Optimizing Sustainable Geothermal Heat Extraction
Patel, Iti; Bielicki, Jeffrey; Buscheck, Thomas
2016-04-01
Geothermal heat, though renewable, can be depleted over time if the rate of heat extraction exceeds the natural rate of renewal. As such, the sustainability of a geothermal resource is typically viewed as preserving the energy of the reservoir by weighing heat extraction against renewability. But heat that is extracted from a geothermal reservoir is used to provide a service to society and an economic gain to the provider of that service. For heat extraction used for market commodities, sustainability entails balancing the rate at which the reservoir temperature renews with the rate at which heat is extracted and converted into economic profit. We present a model for managing geothermal resources that combines simulations of geothermal reservoir performance with natural resource economics in order to develop optimal heat mining strategies. Similar optimal control approaches have been developed for managing other renewable resources, like fisheries and forests. We used the Non-isothermal Unsaturated-saturated Flow and Transport (NUFT) model to simulate the performance of a sedimentary geothermal reservoir under a variety of geologic and operational situations. The results of NUFT are integrated into the optimization model to determine the extraction path over time that maximizes the net present profit given the performance of the geothermal resource. Results suggest that the discount rate that is used to calculate the net present value of economic gain is a major determinant of the optimal extraction path, particularly for shallower and cooler reservoirs, where the regeneration of energy due to the natural geothermal heat flux is a smaller percentage of the amount of energy that is extracted from the reservoir.
Nand Pandey, Sachchida; Vishal, Vikram
2017-04-01
Modeling of coupled thermo-hydro-mechanical processes in enhanced geothermal systems is presented using the finite element method of modeling for a 3-D domain. The reservoir consists of a single horizontal fracture surrounded by low permeable rock matrix. The flow is imposed on a fracture plane, consisting of a doublet system. The reservoir rock mechanical properties were taken from the field data of the Tattapani geothermal field, India. We investigate the effects of injection temperature and mass flow rate on the energy output. The results indicate that temperature and pressure changes within the reservoirs occur due to injection of cold water. The temperature drop and fluid overpressure inside the reservoirs/fracture affect the transport properties of the fracture. The spatial-temporal variations of fracture aperture inside the reservoir greatly impact the thermal drawdown and therefore net energy output. The results showed that maximum aperture evolution occurs near the injection zone than the production zone. The fracture aperture evolution is a result of combined effects of thermal stress and fluid overpressure inside the fracture. The fracture opening reduces the injection pressure required to circulate the fixed volume of water. The effects of the injection temperature on heat extraction were also analyzed under different reservoir formations. The results indicate that reservoir permeability plays a significant role on heat extraction, highlighting the important effect of water losses. For each factor, it is concluded that thermal breakthrough primarily depends on injection temperate, mass flow rate, reservoir permeability and well distances. The results of this study can help in choosing the operational parameters for successful operation of geothermal system. The study will also be helpful to optimize the EGS performance under varying reservoir conditions.
Optimal Management of Geothermal Heat Extraction
Patel, I. H.; Bielicki, J. M.; Buscheck, T. A.
2015-12-01
Geothermal energy technologies use the constant heat flux from the subsurface in order to produce heat or electricity for societal use. As such, a geothermal energy system is not inherently variable, like systems based on wind and solar resources, and an operator can conceivably control the rate at which heat is extracted and used directly, or converted into a commodity that is used. Although geothermal heat is a renewable resource, this heat can be depleted over time if the rate of heat extraction exceeds the natural rate of renewal (Rybach, 2003). For heat extraction used for commodities that are sold on the market, sustainability entails balancing the rate at which the reservoir renews with the rate at which heat is extracted and converted into profit, on a net present value basis. We present a model that couples natural resource economic approaches for managing renewable resources with simulations of geothermal reservoir performance in order to develop an optimal heat mining strategy that balances economic gain with the performance and renewability of the reservoir. Similar optimal control approaches have been extensively studied for renewable natural resource management of fisheries and forests (Bonfil, 2005; Gordon, 1954; Weitzman, 2003). Those models determine an optimal path of extraction of fish or timber, by balancing the regeneration of stocks of fish or timber that are not harvested with the profit from the sale of the fish or timber that is harvested. Our model balances the regeneration of reservoir temperature with the net proceeds from extracting heat and converting it to electricity that is sold to consumers. We used the Non-isothermal Unconfined-confined Flow and Transport (NUFT) model (Hao, Sun, & Nitao, 2011) to simulate the performance of a sedimentary geothermal reservoir under a variety of geologic and operational situations. The results of NUFT are incorporated into the natural resource economics model to determine production strategies that
Shikov, Vasil; Kammerer, Dietmar R; Mihalev, Kiril; Mollov, Plamen; Carle, Reinhold
2008-09-24
Thermal degradation and color changes of purified strawberry anthocyanins in model solutions were studied upon heating at 85 degrees C by HPLC-DAD analyses and CIELCh measurements, respectively. The anthocyanin half-life values increased significantly due to the addition of rose (Rosa damascena Mill.) petal extracts enriched in natural copigments. Correspondingly, the color stability increased as the total color difference values were smaller for anthocyanins upon copigment addition, especially after extended heating. Furthermore, the stabilizing effect of rose petal polyphenols was compared with that of well-known copigments such as isolated kaempferol, quercetin, and sinapic acid. The purified rose petal extract was found to be a most effective anthocyanin-stabilizing agent at a molar pigment/copigment ratio of 1:2. The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved color retention without affecting the gustatory quality of the product.
Directory of Open Access Journals (Sweden)
Zhixue Sun
2018-01-01
Full Text Available The Enhanced Geothermal System (EGS constructs an artificial thermal reservoir by hydraulic fracturing to extract heat economically from hot dry rock. As the core element of the EGS heat recovery process, mass and heat transfer of working fluid mainly occurs in fractures. Since the direction of the natural and induced fractures are generally perpendicular to the minimum principal stress in the formation, as an effective stimulation approach, horizontal well production could increase the contact area with the thermal reservoir significantly. In this paper, the thermal reservoir is developed by a dual horizontal well system and treated as a fractured porous medium composed of matrix rock and discrete fracture network. Using the local thermal non-equilibrium theory, a coupled THM mathematical model and an ideal 3D numerical model are established for the EGS heat extraction process. EGS heat extraction capacity is evaluated in the light of thermal recovery lifespan, average outlet temperature, heat production, electricity generation, energy efficiency and thermal recovery rate. The results show that with certain reservoir and production parameters, the heat production, electricity generation and thermal recovery lifespan can achieve the commercial goal of the dual horizontal well system, but the energy efficiency and overall thermal recovery rate are still at low levels. At last, this paper puts forward a series of optimizations to improve the heat extraction capacity, including production conditions and thermal reservoir construction design.
Nand Pandey, Sachchida; Chaudhuri, Abhijit; Kelkar, Sharad
2015-04-01
Increasing the carbon dioxide concentration in atmosphere become challenging task for the scientific community. To achieve the sustainable growth with minimum pollution in atmosphere requires the development of low carbon technology or switch towards renewable energy. Geothermal energy is one of the promising source of clean energy. Geothermal energy is also considered a sustainable, reliable and least-expensive. This study presents a numerical modeling of subsurface heat extraction from the reservoir. The combine flow, heat transfer and geo-mechanical problem are modeled using FEHM code, which was validated against existing field data, numerical code and commercial software. In FEHM the flow and heat transfer in reservoir are solved by control volume method while for mechanical deformation finite element technique is used. The 3-D computational domain (230m × 200m × 1000m) has single horizontal fault/fracture, which is located at 800 m depth from the ground surface. The fracture connects the injection and production wells. The distance between the wells is 100 m. A geothermal gradient 0.08 °C/m is considered. The temperatures at top and bottom boundaries are held fixed as 20 and 100 °C respectively. The zero heat and mass flux boundary conditions are imposed to all vertical side boundaries of the domain. The simulation results for 100 days suggests that the computational domain is sufficiently large as the temperature along the vertical boundaries are not affected by cold-water injection. To model the thermo-poro-elastic deformation, zero all three components of displacement are specified as zero at the bottom. The zero stress condition along all other boundaries allows the boundaries to move freely. The temperature and pressure dependent fluid properties such as density and viscosity with single phase flow in saturated medium is considered. We performed a series of thermo-hydro-mechanical (THM) simulations to show aperture alteration due to cold
Energy Technology Data Exchange (ETDEWEB)
Augustine, Chad
2017-05-01
Existing methodologies for estimating the electricity generation potential of Enhanced Geothermal Systems (EGS) assume thermal recovery factors of 5% or less, resulting in relatively low volumetric electricity generation potentials for EGS reservoirs. This study proposes and develops a methodology for calculating EGS electricity generation potential based on the Gringarten conceptual model and analytical solution for heat extraction from fractured rock. The electricity generation potential of a cubic kilometer of rock as a function of temperature is calculated assuming limits on the allowed produced water temperature decline and reservoir lifetime based on surface power plant constraints. The resulting estimates of EGS electricity generation potential can be one to nearly two-orders of magnitude larger than those from existing methodologies. The flow per unit fracture surface area from the Gringarten solution is found to be a key term in describing the conceptual reservoir behavior. The methodology can be applied to aid in the design of EGS reservoirs by giving minimum reservoir volume, fracture spacing, number of fractures, and flow requirements for a target reservoir power output. Limitations of the idealized model compared to actual reservoir performance and the implications on reservoir design are discussed.
Directory of Open Access Journals (Sweden)
Guang Chen
2016-07-01
Full Text Available The Weather Research and Forecasting (WRF model coupled with an Urban Canopy Model (UCM was used for studying urban environmental issues. Because land use data employed in the WRF model do not agree with the current situation around Guangzhou, China, the performance of WRF/UCM with new land-use data extracted from Remote Sensing (RS data was evaluated in early August 2012. Results from simulations reveal that experiments with the extracted data are capable of reasonable reproductions of the majority of the observed temporal characteristics of the 2-m temperature, and can capture the characteristics of Urban Heat Island (UHI. The “UCM_12” simulation, which employed the extracted land-use data with the WRF/UCM model, provided the best reproduction of the 2-m temperature data evolution and the smallest minimum absolute average error when compared with the other two experiments without coupled UCM. The contributions of various factors to the UHI effect were analyzed by comparing the energy equilibrium processes of “UCM_12” in urban and suburban areas. Analysis revealed that energy equilibrium processes with new land use data can explain the diurnal character of the UHI intensity variation. Furthermore, land use data extracted from RS can be used to simulate the UHI.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Matson, Dennis L.; Johnson, T. V.; Lunine, J. I.; Castillo-Rogez, J. C.
2010-10-01
Plume gas composition and the presence of dust grains rich in sodium salts [1,2] support a subsurface liquid as the source of the plumes observed at the South pole of Enceladus. We suggest that seawater circulating from the ocean to the surface supplies water, gas, dust and heat to the plumes. Our model needs only a percent or two of gas dissolved in the ocean, a value that is very much consistent with available observations ([1] suggest 10 percent of various gas species in the plume). As seawater comes up, pressure is released and bubbles form. Bubbly seawater is less dense than ice. Expanding gas provides lifting energy (cf. [6], [7]). The model delivers the materials that Postberg et al. [2] use for plume eruptions. Popping bubbles throw a fine spray that contains salt. This aerosol exits with the plume gas [2]. Most significant is the south polar heat flow >15 GW [4]. Water-borne oceanic heat is transferred to the surface ice. Less this heat, the water becomes colder, dissolves the bubble gases and becomes dense. It returns to the ocean via cracks in the ice. A large volume of ice is accessible via cracks SO THAT chemical interactions, heat exchange and other processes are possible. [1] Waite Jr et al., Nature, 460, 487 (2009). [2] Postberg et al., Nature, 459, 1098 (2009). [4] Howett et al BAAS., 41, 1122 (2009). [6] Crawford, and Stevenson, Icarus, 73, 66 (1988). [7] Murchie, and Head, LPS XVII, 583 (1986). This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under NASA contract, and for JIL under "Incentivazione alla mobilita' di studiosi straineri e italiani residenti all'estero" of Italy.
Thermoporoelastic effects during heat extraction from low-permeability reservoirs
DEFF Research Database (Denmark)
Salimzadeh, Saeed; Nick, Hamidreza M.; Zimmerman, R. W.
2018-01-01
Thermoporoelastic effects during heat extraction from low permeability geothermal reservoirs are investigated numerically, based on the model of a horizontal penny-shaped fracture intersected by an injection well and a production well. A coupled formulation for thermo-hydraulic (TH) processes...... is presented that implicitly accounts for the mechanical deformation of the poroelastic matrix. The TH model is coupled to a separate mechanical contact model (M) that solves for the fracture contact stresses due to thermoporoelastic compression. Fractures are modelled as surface discontinuities within a three......-dimensional matrix. A robust contact model is utilised to resolve the contact tractions between opposing fracture surfaces. Results show that due to the very low thermal diffusivity of the rock matrix, the thermally-induced pore pressure partially dissipates even in the very low-permeability rocks that are found...
Characteristics of model heat exchanger
Kolínský, Jan
2017-09-01
The aim of this paper is thermal analysis of model water to water heat exchanger at different mass flow rates. Experimental study deals with determination of total heat transfer - power of the heat exchanger. Furthermore the paper deals with analysis of heat exchanger charakcteristic using a definition of thermal efficiency. It is demonstrated that it is advisable to monitor the dependence of thermal efficiency and flow ratio.
The experimental study of heat extraction of supercritical CO2 in the geothermal reservoir
Directory of Open Access Journals (Sweden)
Huang Cyun-Jie
2016-01-01
Full Text Available The heat transfer phenomena of supercritical CO2 are experimentally investigated in a horizontal tube for improving the efficiency of CO2-EGS.This study discuss the experimental verification of the numerical simulations. The experiment is conducted for the pressure, the flow rate, and particle size 1.54mm. In addition, the experiment and simulation that the maximum heat extraction is occurred at the 9MPa pressure and mass flow rate of 0.00109 kg/s. The maximum specific heat extraction at 9MPa and flow rate of 0.00082 kg/s. The results show that the numerical model has been experimentally verified of the feasibility. Furthermore, the pseudo-critical point had a significant influence on the heat extraction, temperature difference and specific heat extraction.
Assessing the feasibility of high-density subsurface heat extraction in urban areas
Abesser, Corinna; Busby, Jonathan
2017-04-01
The subsurface is increasingly utilized as a heat source (sink) for use in heating (and cooling) applications. This is driven by the need to increase the amount of heat generated from renewable sources to meet the EU renewable energy target of 12% by 2020. This study explores the feasibility, performance and long-term sustainability of high density, closed-loop GSHP installations in urban areas. Specifically, it employs a 2D, finite element, heat transport model to assess the impact of high density heat extraction in a residential area in Reading. A block of semi-detached houses is modelled, assuming that separate GSHP systems are installed in every property. The model considers conductive and advective heat transport. Uncertainties are explored through varying thermal properties and groundwater gradients across the site. Different heat demand scenarios are evaluated and the impact on the subsurface temperature distribution and on heat pump efficiency is assessed. The scenarios are selected to represent variations in inter-annual weather pattern, heating pattern and building insulation standards. Results indicate that high density heat extraction for domestic heating can be sustainable over the lifespan expected for GSHP systems (of around 20 years), in particular where heat demand is reduced by home improvement measures. Based on the results, recommendations are being presented for the sustainable deployment of high density GSHP installation in urban areas.
Mathematical model of heat pump
Pitron, J.
2015-01-01
In this paper different energy states of a heat pump are described. Equations used for mathematical description of the heat pump in the Matlab Simulink are presented. Created model is used to calculate the energy flows in the system according to different input parameters. The simulation involves an accumulation tank, which is controlled by individual input and output parameters. Simulation results have been compared with the experimental measured values on a heat pump in a laboratory.
Transient thermohydraulic heat pipe modeling
Hall, Michael L.; Doster, Joseph M.
Many space based reactor designs employ heat pipes as a means of conveying heat. In these designs, thermal radiation is the principle means for rejecting waste heat from the reactor system, making it desirable to operate at high temperatures. Lithium is generally the working fluid of choice as it undergoes a liquid-vapor transformation at the preferred operating temperature. The nature of remote startup, restart, and reaction to threats necessitates an accurate, detailed transient model of the heat pipe operation. A model is outlined of the vapor core region of the heat pipe which is part of a large model of the entire heat pipe thermal response. The vapor core is modeled using the area averaged Navier-Stokes equations in one dimension, which take into account the effects of mass, energy and momentum transfer. The core model is single phase (gaseous), but contains two components: lithium gas and a noncondensible vapor. The vapor core model consists of the continuity equations for the mixture and noncondensible, as well as mixture equations for internal energy and momentum.
Energy Technology Data Exchange (ETDEWEB)
El-Sebaii, A.A. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt)]. E-mail: aasebaii@yahoo.com; Aboul-Enein, S. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt); Ramadan, M.R.I. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt); Khallaf, A.M. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt)
2006-05-15
The thermal performance of a shallow solar pond (SSP) under an open cycle continuous flow heating mode for heat extraction has been investigated. A serpentine heat exchanger (HE), either welded to the absorber plate or immersed in the pond water, has been used for extracting the heat. Suitable computer programs have been developed based on analytical solutions of the energy balance equations for the various elements of the SSP in the presence of the HE. Numerical calculations have been performed to study the effect of different operational and configurational parameters on the pond performance. In order to improve the pond performance, optimization of the various dimensions of the pond with the HE has been performed. The effects of the design parameters of the HE's tube, i.e. length L{sub he}, diameter D and mass flow rate m-bar {sub f} of the fluid flowing through the HE, on the pond performance have been investigated. The outlet temperature of the HE's fluid T{sub fo} is found to increase with increase of the HE length L{sub he}, and it decreases with increase of the mass flow rate of the HE's fluid m-bar {sub f} up to typical values for these parameters. Typical values for L{sub he} and m-bar {sub f} are found to be 4m and 0.004kg/s beyond which the change in T{sub fo} becomes insignificant. Experiments have been performed for the pond under different operational conditions with a HE welded to the absorber plate. To validate the proposed mathematical models, comparisons between experimental and theoretical results have been performed. Good agreement has been achieved.
An analytical dynamic model of heat transfer from the heating body to the heated room
Directory of Open Access Journals (Sweden)
Mižáková Jana
2017-01-01
Full Text Available On the base of mathematical description of thermal balance the dynamic model of the hot-water heating body (radiator was designed. The radiator is mathematically described as a heat transfer system between heating water and warmed-up air layer. Similarly, the dynamic model of heat transfer through the wall from the heated space to the outdoor environment was design. Both models were interconnected into dynamic model of heat transfer from the heating body to the heated room and they will be implemented into simulation model of the heating system in Matlab/Simulink environment.
Hybrid Model of Content Extraction
DEFF Research Database (Denmark)
Qureshi, Pir Abdul Rasool; Memon, Nasrullah
2012-01-01
We present a hybrid model for content extraction from HTML documents. The model operates on Document Object Model (DOM) tree of the corresponding HTML document. It evaluates each tree node and associated statistical features like link density and text distribution across the node to predict...... model outperformed other existing content extraction models. We present a browser based implementation of the proposed model as proof of concept and compare the implementation strategy with various state of art implementations. We also discuss various applications of the proposed model with special...
Directory of Open Access Journals (Sweden)
Bisheng Wu
2017-01-01
Full Text Available Approximate solutions are found for a mathematical model developed to predict the heat extraction from a closed-loop geothermal system which consists of two vertical wells (one for injection and the other for production and one horizontal well which connects the two vertical wells. Based on the feature of slow heat conduction in rock formation, the fluid flow in the well is divided into three stages, that is, in the injection, horizontal, and production wells. The output temperature of each stage is regarded as the input of the next stage. The results from the present model are compared with those obtained from numerical simulator TOUGH2 and show first-order agreement with a temperature difference less than 4°C for the case where the fluid circulated for 2.74 years. In the end, a parametric study shows that (1 the injection rate plays dominant role in affecting the output performance, (2 higher injection temperature produces larger output temperature but decreases the total heat extracted given a specific time, (3 the output performance of geothermal reservoir is insensitive to fluid viscosity, and (4 there exists a critical point that indicates if the fluid releases heat into or absorbs heat from the surrounding formation.
Microwave heating: A potential pretreating method for bamboo fiber extraction
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Fu Jia-Jia
2017-01-01
Full Text Available Microwave heating is proposed as a kind of pretreating methods for bamboo fiber extraction. Effect of various processing parameters, e. g. microwave initial-setting power, reaction temperature, irradiation time, and bath ratio (bamboo to water on bamboo powders was studied. Analysis of chemical components indicates that microwave assisted extraction is a mild treating method without obvious change of main constitutes of bamboo. The removal of polysaccharide by microwave treating resulted in loosening the structure and thus benefits hydrolysis of bamboo in subsequent.
Statistical Model for Content Extraction
DEFF Research Database (Denmark)
Qureshi, Pir Abdul Rasool; Memon, Nasrullah
2011-01-01
We present a statistical model for content extraction from HTML documents. The model operates on Document Object Model (DOM) tree of the corresponding HTML document. It evaluates each tree node and associated statistical features to predict significance of the node towards overall content...
Monazami, Reza; Saadat, Mehdi; Zhu, Jianzhong; Haj-Hariri, Hossein
2015-11-01
The problem of evaporation from a vertical micro-grooved blade heated from above is investigated. The required superheat to handle the incoming flux is calculated using the results of the study by Monazami and Haj-Hariri (2012). The relation between the applied heat flux, dry-out length and the maximum equilibrium temperature for several geometries and working fluids are studied. Furthermore, a computational study of the evaporating meniscus is conducted to evaluate the evaporation rates and dissipated heat flux at the liquid-vapor interface. The computational study accounts for the flow and heat transfer in both liquid and vapor phases. The results of this study indicate that the micro-grooved structure can dissipate heat fluxes as high as 10MW/m2 for superheats as low as 5 degrees Kelvin. Experiments are conducted to verify the computational and analytical results. The findings of this work are applicable to the design of thermal management systems for high heat flux applications. Partially supported by the MAXNET Energy Partnership (Max Planck Institute and UVA).
Extraction of glabridin with heat reflux extraction by response surface analysis
Directory of Open Access Journals (Sweden)
Li-ying DING
2013-12-01
Full Text Available Objective: To study the extraction process of glabridin from Glycyrrhiza glabra. Methods: The solid-liquid ratio, extraction time and extraction temperature are the three main factors in the experiment, and the extract solvent is ethyl acetate. Establish the response surface quadratic regression equation of glabridin extraction rate and purity. Results:The results indicate that the optimum conditions for glabridin are as follows: solvent is ethyl acetate, extraction time is 90 min, the ratio of solvent to solid is 35 ∶1 (ml/g, and extraction temperature is 44.7 ℃, purity and the maximum yield of Extraction of glabridin are 6.96% and 0.241%, The validation test shows that the experimental values of the model are 0.235% and 6.05% . Conclusion: The model equation can predict the experimental results, it can be used as reference in industrial production.
A Heat Dynamic Model for Intelligent Heating of Buildings
DEFF Research Database (Denmark)
Thavlov, Anders; Bindner, Henrik W.
2015-01-01
of the building in time. This way the thermal mass of the building can be used to absorb energy from renewable energy source when available and postpone heating in periods with lack of renewable energy generation. The model is used in a model predictive controller to ensure the residential comfort over a given......This article presents a heat dynamic model for prediction of the indoor temperature in an office building. The model has been used in several flexible load applications, where the indoor temperature is allowed to vary around a given reference to provide power system services by shifting the heating...
Comparison of Frictional Heating Models
Energy Technology Data Exchange (ETDEWEB)
Davies, Nicholas R [ORNL; Blau, Peter Julian [ORNL
2013-10-01
The purpose of this work was to compare the predicted temperature rises using four well-known models for frictional heating under a few selected conditions in which similar variable inputs are provided to each model. Classic papers by Archard, Kuhlmann-Wilsdorf, Lim and Ashby, and Rabinowicz have been examined, and a spreadsheet (Excel ) was developed to facilitate the calculations. This report may be used in conjunction with that spreadsheet. It explains the background, assumptions, and rationale used for the calculations. Calculated flash temperatures for selected material combinations, under a range of applied loads and sliding speeds, are tabulated. The materials include AISI 52100 bearing steel, CDA 932 bronze, NBD 200 silicon nitride, Ti-6Al-4V alloy, and carbon-graphite material. Due to the assumptions made by the different models, and the direct way in which certain assumed quantities, like heat sink distances or asperity dimensions, enter into the calculations, frictional hearing results may differ significantly; however, they can be similar in certain cases in light of certain assumptions that are shared between the models.
Mathematical model of induction heating
Rak, Josef
2017-07-01
One of mathematical models of induction heating can be described by a parabolic differential equation with the specific Joule looses in the body. Advantage of this method is that the detailed knowledge of the 3D-magnetic field is not necessary and move of the body or the inductor can be easily implemented. The specific Joule looses can computed by solving the Fredholm integral equation of the second kind for the eddy current of density by the Nyström method with the singularity subtraction.
Modelling `Life' against `heat death'
Zak, Michail
2018-01-01
This work is inspired by the discovery of a new class of dynamical system described by ordinary differential equations coupled with their Liouville equation. These systems called self-controlled since the role of actuators is played by the probability produced by the Liouville equation. Following the Madelung equation that belongs to this class, non-Newtonian properties such as randomness, entanglement and probability interference typical for quantum systems have been described. Special attention was paid to the capability to violate the second law of thermodynamics, which makes these systems neither Newtonian, nor quantum. It has been shown that self-controlled dynamical systems can be linked to mathematical models of living systems. The discovery of isolated dynamical systems that can decrease entropy in violation of the second law of thermodynamics, and resemblances of these systems to livings suggests that `Life' can slow down the `heat death' of the Universe and that can be associated with the Purpose of Life.
Hajian, Saeed Reza; Pouladian, Majid; Hemmasi, Gholam Reza
2016-01-01
In high intensity focused ultrasound (HIFU) systems using non-ionizing methods in cancer treatment, if the device is applied to the body externally, the HIFU beam can damage nearby healthy tissues and burn skin due to lack of knowledge about the viscoelastic properties of patient tissue and failure to consider the physical properties of tissue in treatment planning. Addressing this problem by using various methods, such as MRI or ultrasound, elastography can effectively measure visco-elastic properties of tissue and fits within the pattern of stimulation and total treatment planning. In this paper, in a linear path of HIFU propagation, and by considering the smallest part of the path, including voxel with three mechanical elements of mass, spring and damper, which represents the properties of viscoelasticity of tissue, by creating waves of HIFU in the wire environment of MATLAB mechanics and stimulating these elements, pressure and heat transfer due to stimulation in the hypothetical voxel was obtained. Throu...
Modelling Heat Transfer of Carbon Nanotubes
Yang, Xin-She
2010-01-01
Modelling heat transfer of carbon nanotubes is important for the thermal management of nanotube-based composites and nanoelectronic device. By using a finite element method for three-dimensional anisotropic heat transfer, we have simulated the heat conduction and temperature variations of a single nanotube, a nanotube array and a part of nanotube-based composite surface with heat generation. The thermal conductivity used is obtained from the upscaled value from the molecular simulations or ex...
Modelling and simulation of a heat exchanger
Xia, Lei; Deabreu-Garcia, J. Alex; Hartley, Tom T.
1991-01-01
Two models for two different control systems are developed for a parallel heat exchanger. First by spatially lumping a heat exchanger model, a good approximate model which has a high system order is produced. Model reduction techniques are applied to these to obtain low order models that are suitable for dynamic analysis and control design. The simulation method is discussed to ensure a valid simulation result.
MATHEMATICAL MODELING OF HEATING RATE PRODUCT AT HIGH HEAT TREATMENT
Directory of Open Access Journals (Sweden)
M. M. Akhmedova
2014-01-01
Full Text Available Methods of computing and mathematical modeling are all widely used in the study of various heat exchange processes that provide the ability to study the dynamics of the processes, as well as to conduct a reasonable search for the optimal technological parameters of heat treatment.This work is devoted to the identification of correlations among the factors that have the greatest effect on the rate of heating of the product at hightemperature heat sterilization in a stream of hot air, which are chosen as the temperature difference (between the most and least warming up points and speed cans during heat sterilization.As a result of the experimental data warming of the central and peripheral layers compote of apples in a 3 liter pot at high-temperature heat treatment in a stream of hot air obtained by the regression equation in the form of a seconddegree polynomial, taking into account the effects of pair interaction of these parameters.
Dynamic Heat Transfer Model of Refrigerated Foodstuff
DEFF Research Database (Denmark)
Cai, Junping; Risum, Jørgen; Thybo, Claus
2006-01-01
their temperature relation. This paper discusses the dynamic heat transfer model of foodstuff inside the display cabinet, one-dimensional dynamic model is developed, and the Explicit Finite Difference Method is applied, to handle the unsteady heat transfer problem with phase change, as well as time varying boundary...
New models for droplet heating and evaporation
Sazhin, Sergei S.
2013-02-01
A brief summary of new models for droplet heating and evaporation, developed mainly at the Sir Harry Ricardo Laboratory of the University of Brighton during 2011-2012, is presented. These are hydrodynamic models for mono-component droplet heating and evaporation, taking into account the effects of the moving boundary due to evaporation, hydrodynamic models of multi-component droplet heating and evaporation, taking and not taking into account the effects of the moving boundary, new kinetic models of mono-component droplet heating and evaporation, and a model for mono-component droplet evaporation, based on molecular dynamics simulation. The results, predicted by the new models are compared with experimental data and the prehctions of the previously developed models where possible. © 2013 Asian Network for Scientific Information.
Modelling of Ammonia Heat Pump Desuperheaters
DEFF Research Database (Denmark)
Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix
2015-01-01
This paper presents a study of modelling desuperheating in ammonia heat pumps. Focus is on the temperature profile of the superheated refrigerant. Typically, the surface area of a heat exchanger is estimated using the Log Mean Temperature Difference (LMTD) method. The assumption of this method...
Zutphen, M. van; Heron, G.; Enfield, C.G.; Christensen, T.H.
1998-01-01
A 2D-laboratory box experiment (12 x 56 x 116 cm) was conducted to simulate the enhancement of soil vapor extraction by the application of low frequency electrical heating Uoule heating) for the remediation of a low permeable, silty soil contaminated with trichloroethylene. Joule heating enlarged
Lavoué, Francois; Tourancheau, Bernard
2010-01-01
International audience; In the context of energy crisis and global warming, heating buildings with the solar energy stored in the soil rep- resents a very interesting alternative. Moreover, cooling buildings can also use the soil damping capacity. This paper presents our reflexion about the modeling and dimensioning of the ground heat exchanger part of ground-coupled heat pumps (GCHP). After a physical overview of the ground heat exchanger, we extract from analytical solutions practical conse...
Comprehensive areal model of residential heating demands
Energy Technology Data Exchange (ETDEWEB)
Tessmer, R.G. Jr.
1978-01-01
Data sources and methodology for modeling annual residential heating demands are described. A small areal basis is chosen, census tract or minor civil division, to permit estimation of demand densities and economic evaluation of community district heating systems. The demand model is specified for the entire nation in order to provide general applicability and to permit validation with other published fuel consumption estimates for 1970.
Ohmic heating as a pre-treatment in solvent extraction of rice bran.
Nair, Gopu Raveendran; Divya, V R; Prasannan, Liji; Habeeba, V; Prince, M V; Raghavan, G S V
2014-10-01
Rice bran, which is one of the major by products of paddy contain high quality proteins and edible oil apart from fibre, ash and NFE (nitrogen free extract). The existing solvent extraction method employs n-hexane as the most viable solvent for the extraction of oil from rice bran. But the high cost and scarce availability of n-hexane resulted in uneconomical extraction of rice bran oil. In this study, rice bran was ohmically heated for different time periods(1, 2 and 3 min) with different current values (5, 15 and 20 A) and with different concentration of sodium chloride (1 M, 0.1 M and 0.01 M) as conducting medium. The ohmically heated rice bran was subjected to extraction studies. Ohmic heating of rice bran of paddy varieties Red Triveni and Basmati reduced the extraction time by nearly 75 % and 70 % respectively and gave a maximum quantity of oil extracted when compared to bran, which was not ohmically heated. From the experiments with varying concentrations, residence time of ohmic heating and currents, it was found that ohmically heating the rice bran with 1 M sodium chloride solution and with a current value of 20 A for 3 min gave maximum oil extraction with minimum extraction time.
Modeling microscale heat transfer using Calore.
Energy Technology Data Exchange (ETDEWEB)
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Demand modelling for central heating systems
Energy Technology Data Exchange (ETDEWEB)
Heller, A.
2000-07-01
Most researchers in the field of heat demand estimation have focussed on explaning the load for a given plant based on rather few measurements. This approach is simply the only one adaptable with the very limited data material and limited computer power. This way of dealing with the subject is here called the top-down approach, due to the fact that one tries to explain the load from the overall data. The results of such efforts are discussed in the report, leading to inspiration for own work. Also the significance of the findings to the causes for given heat loads are discussed and summarised. Contrary to the top-down approach applied in literature, a here-called bottom-up approach is applied in this work, describing the causes of a given partial load in detail and combining them to explain the total load for the system. Three partial load 'components' are discussed: 1) Space heating. 2) Hot-Water Consumption. 3) Heat losses in pipe networks. The report is aimed at giving an introduction to these subjects, but at the same time at collecting the previous work done by the author. Space heating is shortly discussed and loads are generated by an advanced simulation model. A hot water consumption model is presented and heat loads, generated by this model, utilised in the overall work. Heat loads due to heat losses in district heating a given a high priority in the current work. Hence a detailed presentation and overview of the subject is given to solar heating experts normally not dealing with district heating. Based on the 'partial' loads generated by the above-mentioned method, an overall load model is built in the computer simulation environment TRNSYS. The final tool is then employed for the generation of time series for heat demand, representing a district heating area. The results are compared to alternative methods for the generation of heat demand profiles. Results form this comparison will be presented. Computerised modelling of systems
Modelling batch microwave heating of water
Yeong, S. P.; Law, M. C.; Lee, C. C. Vincent; Chan, Y. S.
2017-07-01
A numerical model of the microwave heating of distilled water is developed using COMSOL Multiphysics software to investigate the microwave effects on the heating rate. Three frequencies (0.915GHz, 2GHz and 2.45 GHz) have been applied in the model in order to study their influences on the water temperature. It is found that the water heats up at 2GHz and 2.45GHz, however, there is no sign of heating at 915MHz. This is supported with the figures of the electric field distribution in the microwave cavity. The results shown in the developed model is validated with the experimental results obtained at 2.45 GHz.
Computational model of miniature pulsating heat pipes
Energy Technology Data Exchange (ETDEWEB)
Martinez, Mario J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Givler, Richard C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2013-01-01
The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.
Modeling Classical Heat Conduction in FLAG
Energy Technology Data Exchange (ETDEWEB)
Ramsey, Scott D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hendon, Raymond Cori [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-01-12
The Los Alamos National Laboratory FLAG code contains both electron and ion heat conduction modules; these have been constructed to be directly relevant to user application problems. However, formal code verification of these modules requires quantitative comparison to exact solutions of the underlying mathematical models. A wide variety of exact solutions to the classical heat conduction equation are available for this purpose. This report summarizes efforts involving the representation of the classical heat conduction equation as following from the large electron-ion coupling limit of the electron and ion 3T temperature equations, subject to electron and ion conduction processes. In FLAG, this limiting behavior is quantitatively verified using a simple exact solution of the classical heat conduction equation. For this test problem, both heat conduction modules produce nearly identical spatial electron and ion temperature profiles that converge at slightly less than 2nd order to the corresponding exact solution.
Model for the spontaneous heating of coal
Energy Technology Data Exchange (ETDEWEB)
Schmal, D.; Duyzer, J.H.; Heuven, J.W. van
1985-07-01
As part of an investigation into the spontaneous heating of coal piles, a one-dimensional model has been developed to describe the spontaneous heating process at relatively low temperatures (less than about 100 C). The ultimate unsteady-state model takes into account depletion of oxygen and production of heat by chemisorption of oxygen in the coal, transport of oxygen by diffusion and convection and transport of heat by conduction, convection and evaporation/condensation of coal moisture. It consists of four differential equations, for conservation of oxygen mass, of coal moisture and of heat and rate of reaction of oxygen with coal. Calculations using data from laboratory and field experiments give results that describe the process of spontaneous heating semiquantitatively. The most important parameters in the process of spontaneous heating, particularly for the time between stacking and spontaneous ignition, are the porosity of the pile (degree of compaction), the initial temperature of the coal and the evaporation and condensation of coal moisture. The influence of other parameters (e.g. reactivity of the coal, thermal conductivity) is much less pronounced. 12 references.
VISCOELASTIC MODELS OF TIDALLY HEATED EXOMOONS
Energy Technology Data Exchange (ETDEWEB)
Dobos, Vera [Konkoly Thege Miklos Astronomical Institute, Research Centre of Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Konkoly Thege Miklós út 15-17, Budapest (Hungary); Turner, Edwin L., E-mail: dobos@konkoly.hu [Department of Astrophysical Sciences, Princeton University, 08544, 4 Ivy Lane, Peyton Hall, Princeton, NJ (United States)
2015-05-01
Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life has been intensely studied on solar system moons such as Europa or Enceladus where the surface ice layer covers a tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. To study the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than the widely used, so-called fixed Q models because it takes into account the temperature dependence of the tidal heat flux and the melting of the inner material. Using this model, we introduced the circumplanetary Tidal Temperate Zone (TTZ), which strongly depends on the orbital period of the moon and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ using both models. We have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ with orbital periods between 0.1 and 3.5 days than the fixed Q model for plausible distributions of physical and orbital parameters. The viscoelastic model provides more promising results in terms of habitability because the inner melting of the body moderates the surface temperature, acting like a thermostat.
Numerical Modeling of Ablation Heat Transfer
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Seki, Hirakazu; Komori, Tomoaki
1987-01-01
埋設管型熱交換器を用いる方法は, 堆肥そうからの熱抽出において典型的で簡単な方法であるが, 混合素材の切返しを行う際に埋設管の取り外し, 再配管などの煩雑な作業を必要とする。このような煩雑な作業を簡単にするためにマルチ・ヒートパイプ熱交換器を用いたユニークな熱抽出方法を提示し, 熱抽出過程における堆肥そう内温度及び熱交換器出口における熱媒体の温度の解析解を導いた。これらの解は埋設管型熱交換器に対する解と数学的に同一であった。そして, 解析解に基づき, マルチ・ヒートパイプ熱交換器の熱抽出能力を計算した。A buried-tube-type heat exchanger is typical and simple for extracting heat from a compost bed except the requirement of some tedious works such as removing and retubing the tubes in remixing the compost materials. In order to simplify the abo...
Modeling terahertz heating effects on water
DEFF Research Database (Denmark)
Kristensen, Torben T.L.; Withayachumnankul, Withawat; Jepsen, Peter Uhd
2010-01-01
We apply Kirchhoff’s heat equation to model the influence of a CW terahertz beam on a sample of water, which is assumed to be static. We develop a generalized model, which easily can be applied to other liquids and solids by changing the material constants. If the terahertz light source is focused...
Thermophotonic heat pump—a theoretical model and numerical simulations
Oksanen, Jani; Tulkki, Jukka
2010-05-01
We have recently proposed a solid state heat pump based on photon mediated heat transfer between two large-area light emitting diodes coupled by the electromagnetic field and enclosed in a semiconductor structure with a nearly homogeneous refractive index. Ideally the thermophotonic heat pump (THP) allows heat transfer at Carnot efficiency but in reality there are several factors that limit the efficiency. The efficient operation of the THP is based on the following construction factors and operational characteristics: (1) broad area semiconductor diodes to enable operation at optimal carrier density and high efficiency, (2) recycling of the energy of the emitted photons, (3) elimination of photon extraction losses by integrating the emitting and the absorbing diodes within a single semiconductor structure, and (4) eliminating the reverse thermal conduction by a nanometer scale vacuum layer between the diodes. In this paper we develop a theoretical model for the THP and study the fundamental physical limitations and potential of the concept. The results show that even when the most important losses of the THPs are accounted for, the THP has potential to outperform the thermoelectric coolers especially for heat transfer across large temperature differences and possibly even to compete with conventional small scale compressor based heat pumps.
Heat Pump Clothes Dryer Model Development
Energy Technology Data Exchange (ETDEWEB)
Shen, Bo [ORNL
2016-01-01
A heat pump clothes dryer (HPCD) is an innovative appliance that uses a vapor compression system to dry clothes. Air circulates in a closed loop through the drum, so no vent is required. The condenser heats air to evaporate moisture out of the clothes, and the evaporator condenses water out of the air stream. As a result, the HPCD can achieve 50% energy savings compared to a conventional electric resistance dryer. We developed a physics-based, quasi-steady-state HPCD system model with detailed heat exchanger and compressor models. In a novel approach, we applied a heat and mass transfer effectiveness model to simulate the drying process of the clothes load in the drum. The system model is able to simulate the inherently transient HPCD drying process, to size components, and to reveal trends in key variables (e.g. compressor discharge temperature, power consumption, required drying time, etc.) The system model was calibrated using experimental data on a prototype HPCD. In the paper, the modeling method is introduced, and the model predictions are compared with experimental data measured on a prototype HPCD.
National Aeronautics and Space Administration — ATA Engineering, Inc. (ATA) proposes a small business innovation research (SBIR) program for a novel compressor heat-extraction development program in response to...
Dynamic thermal modelling of horizontal ground-source heat pumps
Guohui Gan
2013-01-01
A computer program has been developed for numerical simulation of the dynamic thermal performance of horizontally coupled heat exchangers for ground-source heat pumps, taking account of dynamic variations of climatic, load and soil conditions. The program was used to investigate the effects of operating and start times, installation depth and soil freezing on the heat exchanger performance. It is shown that the rate of heat extraction decreases with increasing operating time. Operating a heat...
Petrothermal heat extraction using a single deviated well (Horstberg, revisited)
Ghergut, Julia; Behrens, Horst; Vogt, Esther; Bartetzko, Anne; Sauter, Martin
2013-04-01
The single-well tracer test conducted (Behrens et al. 2006) in conjunction with waterfrac experiments at Horstberg is re-examined with a view at four basic issues: why single-well? why fracturing? why tracers? does this only work at Horstberg, or can it work almost anywhere else in the Northern-German sedimentary basin? Heat and tracer transport within a composite reservoir (impermeable matrix + waterfrac + permeable layer), as accessed by a single deviated well, turn out to fit into a surprisingly simple description, as the plain (arithmetic) sum of certain petrothermal-type and aquifer-type contributions, whose weighting relative to each other can vary from site to site, depending upon stratigraphy and upon wellbore geometry. At Horstberg, within the particular formations tested ('Volpriehausen', 'Detfurth', 'Solling', comprising mainly claystone and sandstone layers), thermal lifetime results to be petrothermally-dominated, while tracer residence times prove to be 'aquifer'-dominated. Despite this disparity, the reservoir's thermal lifetime can reliably be predicted from tracer test results. What cannot be determined from waterfrac flow-path tracing is the very waterfrac's aperture. Aperture uncertainty, however, does not impede upon thermal lifetime predictability. The results of the semi-analytical approach are confirmed by numerical simulations using a FE model that includes more details of hydrogeological heterogeneity for the Horstberg site. They are complemented by a parameter sensitivity analysis. ACKNOWLEDGEMENT: This study is funded by MWK Niedersachsen (Lower-Saxony's Science and Culture Ministry) and by Baker Hughes (Celle) within task unit G6 of the Collaborative Research Project 'gebo' ('Geothermal Energy and High-Performance Drilling').
Modelling of Thermal Behavior of Borehole Heat Exchangers of Geothermal Heat Pump Heating Systems
Directory of Open Access Journals (Sweden)
Gornov V.F.
2016-01-01
Full Text Available This article reports results of comparing the accuracy of the software package “INSOLAR.GSHP.12”, modeling non-steady thermal behavior of geothermal heat pump heating systems (GHCS and of the similar model “conventional” using finite difference methods for solving spatial non-steady problems of heat conductivity. The software package is based on the method of formulating mathematical models of thermal behavior of ground low-grade heat collection systems developed by INSOLAR group of companies. Equations of mathematical model of spatial non-steady thermal behavior of ground mass of low-grade heat collection system obtained by the developed method have been solved analytically that significantly reduced computing time spent by the software complex “INSOLAR.GSHP.12” for calculations. The method allows to turn aside difficulties associated with information uncertainty of mathematical models of the ground thermal behavior and approximation of external factors affecting the ground. Use of experimentally obtained information about the ground natural thermal behavior in the software package allows to partially take into account the whole complex of factors (such as availability of groundwater, their velocity and thermal behavior, structure and arrangement of ground layers, the Earth’s thermal background, precipitation, phase transformations of moisture in the pore space, and more, significantly influencing the formation of thermal behavior of the ground mass of a low-grade geothermal heat collection system. Numerical experiments presented in the article confirmed the high convergence of the results obtained through the software package “INSOLAR.GSHP.12” with solutions obtained by conventional finite-difference methods.
Guo, Xuyang; Song, Hongqing; Killough, John; Du, Li; Sun, Pengguang
2018-02-01
The utilization of geothermal energy is clean and has great potential worldwide, and it is important to utilize geothermal energy in a sustainable manner. Mathematical modeling studies of geothermal reservoirs are important as they evaluate and quantify the complex multi-physical effects in geothermal reservoirs. However, previous modeling efforts lack the study focusing on the emission reduction efficiency and the deformation at geothermal wellbores caused by geothermal water extraction/circulation. Emission efficiency is rather relevant in geothermal projects introduced in areas characterized by elevated air pollution where the utilization of geothermal energy is as an alternative to burning fossil fuels. Deformation at geothermal wellbores is also relevant as significant deformation caused by water extraction can lead to geothermal wellbore instability and can consequently decrease the effectiveness of the heat extraction process in geothermal wells. In this study, the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir in Daming County, China, are numerically investigated based on a coupled multi-physical model. Relationships between the efficiency of emission reduction and heat extraction, deformation at geothermal well locations, and geothermal field parameters including well spacing, heat production rate, re-injection temperature, rock stiffness, and geothermal well placement patterns are analyzed. Results show that, although large heat production rates and low re-injection temperatures can lead to decreased heat production in the last 8 years of heat extraction, they still improve the overall heat production capacity and emission reduction capacity. Also, the emission reduction capacity is positively correlated with the heat production capacity. Deformation at geothermal wellbore locations is alleviated by smaller well spacing, lower heat production rates, and smaller numbers of injectors in the well pattern, and by
Color and surface chemistry changes of extracted wood flour after heating at 120 °C
Yao Chen; Mandla A. Tshabalala; Jianmin Gao; Nicole M. Stark
2013-01-01
To investigate the effect of heat on color and surface chemistry of wood flour (WF), unextracted, extracted and delignified samples of commercial WF were heated at 120 Â°C for 24 h and analyzed by colorimetry, diffuse reflectance visible (DRV), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Fourier transform Raman (FT-Raman) spectroscopies....
Heat-induced chemical and color changes of extractive-free Black Locust (Rosinia Pseudoacacia) wood
Yao Chen; Jianmin Gao; Yongming Fan; Mandla A. Tshabalala; Nicole M. Stark
2012-01-01
To investigate chemical and color changes of the polymeric constituents of black locust (Robinia pseudoacacia) wood during heat treatment, extractive-free wood flour was conditioned to 30% initial moisture content (MC) and heated for 24 h at 120 Â°C in either an oxygen or nitrogen atmosphere. The color change was measured using the CIELAB color system. Chemical changes...
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2014-01-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic
Customer perspectives on district heating price models
Directory of Open Access Journals (Sweden)
Kerstin Sernhed
2017-01-01
Full Text Available In Sweden there has been a move towards more cost reflective price models for district heating in order to reduce economic risks that comes with variable heat demand and high shares of fixed assets. The keywords in the new price models are higher shares of fixed cost, seasonal energy prices and charging for capacity. Also components that are meant to serve as incentives to affect behaviour are introduced, for example peak load components and flow components. In this study customer responses to these more complex price models have been investigated through focus group interviews and through interviews with companies that have changed their price models. The results show that several important customer requirements are suffering with the new price models. The most important ones are when energy savings do not provide financial savings, when costs are hard to predict and are perceived to be out of control.
Mathematical Modeling of Loop Heat Pipes
Kaya, Tarik; Ku, Jentung; Hoang, Triem T.; Cheung, Mark L.
1998-01-01
The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.
Enzymatic extractability of soybean meal proteins and carbohydrates : heat and humidity effects
Fischer, M.; Kofod, L.V.; Schols, H.A.; Piersma, S.R.; Gruppen, H.; Voragen, A.G.J.
2001-01-01
To study the incomplete enzymatic extractability of proteins and carbohydrates of thermally treated soybean meals, one unheated and three heat-treated soybean meals were produced. To obtain truly enzyme-resistant material, the meals were extracted by a repeated hydrolysis procedure using excessive
Baker, Chad; Vuppuluri, Prem; Shi, Li; Hall, Matthew
2012-06-01
The performance and operating characteristics of a hypothetical thermoelectric generator system designed to extract waste heat from the exhaust of a medium-duty turbocharged diesel engine were modeled. The finite-difference model consisted of two integrated submodels: a heat exchanger model and a thermoelectric device model. The heat exchanger model specified a rectangular cross-sectional geometry with liquid coolant on the cold side, and accounted for the difference between the heat transfer rate from the exhaust and that to the coolant. With the spatial variation of the thermoelectric properties accounted for, the thermoelectric device model calculated the hot-side and cold-side heat flux for the temperature boundary conditions given for the thermoelectric elements, iterating until temperature and heat flux boundary conditions satisfied the convection conditions for both exhaust and coolant, and heat transfer in the thermoelectric device. A downhill simplex method was used to optimize the parameters that affected the electrical power output, including the thermoelectric leg height, thermoelectric n-type to p-type leg area ratio, thermoelectric leg area to void area ratio, load electrical resistance, exhaust duct height, coolant duct height, fin spacing in the exhaust duct, location in the engine exhaust system, and number of flow paths within the constrained package volume. The calculation results showed that the configuration with 32 straight fins was optimal across the 30-cm-wide duct for the case of a single duct with total height of 5.5 cm. In addition, three counterflow parallel ducts or flow paths were found to be an optimum number for the given size constraint of 5.5 cm total height, and parallel ducts with counterflow were a better configuration than serpentine flow. Based on the reported thermoelectric properties of MnSi1.75 and Mg2Si0.5Sn0.5, the maximum net electrical power achieved for the three parallel flow paths in a counterflow arrangement was 1
Modelling heating effects in cryocooled protein crystals
Nicholson, J; Fayz, K; Fell, B; Garman, E
2001-01-01
With the application of intense X-ray beams from third generation synchrotron sources, damage to cryocooled macromolecular crystals is being observed more commonly . In order to fully utilize synchrotron facilities now available for studying biological crystals, it is essential to understand the processes involved in radiation damage and beam heating so that, if possible, action can be taken to slow the rate of damage. Finite Element Analysis (FEA) has been applied to model the heating effects of X-rays on cryocooled protein crystals, and to compare the relative cooling efficiencies of nitrogen and helium.
Modeling of Dielectric Heating within Lyophilization Process
Directory of Open Access Journals (Sweden)
Jan Kyncl
2014-01-01
Full Text Available A process of lyophilization of paper books is modeled. The process of drying is controlled by a dielectric heating system. From the physical viewpoint, the task represents a 2D coupled problem described by two partial differential equations for the electric and temperature fields. The material parameters are supposed to be temperature-dependent functions. The continuous mathematical model is solved numerically. The methodology is illustrated with some examples whose results are discussed.
Heat transfer model for quenching by submerging
Energy Technology Data Exchange (ETDEWEB)
Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Song, Chunfeng; Liu, Qingling; Ji, Na; Deng, Shuai; Zhao, Jun; Kitamura, Yutaka
2016-05-01
Reducing energy penalty caused by drying and oil extraction is the most critical challenge in microalgae biodiesel production. In this study, vapor recompression and heat integration are utilized to optimize the performance of wet microalgae drying and oil extraction. In the microalgae drying stage, the hot exhaust stream is recompressed and coupled with wet microalgae to recover the condensate heat. In the oil extraction stage, the exergy rate of recovered solvent is also elevated by compressor and then exchanged heat with feed and bottom stream in the distillation column. Energy and mass balance of the intensified process is investigated and compared with the conventional microalgae drying-extraction process. The simulation results indicated that the total energy consumption of the intensified process can be saved by 52.4% of the conventional route. Copyright © 2016 Elsevier Ltd. All rights reserved.
A Simplified Heat Pump Model for use in Solar Plus Heat Pump System Simulation Studies
Perers, Bengt; Anderssen, Elsa; Nordman, Roger; Kovacs, Peter
2012-01-01
Solar plus heat pump systems are often very complex in design, with sometimes special heat pump arrangements and control. Therefore detailed heat pump models can give very slow system simulations and still not so accurate results compared to real heat pump performance in a system. The idea here is to start from a standard measured performance map of test points for a heat pump according to EN 14825 and then determine characteristic parameters for a simplified correlation based model of the he...
Heat transfer modeling an inductive approach
Sidebotham, George
2015-01-01
This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...
Heat Transfer Model for Hot Air Balloons
Llado-Gambin, Adriana
A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the modeling based on typical thermal input from a balloon propane burner. The burner duty cycle to keep a constant altitude can vary from 10% to 28% depending on the atmospheric conditions, and the ambient temperature is the parameter that most affects the total thermal input needed. The simulation and analysis also predict that the gas temperature inside the balloon decreases at a rate of -0.25 K/s when there is no burner activity, and it increases at a rate of +1 K/s when the balloon pilot operates the burner. The results were compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the simulation.
Directory of Open Access Journals (Sweden)
Lenhard Richard
2012-04-01
Full Text Available In the call OPVaV-2008/2.2/01-SORO Operational Programme Research and Development - knowledge and technology transfer from research and development into practice (ITMS-26220220057, whose strategic goal is "Device to use low-potential geothermal heat without forced circulation of heat carrier deep in the well "in the Department of Energy laboratory techniques to construct a simulator of transport low potential of geothermal energy in comparative test-drilling in the laboratory. The article describes a device that was designed as a scale model of two deep boreholes each of which withdraws the earth's heat by heat transfer technology and heat carrier. Device using forced circulation of heat carrier will respond in the construction of equipment currently used to transport heat from deep borehole. As the heat carrier will be used CO2. Facilities without using forced circulation of heat carrier, the new technology, which will be used as heat carrier ammonia (NH3.
Combined effect of ohmic heating and enzyme assisted aqueous extraction process on soy oil recovery.
Pare, Akash; Nema, Anurag; Singh, V K; Mandhyan, B L
2014-08-01
This research describes a new technological process for soybean oil extraction. The process deals with the combined effect of ohmic heating and enzyme assisted aqueous oil extraction process (EAEP) on enhancement of oil recovery from soybean seed. The experimental process consisted of following basic steps, namely, dehulling, wet grinding, enzymatic treatment, ohmic heating, aqueous extraction and centrifugation. The effect of ohmic heating parameters namely electric field strength (EFS), end point temperature (EPT) and holding time (HT) on aqueous oil extraction process were investigated. Three levels of electric field strength (i.e. OH600V, OH750V and OH900V), 3 levels of end point temperature (i.e. 70, 80 and 90 °C) and 3 levels of holding time (i.e. 0, 5 and 10 min.) were taken as independent variables using full factorial design. Percentage oil recovery from soybean by EAEP alone and EAEP coupled with ohmic heating were 53.12 % and 56.86 % to 73 % respectively. The maximum oil recovery (73 %) was obtained when the sample was heated and maintained at 90 °C using electric field strength of OH600V for a holding time of 10 min. The free fatty acid (FFA) of the extracted oil (i.e. in range of 0.97 to 1.29 %) was within the acceptable limit of 3 % (oleic acid) and 0.5-3 % prescribed respectively by PFA and BIS.
Computational model of heterogeneous heating in melanin
Kellicker, Jason; DiMarzio, Charles A.; Kowalski, Gregory J.
2015-03-01
Melanin particles often present as an aggregate of smaller melanin pigment granules and have a heterogeneous surface morphology. When irradiated with light within the absorption spectrum of melanin, these heterogeneities produce measurable concentrations of the electric field that result in temperature gradients from thermal effects that are not seen with spherical or ellipsoidal modeling of melanin. Modeling melanin without taking into consideration the heterogeneous surface morphology yields results that underestimate the strongest signals or over{estimate their spatial extent. We present a new technique to image phase changes induced by heating using a computational model of melanin that exhibits these surface heterogeneities. From this analysis, we demonstrate the heterogeneous energy absorption and resulting heating that occurs at the surface of the melanin granule that is consistent with three{photon absorption. Using the three{photon dluorescence as a beacon, we propose a method for detecting the extents of the melanin granule using photothermal microscopy to measure the phase changes resulting from the heating of the melanin.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the
Multilevel Flow Modeling of Domestic Heating Systems
DEFF Research Database (Denmark)
Hu, Junjie; Lind, Morten; You, Shi
2012-01-01
Multilevel Flow Modeling (MFM) is a well recognized methodology for functional modeling of complex systems which primarily focuses on the representation of their goals and functions. It has been successfully used in industrial process, e.g. nuclear power plant, chemical plants etc. to facilitate...... i.e. supplying and transferring thermal energy, it is off interest to use MFM to investigate similarities and differences between different implementations. In this paper, three typical domestic European heating systems, which differ from each other in the number of temperature sensors and auxiliary...
Thermal Transport Model for Heat Sink Design
Chervenak, James A.; Kelley, Richard L.; Brown, Ari D.; Smith, Stephen J.; Kilbourne, Caroline a.
2009-01-01
A document discusses the development of a finite element model for describing thermal transport through microcalorimeter arrays in order to assist in heat-sinking design. A fabricated multi-absorber transition edge sensor (PoST) was designed in order to reduce device wiring density by a factor of four. The finite element model consists of breaking the microcalorimeter array into separate elements, including the transition edge sensor (TES) and the silicon substrate on which the sensor is deposited. Each element is then broken up into subelements, whose surface area subtends 10 10 microns. The heat capacity per unit temperature, thermal conductance, and thermal diffusivity of each subelement are the model inputs, as are the temperatures of each subelement. Numerical integration using the Finite in Time Centered in Space algorithm of the thermal diffusion equation is then performed in order to obtain a temporal evolution of the subelement temperature. Thermal transport across interfaces is modeled using a thermal boundary resistance obtained using the acoustic mismatch model. The document concludes with a discussion of the PoST fabrication. PoSTs are novel because they enable incident x-ray position sensitivity with good energy resolution and low wiring density.
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
de Jong, J A; Wijnant, Y H; de Boer, A
2014-03-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.
Heat transfer optimization of SCO2 porous flow based on Brinkman model
Directory of Open Access Journals (Sweden)
Lin David T.W.
2016-01-01
Full Text Available The purpose of this study is to obtain the optimal operating condition in order to find the maximum supercritical CO2 heat extraction in the enhanced geothermal system (EGS. In this study, the heat transfer model conjugated with the Brinkman model is used to evaluate the thermal behavior in the reservoir of the EGS. This numerical model is validated by experiment. Optimization is processed based on the Nelder-Mead approach. The optimal operating conditions are proposed with different pressure, porosity. This study will build the optimal platform of heat source of geothermal power plant.
Modeling terahertz heating effects on water.
Kristensen, Torben T L; Withayachumnankul, Withawat; Jepsen, Peter U; Abbott, Derek
2010-03-01
We apply Kirchhoff's heat equation to model the influence of a CW terahertz beam on a sample of water, which is assumed to be static. We develop a generalized model, which easily can be applied to other liquids and solids by changing the material constants. If the terahertz light source is focused down to a spot with a diameter of 0.5 mm, we find that the steady-state temperature increase per milliwatt of transmitted power is 1.8?C/mW. A quantum cascade laser can produce a CW beam in the order of several milliwatts and this motivates the need to estimate the effect of beam power on the sample temperature. For THz time domain systems, we indicate how to use our model as a worst-case approximation based on the beam average power. It turns out that THz pulses created from photoconductive antennas give a negligible increase in temperature. As biotissue contains a high water content, this leads to a discussion of worst-case predictions for THz heating of the human body in order to motivate future detailed study. An open source Matlab implementation of our model is freely available for use at www.eleceng.adelaide.edu.au/thz.
A simplified heat pump model for use in solar plus heat pump system simulation studies
DEFF Research Database (Denmark)
Perers, Bengt; Andersen, Elsa; Nordman, Roger
2012-01-01
Solar plus heat pump systems are often very complex in design, with sometimes special heat pump arrangements and control. Therefore detailed heat pump models can give very slow system simulations and still not so accurate results compared to real heat pump performance in a system. The idea here...... is to start from a standard measured performance map of test points for a heat pump according to EN 14825 and then determine characteristic parameters for a simplified correlation based model of the heat pump. By plotting heat pump test data in different ways including power input and output form and not only...... as COP, a simplified relation could be seen. By using the same methodology as in the EN 12975 QDT part in the collector test standard it could be shown that a very simple model could describe the heat pump test data very accurately, by identifying 4 parameters in the correlation equation found....
Verification of Conjugate Heat Transfer Models in a Closed Volume with Radiative Heat Source
Directory of Open Access Journals (Sweden)
Maksimov Vyacheslav I.
2016-01-01
Full Text Available The results of verification of mathematical model of convective-conductive heat transfer in a closed volume with a thermally conductive enclosing structures are presented. Experiments were carried out to determine the temperature of floor premises in the working conditions of radiant heating systems. Comparison of mathematical modelling of temperature fields and experiments showed their good agreement. It is concluded that the mathematical model of conjugate heat transfers in the air cavity with a heat-conducting and heat-retaining walls correspond to the real process of formation of temperature fields in premises with gas infrared heaters system.
Reduced dimension model for heat transfer of ground heat exchanger in permafrost
Vasilyeva, M.; Stepanov, S.; Sirditov, I.
2017-12-01
In this work, we present reduced dimensional model for heat transfer processes of ground heat exchanger in permafrost. A mathematical model is described by a coupled system of equations for heat transfer in the ground subdomain and in heat exchanger (pipes). Because radius of the pipes is very small compared to the size of surrounding ground, we write heat transfer problem in pipes as reduced dimensional equation, where we consider pipes as one-dimensional lines. We present a computational algorithm and numerical results for model problem.
Modeling of heat conduction via fractional derivatives
Fabrizio, Mauro; Giorgi, Claudio; Morro, Angelo
2017-09-01
The modeling of heat conduction is considered by letting the time derivative, in the Cattaneo-Maxwell equation, be replaced by a derivative of fractional order. The purpose of this new approach is to overcome some drawbacks of the Cattaneo-Maxwell equation, for instance possible fluctuations which violate the non-negativity of the absolute temperature. Consistency with thermodynamics is shown to hold for a suitable free energy potential, that is in fact a functional of the summed history of the heat flux, subject to a suitable restriction on the set of admissible histories. Compatibility with wave propagation at a finite speed is investigated in connection with temperature-rate waves. It follows that though, as expected, this is the case for the Cattaneo-Maxwell equation, the model involving the fractional derivative does not allow the propagation at a finite speed. Nevertheless, this new model provides a good description of wave-like profiles in thermal propagation phenomena, whereas Fourier's law does not.
Local business models for district heat production; Kaukolaemmoen paikalliset liiketoimintamallit
Energy Technology Data Exchange (ETDEWEB)
Hakala, L.; Pesola, A.; Vanhanen, J.
2012-12-15
Local district heating business, outside large urban centers, is a profitable business in Finland, which can be practiced with several different business models. In addition to the traditional, local district heating business, local district heat production can be also based on franchising business model, on integrated service model or on different types of cooperation models, either between a local district heat producer and industrial site providing surplus heat or between a local district heat producer and a larger district heating company. Locally available wood energy is currently utilized effectively in the traditional district heating business model, in which a local entrepreneur produces heat to consumers in the local area. The franchising model is a more advanced version of the traditional district heating entrepreneurship. In this model, franchisor funds part of the investments, as well as offers centralized maintenance and fuel supply, for example. In the integrated service model, the local district heat producer offers also energy efficiency services and other value-added services, which are based on either the local district heat suppliers or his partner's expertise. In the cooperation model with industrial site, the local district heating business is based on the utilization of the surplus heat from the industrial site. In some cases, profitable operating model approach may be a district heating company outsourcing operations of one or more heating plants to a local entrepreneur. It can be concluded that all business models for district heat production (traditional district heat business model, franchising, integrated service model, cooperative model) discussed in this report can be profitable in Finnish conditions, as well for the local heat producer as for the municipality - and, above all, they produce cost-competitive heat for the end-user. All the models were seen as viable and interesting and having possibilities for expansion Finland
Modeling and Experimental Validation of a Transient Direct Expansion Heat Pump
Directory of Open Access Journals (Sweden)
Clément Rousseau
2017-06-01
Full Text Available Geothermal heat pump technology is currently one of the most interesting technologies used to heat buildings. There are two designs used in the industry: geothermal heat pump using a secondary ground loop and Direct Expansion (DX ground source heat pump. The latter is less used, possibly because less research has been carried out for the design of this kind of heat pump. In this paper, a transient model using the Comsol Multiphysic of a DX ground heat pump is presented in heating mode with R22, and a comparison with experimental results is presented with a 24-hour test. It is shown that the model was adequately validated by our experiment with only a maximum difference of 15%. Following this validation, a parametric analysis was realised on the geometry of the borehole. This study concluded that to have the best heat extraction of the ground, the pipes shank spacing need to be important without increasing the borehole diameter. Keywords: Direct Expansion geothermal heat pump, Modeling, R22 Article History: Received January 16th 2017; Received in revised form May 28th 2017; Accepted June 6th 2017; Available online How to Cite This Article: Rousseau, C., Fannou, J.L.C., Lamarche, L. and Kajl, S. (2017 Modeling and Experimental Validation of a Transient Direct Expansion Heat Pump. International Journal of Renewable Energy Develeopment, 6(2, 145-155. https://doi.org/10.14710/ijred.6.2.145-155
de Aguiar Cipriano, Paula; Ekici, Lutfiye; Barnes, Ryan C; Gomes, Carmen; Talcott, Stephen T
2015-08-01
Purple sweet potatoes (PSP) have been used as a natural food colorant with high acylated anthocyanins concentrations. Commercially extracting pigments from PSP can be challenging due to firm texture and high polyphenol oxidase (PPO) content. These studies evaluated hot water immersions (30, 50, 70, and 90°C for 10 min) as pre-heating treatments and addition of PPO inhibitors (citric acid, oxalic acid, and sodium borate) to aqueous extraction solutions to aid pigment recovery. Predominant PSP anthocyanins included acylated cyanidin or peonidin derivatives. Non-pigmented cinnamates acted as oxidase substrates and induced co-oxidation reactions with anthocyanins. Pre-heating PSP significantly increased polyphenolic yields in a temperature-dependent manner, consistent with tissue softening and PPO inactivation. The use of solvent modifiers in the extraction solution associated with heat helped minimize enzyme action and increased polyphenolic recovery. Minimizing the impact of PPO with heat was critical to the extraction and recovery of PSP anthocyanins, suitable for food use. Copyright © 2015 Elsevier Ltd. All rights reserved.
Patraşcu, Iulian; Bildea, Costin Sorin; Kiss, Anton A.
Recently, a novel heat-pump-assisted extractive distillation process taking place in a dividing-wall column was proposed for bioethanol dehydration. This integrated design combines three distillation columns into a single unit that allows over 40% energy savings and low specific energy requirements
Actant model of an extraction plant
Energy Technology Data Exchange (ETDEWEB)
Poulsen, Helle
1999-05-01
Facing a growing complexity of industrial plants, we recognise the need for qualitative modelling methods capturing functional and causal complexity in a human-centred way. The present paper presents actant modelling as a functional modelling method rooted in linguistics and semiotics. Actant modelling combines actant models from linguistics with multilevel flow modelling (MFM). Thus the semantics of MFM functions is developed further and given an interpretation in terms of actant functions. The present challenge is to provide coherence between seemingly different categories of knowledge. Yet the gap between functional and causal modelling methods can be bridged. Actant modelling provides an open and provisional, but in no way exhaustive or final answer as to how teleological concepts like goals and functions relate to causal concepts. As the main focus of the paper an actant model of an extraction plant is presented. It is shown how the actant model merges functional and causal knowledge in a natural way.
Reaction Wheel Disturbance Model Extraction Software - RWDMES
Blaurock, Carl
2009-01-01
The RWDMES is a tool for modeling the disturbances imparted on spacecraft by spinning reaction wheels. Reaction wheels are usually the largest disturbance source on a precision pointing spacecraft, and can be the dominating source of pointing error. Accurate knowledge of the disturbance environment is critical to accurate prediction of the pointing performance. In the past, it has been difficult to extract an accurate wheel disturbance model since the forcing mechanisms are difficult to model physically, and the forcing amplitudes are filtered by the dynamics of the reaction wheel. RWDMES captures the wheel-induced disturbances using a hybrid physical/empirical model that is extracted directly from measured forcing data. The empirical models capture the tonal forces that occur at harmonics of the spin rate, and the broadband forces that arise from random effects. The empirical forcing functions are filtered by a physical model of the wheel structure that includes spin-rate-dependent moments (gyroscopic terms). The resulting hybrid model creates a highly accurate prediction of wheel-induced forces. It accounts for variation in disturbance frequency, as well as the shifts in structural amplification by the whirl modes, as the spin rate changes. This software provides a point-and-click environment for producing accurate models with minimal user effort. Where conventional approaches may take weeks to produce a model of variable quality, RWDMES can create a demonstrably high accuracy model in two hours. The software consists of a graphical user interface (GUI) that enables the user to specify all analysis parameters, to evaluate analysis results and to iteratively refine the model. Underlying algorithms automatically extract disturbance harmonics, initialize and tune harmonic models, and initialize and tune broadband noise models. The component steps are described in the RWDMES user s guide and include: converting time domain data to waterfall PSDs (power spectral
Anti-polymerization activity of tea and fruits extracts during rapeseed oil heating.
Kmiecik, Dominik; Gramza-Michałowska, Anna; Korczak, Józef
2018-01-15
The aim of the study was to analyze the influence of natural antioxidants on polymerization of partially hydrogenated rapeseed oil heated in 170°C for 40h. In the research ethanolic extracts of green tea leaves (China Lung Ching), yellow tea leaves (China Kakecha), cranberry, blackberry, and lime were used. The yellow and green tea extracts were characterized by the highest content of total polyphenol and antioxidant activity. Polymers of triacylglycerols were found only in the polar fraction of heated oil. During heating, the increase of dimers, trimers, and oligomers was observed. However, it was dependent on the used additives and not directly related to the content of phenolic compounds and their antioxidant activity. The final content of polymers in oil samples increased in the fallowing order: green teaoil without additives. Copyright © 2017 Elsevier Ltd. All rights reserved.
Sari, I. M.
2017-02-01
Teacher plays a crucial role in Education. Helping students construct scientifically mental model is one of obligation of Physics Education Department of Teacher Education Institute that produce physics teacher. Excavating students’ mental model is necessary to be done in physics education. This research was first to identify 23 physics students’ mental model of heat and heat conduction. A series of semi-structured interviews was conducted to excavate the students’ understanding of heat and mental models on heat conduction. The students who involved in this study come from different level from sophomore to master degree in Physics Education Department. This study adopted a constant comparison method to obtain the patterns of the participants’ responses through the students’ writing, drawing and verbal utterances. The framework for assessing mental model and the instruments were adopted and adapted from Chiou and Anderson (2010). We also compared the students’ understanding of heat and mental models on heat conduction. The result shows that Heat is treated as Intrinsic property, material substances, and caloric flow. None of students expressed heat as transfer of thermal energy. Moreover, there are two kinds of students’ fundamental component of mental model in heat conduction were found: medium and molecules. Students understanding of heat and fundamental components of mental model in heat conduction are not resulted from running mental model.
Shalaginova, Z. I.
2016-03-01
The mathematical model and calculation method of the thermal-hydraulic modes of heat points, based on the theory of hydraulic circuits, being developed at the Melentiev Energy Systems Institute are presented. The redundant circuit of the heat point was developed, in which all possible connecting circuits (CC) of the heat engineering equipment and the places of possible installation of control valve were inserted. It allows simulating the operating modes both at central heat points (CHP) and individual heat points (IHP). The configuration of the desired circuit is carried out automatically by removing the unnecessary links. The following circuits connecting the heating systems (HS) are considered: the dependent circuit (direct and through mixing elevator) and independent one (through the heater). The following connecting circuits of the load of hot water supply (HWS) were considered: open CC (direct water pumping from pipelines of heat networks) and a closed CC with connecting the HWS heaters on single-level (serial and parallel) and two-level (sequential and combined) circuits. The following connecting circuits of the ventilation systems (VS) were also considered: dependent circuit and independent one through a common heat exchanger with HS load. In the heat points, water temperature regulators for the hot water supply and ventilation and flow regulators for the heating system, as well as to the inlet as a whole, are possible. According to the accepted decomposition, the model of the heat point is an integral part of the overall heat-hydraulic model of the heat-supplying system having intermediate control stages (CHP and IHP), which allows to consider the operating modes of the heat networks of different levels connected with each other through CHP as well as connected through IHP of consumers with various connecting circuits of local systems of heat consumption: heating, ventilation and hot water supply. The model is implemented in the Angara data
Dynamic heat capacity of the east model and of a bead-spring polymer model.
Energy Technology Data Exchange (ETDEWEB)
McCoy, John Dwane (New Mexico Institute of Mining and Technology, Socorro, NM); Brown, Jonathan R. (New Mexico Institute of Mining and Technology, Socorro, NM); Adolf, Douglas Brian
2011-10-01
In this report we have presented a brief review of the glass transition and one means of characterizing glassy materials: linear and nonlinear thermodynamic oscillatory experiments to extract the dynamic heat capacity. We have applied these methods to the east model (a variation of the Ising model for glass forming systems) and a simple polymeric system via molecular dynamics simulation, and our results match what is seen in experiment. For the east model, since the dynamics are so simple, a mathematical model is developed that matches the simulated dynamics. For the polymeric system, since the system is a simulation, we can instantaneously 'quench' the system - removing all vibrational energy - to separate the vibrational dynamics from dynamics associated with particle rearrangements. This shows that the long-time glassy dynamics are due entirely to the particle rearrangements, i.e. basin jumping on the potential energy landscape. Finally, we present an extension of linear dynamic heat capacity to the nonlinear regime.
Yao Chen; Yongming Fan; Jianmin Gao; Mandla A. Tshabalala; Nicole M. Stark
2012-01-01
To investigate the role of extractives on heat-induced discoloration of wood, samples of black locust (Robinia pseudoacacia) wood flour were extracted with various solvents prior to heat-treatment. Analysis of their color parameters and chromophoric structures showed that the chroma value of the unextracted sample decreased while that of the...
Modeling heat efficiency, flow and scale-up in the corotating disc scraped surface heat exchanger
DEFF Research Database (Denmark)
Friis, Alan; Szabo, Peter; Karlson, Torben
2002-01-01
A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer...... performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key...
Inverse hydrochemical models of aqueous extracts tests
Energy Technology Data Exchange (ETDEWEB)
Zheng, L.; Samper, J.; Montenegro, L.
2008-10-10
Aqueous extract test is a laboratory technique commonly used to measure the amount of soluble salts of a soil sample after adding a known mass of distilled water. Measured aqueous extract data have to be re-interpreted in order to infer porewater chemical composition of the sample because porewater chemistry changes significantly due to dilution and chemical reactions which take place during extraction. Here we present an inverse hydrochemical model to estimate porewater chemical composition from measured water content, aqueous extract, and mineralogical data. The model accounts for acid-base, redox, aqueous complexation, mineral dissolution/precipitation, gas dissolution/ex-solution, cation exchange and surface complexation reactions, of which are assumed to take place at local equilibrium. It has been solved with INVERSE-CORE{sup 2D} and been tested with bentonite samples taken from FEBEX (Full-scale Engineered Barrier EXperiment) in situ test. The inverse model reproduces most of the measured aqueous data except bicarbonate and provides an effective, flexible and comprehensive method to estimate porewater chemical composition of clays. Main uncertainties are related to kinetic calcite dissolution and variations in CO2(g) pressure.
Modeling of Heating During Food Processing
Zheleva, Ivanka; Kamburova, Veselka
Heat transfer processes are important for almost all aspects of food preparation and play a key role in determining food safety. Whether it is cooking, baking, boiling, frying, grilling, blanching, drying, sterilizing, or freezing, heat transfer is part of the processing of almost every food. Heat transfer is a dynamic process in which thermal energy is transferred from one body with higher temperature to another body with lower temperature. Temperature difference between the source of heat and the receiver of heat is the driving force in heat transfer.
Numerical Modelling of Indution Heating - Fundamentals
DEFF Research Database (Denmark)
Zhang, Wenqi
Induction heating is extensively used for brazing and heat treatment of materials to produce consumer and industrial products; structural assemblies; electrical and electronic products; mining, machine, and hand tools; ordnance equipment; and aerospace assemblies. It is often applied when rapid...
Large scale solar district heating. Evaluation, modelling and designing
Energy Technology Data Exchange (ETDEWEB)
Heller, A.
2000-07-01
The main objective of the research was to evaluate large-scale solar heating connected to district heating (CSDHP), to build up a simulation tool and to demonstrate the application of the tool for design studies and on a local energy planning case. The evaluation of the central solar heating technology is based on measurements on the case plant in Marstal, Denmark, and on published and unpublished data for other, mainly Danish, CSDHP plants. Evaluations on the thermal, economical and environmental performances are reported, based on the experiences from the last decade. The measurements from the Marstal case are analysed, experiences extracted and minor improvements to the plant design proposed. For the detailed designing and energy planning of CSDHPs, a computer simulation model is developed and validated on the measurements from the Marstal case. The final model is then generalised to a 'generic' model for CSDHPs in general. The meteorological reference data, Danish Reference Year, is applied to find the mean performance for the plant designs. To find the expectable variety of the thermal performance of such plants, a method is proposed where data from a year with poor solar irradiation and a year with strong solar irradiation are applied. Equipped with a simulation tool design studies are carried out spreading from parameter analysis over energy planning for a new settlement to a proposal for the combination of plane solar collectors with high performance solar collectors, exemplified by a trough solar collector. The methodology of utilising computer simulation proved to be a cheap and relevant tool in the design of future solar heating plants. The thesis also exposed the demand for developing computer models for the more advanced solar collector designs and especially for the control operation of CSHPs. In the final chapter the CSHP technology is put into perspective with respect to other possible technologies to find the relevance of the application
Cruden, Brett A.; Brandis, Aaron M.; White, Todd R.; Mahzari, Milad; Bose, Deepak
2014-01-01
During the recent entry of the Mars Science Laboratory (MSL), the heat shield was equipped with thermocouple stacks to measure in-depth heating of the thermal protection system (TPS). When only convective heating was considered, the derived heat flux from gauges in the stagnation region was found to be underpredicted by as much as 17 W/sq cm, which is significant compared to the peak heating of 32 W/sq cm. In order to quantify the contribution of radiative heating phenomena to the discrepancy, ground tests and predictive simulations that replicated the MSL entry trajectory were performed. An analysis is carried through to assess the quality of the radiation model and the impact to stagnation line heating. The impact is shown to be significant, but does not fully explain the heating discrepancy.
Nishizawa, Kaho; Masuda, Tetsuya; Takenaka, Yasuyuki; Masui, Hironori; Tani, Fumito; Arii, Yasuhiro
2016-08-01
Sword bean (Canavalia gladiata) seeds are a traditional food in Asian countries. In this study, we aimed to determine the optimal methods for the precipitation of sword bean proteins useful for the food development. The soaking time for sword beans was determined by comparing it with that for soybeans. Sword bean proteins were extracted from dried seeds in distilled water using novel methods. We found that most proteins could be precipitated by heating the extract at more than 90 °C. Interestingly, adding magnesium chloride to the extract at lower temperatures induced specific precipitation of a single protein with a molecular weight of approximately 48 kDa. The molecular weight and N-terminal sequence of the precipitated protein was identical to that of canavalin. These data suggested that canavalin was precipitated by the addition of magnesium chloride to the extract. Our results provide important insights into the production of processed foods from sword bean.
Modelling floor heating systems using a validated two-dimensional ground coupled numerical model
DEFF Research Database (Denmark)
Weitzmann, Peter; Kragh, Jesper; Roots, Peter
2005-01-01
and foundation on the performance of the floor heating sys-tem. The ground coupled floor heating model is validated against measurements from a single-family house. The simulation model is coupled to a whole-building energy simu-lation model with inclusion of heat losses and heat supply to the room above...... the floor. This model can be used to design energy efficient houses with floor heating focusing on the heat loss through the floor construction and foundation. It is found that it is impor-tant to model the dynamics of the floor heating system to find the correct heat loss to the ground, and further...
MODELLING OF HEAT CONDUCTIVITY OF COMPOSITE MATERIALS WITH BALL INCLUSIONS
Directory of Open Access Journals (Sweden)
V. Pugachev Oleg
2017-01-01
Full Text Available A number of papers deals with the heat conductivity of composite materials: Zarubin et al used new approaches to the problem of evaluation of the effective heat conductivity coefficients of composite material with ball inclusions. We used variational analysis for a simplified model in a vicinity of inclusion. Contemporary computers allow implementing another approach to solving the problem of the effective heat conductivity: it may be modelled by the Brownian motion of virtual heat particles. The main idea is to obtain the exact formula for the heat conductivity for a homogeneous material and subsequently obtain a statistical evaluation of this formula for a composite material.In the present paper we compare two methods for finding the effective heat conductivity coefficients of composite materials by modeling the process of heat conduction via the Brownian motion of virtual heat particles. We consider a composite with ball inclusions of a material with heat conductivity and heat capacity coefficientsdiffering from those of the matrix material. In a computational experiment, we simulate the process of heatconduction through a flat layer of the composite material, which has been heated on one side at the initial moment. In order to find the confidence interval for the effective heat conductivity coefficient, we find, by means of statistics, either the displacement of the center of heat energy, or the probability of a virtual particle to pass through the layer during a certain time. We compare our results with theoretical assessments suggested by other authors.
Feru, E.; Willems, F.P.T.; Rojer, C.; Jager, B. de; Steinbuch, M.
2013-01-01
To meet future CO2 emission targets, Waste Heat Recovery systems have recently attracted much attention for automotive applications, especially for long haul trucks. This paper focuses on the development of a dynamic counter-flow heat exchanger model for control purposes. The model captures the
Variability extraction and modeling for product variants.
Linsbauer, Lukas; Lopez-Herrejon, Roberto Erick; Egyed, Alexander
2017-01-01
Fast-changing hardware and software technologies in addition to larger and more specialized customer bases demand software tailored to meet very diverse requirements. Software development approaches that aim at capturing this diversity on a single consolidated platform often require large upfront investments, e.g., time or budget. Alternatively, companies resort to developing one variant of a software product at a time by reusing as much as possible from already-existing product variants. However, identifying and extracting the parts to reuse is an error-prone and inefficient task compounded by the typically large number of product variants. Hence, more disciplined and systematic approaches are needed to cope with the complexity of developing and maintaining sets of product variants. Such approaches require detailed information about the product variants, the features they provide and their relations. In this paper, we present an approach to extract such variability information from product variants. It identifies traces from features and feature interactions to their implementation artifacts, and computes their dependencies. This work can be useful in many scenarios ranging from ad hoc development approaches such as clone-and-own to systematic reuse approaches such as software product lines. We applied our variability extraction approach to six case studies and provide a detailed evaluation. The results show that the extracted variability information is consistent with the variability in our six case study systems given by their variability models and available product variants.
Purification of Single-Wall carbon nanotubes by heat treatment and supercritical extraction
Directory of Open Access Journals (Sweden)
Mariana Bertoncini
2011-09-01
Full Text Available Arc discharge is the most practical method for the synthesis of single wall carbon nanotubes (SWCNT. However, the production of SWCNT by this technique has low selectivity and yield, requiring further purification steps. This work is a study of purification of SWCNT by heat treatment in an inert atmosphere followed by supercritical fluid extraction. The raw arc discharge material was first heat-treated at 1250 °C under argon. The nanotubes were further submitted to an extraction process using supercritical CO2 as solvent. A surfactant (tributylphosphate, TBP and a chelating agent (hexafluoroacetylacetone, HFA were used together to eliminate metallic impurities from the remaining arc discharge catalysts. Analysis of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES showed an efficient removal of iron and cobalt (>80%. The purified nanotubes were further analyzed by TGA and Raman spectroscopy.
Obeidat, Omar; Yu, Qiuye; Han, Xiaoyan
2016-12-01
Sonic IR imaging is an emerging NDE technology. This technology uses short pulses of ultrasonic excitation together with infrared imaging to detect defects in materials and structures. Sonic energy is coupled to the specimen under inspection by means of direct contact between the transducer tip and the specimen at some convenient point. This region which is normally in the field of view of the camera appears as intensity peak in the image which might be misinterpreted as defects or obscure the detection and/or extraction of the defect signals in the proximity of the contact region. Moreover, certain defects may have very small heat signature or being buried in noise. In this paper, we present algorithms to improve defect extraction and suppression of undesired heat patterns in sonic IR images. Two approaches are presented, each fits to a specific category of sonic IR images.
Agent-based modelling of heating system adoption in Norway
Energy Technology Data Exchange (ETDEWEB)
Sopha, Bertha Maya; Kloeckner, Christian A.; Hertwich, Edgar G.
2010-07-01
Full text: This paper introduces agent-based modelling as a methodological approach to understand the effect of decision making mechanism on the adoption of heating systems in Norway. The model is used as an experimental/learning tool to design possible interventions, not for prediction. The intended users of the model are therefore policy designers. Primary heating system adoptions of electric heating, heat pump and wood pellet heating were selected. Random topology was chosen to represent social network among households. Agents were households with certain location, number of peers, current adopted heating system, employed decision strategy, and degree of social influence in decision making. The overall framework of decision-making integrated theories from different disciplines; customer behavior theory, behavioral economics, theory of planned behavior, and diffusion of innovation, in order to capture possible decision making processes in households. A mail survey of 270 Norwegian households conducted in 2008 was designed specifically for acquiring data for the simulation. The model represents real geographic area of households and simulates the overall fraction of adopted heating system under study. The model was calibrated with historical data from Statistics Norway (SSB). Interventions with respects to total cost, norms, indoor air quality, reliability, supply security, required work, could be explored using the model. For instance, the model demonstrates that a considerable total cost (investment and operating cost) increase of electric heating and heat pump, rather than a reduction of wood pellet heating's total cost, are required to initiate and speed up wood pellet adoption. (Author)
Heat Source Models in Simulation of Heat Flow in Friction Stir Welding
DEFF Research Database (Denmark)
Schmidt, Henrik Nikolaj Blich; Hattel, Jesper
2004-01-01
The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in Friction Stir Welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms....... The models are configured in terms of the the heat source as i) shoulder contribution only, ii) shoulder and probe contribution, the latter as a volume heat source distributed in the probe volume and iii) shoulder and probe contribution distributed at the contact interface, i.e. as a surface flux in the case...
MODEL OF HEAT SIMULATOR FOR DATA CENTERS
Directory of Open Access Journals (Sweden)
Jan Novotný
2016-08-01
Full Text Available The aim of this paper is to present a design and a development of a heat simulator, which will be used for a flow research in data centers. The designed heat simulator is based on an ideological basis of four-processor 1U Supermicro server. The designed heat simulator enables to control the flow and heat output within the range of 10–100 %. The paper covers also the results of testing measurements of mass flow rates and heat flow rates in the simulator. The flow field at the outlet of the server was measured by the stereo PIV method. The heat flow rate was determined, based on measuring the temperature field at the inlet and outlet of the simulator and known mass flow rate.
Present-day heat flow model of Mars
Parro, Laura M.; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier
2017-04-01
Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m-2, with an average value of 19 mW m-2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7-0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic.
CFD Modeling of Launch Vehicle Aerodynamic Heating
Tashakkor, Scott B.; Canabal, Francisco; Mishtawy, Jason E.
2011-01-01
The Loci-CHEM 3.2 Computational Fluid Dynamics (CFD) code is being used to predict Ares-I launch vehicle aerodynamic heating. CFD has been used to predict both ascent and stage reentry environments and has been validated against wind tunnel tests and the Ares I-X developmental flight test. Most of the CFD predictions agreed with measurements. On regions where mismatches occurred, the CFD predictions tended to be higher than measured data. These higher predictions usually occurred in complex regions, where the CFD models (mainly turbulence) contain less accurate approximations. In some instances, the errors causing the over-predictions would cause locations downstream to be affected even though the physics were still being modeled properly by CHEM. This is easily seen when comparing to the 103-AH data. In the areas where predictions were low, higher grid resolution often brought the results closer to the data. Other disagreements are attributed to Ares I-X hardware not being present in the grid, as a result of computational resources limitations. The satisfactory predictions from CHEM provide confidence that future designs and predictions from the CFD code will provide an accurate approximation of the correct values for use in design and other applications
Terpinc, Petra; Polak, Tomaz; Ulrih, Natasa Poklar; Abramovic, Helena
2011-08-24
The effect of different heat treatments of camelina (Camelina sativa) seeds on the phenolic profile and antioxidant activity of their hydrolyzed extracts was investigated. The results showed that total phenol contents increased in thermally treated seeds. Heat treatment affected also the quantities of individual phenolic compounds in extracts. Phenolics in unheated camelina seeds existed in bound rather than in free form. A temperature of 160 °C was required for release of insoluble bound phenolics, whereas lower temperatures were found to be optimal to liberate those present as soluble conjugates. The best reducing power and alkyl peroxyl radical scavenging activity in the emulsion was expressed by phenolics which were bound to the cell wall, whereas the best iron chelators and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavengers were found to be those present in free form. The heat treatment of seeds up to 120 °C increased the reducing power and DPPH• radical scavenging ability of extracts, but negatively affected iron chelating ability and their activity in an emulsion against alkyl peroxyl radicals.
Absorption Cycle Heat Pump Model for Control Design
DEFF Research Database (Denmark)
Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard
2015-01-01
Heat pumps have recently received increasing interest due to green energy initiatives and increasing energy prices. In this paper, a nonlinear dynamic model of a single-effect LiBr-water absorption cycle heat pump is derived for simulation and control design purposes. The model is based...... on an actual heat pump located at a larger district heating plant. The model is implemented in Modelica and is based on energy and mass balances, together with thermodynamic property functions for LiBr and water and staggered grid representations for heat exchangers. Model parameters have been fitted...... to operational data and different scenarios are simulated to investigate the operational stability of the heat pump. Finally, this paper provides suggestions and examples of derivation of lower order linear models for control design. © Copyright IEEE - All rights reserved....
Modelling and performance of heat pipes with long evaporator sections
Wits, Wessel W.; te Riele, Gert Jan
2017-11-01
This paper presents a planar cooling strategy for advanced electronic applications using heat pipe technology. The principle idea is to use an array of relatively long heat pipes, whereby heat is disposed to a long section of the pipes. The proposed design uses 1 m long heat pipes and top cooling through a fan-based heat sink. Successful heat pipe operation and experimental performances are determined for seven heating configurations, considering active bottom, middle and top sections, and four orientation angles (0°, 30°, 60° and 90°). For all heating sections active, the heat pipe oriented vertically in an evaporator-down mode and a power input of 150 W, the overall thermal resistance was 0.014 K/W at a thermal gradient of 2.1 K and an average operating temperature of 50.7 °C. Vertical operation showed best results, as can be expected; horizontally the heat pipe could not be tested up to the power limit and dry-out occurred between 20 and 80 W depending on the heating configuration. Heating configurations without the bottom section active demonstrated a dynamic start-up effect, caused by heat conduction towards the liquid pool and thereafter batch-wise introducing the working fluid into the two-phase cycle. By analysing the heat pipe limitations for the intended operating conditions, a suitable heat pipe geometry was chosen. To predict the thermal performance a thermal model using a resistance network was created. The model compares well with the measurement data, especially for higher input powers. Finally, the thermal model is used for the design of a 1 kW planar system-level electronics cooling infrastructure featuring six 1 m heat pipes in parallel having a long ( 75%) evaporator section.
Tooth extraction decision model in periodontitis patients.
Popelut, A; Rousval, B; Fromentin, O; Feghali, M; Mora, F; Bouchard, P
2010-01-01
The purpose of this study was to build, around several types of input data, a decision analysis model for dental extraction strategy in periodontitis patients. The decision analysis was based on the following scenario: a fictitious adult chronic periodontitis patient with no chief complaint, being referred to make a decision of extraction on one single tooth presenting a periodontal defect that may affect the decision-making process. A decision tree was used to identify the treatment options within the next 5 years. Scientific evidences were based on probabilities given by a literature analysis using a systematic approach. Clinical expertize was based on subjective utilities (SUs) assigned by an experts' panel. Expected utilities (EUs) were used to rank the following options: no treatment (EU(1)) or periodontal treatment (EU(2)); extraction followed by a tooth-supported fixed partial denture - FPD - (EU(3)) or an implant-supported single crown - ISC - (EU(4)). The robustness analysis calculation indicates that the probability of tooth survival needed to be equal to 0.78 in order that the passive option becomes optimal. However, EU(1) was impossible to calculate due to the lack of available probabilities. The EU intervals were 79-96, 86-89 and 94-95 for EU(2), EU(3) and EU(4), respectively. Consequently, the FPD option is dominated by the ISC option, and it is not possible to conclude to a difference between the periodontal and the ISC therapy. Within the limits of this model, tooth extraction followed by FPD is the worst strategy compared with ISC or periodontal therapies.
Firestone, Gabriel; Bochinski, Jason; Meth, Jeffrey; Clarke, Laura
Understanding of the heat transfer characteristics of a polymer during processing is critical to predicting and controlling the resulting properties and has been studied extensively in injection molding. As new methodologies for polymer processing are developed, such as photothermal heating, it is important to build an understanding of how heat transfer properties change under these novel conditions. By combining theoretical and experimental approaches, the thermal properties of photothermally heated polymer films were measured. The key idea is that by measuring the steady state temperature profile of a spot heated polymer film via a fluorescence probe (the temperature versus distance from the heated region) and fitting to a theoretical model, heat transfer coefficients can be extracted. We apply this approach to three different polymer systems, crosslinked epoxy, poly(methyl methacrylate) and poly(ethylene oxide) thin films with a range of thicknesses, under different heating laser intensities and with different resultant temperatures. We will discuss the resultant trends and extension of the model beyond a simple spot heating configuration. Support from National Science Foundation CMMI-1069108 and CMMI-1462966.
Analytical models of Ohmic heating and conventional heating in food processing
Serventi, A.; Bozzoli, F.; Rainieri, S.
2017-11-01
Ohmic heating is a food processing operation in which an electric current is passed through a food and the electrical resistance of the food causes the electric power to be transformed directly into heat. The heat is not delivered through a surface as in conventional heat exchangers but it is internally generated by Joule effect. Therefore, no temperature gradient is required and it origins quicker and more uniform heating within the food. On the other hand, it is associated with high energy costs and its use is limited to a particular range of food products with an appropriate electrical conductivity. Sterilization of foods by Ohmic heating has gained growing interest in the last few years. The aim of this study is to evaluate the benefits of Ohmic heating with respect to conventional heat exchangers under uniform wall temperature, a condition that is often present in industrial plants. This comparison is carried out by means of analytical models. The two different heating conditions are simulated under typical circumstances for the food industry. Particular attention is paid to the uniformity of the heat treatment and to the heating section length required in the two different conditions.
Directory of Open Access Journals (Sweden)
Hanoem EH
2011-09-01
Full Text Available Background: Indonesia has a variety of plants that can be used for medicines. One of the medicinal plants is Nigella sativa. Nigella sativa has been used for medicinal purposes, both as medicinal herb and as medicinal oil. It contains saponin and atsiri oils that have antifungal, antimicrobial and antibacterial effects. Nigella sativa has been suggested as denture cleansers since it can inhibit the growth of Candida albicans (C. albicans on heat cured acrylic resin. Purpose: The aim of this research is to know the effectiveness of Nigella sativa seed extract in inhibiting the growth of C. albicans on heat cured acrylic resin. Methods: Eighteen acrylic samples were divided into three groups. Group I was control group, only contaminated with C. albicans without immersing in any solution. Group II was acrylic sample immersed in sterile aquades for one hour. Group III was acrylic sample immersed in Nigella sativa seed extract for one hour. Results: There were significant differences of C. albicans (p < 0.05 among the three groups. The number of Candida albicans was significantly higher in Group I, while that in group II was lower than that in group I, and that in group III was the lowest. Conclusion: Nigella sativa seed extract was effective in inhibiting the growth of C. albicans on heat cured acrylic resin.Latar belakang: Indonesia memiliki berbagai tanaman yang dapat dipakai sebagai obat, salah satu tanaman tersebut adalah jinten hitam (Nigella sativa. Pada beberapa negara jinten hitam telah digunakan untuk berbagai tujuan, baik sebagai obat herbal maupun sebagai minyak. kandungan jinten hitam adalah saponin dan minyak atsiri yang mempunyai efek anti jamur dan anti mikroba. Jinten hitam disarankan sebagai pilihan pembersih gigi tiruan yang dapat menghambat pertumbuhan Candida albicans (C. albicans pada resin akrilik heat cured. Tujuan: Tujuan penelitian ini adalah mengetahui efektivitas dari ekstrak biji jinten hitam dalam menghambat pertumbuhan
Mathematical Model of Moving Heat-Transfer Agents
Directory of Open Access Journals (Sweden)
R. I. Yesman
2010-01-01
Full Text Available A mathematical model of moving heat-transfer agents which is applied in power systems and plants has been developed in the paper. A paper presents the mathematical model as a closed system of differential convective heat-transfer equations that includes a continuity equation, a motion equation, an energy equation.Various variants of boundary conditions on the surfaces of calculation flow and heat exchange zone are considered in the paper.
Numerical Modeling of Freezing and Melting Processes around a Borehole Heat Exchanger
Shao, Haibing; Zheng, Tianyuan; Nagel, Thomas; Kolditz, Olaf
2015-04-01
In ground sourced heat pump (GSHP) systems, heat energy stored in the shallow subsurface is extracted through borehole heat exchangers (BHE) and then utilized for domestic heating. In cold regions, the continuous heat deficit in the vicinity of the BHE can cause freezing of the surrounding soil. Its material properties, such as permeability and heat conductivity, will then significantly change and lead to a series of coupled thermal, hydraulic, and mechanical processes. In particular, the heat exchange performance of the BHE will be altered, and the frozen soil may also induce ground lift or subsidence in the vicinity of the building. As the first step of modelling this coupled system, we followed the approach proposed by Al-Khoury et al (2010) and Diersch et al (2011), where the BHE has been fully integrated into the numerical model in a dual-continuum way. Additionally, we extended the existing heat transport module in the numerical simulator OpenGeoSys to include the freezing and melting processes, whereas the ice volume fraction in the soil is non-linearly dependent on the temperature, and the soil properties were determined based on the degree of freezing/melting. The non-linearity of the coupled model was numerically solved by a Newton scheme. The extended model has been verified by comparing numerical results against analytical solutions and also findings from other numerical codes. Moreover, we proposed and simulated a hypothetical scenario, where ice is gradually forming around a BHE in response to the continuous operation of a heat pump. The model is capable of reproducing the thermodynamic freezing process as well as the heat transport affected by it. Future work will be focused on the integration of deformation processes into the model.
Heat source models in simulation of heat flow in friction stir welding
DEFF Research Database (Denmark)
Schmidt, Henrik Nikolaj Blich; Hattel, Jesper
2004-01-01
The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in friction stir welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms...... are implemented in FEMLAB and configured in terms of the heat source as: shoulder contribution only; shoulder and probe contribution, the latter as a volume heat source distributed in the probe volume; and shoulder and probe contribution distributed at the contact interface, i.e. as a surface flux in the case...
Numerical Simulation of Different Models of Heat Pipe Heat Exchanger Using AcuSolve
Directory of Open Access Journals (Sweden)
Zainal Nurul Amira
2017-01-01
Full Text Available In this paper, a numerical simulation of heat pipe heat exchanger (HPHE is computed by using CFD solver program i.e. AcuSolve. Two idealized model of HPHE are created with different variant of entry’s dimension set to be case 1 and case 2. The geometry of HPHE is designed in SolidWorks and imported to AcuSolve to simulate the fluid flow numerically. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in industry.
The porosity in a fluidized bed heat transfer model
Visser, G; Visser, G.; Valk, M.
1993-01-01
A mathematical model of heat transfer between a fluidized bed and an immersed surface and a model of gas flow and porosity, both recently published, were combined and further modified in the area of low velocities where the particle convective component of heat transfer is low or neglectable.
DEFF Research Database (Denmark)
Zvingilaite, Erika; Klinge Jacobsen, Henrik
2015-01-01
The trade-off between investing in energy savings and investing in individual heating technologies with high investment and low variable costs in single family houses is modelled for a number of building and consumer categories in Denmark. For each group the private economic cost of providing...... heating comfort is minimised. The private solution may deviate from the socio-economical optimal solution and we suggest changes to policy to incentivise the individuals to make choices more in line with the socio-economic optimal mix of energy savings and technologies. The households can combine...... to a combination of low costs of primary fuel and low environmental performance of woodstoves today, included health costs lead to decreased use of secondary heating. Overall the interdependence of heat generation technology- and heat saving-choice is significant. The total optimal level of heat savings...
Geochemical Modeling of ILAW Lysimeter Water Extracts
Energy Technology Data Exchange (ETDEWEB)
Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2014-12-22
Geochemical modeling results of water extracts from simulated immobilized low-activity waste (ILAW) glasses, placed in lysimeters for eight years suggest that the secondary phase reaction network developed using product consistency test (PCT) results at 90°C may need to be modified for field conditions. For sediment samples that had been collected from near the glass samples, the impact of glass corrosion could be readily observed based upon the pH of their water extracts. For unimpacted sediments the pH ranged from 7.88 to 8.11 with an average of 8.04. Sediments that had observable impacts from glass corrosion exhibited elevated pH values (as high as 9.97). For lysimeter sediment samples that appear to have been impacted by glass corrosion to the greatest extent, saturation indices determined for analcime, calcite, and chalcedony in the 1:1 water extracts were near equilibrium and were consistent with the secondary phase reaction network developed using PCT results at 90°C. Fe(OH)_{3}(s) also appears to be essentially at equilibrium in extracts impacted by glass corrosion, but with a solubility product (log K_{sp}) that is approximately 2.13 units lower than that used in the secondary phase reaction network developed using PCT results at 90°C. The solubilities of TiO_{2}(am) and ZrO_{2}(am) also appear to be much lower than that assumed in the secondary phase reaction network developed using PCT results at 90°C. The extent that the solubility of TiO_{2}(am) and ZrO_{2}(am) were reduced relative to that assumed in the secondary phase reaction network developed using PCT results at 90°C could not be quantified because the concentrations of Ti and Zr in the extracts were below the estimated quantification limit. Gibbsite was consistently highly oversaturated in the extract while dawsonite was at or near equilibrium. This suggests that dawsonite might be a more suitable phase for the secondary phase reaction network
Directory of Open Access Journals (Sweden)
Mariana-Atena Poiana
2012-07-01
Full Text Available This study was performed to investigate the effectiveness of grape seed extract (GSE compared to butylated hydroxytoluene (BHT on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV, p-anisidine value (p-AV, conjugated dienes and trienes (CD, CT, inhibition of oil oxidation (IO and TOTOX value. In addition, total phenolic content (TP was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%, p-AV (29%; 40%, CD (45%; 30%, CT (41%; 36%, TOTOX (35%; 37%. GSE to a level of 600–800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.
Poiana, Mariana-Atena
2012-01-01
This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600-800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.
Poiana, Mariana-Atena
2012-01-01
This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600–800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications. PMID:22942764
Modelling the Heat Consumption in District Heating Systems using a Grey-box approach
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg; Madsen, Henrik
2006-01-01
The heat consumption in a large geographical area is considered together with climate measurements on a single location in the area. The purpose is to identify a model linking the heat consumption to climate and calendar information. The process of building a model is split into a theoretical based...... identification of an overall model structure followed by data-based modelling, whereby the details of the model are identified. This approach is sometimes called grey-box modelling, but the specific approach used here does not require states to be specified. Overall, the paper demonstrates the power of the grey...
Modelling the heat dynamics of buildings using stochastic
DEFF Research Database (Denmark)
Andersen, Klaus Kaae; Madsen, Henrik
2000-01-01
This paper describes the continuous time modelling of the heat dynamics of a building. The considered building is a residential like test house divided into two test rooms with a water based central heating. Each test room is divided into thermal zones in order to describe both short and long term...... variations. Besides modelling the heat transfer between thermal zones, attention is put on modelling the heat input from radiators and solar radiation. The applied modelling procedure is based on collected building performance data and statistical methods. The statistical methods are used in parameter...... estimation and model validation, while physical knowledge is used in forming the model structure. The suggested lumped parameter model is thus based on thermodynamics and formulated as a system of stochastic differential equations. Due to the continuous time formulation the parameters of the model...
Karkhin, V. A.; Pittner, A.; Schwenk, C.; Rethmeier, M.
2011-06-01
The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat due to fusion and solidification. The parameters of the heat source models are unknown a priori and have to be evaluated by solving an inverse heat conduction problem. The functional-analytical technique for calculating 3D temperature fields in butt welding is developed. The proposed technique makes it possible to reduce considerably the total time for data input and solution. It is demonstrated with an example of laser beam welding of steel plates.
Rodgers, Corissa L; St Pierre, Kathryne A; Hall, Adam B
2014-07-01
Previous studies performed by our research group have suggested that zeolites are a suitable adsorbent for the recovery of oxygenates from fire debris through heated passive headspace extraction. Zeolite 13X, in particular, has been shown to be effective for recovering analytes with molecular diameters smaller than 10Å. The primary aim of this study was to evaluate the addition of zeolite 13X to heated headspace extraction for the recovery of ignitable liquids. Comparative recoveries of petroleum and alcohol-based ignitable liquid mixtures were studied utilizing activated charcoal strips and zeolites, individually and in tandem. In the presence of both adsorption media within the same sample can, activated charcoal strips recovered the majority of gasoline components, while zeolites recovered the majority of oxygenated compounds. This phenomenon was attributed to the size exclusion properties, polarity, and available surface area of zeolites. This research supports the use of zeolites with activated charcoal strips in a "dual-mode" preparation for casework in which the presence of an ignitable liquid is suspected. The described method allows for the recovery and concentration of ignitable liquid residues in a single extraction procedure, whether the ignitable liquid is petroleum-based or oxygenated in nature. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Simulation Models to Size and Retrofit District Heating Systems
Directory of Open Access Journals (Sweden)
Kevin Sartor
2017-12-01
Full Text Available District heating networks are considered as convenient systems to supply heat to consumers while reducing CO 2 emissions and increasing renewable energies use. However, to make them as profitable as possible, they have to be developed, operated and sized carefully. In order to cope with these objectives, simulation tools are required to analyze several configuration schemes and control methods. Indeed, the most common problems are heat losses, the electric pump consumption and the peak heat demand while ensuring the comfort of the users. In this contribution, a dynamic simulation model of all the components of the network is described. It is dedicated to assess some energetic, environmental and economic indicators. Finally, the methodology is used on an existing application test case namely the district heating network of the University of Liège to study the pump control and minimize the district heating network heat losses.
Modeling of surge characteristics in turbo heat pumps
Energy Technology Data Exchange (ETDEWEB)
Kim, Hye Rim; Song, Seung Jin [Seoul National University, Seoul (Korea, Republic of); Kim, Kil Young [LS Mtron Co., Ltd., Anyang (Korea, Republic of)
2009-07-01
The study shows the theoretical analysis of surge dynamics in a turbo heat pump. The one-dimensional nonlinear model is developed. This is similar to the previous researches on unsteady analysis in simple compression system. But it is more complicated because the fluids in heat pumps undergo phase changes in heat exchangers and form closed-loop systems. So the two-phase flow effect and feedback effect from evaporator outlet to compressor inlet should be considered. The external conditions such as heat flux from cooling and chilled water are also important. Numerical results are presented to show the surge behavior in a turbo heat pump. It show that there are important parameters which determine the surge characteristics including Greitzer's B parameter and the other related to heat transfer in heat exchangers.
Directory of Open Access Journals (Sweden)
James A. Parsons
2001-01-01
Full Text Available The effect of channel rotation on jet impingement cooling by arrays of circular jets in twin channels was studied. Impinging jet flows were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. The jets impinged normally on the smooth, heated target wall in each channel. The spent air exited the channels through extraction holes in each target wall, which eliminates cross flow on other jets. Jet rotation numbers and jet Reynolds numbers varied from 0.0 to 0.0028 and 5000 to 10,000, respectively. For the target walls with jet flow in the direction of rotation (or opposite to the direction of rotation, as rotation number increases heat transfer decreases up to 25% (or 15% as compared to corresponding results for non-rotating conditions. This is due to the changes in flow distribution and rotation induced Coriolis and centrifugal forces.
Quantum heat engine: A fully quantized model
Youssef, M.; Mahler, G.; Obada, A.-S. F.
2010-01-01
Motivated by the growing interest in the nanophysics and the field of quantum thermodynamics [J. Gemmer, M. Michel, G. Mahler, Springer, 2005] we study a system consisting of two different 2-level atoms (spins) coupled to a quantum oscillator (resonator field mode), and each spin linked to a heat bath with different temperatures. We find that the energy gradient imposed on the system and the “coherent driving” of the two atoms achieved by the oscillator make this system act as a thermodynamic machine. We analyze the engine dynamics using the recently developed definitions of heat flux and power [E. Boukobza, D.J. Tannor, Phys. Rev. A. 74 (2006) 063823; H. Weimer, M.J. Henrich, F. Rempp, H. Schröder, G. Mahler, Eur. Phys. Lett. 83 (3) (2008) 30008]. The system can work as heat engine (laser) or a heat pump in a non-cyclic continuous mode. We characterize the properties of the resonator field. The concept of work and heat for this machine is discussed.
Model-based control of district heating supply temperature
Energy Technology Data Exchange (ETDEWEB)
Saarinen, Linn
2010-11-15
A model-based control strategy for the supply temperature to a district heating network was tested during three weeks at Idbaecken's CHP plant. The aim was to increase the electricity efficiency by a lower supply temperature, without risking the delivery reliability of heat to the district heating customers. Simulations and tests showed that at high loads, the mean supply temperature could be reduced by 4 deg C and the electricity production could be increased by 2.5%
Thermal Models for Intelligent Heating of Buildings
DEFF Research Database (Denmark)
Thavlov, Anders; Bindner, Henrik W.
2012-01-01
The Danish government has set the ambitious goal that the share of the total Danish electricity consumption, covered by wind energy, should be increased to 50% by year 2020. This asks for radical changes in how we utilize and transmit electricity in the future power grid. To fully utilize the high...... share of renewable power generation, which is in general intermittent and non-controllable, the consumption side has to be much more flexible than today. To achieve such flexibility, methods for moving power consumption in time, within the hourly timescale, have to be developed. One approach currently...... being pursued is to use the heat capacity of the thermal mass in buildings to temporarily store excess power production by increasing the electrical heating. Likewise can the electrical heating be postponed in periods with lack of production. To exploit the potential in thermal storage and to ensure...
Blotting Assisted by Heating and Solvent Extraction for DESI-MS Imaging
Cabral, Elaine C.; Mirabelli, Mario F.; Perez, Consuelo J.; Ifa, Demian R.
2013-06-01
Imprints of potato sprout ( Solanum tuberosum L.), gingko leaves (Gingko biloba L. ) and strawberries (Fragaria x ananassa Duch. ) were successfully imaged by desorption electrospray ionization mass spectrometry (DESI-MS) on TLC plates through blotting assisted by heating and/or solvent extraction. Ion images showing the distribution of significant compounds such as glycoalkaloid toxins in potato sprout, ginkgolic acids and flavonoids in ginkgo leaves, and sugars and anthocyanidin in strawberry were obtained. Practical implications of this work include analysis of a wide range of irregular or soft materials by different imprinting conditions without requiring the addition of matrices or use of specific kinds of surfaces.
Kinetic Modelling of Oil Extraction from Neem Seed | Ogunleye ...
African Journals Online (AJOL)
The suitability of three different types of extraction kinetic models (one- step, two –step and three – step models) for neem oil was investigated in this study. Solvent extraction using n-hexane at temperatures range between 303K and 323 K ; 360minutes of extraction time were experimented and the oil yield calculated.
Lescano, Caroline Honaiser; de Oliveira, Ivan Pires; Zaminelli, Tiago; Baldivia, Débora da Silva; da Silva, Luan Ramos; Napolitano, Mauro; Silvério, Camila Bitencourt Mendes; Lincopan, Nilton; Sanjinez-Argandoña, Eliana Janet
2016-01-01
Campomanesia adamantium (Myrtaceae) is a medicinal plant distributed in Brazilian Cerrado. Different parts of this plant are used in popular medicine for treatment of several diseases like fever, diarrhea, hypercholesterolemia and rheumatism. The aim of this work was to evaluate the inhibition of heat-stable enterotoxin type A (STa) by gallic acid present in the peel of C. adamantium fruit and assays to assess the antidiarrheal activity, anti-inflammatory and cytotoxic properties of peel extract using the T84 cell line model. The possible inhibition exerted by the gallic acid of the peel extract on the STa peptide was inferred by molecular dynamics simulations. The antidiarrheal effects were investigated measuring cGMP accumulation in cells after stimulation by STa toxin and antibacterial activity was assessed. The anti-inflammatory activity was assessed by inhibition of COX-1 and COX-2. MTT and LDH assays were used to evaluate any possible cytotoxic action while the CyQUANT test was used to investigate the effect on cell proliferation. A representation showing how the possible interactions between STa and the gallic acid of the extract might reduce the action of the enterotoxin is presented. C. adamantium peel extract significantly decreased the levels of cGMP in T84 cells. However, no effect on the species of microorganisms was observed. The extract also inhibited COX-1 (IC50 255.70 ± 0.04 ng/mL) and COX-2 (IC50 569.50 ± 0.11 ng/mL) enzymes. Cytotoxicity assay have shown significant changes in cells treated with the extract, which inhibited the cell proliferation until 72 hours of treatment. Direct interactions of phenolic compounds present in the extract with the STa toxin may limit its activity. Curative effect in the diarrhea treatment and its anti-inflammatory action is based on the pharmacological properties, mechanism of action of the C. adamantium peel extract, and no toxic effects of the peel extract presented on this work.
Lescano, Caroline Honaiser; de Oliveira, Ivan Pires; Zaminelli, Tiago; Baldivia, Débora da Silva; da Silva, Luan Ramos; Napolitano, Mauro; Silvério, Camila Bitencourt Mendes; Lincopan, Nilton; Sanjinez-Argandoña, Eliana Janet
2016-01-01
Campomanesia adamantium (Myrtaceae) is a medicinal plant distributed in Brazilian Cerrado. Different parts of this plant are used in popular medicine for treatment of several diseases like fever, diarrhea, hypercholesterolemia and rheumatism. The aim of this work was to evaluate the inhibition of heat-stable enterotoxin type A (STa) by gallic acid present in the peel of C. adamantium fruit and assays to assess the antidiarrheal activity, anti-inflammatory and cytotoxic properties of peel extract using the T84 cell line model. The possible inhibition exerted by the gallic acid of the peel extract on the STa peptide was inferred by molecular dynamics simulations. The antidiarrheal effects were investigated measuring cGMP accumulation in cells after stimulation by STa toxin and antibacterial activity was assessed. The anti-inflammatory activity was assessed by inhibition of COX-1 and COX-2. MTT and LDH assays were used to evaluate any possible cytotoxic action while the CyQUANT test was used to investigate the effect on cell proliferation. A representation showing how the possible interactions between STa and the gallic acid of the extract might reduce the action of the enterotoxin is presented. C. adamantium peel extract significantly decreased the levels of cGMP in T84 cells. However, no effect on the species of microorganisms was observed. The extract also inhibited COX-1 (IC50 255.70 ± 0.04 ng/mL) and COX-2 (IC50 569.50 ± 0.11 ng/mL) enzymes. Cytotoxicity assay have shown significant changes in cells treated with the extract, which inhibited the cell proliferation until 72 hours of treatment. Direct interactions of phenolic compounds present in the extract with the STa toxin may limit its activity. Curative effect in the diarrhea treatment and its anti-inflammatory action is based on the pharmacological properties, mechanism of action of the C. adamantium peel extract, and no toxic effects of the peel extract presented on this work. PMID:27764241
Energy Technology Data Exchange (ETDEWEB)
Berna, C.; Escriva, A.; Munuz-Cobo, J. L.; Romero, A.
2012-07-01
This paper made the simulation of the PKL III G1.1 experiment using SNAP interface and the TRACE code. This experiment aims to essentially the study of the extraction of the residual heat of the steam generator in the presence of gases incondensables.
Directory of Open Access Journals (Sweden)
Sugito
2015-09-01
Full Text Available Quality of eggs might decrease when hens under heat stress. A further study found that a specific plant extracts could reduce the impacts of heat stress. The aim of this study was to determine effects of Salix tetrasperma plant extract in combination with extract of turmeric and neem to improve egg quality and productivity of laying hens under heat stress. Sixty laying hens strain Isa Brown of 6 months old were used and reared in individual cages. The feed and drinking water were supplied ad libitum. This study was conducted in a completely randomized design with five treatments (two controls and three treatments and each treatment consisted of 12 replication. Treatment consisted of with (KP and without (KP commercial anti-stress supplement. Formulations of extract were S. tetrasperma 1.000 mg / l water (EJ, S. tetrasperma 1.000 mg / l + Turmeric 250 mg / l + neem 250 mg / l (EJ+K1, and S. tetrasperma 1.000 mg / l + Turmeric 500 mg / l + neem 500 mg / l drinking water (EJ+K2. The hens were exposed to heat stress for 5 hours per day at a temperature range of 34.0±1.0°C. Supplements were dissolved in drinking water and were given for 30 days in the morning and noon. Results showed that a single extract of S. tetrasperma or the combination of an extract of turmeric and neem were significantly increased thickness of eggshell (P<0.05, but did not affect color of egg yolk, height albumin, egg weight, and HU value. Extract of S. tetrasperma combined with turmeric and neem extract dissolved in drinking water for 30 days in laying hens reared under heat stress could not improved quality of the eggs, but may increase thickness of the egg shell and cause decreased water consumption.
Alberice, Juliana Vieira; Funes-Huacca, Maribel Elizabeth; Guterres, Sheila Barreto; Carrilho, Emanuel
2012-10-01
Alicyclobacillus acidoterrestris is a spoilage-causing bacterium in fruit juices. The inactivation of this bacterium by commercial saponin and saponin purified extract from Sapindus saponaria fruits combined with heat-treatment is described. We investigated heat treatment (87, 90, 95, and 99°C) with incubation time ranging from 0 to 50min, in both concentrated and reconstituted juice. Juices were inoculated with 1.0×10(4)CFU/mL of A. acidoterrestris spores for the evaluation of the best temperature for inactivation. For the temperatures of 87, 90, and 95°C counts of cell viability decreased rapidly within the first 10 to 20min of incubation in both concentrated and reconstituted juices; inactivation at 99°C ensued within 1 and 2min. Combination of commercial saponin (100mg/L) with a very short incubation time (1min) at 99°C showed a reduction of 2.34 log cycle for concentrated juice A. acidoterrestris spores (1.0×10(4)CFU/mL) in the first 24h of incubation after treatments. The most efficient treatment was reached with 300, 400 or 500mg/L of purified extract of saponins from S. saponaria after 5days of incubation in concentrated juice, and after 5days with 300 and 400mg/L or 72h with 500mg/L in reconstituted juice. Commercial saponin and purified extracts from S. saponaria had similar inactivation power on A. acidoterrestris spores, without significant differences (P>0.05). Therefore, purified extract of saponins can be an alternative for the control of A. acidoterrestris in fruit juices. Copyright © 2012 Elsevier B.V. All rights reserved.
Longo, Cristiano; Leo, Lucia; Leone, Antonella
2012-01-01
The risk of chronic diseases has been shown to be inversely related to tomato intake and the lycopene levels in serum and tissue. Cis-isomers represent approximately 50%–80% of serum lycopene, while dietary lycopene maintains the isomeric ratio present in the plant sources with about 95% of all-trans-lycopene. Supercritical CO2 extraction (S-CO2) has been extensively developed to extract lycopene from tomato and tomato processing wastes, for food or pharmaceutical industries, also by using additional plant sources as co-matrices. We compared two S-CO2-extracted oleoresins (from tomato and tomato/hazelnut matrices), which showed an oil-solid bi-phasic appearance, a higher cis-lycopene content, and enhanced antioxidant ability compared with the traditional solvent extracts. Heat-treating, in the range of 60–100 °C, led to changes in the lycopene isomeric composition and to enhanced antioxidant activity in both types of oleoresins. The greater stability has been related to peculiar lycopene isomer composition and to the lipid environment. The results indicate these oleoresins are a good source of potentially healthful lycopene. PMID:22605975
Dynamic modeling of an air source heat pump water heater
Fardoun, Farouk; Ibrahim, Oussama; Zoughaib, Assaad
2011-01-01
International audience; This paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out usi...
Energy Technology Data Exchange (ETDEWEB)
Hedegaard, K.
2013-09-15
This PhD investigates to which extent heat pumps, heat storages, and electric vehicles can support the integration of wind power. Considering the gaps in existing research, the main focus is put on individual heat pumps in the residential sector (one-family houses) and the possibilities for flexible operation, using the heat storage options available. Several energy systems analyses are performed using the energy system models, Balmorel, developed at the former TSO, ElkraftSystem, and, EnergyPLAN, developed at Aalborg University. The Danish energy system towards 2030, with wind power penetrations of up to 60 %, is used as a case study in most of the analyses. Both models have been developed further, resulting in an improved representation of individual heat pumps and heat storages. An extensive model add-on for Balmorel renders it possible to optimise investment and operation of individual heat pumps and different types of heat storages, in integration with the energy system. Total costs of the energy system are minimised in the optimisation. The add-on incorporates thermal building dynamics and covers various different heat storage options: intelligent heat storage in the building structure for houses with radiator heating and floor heating, respectively, heat accumulation tanks on the space heating circuit, as well as hot water tanks. In EnergyPLAN, some of the heat storage options have been modelled in a technical optimisation that minimises fuel consumption of the energy system and utilises as much wind power as possible. The energy systems analyses reveal that in terms of supporting wind power integration, the installation of individual heat pumps is an important step, while adding heat storages to the heat pumps is less influential. When equipping the heat pumps with heat storages, only moderate system benefits can be gained. Hereof, the main system benefit is that the need for peak/reserve capacity investments can be reduced through peak load shaving; in
Nanoflare heating model for collisionless solar corona
Indian Academy of Sciences (India)
2017-01-31
Jan 31, 2017 ... Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place.
Nanoflare heating model for collisionless solar corona
Indian Academy of Sciences (India)
Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place. The present ...
Stochastic modelling of central heating systems
DEFF Research Database (Denmark)
Hansen, Lars Henrik
1997-01-01
and the degree Erhvervsforsker (a special Danish degree, equivalent to ``Industrial Ph.D.''). The thesis is mainly concerned with experimental design and system identification for individual components in water based central heating systems. The main contribution to this field is on the nonlinear dynamic...
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Induction and direct resistance heating theory and numerical modeling
Lupi, Sergio; Aliferov, Aleksandr
2015-01-01
This book offers broad, detailed coverage of theoretical developments in induction and direct resistance heating and presents new material on the solution of problems in the application of such heating. The physical basis of induction and conduction heating processes is explained, and electromagnetic phenomena in direct resistance and induction heating of flat workpieces and cylindrical bodies are examined in depth. The calculation of electrical and energetic characteristics of induction and conduction heating systems is then thoroughly reviewed. The final two chapters consider analytical solutions and numerical modeling of problems in the application of induction and direct resistance heating, providing industrial engineers with the knowledge needed in order to use numerical tools in the modern design of installations. Other engineers, scientists, and technologists will find the book to be an invaluable reference that will assist in the efficient utilization of electrical energy.
An Analytical Model of Joule Heating in Piezoresistive Microcantilevers
Directory of Open Access Journals (Sweden)
Chongdu Cho
2010-11-01
Full Text Available The present study investigates Joule heating in piezoresistive microcantilever sensors. Joule heating and thermal deflections are a major source of noise in such sensors. This work uses analytical and numerical techniques to characterise the Joule heating in 4-layer piezoresistive microcantilevers made of silicon and silicon dioxide substrates but with the same U-shaped silicon piezoresistor. A theoretical model for predicting the temperature generated due to Joule heating is developed. The commercial finite element software ANSYS Multiphysics was used to study the effect of electrical potential on temperature and deflection produced in the cantilevers. The effect of piezoresistor width on Joule heating is also studied. Results show that Joule heating strongly depends on the applied potential and width of piezoresistor and that a silicon substrate cantilever has better thermal characteristics than a silicon dioxide cantilever.
Microscale Heat Conduction Models and Doppler Feedback
Energy Technology Data Exchange (ETDEWEB)
Hawari, Ayman I. [North Carolina State Univ., Raleigh, NC (United States); Ougouag, Abderrafi [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-01-22
The objective of this project is to establish an approach for providing the fundamental input that is needed to estimate the magnitude and time-dependence of the Doppler feedback mechanism in Very High Temperature reactors. This mechanism is the foremost contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic (TRISO) coated particles. Therefore, its correct prediction is essential to the conduct of safety analyses for these reactors. Since the effect is directly dependent on the actual temperature reached by the fuel during transients, the underlying phenomena of heat deposition, heat transfer and temperature rise must be correctly predicted. To achieve the above objective, this project will explore an approach that accounts for lattice effects as well as local temperature variations and the correct definition of temperature and related local effects.
Optimization of heat saving in buildings using unsteady heat transfer model
Directory of Open Access Journals (Sweden)
Dedinec Aleksandra
2015-01-01
Full Text Available Reducing the energy consumption growth rate is increasingly becoming one of the main challenges for ensuring sustainable development, particularly in the buildings as the largest end-use sector in many countries. Along this line, the aim of this paper is to analyse the possibilities for energy savings in the construction of new buildings and reconstruction of the existing ones developing a tool that, in terms of the available heating technologies and insulation, provides answer to the problem of optimal cost effective energy consumption. The tool is composed of an unsteady heat transfer model which is incorporated into a cost-effective energy saving optimization. The unsteady heat transfer model uses annual hourly meteorological data, chosen as typical for the last ten-year period, as well as thermo physical features of the layers of the building walls. The model is tested for the typical conditions in the city of Skopje, Macedonia. The results show that the most cost effective heating technology for the given conditions is the wood fired stove, followed by the inverter air-conditioner. The centralized district heating and the pellet fired stoves are the next options. The least cost effective option is the panel that uses electricity. In this paper, the optimal insulation thickness is presented for each type of heating technology.
Two-phase plate-fin heat exchanger modeling for waste heat recovery systems in diesel engines
Feru, E.; de Jager, B.; Willems, F.; Steinbuch, M.
2014-01-01
This paper presents the modeling and model validation for a modular two-phase heat exchanger that recovers energy in heavy-duty diesel engines. The model is developed for temperature and vapor quality prediction and for control design of the waste heat recovery system. In the studied waste heat
Directory of Open Access Journals (Sweden)
Nee Alexander
2015-01-01
Full Text Available Mathematical modeling of radiant heating of a closed rectangular area under conditions of convective heat transfer at the external boundaries is passed. The fields of temperature and stream function, illustrating the unsteady nature of the heat transfer were obtained. The extent influence of convective heat transfer at the external boundaries on the circulating flows formation in the gas cavity are shown.
Modelling of heating and evaporation of n-Heptane droplets
DEFF Research Database (Denmark)
Yin, Chungen
2015-01-01
and azimuthal directions, respectively, on each of which the flow, heat and mass transfer are numerically solved using the finite volume method. During the transient heating and evaporation process, the interaction between the moving droplets and free-stream flow are properly considered. Droplet dynamics......-oil droplets are two key tasks. This paper presents an effort towards a generic model that is beneficial to both the tasks. A computer code for droplet heating and evaporation is developed in a generic 3D model framework. The droplets are discretized into a number of control volumes along the radial, polar...... and size are also updated accordingly. The model is validated by analytical solutions to simplified cases and also by experimental data on heating and evaporation of n-Heptane droplets available in literature. Finally, the routines to extend the validated model for the two tasks of the project...
Modelling of elastic heat conductors via objective rate equations
Morro, Angelo
2018-01-01
A thermoelastic solid is modelled by letting the heat flux be given by a rate equation. As any constitutive property, the rate equation has to be objective and consistent with thermodynamics. Accordingly, firstly a theorem is given that characterizes objective time derivatives. This allows the known objective time derivatives to be viewed as particular elements of the set so specified. Next the thermodynamic consistency is established for the constitutive models involving objective time derivatives within appropriate sets. It emerges that the thermodynamic consistency holds provided the stress contains additively terms quadratic in the heat flux vector in a form that is related to the derivative adopted for the rate of the heat flux.
Model-based analysis and simulation of regenerative heat wheel
DEFF Research Database (Denmark)
Wu, Zhuang; Melnik, Roderick V. N.; Borup, F.
2006-01-01
The rotary regenerator (also called the heat wheel) is an important component of energy intensive sectors, which is used in many heat recovery systems. In this paper, a model-based analysis of a rotary regenerator is carried out with a major emphasis given to the development and implementation...... of mathematical models for the thermal analysis of the fluid and wheel matrix. The effect of heat conduction in the direction of the fluid flow is taken into account and the influence of variations in rotating speed of the wheel as well as other characteristics (ambient temperature, airflow and geometric size...
Numerical Modeling of Fin and Tube Heat Exchanger for Waste Heat Recovery
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study...
MODELING OF TEMPERATURE FIELDS IN A SOLID HEAT ACCUMULLATORS
Directory of Open Access Journals (Sweden)
S. S. Belimenko
2016-10-01
Full Text Available Purpose. Currently, one of the priorities of energy conservation is a cost savings for heating in commercial and residential buildings by the stored thermal energy during the night and its return in the daytime. Economic effect is achieved due to the difference in tariffs for the cost of electricity in the daytime and at night. One of the most common types of devices that allow accumulating and giving the resulting heat are solid heat accumulators. The main purpose of the work: 1 software development for the calculation of the temperature field of a flat solid heat accumulator, working due to the heat energy accumulation in the volume of thermal storage material without phase transition; 2 determination the temperature distribution in its volumes at convective heat transfer. Methodology. To achieve the study objectives a heat transfer theory and Laplace integral transform were used. On its base the problems of determining the temperature fields in the channels of heat accumulators, having different cross-sectional shapes were solved. Findings. Authors have developed the method of calculation and obtained solutions for the determination of temperature fields in channels of the solid heat accumulator in conditions of convective heat transfer. Temperature fields over length and thickness of channels were investigated. Experimental studies on physical models and industrial equipment were conducted. Originality. For the first time the technique of calculating the temperature field in the channels of different cross-section for the solid heat accumulator in the charging and discharging modes was proposed. The calculation results are confirmed by experimental research. Practical value. The proposed technique is used in the design of solid heat accumulators of different power as well as full-scale production of them was organized.
Modeling transient heat transfer in nuclear waste repositories.
Yang, Shaw-Yang; Yeh, Hund-Der
2009-09-30
The heat of high-level nuclear waste may be generated and released from a canister at final disposal sites. The waste heat may affect the engineering properties of waste canisters, buffers, and backfill material in the emplacement tunnel and the host rock. This study addresses the problem of the heat generated from the waste canister and analyzes the heat distribution between the buffer and the host rock, which is considered as a radial two-layer heat flux problem. A conceptual model is first constructed for the heat conduction in a nuclear waste repository and then mathematical equations are formulated for modeling heat flow distribution at repository sites. The Laplace transforms are employed to develop a solution for the temperature distributions in the buffer and the host rock in the Laplace domain, which is numerically inverted to the time-domain solution using the modified Crump method. The transient temperature distributions for both the single- and multi-borehole cases are simulated in the hypothetical geological repositories of nuclear waste. The results show that the temperature distributions in the thermal field are significantly affected by the decay heat of the waste canister, the thermal properties of the buffer and the host rock, the disposal spacing, and the thickness of the host rock at a nuclear waste repository.
Modeling heat loss from the udder of a dairy cow.
Gebremedhin, Kifle G; Wu, Binxin
2016-07-01
A mechanistic model that predicts sensible and latent heat fluxes from the udder of a dairy cow was developed. The prediction of the model was spot validated against measured data from the literature, and the result agreed within 7% of the measured value for the same ambient temperature. A dairy cow can lose a significant amount of heat (388W/m(2)) from the udder. This suggests that the udder could be considered as a heat sink. The temperature profile through the udder tissue (core to skin) approached the core temperature for an air temperature ≥37°C whereas the profile decreased linearly from the core to skin surface for an air temperature less than 37°C. Sensible heat loss was dominant when ambient air temperature was less than 37.5°C but latent heat loss was greater than sensible heat loss when air temperature was ≥37.5°C. The udder could lose a total (sensible + latent) heat flux of 338W/m(2) at an ambient temperature of 35°C and blood-flow rate of 3.2×10(-3)m(3)/(sm(3) tissue). The results of this study suggests that, in time of heat stress, a dairy cow could be cooled by cooling the udder only (e.g., using an evaporative cooling jacket). Copyright © 2016 Elsevier Ltd. All rights reserved.
Down-Hole Heat Exchangers: Modelling of a Low-Enthalpy Geothermal System for District Heating
Directory of Open Access Journals (Sweden)
M. Carlini
2012-01-01
Full Text Available In order to face the growing energy demands, renewable energy sources can provide an alternative to fossil fuels. Thus, low-enthalpy geothermal plants may play a fundamental role in those areas—such as the Province of Viterbo—where shallow groundwater basins occur and conventional geothermal plants cannot be developed. This may lead to being fuelled by locally available sources. The aim of the present paper is to exploit the heat coming from a low-enthalpy geothermal system. The experimental plant consists in a down-hole heat exchanger for civil purposes and can supply thermal needs by district heating. An implementation in MATLAB environment is provided in order to develop a mathematical model. As a consequence, the amount of withdrawable heat can be successfully calculated.
Modeling of Radiative Heat Transfer in an Electric Arc Furnace
Opitz, Florian; Treffinger, Peter; Wöllenstein, Jürgen
2017-12-01
Radiation is an important means of heat transfer inside an electric arc furnace (EAF). To gain insight into the complex processes of heat transfer inside the EAF vessel, not only radiation from the surfaces but also emission and absorption of the gas phase and the dust cloud need to be considered. Furthermore, the radiative heat exchange depends on the geometrical configuration which is continuously changing throughout the process. The present paper introduces a system model of the EAF which takes into account the radiative heat transfer between the surfaces and the participating medium. This is attained by the development of a simplified geometrical model, the use of a weighted-sum-of-gray-gases model, and a simplified consideration of dust radiation. The simulation results were compared with the data of real EAF plants available in literature.
Fractional Heat Conduction Models and Thermal Diffusivity Determination
Directory of Open Access Journals (Sweden)
Monika Žecová
2015-01-01
Full Text Available The contribution deals with the fractional heat conduction models and their use for determining thermal diffusivity. A brief historical overview of the authors who have dealt with the heat conduction equation is described in the introduction of the paper. The one-dimensional heat conduction models with using integer- and fractional-order derivatives are listed. Analytical and numerical methods of solution of the heat conduction models with using integer- and fractional-order derivatives are described. Individual methods have been implemented in MATLAB and the examples of simulations are listed. The proposal and experimental verification of the methods for determining thermal diffusivity using half-order derivative of temperature by time are listed at the conclusion of the paper.
William Massman
2015-01-01
Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMVmodel, a 1-D (one-dimensional) non-equilibrium (liquid- vapor phase change)...
Energy Technology Data Exchange (ETDEWEB)
Hurtig, E.; Groswig, S.; Kasch, M. [GESO GmbH, Jena (Germany)
1997-12-01
The relations between the thermal processes around a 200 m deep geothermal well and the petrographic composition were studied using the fibre optic temperature sensing method. The heat injection and heat extraction properties depend on the petrographic properties (porosity, permeability) of the individual layers. Coarse sandy, water saturated layers have good properties, silts and clays have poor properties for het storage and heat extraction. Heat transport occurs in well defined layers with good hydraulic properties and can be explained by a convective heat transport model. (orig.) [Deutsch] Mit faseroptischen Temperaturmessungen in einer Erdwaermesonde (EWS)-Bohrung wurde der Zusammenhang zwischen den thermischen Prozessen unmittelbar um die EWS und dem petrographischen Aufbau untersucht. Das Waermeein- bzw. -ausspeisevermoegen haengt von der petrographischen Ausbildung der einzelnen Schichten ab (Porositaet, Kf-Wert). Grobsandige bis kiesige, wassergesaettigte Schichten haben guenstige, schluffig-tonige unguenstige Eigenschaften fuer die Waermeaus- bzw. -einspeisung. Der wesentliche Waermetransport erfolgt in definierten geringmaechtigen Schichten mit guten hydraulischen Eigenschaften. Der Waermetransport in poroesen, wassergefuellten Schichten kann mit einem konvektiven Waermetransportmodell erklaert werden. (orig.)
EnergyPlus Air Source Integrated Heat Pump Model
Energy Technology Data Exchange (ETDEWEB)
Shen, Bo [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Science Division; Adams, Mark B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Science Division; New, Joshua Ryan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy and Transportation Science Division
2016-03-30
This report summarizes the development of the EnergyPlus air-source integrated heat pump model. It introduces its physics, sub-models, working modes, and control logic. In addition, inputs and outputs of the new model are described, and input data file (IDF) examples are given.
Analytic model of heat deposition in spallation neutron target
Findlay, D. J. S.
2015-12-01
A simple analytic model for estimating deposition of heat in a spallation neutron target is presented-a model that can readily be realised in an unambitious spreadsheet. The model is based on simple representations of the principal underlying physical processes, and is intended largely as a 'sanity check' on results from Monte Carlo codes such as FLUKA or MCNPX.
A model for the spontaneous heating of coal
Energy Technology Data Exchange (ETDEWEB)
Schmal, D.; Duyzer, J.H.; van Heuven, J.W.
1984-01-01
As part of an investigation into the spontaneous heating of coal piles, a one-dimensional model describing the spontaneous heating process at relatively low temperatures has been developed. The model aims at establishing a relation between laboratory measurements on coal and the behavior of coal piles. In addition the model should be useful in establishing those physical and chemical factors that play an important role in the heating of coal piles in order to take rational measures against excessive losses in caloric value. The ultimate non-steady model takes into account the depletion of oxygen and the production of heat by chemisorption of oxygen in the coal, the transport of oxygen via diffusion and convection and the transport of heat via conduction, convection and evaporation/condensation of coal moisture. It consists of four differential equations, namely equations for conservation of oxygen mass, of coal moisture and of heat and a reaction-rate equation of oxygen with coal. For some simple cases, the equations were solved analytically. For non-steady conditions, they were solved numerically. Calculations using data from laboratory and field experiments give results that describe the process of spontaneous heating in a semi-quantitative sense as it appeared from a comparison between the results of calculations and those of measurements in coal piles. The most important parameters in the process of spontaneous heating particularly for the time between dumping and spontaneous ignition are the porosity of the pile, the initial temperature of the coal and the evaporation and condensation of coal moisture. The influence of other parameters (e.g. reactivity of the coal, heat conductivity, etc.) is much less pronounced.
Numerical Modeling of Electroacoustic Logging Including Joule Heating
Plyushchenkov, Boris D.; Nikitin, Anatoly A.; Turchaninov, Victor I.
It is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows to take influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modeling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electroacoustic logging and at the interpretation of its log data.
Liu, Jiawei; Zhou, Xingqiu; Wu, Jiangdong; Gao, Wen; Qian, Xu
2017-10-01
The temperature is the essential factor that influences the efficiency of anaerobic reactors. During the operation of the anaerobic reactor, the fluctuations of ambient temperature can cause a change in the internal temperature of the reactor. Therefore, insulation and heating measures are often used to maintain anaerobic reactor's internal temperature. In this paper, a simplified heat transfer model was developed to study heat transfer between cylindrical anaerobic reactors and their surroundings. Three cylindrical reactors of different sizes were studied, and the internal relations between ambient temperature, thickness of insulation, and temperature fluctuations of the reactors were obtained at different reactor sizes. The model was calibrated by a sensitivity analysis, and the calibrated model was well able to predict reactor temperature. The Nash-Sutcliffe model efficiency coefficient was used to assess the predictive power of heat transfer models. The Nash coefficients of the three reactors were 0.76, 0.60, and 0.45, respectively. The model can provide reference for the thermal insulation design of cylindrical anaerobic reactors.
A SIMPLE EXPERIMENTAL MODEL OF HEAT SHOCK RESPONSE IN RATS
Directory of Open Access Journals (Sweden)
Tufi Neder Meyer
1998-10-01
Full Text Available Objective: To obtain a simple model for the elicitation of the heat shock response in rats. Design: Laboratory study. Setting: University research laboratories. Sample: Seventy-nine adult male albino rats (weight range 200 g to 570 g. Procedures: Exposure to heat stress by heating animals in a warm bath for 5 min after their rectal temperatures reached 107.60 F (420 C. Liver and lung samples were collected for heat-shock protein 70 (HSP70 detection (Western analysis. Results: Western analysis was positive for HSP70 in the liver and in the lungs of heated animals. There was a temporal correlation between heating and HSP70 detection: it was strongest 1 day after heating and reduced afterwards. No heated animals died. Conclusion: These data show that heating rats in a warm (45o C bath, according to parameters set in this model, elicits efficiently the heat shock response.OBJETIVO: Obter um modelo simples para tentar esclarecer a resposta ao choque térmico em ratos. LOCAL: Laboratório de pesquisa da Universidade. MÉTODO: Amostra: 79 ratos albinos, adultos, entre 200g a 570g. Procedimentos: Exposição ao calor, em banho quente, por 5 minutos, após a temperatura retal chegar a 42 graus centigrados. Biópsias de fígado e pulmão foram obtidas para detectar a proteina 70 (HSP 70, pelo "Western blot". RESULTADOS: As análises foram positivas nos animais aquecidos, com uma correlação entre aquecimento e constatação da HSP 70. Foi mais elevada no primeiro dia e não houve óbitos nos animais aquecidos. CONCLUSÃO: Os ratos aquecidos a 45 graus centígrados respondem eficientemente ao choque térmico.
On the Einstein-Stern model of rotational heat capacities
DEFF Research Database (Denmark)
Dahl, Jens Peder
1998-01-01
The Einstein-Stern model for the rotational contribution to the heat capacity of a diatomic gas has recently been resuscitated. In this communication, we show that the apparent success of the model is illusory, because it is based on what has turned out to be an unfortunate comparison with experi......The Einstein-Stern model for the rotational contribution to the heat capacity of a diatomic gas has recently been resuscitated. In this communication, we show that the apparent success of the model is illusory, because it is based on what has turned out to be an unfortunate comparison...
Modelling of boiler heating surfaces and evaporator circuits
DEFF Research Database (Denmark)
Sørensen, K.; Condra, T.; Houbak, Niels
2002-01-01
Dynamic models for simulating boiler performance have been developed. Models for the flue gas side and for the evaporator circuit have been developed for the purpose of determining material temperatures and heat transfer from the flue gas side to the water-/steam side in order to simulate...... the circulation in the evaporator circuit. The models have been developed as Differential-Algebraic-Equations (DAE) and MATLAB has been applied for the integration of the models. In general MATLAB has proved to be very stable for the relatively stiff equation systems. Experimental verification is planned...... at a full scale plant equipped with instrumentation to verify heat transfer and circulation in the evaporator circuit....
Multiphysics Numerical Modeling of a Fin and Tube Heat Exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2015-01-01
In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM). For the ......In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM...
Modeling of Heat Transfer in the Helical-Coil Heat Exchanger for the Reactor Facility "UNITERM"
Directory of Open Access Journals (Sweden)
V. I. Solonin
2014-01-01
Full Text Available Circuit heat sink plays an important role in the reactor system. Therefore it imposes high requirements for quality of determining thermal-hydraulic parameters. This article is aimed at modeling of heat exchange process of the helical-coil heat exchanger, which is part of the heat sink circuit of the reactor facility "UNITERM."The simulation was performed using hydro-gas-dynamic software package ANSYS CFX. Computational fluid dynamics of this package allows us to perform calculations in a threedimensional setting, giving an idea of the fluid flow nature. The purpose of the simulation was to determine the parameters of the helical-coil heat exchanger (temperature, velocity at the outlet of the pipe and inter-tubular space, pressure drop, and the nature of the fluid flow of primary and intermediate coolants. Geometric parameters of the model were determined using the preliminary calculations performed by the criterion equations. In calculations Turbulence models k-ε RNG, Shear Stress Transport (SST are used. The article describes selected turbulence models, and considers relationship with wall function.The calculation results allow us to give the values obtained for thermal-hydraulic parameters, to compare selected turbulence models, as well as to show distribution patterns of the coolant temperature, pressure, and velocity at the outlet of the intermediate cooler.Calculations have shown that:- maximum values of primary coolant temperature at the outlet of the heat exchanger surface are encountered in the space between the helical-coil tubes;- higher temperatures of intermediate coolant at the outlet of the coils (in space of helicalcoil tubes are observed for the peripheral row;- primary coolant movement in the inter-tubular space of helical-coil surface is formed as a spiral flow, rather than as a in-line tube bank cross flow.
Papanastasiou, D. K.; Bartzanas, T.; Panagakis, P.; Zhang, G.; Kittas, C.
2016-11-01
It is well documented that heat-stress burdens sheep welfare and productivity. Peak heat-stress levels are observed when high temperatures prevail, i.e. during heat waves; however, continuous measurements inside livestock buildings are not usually available for long periods so as to study the variation of summer heat-stress levels for several years, especially during extreme hot weather. Α methodology to develop a long time series of summer temperature and relative humidity inside naturally ventilated sheep barns is proposed. The accuracy and the transferability of the developed linear regression models were verified. Temperature Humidity Index (THI) was used to assess sheep's potential heat-stress. Τhe variation of THI inside a barn during heat wave and non-heat wave days was examined, and the results were comparatively assessed. The analysis showed that sheep were exposed to moderate, severe, and extreme severe heat-stress in 10, 21 and 66 % of hours, respectively, during heat wave days, while the corresponding values during non-heat wave days were 14, 33 and 43 %, respectively. The heat load on sheep was much higher during heat wave events than during non-heat wave periods. Additionally, based on the averaged diurnal variation of THI, it was concluded that extreme severe heat-stress conditions were prevailing between 1000 and 2400 hours local time during heat wave days. Cool off night periods were never and extremely rarely detected during heat wave and non-heat wave days, respectively.
Model of Carbon Wire Heating in Accelerator Beam
Sapinski, M
2008-01-01
A heat flow equation with beam-induced heating and various cooling processes for a carbon wire passing through a particle beam is solved. Due to equation nonlinearity a numerical approach based on discretization of the wire movement is used. Heating of the wire due to the beam-induced electromagnetic field is taken into account. An estimation of the wire sublimation rate is made. The model is tested on SPS, LEP and Tevatron Main Injector data. Results are discussed and conclusions about limits of Wire Scanner operation on LHC beams are drawn.
An Energy Savings Model for the Heat Treatment of Castings
Energy Technology Data Exchange (ETDEWEB)
Y. Rong; R. Sisson; J. Morral; H. Brody
2006-12-31
An integrated system of software, databases, and design rules have been developed, verified, and to be marketed to enable quantitative prediction and optimization of the heat treatment of aluminum castings to increase quality, increase productivity, reduce heat treatment cycle times and reduce energy consumption. The software predicts the thermal cycle in critical locations of individual components in a furnace, the evolution of microstructure, and the attainment of properties in heat treatable aluminum alloy castings. The model takes into account the prior casting process and the specific composition of the component. The heat treatment simulation modules can be used in conjunction with software packages for simulation of the casting process. The system is built upon a quantitative understanding of the kinetics of microstructure evolution in complex multicomponent alloys, on a quantitative understanding of the interdependence of microstructure and properties, on validated kinetic and thermodynamic databases, and validated quantitative models.
Modelling of heat and mass transfer processes in neonatology
Energy Technology Data Exchange (ETDEWEB)
Ginalski, Maciej K [FLUENT Europe, Sheffield Business Park, Europa Link, Sheffield S9 1XU (United Kingdom); Nowak, Andrzej J [Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice (Poland); Wrobel, Luiz C [School of Engineering and Design, Brunel University, Uxbridge UB8 3PH (United Kingdom)], E-mail: maciej.ginalski@ansys.com, E-mail: Andrzej.J.Nowak@polsl.pl, E-mail: luiz.wrobel@brunel.ac.uk
2008-09-01
This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices.
A quantum heat engine based on Tavis-Cummings model
Sun, Kai-Wei; Li, Ran; Zhang, Guo-Feng
2017-09-01
This paper will investigate a four-stroke quantum heat engine based on the Tavis-Cummings model. The cycle of the heat engine is similar to the Otto cycle in classical thermodynamics. The relationship between output power as well as cycle efficiency and external physical system parameters are given. Under this condition, the entanglement behavior of the system will be studied. The system can show considerable entanglement by strictly controlling relevant parameters. Unlike common two-level quantum heat engines, efficiency is a function of temperature, showing interesting and unexpected phenomena. Several ways to adjust engine properties by external parameters are proposed, with which the output power and efficiency can be optimized. The heat engine model exhibits high efficiency and output power with the participation of a small number of photons, and decay rapidly as the number of photons increases in entangled area but shows interesting behaviors in non-entangled area of photon numbers.
Health Externalities and Heat savings in Energy System Modelling
DEFF Research Database (Denmark)
Zvingilaite, Erika
and included in an energy system optimisation model. The performed analysis of the Danish heat and power sector concludes that accounting for spatial variation of health damage costs in heat and power system optimisation model has an effect on the optimal technology mix and distribution of energy plants among...... and technologies, more remote location of energy plants and by reducing energy consumption. Considerable technical potential for energy demand reduction exists, particularly in buildings. In countries with cold climate, such as Denmark, energy demand for heating of buildings accounts for a significant share...... of the total energy consumption. Due to the long lifetime of buildings, they are an important part of the futureenergy systems. However, energy system studies often treat energy consumption and energy savings in buildings exogenously. At the same time heat savings in buildings are usually examined separately...
Transient Heat Transfer Model for Car Body Primer Curing
D. Zabala; N. Sánchez; J. Pinto
2010-01-01
A transient heat transfer mathematical model for the prediction of temperature distribution in the car body during primer baking has been developed by considering the thermal radiation and convection in the furnace chamber and transient heat conduction governing equations in the car framework. The car cockpit is considered like a structure with six flat plates, four vertical plates representing the car doors and the rear and front panels. The other two flat plates are the...
Mathematical modeling of heat transfer in plant community
Finnikov K.A.; Korzun A.M.; Kolesnichenko A.V.
2011-01-01
The conductive, convective and radiation heat exchange process in a natural system including plants aggregation, air lower layer and ground upper layer, is examined. The mathematical model of process is formulated in 1d unsteady approach. The numerical simulation of plants aggregation cooling is performed for the case of a radiation frost. It is found up that mutual influence of plants in an aggregation on the heat exchange with environment grows with the increase of plants size and plants nu...
Thermal performance modeling of cross-flow heat exchangers
Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria
2014-01-01
This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges
Modeling of supercritical extraction of mannitol from plane tree leaf.
Ghoreishi, S M; Sharifi, S
2001-03-01
The objective of this study was to investigate the theoretical feasibility of using supercritical fluid extraction of Mannitol from plane tree leaf as an alternative technology in the pharmaceutical industry. Simulation of an extraction column using dense liquid and supercritical carbon dioxide was modeled involving partial differential equations, using orthogonal collocation on finite elements. The important solvent extraction parameters such as the partition coefficient, mass transfer coefficient, dispersion coefficient, molecular diffusion and extraction efficiency (the amount of Mannitol extracted versus the amount of solvent used) were investigated as a function of the dimensionless Reynold's and Peclet numbers in order to optimize the extraction column geometry and the carbon dioxide operating conditions. The results of this study demonstrated that supercritical extraction is a viable technique for Mannitol production and that the process conditions for a large commercial extraction system do not require a high temperature in order to obtain a high extraction efficiency. However, at low pressures, the solubility of Mannitol in carbon dioxide would limit the success of the extraction process and at very high pressures the extraction technique may not be economically feasible. To investigate the authenticity of the mathematical model, the experimental data for the desorption of hexachlorobenzene from soil was compared with the theoretical results of this research. The model is able to predict the experimental data quite well without any adjustable parameters.
Maksimov Vyacheslav I.; Nagornova Tatiana A.; Shestakov Igor A.
2015-01-01
Results of mathematical modeling of convective heat transfer in air area surrounded on all sides enclosing structures, in the presence of heat source at the lower boundary of the media are presented. Solved the system of differential equations of unsteady Navier-Stokes equations with the appropriate initial and boundary conditions. The process of convective heat transfer is calculated using the models of turbulence Prandtl and Prandtl-Reichard. Takes into account the processes of heat exchang...
National Research Council Canada - National Science Library
Plaksina, Tatyana; White, Christopher
2016-01-01
.... In such geographic areas thick geopressured sandstones (up to several hundred meters thick) hold tremendous geothermal heat with conservative estimates of gross extractable energy approximately 0.2...
Real-time modeling of heat distributions
Energy Technology Data Exchange (ETDEWEB)
Hamann, Hendrik F.; Li, Hongfei; Yarlanki, Srinivas
2018-01-02
Techniques for real-time modeling temperature distributions based on streaming sensor data are provided. In one aspect, a method for creating a three-dimensional temperature distribution model for a room having a floor and a ceiling is provided. The method includes the following steps. A ceiling temperature distribution in the room is determined. A floor temperature distribution in the room is determined. An interpolation between the ceiling temperature distribution and the floor temperature distribution is used to obtain the three-dimensional temperature distribution model for the room.
Experimental and modelling evidence of shortening heat in cardiac muscle.
Tran, Kenneth; Han, June-Chiew; Crampin, Edmund John; Taberner, Andrew James; Loiselle, Denis Scott
2017-10-01
Heat associated with muscle shortening has been repeatedly demonstrated in skeletal muscle, but its existence in cardiac muscle remains contentious after five decades of study. By iterating between experiments and computational modelling, we show compelling evidence for the existence of shortening heat in cardiac muscle and reveal, mechanistically, the source of this excess heat. Our results clarify a long-standing uncertainty in the field of cardiac muscle energetics. We provide a revised partitioning of cardiac muscle energy expenditure to include this newly revealed thermal component. When a muscle shortens against an afterload, the heat that it liberates is greater than that produced by the same muscle contracting isometrically at the same level of force. This excess heat is defined as 'shortening heat', and has been repeatedly demonstrated in skeletal muscle but not in cardiac muscle. Given the micro-structural similarities between these two muscle types, and since we imagine that shortening heat is the thermal accompaniment of cross-bridge cycling, we have re-examined this issue. Using our flow-through microcalorimeter, we measured force and heat generated by isolated rat trabeculae undergoing isometric contractions at different muscle lengths and work-loop (shortening) contractions at different afterloads. We simulated these experimental protocols using a thermodynamically constrained model of cross-bridge cycling and probed the mechanisms underpinning shortening heat. Predictions generated by the model were subsequently validated by a further set of experiments. Both our experimental and modelling results show convincing evidence for the existence of shortening heat in cardiac muscle. Its magnitude is inversely related to the afterload or, equivalently, directly related to the extent of shortening. Computational simulations reveal that the heat of shortening arises from the cycling of cross-bridges, and that the rate of ATP hydrolysis is more sensitive to
Supervisory Model Predictive Control of the Heat Integrated Distillation Column
DEFF Research Database (Denmark)
Meyer, Kristian; Bisgaard, Thomas; Huusom, Jakob Kjøbsted
2017-01-01
This paper benchmarks a centralized control system based on model predictive control for the operation of the heat integrated distillation column (HIDiC) against a fully decentralized control system using the most complete column model currently available in the literature. The centralized control...
Simulating canopy temperature for modelling heat stress in cereals
Crop models must be improved to account for the large effects of heat stress effects on crop yields. To date, most approaches in crop models use air temperature despite evidence that crop canopy temperature better explains yield reductions associated with high temperature events. This study presents...
A Rotating Plug Model of Friction Stir Welding Heat Transfer
Raghulapadu J. K.; Peddieson, J.; Buchanan, G. R.; Nunes, A. C.
2006-01-01
A simplified rotating plug model is employed to study the heat transfer phenomena associated with the fiction stir welding process. An approximate analytical solution is obtained based on this idealized model and used both to demonstrate the qualitative influence of process parameters on predictions and to estimate temperatures produced in typical fiction stir welding situations.
Model for electrical conductivity of muscle meat during Ohmic heating
Sman, van der R.G.M.
2017-01-01
A model is presented for predicting the electrical conductivity of muscle meat, which can be used for the evaluation of Ohmic heating. The model computes the conductivity as a function of composition, temperature and microstructure. The muscle meat is thought to be composed of protein, water, salt.
A control model for district heating networks with storage
Scholten, Tjeert; De Persis, Claudio; Tesi, Pietro
2014-01-01
In [1] pressure control of hydraulic networks is investigated. We extend this work to district heating systems with storage capabilities and derive a model taking the topology of the network into account. The goal for the derived model is that it should allow for control of the storage level and
Modelling and simulation of a moving interface problem: freeze drying of black tea extract
Aydin, Ebubekir Sıddık; Yucel, Ozgun; Sadikoglu, Hasan
2017-06-01
The moving interface separates the material that is subjected to the freeze drying process as dried and frozen. Therefore, the accurate modeling the moving interface reduces the process time and energy consumption by improving the heat and mass transfer predictions during the process. To describe the dynamic behavior of the drying stages of the freeze-drying, a case study of brewed black tea extract in storage trays including moving interface was modeled that the heat and mass transfer equations were solved using orthogonal collocation method based on Jacobian polynomial approximation. Transport parameters and physical properties describing the freeze drying of black tea extract were evaluated by fitting the experimental data using Levenberg-Marquardt algorithm. Experimental results showed good agreement with the theoretical predictions.
Computational Model of Heat Transfer on the ISS
Torian, John G.; Rischar, Michael L.
2008-01-01
SCRAM Lite (SCRAM signifies Station Compact Radiator Analysis Model) is a computer program for analyzing convective and radiative heat-transfer and heat-rejection performance of coolant loops and radiators, respectively, in the active thermal-control systems of the International Space Station (ISS). SCRAM Lite is a derivative of prior versions of SCRAM but is more robust. SCRAM Lite computes thermal operating characteristics of active heat-transport and heat-rejection subsystems for the major ISS configurations from Flight 5A through completion of assembly. The program performs integrated analysis of both internal and external coolant loops of the various ISS modules and of an external active thermal control system, which includes radiators and the coolant loops that transfer heat to the radiators. The SCRAM Lite run time is of the order of one minute per day of mission time. The overall objective of the SCRAM Lite simulation is to process input profiles of equipment-rack, crew-metabolic, and other heat loads to determine flow rates, coolant supply temperatures, and available radiator heat-rejection capabilities. Analyses are performed for timelines of activities, orbital parameters, and attitudes for mission times ranging from a few hours to several months.
Heat transition during magnetic heating treatment: Study with tissue models and simulation
Energy Technology Data Exchange (ETDEWEB)
Henrich, Franziska [Technische Universität Dresden, Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, 01062 Dresden (Germany); Max Planck Institute for Polymer Research, Physics at Interfaces, 55128 Mainz (Germany); Rahn, Helene, E-mail: helene.rahn@tu-dresden.de [Technische Universität Dresden, Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, 01062 Dresden (Germany); Odenbach, Stefan [Technische Universität Dresden, Institute of Fluid Mechanics, Chair of Magnetofluiddynamics, 01062 Dresden (Germany)
2015-04-15
The magnetic heating treatment (MHT) is well known as a promising therapy for cancer diseases. Depending on concentration and specific heating power of the magnetic material as well as on parameters of the magnetic field, temperatures between 43 and 55 °C can be reached. This paper deals with the evaluation of heat distribution around such a heat source in a tissue model, thereby focusing on the heat transfer from tissue enriched with magnetic nanoparticles to regions of no or little enrichment of magnetic nanoparticles. We examined the temperature distribution with several tissue phantoms made of polyurethane (PUR) with similar thermal conductivity coefficient as biological tissue. These phantoms are composed of a cylinder with one sphere embedded, enriched with magnetic fluid. Thereby the spheres have different diameters in order to study the influence of the surface-to-volume ratio. The phantoms were exposed to an alternating magnetic field. The magnetically induced heat increase within the phantoms was measured with thermocouples. Those were placed at defined positions inside the phantoms. Based on the measured results a 3-dimensional simulation of each phantom was built. We achieved an agreement between the measured and simulated temperatures for all phantoms produced in this experimental study. The established experiment theoretically allows a prediction of temperature profiles in tumors and the surrounding tissue for the potential cancer treatment and therefore an optimization of e.g. the respective magnetic nanoparticles concentrations for the desirable rise of temperature. - Highlights: • Four phantoms built to measure the temperature distribution during magnetic heating. • Simulations have been carried out based on experimental data. • Measured and simulated temperature distribution for different magnetic field strength. • Temperature profiles for with ferrofluid enriched areas of different size. • Comparison of experimental and simulated data.
Heat transport modelling in EXTRAP T2R
Frassinetti, L.; Brunsell, P. R.; Cecconello, M.; Drake, J. R.
2009-02-01
A model to estimate the heat transport in the EXTRAP T2R reversed field pinch (RFP) is described. The model, based on experimental and theoretical results, divides the RFP electron heat diffusivity χe into three regions, one in the plasma core, where χe is assumed to be determined by the tearing modes, one located around the reversal radius, where χe is assumed not dependent on the magnetic fluctuations and one in the extreme edge, where high χe is assumed. The absolute values of the core and of the reversal χe are determined by simulating the electron temperature and the soft x-ray and by comparing the simulated signals with the experimental ones. The model is used to estimate the heat diffusivity and the energy confinement time during the flat top of standard plasmas, of deep F plasmas and of plasmas obtained with the intelligent shell.
Analysis of edge stability for models of heat flux width
Directory of Open Access Journals (Sweden)
M.A. Makowski
2017-08-01
Full Text Available Detailed measurements of the ne, Te, and Ti profiles in the vicinity of the separatrix of ELMing H-mode discharges have been used to examine plasma stability at the extreme edge of the plasma and assess stability dependent models of the heat flux width. The results are strongly contrary to the critical gradient model, which posits that a ballooning instability determines a gradient scale length related to the heat flux width. The results of this analysis are not sensitive to the choice of location to evaluate stability. Significantly, it is also found that the results are completely consistent with the heuristic drift model for the heat flux width. Here the edge pressure gradient scales with plasma density and is proportional to the pressure gradient inferred from the equilibrium in accordance with the predictions of that theory.
Mathematical modeling of heat transfer in plant community
Directory of Open Access Journals (Sweden)
Finnikov K.A.
2011-12-01
Full Text Available The conductive, convective and radiation heat exchange process in a natural system including plants aggregation, air lower layer and ground upper layer, is examined. The mathematical model of process is formulated in 1d unsteady approach. The numerical simulation of plants aggregation cooling is performed for the case of a radiation frost. It is found up that mutual influence of plants in an aggregation on the heat exchange with environment grows with the increase of plants size and plants number per ground area. The influence leads to that lower parts of plants are cooled slower, while upper parts are cooled faster. The estimations are made for the quantity of heat emitted in a thermogenic plant that is enough to prevent the plant cold stress. It is shown that in presence of enforced air flow the rate of plants cooling is noticeably lower, as well as the quantity of heat enough to prevent the plant cold stress.
Heat and Mass Transfer Model in Freeze-Dried Medium
Alfat, Sayahdin; Purqon, Acep
2017-07-01
There are big problems in agriculture sector every year. One of the major problems is abundance of agricultural product during the peak of harvest season that is not matched by an increase in demand of agricultural product by consumers, this causes a wasted agricultural products. Alternative way was food preservation by freeze dried method. This method was already using heat transfer through conduction and convection to reduce water quality in the food. The main objective of this research was to design a model heat and mass transfer in freeze-dried medium. We had two steps in this research, the first step was design of medium as the heat injection site and the second was simulate heat and mass transfer of the product. During simulation process, we use physical property of some agriculture product. The result will show how temperature and moisture distribution every second. The method of research use finite element method (FEM) and will be illustrated in three dimensional.
Modelling of ICRF heating in DEMO with special emphasis on bulk ion heating
Energy Technology Data Exchange (ETDEWEB)
Gallart, Dani, E-mail: daniel.gallart@bsc.es [Barcelona Supercomputing Center, Barcelona (Spain); Mantsinen, Mervi [Barcelona Supercomputing Center, Barcelona (Spain); Catalan Institution for Research and Advanced Studies, Barcelona (Spain); Kazakov, Yevgen [Laboratory for Plasma Physics LPP-ERM/KMS, Brussels (Belgium)
2015-12-10
Ion cyclotron resonance frequency (ICRF) heating is one of the auxiliary heating schemes presently envisaged for ITER and DEMO. In this paper we analyse the potential of ICRF waves to heat the fuel ions in DEMO. Our analysis is carried out for the DEMO1 Reference Scenario from October 2013 (B = 6.8 T, I = 18.6 MA, R = 9.25 m, a = 2.64 m) optimized for a maximum pulse length of 2.3 hrs using the ICRF modelling codes PION and TORIC. We focus on second harmonic heating of tritium and fundamental minority heating of {sup 3}He ions (with a few percent of {sup 3}He) in a 50%:50% D-T plasma. The dependence of the ICRF characteristics and the ICRF-accelerated ions on the ICRF and plasma parameters is investigated, giving special attention to the DEMO design point at a core plasma temperature of 30 keV and an electron density of 1.2·10{sup 20} m{sup −3}.
Radiative heating in global climate models
Energy Technology Data Exchange (ETDEWEB)
Baer, F.; Arsky, N.; Rocque, K. [Univ. of Maryland, College Park, MD (United States)
1996-04-01
LWR algorithms from various GCMs vary significantly from one another for the same clear sky input data. This variability becomes pronounced when clouds are included. We demonstrate this effect by intercomparing the various models` output using observed data including clouds from ARM/CART data taken in Oklahoma.
Enthalpy model for heating, melting, and vaporization in laser ablation
Directory of Open Access Journals (Sweden)
Vasilios Alexiades
2010-09-01
Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.
DEFF Research Database (Denmark)
Hedegaard, Karsten
in an energy system context. Energy systems analyses reveal that the heat pumps can even without flexible operation contribute significantly to facilitating larger wind power investments and reducing system costs, fuel consumption, and CO2 emissions. When equipping the heat pumps with heat storages, only......The fluctuating and only partly predictable nature of wind challenges an effective integration of large wind power penetrations. This PhD thesis investigates to which extent heat pumps, heat storages, and electric vehicles can support the integration of wind power. Considering the gaps in existing...... research, main focus is put on individual heat pumps in the residential sector and the possibilities for flexible operation, using the heat storage options available. Extensive model development is performed that significantly improves the possibilities for analysing individual heat pumps and heat storages...
Ruiz, Geraldine Avila; Opazo-Navarrete, Mauricio; Meurs, Marlon; Minor, Marcel; Sala, Guido; Boekel, van Tiny; Stieger, Markus; Janssen, Anja E.M.
2016-01-01
The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60,
A model for the spontaneous heating of stored coal
Energy Technology Data Exchange (ETDEWEB)
Schmal, D.
1987-01-01
To describe the spontaneous heating process in stored coal, a one dimensional model has been developed. From the calculations with the model and the experience made, understanding has been gained about a number of phenomena occurring in stored coal. Among them are the role of porosity in the stockpile in transport of moisture and oxygen, the role of evaporation and condensation in the heat balance, and consequently in the rate of combustion. It was also found that spontaneous heating is a very slow process. It can take years to reach a steady state. Measures to prevent oxygen from flowing into the pile lead in certain situations to an increased rate of spontaneous heating instead of the expected decrease. Losses of calorific value of the stored coal were estimated and compared with the costs of the measures against spontaneous combustion. The results of the calculations were also applied to the estimation of safe storage times. The model can also be used to get an insight into other types of processes (e.g. chemical reactions involving heat effects in packed bed reactors).
Wang, Wenjun; Ma, Xiaobin; Xu, Yuting; Cao, Yongqiang; Jiang, Zhumao; Ding, Tian; Ye, Xingqian; Liu, Donghong
2015-07-01
The extraction of pectin from grapefruit peel by ultrasound-assisted heating extraction (UAHE) was investigated using response surface methodology and compared with the conventional heating extraction (CHE). The optimized conditions were power intensity of 12.56 W/cm(2), extraction temperature of 66.71°C, and sonication time of 27.95 min. The experimental optimized yield was 27.34%, which was well matched with the predicted value (27.46%). Compared with CHE, UAHE provided higher yield increased by 16.34% at the temperature lowered by 13.3°C and the time shortened by 37.78%. Image studies showed that pectin extracted by UAHE showed better color and more loosen microstructure compared to that extracted by CHE, although Fourier Transform Infrared Analysis indicated insignificant difference in their chemical structures. Furthermore, UAHE pectin possessed lower viscosity, molecular weight and degree of esterification, but higher degree of branching and purity than CHE pectin, indicating that the former was preliminarily modified during the extraction process. Copyright © 2015 Elsevier Ltd. All rights reserved.
Modelling of storage tanks with immersed heat exchangers
Cadafalch Rabasa, Jordi; Carbonell Sánchez, Daniel; Consul Serracanta, Ricard; Ruiz Mansilla, Rafael
2015-01-01
A model of a storage tank with an immersed serpentine heat exchanger is described and validated against experimental data available from the literature. The tank is modelled one dimensionally using the multi-node approach corrected by an energy conservative reversion elimination algorithm to prevent inverse gradient solutions to occur. A one dimensional model in the flow direction is also used for the serpentine based on control volume techniques. The serpentine is discretized in equal sized ...
Pilot-scale radio frequency pasteurisation of chili powder: heating uniformity and heating model.
Li, Yukun; Zhang, Yongdi; Lei, Yujie; Fu, Hongfei; Chen, Xiangwei; Wang, Yunyang
2016-08-01
Microbial contamination is a vital obstacle needed to overcome for food safety of condiments. Radio frequency (RF) pasteurisation is a new technology to solve this obstacle. Temperature distribution and heating uniformity of sample, which are influenced by different factors, are the most important things affecting the nutritional ingredients and microbial safety of sample in the process of RF pasteurisation. This study demonstrated the location of cold spot in chili powder by analysing temperature distribution in horizontal and vertical direction. The related models were established and the accuracy was verified. Cold spot located on the centre of sample surface in the process of RF pasteurisation. The averaged temperature of sample increased linearly. The uniformity index decreased as the averaged temperature increased. Both the correlation coefficient of two equations were greater than 0.91. The error value of heating rate and heating uniformity index was 0.54% and 0.75% between the measured value and predicted value. Electric field was not uniformly distributed between RF parallel-plate electrodes in the RF pasteurisation of chili powder. The heating models were reliable to predict experiment results with high precision and accuracy. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.
Numerical modeling of the laser heated solenoid
Energy Technology Data Exchange (ETDEWEB)
Chung, C.S.
1973-01-01
A numerical model of the interaction of laser radiation with the magnetically confined plasma in an infinitive solenoid was given. An approximate solution which includes the balance of total pressure instead of momentum equation was also developed. Thus, the time step in computing is not bounded by the characteristics given by the Alfven speed. This approximation approach makes the efficient computing of this problem possible. The results of the approximate solution agree very well with those of the exact solution. They have the same final steady state solution.
An Information Extraction model for unconstrained handwritten documents
Thomas, Simon; Chatelain, Clement; Heutte, Laurent; Paquet, Thierry
2010-01-01
International audience; In this paper, a new information extraction system by statistical shallow parsing in unconstrained handwritten documents is introduced. Unlike classical approaches found in the literature as keyword spotting or full document recognition, our approch relies on a strong and powerful global handwriting model. A entire text line is considered as an indivisible entity and is modeled with Hidden Markov Models. In this way, text line shallow parsing allows fast extraction of ...
Modelling of the Heating Process in a Thermal Screw
Zhang, Xuan; Veje, Christian T.; Lassen, Benny; Willatzen, Morten
2012-11-01
The procedure of separating efficiently dry-stuff (proteins), fat, and water is an important process in the handling of waste products from industrial and commercial meat manufactures. One of the sub-processes in a separation facility is a thermal screw where the raw material (after proper mincing) is heated in order to melt fat, coagulate protein, and free water. This process is very energy consuming and the efficiency of the product is highly dependent on accurate temperature control of the process. A key quality parameter is the time that the product is maintained at temperatures within a certain threshold. A detailed mathematical model for the heating process in the thermal screw is developed and analysed. The model is formulated as a set of partial differential equations including the latent heat for the melting process of the fat and the boiling of water, respectively. The product is modelled by three components; water, fat and dry-stuff (bones and proteins). The melting of the fat component is captured as a plateau in the product temperature. The model effectively captures the product outlet temperature and the energy consumed. Depending on raw material composition, "soft" or "dry", the model outlines the heat injection and screw speeds necessary to obtain optimal output quality.
Directory of Open Access Journals (Sweden)
Maksimov Vyacheslav I.
2015-01-01
Full Text Available Results of mathematical modeling of convective heat transfer in air area surrounded on all sides enclosing structures, in the presence of heat source at the lower boundary of the media are presented. Solved the system of differential equations of unsteady Navier-Stokes equations with the appropriate initial and boundary conditions. The process of convective heat transfer is calculated using the models of turbulence Prandtl and Prandtl-Reichard. Takes into account the processes of heat exchange region considered with the environment. Is carried out the analysis of the dimensionless heat transfer coefficient at interfaces “air – enclosures”. The distributions average along the gas temperature range are obtained.
The thermodynamics of enhanced heat transfer: a model study
Hovhannisyan, Karen; Allahverdyan, Armen E.
2010-06-01
Situations where a spontaneous process of energy or matter transfer is enhanced by an external device are widespread in nature (the human sweating system, enzyme catalysis, facilitated diffusion across biomembranes, industrial heat-exchangers and so on). The thermodynamics of such processes remains, however, open. Here we study enhanced heat transfer by using a model junction immersed between two thermal baths at different temperatures Th and Tc (Th > Tc). The transferred heat power is enhanced via controlling the junction by means of external time-dependent fields. Provided that the spontaneous heat flow process is optimized over the junction Hamiltonian, any enhancement of this spontaneous process demands consumption and subsequent dissipation of work. The efficiency of the enhancement is defined via the increment in the heat power divided by the amount of work done. We show that this efficiency is bounded from above by Tc/(Th - Tc). Formally this is identical to the Carnot bound for the efficiency of ordinary refrigerators which transfer heat from cold to hot bodies. It also shares some (but not all) physical features of the Carnot bound.
A probabilistic model of a porous heat exchanger
Agrawal, O. P.; Lin, X. A.
1995-01-01
This paper presents a probabilistic one-dimensional finite element model for heat transfer processes in porous heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional model of heat transfer phenomenon in superfluid flow through a porous media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.
Testing and modelling of an electric tubular heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Terral, O. [Electricite de France, 77 - Moret sur Loing (France). Direction des Etudes et Recherches; Bandelier, P. [CEA/Grenoble, Dept. de Thermohydraulique et de Physique (DTP-GRETh), 38 (France)
1999-07-01
Electric Tubular Heat Exchanger (ETHE) is based on the principle of the Joule effect applied to a metallic tube submitted to a potential difference. It offers many advantages in concentration and evaporation processes. A numerical model (DIMDIPH) has been developed to predict the operating conditions and to design installations of ETHE evaporators. It is based on several correlations to estimate the main parameters: heat transfer coefficient giving the wall temperature, pressure drops along the tube, critical heat flux. The collaboration between the R and D division of EDF and the Greth aims to link the numerical approach with an experimental validation carried out with an evaporating pilot plant: Cannelle. The first experimental results obtained on a SNPE sulphuric acid concentrator pilot and on Cannelle are compared to the model predictions. In spite of some deviations in the subcooled region, the temperature profile trends remain similar with an overestimation from the correlations. (authors)
Rodent brain extraction using B-spline based deformable model.
Weimin Huang; Chen Ling; Su Huang; Zhongkang Lu; Zhiping Lin
2017-07-01
Accurate rodent brain extraction is one of the basic steps for many translational study using Magnetic Resonance Imaging (MRI). In this paper, we present a new approach to model the rodent brain variation using non-rigid B-spline image registration for the brain extraction in MRI images. We model the shape and appearance with the B-spline parameters together with a mean brain image. Followed by a method using multi-expert, we refine the brain extraction region. Compared with the image-based template model using cross-correlation, the performance for rodent brain extraction has shown much improvement on one data set while maintaining the similar yet more consistent performance for another. Both template based methods however outperform the voxel based method (3D PCNN) and a modified BET version for rodent brain extraction.
Models of the Solar Atmospheric Response to Flare Heating
Allred, Joel
2011-01-01
I will present models of the solar atmospheric response to flare heating. The models solve the equations of non-LTE radiation hydrodynamics with an electron beam added as a flare energy source term. Radiative transfer is solved in detail for many important optically thick hydrogen and helium transitions and numerous optically thin EUV lines making the models ideally suited to study the emission that is produced during flares. I will pay special attention to understanding key EUV lines as well the mechanism for white light production. I will also present preliminary results of how the model solar atmosphere responds to Fletcher & Hudson type flare heating. I will compare this with the results from flare simulations using the standard thick target model.
Directory of Open Access Journals (Sweden)
Veljković Vlada B.
2002-01-01
Full Text Available The extraction of resinoids from St. John's wort (Hypericum perforatum L was studied in a series of two papers. While the first part dealt with the effects of the operating conditions on the yield of resinoids (total extract and process optimization, the mathematical models of extraction kinetics were analyzed in the second one. The extraction was carried out using an aqueous solution of ethanol (70 and 95 % v/v at the hydromodulus (plant material to solvent ratio, w/v of 1:5 or 1:10. The plant material was disintegrated and divided into three fractions (particle mean size 0.23, 0.57 and 1.05 mm. The temperature was 25, 50 or about 80°C (boiling temperature. Three models were applied for modeling the extraction kinetics: a model based on the film theory, a model based on unsteady state diffusion through solid material and the empirical Ponomarev equation. Because of its physical basis, the relative simplicity and good fitting of the experimental data, the model based on the film theory could be proposed for mathematical modeling of solid-liquid etraction processes.
Ocean carbon and heat variability in an Earth System Model
Thomas, J. L.; Waugh, D.; Gnanadesikan, A.
2016-12-01
Ocean carbon and heat content are very important for regulating global climate. Furthermore, due to lack of observations and dependence on parameterizations, there has been little consensus in the modeling community on the magnitude of realistic ocean carbon and heat content variability, particularly in the Southern Ocean. We assess the differences between global oceanic heat and carbon content variability in GFDL ESM2Mc using a 500-year, pre-industrial control simulation. The global carbon and heat content are directly out of phase with each other; however, in the Southern Ocean the heat and carbon content are in phase. The global heat mutli-decadal variability is primarily explained by variability in the tropics and mid-latitudes, while the variability in global carbon content is primarily explained by Southern Ocean variability. In order to test the robustness of this relationship, we use three additional pre-industrial control simulations using different mesoscale mixing parameterizations. Three pre-industrial control simulations are conducted with the along-isopycnal diffusion coefficient (Aredi) set to constant values of 400, 800 (control) and 2400 m2 s-1. These values for Aredi are within the range of parameter settings commonly used in modeling groups. Finally, one pre-industrial control simulation is conducted where the minimum in the Gent-McWilliams parameterization closure scheme (AGM) increased to 600 m2 s-1. We find that the different simulations have very different multi-decadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. While the temporal frequency and amplitude global heat and carbon content changes significantly, the overall spatial pattern of variability remains unchanged between the simulations.
Yu, Zhitao; Miller, Franklin; Pfotenhauer, John M.
2017-12-01
Both a numerical and analytical model of the heat and mass transfer processes in a CO2, N2 mixture gas de-sublimating cross-flow finned duct heat exchanger system is developed to predict the heat transferred from a mixture gas to liquid nitrogen and the de-sublimating rate of CO2 in the mixture gas. The mixture gas outlet temperature, liquid nitrogen outlet temperature, CO2 mole fraction, temperature distribution and de-sublimating rate of CO2 through the whole heat exchanger was computed using both the numerical and analytic model. The numerical model is built using EES [1] (engineering equation solver). According to the simulation, a cross-flow finned duct heat exchanger can be designed and fabricated to validate the models. The performance of the heat exchanger is evaluated as functions of dimensionless variables, such as the ratio of the mass flow rate of liquid nitrogen to the mass flow rate of inlet flue gas.
Specific heat of the simple-cubic Ising model
Feng, X.; Blöte, H.W.J.
2010-01-01
We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions
Large scale solar district heating. Evaluation, modelling and designing - Appendices
Energy Technology Data Exchange (ETDEWEB)
Heller, A.
2000-07-01
The appendices present the following: A) Cad-drawing of the Marstal CSHP design. B) Key values - large-scale solar heating in Denmark. C) Monitoring - a system description. D) WMO-classification of pyranometers (solarimeters). E) The computer simulation model in TRNSYS. F) Selected papers from the author. (EHS)
Numerical Model Study of In Vivo Magnetic Nanoparticle Tumor Heating.
Pearce, John A; Petryk, Alicia A; Hoopes, P Jack
2017-12-01
Iron oxide nanoparticles are currently under investigation as heating agents for hyperthermic treatment of tumors. Major determinants of effective heating include the biodistribution and minimum iron oxide loading required to achieve adequate heating at practically achievable magnetic field strengths. These inter-related criteria ultimately determine the practicality of this approach to tumor treatment. Further, in our experience the currently used treatment assessment criterion for hyperthermia treatment-cumulative equivalent minutes at 43 °C, CEM43 -provides an inadequate description of the expected treatment effectiveness. Couple numerical models to experimental measurements to study the relative heating effectiveness described by cell death predictions. FEM numerical models were applied to increase the understanding of a carefully calibrated series of experiments in mouse mammary adenocarcinoma. The numerical model results indicate that minimum tumor loadings between approximately 1.3 to 1.8 mg of Fe per cm3 of tumor tissue are required to achieve the experimentally observed temperatures in magnetic field strengths of 32 kA/m (rms) at 162 kHz. We show that including multiple cell death processes operating in parallel within the numerical models provides valuable perspective on the likelihood of successful treatment. We show and believe that these assessment methods are more accurate than a single assessment figure of merit based only on the comparison of thermal histories, such as the CEM method.
Comparison of performance of simulation models for floor heating
DEFF Research Database (Denmark)
Weitzmann, Peter; Svendsen, Svend
2005-01-01
only the floor construction, the differences can be directly compared. In this comparison, a two-dimensional model of a slab-on-grade floor including foundation is used as reference. The other models include a one-dimensional model and a thermal network model including the linear thermal transmittance......This paper describes the comparison of performance of simulation models for floor heating with different level of detail in the modelling process. The models are compared in an otherwise identical simulation model containing room model, walls, windows, ceiling and ventilation system. By exchanging...... of the foundation. The result can be also be found in the energy consumption of the building, since up to half the energy consumption is lost through the ground. Looking at the different implementations it is also found, that including a 1m ground volume below the floor construction under a one-dimensional model...
Khan, Sumaira; Kazi, Tasneem Gul; Afridi, Hassan Imran; Kolachi, Nida Fatima; Ullah, Naeem; Dev, Kapil
2013-01-01
A fast microwave-assisted extraction procedure was developed for the speciation of vanadium (V) species in soil samples collected from the vicinity of the Lakhra coal power plant (situated near a coal mining area) and industrial and agricultural areas. Soil samples were treated with two extracting reagents, (NH4)2HPO4 (0.2-1 M) and Na2CO3 (0.1-0.5 M), and heated by conventional and microwave methods for different time intervals to extract V+5 species. The V+4 and total V were extracted from filtration residue and the same subsamples of soil by treating with the acid mixture of HNO3-HCl-HClO4-H2SO4 (1:1:1:1, v/v/v/v). No significant difference between V+5 contents obtained by conventional heating and microwave-assisted extraction was observed (P = 0.485). The extraction efficiency of 0.6 M (NH4)2HPO4 for V+5 was lower (4-7%) than that obtained by 0.2 M Na2CO3 solution. The levels of V+5 were higher in soil samples collected from the vicinity of the Lakhra coal power plant and industrial areas, compared to those obtained from agricultural soil.
Ruiz, Geraldine Avila; Opazo-Navarrete, Mauricio; Meurs, Marlon; Minor, Marcel; Sala, Guido; van Boekel, Martinus; Stieger, Markus; Janssen, Anja E M
The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components.
Modelling of Boiler Heating Surfaces and Evaporator Circuits
DEFF Research Database (Denmark)
Sørensen, Kim; Condra, Thomas Joseph; Houbak, Niels
2002-01-01
Dynamic models for simulating boiler performance have been developed. Models for the ue gas side and for the evaporator circuit have been developed for the purpose of determining material temperatures and heat transfer from the ue gas side to the water-/steam side in order to simulate...... the circulation in the evaporator circuit. The models have been developed as Differential-Algebraic-Equation systems (DAE) and MATLAB has been applied for the integration of the models. In general MATLAB has proved to be very stable for these relatively stiff equation systems. Experimental verication is planned...... at a full scale plant equipped with instrumentation to verify heat transfer and circulation in the evaporator circuit....
Directory of Open Access Journals (Sweden)
Yang Li
2014-01-01
Full Text Available The heating performance of enzyme-assisted aqueous processing-extracted blended oil (EAEPO, hexane-extracted blended oil (HEBO, and three kinds of blended oils was investigated by varying the heating times. Oil degradation was monitored by analysis of the acid value (AV, peroxide value (PV, p-anisidine value (p-AV, color, and trans-fatty acid composition. The fatty acid ratios of EAEPO, HEBO, and the three kinds of blended oils were very similar (0.27 : 1.03 : 0.96, 0.27 : 1.08 : 1.16, 0.27 : 0.65 : 0.8, 0.27 : 0.6 : 0.84, and 0.27 : 0.61 : 0.79, resp.. The AV and color increased in proportion to the heating time for all the oils. There was a rapid increase in the PV and p-AV of EAEPO and HEBO after heating for only 1 h, whereas the other three blended oils showed a rapid increase after heating for 2 h or 6 h. Despite the highest trans-fatty acid content found for HEBO, this content was relatively low and remained low up to a heating time of 8 h. It was found that after heating, a fatty acid ratio relatively close to its ideal value (0.27 : 0.48 : 0.49 was maintained by EAEPO, which indicates that EAEPO is tolerant to heat treatment and is suitable for maintaining a healthy diet.
Extracting conceptual models from user stories with Visual Narrator
Lucassen, Garm|info:eu-repo/dai/nl/412351366; Robeer, Marcel; Dalpiaz, Fabiano|info:eu-repo/dai/nl/369508394; van der Werf, Jan Martijn E. M.|info:eu-repo/dai/nl/36950674X; Brinkkemper, Sjaak|info:eu-repo/dai/nl/07500707X
2017-01-01
Extracting conceptual models from natural language requirements can help identify dependencies, redundancies, and conflicts between requirements via a holistic and easy-to-understand view that is generated from lengthy textual specifications. Unfortunately, existing approaches never gained traction
Modeling supercritical fluid extraction process involving solute-solid interaction
Energy Technology Data Exchange (ETDEWEB)
Goto, M.; Roy, B. Kodama, A.; Hirose, T. [Kumamoto Univ., Kumamoto (Japan)
1998-04-01
Extraction or leaching of solute from natural solid material is a mass transfer process involving dissolution or release of solutes from a solid matrix. Interaction between the solute and solid matrix often influences the supercritical fluid extraction process. A model accounting for the solute-solid interaction as well as mass transfer is developed. The BET equation is used to incorporate the interaction and the solubility of solutes into the local equilibrium in the model. Experimental data for the supercritical extraction of essential oil and cuticular wax from peppermint leaves are successfully analyzed by the model. The effects of parameters on the extraction behavior are demonstrated to illustrate the concept of the model. 18 refs., 5 figs., 1 tab.
Specific heat of a non-local attractive Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Calegari, E.J., E-mail: eleonir@ufsm.br [Laboratório de Teoria da Matéria Condensada, Departamento de Física, UFSM, 97105-900, Santa Maria, RS (Brazil); Lobo, C.O. [Laboratório de Teoria da Matéria Condensada, Departamento de Física, UFSM, 97105-900, Santa Maria, RS (Brazil); Magalhaes, S.G. [Instituto de Física, Universidade Federal Fluminense, Av. Litorânea s/n, 24210, 346, Niterói, Rio de Janeiro (Brazil); Chaves, C.M.; Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150, 22290-180, Rio de Janeiro, RJ (Brazil)
2013-10-01
The specific heat C(T) of an attractive (interaction G<0) non-local Hubbard model is investigated within a two-pole approximation that leads to a set of correlation functions, which play an important role as a source of anomalies as the pseudogap. For a giving range of G and n{sub T} (where n{sub T}=n{sub ↑}+n{sub ↓}), the specific heat as a function of the temperature presents a two peak structure. Nevertehelesss, the presence of a pseudogap eliminates the two peak structure. The effects of the second nearest-neighbor hopping on C(T) are also investigated.
Thermal Behavior and Heat Generation Modeling of Lithium Sulfur Batteries
DEFF Research Database (Denmark)
Stroe, Daniel-Ioan; Knap, Vaclav; Swierczynski, Maciej Jozef
2017-01-01
Lithium Sulfur batteries are receiving a lot of research interest because of their intrinsic characteristics, such as very high energy density and increased safety, which make them a suitable solution for zero-emission vehicles and space application. This paper analyses the influence...... of the temperature on the performance parameters of a 3.4 Ah Lithium-Sulfur battery cell. Furthermore, the values of the internal resistance and entropic heat coefficient, which are necessary for the parametrization of a heat generation model, are determined experimentally....
Models for Metal Hydride Particle Shape, Packing, and Heat Transfer
Smith, Kyle C.; Fisher, Timothy S.
2012-01-01
A multiphysics modeling approach for heat conduction in metal hydride powders is presented, including particle shape distribution, size distribution, granular packing structure, and effective thermal conductivity. A statistical geometric model is presented that replicates features of particle size and shape distributions observed experimentally that result from cyclic hydride decrepitation. The quasi-static dense packing of a sample set of these particles is simulated via energy-based structu...
Kondjoyan, Alain; Oillic, Samuel; Portanguen, Stéphane; Gros, Jean-Bernard
2013-10-01
A heat transfer model was used to simulate the temperature in 3 dimensions inside the meat. This model was combined with a first-order kinetic models to predict cooking losses. Identification of the parameters of the kinetic models and first validations were performed in a water bath. Afterwards, the performance of the combined model was determined in a fan-assisted oven under different air/steam conditions. Accurate knowledge of the heat transfer coefficient values and consideration of the retraction of the meat pieces are needed for the prediction of meat temperature. This is important since the temperature at the center of the product is often used to determine the cooking time. The combined model was also able to predict cooking losses from meat pieces of different sizes and subjected to different air/steam conditions. It was found that under the studied conditions, most of the water loss comes from the juice expelled by protein denaturation and contraction and not from evaporation. Copyright © 2013 Elsevier Ltd. All rights reserved.
Induction Heating Model of Cermet Fuel Element Environmental Test (CFEET)
Gomez, Carlos F.; Bradley, D. E.; Cavender, D. P.; Mireles, O. R.; Hickman, R. R.; Trent, D.; Stewart, E.
2013-01-01
Deep space missions with large payloads require high specific impulse and relatively high thrust to achieve mission goals in reasonable time frames. Nuclear Thermal Rockets (NTR) are capable of producing a high specific impulse by employing heat produced by a fission reactor to heat and therefore accelerate hydrogen through a rocket nozzle providing thrust. Fuel element temperatures are very high (up to 3000 K) and hydrogen is highly reactive with most materials at high temperatures. Data covering the effects of high-temperature hydrogen exposure on fuel elements are limited. The primary concern is the mechanical failure of fuel elements due to large thermal gradients; therefore, high-melting-point ceramics-metallic matrix composites (cermets) are one of the fuels under consideration as part of the Nuclear Cryogenic Propulsion Stage (NCPS) Advance Exploration System (AES) technology project at the Marshall Space Flight Center. The purpose of testing and analytical modeling is to determine their ability to survive and maintain thermal performance in a prototypical NTR reactor environment of exposure to hydrogen at very high temperatures and obtain data to assess the properties of the non-nuclear support materials. The fission process and the resulting heating performance are well known and do not require that active fissile material to be integrated in this testing. A small-scale test bed; Compact Fuel Element Environmental Tester (CFEET), designed to heat fuel element samples via induction heating and expose samples to hydrogen is being developed at MSFC to assist in optimal material and manufacturing process selection without utilizing fissile material. This paper details the analytical approach to help design and optimize the test bed using COMSOL Multiphysics for predicting thermal gradients induced by electromagnetic heating (Induction heating) and Thermal Desktop for radiation calculations.
MATHEMATICAL MODELING OF UNSTEADY HEAT EXCHANGE IN A PASSENGER CAR
Directory of Open Access Journals (Sweden)
I. Yu. Khomenko
2013-07-01
Full Text Available Purpose.Existing mathematicalmodelsofunsteadyheatexchangeinapassengercardonotsatisfytheneedofthedifferentconstructivedecisionsofthelifesupportsystemefficiencyestimation. They also don’t allow comparing new and old life support system constructions influence on the inner environment conditions. Moreoverquite frequently unsteady heat exchange processes were studied at the initial car motion stage. Due to the new competitive engineering decisionsof the lifesupportsystemthe need of a new mathematical instrument that would satisfy the mentioned features and their influence on the unsteadyheatexchangeprocesses during the whole time of the road appeared. The purpose of this work is creation of the mathematicalmodel ofunsteadyheatexchangeinapassengercarthatcan satisfythe above-listed requirements. Methodology. Fortheassigned task realizationsystemofdifferentialequationsthatcharacterizesunsteadyheatexchangeprocessesinapassengercarwascomposed; forthesystemof equationssolution elementary balance method was used. Findings. Computational algorithm was developed andcomputer program for modeling transitional heat processes in the car was designed. It allows comparing different life support system constructions influence on the inner environment conditionsand unsteady heat exchange processes can be studied at every car motion stage. Originality.Mathematicalmodelofunsteadyheatexchangeinapassengercarwasimproved. That is why it can be used for the heat engineering studying of the inner car state under various conditions and for the operation of the different life support systems of passenger cars comparison. Mathematicalmodelingofunsteadyheatexchangeinapassengercarwas made by the elementary balance method. Practical value. Created mathematical model gives the possibility to simulate temperature changes in passenger car on unsteady thermal conditions with enough accuracy and to introduce and remove additional elements to the designed model. Thus different
Modeling of conjugated heat transfer in unsteady hypersonic flow
Pogudalina, S. V.; Goldfeld, M. A.; Pickalov, V. V.; Fedorova, N. N.
2017-10-01
Heat exchange of a blunt cylinder in a hypersonic (M = 6) air flow are studied numerically. Calculations are carried out in ANSYS Fluent, taking into account the conjugate heat transfer between the external flow and the solid model under steady and transient incoming flow conditions. As a result of the calculations, the fields of temperature and other external flow parameters were obtained. The heating regimes are defined for the steel model and the heat transfer sensor installed in the frontal part of the model. Results of the analysis of gas temperature measurement are presented at change of the temperature from 1400 K to 2000 K in an impulse wind tunnel with operation time up to 160 ms. The total temperature was measured by chromel -alumel thermocouples with the junction sizes of 0.05, 0.1 and 0.2 mm. Deconvolution method was used for the solution of convolution integral equation. Thermocouples calibration was done by measurements of temperature step-function. Deconvolution method allows obtaining distinctive feature in the form of temperature peak, which is typical for the temperature distribution in impulse wind tunnels. The estimation of an error of reconstruction of total temperature by means of the offered approach has demonstrated that the temperature can be reconstructed with accuracy not worse than 8%.
Directory of Open Access Journals (Sweden)
Wenchie Marie L. Lumbera
2016-03-01
Full Text Available There is a high association of heat shock on the alteration of energy and lipid metabolism. The alterations associated with thermal stress are composed of gene expression changes and adaptation through biochemical responses. Previous study showed that Angelica gigas Nakai (AGN root extract promoted adipogenic differentiation in murine 3T3-L1 preadipocytes under the normal temperature condition. However, its effect in heat shocked 3T3-L1 cells has not been established. In this study, we investigated the effect of AGN root hot water extract in the adipogenic differentiation of murine 3T3-L1 preadipocytes following heat shock and its possible mechanism of action. Thermal stress procedure was executed within the same stage of preadipocyte confluence (G0 through incubation at 42°C for one hour and then allowed to recover at normal incubation temperature of 37°C for another hour before AGN treatment for both cell viability assay and Oil Red O. Cell viability assay showed that AGN was able to dose dependently (0 to 400 μg/mL increase cell proliferation under normal incubation temperature and also was able to prevent cytotoxicity due to heat shock accompanied by cell proliferation. Confluent preadipocytes were subjected into heat shock procedure, recovery and then AGN treatment prior to stimulation with the differentiation solution. Heat shocked preadipocytes exhibited reduced differentiation as supported by decreased amount of lipid accumulation in Oil Red O staining and triglyceride measurement. However, those heat shocked preadipocytes that then were given AGN extract showed a dose dependent increase in lipid accumulation as shown by both evaluation procedures. In line with these results, real-time polymerase chain reaction (RT-PCR and Western blot analysis showed that AGN increased adipogenic differentiation by upregulating heat shock protection related genes and proteins together with the adipogenic markers. These findings imply the potential of
Direct containment heating models in the CONTAIN code
Energy Technology Data Exchange (ETDEWEB)
Washington, K.E.; Williams, D.C.
1995-08-01
The potential exists in a nuclear reactor core melt severe accident for molten core debris to be dispersed under high pressure into the containment building. If this occurs, the set of phenomena that result in the transfer of energy to the containment atmosphere and its surroundings is referred to as direct containment heating (DCH). Because of the potential for DCH to lead to early containment failure, the U.S. Nuclear Regulatory Commission (USNRC) has sponsored an extensive research program consisting of experimental, analytical, and risk integration components. An important element of the analytical research has been the development and assessment of direct containment heating models in the CONTAIN code. This report documents the DCH models in the CONTAIN code. DCH models in CONTAIN for representing debris transport, trapping, chemical reactions, and heat transfer from debris to the containment atmosphere and surroundings are described. The descriptions include the governing equations and input instructions in CONTAIN unique to performing DCH calculations. Modifications made to the combustion models in CONTAIN for representing the combustion of DCH-produced and pre-existing hydrogen under DCH conditions are also described. Input table options for representing the discharge of debris from the RPV and the entrainment phase of the DCH process are also described. A sample calculation is presented to demonstrate the functionality of the models. The results show that reasonable behavior is obtained when the models are used to predict the sixth Zion geometry integral effects test at 1/10th scale.
Hernández-Pinero, Jorge Luis; Terrón-Rebolledo, Manuel; Foroughbakhch, Rahim; Moreno-Limón, Sergio; Melendrez, M. F.; Solís-Pomar, Francisco; Pérez-Tijerina, Eduardo
2016-11-01
Mixing aqueous silver solutions with aqueous leaf aromatic plant extracts from basil, mint, marjoram and peppermint resulted in the synthesis of quasi-spherical silver nanoparticles in a range of size between 2 and 80 nm in diameter as analyzed by analytical high-resolution electron microscopy. The average size could be controlled by applying heat to the initial reaction system at different rates of heating, and by the specific botanical species employed for the reaction. Increasing the rate of heating resulted in a statistically significant decrease in the size of the nanoparticles produced, regardless of the species employed. This fact was more evident in the case of marjoram, which decreased the average diameter from 27 nm at a slow rate of heating to 8 nm at a high rate of heating. With regard to the species, minimum sizes of mint yielded an average size between 10 and 25 nm. The results indicate that aromatic plant extracts can be used to achieve the controlled synthesis of metal nanoparticles.
Feature Extraction for Structural Dynamics Model Validation
Energy Technology Data Exchange (ETDEWEB)
Farrar, Charles [Los Alamos National Laboratory; Nishio, Mayuko [Yokohama University; Hemez, Francois [Los Alamos National Laboratory; Stull, Chris [Los Alamos National Laboratory; Park, Gyuhae [Chonnam Univesity; Cornwell, Phil [Rose-Hulman Institute of Technology; Figueiredo, Eloi [Universidade Lusófona; Luscher, D. J. [Los Alamos National Laboratory; Worden, Keith [University of Sheffield
2016-01-13
As structural dynamics becomes increasingly non-modal, stochastic and nonlinear, finite element model-updating technology must adopt the broader notions of model validation and uncertainty quantification. For example, particular re-sampling procedures must be implemented to propagate uncertainty through a forward calculation, and non-modal features must be defined to analyze nonlinear data sets. The latter topic is the focus of this report, but first, some more general comments regarding the concept of model validation will be discussed.
Modelling, simulating and optimizing boiler heating surfaces and evaporator circuits
DEFF Research Database (Denmark)
Sørensen, Kim; Condra, Thomas Joseph; Houbak, Niels
2003-01-01
for the optimization a dynamic model for the boiler is applied. Furthermore a function for the value of the dynamic performance is included in the model. The dynamic models for simulating boiler performance consists of a model for the ue gas side, a model for the evaporator circuit and a model for the drum....... The dynamic model has been developed for the purpose of determining boiler material temperatures and heat transfer from the ue gas side to the water-/steam side in order to simulate the circulation in the evaporator circuit and hereby the water level uctuations in the drum. The dynamic model has been...... transfer, circulation in the evaporator circuit and water level uctuations in the drum....
Modelling, simulating and optimizing boiler heating surfaces and evaporator circuits
DEFF Research Database (Denmark)
Sørensen, K.; Condra, T.; Houbak, Niels
2003-01-01
for the optimization a dynamic model for the boiler is applied. Furthermore a function for the value of the dynamic performance is included in the model. The dynamic models for simulating boiler performance consists of a model for the flue gas side, a model for the evaporator circuit and a model for the drum....... The dynamic model has been developed for the purpose of determining boiler material temperatures and heat transfer from the flue gas side to the water-/steam side in order to simulate the circulation in the evaporator circuit and hereby the water level fluctuations in the drum. The dynamic model has been...... transfer, circulation in the evaporator circuit and water level fluctuations in the drum....
Effect of heat/pressure on cyanidin-3-glucoside ethanol model solutions
Energy Technology Data Exchange (ETDEWEB)
Corrales, M; Lindauer, R; Butz, P; Tauscher, B [Institute of Chemistry and Biology, Federal Research Centre for Nutrition and Food, 76131 Karlsruhe (Germany)], E-mail: margarita.corrales@bfel.de
2008-07-15
The stability of cyanidin-3-glucoside (Cy3gl) in 50% ethanol model solutions under heat/pressure treatments was investigated. Cy3gl was rapidly degraded when solutions were subjected to a heat/pressure treatment. The higher the pressure and the temperature used, the higher the degradation. Moreover, the degradation was increased according to increasing holding times. Parallel to the degradation of Cy3gl several hydrolytic products were formed and identified by LC-DAD/ESI-MS. The degradation of Cy3gl was well fitted to a first order reaction (R=0.99). This study pointed out the rate of susceptibility of Cy3gl in model solutions to degrade when exposed to a heat/pressure treatment and the trigger effect of high hydrostatic pressure to hydrolyse Cy3gl. By contrast, the degradation of anthocyanins in a food matrix (red grape extract solutions) was negligible after a heat/pressure process at 600MPa, 70 deg. C during 1h (P >0.05)
MODELING OF TRANSIENT HEAT TRANSFER IN FOAMED CONCRETE SLAB
Directory of Open Access Journals (Sweden)
MD AZREE OTHUMAN MYDIN
2013-06-01
Full Text Available This paper reports the basis of one-dimensional Finite Difference method to obtain thermal properties of foamed concrete in order to solve transient heat conduction problems in multi-layer panels. In addition, this paper also incorporates the implementation of the method and the validation of thermal properties model of foamed concrete. A one-dimensional finite difference heat conduction programme has been developed to envisage the temperature development through the thickness of the foamed concrete slab, based on an initial estimate of the thermal conductivity-temperature relationship as a function of porosity and radiation within the voids. The accuracy of the model was evaluated by comparing predicted and experimental temperature profiles obtained from small scale heat transfer test on foamed concrete slabs, so that the temperature history of the specimen calculated by the programme closely matches those recorded during the experiment. Using the thermal properties of foamed concrete, the validated heat transfer program predicts foamed concrete temperatures in close agreement with experimental results obtained from a number of high temperature tests. The proposed numerical and thermal properties are simple yet efficient and can be utilised to aid manufacturers to develop their products without having to conduct numerous large-scale fire tests.
Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters
Energy Technology Data Exchange (ETDEWEB)
Bogle, Brandon [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kelly, James [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Haslam, Jeffrey [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-09-29
The purpose of this report is to showcase an initial finite-element analysis model of a ceramic High-Efficiency Particulate (HEPA) Air filter design. Next generation HEPA filter assemblies are being developed at LLNL to withstand high-temperature fire scenarios by use of ceramics and advanced materials. The filters are meant for use in radiological and nuclear facilities, and are required to survive 500°C fires over an hour duration. During such conditions, however, collecting data under varying parameters can be challenging; therefore, a Finite Element Analysis model of the filter was conducted using COMSOL ® Multiphysics to analyze the effects of fire. Finite Element Analysis (FEA) modelling offers several opportunities: researchers can quickly and easily consider impacts of potential design changes, material selection, and flow characterization on filter performance. Specifically, this model provides stress references for the sealant at high temperatures. Modeling of full filter assemblies was deemed inefficient given the computational requirements, so a section of three tubes from the assembly was modeled. The model looked at the transient heating and thermomechanical stress development during a 500°C air flow at 6 CFM. Significant stresses were found at the ceramic-metal interfaces of the filter, and conservative temperature profiles at locations of interest were plotted. The model can be used for the development of sealants that minimize stresses at the ceramic-metal interface. Further work on the model would include the full filter assembly and consider heat losses to make more accurate predictions.
Beam Heating of Samples: Modeling and Verification. Part 2
Kazmierczak, Michael; Gopalakrishnan, Pradeep; Kumar, Raghav; Banerjee Rupak; Snell, Edward; Bellamy, Henry; Rosenbaum, Gerd; vanderWoerd, Mark
2006-01-01
Energy absorbed from the X-ray beam by the sample requires cooling by forced convection (i.e. cryostream) to minimize temperature increase and the damage caused to the sample by the X-ray heating. In this presentation we will first review the current theoretical models and recent studies in the literature, which predict the sample temperature rise for a given set of beam parameters. It should be noted that a common weakness of these previous studies is that none of them provide actual experimental confirmation. This situation is now remedied in our investigation where the problem of x-ray sample heating is taken up once more. We have theoretically investigated, and at the same time, in addition to the numerical computations, performed experiments to validate the predictions. We have modeled, analyzed and experimentally tested the temperature rise of a 1 mm diameter glass sphere (sample surrogate) exposed to an intense synchrotron X-ray beam, while it is being cooled in a uniform flow of nitrogen gas. The heat transfer, including external convection and internal heat conduction was theoretically modeled using CFD to predict the temperature variation in the sphere during cooling and while it was subjected to an undulator (ID sector 19) X-ray beam at the APS. The surface temperature of the sphere during the X-ray beam heating was measured using the infrared camera measurement technique described in a previous talk. The temperatures from the numerical predictions and experimental measurements are compared and discussed. Additional results are reported for the two different sphere sizes and for two different supporting pin orientations.
Numerical modeling of some engineering heat transfer problems
Energy Technology Data Exchange (ETDEWEB)
Eriksson, Daniel
1998-04-01
Engineering heat transfer problems are very often of a complex nature and most often no analytical solutions exist. One way to create solutions to such problems is to apply numerical methods. This study concerns heat transfer problems with coupled conduction, convection and thermal radiation. Five important but different engineering problems are considered. (1) The transient temperature distribution in a rotating cylinder which is exposed to a time varying incident heat flux, e.g. a nuclear burst, is determined. The cylinder is cooled by mixed convection and thermal radiation. The effects of the leading parameters, such as rotation speed, the cooling parameters and the physical properties of the shell are studied. (2) The cooling of a roll system which is transporting/casting a thin hot plastic film. The leading roll is heated by the hot film, cooled at the interior by forced convection and on the outside by forced convection, thermal radiation and contact with a support roll. The influence of the cooling parameters and the rotation are studied. (3) The heat and mass diffusion in pre-insulated district heating/cooling pipes. The task is to determine the effects of the gas mass transport through the casing of the pipes on the thermal behaviour and effects of condensed water due to the mass diffusion of water vapour. The importance of the density of the casing, the wall thickness of the casing, the thickness of the insulation and the surrounding temperature is revealed. (4) The development of a cooling system for an electrical unit in which a time dependent heat is generated due to the Joule effect. (5) The heat transfer from a rectangular fin in a confined space. The fin is cooled by turbulent forced convection. The turbulence model applied is a low Reynolds k-{epsilon}-model. Predicted results are compared with experimental ones, and a correlation for the Nusselt number is proposed. The effects of thermal radiation for non-participating as well as participating
Ruiz, Geraldine Avila; Xiao, Wukai; Boekel, van Tiny; Minor, Marcel; Stieger, Markus
2016-01-01
The aim of this study was to determine the influence of extraction pH on heat-induced aggregation, gelation and microstructure of suspensions of protein isolates extracted from quinoa (Chenopodium quinoa Willd). Quinoa seed protein was extracted by alkaline treatment at various pH values (pH 8
Stochastic and deterministic model of microbial heat inactivation.
Corradini, Maria G; Normand, Mark D; Peleg, Micha
2010-03-01
Microbial inactivation is described by a model based on the changing survival probabilities of individual cells or spores. It is presented in a stochastic and discrete form for small groups, and as a continuous deterministic model for larger populations. If the underlying mortality probability function remains constant throughout the treatment, the model generates first-order ("log-linear") inactivation kinetics. Otherwise, it produces survival patterns that include Weibullian ("power-law") with upward or downward concavity, tailing with a residual survival level, complete elimination, flat "shoulder" with linear or curvilinear continuation, and sigmoid curves. In both forms, the same algorithm or model equation applies to isothermal and dynamic heat treatments alike. Constructing the model does not require assuming a kinetic order or knowledge of the inactivation mechanism. The general features of its underlying mortality probability function can be deduced from the experimental survival curve's shape. Once identified, the function's coefficients, the survival parameters, can be estimated directly from the experimental survival ratios by regression. The model is testable in principle but matching the estimated mortality or inactivation probabilities with those of the actual cells or spores can be a technical challenge. The model is not intended to replace current models to calculate sterility. Its main value, apart from connecting the various inactivation patterns to underlying probabilities at the cellular level, might be in simulating the irregular survival patterns of small groups of cells and spores. In principle, it can also be used for nonthermal methods of microbial inactivation and their combination with heat.
Multivariate Statistical Modelling of Drought and Heat Wave Events
Manning, Colin; Widmann, Martin; Vrac, Mathieu; Maraun, Douglas; Bevaqua, Emanuele
2016-04-01
Multivariate Statistical Modelling of Drought and Heat Wave Events C. Manning1,2, M. Widmann1, M. Vrac2, D. Maraun3, E. Bevaqua2,3 1. School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK 2. Laboratoire des Sciences du Climat et de l'Environnement, (LSCE-IPSL), Centre d'Etudes de Saclay, Gif-sur-Yvette, France 3. Wegener Center for Climate and Global Change, University of Graz, Brandhofgasse 5, 8010 Graz, Austria Compound extreme events are a combination of two or more contributing events which in themselves may not be extreme but through their joint occurrence produce an extreme impact. Compound events are noted in the latest IPCC report as an important type of extreme event that have been given little attention so far. As part of the CE:LLO project (Compound Events: muLtivariate statisticaL mOdelling) we are developing a multivariate statistical model to gain an understanding of the dependence structure of certain compound events. One focus of this project is on the interaction between drought and heat wave events. Soil moisture has both a local and non-local effect on the occurrence of heat waves where it strongly controls the latent heat flux affecting the transfer of sensible heat to the atmosphere. These processes can create a feedback whereby a heat wave maybe amplified or suppressed by the soil moisture preconditioning, and vice versa, the heat wave may in turn have an effect on soil conditions. An aim of this project is to capture this dependence in order to correctly describe the joint probabilities of these conditions and the resulting probability of their compound impact. We will show an application of Pair Copula Constructions (PCCs) to study the aforementioned compound event. PCCs allow in theory for the formulation of multivariate dependence structures in any dimension where the PCC is a decomposition of a multivariate distribution into a product of bivariate components modelled using copulas. A
Lawrence, Ellen
2016-01-01
Is it possible to make heat by rubbing your hands together? Why does an ice cube melt when you hold it? In this title, students will conduct experiments to help them understand what heat is. Kids will also investigate concepts such as which materials are good at conducting heat and which are the best insulators. Using everyday items that can easily be found around the house, students will transform into scientists as they carry out step-by-step experiments to answer interesting questions. Along the way, children will pick up important scientific skills. Heat includes seven experiments with detailed, age-appropriate instructions, surprising facts and background information, a "conclusions" section to pull all the concepts in the book together, and a glossary of science words. Colorful, dynamic designs and images truly put the FUN into FUN-damental Experiments.
Extraction of lycopene from tomato processing waste: kinetics and modelling.
Poojary, Mahesha M; Passamonti, Paolo
2015-04-15
Lycopene, a nutraceutical compound, was extracted from tomato processing waste, an abundantly available food industry by-product in Italy. The extraction kinetics was mathematically described using the first order kinetic model, the mass transfer model and Peleg's model to understand the physicochemical behaviour of the extraction. Samples were extracted using acetone/n-hexane mixtures at different ratios (1:3, 2:2 and 3:1, v/v) and at different temperatures (30, 40 and 50 °C) and simultaneously analysed using UV-VIS spectrophotometry. The lycopene yield was in the range 3.47-4.03 mg/100g, which corresponds to a percentage recovery of 65.22-75.75. All kinetic models gave a good fit to the experimental data, but the best one was Peleg's model, having the highest RAdj(2) and the lowest RMSE, MBE and χ(2) values. All the models confirmed that a temperature of 30 °C and solvent mixture of acetone/n-hexane 1:3 (v/v) provided optimal conditions for extraction of lycopene. Copyright © 2014 Elsevier Ltd. All rights reserved.
Modeling ray tracing through heating perturbed ionosphere with SAMI2
Wu, T.; Huba, J. D.; Bernhardt, P. A.
2012-12-01
We present simulations of high frequency (HF) signals/rays tracing through perturbed ionosphere by combining the NRL ionosphere model [Huba, 2000] and the ray tracing program [Jones, 1966]. We show with modeling that by creating artificial disturbances to the ionosphere, i.e. heating-induced geomagnetic-field-aligned density ducts, the radio signal transmission may be deflected out of its original propagation path and may exit the top ionosphere through the density breach at the F2 peak layer. Our results show the possibility to control or disrupt the communication channels in the future.; The solid line shows deviated ray trace due to F2 layer breach created by heat-induced density ducts. The dashed line shows the original ray path when no disturbances present.
Modelling hot electron generation in short pulse target heating experiments
Directory of Open Access Journals (Sweden)
Sircombe N.J.
2013-11-01
Full Text Available Target heating experiments planned for the Orion laser facility, and electron beam driven fast ignition schemes, rely on the interaction of a short pulse high intensity laser with dense material to generate a flux of energetic electrons. It is essential that the characteristics of this electron source are well known in order to inform transport models in radiation hydrodynamics codes and allow effective evaluation of experimental results and forward modelling of future campaigns. We present results obtained with the particle in cell (PIC code EPOCH for realistic target and laser parameters, including first and second harmonic light. The hot electron distributions are characterised and their implications for onward transport and target heating are considered with the aid of the Monte-Carlo transport code THOR.
Bulygin, Y. I.; Koronchik, D. A.; Legkonogikh, A. N.; Zharkova, M. G.; Azimova, N. N.
2017-05-01
The standard k-epsilon turbulence model, adapted for welding workshops, equipped with fixed workstations with sources of pollution took into account only the convective component of heat transfer, which is quite reasonable for large-volume rooms (with low density distribution of sources of pollution) especially the results of model calculations taking into account only the convective component correlated well with experimental data. For the purposes of this study, when we are dealing with a small confined space where necessary to take account of the body heated to a high temperature (for welding), located next to each other as additional sources of heat, it can no longer be neglected radiative heat exchange. In the task - to experimentally investigate the various types of heat transfer in a limited closed space for welding and behavior of a mathematical model, describing the contribution of the various components of the heat exchange, including radiation, influencing the formation of fields of concentration, temperature, air movement and thermal stress in the test environment. Conducted field experiments to model cubic body, allowing you to configure and debug the model of heat and mass transfer processes with the help of the developed approaches, comparing the measurement results of air flow velocity and temperature with the calculated data showed qualitative and quantitative agreement between process parameters, that is an indicator of the adequacy of heat and mass transfer model.
Ráice, Rui
2015-01-01
This study concerns the identification and characterisation of volatile components of fruits, and evaluation of the effect of heat treatment and drying on retention or loss of volatiles of fruits. The investigation included developing a procedure to extract volatile components from the fruit matrix, a purification step, separation, identification and quantification. Initial experiments with Vangueria infausta L. showed that some components, especially sugars, degrade during ...
Skeleton extraction based on the topology and Snakes model
Directory of Open Access Journals (Sweden)
Yuanxue Cai
Full Text Available A new skeleton line extraction method based on topology and flux is proposed by analyzing the distribution characteristics of the gradient vector field in the Snakes model. The distribution characteristics of the skeleton line are accurately obtained by calculating the eigenvalues of the critical points and the flux of the gradient vector field. Then the skeleton lines can be effectively extracted. The results also show that there is no need for the pretreatment or binarization of the target image. The skeleton lines of complex gray images such as optical interference patterns can be effectively extracted by using this method. Compared to traditional methods, this method has many advantages, such as high extraction accuracy and fast processing speed. Keywords: Skeleton, Snakes model, Topology, Photoelasticity image
A Combustion and Heat Transfer Model for Porous Media
1982-06-01
combustion process in two phases. During the initial phase, combustion occurs within the porous medium. The second phase occurs when the exo- thermic ...the combustion model. Specifically, there is a change in the behavior of combustion when insulated boundaries on the porous solid are changed to...represent insulated boundaries on the porous solid (i.e., no heat loss from the porous solid to the environment). Expressions III. 51 and III. 52 provide for
Enhancing natural product extraction and mass transfer using selective microwave heating
Lee, Chai Siah; Binner, Eleanor; Winkworth-Smith, Charles; John, Rebecca; Gomes, R.L.; Robinson, John
2016-01-01
This study uses a combination of empirical observations and an analysis of mass transfer behaviour to yield new insights into the mechanism of microwave assisted extraction. Enhancements in extraction rate and yield were observed experimentally compared with conventional extraction at temperatures in excess of 50°C, however at lower temperatures there was no observable difference between the two processes. A step-change in extract yield between microwave and conventional processes was shown t...
Energy Technology Data Exchange (ETDEWEB)
Choi, Chiwoong; Ha, Kwiseok; Hong, Jonggan; Yeom, Sujin; Eoh, Jaehyuk [Sodium-cooled Fast Reactor Design Division, Korea Atomic Energy Research Institute (KAERI), 989-111, Daedeok-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Jeong, Hae-yong, E-mail: hyjeong@sejong.ac.kr [Department of Nuclear Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)
2016-11-15
Highlights: • The capability of the MARS-LMR for heat transfer through IHX and DHX is evaluated. • Prediction of heat transfer through IHXs and DHXs is essential in the SFR analysis. • Data obtained from the STELLA-1 and the JOYO test are analyzed with the MARS-LMR. • MARS-LMR adopts the Aoki’s correlation for tube side and Graber-Rieger’s for shell. • The performance of the basic models and other available correlations is evaluated. • The current models in MARS-LMR show best prediction for JOYO and STELLA-1 data. - Abstract: The MARS-LMR code has been developed by the Korea Atomic Energy Research Institute (KAERI) to analyze transients in a pool-type sodium-cooled fast reactor (SFR). Currently, KAERI is developing a prototype Gen-IV SFR (PGSFR) with metallic fuel. The decay heat exchangers (DHXs) and the intermediate heat exchangers (IHXs) were designed as a sodium-sodium counter-flow tube bundle type for decay heat removal system (DHRS) and intermediate heat transport system (IHTS), respectively. The IHX and DHX are important components for a heat removal function under normal and accident conditions, respectively. Therefore, sodium heat transfer models for the DHX and IHX heat exchangers were added in MARS-LMR. In order to validate the newly added heat transfer model, experimental data were obtained from the JOYO and STELLA-1 facilities were analyzed. JOYO has two different types of IHXs: type-A (co-axial circular arrangement) and type-B (triangular arrangement). For the code validation, 38 and 39 data points for type A and type B were selected, respectively. A DHX performance test was conducted in STELLA-1, which is the test facility for heat exchangers and primary pump in the PGSFR. The DHX test in STELLA-1 provided eight data points for a code validation. Ten nodes are used in the heat transfer region is used, based on the verification test for the heat transfer models. RMS errors for JOYO IHX type A and type B of 19.1% and 4.3% are obtained
Modeling of high power ICRF heating experiments on TFTR
Energy Technology Data Exchange (ETDEWEB)
Phillips, C.K.; Wilson, J.R.; Bell, M.; Fredrickson, E.; Hosea, J.C.; Majeski, R.; Ramsey, A.; Rogers, J.H.; Schilling, G.; Skinner, C.; Stevens, J.E.; Taylor, G.; Wong, K.L. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Khudaleev, A.; Petrov, M.P. (Ioffe Inst., St. Petersburg (Russian Federation)); Murakami, M. (Oak Ridge National Lab., TN (United States))
1993-01-01
Over the past two years, ICRF heating experiments have been performed on TFTR in the hydrogen minority heating regime with power levels reaching 11.2 MW in helium-4 majority plasmas and 8.4 MW in deuterium majority plasmas. For these power levels, the minority hydrogen ions, which comprise typically less than 10% of the total electron density, evolve into la very energetic, anisotropic non-Maxwellian distribution. Indeed, the excess perpendicular stored energy in these plasmas associated with the energetic minority tail ions is often as high as 25% of the total stored energy, as inferred from magnetic measurements. Enhanced losses of 0.5 MeV protons consistent with the presence of an energetic hydrogen component have also been observed. In ICRF heating experiments on JET at comparable and higher power levels and with similar parameters, it has been suggested that finite banana width effects have a noticeable effect on the ICRF power deposition. In particular, models indicate that finite orbit width effects lead to a reduction in the total stored energy and of the tail energy in the center of the plasma, relative to that predicted by the zero banana width models. In this paper, detailed comparisons between the calculated ICRF power deposition profiles and experimentally measured quantities will be presented which indicate that significant deviations from the zero banana width models occur even for modest power levels (P[sub rf] [approximately] 6 MW) in the TFTR experiments.
Modeling of high power ICRF heating experiments on TFTR
Energy Technology Data Exchange (ETDEWEB)
Phillips, C.K.; Wilson, J.R.; Bell, M.; Fredrickson, E.; Hosea, J.C.; Majeski, R.; Ramsey, A.; Rogers, J.H.; Schilling, G.; Skinner, C.; Stevens, J.E.; Taylor, G.; Wong, K.L. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Khudaleev, A.; Petrov, M.P. [Ioffe Inst., St. Petersburg (Russian Federation); Murakami, M. [Oak Ridge National Lab., TN (United States)
1993-04-01
Over the past two years, ICRF heating experiments have been performed on TFTR in the hydrogen minority heating regime with power levels reaching 11.2 MW in helium-4 majority plasmas and 8.4 MW in deuterium majority plasmas. For these power levels, the minority hydrogen ions, which comprise typically less than 10% of the total electron density, evolve into la very energetic, anisotropic non-Maxwellian distribution. Indeed, the excess perpendicular stored energy in these plasmas associated with the energetic minority tail ions is often as high as 25% of the total stored energy, as inferred from magnetic measurements. Enhanced losses of 0.5 MeV protons consistent with the presence of an energetic hydrogen component have also been observed. In ICRF heating experiments on JET at comparable and higher power levels and with similar parameters, it has been suggested that finite banana width effects have a noticeable effect on the ICRF power deposition. In particular, models indicate that finite orbit width effects lead to a reduction in the total stored energy and of the tail energy in the center of the plasma, relative to that predicted by the zero banana width models. In this paper, detailed comparisons between the calculated ICRF power deposition profiles and experimentally measured quantities will be presented which indicate that significant deviations from the zero banana width models occur even for modest power levels (P{sub rf} {approximately} 6 MW) in the TFTR experiments.
Dynamic modelling of pectin extraction describing yield and functional characteristics
DEFF Research Database (Denmark)
Andersen, Nina Marianne; Cognet, T.; Santacoloma, P. A.
2017-01-01
A dynamic model of pectin extraction is proposed that describes pectin yield, degree of esterification and intrinsic viscosity. The dynamic model is one dimensional in the peel geometry and includes mass transport of pectin by diffusion and reaction kinetics of hydrolysis, degradation and de-este...
Xi, Jun; He, Lang; Yan, Lianggong
2015-01-01
In the study, the kinetics of pressure-assisted solvent extraction (PSE) of polyphenols from green tea at different pressures (300, 400, 500 MPa) was studied. The model derived from Patricelli, which describes the two step extraction consisting of rapid washing followed by slow diffusion, had been applied to estimate the extraction kinetics. The model parameters were calculated using the experimental results obtained from PSE and conventional solvent extraction (CSE). The results showed a good prediction of Patricelli's model for extraction kinetics in all experiments (R(2)≥0.996), which gave the possibility for estimation of the extraction rate and extent of PSE. The results also showed that the extraction by washing was more efficient with PSE than CSE. In addition, the initial extraction rate of the PSE was always much larger than that of the CSE. Therefore, PSE was more effective for extracting the green tea polyphenols than the CSE. Copyright © 2014 Elsevier Ltd. All rights reserved.
Czech Academy of Sciences Publication Activity Database
Sovová, Helena
2005-01-01
Roč. 33, č. 1 (2005), s. 35-52 ISSN 0896-8446 R&D Projects: GA AV ČR IAA4072102 Institutional research plan: CEZ:AV0Z4072921 Keywords : supercritical extraction * natural products * model Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.144, year: 2005
Energy Technology Data Exchange (ETDEWEB)
Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinek, Janna G [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-06-03
Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000 degrees C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40 degrees C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to =720 degrees C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.
Ma, Chih-Ming; Cheng, Chih-Lun; Lee, Shang-Chieh; Hong, Gui-Bing
2018-01-05
The aim of this study was to examine the effect of process factors such as ethanol concentration, extraction time and temperature on the extraction yield and the bioactive contents of Tagetes lemmonii leaf extracts using response surface methodology (RSM). ANOVA results showed that the response variables were affected by the ethanol concentration to a very significant degree and by extraction temperature to a lesser degree. GC/MS characterization showed that the extract is rich in bioactive compounds and those present exhibited important biological activities such as antioxidant, insect repellence and insecticidal activities. The results from the toxicity assay demonstrate that the extract obtained from the leaves of Tagetes lemmonii was an effective insect toxin against Tribolium castaneum. The radical scavenging activity and p-anisidine test results of olive oil spiked with different concentrations of leaf extract showed that the phenolic compounds can retard lipid oxidation. Copyright © 2018 Elsevier Inc. All rights reserved.
A Preliminary Study of Heat Strain Using Modelling and Simulation
2006-05-01
opérationnelles s’imposent. Le personnel militaire est confronté à un certain nombre de risques qui doivent être réduits, et la fatigue due à la chaleur n’est...collaborative agreement now in place, DRDC Toronto has a mechanism to exchange models or data with QinetiQ14 and future exchanges should proceed more...A preliminary study of heat strain using modelling and simulation (U) Étude préliminaire sur la fatigue due à la chaleur à l’aide de la modélisation
Lattice Boltzmann heat transfer model for permeable voxels
Pereira, Gerald G.; Wu, Bisheng; Ahmed, Shakil
2017-12-01
We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribution to rock permeability. The LB temperature field is compared to a finite difference solution of the continuum partial differential equations for fluid flow in a channel. Excellent quantitative agreement is found for both Poiseuille channel flow and Brinkman flow. The LB model is then applied to sample porous media such as packed beds and also more realistic sandstone rock sample, and both the convective and diffusive regimes are recovered when varying the thermal diffusivity. It is found that while the rock permeability can be comparatively small (order milli-Darcy), the temperature field can show significant variation depending on the thermal convection of the fluid. This LB method has significant advantages over other numerical methods such as finite and boundary element methods in dealing with coupled fluid flow and heat transfer in rocks which have irregular and nonsmooth pore spaces.
MODELING OF THE HEAT PUMP STATION CONTROLABLE LOOP OF AN INTERMEDIATE HEAT-TRANSFER AGENT (Part II
Directory of Open Access Journals (Sweden)
Sit M.L.
2011-08-01
Full Text Available It is studied the model of the heat pump station controllable loop of an intermediate heat-transfer agent for the use in wineries. There are demonstrated transients after the disturbing action of the temperature on the input of cooling jacket of the fermentation stirred tank. There are compared different control laws of the object.
Modelling the supercritical CO2 extraction kinetics of soybean oil
Directory of Open Access Journals (Sweden)
Sandra Svilović
2015-01-01
Full Text Available Different empirical models were used to describe the supercritical CO2 extraction of soybean oil obtained at series of operational parameters namely pressure, temperature, solvent flow rate and characteristic particle size. Process yields obtained by supercritical CO2 were up to 19.33%. Several kinetic models: Brunner, Kandiah and Spiro, Tan and Liou, Martinez et al. and Esquivel et al. were used to test the experimental yield data. All models were analysed using nonlinear regression method. Also a new model, modified Esquivel et al., was proposed and analysed using nonlinear regression method as well. According to the obtained results for extraction yield of soybean oil, the modified Esquivel et al. model show the best agreement between experimental and model calculated data.
Antithrombotic Potential of Tormentil Extract in Animal Models
Directory of Open Access Journals (Sweden)
Natalia Marcinczyk
2017-08-01
Full Text Available Potentilla species that have been investigated so far display pharmacological activity mainly due to the presence of polyphenols. Recently, it was shown that polyphenol-rich extract from rhizome of Potentilla erecta (tormentil extract affects the metabolism of arachidonic acid and exerts both anti-inflammatory and anti-oxidant activities, suggesting a possible effect on thrombosis. Accordingly, the aim of the study was to evaluate the effect of tormentil extract on haemostasis in a rat model of thrombosis. Lyophilized water-methanol extract from P. erecta rhizome was administrated per os for 14 days in doses of 100, 200, and 400 mg/kg in a volume of 2 mL/kg in a 5% water solution of gummi arabici (VEH. In the in vivo experiment an electrically induced carotid artery thrombosis model with blood flow monitoring was used in Wistar rats. Collected blood samples were analyzed ex vivo functionally and biochemically for changes in haemostasis. Tormentil extract (400 mg/kg significantly decreased thrombus weight and prolonged the time to carotid artery occlusion and bleeding time without changes in the blood pressure. In the ex vivo experiment tormentil extract (400 mg/kg reduced thromboxane production and decreased t-PA activity, while total t-PA concentration, as well as total PAI-1 concentration and PAI-1 activity remained unchanged. Furthermore, tormentil extract (400 mg/kg decreased bradykinin concentration and shortened the time to reach maximal optical density during fibrin generation. Prothrombin time, activated partial thromboplastin time, QUICK index, fibrinogen level, and collagen-induced aggregation remained unchanged. To investigate the involvement of platelets in the antithrombotic effect of tormentil, the extract was administrated per os for 2 days to mice and irreversible platelets activation after ferric chloride induced thrombosis was evaluated under intravital conditions using confocal microscopy system. In this model tormentil
Skeleton extraction based on the topology and Snakes model
Cai, Yuanxue; Ming, Chengguo; Qin, Yueting
A new skeleton line extraction method based on topology and flux is proposed by analyzing the distribution characteristics of the gradient vector field in the Snakes model. The distribution characteristics of the skeleton line are accurately obtained by calculating the eigenvalues of the critical points and the flux of the gradient vector field. Then the skeleton lines can be effectively extracted. The results also show that there is no need for the pretreatment or binarization of the target image. The skeleton lines of complex gray images such as optical interference patterns can be effectively extracted by using this method. Compared to traditional methods, this method has many advantages, such as high extraction accuracy and fast processing speed.
Directory of Open Access Journals (Sweden)
Carmen Díaz
2016-10-01
Full Text Available In order to avoid the loss of anthocyanins during the preparation of black corn (Zea mays L. as food, and for the extraction of these metabolites for industrial purposes, it is necessary to determine the effect of several factors that influence its final content. The objective of this work was to extract anthocyanins from black corn cultivated in Tunshi-Chimborazo, Ecuador subjected to different heat treatments for scalding. Black corn seeds were used and planted manually. The corn cobs harvests were subjected to three scalding treatments (immersion in boiling water, steam and microwave with 160W of power with three times (3, 5 and 7 minutes. In addition, a control treatment was included without application of heat treatment. The content of total anthocyanins per sample was calculated as cyanidin 3-glucoside equivalent per kg fresh mass (mg kg-1. The content of anthocyanins was found to vary with the heat treatment applied. The extraction times conditioned the differences in anthocyanin content only at the extreme values for immersion in boiling water. Heat treatment methods of black corn for sclading such as immersion in boiling water, steam and microwave with 160 W of power condition the anthocyanin content. The maximum reduction of the anthocyanin equivalent content of cyanidin in the black corn grains was obtained in the treatment with immersion in boiling water during 7 min where it was reduced in 79%, while the preservation in these of the content of anthocyanins was achieved with the use of microwave with 160W of power for 3 min. Keywords: microwave, secondary metabolites, Zea mays
Energy Technology Data Exchange (ETDEWEB)
Zheng, L.; Samper, J.; Montenegro, L.; Fernandez, A.M.
2010-05-01
Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed on a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous
Heat transfer corrected isothermal model for devolatilization of thermally-thick biomass particles
DEFF Research Database (Denmark)
Luo, Hao; Wu, Hao; Lin, Weigang
Isothermal model used in current computational fluid dynamic (CFD) model neglect the internal heat transfer during biomass devolatilization. This assumption is not reasonable for thermally-thick particles. To solve this issue, a heat transfer corrected isothermal model is introduced. In this model......, two heat transfer corrected coefficients: HT-correction of heat transfer and HR-correction of reaction, are defined to cover the effects of internal heat transfer. A series of single biomass devitalization case have been modeled to validate this model, the results show that devolatilization behaviors...... of both thermally-thick and thermally-thin particles are predicted reasonable by using heat transfer corrected model, while, isothermal model overestimate devolatilization rate and heating rate for thermlly-thick particle.This model probably has better performance than isothermal model when it is coupled...
2013-04-03
... mathematical modeling methods used in predicting the dispersion of heated effluent in natural water bodies. The... COMMISSION Reporting Procedure for Mathematical Models Selected To Predict Heated Effluent Dispersion in... Mathematical Models Selected to Predict Heated Effluent Dispersion in Natural Water Bodies.'' The guide is...
A Mathematical Model of Heat Transfer in Spheroplastic
Directory of Open Access Journals (Sweden)
V. S. Zarubin
2016-01-01
Full Text Available Spheroplastics are composite materials composed of a polymer or organosilicate binder and hollow spherical inclusions (mostly, of glass, but there are also of carbon, phenol, and epoxy, which are called microspheres and have a diameter within a millimeter with the wall thickness of several micrometers. To reduce the material density in watercraft constructions sometimes are used so called macrospheres of up to 40 mm in diameter and shell thickness of 0,5--1,5 mm from spheroplastic with microspheres.Microspheres may contain inert gases such as nitrogen. Many countries have commercialised quartz microspheres. The USA, in particular, produces Q-Gel microspheres with density of 300 kg / m3, the bulk density - 100 kg / m3 and the average diameter of 75 microns,characterized by a high mechanical strength and low cost. Carbon microspheres having low mechanical properties can absorb radio waves in certain frequency ranges. Spheroplastic with silicone microspheres combine relatively high mechanical and dielectric properties.In virtue of low thermal conductivity spheroplastics are used in various heat-insulating structures. As the thermal insulation coatings, the spheroplastic covers the outer surface of the pipes, in particular oil and gas pipelines in the permafrost zones, regions of swampy ground, and underwater. The effective heat conductivity factor, primarily, determines the specific application of spheroplastic as a thermal insulation material. To quantify the value of this factor is necessary to have a mathematical model describing heat ransfer in spheroplastic.The paper presents a four-phase mathematical model of the heat transfer in a representative element of a spheroplastic structure placed in an unlimited array of homogeneous material, the thermal conductivity of which is to be determined as desired characteristics of spheroplastic. This model in combination with a dual variational formulation of stationary heat conduction problem in the
Modeling the Effect of Wider Canyons on Urban Heating
Directory of Open Access Journals (Sweden)
Rizwan Ahmed Memon
2011-04-01
Full Text Available The k-? turbulence model is adopted in this study to simulate the impact of street canyon AR (Aspect Ratios on heating within street canyon. The two-dimensional model was validated for RANS (Reynolds Averaged Navier Stokes and energy transport equations. The validation process confirms that the results of the model for airtemperature and wind speed could be trusted. The application of the said model is carried out to ideal street canyons of ARs (ratio of building-height-to-street-width from 0.4 to 2 with the same boundary conditions. Notably, street canyon aspect ratio was calculated by varying the street width while keeping the building height constant. Results show that the weighted-average-air-temperature within AR 0.4 was around 0.8% (i.e. 2.4K higher than that within AR 2.0. Conversely, there was strong correlation (i.e., R2>0.9 between air temperature within the street canyon and street canyon AR. Results demonstrate stronger influence of vertical velocity on heating within street canyon. Evidently, increased vertical velocity decreased the temperatures. Conversely, temperatures were higher along the leeward side of the canyon in lower ARs.
Modeling activity transport in the CANDU heat transport system
Energy Technology Data Exchange (ETDEWEB)
Guzonas, D.A.; Qiu, L. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)
2010-07-01
The release and transport of corrosion products from the surfaces of primary coolant system components is a serious concern for all water-cooled nuclear power plants. The consequences of high levels of corrosion product transport are twofold: a) increased corrosion product (crud) deposition on fuel cladding surfaces, leading to reduced heat transfer and the possibility of fuel failures, and b) increased production of radioactive species by neutron activation, resulting in increased out-of-core radiation fields and worker dose. In recent years, a semi-empirical activity transport model has been successfully developed to predict the deposition of radionuclides, including {sup 60}Co, {sup 95}Zr, {sup 124}Sb and fission products, around the CANDU® primary Heat Transport System (HTS), and to predict radiation fields at the steam generators and reactor face. The model links corrosion of the carbon steel outlet feeders to magnetite and radionuclide deposition on steam generator and inlet piping surfaces. This paper will describe the model development, key assumptions, required inputs, and model validation. The importance of reactor artefact characterization in the model development will be highlighted, and some key results will be presented, including oxide morphology and loadings, and radionuclide distributions within the oxide. The predictive capabilities of the model will also be described, including predictions of oxide thickness and the effects of changes in chemistry parameters such as alkalinity. While the model was developed primarily for the CANDU® HTS, the information gained during model development regarding corrosion product and radionuclide transport and deposition can also provide insights into activity transport in other water-cooled reactor systems. (author)
Heat transfer modeling of double-side arc welding
Sun Jun Sheng; Zhang Yan Ming
2002-01-01
If a plasma arc and a TIG arc are connected in serial and with the plasma arc placed on the obverse side and the TIG arc on the opposite side of the workpiece, a special double-side arc welding (DSAW) system will be formed, in which the PAW current is forced to flow through the keyhole along the thickness direction so as to compensate the energy consumed for melting the workpiece and improve the penetration capacity of the PAW arc. By considering the mechanics factors which influence the DSAW pool geometric shape, the control equations of the pool surface deformation are derived, and the mathematics mode for DSAW heat transfer is established by using boundary-fitted non-orthogonal coordinate systems. With this model, the difference between DSAW and PAW heat transfer is analyzed and the reason for the increase of DSAW penetration is explained from the point of heat transfer. The welding process experiments show that calculated results are in good agreement with measured ones
National Research Council Canada - National Science Library
Longo, Cristiano; Leo, Lucia; Leone, Antonella
2012-01-01
.... We compared two S-CO(2)-extracted oleoresins (from tomato and tomato/hazelnut matrices), which showed an oil-solid bi-phasic appearance, a higher cis-lycopene content, and enhanced antioxidant ability compared with the traditional solvent extracts...
DEFF Research Database (Denmark)
Mohammadi, Soma; Bojesen, Carsten
2015-01-01
Increasing the building energy efficiency in recent years results in noticeably reduction in their heating demand. Combined with the current trend for utilizing low temperature heat sources, it raises the necessity of introducing a new generation of district heating [DH] systems with lowered...
A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation
Lee, C. K.
2014-01-01
This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that PSETs…
Seven Operation Modes and Simulation Models of Solar Heating System with PCM Storage Tank
Directory of Open Access Journals (Sweden)
Juan Zhao
2017-12-01
Full Text Available A physical model and dynamic simulation models of a solar phase-change heat storage heating system with a plate solar collector, phase-change material (PCM storage tank, plate heat exchanger, and auxiliary heat sources were established. A control strategy and numerical models for each of seven different operation modes that cover the entire heating season of the system were developed for the first time. The seven proposed operation modes are Mode 1: free cooling; Mode 2: reservation of heat absorbed by the solar collector in the PCM storage tank when there is no heating demand; Mode 3: direct supply of the heating demand by the solar collector; Mode 4: use of the heat absorbed by the solar collector to meet the heating demands, with the excess heat stored in the PCM storage tank; Mode 5: use of heat stored in the PCM storage tank to meet the heating demands, Mode 6: combined use of heat stored in the PCM storage tank and the auxiliary heating sources to meet the heating demands; and Mode 7: exclusive use of the auxiliary heat sources in order to meet the heating demands. Mathematical models were established for each of the above seven operation modes, taking into consideration the effects of the outdoor meteorological parameters and terminal load on the heating system. The real-time parameters for the entire heating season of the system with respect to the different operation modes can be obtained by solving the simulation models, and used as reference for the optimal design and operation of the actual system.
Energy Technology Data Exchange (ETDEWEB)
Mohd Fauzi, Noor Akhmazillah bt [Chemical and Bioprocess Department, Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor (Malaysia); Sarmidi, Mohd Roji [Chemical Engineering Pilot Plant, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia)
2011-07-01
An investigation was carried out on the effect of different sterilization time on the trace metals concentration of palm oil whole extract. Palm fruits were collected, cleaned and sterilized for 0, 20, 40 and 60 minutes. The kernels were then stripped from the sterilized fruits to get the pulp and later the pulp was pressed using small scale expeller. The resulting puree was centrifuge at 4000 rpm for 20 minutes. The palm oil whole extract were then collected and trace metals analysis was conducted using Inductively Couple Plasma-Mass Spectrometry (ICP-MS). The result showed that the highest yield was obtained at 40 minutes of sterilization with 19.9 {+-} 0.21 % (w/w). There was no significant different (p < 0.5) in total trace metals content between the degrees of the heat treatment. Na+ was found as the highest trace metals content in the extract with mean concentration ranging from 1.05 {+-} 0.03 ppm to 2.36 {+-} 0.01 ppm. 40 minutes of heating time was predicted to have good oil quality due to higher content in trace metals that inhibit the lipase enzyme activity.
Model-based Bayesian signal extraction algorithm for peripheral nerves
Eggers, Thomas E.; Dweiri, Yazan M.; McCallum, Grant A.; Durand, Dominique M.
2017-10-01
Objective. Multi-channel cuff electrodes have recently been investigated for extracting fascicular-level motor commands from mixed neural recordings. Such signals could provide volitional, intuitive control over a robotic prosthesis for amputee patients. Recent work has demonstrated success in extracting these signals in acute and chronic preparations using spatial filtering techniques. These extracted signals, however, had low signal-to-noise ratios and thus limited their utility to binary classification. In this work a new algorithm is proposed which combines previous source localization approaches to create a model based method which operates in real time. Approach. To validate this algorithm, a saline benchtop setup was created to allow the precise placement of artificial sources within a cuff and interference sources outside the cuff. The artificial source was taken from five seconds of chronic neural activity to replicate realistic recordings. The proposed algorithm, hybrid Bayesian signal extraction (HBSE), is then compared to previous algorithms, beamforming and a Bayesian spatial filtering method, on this test data. An example chronic neural recording is also analyzed with all three algorithms. Main results. The proposed algorithm improved the signal to noise and signal to interference ratio of extracted test signals two to three fold, as well as increased the correlation coefficient between the original and recovered signals by 10–20%. These improvements translated to the chronic recording example and increased the calculated bit rate between the recovered signals and the recorded motor activity. Significance. HBSE significantly outperforms previous algorithms in extracting realistic neural signals, even in the presence of external noise sources. These results demonstrate the feasibility of extracting dynamic motor signals from a multi-fascicled intact nerve trunk, which in turn could extract motor command signals from an amputee for the end goal of
A New Self-Heating Bipolar Transistor Spice Model
Pintacuda, Francesco; Cavallaro, Daniela; Bazzano, Gaetano
2011-10-01
Self-heating effects in Bipolar Junction Transistors have been incorporated into SPICE through sub-circuits including a thermal model. It contains a dynamic link between electrical and thermal components which allows a good prediction of DC and AC variation due to temperature in the range of the component (-55 C to 150C). It allows the estimation of the junction-temperature when the device is working in the power application. An example of thermal transient simulation is presented showing the thermal effects in a typical circuit configuration.
The balance model for heat transport from hydrolytic reaction mixture
Directory of Open Access Journals (Sweden)
Janacova Dagmar
2017-01-01
Full Text Available The content of the paper is the industrial application of enzyme hydrolysis of tanning solids waste with a view to minimizing the price of enzyme hydrolysate product, which has widely used. On the base of the energy balance of the enzymatic hydrolysis we estimated the critical minimal charge of a tanning drum. We performed of the critical minimal on the basis of a balance model for heat transport from reaction mixture into the environment through reactor wall. Employing a tanning drum for hydrolytic reaction allows to process tanning wastes in the place of their origin. It means thus considerably to enhancing economics of the whole process.
Hybrid fluid/kinetic model for parallel heat conduction
Energy Technology Data Exchange (ETDEWEB)
Callen, J.D.; Hegna, C.C.; Held, E.D. [Univ. of Wisconsin, Madison, WI (United States)
1998-12-31
It is argued that in order to use fluid-like equations to model low frequency ({omega} < {nu}) phenomena such as neoclassical tearing modes in low collisionality ({nu} < {omega}{sub b}) tokamak plasmas, a Chapman-Enskog-like approach is most appropriate for developing an equation for the kinetic distortion (F) of the distribution function whose velocity-space moments lead to the needed fluid moment closure relations. Further, parallel heat conduction in a long collision mean free path regime can be described through a combination of a reduced phase space Chapman-Enskog-like approach for the kinetics and a multiple-time-scale analysis for the fluid and kinetic equations.
Modeling of Heat Transfer in LDConverter (BOF) Lining
Jahan, Georgina
2012-01-01
During the production of steel in the LD converter the refractory lining is exposed to high temperature emulsion of steel, slag and gas. It protects the steel body of the vessel to come in contact with the molten steel.The main purpose of this work was to observe the temperature distribution profile in converter refractory lining which is very important to understand the life of the refractory lining of the LD converter.In this study, a three dimensional (3D) heat transfer model for the refra...
Validation of an extracted tooth model of endodontic irrigation.
Hope, C K; Burnside, G; Chan, S N; Giles, L H; Jarad, F D
2011-01-01
An extracted tooth model of endodontic irrigation, incorporating reproducible inoculation and irrigation procedures, was tested against Enterococcus faecalis using a variety of different irrigants in a Latin square methodology. ANOVA revealed no significant variations between the twelve teeth or experiments undertaken on different occasions; however, variation between irrigants was significant. Copyright © 2010 Elsevier B.V. All rights reserved.
Building extraction for 3D city modelling using airborne laser ...
African Journals Online (AJOL)
Light detection and ranging (LiDAR) technology has become a standard tool for three-dimensional mapping because it offers fast rate of data acquisition with unprecedented level of accuracy. This study presents an approach to accurately extract and model building in three-dimensional space from airborne laser scanning ...
Energy Technology Data Exchange (ETDEWEB)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.
1995-09-01
RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.
Modelling and performance of heat pipes with long evaporator sections
Wits, Wessel W.; te Riele, Gert Jan
2017-01-01
This paper presents a planar cooling strategy for advanced electronic applications using heat pipe technology. The principle idea is to use an array of relatively long heat pipes, whereby heat is disposed to a long section of the pipes. The proposed design uses 1 m long heat pipes and top cooling
Modelling of Split Condenser Heat Pump with Limited Set of Plate Heat Exchanger Dimensions
DEFF Research Database (Denmark)
Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix
2017-01-01
in parallel to different temperature levels, whereas only one stream is heated in a THP. The length/width ratio of the plate heat exchangers on the high pressure side of a SCHP was investigated to find the optimal plate dimensions with respect to minimum area of the heat exchangers. The total heat exchanger...... area was found to decrease with an increasing length/width ratio of the plates. The marginal change in heat exchanger area was shown to be less significant for heat exchangers with high length/width ratios. In practice only a limited number of plate dimensions are available and feasible...... in the production. This was investigated to find the practical potential of a SCHP compared to a THP. Using plates optimized for a SCHP in a THP, the total required heat exchanger area increased by approximately 100% for the conditions investigated in this study, indicating that available plate dimensions influence...
Energy Technology Data Exchange (ETDEWEB)
Afanas' ev, A.A.; Borisov, V.P.; Grebennikov, V.N.; Dolinin, E.L.; Krutikov, P.G.; Shishkunov, V.A.; Stogov, V.I.
1984-02-01
Test results of network heat exchanger model of a nuclear boiler plant AST-500 with a tube part of 08Kh14MF ferritic-martensitic steel are presented. The model presents a one-through counterflow water-water heat-exchanger. The model was connected to the district heating network where it operated for 5000 hr at pH=7.3 and at the temperature 70-90 deg C. Rolled joints ''tube-tube sheet'' did not have traces of contact corrosion, gradual corrosion of 08Kh14MF steel did not exceed 0 003 mm/year, which ensured normal working capacity of heat-exchanger equipment for the planned 30 years.
X-ray studies of interfacial strontium-extractant complexes in a model solvent extraction system.
Bu, Wei; Mihaylov, Miroslav; Amoanu, Daniel; Lin, Binhua; Meron, Mati; Kuzmenko, Ivan; Soderholm, L; Schlossman, Mark L
2014-10-30
The interfacial behavior of a model solvent extraction liquid-liquid system, consisting of solutions of dihexadecyl phosphate (DHDP) in dodecane and SrCl2 in water, was studied to determine the structure of the interfacial ion-extractant complex and its variation with pH. Previous experiments on a similar extraction system with ErCl3 demonstrated that the kinetics of the extraction process could be greatly retarded by cooling through an adsorption transition, thus providing a method to immobilize ion-extractant complexes at the interface and further characterize them with X-ray interface-sensitive techniques. Here, we use this same method to study the SrCl2 system. X-ray reflectivity and fluorescence near total reflection measured the molecular-scale interfacial structure above and below the adsorption transition for a range of pH. Below the transition, DHDP molecules form a homogeneous monolayer at the interface with Sr(2+) coverage increasing from zero to saturation (one Sr(2+) per two DHDP) within a narrow range of pH. Experimental values of Sr(2+) interfacial density determined from fluorescence measurements are larger than those from reflectivity measurements. Although both techniques probe Sr(2+) bound to DHDP, only the fluorescence provides adequate sensitivity to Sr(2+) in the diffuse double layer. A Stern equation determines the Sr(2+) binding constant from the reflectivity measurements and the additional Sr(2+) measured in the diffuse double layer is accounted for by Gouy-Chapman theory. Above the transition temperature, a dilute concentration of DHDP-Sr complexes resides at the interface, even for temperatures far above the transition. A comparison is made of the structure of the interfacial ion-extractant complex for this divalent metal ion to recent results on trivalent Er(3+) metal ions, which provides insight into the role of metal ion charge on the structure of interfacial ion-extractant complexes, as well as implications for extraction of these two
MODELING AND SIMULATION OF A BENZENE RECOVERY PROCESS BY EXTRACTIVE DISTILLATION
Directory of Open Access Journals (Sweden)
L. B. Brondani
2015-03-01
Full Text Available Abstract Extractive distillation processes with N-formylmorpholine (NFM are used industrially to separate benzene from six carbon non-aromatics. In the process studied in this work, the stream of interest consists of nearly 20 different hydrocarbons. A new set of NRTL parameters was correlated based on literature experimental data. Both vapor-liquid equilibrium as well as infinite dilution activity coefficient data were taken into account; missing parameters were estimated with the UNIFAC group contribution model. The extractive distillation process was simulated using ASPEN Plus®. Very good agreement with plant data was obtained. The influences of the main operational parameters, solvent to feed ratio and solvent temperature, were studied. Theoretical optimum operating values were obtained and can be implemented to improve the industrial process. Extreme static sensitivity with respect to reboiler heat was observed, indicating that this can be the source of instabilities.
A miniswine model of acute exertional heat exhaustion.
Gentile, B J; Szlyk-Modrow, P C; Durkot, M J; Krestel, B A; Sils, I V; Tartarini, K A; Alkhyyat, A M
1996-06-01
We examined the thermoregulatory and hemodynamic responses of 12 miniswine (31 +/- 3.9 kg) during 25-30 min of treadmill exercise (5.4 km.h-1, 5% grade) under cool (10 degrees C), moderate (20 degrees C) and warm (30 degrees C) ambient temperature (Ta) conditions. Within 15-20 min of exercise at Ta = 30 degrees C, the miniswine demonstrated significant hyperventilation, hypersalivation, and unsteady gait. Exercise-heat endurance time (T) at Ta = 30 degrees C decreased by 35% and 40% in comparison to T at Ta = 20 degrees C and 10 degrees C, respectively. This resulted from a significant rise in heat strain (S)-defined as the rate of change in rectal temperature. Averaged throughout exercise, S increased from 0.04 +/- 0.01 degree C.min-1 and 0.05 +/- 0.02 degree C.min-1 at Ta = 10 degrees C and 20 degrees C, respectively, to 0.10 +/- 0.03 degree C.min-1 at Ta = 30 degrees C. Due to the comparatively large storage capacity of the porcine spleen relative to humans, splenectomized miniswine were used. This permitted calculation of percentage changes in plasma volume (% delta PVc) from hematocrit (HCT) and hemoglobin (HGB) without the confounding effects of splenic red cells released into the circulation during exercise. Independent of Ta, pre-exercise PVc decreased 3%-5% (p post-exercise. We conclude that the poor thermoregulatory ability of miniswine manifested in insignificant sweating and restricted evaporative cooling, may make them an appropriate model for acute exertional heat exhaustion in humans working in hot, humid conditions and/or wearing impermeable protective clothing. Further, evaluation of plasma volume changes from HCT and HGB in a miniswine model should consider the merit of a splenectomized design.
Heat-Killed Enterococcus faecalis EF-2001 Ameliorates Atopic Dermatitis in a Murine Model.
Choi, Eun-Ju; Iwasa, Masahiro; Han, Kwon-Il; Kim, Wan-Jae; Tang, Yujiao; Hwang, Young Joung; Chae, Jeong Ryong; Han, Weon Cheol; Shin, Yu-Su; Kim, Eun-Kyung
2016-03-05
Recent reports have shown the immunomodulatory effect of heat-killed lactic acid bacteria. Atopic dermatitis (AD) is an allergic skin disease, caused by immune dysregulation among other factors. The aim of this study was to assess the effect of heat-killed Enterococcus faecalis EF-2001 (EF-2001) on AD. We established an in vivo AD model by repeated local exposure of Dermatophagoides farinae extract (DFE; house dust mite extract) and 2,4-dinitrochlorobenzene (DNCB) to the ears of mice. After oral administration of EF-2001 for four weeks, the epidermal and dermal ear thickness, mast cell infiltration, and serum immunoglobulin levels were measured. In addition, the gene expression levels of pathogenic cytokines in the ears, lymph nodes, and splenocytes were assayed. EF-2001 attenuated AD symptoms based on the ear thickness, histopathological analysis, and serum immunoglobulin levels. Moreover, EF-2001 decreased the DFE/DNCB-induced expression of various pathogenic cytokines in the ears, lymph nodes, and splenocytes. These results suggest that EF-2001 has therapeutic potential in the treatment of AD owing to its immunomodulatory effects.
Heat-Killed Enterococcus faecalis EF-2001 Ameliorates Atopic Dermatitis in a Murine Model
Directory of Open Access Journals (Sweden)
Eun-Ju Choi
2016-03-01
Full Text Available Recent reports have shown the immunomodulatory effect of heat-killed lactic acid bacteria. Atopic dermatitis (AD is an allergic skin disease, caused by immune dysregulation among other factors. The aim of this study was to assess the effect of heat-killed Enterococcus faecalis EF-2001 (EF-2001 on AD. We established an in vivo AD model by repeated local exposure of Dermatophagoides farinae extract (DFE; house dust mite extract and 2,4-dinitrochlorobenzene (DNCB to the ears of mice. After oral administration of EF-2001 for four weeks, the epidermal and dermal ear thickness, mast cell infiltration, and serum immunoglobulin levels were measured. In addition, the gene expression levels of pathogenic cytokines in the ears, lymph nodes, and splenocytes were assayed. EF-2001 attenuated AD symptoms based on the ear thickness, histopathological analysis, and serum immunoglobulin levels. Moreover, EF-2001 decreased the DFE/DNCB-induced expression of various pathogenic cytokines in the ears, lymph nodes, and splenocytes. These results suggest that EF-2001 has therapeutic potential in the treatment of AD owing to its immunomodulatory effects.
Zhang, Jianbo; Ge, Hao; Li, Zhe; Ding, Zhanming
2015-01-01
This study develops a method to internally preheat lithium-ion batteries at low temperatures with sinusoidal alternating current (AC). A heat generation rate model in frequency domain is developed based on the equivalent electrical circuit. Using this model as the source term, a lumped energy conservation model is adopted to predict the temperature rise. These models are validated against the experimental results of preheating an 18650 cell at different thermal insulation conditions. The effects of current amplitude and frequency on the heating rate are illustrated with a series of simulated contours of heating time. These contours indicate that the heating rate increases with higher amplitude, lower frequency and better thermal insulation. The cell subjected to an alternating current with an amplitude of 7 A (2.25 C) and a frequency of 1 Hz, under a calibrated heat transfer coefficient of 15.9 W m-2 K-1, can be heated from -20 °C to 5 °C within 15 min and the temperature distribution remains essentially uniform. No capacity loss is found after repeated AC preheating tests, indicating this method incurs little damage to the battery health. These models are computationally-efficient and can be used in real time to control the preheating devices in electric vehicles.
Silva, Humberto R; Phelan, Patrick E; Golden, Jay S
2010-01-01
A zero-dimensional energy balance model was previously developed to serve as a user-friendly mitigation tool for practitioners seeking to study the urban heat island (UHI) effect. Accordingly, this established model is applied here to show the relative effects of four common mitigation strategies: increasing the overall (1) emissivity, (2) percentage of vegetated area, (3) thermal conductivity, and (4) albedo of the urban environment in a series of percentage increases by 5, 10, 15, and 20% from baseline values. In addition to modeling mitigation strategies, we present how the model can be utilized to evaluate human health vulnerability from excessive heat-related events, based on heat-related emergency service data from 2002 to 2006. The 24-h average heat index is shown to have the greatest correlation to heat-related emergency calls in the Phoenix (Arizona, USA) metropolitan region. The four modeled UHI mitigation strategies, taken in combination, would lead to a 48% reduction in annual heat-related emergency service calls, where increasing the albedo is the single most effective UHI mitigation strategy.
Rossmann, Christian; McCrackin, M A; Armeson, Kent E; Haemmerich, Dieter
2017-01-01
Temperature sensitive liposomes (TSL) are nanoparticles that rapidly release the contained drug at hyperthermic temperatures, typically above ~40°C. TSL have been combined with various heating modalities, but there is no consensus on required hyperthermia duration or ideal timing of heating relative to TSL administration. The goal of this study was to determine changes in drug uptake when heating duration and timing are varied when combining TSL with radiofrequency ablation (RF) heating. We used computer models to simulate both RF tissue heating and TSL drug delivery, to calculate spatial drug concentration maps. We simulated heating for 5, 12 and 30 min for a single RF electrode, as well as three sequential 12 min ablations for 3 electrodes placed in a triangular array. To support simulation results, we performed porcine in vivo studies in normal liver, where TSL filled with doxorubicin (TSL-Dox) at a dose of 30 mg was infused over 30 min. Following infusion, RF heating was performed in separate liver locations for either 5 min (n = 2) or 12 min (n = 2). After ablation, the animal was euthanized, and liver extracted and frozen. Liver samples were cut orthogonal to the electrode axis, and fluorescence imaging was used to visualize tissue doxorubicin distribution. Both in vivo studies and computer models demonstrate a ring-shaped drug deposition within ~1 cm of the visibly coagulated tissue. Drug uptake directly correlated with heating duration. In computer simulations, drug concentration increased by a factor of 2.2x and 4.3x when heating duration was extended from 5 to either 12, or 30 minutes, respectively. In vivo, drug concentration was by a factor of 2.4x higher at 12 vs 5 min heating duration (7.1 μg/g to 3.0 μg/g). The computer models suggest that heating should be timed to maximize area under the curve of systemic plasma concentration of encapsulated drug. Both computer models and in vivo study demonstrate that tissue drug uptake directly correlates with
Building footprint extraction from digital surface models using neural networks
Davydova, Ksenia; Cui, Shiyong; Reinartz, Peter
2016-10-01
Two-dimensional building footprints are a basis for many applications: from cartography to three-dimensional building models generation. Although, many methodologies have been proposed for building footprint extraction, this topic remains an open research area. Neural networks are able to model the complex relationships between the multivariate input vector and the target vector. Based on these abilities we propose a methodology using neural networks and Markov Random Fields (MRF) for automatic building footprint extraction from normalized Digital Surface Model (nDSM) and satellite images within urban areas. The proposed approach has mainly two steps. In the first step, the unary terms are learned for the MRF energy function by a four-layer neural network. The neural network is learned on a large set of patches consisting of both nDSM and Normalized Difference Vegetation Index (NDVI). Then prediction is performed to calculate the unary terms that are used in the MRF. In the second step, the energy function is minimized using a maxflow algorithm, which leads to a binary building mask. The building extraction results are compared with available ground truth. The comparison illustrates the efficiency of the proposed algorithm which can extract approximately 80% of buildings from nDSM with high accuracy.
Numerical modeling of transient heat transfer in microsystem of protective clothing
Directory of Open Access Journals (Sweden)
Du Min-Zhi
2016-01-01
Full Text Available Heat protective clothing is always being treated as a main personal protective equipment to shield robust flame injection and high temperature, therefore, it is significant and essential to investigate transient heat transfer and heat insulation ability of heat protective clothing. In this paper, a novel co-operative model composed of heat protective clothing, air gap, and test sensor was established under the convection and radiation heat source, and the temperature and heat flux were numerically solved by finite element method. The results showed an acceptable agreement between the experimental data and numerical prediction.
The Mathematical Modelling of Heat Transfer in Electrical Cables
Directory of Open Access Journals (Sweden)
Bugajev Andrej
2014-05-01
Full Text Available This paper describes a mathematical modelling approach for heat transfer calculations in underground high voltage and middle voltage electrical power cables. First of the all typical layout of the cable in the sand or soil is described. Then numerical algorithms are targeted to the two-dimensional mathematical models of transient heat transfer. Finite Volume Method is suggested for calculations. Different strategies of nonorthogonality error elimination are considered. Acute triangles meshes were applied in two-dimensional domain to eliminate this error. Adaptive mesh is also tried. For calculations OpenFOAM open source software which uses Finite Volume Method is applied. To generate acute triangles meshes aCute library is used. The efficiency of the proposed approach is analyzed. The results show that the second order of convergence or close to that is achieved (in terms of sizes of finite volumes. Also it is shown that standard strategy, used by OpenFOAM is less efficient than the proposed approach. Finally it is concluded that for solving real problem a spatial adaptive mesh is essential and adaptive time steps also may be needed.
Heat Redistribution and Misaligned Orbit Models in PHOEBE
Horvat, Martin; Prsa, Andrej; Conroy, Kyle E.
2017-01-01
Reflection and aligned Roche geometry have been long supported in modeling codes that synthesize light and radial velocity curves of eclipsing binary stars. However, recent advances in observational data, mostly in terms of precision and temporal baseline, demonstrated that the assumptions of these two effects are frequently violated. Reflection treatment neglected the energy absorbed by the irradiated star, and Roche geometry assumed aligned vectors of spin and orbital angular momentum. Observations of night- and day-side brightness variation of cooler stellar and substellar companions point to a clear deficiency in treating heat redistribution, and the break in symmetry of the Rossiter-McLaughlin effect points to misaligned stellar spins w.r.t. orbital plane. The framework of existing codes did not allow for revising these effects while keeping the rest of the logic intact, which prompted a complete rewrite of the modeling code PHOEBE (PHysics Of Eclipsing BinariEs). Here we present the basic considerations and proof-of-concept examples of the revised reflection effect and misaligned spin-orbit support. Reflection has been extended with heat absorption and consequent redistribution, which can be local, longitudinal or global. Misaligned spin-orbit vectors are supported by deriving the equation of the Roche potential that allows misaligned rotational axes and are provided by the corresponding Euler angles. This research is supported by the NSF grant #1517474.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For large thickness dimensions the resulting heat transfer through the
Supercritical extraction of carqueja essential oil: experiments and modeling
Directory of Open Access Journals (Sweden)
R. M. F. Vargas
2006-09-01
Full Text Available Baccharis trimera is a native Brazilian plant which has medicinal properties. In this work a method of supercritical extraction was studied to obtain the popularly essential oil from Baccharis trimera, known as carqueja. The aim was to obtain experimental data and to compare two mathematical models used in the simulation of carqueja (Baccharis trimera oil extraction by supercritical CO2. The two mathematical models are based on mass transfer. One of the models, proposed by Reverchon, is solved numerically and requires two adjustable parameters from the experimental data. The other model chosen is the one proposed by Sovová. This model is solved analytically and requires four adjustable parameters. Numerical results are presented and discussed for the adjusted parameters. The experimental results are obtained in a temperature range of 313.15 K to 343.15 K at 90 bar. The extraction yield of carqueja essential oil using supercritical carbon dioxide ranged between 1.72 % (w/w at 323.15 K and 2.34 % (w/w at 343.15 K, 90 bar with a CO2 flow rate of 3.34.10-8 m³/s for a 0.0015 kg sample of Baccharis trimera.
Dynamic friction modelling in heat exchanger tube simulations
Energy Technology Data Exchange (ETDEWEB)
Tan, X.; Rogers, R.J. [Univ. of New Brunswick, Fredericton, New Brunswick (Canada). Dept. of Mechanical Engineering
1996-12-01
A force-balance friction model has been developed to describe dynamic friction phenomena in multi-degree of freedom vibration systems and validated for a two degree-of-freedom (2dof) lumped mass vibration system. It has been implemented into VIBIC, a finite element code for the vibration of beams with intermittent contact, to improve the prediction of tube wear rate in the simulation of shell-and-tube heat exchangers. The friction model has been tailored for VIBIC for various kinds of supports: circular, semi-circular scallop-bar, and arbitrary flat-bar supports. Simulations for single fuel pin vibration have been compared with experimental data on wear work rate for different test conditions, gaps and preloads.
Saturated-liquid heat capacity of organic compounds: new empirical correlation model
Directory of Open Access Journals (Sweden)
DUSAN K. GROZDANIC
2004-03-01
Full Text Available A new saturated-liquid heat capacity model is recommended. This model is tested and compared with the known polynomial and quasi-polynomial models on 39 sets with 1453 experimental heat capacity data. The obtained results indicate that the new model is better then the existing models, especially near the critical point.
Ramazanov, M. M.; Alkhasova, D. A.; Abasov, G. M.
2017-05-01
With the use of the finite-difference method, a nonstationary nonlinear problem on the heat and mass transfer in a geothermal bed in the process of extraction of a vapor-water mixture from it was solved numerically with regard for the heat exchange between the bed and the surrounding rocks. The results obtained were analyzed and compared with the results of earlier investigations. It was established that the heat exchange between the bed and its roof and bottom influences the heat and mass transfer in the neighborhood of a producing well in it. It is shown that this heat exchange increases somewhat the pressure (temperature) of the phase transition of the heat-transfer medium and changes its saturation with water. At the stage of stationary heat and mass transfer in the bed, this change leads to a decrease in the water saturation of the heat-transfer medium, i.e., to an additional evaporation of water from it. However, at the stage of substantially nonstationary heat and mass transfer in the bed, the pattern is more complex: within certain time intervals, the heat exchange in separate regions of the bed decreases the content of vapor in the heat-transfer medium (increases its saturation with water). Moreover, in both the cases of absence and presence of heat exchange between the bed and the surrounding rocks, the distributions of the water saturation of the heat-transfer medium in the bed executes damped oscillations and, in so doing, approaches the stationary state.
A heating agent using a personalised thermal comfort model to Save energy
Auffenberg, Frederik; Stein, Sebastian; Rogers, Alex
2015-01-01
We present a novel, personalised thermal comfort model anda heating agent using this model to reduce energy consump-tion with minimal comfort loss. At present, heating agentstypically use simple models of user comfort when decidingon a set point temperature for the heating or cooling system.These models however generally fail to adapt to an individ-ual user's preferences, resulting in poor performance. Toaddress this issue, we propose a personalised thermal com-fort model using a Bayesian net...
Energy Technology Data Exchange (ETDEWEB)
Forristall, R.
2003-10-01
This report describes the development, validation, and use of a heat transfer model implemented in Engineering Equation Solver. The model determines the performance of a parabolic trough solar collector's linear receiver, also called a heat collector element. All heat transfer and thermodynamic equations, optical properties, and parameters used in the model are discussed. The modeling assumptions and limitations are also discussed, along with recommendations for model improvement.
Three dimensional heat transport modeling in Vossoroca reservoir
Arcie Polli, Bruna; Yoshioka Bernardo, Julio Werner; Hilgert, Stephan; Bleninger, Tobias
2017-04-01
Freshwater reservoirs are used for many purposes as hydropower generation, water supply and irrigation. In Brazil, according to the National Energy Balance of 2013, hydropower energy corresponds to 70.1% of the Brazilian demand. Superficial waters (which include rivers, lakes and reservoirs) are the most used source for drinking water supply - 56% of the municipalities use superficial waters as a source of water. The last two years have shown that the Brazilian water and electricity supply is highly vulnerable and that improved management is urgently needed. The construction of reservoirs affects physical, chemical and biological characteristics of the water body, e.g. stratification, temperature, residence time and turbulence reduction. Some water quality issues related to reservoirs are eutrophication, greenhouse gas emission to the atmosphere and dissolved oxygen depletion in the hypolimnion. The understanding of the physical processes in the water body is fundamental to reservoir management. Lakes and reservoirs may present a seasonal behavior and stratify due to hydrological and meteorological conditions, and especially its vertical distribution may be related to water quality. Stratification can control heat and dissolved substances transport. It has been also reported the importance of horizontal temperature gradients, e.g. inflows and its density and processes of mass transfer from shallow to deeper regions of the reservoir, that also may impact water quality. Three dimensional modeling of the heat transport in lakes and reservoirs is an important tool to the understanding and management of these systems. It is possible to estimate periods of large vertical temperature gradients, inhibiting vertical transport and horizontal gradients, which could be responsible for horizontal transport of heat and substances (e.g. differential cooling or inflows). Vossoroca reservoir was constructed in 1949 by the impoundment of São João River and is located near to
Abdominal wall extraction using constrained deformable model and abdominal context.
Huang, Weimin; Quan, Lijie; Lin, Zhiping; Duan, Yuping; Zhou, Jiayin; Yang, Yongzhong; Xiong, Wei
2014-01-01
Information about abdominal wall can be used for many applications from organ segmentation, registration, and surgical simulation. The challenges exist in abdominal wall extraction due to its varieties in shapes, connection to the internal organs and anterior layer edge formed between the muscle and fascia/fatty layer, which may distract the shape model. In this paper we present an approach to the posterior abdominal wall extraction using the shape model and other abdominal context, particularly with the rib-spine bone information and the wall image features. The shape model is constructed based on the training abdominal walls that are delineated manually. After bone information being extracted, the wall shape deforms from the prior shape model using the snake, which is constrained by the bone context and guided by the processed image energy map with the aim of removing distracted image features of anterior abdominal wall and the outer region from the original map. Meanwhile, an overall convex shape is maintained by limiting the angles of the contour points. The proposed approach is tested on abdominal CT data which provides encouraging results.
Heat and Bleach: A Cost-Efficient Method for Extracting Microplastics from Return Activated Sludge.
Sujathan, Surya; Kniggendorf, Ann-Kathrin; Kumar, Arun; Roth, Bernhard; Rosenwinkel, Karl-Heinz; Nogueira, Regina
2017-11-01
The extraction of plastic microparticles, so-called microplastics, from sludge is a challenging task due to the complex, highly organic material often interspersed with other benign microparticles. The current procedures for microplastic extraction from sludge are time consuming and require expensive reagents for density separation as well as large volumes of oxidizing agents for organic removal, often resulting in tiny sample sizes and thus a disproportional risk of sample bias. In this work, we present an improved extraction method tested on return activated sludge (RAS). The treatment of 100 ml of RAS requires only 6% hydrogen peroxide (H2O2) for bleaching at 70 °C, followed by density separation with sodium nitrate/sodium thiosulfate (SNT) solution, and is completed within 24 h. Extracted particles of all sizes were chemically analyzed with confocal Raman microscopy. An extraction efficiency of 78 ± 8% for plastic particle sizes 20 µm and up was confirmed in a recovery experiment. However, glass shards with a diameter of less than 20 µm remained in the sample despite the density of glass exceeding the density of the separating SNT solution by 1.1 g/cm3. This indicates that density separation may be unreliable for particle sizes in the lower micrometer range.
Energy Technology Data Exchange (ETDEWEB)
Kenkeremath, D. (ed.)
1985-05-01
Numerical simulation models and data bases that were developed for DOE as part of a number of geothermal programs have been assessed with respect to their overall stage of development and usefulness. This report combines three separate studies that focus attention upon: (1) economic models related to geothermal energy; (2) physical geothermal system models pertaining to thermal energy and the fluid medium; and (3) geothermal energy data bases. Computerized numerical models pertaining to the economics of extracting and utilizing geothermal energy have been summarized and catalogued with respect to their availability, utility and function. The 19 models that are discussed in detail were developed for use by geothermal operators, public utilities, and lending institutions who require a means to estimate the value of a given resource, total project costs, and the sensitivity of these values to specific variables. A number of the models are capable of economically assessing engineering aspects of geothermal projects. Computerized simulations of heat distribution and fluid flow have been assessed and are presented for ten models. Five of the models are identified as wellbore simulators and five are described as reservoir simulators. Each model is described in terms of its operational characteristics, input, output, and other pertinent attributes. Geothermal energy data bases are reviewed with respect to their current usefulness and availability. Summaries of eight data bases are provided in catalogue format, and an overall comparison of the elements of each data base is included.
Modelling of convective heat and mass transfer in rotating flows
Shevchuk, Igor V
2016-01-01
This monograph presents results of the analytical and numerical modeling of convective heat and mass transfer in different rotating flows caused by (i) system rotation, (ii) swirl flows due to swirl generators, and (iii) surface curvature in turns and bends. Volume forces (i.e. centrifugal and Coriolis forces), which influence the flow pattern, emerge in all of these rotating flows. The main part of this work deals with rotating flows caused by system rotation, which includes several rotating-disk configurations and straight pipes rotating about a parallel axis. Swirl flows are studied in some of the configurations mentioned above. Curvilinear flows are investigated in different geometries of two-pass ribbed and smooth channels with 180° bends. The author demonstrates that the complex phenomena of fluid flow and convective heat transfer in rotating flows can be successfully simulated using not only the universal CFD methodology, but in certain cases by means of the integral methods, self-similar and analyt...
The Oak Ridge Heat Pump Models: I. A Steady-State Computer Design Model of Air-to-Air Heat Pumps
Energy Technology Data Exchange (ETDEWEB)
Fischer, S.K. Rice, C.K.
1999-12-10
The ORNL Heat Pump Design Model is a FORTRAN-IV computer program to predict the steady-state performance of conventional, vapor compression, electrically-driven, air-to-air heat pumps in both heating and cooling modes. This model is intended to serve as an analytical design tool for use by heat pump manufacturers, consulting engineers, research institutions, and universities in studies directed toward the improvement of heat pump performance. The Heat Pump Design Model allows the user to specify: system operating conditions, compressor characteristics, refrigerant flow control devices, fin-and-tube heat exchanger parameters, fan and indoor duct characteristics, and any of ten refrigerants. The model will compute: system capacity and COP (or EER), compressor and fan motor power consumptions, coil outlet air dry- and wet-bulb temperatures, air- and refrigerant-side pressure drops, a summary of the refrigerant-side states throughout the cycle, and overall compressor efficiencies and heat exchanger effectiveness. This report provides thorough documentation of how to use and/or modify the model. This is a revision of an earlier report containing miscellaneous corrections and information on availability and distribution of the model--including an interactive version.
Central model predictive control of a group of domestic heat pumps, case study for a small district
van Leeuwen, Richard Pieter; Fink, J.; Smit, Gerardus Johannes Maria; Helfert, Markus; Krempels, Karl-Heinz; Donnellan, Brian; Klein, Cornel
2015-01-01
In this paper we investigate optimal control of a group of heat pumps. Each heat pump provides space heating and domestic hot water to a single household. Besides a heat pump, each house has a buffer for domestic hot water and a floor heating system for space heating. The paper describes models and
A heat exchanger model for air-to-refrigerant fin-and-tube heat exchanger with arbitrary fin sheet
Energy Technology Data Exchange (ETDEWEB)
Singh, Varun; Aute, Vikrant; Radermacher, Reinhard [Department of Mechanical Engineering, University of Maryland, 4164 Glenn L Martin Hall, College Park, MD 20742 (United States)
2009-11-15
A new model for simulating air-to-refrigerant fin-and-tube heat exchangers, with arbitrary fin sheet which encompasses variable tube diameters, variable tube locations, variable tube pitches, internal as well as external jagged edges, variable number of tubes per bank and variable location of fin cuts, is introduced. This model is based on a segment-by-segment approach and is developed to be a general purpose and flexible simulation tool. To account for fin conduction and air propagation through the heat exchanger, it is spatially modeled on a Cartesian grid. A new methodology for air side propagation, required for arbitrary fin sheets, is introduced. The model prediction is validated against experimental data for a condenser using R410A as the working fluid. The predicted results agree within {+-}5% of overall heat load, and {+-}25% for total refrigerant pressure drop. (author)
Advancing Affect Modeling via Preference Learning and Unsupervised Feature Extraction
DEFF Research Database (Denmark)
Martínez, Héctor Pérez
over the other examined methods. The second challenge addressed in this thesis refers to the extraction of relevant information from physiological modalities. Deep learning is proposed as an automatic approach to extract input features for models of affect from physiological signals. Experiments...... difficulties, ordinal reports such as rankings and ratings can yield more reliable affect annotations than alternative tools. This thesis explores preference learning methods to automatically learn computational models from ordinal annotations of affect. In particular, an extensive collection of training...... the complexity of hand-crafting feature extractors that combine information across dissimilar modalities of input. Frequent sequence mining is presented as a method to learn feature extractors that fuse physiological and contextual information. This method is evaluated in a game-based dataset and compared...
Extraction and use of linguistic patterns for modelling medical guidelines.
Serban, Radu; ten Teije, Annette; van Harmelen, Frank; Marcos, Mar; Polo-Conde, Cristina
2007-02-01
The quality of knowledge updates in evidence-based medical guidelines can be improved and the effort spent for updating can be reduced if the knowledge underlying the guideline text is explicitly modelled using the so-called linguistic guideline patterns, mappings between a text fragment and a formal representation of its corresponding medical knowledge. Ontology-driven extraction of linguistic patterns is a method to automatically reconstruct the control knowledge captured in guidelines, which facilitates a more effective modelling and authoring of medical guidelines. We illustrate by examples the use of this method for generating and instantiating linguistic patterns in the text of a guideline for treatment of breast cancer, and evaluate the usefulness of these patterns in the modelling of this guideline. We developed a methodology for extracting and using linguistic patterns in guideline formalization, to aid the human modellers in guideline formalization and reduce the human modelling effort. Using automatic transformation rules for simple linguistic patterns, a good recall (between 72% and 80%) is obtained in selecting the procedural knowledge relevant for the guideline model, even though the precision of the guideline model generated automatically covers only between 20% and 35% of the human-generated guideline model. These results indicate the suitability of our method as a pre-processing step in medical guideline formalization. Modelling and authoring of medical texts can benefit from our proposed method. As pre-requisites for generating automatically a skeleton of the guideline model from the procedural part of the guideline text, to aid the human modeller, the medical terminology used by the guideline must have a good overlap with existing medical thesauri and its procedural knowledge must obey linguistic regularities that can be mapped into the control constructs of the target guideline modelling language.
The Heat Is On! Using Particle Models to Change Students' Conceptions of Heat and Temperature
Hitt, Austin Manning; Townsend, J. Scott
2015-01-01
Elementary, middle-level, and high school science teachers commonly find their students have misconceptions about heat and temperature. Unfortunately, student misconceptions are difficult to modify or change and can prevent students from learning the accurate scientific explanation. In order to improve our students' understanding of heat and…
DEFF Research Database (Denmark)
Wu, Xiaozhou; Zhao, Jianing; Olesen, Bjarne W.
2015-01-01
In this paper, a new simplified model to calculate surface temperature and heat transfer of radiant floor heating and cooling system was proposed and established using the conduction shape factor. Measured data from references were used to validate the proposed model. The results showed...... that the maximum differences between the calculated surface temperature and heat transfer using the proposed model and the measured data were 0.8 ºC and 8.1 W/m2 for radiant floor heating system when average water temperature between 40 ºC and 60 ºC. For the corresponding values were 0.3 ºC and 2.0 W/m2...... for radiant floor cooling systems when average water temperature between 10 ºC and 20 ºC. Numerically simulated data in this study were also used to validate the proposed model. The results showed that the surface temperature and heat transfer of radiant floor calculated by the proposed model agreed very well...
A static model of chromospheric heating in solar flares
Ricchiazzi, P. J.; Canfield, R. C.
1983-01-01
The response of the solar chromosphere to flare processes, namely nonthermal electrons, thermal conduction, and coronal pressure, is modeled. Finite difference methods employing linearization and iteration are used in obtaining simultaneous solutions to the equations of steady-state energy balance, hydrostatic equilibrium, radiative transfer, and atomic statistical equilibrium. The atmospheric response is assumed to be confined to one dimension by a strong vertical magnetic field. A solution is obtained to the radiative transfer equation for the most important optically thick transitions of hydrogen, magnesium, and calcium. The theoretical atmospheres discussed here are seen as elucidating the role of various physical processes in establishing the structure of flare chromospheres. At low coronal pressures, conduction is found to be more important than nonthermal electrons in establishing the position of the transition region. Only thermal conduction can adequately account for the chromospheric evaporation in compact flares. Of the mechanisms considered, only nonthermal electrons bring about significant heating below the flare transition region.
VALIDATION OF SIMULATION MODELS FOR DIFFERENTLY DESIGNED HEAT-PIPE EVACUATED TUBULAR COLLECTORS
DEFF Research Database (Denmark)
Fan, Jianhua; Dragsted, Janne; Furbo, Simon
2007-01-01
Differently designed heat-pipe evacuated tubular collectors have been investigated theoretically and experimentally. The theoretical work has included development of two TRNSYS [1] simulation models for heat-pipe evacuated tubular collectors utilizing solar radiation from all directions. One model...... is developed for heat-pipe evacuated tubular collectors with flat fins and one model is developed for heat-pipe evacuated tubular collectors with curved fins. The models are characterized by detailed calculations of the heat transfer processes in the fins, by detailed shadow modeling and by fins with selective...... coating on both sides. The input to the models is thus not a simple collector efficiency expression but the actual collector geometry. In this study, the TRNSYS models are validated with measurements for four differently designed heat-pipe evacuated tubular collectors. The collectors are produced...
X-ray Studies of Interfacial Strontium–Extractant Complexes in a Model Solvent Extraction System
Energy Technology Data Exchange (ETDEWEB)
Bu, Wei; Mihaylov, Miroslav; Amoanu, Daniel; Lin, Binhua; Meron, Mati; Kuzmenko, Ivan; Soderholm, L.; Schlossman, Mark L.
2014-10-30
The interfacial behavior of a model solvent extraction liquidliquid system, consisting of solutions of dihexadecyl phosphate (DHDP) in dodecane and SrCl2 in water, was studied to determine the structure of the interfacial ionextractant complex and its variation with pH. Previous experiments on a similar extraction system with ErCl3 demonstrated that the kinetics of the extraction process could be greatly retarded by cooling through an adsorption transition, thus providing a method to immobilize ionextractant complexes at the interface and further characterize them with X-ray interface-sensitive techniques. Here, we use this same method to study the SrCl2 system. X-ray reflectivity and fluorescence near total reflection measured the molecular-scale interfacial structure above and below the adsorption transition for a range of pH. Below the transition, DHDP molecules form a homogeneous monolayer at the interface with Sr2+ coverage increasing from zero to saturation (one Sr2+ per two DHDP) within a narrow range of pH. Experimental values of Sr2+ interfacial density determined from fluorescence measurements are larger than those from reflectivity measurements. Although both techniques probe Sr2+ bound to DHDP, only the fluorescence provides adequate sensitivity to Sr2+ in the diffuse double layer. A Stern equation determines the Sr2+ binding constant from the reflectivity measurements and the additional Sr2+ measured in the diffuse double layer is accounted for by GouyChapman theory. Above the transition temperature, a dilute concentration of DHDPSr complexes resides at the interface, even for temperatures far above the transition. A comparison is made of the structure of the interfacial ionextractant complex for this divalent metal ion to recent results on trivalent Er3+ metal ions, which provides insight into the role of metal ion charge on the structure of interfacial ionextractant complexes, as well as implications for extraction of these two differently charged
Directory of Open Access Journals (Sweden)
Pamplona Reinald
2010-06-01
Full Text Available Abstract Background Experimental evidences demonstrate that vegetable derived extracts inhibit cholesterol absorption in the gastrointestinal tract. To further explore the mechanisms behind, we modeled duodenal contents with several vegetable extracts. Results By employing a widely used cholesterol quantification method based on a cholesterol oxidase-peroxidase coupled reaction we analyzed the effects on cholesterol partition. Evidenced interferences were analyzed by studying specific and unspecific inhibitors of cholesterol oxidase-peroxidase coupled reaction. Cholesterol was also quantified by LC/MS. We found a significant interference of diverse (cocoa and tea-derived extracts over this method. The interference was strongly dependent on model matrix: while as in phosphate buffered saline, the development of unspecific fluorescence was inhibitable by catalase (but not by heat denaturation, suggesting vegetable extract derived H2O2 production, in bile-containing model systems, this interference also comprised cholesterol-oxidase inhibition. Several strategies, such as cholesterol standard addition and use of suitable blanks containing vegetable extracts were tested. When those failed, the use of a mass-spectrometry based chromatographic assay allowed quantification of cholesterol in models of duodenal contents in the presence of vegetable extracts. Conclusions We propose that the use of cholesterol-oxidase and/or peroxidase based systems for cholesterol analyses in foodstuffs should be accurately monitored, as important interferences in all the components of the enzymatic chain were evident. The use of adequate controls, standard addition and finally, chromatographic analyses solve these issues.
An Empirical Temperature Variance Source Model in Heated Jets
Khavaran, Abbas; Bridges, James
2012-01-01
An acoustic analogy approach is implemented that models the sources of jet noise in heated jets. The equivalent sources of turbulent mixing noise are recognized as the differences between the fluctuating and Favre-averaged Reynolds stresses and enthalpy fluxes. While in a conventional acoustic analogy only Reynolds stress components are scrutinized for their noise generation properties, it is now accepted that a comprehensive source model should include the additional entropy source term. Following Goldstein s generalized acoustic analogy, the set of Euler equations are divided into two sets of equations that govern a non-radiating base flow plus its residual components. When the base flow is considered as a locally parallel mean flow, the residual equations may be rearranged to form an inhomogeneous third-order wave equation. A general solution is written subsequently using a Green s function method while all non-linear terms are treated as the equivalent sources of aerodynamic sound and are modeled accordingly. In a previous study, a specialized Reynolds-averaged Navier-Stokes (RANS) solver was implemented to compute the variance of thermal fluctuations that determine the enthalpy flux source strength. The main objective here is to present an empirical model capable of providing a reasonable estimate of the stagnation temperature variance in a jet. Such a model is parameterized as a function of the mean stagnation temperature gradient in the jet, and is evaluated using commonly available RANS solvers. The ensuing thermal source distribution is compared with measurements as well as computational result from a dedicated RANS solver that employs an enthalpy variance and dissipation rate model. Turbulent mixing noise predictions are presented for a wide range of jet temperature ratios from 1.0 to 3.20.
Development of a UF{sub 6} cylinder transient heat transfer/stress analysis model
Energy Technology Data Exchange (ETDEWEB)
Williams, W.R. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)
1991-12-31
A heat transfer/stress analysis model is being developed to simulate the heating to a point of rupture of a cylinder containing UF{sub 6} when it is exposed to a fire. The assumptions underlying the heat transfer portion of the model, which has been the focus of work to date, will be discussed. A key aspect of this model is a lumped parameter approach to modeling heat transfer. Preliminary results and future efforts to develop an integrated thermal/stress model will be outlined.
Vintzileos, A.; Halpert, M.; Gottschalk, J.; Allgood, A.
2016-12-01
Heatwaves are among the most dangerous, yet invisible, of natural hazards. According to NOAA, the distribution of 30-year based annual mean fatalities from natural hazards in the U.S. ranks as follows; those from heat (130), floods (81), tornadoes (70), lightning (48) and hurricanes (46). Early warning to excessive heat events can be improved by using multi-scale prognostic systems. We designed and developed such a system for forecasting excessive heat events at lead times beyond Week-1. This Subseasonal Excessive Heat Outlook System (SEHOS) consists of (a) a monitoring/verification component and (b) a forecasting component which in its baseline version uses NOAA's Global Ensemble Forecast System (GEFS) predictions of temperature and humidity from Day-8 to Day-14. In this presentation, we discuss the definition of heat events, sources of predictability and present the forecast skill of SEHOS for the GEFS reforecast period (1985-2014). We then use subseasonal reforecasts from several models from the S2S database and discuss the forecast value added by multi-model approaches in predicting excessive heat events.
Numerical modeling of the conduction and radiation heating in precision glass moulding
DEFF Research Database (Denmark)
Sarhadi, Ali; Hattel, Jesper Henri; Hansen, Hans Nørgaard
2012-01-01
wafer, heating can be performed by either conduction or radiation. The numerical simulation of these two heating mechanisms in the wafer based glass moulding process is the topic of the present paper. First, the transient heating of the glass wafer is simulated by the FEM software ABAQUS. Temperature...... dependent material data of the glass wafer are taken into account in the simulation to have a more realistic model of the material. Heating curves depicting temperature as a function of time inside the glass wafer are predicted for both radiation and conduction heating and based on that the heating time...
Energy Technology Data Exchange (ETDEWEB)
Zinki, Heimo [ZW Energiteknik, Nykoeping (Sweden)
1996-11-01
The aim of this study was to investigate the possibility of analysing the temperature profile at the ground surface above buried district heating pipes in such a way that would enable the quantitative determination of heat loss from the pair of pipes. In practical applications, it is supposed that this temperature profile is generated by means of advanced IR-thermography. For this purpose, the principle of the TX - model has been developed, based on the fact that the heat losses from pipes buried in the ground have a temperature signature on the ground surface. Qualitative analysis of this temperature signature is very well known and in practical use for detecting leaks from pipes. These techniques primarily make use of relative changes of the temperature pattern along the pipe. In the quantitative heat loss analysis, however, it is presumed that the temperature profile across the pipes is related to the pipe heat loss per unit length. The basic idea is that the integral of the temperature profile perpendicular to the pipe, called TX, is a function of the heat loss, but is also affected by other parameters such as burial depth, heat diffusivity, wind, precipitation and so on. In order to analyse the parameters influencing the TX- factor, a simulation model for the energy balance at the ground surface has been developed. This model includes the heat flow from the pipe to the surface and the heat exchange at the surface with the environment due to convection, latent heat change, solar and long wave radiation. The simulation gives the surprising result that the TX factor is by and large unaffected during the course of a day even when the sun is shining, as long as other climate conditions are relatively stable (low wind, no rain, no shadows). The results from the simulations were verified at different sites in Denmark, Finland, Sweden and USA through a co-operative research program organised and partially financed by the IEA District Heating Programme, Task III, and
Numerical Modelling of Induction Heating for a Molten Salts Pyrochemical Process
Energy Technology Data Exchange (ETDEWEB)
Vu, Xuan-Tuyen; Feraud, Jean-Pierre; Ode, Denis [CEA Marcoule: DTEC/SGCS/LGCI Bat. 57 B17171, 30207 Bagnols/Ceze (France); Du Terrail Couvat, Yves [SIMaP, Grenoble INP, CNRS: ENSEEG, BP 75, 38402 Saint Martin d' Heres Cedex (France)
2008-07-01
Technological developments in the pyro-chemistry program are required to allow choices for a reprocessing experiment on 100 g of spent nuclear fuel. In this context, a special device must be designed for the solid/gas reaction phases followed by actinide extraction and stripping in molten salt. This paper discusses a modelling approach for designing an induction furnace. Using this numerical approach is a good way to improve thermal performance of the device in terms of magnetic/thermal coupling phenomena. The influence of current frequency is also studied to give another view of the possibilities of an induction furnace. Electromagnetic forces are taken into account in a computational fluid dynamics code derived from a specifically developed exchange library. Induction heating systems are an example of a typical multi-physics problem involving numerically coupled equations. (authors)
Observational & modeling analysis of surface heat and moisture fluxes
Energy Technology Data Exchange (ETDEWEB)
Smith, E. [Florida State Univ., Tallahassee, FL (United States)
1995-09-01
An observational and modeling study was conducted to help assess how well current GCMs are predicting surface fluxes under the highly variable cloudiness and flow conditions characteristic of the real atmosphere. The observational data base for the study was obtained from a network of surface flux stations operated during the First ISLSCP Field Experiment (FIFE). The study included examination of a surface-driven secondary circulation in the boundary layer resulting from a persistent cross-site gradient in soil moisture, to demonstrate the sensitivity of boundary layer dynamics to heterogeneous surface fluxes, The performance of a biosphere model in reproducing the measured surface fluxes was evaluated with and without the use of satellite retrieval of three key canopy variables with RMS uncertainties commensurate with those of the measurements themselves. Four sensible heat flux closure schemes currently being used in GCMs were then evaluated against the FIFE observations. Results indicate that the methods by which closure models are calibrated lead to exceedingly large errors when the schemes are applied to variable boundary layer conditions. 4 refs., 2 figs.
Modeling the Supercritical Fluid Extraction of Essential Oils from Plant Materials
Sovová, H. (Helena)
2012-01-01
Different types of mathematical models were applied in the last decade to simulate kinetics of supercritical fluid extraction (SFE) of essential oils from aromatic plants. Compared to the extraction of fatty oils, modeling of extraction of essential oils is more complicated due to their potential fractionation, co-extraction of less soluble compounds, and stronger effect of flow pattern on extraction yield, which is connected with solute adsorption on plant matrix. Fitting the SFE models to e...
Economic Model Predictive Control for Hot Water Based Heating Systems in Smart Buildings
DEFF Research Database (Denmark)
Awadelrahman, M. A. Ahmed; Zong, Yi; Li, Hongwei
2017-01-01
This paper presents a study to optimize the heating energy costs in a residential building with varying electricity price signals based on an Economic Model Predictive Controller (EMPC). The investigated heating system consists of an air source heat pump (ASHP) incorporated with a hot water tank...
Clothing evaporative heat resistance - Proposal for improved representation in standards and models
Havenith, G.; Holmér, I.; Hartog, E.A. den; Parsons, K.C.
1999-01-01
Clothing heat and vapour resistances are important inputs for standards and models dealing with thermal comfort, heat- and cold-stress. A vast database of static clothing heat resistance values is available, and this was recently expanded with correction equations to account for effects of movement
Three-Step Model of Dispersed Flow Heat Transfer (Post CHF ...
African Journals Online (AJOL)
The paper presents a three step model of the dispersed flow heat transfer process, using an analysis of a single drop motion and heat transfer, and a statistical representation of the overall behaviour of the drops. The resulting equation gives the total heat transferred to the flow in terms of the mass flux, flow quality, fluid ...
DEFF Research Database (Denmark)
Martre, Pierre; Reynolds, Matthew; Asseng, Senthold
2017-01-01
The data set contains a portion of the International Heat Stress Genotype Experiment (IHSGE) data used in the AgMIP-Wheat project to analyze the uncertainty of 30 wheat crop models and quantify the impact of heat on global wheat yield productivity. It includes two spring wheat cultivars grown dur...
Analytical solution of nucleate pool boiling heat transfer model based on macrolayer
Danish, Mohd; Al Mesfer, Mohammed K.
2018-02-01
In the present work, a transient heat conduction model has been developed for heat transfer through macrolayer in nucleate regime of pool boiling. The developed heat transfer model was solved analytically (Laplace Transform) using appropriate initial and boundary conditions. The influence of macrolayer thickness, wall superheat, and time on conduction heat flux has been predicted. The average conduction heat flux as a function of wall superheat and macrolayer thickness has also been predicted. The findings of the study have been compared with experimental results, and they are in reasonable agreement. For higher values of wall superheat, which correspond to nucleate pool boiling, predicted results agree with experimental data. Findings also substantiate the assertion that heat conduction across the macrolayer constitutes the major mode of heat transfer from the heated wall to the boiling liquid in the macrolayer regime of pool boiling.
Analytical solution of nucleate pool boiling heat transfer model based on macrolayer
Danish, Mohd; Al Mesfer, Mohammed K.
2017-08-01
In the present work, a transient heat conduction model has been developed for heat transfer through macrolayer in nucleate regime of pool boiling. The developed heat transfer model was solved analytically (Laplace Transform) using appropriate initial and boundary conditions. The influence of macrolayer thickness, wall superheat, and time on conduction heat flux has been predicted. The average conduction heat flux as a function of wall superheat and macrolayer thickness has also been predicted. The findings of the study have been compared with experimental results, and they are in reasonable agreement. For higher values of wall superheat, which correspond to nucleate pool boiling, predicted results agree with experimental data. Findings also substantiate the assertion that heat conduction across the macrolayer constitutes the major mode of heat transfer from the heated wall to the boiling liquid in the macrolayer regime of pool boiling.
Directory of Open Access Journals (Sweden)
Helena Sovová
2016-05-01
Full Text Available Microalgae contain valuable biologically active lipophilic substances such as omega-3 fatty acids and carotenoids. In contrast to the recovery of vegetable oils from seeds, where the extraction with supercritical CO2 is used as a mild and selective method, economically viable application of this method on similarly soluble oils from microalgae requires, in most cases, much higher pressure. This paper presents and verifies hypothesis that this difference is caused by high adsorption capacity of microalgae. Under the pressures usually applied in supercritical fluid extraction from plants, microalgae bind a large fraction of the extracted oil, while under extremely high CO2 pressures their adsorption capacity diminishes and the extraction rate depends on oil solubility in supercritical CO2. A mathematical model for the extraction from microalgae was derived and applied to literature data on the extraction kinetics in order to determine model parameters.
Automated extraction of knowledge for model-based diagnostics
Gonzalez, Avelino J.; Myler, Harley R.; Towhidnejad, Massood; Mckenzie, Frederic D.; Kladke, Robin R.
1990-01-01
The concept of accessing computer aided design (CAD) design databases and extracting a process model automatically is investigated as a possible source for the generation of knowledge bases for model-based reasoning systems. The resulting system, referred to as automated knowledge generation (AKG), uses an object-oriented programming structure and constraint techniques as well as internal database of component descriptions to generate a frame-based structure that describes the model. The procedure has been designed to be general enough to be easily coupled to CAD systems that feature a database capable of providing label and connectivity data from the drawn system. The AKG system is capable of defining knowledge bases in formats required by various model-based reasoning tools.
Heat exchange modeling in a multilayered karst aquifer affected by seawater intrusion
Luca Vettorello; Roberto Pedron; Andrea Sottani; Michele Chieco
2015-01-01
A Feflow thermohaline model has been implemented in order to study borehole heat exchangers (BHEs) activity in a coastal aquifer in the South of Italy (Province of Lecce, Puglia Region). The modeled closed-loop system consists of two double u-pipe heat exchangers, installed in 200 meters deep boreholes. The main purpose of numerical modeling was to forecast thermal plume extension in groundwater after a long period of heat exchange, calculating temperature trends in observation points during ...
Probabilistic tectonic heat flow modeling for basin maturation: Assessment method and applications
Wees, J.D. van; Bergen, F. van; David, P.; Nepveu, M.; Beekman, F.; Cloetingh, S.; Bonté, D.
2009-01-01
Tectonic modeling is often neglected in the basin modeling workflow and heat flow is most times considered a user input. Such heat flows can, therefore, result in erroneous basin modeling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify
Probabilistic tectonic heat flow modelling for basin maturation: method and applications
van Wees, J.D.A.M.; van Bergen, F.; David, P.; Nepveu, M.; Beekman, W.W.W.; Cloetingh, S.A.P.L.; Bonte, D.D.P.
2009-01-01
Tectonic modeling is often neglected in the basin modeling workflow and heat flow is most times considered a user input. Such heat flows can, therefore, result in erroneous basin modeling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify
Modelling the heat dynamics of a building using stochastic differential equations
DEFF Research Database (Denmark)
Andersen, Klaus Kaae; Madsen, Henrik; Hansen, Lars Henrik
2000-01-01
variations. Besides modelling the heat transfer between thermal zones, attention is put on modelling the heat input from radiators and solar radiation. The applied modelling procedure is based on collected building performance data and statistical methods. The statistical methods are used in parameter...
Modeling Pumped Thermal Energy Storage with Waste Heat Harvesting
Abarr, Miles L. Lindsey
This work introduces a new concept for a utility scale combined energy storage and generation system. The proposed design utilizes a pumped thermal energy storage (PTES) system, which also utilizes waste heat leaving a natural gas peaker plant. This system creates a low cost utility-scale energy storage system by leveraging this dual-functionality. This dissertation first presents a review of previous work in PTES as well as the details of the proposed integrated bottoming and energy storage system. A time-domain system model was developed in Mathworks R2016a Simscape and Simulink software to analyze this system. Validation of both the fluid state model and the thermal energy storage model are provided. The experimental results showed the average error in cumulative fluid energy between simulation and measurement was +/- 0.3% per hour. Comparison to a Finite Element Analysis (FEA) model showed PTES) that uses ammonia as the working fluid. This analysis focused on the effects of hot thermal storage utilization, system pressure, and evaporator/condenser size on the system performance. This work presents the estimated performance for a proposed baseline Bot-PTES. Results of this analysis showed that all selected parameters had significant effects on efficiency, with the evaporator/condenser size having the largest effect over the selected ranges. Results for the baseline case showed stand-alone energy storage efficiencies between 51 and 66% for varying power levels and charge states, and a stand-alone bottoming efficiency of 24%. The resulting efficiencies for this case were low compared to competing technologies; however, the dual-functionality of the Bot-PTES enables it to have higher capacity factor, leading to 91-197/MWh levelized cost of energy compared to 262-284/MWh for batteries and $172-254/MWh for Compressed Air Energy Storage.
Implementation and model to model intercomparison of 12 heat stress metrics
Buzan, Jonathan R.
Earth system models simulate the dynamics of the most complex systems on our planet with some success. Despite the overwhelming sophistication of these models, which include dynamical interactions of ocean, atmosphere, vegetation, ice, and land-surface properties, they fail to include the most important element. People. Humans are also a complex physical-biological system and coupling of human physiology within an Earth Systems Modeling framework is challenging. This thesis presents results that tackle one particular component of human physiological climate interaction--a representation of heat stress on human physiology. Twelve different metrics were implemented and analyzed. These metrics represent a variety of philosophical approaches to characterizing heat stress: thermal comfort, physiological responses, and first principle physics. We implemented these 12 metrics into the Community Land Model (CLM4.5). All of the metrics implemented measure the covariance of near surface atmospheric variables: temperature, pressure, and humidity. Results show that heat stress may be broken into two regimes; arid and non-arid regions (i.e. the rest of the land surface). Additionally, results show that the highest heat stress zones are a robust feature with low variability. Temperatures vary by +/-3°C as compared to +/-1°C wet bulb temperatures, and is consistent over a vast area of Earth.
Modelling of Split Condenser Heat Pump: Optimization and Exergy Analysis
DEFF Research Database (Denmark)
Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix
2017-01-01
This paper presents a numerical study of a split condenser heat pump (SCHP). The SCHP setup differs from a traditional heat pump (THP) setup in the way that two separate water streams on the secondary side of the condenser are heated in parallel to different temperature levels, whereas only one s...... unit. For a water temperature of 40°C/85°C and an evaporating temperature of 5°C, the total area of the two plate heat exchangers was reduced by 3%. When using the SCHP setup the exergy destruction was slightly smaller compared to the THP....
Directory of Open Access Journals (Sweden)
Moo-Yeon Lee
2012-01-01
Full Text Available The objective of this study is to provide the numerical model for prediction of the frost growth of the round plate fin for the purpose of using it as a round plate fin-tube heat exchanger (evaporator under frosting conditions. In this study, numerical model was considering the frost density change with time, and it showed better agreement with experimental data of Sahin (1994 than that of the Kim model (2004 and the Jonse and Parker model (1975. This is because the prediction on the frost height with time was improved by using the frost thermal conductivity reflecting the void fraction and density of ice crystal with frost growth. Therefore, the developed numerical model could be used for frosting performance prediction of the round plate fin-tube heat exchanger.
Tao, Yang; Wu, Di; Zhang, Qing-An; Sun, Da-Wen
2014-03-01
The ultrasound-assisted extraction process of phenolics including anthocyanins from wine lees was modeled and optimized in this research. An ultrasound bath system with the frequency of 40 kHz was used and the acoustic energy density during extraction was identified to 48 W/L. The effects of extraction time, extraction temperature, solvent-to-solid ratio and the solvent composition on the extraction yields of total phenolics and total anthocyanins were taken into account. The extraction process was simulated and optimized by means of artificial neural network (ANN) and genetic algorithm (GA). The constructed ANN models were accurate to predict the extraction yields of both total phenolics and total anthocyanins according to the statistical analysis. Meanwhile, the input space of the ANN models was optimized by GA, so as to maximize the extraction yields. Under the optimal conditions, the experimental yields of total phenolics and total anthocyanins were 58.76 and 6.69 mg/g, respectively, which agreed with the predicted values. Furthermore, more amounts of total phenolics and total anthocyanins were extracted by ultrasound at the optimal conditions than by conventional maceration. On the other hand, the stability of phenolics in the liquid extracts obtained from ultrasound-assisted extraction during storage was evaluated. After 30-day storage, the total phenolic contents in extracts stored at 4 °C and 20 °C decreased by 12.5% and 12.1%, respectively. Moreover, anthocyanins were more stable at 4 °C while tartaric esters and flavonols exhibited a better stability at 20 °C. Overall, the loss of phenolics during storage found in this study could be acceptable. Copyright © 2013 Elsevier B.V. All rights reserved.
Model selection for the extraction of movement primitives
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Dominik M Endres
2013-12-01
Full Text Available A wide range of blind source separation methods have been used in motor control research for the extraction of movement primitives from EMG and kinematic data. Popular examples are principal component analysis (PCA,independent component analysis (ICA, anechoic demixing, and the time-varying synergy model. However, choosing the parameters of these models, or indeed choosing the type of model, is often done in a heuristic fashion, driven by result expectations as much as by the data. We propose an objective criterion which allows to select the model type, number of primitives and the temporal smoothness prior. Our approach is based on a Laplace approximation to the posterior distribution of the parameters of a given blind source separation model, re-formulated as a Bayesian generative model.We first validate our criterion on ground truth data, showing that it performs at least as good as traditional model selection criteria (Bayesian information criterion, BIC and the Akaike Information Criterion (AIC. Then, we analyze human gait data, finding that an anechoic mixture model with a temporal smoothness constraint on the sources can best account for the data.
Optimum load distribution between heat sources based on the Cournot model
Penkovskii, A. V.; Stennikov, V. A.; Khamisov, O. V.
2015-08-01
One of the widespread models of the heat supply of consumers, which is represented in the "Single buyer" format, is considered. The methodological base proposed for its description and investigation presents the use of principles of the theory of games, basic propositions of microeconomics, and models and methods of the theory of hydraulic circuits. The original mathematical model of the heat supply system operating under conditions of the "Single buyer" organizational structure provides the derivation of a solution satisfying the market Nash equilibrium. The distinctive feature of the developed mathematical model is that, along with problems solved traditionally within the bounds of bilateral relations of heat energy sources-heat consumer, it considers a network component with its inherent physicotechnical properties of the heat network and business factors connected with costs of the production and transportation of heat energy. This approach gives the possibility to determine optimum levels of load of heat energy sources. These levels provide the given heat energy demand of consumers subject to the maximum profit earning of heat energy sources and the fulfillment of conditions for formation of minimum heat network costs for a specified time. The practical realization of the search of market equilibrium is considered by the example of a heat supply system with two heat energy sources operating on integrated heat networks. The mathematical approach to the solution search is represented in the graphical form and illustrates computations based on the stepwise iteration procedure for optimization of levels of loading of heat energy sources (groping procedure by Cournot) with the corresponding computation of the heat energy price for consumers.
A Financial Data Mining Model for Extracting Customer Behavior
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Mark K.Y. Mak
2011-08-01
Full Text Available Facing the problem of variation and chaotic behavior of customers, the lack of sufficient information is a challenge to many business organizations. Human analysts lacking an understanding of the hidden patterns in business data, thus, can miss corporate business opportunities. In order to embrace all business opportunities, enhance the competitiveness, discovery of hidden knowledge, unexpected patterns and useful rules from large databases have provided a feasible solution for several decades. While there is a wide range of financial analysis products existing in the financial market, how to customize the investment portfolio for the customer is still a challenge to many financial institutions. This paper aims at developing an intelligent Financial Data Mining Model (FDMM for extracting customer behavior in the financial industry, so as to increase the availability of decision support data and hence increase customer satisfaction. The proposed financial model first clusters the customers into several sectors, and then finds the correlation among these sectors. It is noted that better customer segmentation can increase the ability to identify targeted customers, therefore extracting useful rules for specific clusters can provide an insight into customers' buying behavior and marketing implications. To validate the feasibility of the proposed model, a simple dataset is collected from a financial company in Hong Kong. The simulation experiments show that the proposed method not only can improve the workflow of a financial company, but also deepen understanding of investment behavior. Thus, a corporation is able to customize the most suitable products and services for customers on the basis of the rules extracted.
Directory of Open Access Journals (Sweden)
Fisnik Dalipi
2016-01-01
Full Text Available We present our data-driven supervised machine-learning (ML model to predict heat load for buildings in a district heating system (DHS. Even though ML has been used as an approach to heat load prediction in literature, it is hard to select an approach that will qualify as a solution for our case as existing solutions are quite problem specific. For that reason, we compared and evaluated three ML algorithms within a framework on operational data from a DH system in order to generate the required prediction model. The algorithms examined are Support Vector Regression (SVR, Partial Least Square (PLS, and random forest (RF. We use the data collected from buildings at several locations for a period of 29 weeks. Concerning the accuracy of predicting the heat load, we evaluate the performance of the proposed algorithms using mean absolute error (MAE, mean absolute percentage error (MAPE, and correlation coefficient. In order to determine which algorithm had the best accuracy, we conducted performance comparison among these ML algorithms. The comparison of the algorithms indicates that, for DH heat load prediction, SVR method presented in this paper is the most efficient one out of the three also compared to other methods found in the literature.
Directory of Open Access Journals (Sweden)
Harry O'Hanley
2012-01-01
Full Text Available Nanofluids are being considered for heat transfer applications; therefore it is important to know their thermophysical properties accurately. In this paper we focused on nanofluid specific heat capacity. Currently, there exist two models to predict a nanofluid specific heat capacity as a function of nanoparticle concentration and material. Model I is a straight volume-weighted average; Model II is based on the assumption of thermal equilibrium between the particles and the surrounding fluid. These two models give significantly different predictions for a given system. Using differential scanning calorimetry (DSC, a robust experimental methodology for measuring the heat capacity of fluids, the specific heat capacities of water-based silica, alumina, and copper oxide nanofluids were measured. Nanoparticle concentrations were varied between 5 wt% and 50 wt%. Test results were found to be in excellent agreement with Model II, while the predictions of Model I deviated very significantly from the data. Therefore, Model II is recommended for nanofluids.
Applications of hydrologic information automatically extracted from digital elevation models
Jenson, Susan K.
1991-01-01
Digital elevation models (DEMs) can be used to derive a wealth of information about the morphology of a land surface. Traditional raster analysis methods can be used to derive slope, aspect, and shaded relief information; recently-developed computer programs can be used to delineate depressions, overland flow paths, and watershed boundaries. These methods were used to delineate watershed boundaries for a geochemical stream sediment survey, to compare the results of extracting slope and flow paths from DEMs of varying resolutions, and to examine the geomorphology of a Martian DEM. -Author
DEFF Research Database (Denmark)
Pafilis, Evangelos; Buttigieg, Pier Luigi; Ferrell, Barbra
2016-01-01
The microbial and molecular ecology research communities have made substantial progress on developing standards for annotating samples with environment metadata. However, sample manual annotation is a highly labor intensive process and requires familiarity with the terminologies used. We have the...... and text-mining-assisted curation revealed that EXTRACT speeds up annotation by 15-25% and helps curators to detect terms that would otherwise have been missed.Database URL: https://extract.hcmr.gr/......., organism, tissue and disease terms. The evaluators in the BioCreative V Interactive Annotation Task found the system to be intuitive, useful, well documented and sufficiently accurate to be helpful in spotting relevant text passages and extracting organism and environment terms. Comparison of fully manual...
Procedure for identifying models for the heat dynamics of buildings
DEFF Research Database (Denmark)
Bacher, Peder; Madsen, Henrik
This report describes a new method for obtaining detailed information about the heat dynamics of a building using frequent reading of the heat consumption. Such a procedure is considered to be of uttermost importance as a key procedure for using readings from smart meters, which is expected...
Fang, En; Wu, Xiaojie; Yu, Yuesen; Xiu, Junrui
2017-03-01
In this paper, a numerical model is developed by combining thermodynamics with heat transfer theory. Taking inner and external multi-irreversibility into account, it is with a complementary equation for heat circulation in air gaps of a steady cooling system with commercial thermoelectric modules operating in refrigeration mode. With two modes concerned, the equation presents the heat flowing through air gaps which forms heat circulations between both sides of thermoelectric coolers (TECs). In numerical modelling, a TEC is separated as two temperature controlled constant heat flux reservoirs in a thermal resistance network. In order to obtain the parameter values, an experimental apparatus with a commercial thermoelectric cooler was built to characterize the performance of a TEC with heat source and sink assembly. At constant power dissipation, steady temperatures of heat source and both sides of the thermoelectric cooler were compared with those in a standard numerical model. The method displayed that the relationship between Φf and the ratio Φ_{c}'/Φ_{c} was linear as expected. Then, for verifying the accuracy of proposed numerical model, the data in another system were recorded. It is evident that the experimental results are in good agreement with simulation(proposed model) data at different heat transfer rates. The error is small and mainly results from the instabilities of thermal resistances with temperature change and heat flux, heat loss of the device vertical surfaces and measurements.
Considering extraction constraints in long-term oil price modelling
Energy Technology Data Exchange (ETDEWEB)
Rehrl, Tobias; Friedrich, Rainer; Voss, Alfred
2005-12-15
Apart from divergence about the remaining global oil resources, the peak oil discussion can be reduced to a dispute about the time rate at which these resources can be supplied. On the one hand it is problematic to project oil supply trends without taking both - prices as well as supply costs - explicitly into account. On the other hand are supply cost estimates however itself heavily dependent on the underlying extraction rates and are actually only valid within a certain business-as-usual extraction rate scenario (which itself is the task to determine). In fact, even after having applied enhanced recovery technologies, the rate at which an oil field can be exploited is quite restricted. Above a certain level an additional extraction rate increase can only be costly achieved at risks of losses in the overall recoverable amounts of the oil reservoir and causes much higher marginal cost. This inflexibility in extraction can be overcome in principle by the access to new oil fields. This indicates why the discovery trend may roughly form the long-term oil production curve, at least for price-taking suppliers. The long term oil discovery trend itself can be described as a logistic process with the two opposed effects of learning and depletion. This leads to the well-known Hubbert curve. Several attempts have been made to incorporate economic variables econometrically into the Hubbert model. With this work we follow a somewhat inverse approach and integrate Hubbert curves in our Long-term Oil Price and EXtraction model LOPEX. In LOPEX we assume that non-OPEC oil production - as long as the oil can be profitably discovered and extracted - is restricted to follow self-regulative discovery trends described by Hubbert curves. Non-OPEC production in LOPEX therefore consists of those Hubbert cycles that are profitable, depending on supply cost and price. Endogenous and exogenous technical progress is extra integrated in different ways. LOPEX determines extraction and price
Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles
DEFF Research Database (Denmark)
Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.
2011-01-01
Subsurface heat production from oxidation of pyrite is an important process that may increase subsurface temperatures within coal waste rock piles and increase the release of acid mine drainage, AMD. Waste rock piles in the Arctic are especially vulnerable to changes in subsurface temperatures...... as the release of AMD normally is limited by permafrost. Here we show that temperatures within a 20 year old heat-producing waste rock pile in Svalbard (78°N) can be modelled by the one-dimensional heat and water flow model (CoupModel) with a new temperature-dependent heat-production module that includes both...... biological and chemical oxidation processes and heat source depletion over time. Inputs to the model are meteorological measurements, physical properties of the waste rock material and measured subsurface heat-production rates. Measured mean annual subsurface temperatures within the waste rock pile are up...
Modelling the Size of Seasonal Thermal Storage in the Solar District Heating System
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Giedrė Streckienė
2012-12-01
Full Text Available The integration of a thermal storage system into the solar heating system enables to increase the use of solar thermal energy in buildings and allows avoiding the mismatch between consumers’ demand and heat production in time. The paper presents modelling a seasonal thermal storage tank various sizes of which have been analyzed in the district solar heating system that could cover a part of heat demand for the district of individual houses in Vilnius. A biomass boiler house, as an additional heat source, should allow covering the remaining heat demand. energyPRO software is used for system modelling. The paper evaluates heat demand, climate conditions and technical characteristics.Article in Lithuanian
ANALYZING NUMERICAL ERRORS IN DOMAIN HEAT TRANSPORT MODELS USING THE CVBEM.
Hromadka, T.V.
1987-01-01
Besides providing an exact solution for steady-state heat conduction processes (Laplace-Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil-water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximate boundary generation.
Identifying the optimal supply temperature in district heating networks - A modelling approach
DEFF Research Database (Denmark)
Mohammadi, Soma; Bojesen, Carsten
2014-01-01
The number of low-energy and energy renovated buildings with considerably low heating demand has been continuously increasing in recent years. Combined with utilizing low temperature sources, this development raises the necessity of introducing a new generation of District Heating [DH] Systems...... of this study is to develop a model for thermo-hydraulic calculation of low temperature DH system. The modelling is performed with emphasis on transient heat transfer in pipe networks. The pseudo-dynamic approach is adopted to model the District Heating Network [DHN] behaviour which estimates the temperature...
Modeling the Performance of Water-Zeolite 13X Adsorption Heat Pump
Kowalska, Kinga; Ambrożek, Bogdan
2017-12-01
The dynamic performance of cylindrical double-tube adsorption heat pump is numerically analysed using a non-equilibrium model, which takes into account both heat and mass transfer processes. The model includes conservation equations for: heat transfer in heating/cooling fluids, heat transfer in the metal tube, and heat and mass transfer in the adsorbent. The mathematical model is numerically solved using the method of lines. Numerical simulations are performed for the system water-zeolite 13X, chosen as the working pair. The effect of the evaporator and condenser temperatures on the adsorption and desorption kinetics is examined. The results of the numerical investigation show that both of these parameters have a significant effect on the adsorption heat pump performance. Based on computer simulation results, the values of the coefficients of performance for heating and cooling are calculated. The results show that adsorption heat pumps have relatively low efficiency compared to other heat pumps. The value of the coefficient of performance for heating is higher than for cooling
Modeling the Performance of Water-Zeolite 13X Adsorption Heat Pump
Directory of Open Access Journals (Sweden)
Kowalska Kinga
2017-12-01
Full Text Available The dynamic performance of cylindrical double-tube adsorption heat pump is numerically analysed using a non-equilibrium model, which takes into account both heat and mass transfer processes. The model includes conservation equations for: heat transfer in heating/cooling fluids, heat transfer in the metal tube, and heat and mass transfer in the adsorbent. The mathematical model is numerically solved using the method of lines. Numerical simulations are performed for the system water-zeolite 13X, chosen as the working pair. The effect of the evaporator and condenser temperatures on the adsorption and desorption kinetics is examined. The results of the numerical investigation show that both of these parameters have a significant effect on the adsorption heat pump performance. Based on computer simulation results, the values of the coefficients of performance for heating and cooling are calculated. The results show that adsorption heat pumps have relatively low efficiency compared to other heat pumps. The value of the coefficient of performance for heating is higher than for cooling
Shang, De-Yi
2012-01-01
This book presents recent developments in our systematic studies of hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, as well as accelerating film flow of non-Newtonian power-law fluids (FFNF). These new developments provided in this book are (i) novel system of analysis models based on the developed New Similarity Analysis Method; (ii) a system of advanced methods for treatment of gas temperature- dependent physical properties, and liquid temperature- dependent physical properties; (iii) the organically combined models of the governing mathematical models with those on treatment model of variable physical properties; (iv) rigorous approach of overcoming a challenge on accurate solution of three-point boundary value problem related to two-phase film boiling and condensation; and (v) A pseudo-similarity method of dealing with thermal boundary layer of FFNF for greatly simplifies the heat-transfer analysis and numerical calculati...
Statistical analysis as approach to conductive heat transfer modelling
Antonyová, A.; Antony, P.
2013-04-01
The main inspiration for article was the problem of high investment into installation of the building insulation. The question of its effectiveness and reliability also after the period of 10 or 15 years was the topic of the international research project carried out at the University of Prešov in Prešov and Vienna University of Technology entitled "Detection and Management of Risk Processes in Building Insulation" and numbered SRDA SK-AT-0008-10. To detect especially the moisture problem as risk process in the space between the wall and insulation led to construction new measuring equipment to test the moisture and temperature without the insulation destruction and this way to describe real situation in old buildings too. The further investigation allowed us to analyse the range of data in the amount of 1680 measurements and express conductive heat transfer using the methods of statistical analysis. Modelling comprises relationships of the environment properties inside the building, in the space between the wall and insulation and in ambient surrounding of the building. Radial distribution function also characterizes the connection of the temperature differences.
Golmakani, Mohammad-Taghi; Moayyedi, Mahsa
2015-11-01
Dried and fresh peels of Citrus limon were subjected to microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME), respectively. A comparison was made between MAHD and SFME with the conventional hydrodistillation (HD) method in terms of extraction kinetic, chemical composition, and antioxidant activity. Higher yield results from higher extraction rates by microwaves and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way. Gas chromatography/mass spectrometry (GC/MS) analysis did not indicate any noticeable differences between the constituents of essential oils obtained by MAHD and SFME, in comparison with HD. Antioxidant analysis of the extracted essential oils indicated that microwave irradiation did not have adverse effects on the radical scavenging activity of the extracted essential oils. The results of this study suggest that MAHD and SFME can be termed as green technologies because of their less energy requirements per ml of essential oil extraction.
Model-Based Extracted Water Desalination System for Carbon Sequestration
Energy Technology Data Exchange (ETDEWEB)
Dees, Elizabeth M. [General Electric Global Research Center, Niskayuna, NY (United States); Moore, David Roger [General Electric Global Research Center, Niskayuna, NY (United States); Li, Li [Pennsylvania State Univ., University Park, PA (United States); Kumar, Manish [Pennsylvania State Univ., University Park, PA (United States)
2017-05-28
Over the last 1.5 years, GE Global Research and Pennsylvania State University defined a model-based, scalable, and multi-stage extracted water desalination system that yields clean water, concentrated brine, and, optionally, salt. The team explored saline brines that ranged across the expected range for extracted water for carbon sequestration reservoirs (40,000 up to 220,000 ppm total dissolved solids, TDS). In addition, the validated the system performance at pilot scale with field-sourced water using GE’s pre-pilot and lab facilities. This project encompassed four principal tasks, in addition to Project Management and Planning: 1) identify a deep saline formation carbon sequestration site and a partner that are suitable for supplying extracted water; 2) conduct a techno-economic assessment and down-selection of pre-treatment and desalination technologies to identify a cost-effective system for extracted water recovery; 3) validate the downselected processes at the lab/pre-pilot scale; and 4) define the scope of the pilot desalination project. Highlights from each task are described below: Deep saline formation characterization The deep saline formations associated with the five DOE NETL 1260 Phase 1 projects were characterized with respect to their mineralogy and formation water composition. Sources of high TDS feed water other than extracted water were explored for high TDS desalination applications, including unconventional oil and gas and seawater reverse osmosis concentrate. Technoeconomic analysis of desalination technologies Techno-economic evaluations of alternate brine concentration technologies, including humidification-dehumidification (HDH), membrane distillation (MD), forward osmosis (FO), turboexpander-freeze, solvent extraction and high pressure reverse osmosis (HPRO), were conducted. These technologies were evaluated against conventional falling film-mechanical vapor recompression (FF-MVR) as a baseline desalination process. Furthermore, a
Energy Technology Data Exchange (ETDEWEB)
Shah, S., E-mail: sajidshah313@yahoo.com; Hussain, S.; Sagheer, M. [Department of Mathematics, Capital University of Science and Technology, Islamabad (Pakistan)
2016-08-15
Present study examines the numerical analysis of MHD flow of Maxwell fluid with thermal radiation and Joule heating by considering the recently developed Cattaneo-Christov heat flux model which explains the time relaxation characteristics for the heat flux. The objective is to analyze the governing parameters such as viscoelastic fluid parameter, Magnetic parameter, Eckert and Prandtl number’s impact on the velocity and temperature profiles through graphs and tables. Suitable similarity transformations have been used to reduce the formulated PDEs into a system of coupled non-linear ODEs. Shooting technique has been invoked for finding the numerical solutions of the dimensionless velocity and temperature profiles. Additionally, the MATLAB built-in routine bvp4c has also been used to verify and strengthen the results obtained by shooting method. From some special cases of the present work, a comparison with the previously published results has been presented.
The modeling of heat affected zone (HAZ in submerged arc welding (SAW surfacing steel element
Directory of Open Access Journals (Sweden)
J. Winczek
2016-04-01
Full Text Available In the work the bimodal heat source model in the description of the temperature field is presented. The electric arc was treated physically as one heat source, whose heat was divided: part of the heat is transferred by the direct impact of the electric arc, but another part of the heat is transferred to the weld by the melted material of the electrode. Computations of the temperature field during SAW surfacing of S355 steel element are carried out. The macrographic and metallographic analysis of the weld confirmed the depth and shapes of the fusion line and HAZ defined by the numerical simulation.
A simple and accurate numerical network flow model for bionic micro heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Pieper, M.; Klein, P. [Fraunhofer Institute (ITWM), Kaiserslautern (Germany)
2011-05-15
Heat exchangers are often associated with drawbacks like a large pressure drop or a non-uniform flow distribution. Recent research shows that bionic structures can provide possible improvements. We considered a set of such structures that were designed with M. Hermann's FracTherm {sup registered} algorithm. In order to optimize and compare them with conventional heat exchangers, we developed a numerical method to determine their performance. We simulated the flow in the heat exchanger applying a network model and coupled these results with a finite volume method to determine the heat distribution in the heat exchanger. (orig.)
A revised correlation based on heat transfer model of slug flow in mini/micro-channels
Li, Xuejiao; Jia, Li; Yin, Liaofei; An, Zhoujian
2017-07-01
As flow boiling in mini/micro-channel, slug flow was corresponding to the optimal heat transfer ability owing to the evaporation of thin liquid film. Based on the heat transfer mechanism of liquid film evaporation, a simplified heat transfer model of slug flow was proposed. Li-Wu heat transfer correlation (Int J Heat Mass Transf 53(9): 1778-1787, 2010) was revised by introducing evaporation parameter, C e . With the evaporation parameter, C e , the revised correlation predicted the slug flow database with MAE (Mean Absolute Error) 25.14%, which improved the prediction accuracy remarkably.
Heating patterns produced by shortwave diathermy applicators in tissue substitute models.
Lehmann, J F; McDougall, J A; Guy, A W; Warren, C G; Esselman, P C
1983-12-01
To be a deep-heating modality, shortwave diathermy applicators have to heat the musculature more than the subcutaneous fat. In this study, commercially available and prototype shortwave diathermy applicators were tested using tissue substitute models which allow rapid thermographic scanning of the initial linear transient temperature rise in the subcutaneous fat and muscle. The specific absorption rates (SAR) of the electromagnetic radiation were calculated throughout the tissues. Great differences were found in the deep-heating capability of these applicators. Some of the applicators heated the subcutaneous fat more than the muscle, while others were more efficient in heating the musculature.
Cognata, Thomas J.; Leimkuehler, Thomas; Sheth, Rubik; Le, Hung
2013-01-01
The Fusible Heat Sink is a novel vehicle heat rejection technology which combines a flow through radiator with a phase change material. The combined technologies create a multi-function device able to shield crew members against Solar Particle Events (SPE), reduce radiator extent by permitting sizing to the average vehicle heat load rather than to the peak vehicle heat load, and to substantially absorb heat load excursions from the average while constantly maintaining thermal control system setpoints. This multi-function technology provides great flexibility for mission planning, making it possible to operate a vehicle in hot or cold environments and under high or low heat load conditions for extended periods of time. This paper describes the modeling and experimental validation of the Fusible Heat Sink technology. The model developed was intended to meet the radiation and heat rejection requirements of a nominal MMSEV mission. Development parameters and results, including sizing and model performance will be discussed. From this flight-sized model, a scaled test-article design was modeled, designed, and fabricated for experimental validation of the technology at Johnson Space Center thermal vacuum chamber facilities. Testing showed performance comparable to the model at nominal loads and the capability to maintain heat loads substantially greater than nominal for extended periods of time.
Stream Heat Budget Modeling of Groundwater Inputs: Model Development and Validation
Glose, A.; Lautz, L. K.
2012-12-01
Models of physical processes in fluvial systems are useful for improving understanding of hydrologic systems and for predicting future conditions. Process-based models of fluid flow and heat transport in fluvial systems can be used to quantify unknown spatial and temporal patterns of hydrologic fluxes, such as groundwater discharge, and to predict system response to future change. In this study, a stream heat budget model was developed and calibrated to observed stream water temperature data for Meadowbrook Creek in Syracuse, NY. The one-dimensional (longitudinal), transient stream temperature model is programmed in Matlab and solves the equations for heat and fluid transport using a Crank-Nicholson finite difference scheme. The model considers four meteorologically driven heat fluxes: shortwave solar radiation, longwave radiation, latent heat flux, and sensible heat flux. Streambed conduction is also considered. Input data for the model were collected from June 13-18, 2012 over a 500 m reach of Meadowbrook Creek, a first order urban stream that drains a retention pond in the city of Syracuse, NY. Stream temperature data were recorded every 20 m longitudinally in the stream at 5-minute intervals using iButtons (model DS1922L, accuracy of ±0.5°C, resolution of 0.0625°C). Meteorological data, including air temperature, solar radiation, relative humidity, and wind speed, were recorded at 5-minute intervals using an on-site weather station. Groundwater temperature was measured in wells adjacent to the stream. Stream dimensions, bed temperatures, and type of bed sediments were also collected. A constant rate tracer injection of Rhodamine WT was used to quantify groundwater inputs every 10 m independently to validate model results. Stream temperatures fluctuated diurnally by ~3-5 °C during the observation period with temperatures peaking around 2 pm and cooling overnight, reaching a minimum between 6 and 7 am. Spatially, the stream shows a cooling trend along the
Immunomodulatory effect of Hawthorn extract in an experimental stroke model.
Elango, Chinnasamy; Devaraj, Sivasithambaram Niranjali
2010-12-30
increased Foxp3-positive T(regs) in the brain, which may have aided in suppression of activated inflammatory cells. Such treatment also minimizes apoptotic cell death by influencing STAT-3 phosphorylation and Bcl-xL expression in the brain. Taken together, the immunomodulatory effect of Hawthorn extract may play a critical role in the neuroprotection observed in this MCAO-induced stroke model.
Immunomodulatory effect of Hawthorn extract in an experimental stroke model
Directory of Open Access Journals (Sweden)
Devaraj Sivasithambaram
2010-12-01
with I/R-induced injury, boosted IL-10 levels, and increased Foxp3-positive Tregs in the brain, which may have aided in suppression of activated inflammatory cells. Such treatment also minimizes apoptotic cell death by influencing STAT-3 phosphorylation and Bcl-xL expression in the brain. Taken together, the immunomodulatory effect of Hawthorn extract may play a critical role in the neuroprotection observed in this MCAO-induced stroke model.
SIMPLIFIED BUILDING MODELS EXTRACTION FROM ULTRA-LIGHT UAV IMAGERY
Directory of Open Access Journals (Sweden)
O. Küng
2012-09-01
Full Text Available Generating detailed simpliﬁed building models such as the ones present on Google Earth is often a difﬁcult and lengthy manual task, requiring advanced CAD software and a combination of ground imagery, LIDAR data and blueprints. Nowadays, UAVs such as the AscTec Falcon 8 have reached the maturity to offer an affordable, fast and easy way to capture large amounts of oblique images covering all parts of a building. In this paper we present a state-of-the-art photogrammetry and visual reconstruction pipeline provided by Pix4D applied to medium resolution imagery acquired by such UAVs. The key element of simpliﬁed building models extraction is the seamless integration of the outputs of such a pipeline for a ﬁnal manual reﬁnement step in order to minimize the amount of manual work.
Modeling of oil extraction from olive foot cake using hexane
Directory of Open Access Journals (Sweden)
Fellag, Hocine
2001-12-01
Full Text Available In this work, the influences of the factors, which can have effect on oil extraction from olive foot cake using hexane, are studied. From the experimental results, a mathematical model for calculation of the extraction yield is proposed. The statistical tests used to obtain this model show that the yield does not depend on the granulometry and the stirring rate, but depends on the temperature, the contact time and the liquid-solid ratio (L/S. Also, it depends on interactions between time and temperature and interactions between time and L/S. The comparison of the results given by the experiment and the model allows us to say that the model is satisfactory.En este artículo se estudia la influencia de los factores que pueden tener efecto en la extracción del aceite de orujo usando hexano. Se propone a partir de los resultados experimentales, un modelo matemático para el cálculo del rendimiento de la extracción. Los tests estadísticos utilizados para obtener este modelo mostraron que el rendimiento no depende de la granulometría ni de la velocidad de agitación, pero si depende de la temperatura, del tiempo de contacto y de la relación líquido-sólido (L/S. También depende de las interacciones entre el tiempo y la temperatura y entre el tiempo y la relación L/S. La comparación entre los resultados experimentales y el modelo nos permite decir que dicho modelo es satisfactorio.
A mathematical model of the distillation units with heat pump
Directory of Open Access Journals (Sweden)
A. V. Zhuchkov
2013-01-01
Full Text Available Efficient hardware design of the rectification process and reduce energy costs for their implementation is an urgent task. The mathematical description of the alcohol distillation process using a heat pump was obtained in this study.
Present-day heat flow model of Mars
National Research Council Canada - National Science Library
Laura M Parro; Alberto Jiménez-díaz; Federico Mansilla; Javier Ruiz
2017-01-01
Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere...
Thermal Heat and Power Production with Models for Local and Regional Energy Systems
Energy Technology Data Exchange (ETDEWEB)
Saether, Sturla
1999-07-01
The primary goal of this thesis is the description and modelling of combined heat and power systems as well as analyses of thermal dominated systems related to benefits of power exchange. Large power plants with high power efficiency (natural gas systems) and heat production in local heat pumps can be favourable in areas with low infrastructure of district heating systems. This system is comparable with typical combined heat and power (CHP) systems based on natural gas with respect to efficient use of fuel energy. The power efficiency obtainable from biomass and municipal waste is relatively low and the advantage of CHP for this system is high compared to pure power production with local heat pumps for heat generation. The advantage of converting pure power systems into CHP systems is best for power systems with low power efficiency and heat production at low temperature. CHP systems are divided into two main groups according to the coupling of heat and power production. Some CHP systems, especially those with strong coupling between heat and power production, may profit from having a thermal heat storage subsystem. District heating temperatures direct the heat to power ratio of the CHP units. The use of absorption chillers driven by district heating systems are also evaluated with respect to enhancing the utilisation of district heating in periods of low heat demand. Power exchange between a thermal dominated and hydropower system is found beneficial. Use of hydropower as a substitute for peak power production in thermal dominated systems is advantageous. Return of base load from the thermal dominated system to the hydropower system can balance in the net power exchange.
Model-Based Information Extraction From Synthetic Aperture Radar Signals
Matzner, Shari A.
2011-07-01
Synthetic aperture radar (SAR) is a remote sensing technology for imaging areas of the earth's surface. SAR has been successfully used for monitoring characteristics of the natural environment such as land cover type and tree density. With the advent of higher resolution sensors, it is now theoretically possible to extract information about individual structures such as buildings from SAR imagery. This information could be used for disaster response and security-related intelligence. SAR has an advantage over other remote sensing technologies for these applications because SAR data can be collected during the night and in rainy or cloudy conditions. This research presents a model-based method for extracting information about a building -- its height and roof slope -- from a single SAR image. Other methods require multiple images or ancillary data from specialized sensors, making them less practical. The model-based method uses simulation to match a hypothesized building to an observed SAR image. The degree to which a simulation matches the observed data is measured by mutual information. The success of this method depends on the accuracy of the simulation and on the reliability of the mutual information similarity measure. Electromagnetic theory was applied to relate a building's physical characteristics to the features present in a SAR image. This understanding was used to quantify the precision of building information contained in SAR data, and to identify the inputs needed for accurate simulation. A new SAR simulation technique was developed to meet the accuracy and efficiency requirements of model-based information extraction. Mutual information, a concept from information theory, has become a standard for measuring the similarity between medical images. Its performance in the context of matching a simulation image to a SAR image was evaluated in this research, and it was found to perform well under certain conditions. The factors that affect its performance
Numerical simulation of heat and mass transfer in a 3D model of a loop heat pipe evaporator
Directory of Open Access Journals (Sweden)
Aleksey A. Pozhilov
2017-10-01
Full Text Available The article presents results of 3D numerical simulation of flow and conjugate heat and mass transfer in a model of the TacSat-4 satellite loop heat pipe evaporator. The mathematical model includes the Reynolds-averaged Navier–Stokes equations describing the flow in the liquid and vapor regions, Darcy's law for filtration modeling in the wicks and the energy equation with accurate coupling of connected sub-domains including effects of evaporation on interfaces between the porous and vapor regions. According to the simulation results, the evaporation localizes mainly at the vapor groove corners near the evaporator body. The vapor grooves operate under essentially different conditions, as a result, the flow rates differ by several times. Significant thickening of the evaporator body yields only weak reduction in a level of the grooves’ flow rate non-uniformity.
Energy Technology Data Exchange (ETDEWEB)
Suthar, K. J.; Lurie, Alexander M.; Den Hartog, P.
2016-01-01
Heat pipes and vapour chambers work on heat exchange phenomena of two-phase flow and are widely used for in-dustrial and commercial applications. These devices offer very high effective thermal conductivities (5,000-200,000 W/m/K) and are adaptable to various sizes, shapes, and ori-entations. Although they have been found to be an excel-lent thermal management solution for laptops, satellites, and many things in-between, heat pipes and vapour cham-bers have yet to be adopted for use at particle accelerator facilities where they offer the possibility of more compact and more efficient means to remove heat from unwanted synchrotron radiation. As with all technologies, there are inherent limitations. Foremost, they are limited by practi-cality to serve as local heat transfer devices; heat transfer over long distances is likely best provided by other means. Heat pipes also introduce unique failure modes which must be considered.
Fractional model for heat conduction in polar bear hairs
Directory of Open Access Journals (Sweden)
Wang Qing-Li
2012-01-01
Full Text Available Time-fractional differential equations can accurately describe heat conduction in fractal media, such as wool fibers, goose down and polar bear hair. The fractional complex transform is used to convert time-fractional heat conduction equations with the modified Riemann-Liouville derivative into ordinary differential equations, and exact solutions can be easily obtained. The solution process is straightforward and concise.
Numerical Modeling of Transient Heat Transfer in Longitudinal Fin
Farshad Panahizadeh; Mohammed Hasnat; Ashkan Ghafour
2017-01-01
The main objective of the present numerical study is to investigate the transient heat transfer in one kind of all-purpose longitudinal fin with the triangular profile. The lateral surface of the concerned fin and the tip of it are subjected to general situations included heat flux at the base and insulation on the tip. For this study developed a one dimensional in house code written by Fortran 90 programming language by using finite difference method with an implicit scheme...
Simulation models and performance assessment of district heating substations
Vaillant Rebollar, Julio; Himpe, Eline; Janssens, Arnold
2014-01-01
Development of new technologies and methodologies regarding district heating substation operational control strategies are increasingly found nowadays. At the same time a great number of modern buildings are provided with energy monitoring and control systems which supervise and collect operating data from different energy components. Accordingly, an exemplary district heating systems is being implemented in the city of Kortrijk in Belgium, as part of a demonstration zero-carbon neighbo...
Large Scale Solar Heating:Evaluation, Modelling and Designing
Heller, Alfred; Svendsen, Svend; Furbo, Simon
2001-01-01
The main objective of the research was to evaluate large-scale solar heating connected to district heating (CSDHP), to build up a simulation tool and to demonstrate the application of the simulation tool for design studies and on a local energy planning case. The evaluation was mainly carried out based on measurements on the Marstal plant, Denmark, and through comparison with published and unpublished data from other plants. Evaluations on the thermal, economical and environmental performance...
National Research Council Canada - National Science Library
Chiou, Guo-Li
2013-01-01
.... The purpose of this study, therefore, was first to investigate 30 physics students’ mental models of heat convection, and then to examine the relationship between their mental models and predictions of convection-related phenomena...
Shoda, Munehito; Yokoyama, Takaaki; Suzuki, Takeru K.
2018-02-01
We propose a novel one-dimensional model that includes both shock and turbulence heating and qualify how these processes contribute to heating the corona and driving the solar wind. Compressible MHD simulations allow us to automatically consider shock formation and dissipation, while turbulent dissipation is modeled via a one-point closure based on Alfvén wave turbulence. Numerical simulations were conducted with different photospheric perpendicular correlation lengths {λ }0, which is a critical parameter of Alfvén wave turbulence, and different root-mean-square photospheric transverse-wave amplitudes δ {v}0. For the various {λ }0, we obtain a low-temperature chromosphere, high-temperature corona, and supersonic solar wind. Our analysis shows that turbulence heating is always dominant when {λ }0≲ 1 {Mm}. This result does not mean that we can ignore the compressibility because the analysis indicates that the compressible waves and their associated density fluctuations enhance the Alfvén wave reflection and therefore the turbulence heating. The density fluctuation and the cross-helicity are strongly affected by {λ }0, while the coronal temperature and mass-loss rate depend weakly on {λ }0.
A predictive mathematical model was developed to simulate heat transfer in a tomato undergoing double sided infrared (IR) heating in a dry-peeling process. The aims of this study were to validate the developed model using experimental data and to investigate different engineering parameters that mos...
GMDH-GA Hybrid Model Extracting Exon Region from DNA Sequences
Ohta, Kouji; Yoshihara, Ikuo; Yamamori, Kunihito; Yasunaga, Moritoshi
2004-01-01
Abstract ###A model building method based on Group Method of Data Handling (GMDH) optimized by ###GA is developed for extracting exon regions. GMDH, that is originally a method to construct ###higher order polynomial model, is extended to constructing higher order logical model. ###The model built by proposed method is compared with Genetic Programming (GP)-based ###model as to the extraction rate of best, worst and average. The proposed method is superior to GP ###as to extraction rate of al...
Antioxidative properties of Iberis amara extracts in biochemical model reactions.
Schempp, Harald; Toth, Angela; Weiser, Dieter; Elstner, Erich F
2003-01-01
Gastro-intestinal disorders such as the non-ulcer dyspepsia and irritable bowel syndrome expatiate on/with inflammatory processes of the gastro-intestinal mucosa. Iberogast is used in treatment of such disorders. Iberis amara L. extract (IAE) is one of nine components of the drug. There is increasing evidence that mediators of inflammation processes in the stomach and intestine include reactive oxygen species (ROS), arising from several enzymic reactions characteristic for inflammatory events. In this study it was shown that Iberis amara extract (STW 6) has the potential for scavenging ROS, dependent on the individual test system. Biochemical model reactions relevant for the formation of ROS in vivo at inflammatory sites were used. Inhibition of the formation of ROS could be shown to be excellent in test systems known to preferentially produce reactive species (myeloperoxidase-generated HOCl, peroxynitrite) with high affinities to sulfur-containing compounds, e.g. mustard oil glycosides such as glucoiberin. Furthermore ROS, generated during xanthine oxidase (XOD)-catalysed oxidation of xanthine into uric acid, were also efficiently decreased by IAE. However, an inhibition of XOD could be excluded, but chelation of metal ions (Fe, Cu) decreasing their redox-cycling activities seems to play a role. A major activity of IAE proved to represent inhibition of lipid peroxidation processes, shown as delay of the lag phase of the Cu(II)-induced LDL oxidation as well as protection of alpha-linolenic acid from peroxidation by singlet oxygen.
A model for allometric scaling of mammalian metabolism with ambient heat loss
Kwak, Ho Sang
2016-02-02
Background Allometric scaling, which represents the dependence of biological trait or process relates on body size, is a long-standing subject in biological science. However, there has been no study to consider heat loss to the ambient and an insulation layer representing mammalian skin and fur for the derivation of the scaling law of metabolism. Methods A simple heat transfer model is proposed to analyze the allometry of mammalian metabolism. The present model extends existing studies by incorporating various external heat transfer parameters and additional insulation layers. The model equations were solved numerically and by an analytic heat balance approach. Results A general observation is that the present heat transfer model predicted the 2/3 surface scaling law, which is primarily attributed to the dependence of the surface area on the body mass. External heat transfer effects introduced deviations in the scaling law, mainly due to natural convection heat transfer which becomes more prominent at smaller mass. These deviations resulted in a slight modification of the scaling exponent to a value smaller than 2/3. Conclusion The finding that additional radiative heat loss and the consideration of an outer insulation fur layer attenuate these deviation effects and render the scaling law closer to 2/3 provides in silico evidence for a functional impact of heat transfer mode on the allometric scaling law in mammalian metabolism.
Dynamics of heat, water, and soluble gas exchange in the human airways: 1. A model study.
Tsu, M E; Babb, A L; Ralph, D D; Hlastala, M P
1988-01-01
In order to provide a means for analysis of heat, water, and soluble gas exchange with the airways during tidal ventilation, a one dimensional theoretical model describing heat and water exchange in the respiratory airways has been extended to include soluble gas exchange with the airway mucosa and water exchange with the mucous layer lining the airways. Not only do heat, water, and gas exchange occur simultaneously, but they also interact. Heating and cooling of the airway surface and mucous lining affects both evaporative water and soluble gas exchange. Water evaporation provides a major source of heat exchange. The model-predicted mean airway temperature profiles agree well with literature data for both oral and nasal breathing validating that part of the model. With model parameters giving the best fit to experimental data, the model shows: (a) substantial heat recovery in the upper airways, (b) minimal respiratory heat and water loss, and (c) low average mucous temperatures and maximal increases in mucous thickness. For resting breathing of room air, heat and water conservation appear to be more important than conditioning efficiency. End-tidal expired partial pressures of very soluble gases eliminated by the lungs are predicted to be lower than the alveolar partial pressures due to the absorption of the expired gases by the airway mucosa. The model may be usable for design of experiments to examine mechanisms associated with the local hydration and dehydration dynamics of the mucosal surface, control of bronchial perfusion, triggering of asthma, mucociliary clearance and deposition of inhaled pollutant gases.
Modeling and dynamic control simulation of unitary gas engine heat pump
Energy Technology Data Exchange (ETDEWEB)
Zhao Yang [Department of Thermal Energy Engineering, Tianjin University, Tianjin 300072 (China)], E-mail: Zhaoyang@tju.edu.cn; Haibo Zhao; Zheng Fang [Department of Thermal Energy Engineering, Tianjin University, Tianjin 300072 (China)
2007-12-15
Based on the dynamic model of the gas engine heat pump (GEHP) system, an intelligent control simulation is presented to research the dynamic characteristics of the system in the heating operation. The GEHP system simulation model consists of eight models for its components including a natural gas engine, a compressor, a condenser, an expansion valve, an evaporator, a cylinder jacket heat exchanger, an exhaust gas heat exchanger and an auxiliary heater. The intelligent control model is composed of the prediction controller model and the combined controller model. The Runge-Kutta Fehlberg fourth-fifth order algorithms are used to solve the differential equations. The results show that the model is very effective in analyzing the effects of the control system, and the steady state accuracy of the intelligent control scheme is higher than that of the fuzzy controller.
A coordinated dispatch model for electricity and heat in a Microgrid via particle swarm optimization
DEFF Research Database (Denmark)
Xu, Lizhong; Yang, Guangya; Xu, Zhao
2013-01-01
, detailed combined heat and power (CHP) model is developed. The part load performance of CHP is modeled by curve fitting method. Furthermore, electric heater is introduced into the model to improve the economy of Microgrid operation and enhance the flexibility of the Microgrid by electricity-heat conversion......This paper develops a coordinated electricity and heat dispatching model for Microgrid under day-ahead environment. In addition to operational constraints, network loss and physical limits are addressed in this model, which are always ignored in previous work. As an important component of Microgrid....... Particle swarm optimization (PSO) is employed to solve this model for the operation schedule to minimize the total operational cost of Microgrid by coordinating the CHP, electric heater, boiler and heat storage. The efficacy of the model and methodology is verified with different operation scenarios....
MODELING OF AN ADVANCED HEAT EXCHANGE UNIT WITH MICROCHANNELS FOR A COMBINED PHOTOENERGY SYSTEM
Directory of Open Access Journals (Sweden)
R. V. Zaitsev
2017-06-01
Full Text Available Purpose. Mathematical modeling of the heat exchange unit main parameters for photoenergy system based on general models with forced circulation of heat transfer fluid. Methodology. To determine the coefficient of heat transfer at a given coolant temperature and surfaces temperature necessary to determine the temperature gradient in the wall of the heat exchanger. Temperature gradients can be determined by solving the equation of energy, which depends on the distribution of the flow rate in the flow. In general, a solution of convective heat transfer fluid to flow along the plane comes to solution of the system of differential equations. Results. In the paper features of the selection of theoretical basis and mathematical modeling of thermal processes in the heat exchange unit for combination photoenergy system are presented. As a result of the simulation conducted we improve and develop high-efficiency heat exchange unit with microchannels. Testing of the proposed unit proved its high efficiency through the implementation of turbulent flow of coolant with heat transfer coefficient at 18 kW/(m2×K. Analytical testing of the heat exchanger allowed showing that heat exchanger unit provides a stable operating temperature at less than 50 °C with the coolant flow rate is less than 0.3 m/s. Originality. Novelty of the proposed heat exchanger is in the optimal design of microchannels to improve the heat transfer coefficient. Practical value. The use of this heat exchanger will improve the quality and uniformity of cooling solar panels and reduce energy costs for circulation of fluid.
DEFF Research Database (Denmark)
Yang, Xiaochen; Li, Hongwei; Svendsen, Svend
2016-01-01
. In this study, electric heat tracing system was investigated as a solution to this dilemma. A model of electric heat tracing system for multi-storey buildings was built. Various pipe materials and insulation thicknesses as the parameters of the model were compared to make a comprehensive study. The performance......Low temperature district heating (LTDH) is a cost-efficient way of supplying space heating and domestic hot water (DHW) for buildings in urban areas. However, there is concern that the potential hygiene problems (Legionella) might occur if LTDH is implemented, especially for large buildings...... profiles to the model. The energy and economy performances of electric heat tracing system in different scenarios were simulated by Matlab. The results were compared to the conventional circulation system with the current generation district heating. The electric heat tracing system with LTDH showed good...
A minimal titration modelization of the mammalian dynamical heat shock response
Aude, Sivéry; Thommen, Quentin
2015-01-01
Environmental stress, such as oxidative or heat stress, induces the activation of the Heat Shock Response (HSR) which leads to an increase in the heat shock proteins (HSPs) level. These HSPs act as molecular chaperones to maintain proteostasis. Even if the main heat shock response partners are well known, a detailed description of the dynamical properties of the HSR network is still missing. In this study, we derive a minimal mathematical model of cellular response to heat shock that reproduces available experimental data sets both on transcription factor activity and cell viability. This simplistic model highlights the key mechanistic processes that rule the HSR network and reveals (i) the titration of Heat Shock Factor 1 (HSF1) by chaperones as the guiding line of the network, (ii) that protein triage governs the fate of damaged proteins and (iii) three different temperature regimes describing normal, acute or chronic stress.
Modeling of an Air Conditioning System with Geothermal Heat Pump for a Residential Building
Directory of Open Access Journals (Sweden)
Silvia Cocchi
2013-01-01
Full Text Available The need to address climate change caused by greenhouse gas emissions attaches great importance to research aimed at using renewable energy. Geothermal energy is an interesting alternative concerning the production of energy for air conditioning of buildings (heating and cooling, through the use of geothermal heat pumps. In this work a model has been developed in order to simulate an air conditioning system with geothermal heat pump. A ground source heat pump (GSHP uses the shallow ground as a source of heat, thus taking advantage of its seasonally moderate temperatures. GSHP must be coupled with geothermal exchangers. The model leads to design optimization of geothermal heat exchangers and to verify the operation of the geothermal plant.
Fractional single-phase-lagging heat conduction model for describing anomalous diffusion
Directory of Open Access Journals (Sweden)
T.N. Mishra
2016-03-01
Full Text Available The fractional single-phase-lagging (FSPL heat conduction model is obtained by combining scalar time fractional conservation equation to the single-phase-lagging (SPL heat conduction model. Based on the FSPL heat conduction model, anomalous diffusion within a finite thin film is investigated. The effect of different parameters on solution has been observed and studied the asymptotic behavior of the FSPL model. The analytical solution is obtained using Laplace transform method. The whole analysis is presented in dimensionless form. Numerical examples of particular interest have been studied and discussed in details.
Peron, D V; Fraga, S; Antelo, F
2017-10-01
The effect of temperature on the degradation of anthocyanins in juçara and "Italia" grape extracts was determined between 50 and 90°C. For both species, thermal degradation followed a first-order kinetic model. The decimal reduction time decreased with increasing temperature, and dependence on the thermodegradable factor was lower at higher temperatures. The anthocyanins from juçara degraded more slowly than those extracted from "Italia" grapes. The activation enthalpy and free energy of inactivation indicated an endothermic reaction, not spontaneous degradation, whereas the activation entropy suggested that the transition state has less structural freedom than that of the reactants. The antioxidant capacity of the extracts was reduced when subjected to 90°C heat treatment, however, significant quantities of this bioactive compound still remained. Copyright © 2017 Elsevier Ltd. All rights reserved.
Extracting software static defect models using data mining
Directory of Open Access Journals (Sweden)
Ahmed H. Yousef
2015-03-01
Full Text Available Large software projects are subject to quality risks of having defective modules that will cause failures during the software execution. Several software repositories contain source code of large projects that are composed of many modules. These software repositories include data for the software metrics of these modules and the defective state of each module. In this paper, a data mining approach is used to show the attributes that predict the defective state of software modules. Software solution architecture is proposed to convert the extracted knowledge into data mining models that can be integrated with the current software project metrics and bugs data in order to enhance the prediction. The results show better prediction capabilities when all the algorithms are combined using weighted votes. When only one individual algorithm is used, Naïve Bayes algorithm has the best results, then the Neural Network and the Decision Trees algorithms.
A model for the prediction of safe heat flux from a downward-facing hot patch
Energy Technology Data Exchange (ETDEWEB)
Reddy, C. Nowneswara; Jayanti, S., E-mail: sjayanti@iitm.ac.in
2013-12-15
Highlights: • Elucidation of the effect inclination on bubble size and shape. • Computational model for heat transfer under film boiling conditions. • Elucidation of heat leakage from a hot patch. • Development of a dimensionless correlation for safe heat flux. - Abstract: Pool boiling from the underside of flat, downward-facing patch is important in analyzing possible accident scenarios related to nuclear power generation. Significant deterioration in heat transfer may occur in stationary film boiling leading to high wall temperatures. In the present work, we have studied, experimentally and through computational fluid dynamics simulations, the nature of the bubbles that are formed at a hot patch. Noting that large, flattened bubbles can be formed at a heated surface, we develop a heat transfer-only model which takes into account the conduction within the plate and the convective and boiling heat transfer to the surrounding liquid medium. It is shown that the safe heat flux, beyond which significant wall temperature rise may occur, is very small compared the critical heat flux for thick plates made of poorly conducting materials. A dimensionless correlation is proposed to calculate the safe heat flux.
Clinic expert information extraction based on domain model and block importance model.
Zhang, Yuanpeng; Wang, Li; Qian, Danmin; Geng, Xingyun; Yao, Dengfu; Dong, Jiancheng
2015-11-01
To extract expert clinic information from the Deep Web, there are two challenges to face. The first one is to make a judgment on forms. A novel method based on a domain model, which is a tree structure constructed by the attributes of query interfaces is proposed. With this model, query interfaces can be classified to a domain and filled in with domain keywords. Another challenge is to extract information from response Web pages indexed by query interfaces. To filter the noisy information on a Web page, a block importance model is proposed, both content and spatial features are taken into account in this model. The experimental results indicate that the domain model yields a precision 4.89% higher than that of the rule-based method, whereas the block importance model yields an F1 measure 10.5% higher than that of the XPath method. Copyright © 2015 Elsevier Ltd. All rights reserved.
Witherspoon, L R; Shuler, S E; Alyea, K; Husserl, F E
1983-10-01
Heat inactivation has been proposed as an alternative to perchloric acid (PCA) precipitation for the extraction of carcinoembryonic antigen (CEA) from human plasma. We examined a commercial RIA kit using heat inactivation, and compared results with those obtained with PCA precipitation. Adequate sensitivity (1.5 micrograms CEA/l plasma), satisfactory analytical recovery of CEA added to plasma, and dilutional linearity of samples found to have elevated CEA concentrations, were demonstrated for the heat-inactivation assay. Between-assay precision was better with the heat inactivation than with the PCA assay. Although the absolute concentration of CEA estimated after heat inactivation was consistently lower than that estimated after PCA extraction of plasma specimens, there was excellent correlation between results obtained with the two methods in colon cancer patients free of disease, colon cancer patients with residual or recurrent disease, patients with benign gastrointestinal disease, and in patients with chronic renal failure. We conclude that the heat-inactivation assay is an excellent alternative to the PCA assay.
Energy Technology Data Exchange (ETDEWEB)
Witherspoon, L.R.; Shuler, S.E.; Alyea, K.; Husserl, F.E.
1983-10-01
Heat inactivation has been proposed as an alternative to perchloric acid (PCA) precipitation for the extraction of carcinoembryonic antigen (CEA) from human plasma. A commercial RIA kit using heat inactivation was examined and results compared with those obtained with PCA precipitation. Adequate sensitivity (1.5 ..mu..g CEA/I plasma), satisfactory analytical recovery of CEA added to plasma, and dilutional linearity of samples found to have elevated CEA concentrations, were demonstrated for the heat-inactivation assay. Between-assay precision was better with the heat inactivation than with the PCA assay. Although the absolute concentration of CEA estimated after heat inactivation was consistently lower than that estimated after PCA extraction of plasma specimens, there was excellent correlation between results obtained with the two methods in colon cancer patients free of disease, colon cancer patients with residual or recurrent disease, patients with benign gastrointestinal disease, and in patients with chronic renal failure. The heat-inactivation assay is an excellent alternative to the PCA assay.
Mathematical modelling of thermal and flow processes in vertical ground heat exchangers
Directory of Open Access Journals (Sweden)
Pater Sebastian
2017-12-01
Full Text Available The main task of mathematical modelling of thermal and flow processes in vertical ground heat exchanger (BHE-Borehole Heat Exchanger is to determine the unit of borehole depth heat flux obtainable or transferred during the operation of the installation. This assignment is indirectly associated with finding the circulating fluid temperature flowing out from the U-tube at a given inlet temperature of fluid in respect to other operational parameters of the installation.
Leithner Reinhard; Askarova Aliya; Bolegenova Saltanat; Bolegenova Symbat; Maximov Valeriy; Ospanova Shinar; Ergalieva Aigul; Nugymanova Aizhan; Beketayeva Meruyert
2016-01-01
In this paper the results obtained by the method of numerical modelling of Ekibastuz coal burning in furnace of Kazakhstan Power Plant. Numerical experiment was carried out on the basis of three-dimensional equations of convective heat and mass transfer, taking into account the heat propagation, heat radiation, chemical reactions and multiphase structure of the medium to predict the influence of different water content in coal on overall furnace operation and formation of combustion products.
Directory of Open Access Journals (Sweden)
Leithner Reinhard
2016-01-01
Full Text Available In this paper the results obtained by the method of numerical modelling of Ekibastuz coal burning in furnace of Kazakhstan Power Plant. Numerical experiment was carried out on the basis of three-dimensional equations of convective heat and mass transfer, taking into account the heat propagation, heat radiation, chemical reactions and multiphase structure of the medium to predict the influence of different water content in coal on overall furnace operation and formation of combustion products.
Energy Technology Data Exchange (ETDEWEB)
Seiler, J.M.; Bonnet, J.M.; Bernaz, L. [CEA Grenoble (France)
2001-07-01
Extensive studies have been performed to investigate the heat transfer within a molten corium pool (homogeneous, stratified and with miscibility gap): Synthesis of heat transfer correlations in molten pool (homogeneous and stratified), Focusing effect in stratified metal layer, DNS analysis of Rayleigh Benard instabilities at the top boundary; interpretation of the different convection regimes and exponents affecting the Rayleigh number in the heat transfer correlations, Molten pool model for corium presenting a miscibility gap. Condition for de-stratification. (authors)
CFD modeling of heat transfer in a rectangular channel with dimplepin finning
Directory of Open Access Journals (Sweden)
Spokoiny M. Yu.
2013-05-01
Full Text Available Using the CFD modeling method, the authors have investigated conjugate heat transfer in a rectangular channel with dimple-pin finning with hight of pins, depth of cavities and Reynolds number values varying in the range, characteristic for heat exchangers designed for liquid cooling of microelectronic devices, such as microprocessors. Criterion dependencies for calculation of heat transfer under these conditions have been obtained.
Design and modelling of a novel compact power cycle for low temperature heat sources
DEFF Research Database (Denmark)
Wronski, Jorrit; Skovrup, Morten Juel; Elmegaard, Brian
2012-01-01
Power cycles for the efficient use of low temperature heat sources experience increasing attention. This paper describes an alternative cycle design that offers potential advantages in terms of heat source exploitation. A concept for a reciprocating expander is presented that performs both, work...... calculation results for use with a steady state cycle evaluation. An organic Rankine cycle model is developed and used for a comparison. The performance of the expander itself and the different requirements regarding heat source and temperature levels are studied....
Chen, Jiajia; Pitchai, Krishnamoorthy; Birla, Sohan; Negahban, Mehrdad; Jones, David; Subbiah, Jeyamkondan
2014-10-01
A 3-dimensional finite-element model coupling electromagnetics and heat and mass transfer was developed to understand the interactions between the microwaves and fresh mashed potato in a 500 mL tray. The model was validated by performing heating of mashed potato from 25 °C on a rotating turntable in a microwave oven, rated at 1200 W, for 3 min. The simulated spatial temperature profiles on the top and bottom layer of the mashed potato showed similar hot and cold spots when compared to the thermal images acquired by an infrared camera. Transient temperature profiles at 6 locations collected by fiber-optic sensors showed good agreement with predicted results, with the root mean square error ranging from 1.6 to 11.7 °C. The predicted total moisture loss matched well with the observed result. Several input parameters, such as the evaporation rate constant, the intrinsic permeability of water and gas, and the diffusion coefficient of water and gas, are not readily available for mashed potato, and they cannot be easily measured experimentally. Reported values for raw potato were used as baseline values. A sensitivity analysis of these input parameters on the temperature profiles and the total moisture loss was evaluated by changing the baseline values to their 10% and 1000%. The sensitivity analysis showed that the gas diffusion coefficient, intrinsic water permeability, and the evaporation rate constant greatly influenced the predicted temperature and total moisture loss, while the intrinsic gas permeability and the water diffusion coefficient had little influence. This model can be used by the food product developers to understand microwave heating of food products spatially and temporally. This tool will allow food product developers to design food package systems that would heat more uniformly in various microwave ovens. The sensitivity analysis of this study will help us determine the most significant parameters that need to be measured accurately for reliable
Application of a New Dynamic Heating System Model Using a Range of Common Control Strategies
Directory of Open Access Journals (Sweden)
Joshua Fong
2016-06-01
Full Text Available This research investigates the overall heating energy consumptions using various control strategies, secondary heat emitters, and primary plant for a building. Previous research has successfully demonstrated that a dynamic distributed heat emitter model embedded within a simplified third-order lumped parameter building model is capable of achieving improved results when compared to other commercially available modelling tools. With the enhanced ability to capture transient effects of emitter thermal capacity, this research studies the influence of control strategies and primary plant configurations on the rate of energy consumption of a heating system. Four alternative control strategies are investigated: zone feedback; weather-compensated; a combination of both of these methods; and thermostatic control. The plant alternative configurations consist of conventional boilers, biomass boilers, and heat pumps supporting radiator heating and underfloor heating. The performance of the model is tested on a primary school building and can be applied to any residential or commercial building with a heating system. Results show that the new methods reported offer greater detail and rigor in the conduct of building energy modelling.
Discussion on the Heat and Mass Transfer Model on the Pool Surface
Energy Technology Data Exchange (ETDEWEB)
Hong, Soon-Joon; Choo, Yeon-Jun [FNC Tech., Yongin (Korea, Republic of); Ha, Sang-Jun [KHNP Central Research Institute, Daejeon (Korea, Republic of)
2016-10-15
Heat transfer on the pool surface involves the evaporation and condensation of steam in the presence of non-condensable gas. It is a kind of inter-phase heat transfer. This phenomenon has been regarded as less important on the thermal hydraulic behaviors such as pressure, temperature, hydrogen distribution, and so on in the nuclear reactor containment building. As a matter of fact, several RAIs (requests for additional information) during the licensing review of the developed CAP have been presented. And early in 2000s the steam condensation on the water surface of IRWST was a concern of APR1400 design. Such an increased concern is believed because it is a newly adopted system. This study discusses the pool surface heat transfer by reviewing the models of several well-known containment analysis codes, and conducting the sensitivities. This study discussed the pool surface heat transfer. The related models of CAP, GOTHIC, CONTEMPT-LT, and CONTEMPT4 were compared. The sensitivity of heat transfer coefficient for SKN3 and 4 using conventional code CONTEMPT-LT/028-A showed little effect. And the sensitivity of relative humidity and heat transfer area for latent heat transfer shows that CAP locates between GOTHIC and CONTEMPT4/MOD. The sensitivity for sensible heat transfer also shows similar trend. Conclusively, current CAP model of pool surface heat transfer has no fatal defect.
Johnston, C. D.; Hood, A. W.; Cargill, P. J.; De Moortel, I.
2017-08-01
We proposed that the use of an approximate "jump condition" at the solar transition region permits fast and accurate numerical solutions of the one dimensional hydrodynamic equations when the corona undergoes impulsive heating. In particular, it eliminates the need for the very short timesteps imposed by a highly resolved numerical grid. This paper presents further examples of the applicability of the method for cases of non-uniform heating, in particular, nanoflare trains (uniform in space but non-uniform in time) and spatially localised impulsive heating, including at the loop apex and base of the transition region. In all cases the overall behaviour of the coronal density and temperature shows good agreement with a fully resolved one dimensional model and is significantly better than the equivalent results from a 1D code run without using the jump condition but with the same coarse grid. A detailed assessment of the errors introduced by the jump condition is presented showing that the causes of discrepancy with the fully resolved code are (I) the neglect of the terms corresponding to the rate of change of total energy in the unresolved atmosphere; (II) mass motions at the base of the transition region and (III) for some cases with footpoint heating, an over-estimation of the radiative losses in the transition region.
Analysis and Modeling of Heat Generation in Overcharged Li-Ion Battery with Passive Cooling
DEFF Research Database (Denmark)
Coman, Paul Tiberiu; Veje, Christian
2013-01-01
by coupling a one-dimensional model of the electrochemical processes with a two-dimensional model for the heat transfer in a cross section of a battery pack. The heat generation and subsequent temperature rise is analyzed for different charging currents for the two cases where the cell is air-cooled...... and passively cooled using a PCM, respectively. As expected, the results show that for high currents, the heat generation and implicitly the temperature increases. However, using a PCM the temperature increase is found to be limited allowing the battery to be overcharged to a certain degree. It is found......This paper presents a dynamic model for simulating the heat generation in Lithium batteries and an investigation of the heat transfer as well as the capacity of Phase Change Materials (PCM’s) to store energy inside a battery cell module when the battery is overcharged. The study is performed...
Koch, Andrew S.; Chimento, Clio A.; Berg, Allison N.; Mughal, Farah D.; Spencer, Jean-Paul; Hovland, Douglas E.; Mbadugha, Bessie; Hovland, Allan K.; Eller, Leah R.
2015-01-01
Two methods for the extraction of maltol from Fraser fir needles are performed and compared in this two-week experiment. A traditional benchtop extraction using dichloromethane is compared to a microwave-assisted extraction using aqueous ethanol. Students perform both procedures and weigh the merits of each technique. In doing so, students see a…
Complex Model of Induction Heating - Demounting of Shaft Flange
Directory of Open Access Journals (Sweden)
Milan Krasl
2004-01-01
Full Text Available This paper deals with exemplary solutions of one specifies problem of induction heating. This problem was partly determined by means of numerical method as a light-coupling problem. Numerical solutions were calculated with the help of professional programs (Ansys, Fluent, QuickField. Results of the solution and comparison with measurements are discussed in conclusion.
Kinetic modelling of reactions in heated disaccharide-casein systems
Brands, C.M.J.; Boekel, van M.A.J.S.
2003-01-01
The reactions occurring in disaccharide-casein reaction mixtures during heating at 120 degreesC and pH 6.8 were studied. The existence of two main degradation routes were established: (1) Isomerisation of the aldose sugars lactose and maltose in their ketose isomers lactulose and maltulose,
Chemical simulation modeling of heat transfer in LMFBRs
Energy Technology Data Exchange (ETDEWEB)
Wiberg, D V
1980-04-01
A chemical reaction conducted in a wax cylinder was used in this study to simulate a CDA occurring in a reactor. The exothermic reaction of dimethyl sulfoxide (DMSO) with acetyl chloride (AC) was used as the chemical reaction to simulate the internally heated liquid pool. SUN-3420 wax was used to construct the cylindrical reaction vessel to simulate cladding and containment.
Model predictive control of a waste heat recovery system for automotive diesel engines
Feru, E.; Willems, F.; De Jager, B.; Steinbuch, M.
2014-01-01
In this paper, a switching Model Predictive Control strategy is designed for an automotive Waste Heat Recovery system with two parallel evaporators. The objective is to maximize Waste Heat Recovery system output power, while satisfying safe operation under highly dynamic disturbances from the
A Three-Fold Approach to the Heat Equation: Data, Modeling, Numerics
Spayd, Kimberly; Puckett, James
2016-01-01
This article describes our modeling approach to teaching the one-dimensional heat (diffusion) equation in a one-semester undergraduate partial differential equations course. We constructed the apparatus for a demonstration of heat diffusion through a long, thin metal rod with prescribed temperatures at each end. The students observed the physical…
Experimental validation of a dynamic waste heat recovery system model for control purposes
Feru, E.; Kupper, F.; Rojer, C.; Seykens, X.L.J.; Scappin, F.; Willems, F.P.T.; Smits, J.; Jager, B. de; Steinbuch, M.
2013-01-01
This paper presents the identification and validation of a dynamic Waste Heat Recovery (WHR) system model. Driven by upcoming CO2 emission targets and increasing fuel costs, engine exhaust gas heat utilization has recently attracted much attention to improve fuel efficiency, especially for
Modeling and analysis of a transcritical rankine power cycle with a low grade heat source
DEFF Research Database (Denmark)
Nguyen, Chan; Veje, Christian
efficiency, exergetic efficiency and specific net power output. A generic cycle configuration has been used for analysis of a geothermal energy heat source. This model has been validated against similar calculations using industrial waste heat as the energy source. Calculations are done with fixed...
Modelling of Temperature Profiles and Transport Scaling in Auxiliary Heated Tokamaks
DEFF Research Database (Denmark)
Callen, J.D.; Christiansen, J.P.; Cordey, J.G.
1987-01-01
-mode) scaling with input power, . The constant heat pinch or excess temperature gradient model leads to the offset linear law for the total stored energy W with Pin, W = τinc Pin + W(0), which describes JET auxiliary heating data quite well. It also provides definitions for the incremental energy confinement...
Temperature dependence of electronic heat capacity in Holstein model of DNA
Fialko, N.; Sobolev, E.; Lakhno, V.
2016-04-01
The dynamics of charge migration was modeled to calculate temperature dependencies of its thermodynamic equilibrium values such as energy and electronic heat capacity in homogeneous adenine fragments. The energy varies from nearly polaron one at T ∼ 0 to midpoint of the conductivity band at high temperatures. The peak on the graph of electronic heat capacity is observed at the polaron decay temperature.
A modified force-restore approach to modeling snow-surface heat fluxes
Charles H. Luce; David G. Tarboton
2001-01-01
Accurate modeling of the energy balance of a snowpack requires good estimates of the snow surface temperature. The snow surface temperature allows a balance between atmospheric heat fluxes and the conductive flux into the snowpack. While the dependency of atmospheric fluxes on surface temperature is reasonably well understood and parameterized, conduction of heat from...
John F. Hunt; Hongmei Gu
2006-01-01
The anisotropy of wood complicates solution of heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment, earlywood/latewood differences, or...
Directory of Open Access Journals (Sweden)
Fazle Mabood
2015-01-01
Full Text Available The heat flow patterns profiles are required for heat transfer simulation in each type of the thermal insulation. The exothermic reaction models in porous medium can prescribe the problems in the form of nonlinear ordinary differential equations. In this research, the driving force model due to the temperature gradients is considered. A governing equation of the model is restricted into an energy balance equation that provides the temperature profile in conduction state with constant heat source on the steady state. The proposed optimal homotopy asymptotic method (OHAM is used to compute the solutions of the exothermic reactions equation.
Farrokhpanah, Amirsaman; Bussmann, Markus; Mostaghimi, Javad
2017-04-01
When modelling phase change, the latent heat released (absorbed) during solidification (melting) must be included in the heat transfer equation. In this paper, different SPH methods for the implementation of latent heat, in the context of transient heat conduction, are derived and tested. First, SPH discretizations of two finite element methods are presented, but these prove to be computationally expensive. Then, by starting from a simple approximation and enhancing accuracy using different numerical treatments, a new SPH method is introduced, that is fast and easy to implement. An evaluation of this new method on various analytical and numerical results confirms its accuracy and robustness.
Modelling the mechanical response of an idealized ice stream to variations in geothermal heat flux
Smith-Johnsen, Silje; de Fleurian, Basile; Hestnes Nisancioglu, Kerim
2017-04-01
The spatial distribution of geothermal heat flux beneath the Greenland Ice Sheet is largely unknown partly due to difficulties in accessing the bed, and bore hole data providing point measurements only. Studies using tectonic, seismic and magnetic models to retrieve the geothermal heat flux show very different results indicating large uncertainties. However, modelling studies point to a geothermal heat flux anomaly that may influence the Northeast Greenland Ice Stream (NEGIS). Previous studies have investigated the impact of the uncertainty in geothermal heatflux on ice dynamics. These studies are mainly focusing on the impact on the ice rheology as the basal condition are derived from inverse modelling methods (including the geothermal heat flux variability in the variability of the friction coefficient). Another important feedback is the increase in subglacial meltwater production which may affect the sliding velocities of an ice stream, and has not been taken into account in preceding studies. In this study we investigate the impact of variations in geothermal heat flux on ice dynamics by analysing the mechanical response of a synthetic ice stream simulating NEGIS using the Ice Sheet System Model (Larour et al. 2012). We present results from model experiments using different heat flux configurations, friction laws and a hydrology model, showing the importance of geothermal heat flux on basal conditions of fast flowing ice.
Semi-structured data extraction and modelling: the WIA Project
Directory of Open Access Journals (Sweden)
Alessandro Mosca
2013-09-01
Full Text Available Over the last decades, the amount of data of all kinds available electronically has increased dramatically. Data are accessible through a range of interfaces including Web browsers, database query languages, application-specific interfaces, built on top of a number of different data exchange formats. All these data span from un-structured to highly structured data. Very often, some of them have structure even if the structure is implicit, and not as rigid or regular as that found in standard database systems. Spreadsheet documents are prototypical in this respect. Spreadsheets are the lightweight technology able to supply companies with easy to build business management and business intelligence applications, and business people largely adopt spreadsheets as smart vehicles for data files generation and sharing. Actually, the more spreadsheets grow in complexity (e.g., their use in product development plans and quoting, the more their arrangement, maintenance, and analysis appear as a knowledge-driven activity. The algorithmic approach to the problem of automatic data structure extraction from spreadsheet documents (i.e., grid-structured and free topological-related data emerges from the WIA project: Worksheets Intelligent Analyser. The WIA-algorithm shows how to provide a description of spreadsheet contents in terms of higher level of abstractions or conceptualisations. In particular, the WIA-algorithm target is about the extraction of i the calculus work-flow implemented in the spreadsheets formulas and ii the logical role played by the data which take part into the calculus. The aim of the resulting conceptualisations is to provide spreadsheets with abstract representations useful for further model refinements and optimizations through evolutionary algorithms computations.
Lucato, Jeanette Janaina Jaber; Adams, Alexander Bernard; Souza, Rogério; Torquato, Jamili Anbar; Carvalho, Carlos Roberto Ribeiro; Marini, John J
2009-01-01
To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37 degrees C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.
Thermal-Hydraulics analysis of pressurized water reactor core by using single heated channel model
Directory of Open Access Journals (Sweden)
Reza Akbari
2017-08-01
Full Text Available Thermal hydraulics of nuclear reactor as a basis of reactor safety has a very important role in reactor design and control. The thermal-hydraulic analysis provides input data to the reactor-physics analysis, whereas the latter gives information about the distribution of heat sources, which is needed to perform the thermal-hydraulic analysis. In this study single heated channel model as a very fast model for predicting thermal hydraulics behavior of pressurized water reactor core has been developed. For verifying the results of this model, we used RELAP5 code as US nuclear regulatory approved thermal hydraulics code. The results of developed single heated channel model have been checked with RELAP5 results for WWER-1000. This comparison shows the capability of single heated channel model for predicting thermal hydraulics behavior of reactor core.
Directory of Open Access Journals (Sweden)
Michel Feidt
2010-12-01
Full Text Available The purpose of this work is to precise and complete one recently proposed in the literature and relative to a general criterion to maximize the first law efficiency of irreversible heat engines. It is shown that the previous proposal seems to be a particular case. A new proposal has been developed for a Carnot irreversible thermomechanical heat engine at steady state associated to two infinite heat reservoirs (hot source, and cold sink: this constitutes the studied system. The presence of heat leak is accounted for, with the most simple form, as is done generally in the literature. Irreversibility is modeled through , created internal entropy rate in the converter (engine, and , total created entropy rate in the system. Heat transfer laws are represented as general functions of temperatures. These concepts are particularized to the most common heat transfer law (linear one. Consequences of the proposal are examined; some new analytical results are proposed for efficiencies.
Ali, M. E.; Sandeep, N.
The knowledge of heat transfer in MHD nanofluid flows over different geometries is very important for heat exchangers design, transpiration, fiber coating, etc. Recent days, heat transfer of non-Newtonian nanofluids plays a major role in manufacturing processes due to its shear thinning and thickening properties. Naturally, magnetite (Fe3O4) nanoparticles move randomly within the base fluid. By applying the transverse magnetic field, the motion of those nanoparticles becomes uniform. This phenomenon is very useful in heat transfer processes. With this initiation, a mathematical model is developed to investigate the heat transfer behaviour of electrically conducting MHD flow of a Casson nanofluid over a cone, wedge and a plate. We consider a Cattaneo-Christov heat flux model with variable source/sink and nonlinear radiation effects. We also considered water as the base fluid suspended with magnetite nanoparticles. R-K-Felhberg-integration scheme is employed to resolve the altered governing nonlinear equations. Impacts of governing parameters on common profiles (temperature and velocity) are conversed (in three cases). By viewing the same parameters, the friction factor coefficient and heat transfer rate are discussed with the assistance of tables. It is found that the boundary layers (thermal and flow) over three geometries (cone, wedge and a plate) are not uniform. It is also found that the thermal relaxation parameter effectively enhances the heat local Nusselt number and the heat transfer performance is high in the flow over a wedge when compared with the flows over a cone and plate.
DEFF Research Database (Denmark)
Xin, Gao; Andreasen, Søren Juhl; Chen, Min
2012-01-01
This paper presents a numerical model of an exhaust heat recovery system for a high temperature polymer electrolyte membrane fuel cell (HTPEMFC) stack. The system is designed as thermoelectric generators (TEGs) sandwiched in the walls of a compact plate-fin heat exchanger. Its model is based...
Directory of Open Access Journals (Sweden)
L. Bannehr
2012-09-01
Full Text Available Remote sensing methods are used to obtain different kinds of information about the state of the environment. Within the cooperative research project HiReSens, funded by the German BMBF, a hyperspectral scanner, an airborne laser scanner, a thermal camera, and a RGB-camera are employed on a small aircraft to determine roof material parameters and heat bridges of house tops over the city Oldenburg, Lower Saxony. HiReSens aims to combine various geometrical highly resolved data in order to achieve relevant evidence about the state of the city buildings. Thermal data are used to obtain the energy distribution of single buildings. The use of hyperspectral data yields information about material consistence of roofs. From airborne laser scanning data (ALS digital surface models are inferred. They build the basis to locate the best orientations for solar panels of the city buildings. The combination of the different data sets offers the opportunity to capitalize synergies between differently working systems. Central goals are the development of tools for the collection of heat bridges by means of thermal data, spectral collection of roofs parameters on basis of hyperspectral data as well as 3D-capture of buildings from airborne lasers scanner data. Collecting, analyzing and merging of the data are not trivial especially not when the resolution and accuracy is aimed in the domain of a few decimetre. The results achieved need to be regarded as preliminary. Further investigations are still required to prove the accuracy in detail.
Modeling of Heat Transfer in Rooms in the Modelica "Buildings" Library
Energy Technology Data Exchange (ETDEWEB)
Wetter, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zuo, Wangda [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nouidui, Thierry Stephane [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2011-11-01
This paper describes the implementation of the room heat transfer model in the free open-source Modelica \\Buildings" library. The model can be used as a single room or to compose a multizone building model. We discuss how the model is decomposed into submodels for the individual heat transfer phenomena. We also discuss the main physical assumptions. The room model can be parameterized to use different modeling assumptions, leading to linear or non-linear differential algebraic systems of equations. We present numerical experiments that show how these assumptions affect computing time and accuracy for selected cases of the ANSI/ASHRAE Standard 140- 2007 envelop validation tests.
Heat engines at optimal power: Low-dissipation versus endoreversible model
Johal, Ramandeep S.
2017-07-01
The low-dissipation model and the endoreversible model of heat engines are two of the most commonly studied models of machines in finite-time thermodynamics. In this paper we compare the performance characteristics of these two models under optimal power output. We point out a basic equivalence between them, in the linear response regime.
DEFF Research Database (Denmark)
Nielsen, Toke Rammer; Rose, Jørgen; Kragh, Jesper
2009-01-01
In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer...... must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements...... on a prototype heat exchanger for cold climates....
An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers.
White, M J; Nellis, G F; Kelin, S A; Zhu, W; Gianchandani, Y
2010-11-01
Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.
An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers
Nellis, G. F.; Kelin, S. A.; Zhu, W.; Gianchandani, Y.
2010-01-01
Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid. PMID:20976021
Modelling sub-daily latent heat fluxes from a small reservoir
McGloin, Ryan; McGowan, Hamish; McJannet, David; Burn, Stewart
2014-11-01
Accurate methods of latent heat flux quantification are essential for water management and for use in hydrological and meteorological models. Currently the effect of small lakes in most numerical weather prediction modelling systems is either entirely ignored or crudely parameterized. In order to test methods for modelling hourly latent heat flux from small water bodies, this study compares results from several modelling approaches to values measured by the eddy covariance method at an agricultural reservoir in southeast Queensland, Australia. Mass transfer estimates of LE calculated using the theoretical mass transfer model and using the Tanny et al. (2008) and Sacks et al. (1994) bulk transfer coefficients showed the best relationship with measured values under a range of meteorological conditions. The theoretical model showed the strongest correlation with measured values, while the Tanny et al. (2008) and Sacks et al. (1994) models had regression equation slopes with the closest proximity to 1. Latent heat fluxes estimated using the Granger and Hedstrom (2011) evaporation model, that was specifically developed for use at small reservoirs, showed a poor relationship with measured values, particularly in stable atmospheric conditions. The 1-dimensional hydrodynamics model, DYRESM, was used to obtain predictions of hourly latent heat flux without the use of water surface temperature measurements. DYRESM estimates of latent heat flux showed a slightly worse relationship with measured values than those predicted using the traditional mass transfer models (which used measurements of water surface temperature). However, DYRESM performed considerably better than the Granger and Hedstrom (2011) model.
MODELLING SLOW EXTRACTION INDUCED RADIOACTIVITY IN SPS LSS2
Araujo Martinez, Aurora Cecilia; CERN. Geneva. TE Department
2017-01-01
The Accelerator and Beam Transfer (ABT) group is investigating the impact of recent proposals to extract higher proton intensities to Fixed Target experiments at the SPS. The 400 GeV high-energy proton beam is typically extracted over a few seconds using a resonant slow-extraction technique that induces small but unavoidable beam losses on the extraction equipment in SPS LSS2. In this report, the induced radioactivity for 2016-2017 is used to predict future activation levels and cool-down times, using a past intervention as a reference to predict dose to the personnel carrying-out maintenance of the accelerator.
Model-based Optimization of Pectin Extraction Process
DEFF Research Database (Denmark)
Kim, Boeun; André Fernandes Caroço, Ricardo; Huusom, Jakob Kjøbsted
2017-01-01
Commercial pectin produced through an extraction using acid is used as a gelling, thickening, emulsifying or stabilizing agent in many applications due to its gelling ability. Quality of the gel formed by pectin depends on physical and chemical characteristics of extracted pectin, such as degree...... of esterification (DE) and intrinsic viscosity (IV). However, since there is a trade-off between the pectin yield and quality, it becomes a challenge to decide the extraction condition using heuristic approaches. In this study, we propose a strategy for an operation optimization of the pectin extraction process...
l MODEL CALCULATION OF THE HEAT CONTENT OF TECHNICAL
African Journals Online (AJOL)
sing the glass, with Cp(glass) being calculated as a linear combination of the partial heat capacities of the different oxides. ..... 131. 9. Thuret. A. J. Soc. Glass Technol. 1936, 20, 680. 10. Maier. C.G.; Kelley, KK. J. Am. Chem. Soc. 1932, 54, 3243. Stebbins, J.F.; Carmichael, I.S.E.; Moret, L.K. Contrib. Mineral. Petrol. 1984, 8:5»,
Modelling of droplet heating and evaporation: recent results and unsolved problems
Energy Technology Data Exchange (ETDEWEB)
Sazhin, S S; Elwardany, A; Gusev, I G; Heikal, M R [Sir Harry Ricardo Laboratories, School of Computing, Engineering and Mathematics, University of Brighton, Brighton, BN2 4GJ UK (United Kingdom); Shishkova, I N, E-mail: S.Sazhin@brighton.ac.uk [Low Temperature Department, Moscow Power Engineering Institute, Moscow 111250 (Russian Federation)
2011-01-01
The most recent results referring to the hydrodynamic and kinetic modelling of droplet heating and evaporation are briefly summarised. Two new solutions to the heat conduction equation, taking into account the effect of the moving boundary during transient heating of an evaporating droplet, are discussed. The first solution is the explicit analytical solution to this equation, while the second one reduces the solution of the differential transient heat conduction equation to the solution of the Volterra integral equation of the second kind. It has been pointed out that the new approach predicts lower droplet surface temperatures and slower evaporation rates compared with the traditional approach. A simplified model for multi-component droplet heating and evaporation, based on the analytical solution of the species diffusion equation inside droplets, is reviewed. A new algorithm, based on simple approximations of the kinetic results for droplet radii and temperatures, suitable for engineering applications, is discussed.
A GPU Heterogeneous Cluster Scheduling Model for Preventing Temperature Heat Island
Directory of Open Access Journals (Sweden)
Cao Yun-Peng
2017-01-01
Full Text Available With the development of GPU general-purpose computing, GPU heterogeneous cluster has become a widely used parallel data processing solution in modern data center. Temperature management and controlling has become a new research hotspot in big data continuous computing. Temperature heat island in cluster has important influence on computing reliability and energy efficiency. In order to prevent the occurrence of GPU cluster temperature heat island, a big data task scheduling model for preventing temperature heat island was proposed. In this model, temperature, reliability and computing performance are taken into account to reduce node performance difference and improve throughput per unit time in cluster. Temperature heat islands caused by slow nodes are prevented by optimizing scheduling. The experimental results show that the proposed scheme can control node temperature and prevent the occurrence of temperature heat island under the premise of guaranteeing computing performance and reliability.
Model for Determining Geographical Distribution of Heat Saving Potentials in Danish Building Stock
DEFF Research Database (Denmark)
Petrovic, Stefan; Karlsson, Kenneth Bernard
2014-01-01
. A highly detailed model for determining heat demand, possible heat savings and associated costs in the Danish building stock is presented. Both scheduled and energy-saving renovations until year 2030 have been analyzed. The highly detailed GIS-based heat atlas for Denmark is used as a container for storing...... data about physical properties for 2.5 million buildings in Denmark. Consequently, the results of the analysis can be represented on a single building level. Under the assumption that buildings with the most profitable heat savings are renovated first, the consequences of heat savings for the economy...... and energy system have been quantified and geographically referenced. The possibilities for further improvements of the model and the application to other geographical regions have been discussed....
A large-scale sensitivity study of urban heat islands using GFDL's earth system model
Li, D.; Gu, Y.
2016-12-01
Most previous sensitivity studies of urban heat islands focus on the impact of surface characteristics (including urban geometry and material properties). In this study, we analyze the influence of atmospheric forcing on simulated urban heat islands over the Continental United States (CONUS) using GFDL's earth system model coupled with a newly developed urban canopy model, with a specific focus on the impact of precipitation. It is shown that in summer the simulated urban heat islands generally increase with increasing precipitation amount over the CONUS while in winter precipitation has little impact on the simulated urban heat islands. From a simulation perspective, changing both atmospheric forcing and surface characteristics has important impacts on the simulated urban heat islands and the relative importance varies spatially. Similarly, the relative importance of precipitation among all atmospheric forcing variables varies spatially. Hotspots where precipitation is particularly important are identified.
Numerical Modeling of Transient Heat Transfer in Longitudinal Fin
Directory of Open Access Journals (Sweden)
Farshad Panahizadeh
2017-11-01
Full Text Available The main objective of the present numerical study is to investigate the transient heat transfer in one kind of all-purpose longitudinal fin with the triangular profile. The lateral surface of the concerned fin and the tip of it are subjected to general situations included heat flux at the base and insulation on the tip. For this study developed a one dimensional in house code written by Fortran 90 programming language by using finite difference method with an implicit scheme in unsteady state condition. Generally, the result of this study in time variation state after 700 seconds is steady. The results also show the fin efficiency by increasing the time of study decreases due to a reduction in the total heat transfer which is happened in the fin. The grid independence study shows that for the number of nodes greater than 20 the result will not be changed and same as before. Finally, the result of Fortran code verified by commercial CFD code which relies on finite difference method and it was shown have a consistent agreement
Chemical simulation modeling of heat transfer in LMFBRs
Energy Technology Data Exchange (ETDEWEB)
Wiberg, D V
1980-04-01
A chemical reaction conducted in a wax cylinder was used in this study to simulate a CDA occurring in a reactor. The exothermic reaction of dimethyl sulfoxide (DMSO) with acetyl chloride (AC) was used as the chemical reaction to simulate the internally heated liquid pool. SUN-3420 wax was used to construct the cylindrical reaction vessel to simulate cladding and containment. During a CDA, a question remains as to whether the containment would be miscible in the molten fuel. To allow for the possibility that either may be true, two cases were evaluated in this study. By using acetone as the solvent in the DMSO and AC solutions, the case in which the vessel was relatively insoluble in the reaction mixture was simulated. By using benzene as the solvent in the DMSO and AC solution, the case in which the molten vessel was more soluble in the reaction mixture was simulated. Based on the findings of this work the proposed heat transfer correlations for volumetrically heated liquid pools may be used with greater confidence as to their accuracy and applicability.
A simple model of the effect of ocean ventilation on ocean heat uptake
Energy Technology Data Exchange (ETDEWEB)
Nadiga, Balasubramanya T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Urban, Nathan Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2018-01-27
Presentation includes slides on Earth System Models vs. Simple Climate Models; A Popular SCM: Energy Balance Model of Anomalies; On calibrating against one ESM experiment, the SCM correctly captures that ESM's surface warming response with other forcings; Multi-Model Analysis: Multiple ESMs, Single SCM; Posterior Distributions of ECS; However In Excess of 90% of TOA Energy Imbalance is Sequestered in the World Oceans; Heat Storage in the Two Layer Model; Heat Storage in the Two Layer Model; Including TOA Rad. Imbalance and Ocean Heat in Calibration Improves Repr., but Significant Errors Persist; Improved Vertical Resolution Does Not Fix Problem; A Series of Expts. Confirms That Anomaly-Diffusing Models Cannot Properly Represent Ocean Heat Uptake; Physics of the Thermocline; Outcropping Isopycnals and Horizontally-Averaged Layers; Local interactions between outcropping isopycnals leads to non-local interactions between horizontally-averaged layers; Both Surface Warming and Ocean Heat are Well Represented With Just 4 Layers; A Series of Expts. Confirms That When Non-Local Interactions are Allowed, the SCMs Can Represent Both Surface Warming and Ocean Heat Uptake; and Summary and Conclusions.
New approaches to the modelling of multi-component fuel droplet heating and evaporation
Sazhin, Sergei S
2015-02-25
The previously suggested quasi-discrete model for heating and evaporation of complex multi-component hydrocarbon fuel droplets is described. The dependence of density, viscosity, heat capacity and thermal conductivity of liquid components on carbon numbers n and temperatures is taken into account. The effects of temperature gradient and quasi-component diffusion inside droplets are taken into account. The analysis is based on the Effective Thermal Conductivity/Effective Diffusivity (ETC/ED) model. This model is applied to the analysis of Diesel and gasoline fuel droplet heating and evaporation. The components with relatively close n are replaced by quasi-components with properties calculated as average properties of the a priori defined groups of actual components. Thus the analysis of the heating and evaporation of droplets consisting of many components is replaced with the analysis of the heating and evaporation of droplets consisting of relatively few quasi-components. It is demonstrated that for Diesel and gasoline fuel droplets the predictions of the model based on five quasi-components are almost indistinguishable from the predictions of the model based on twenty quasi-components for Diesel fuel droplets and are very close to the predictions of the model based on thirteen quasi-components for gasoline fuel droplets. It is recommended that in the cases of both Diesel and gasoline spray combustion modelling, the analysis of droplet heating and evaporation is based on as little as five quasi-components.
Energy Technology Data Exchange (ETDEWEB)
Tabares Velasco, P. C.
2011-04-01
This presentation discusses estimating heat and mass transfer processes in green roof systems: current modeling capabilities and limitations. Green roofs are 'specialized roofing systems that support vegetation growth on rooftops.'
Energy Efficiency Modelling of Residential Air Source Heat Pump Water Heater
Directory of Open Access Journals (Sweden)
Cong Toan Tran
2016-03-01
Full Text Available The heat pump water heater is one of the most energy efficient technologies for heating water for household use. The present work proposes a simplified model of coefficient of performance and examines its predictive capability. The model is based on polynomial functions where the variables are temperatures and the coefficients are derived from the Australian standard test data, using regression technics. The model enables to estimate the coefficient of performance of the same heat pump water heater under other test standards (i.e. US, Japanese, European and Korean standards. The resulting estimations over a heat-up phase and a full test cycle including a draw off pattern are in close agreement with the measured data. Thus the model allows manufacturers to avoid the need to carry out physical tests for some standards and to reduce product cost. The limitations of the methodology proposed are also discussed.
Heat exchange modeling in a multilayered karst aquifer affected by seawater intrusion
National Research Council Canada - National Science Library
Vettorello, Luca; Pedron, Roberto; Sottani, Andrea; Chieco, Michele
...) activity in a coastal aquifer in the South of Italy (Province of Lecce, Puglia Region). The modeled closed-loop system consists of two double u-pipe heat exchangers, installed in 200 meters deep boreholes...
Modeling Heat Flow In a Calorimeter Equipped With a Textured Solar Collector
Jaworske, Donald A.; Allen, Bradley J.
2001-01-01
Heat engines are being considered for generating electric power for minisatellite applications, particularly for those missions in high radiation threat orbits. To achieve this objective, solar energy must be collected and transported to the hot side of the heat engine. A solar collector is needed having the combined properties of high solar absorptance, low infrared emittance, and high thermal conductivity. To test candidate solar collector concepts, a simple calorimeter was designed, manufactured, and installed in a bench top vacuum chamber to measure heat flow. In addition, a finite element analysis model of the collector/calorimeter combination was made to model this heat flow. The model was tuned based on observations from the as-manufactured collector/calorimeter combination. In addition, the model was exercised to examine other collector concepts, properties, and scale up issues.
Heat Transfer Modeling and Validation for Optically Thick Alumina Fibrous Insulation
Daryabeigi, Kamran
2009-01-01
Combined radiation/conduction heat transfer through unbonded alumina fibrous insulation was modeled using the diffusion approximation for modeling the radiation component of heat transfer in the optically thick insulation. The validity of the heat transfer model was investigated by comparison to previously reported experimental effective thermal conductivity data over the insulation density range of 24 to 96 kg/cu m, with a pressure range of 0.001 to 750 torr (0.1 to 101.3 x 10(exp 3) Pa), and test sample hot side temperature range of 530 to 1360 K. The model was further validated by comparison to thermal conductivity measurements using the transient step heating technique on an insulation sample at a density of 144 kg/cu m over a pressure range of 0.001 to 760 torr, and temperature range of 290 to 1090 K.
Energy Technology Data Exchange (ETDEWEB)
Blair, N.; Mehos, M.; Christiansen, C.
2006-10-03
This poster, submitted for the CU Energy Initiative/NREL Symposium on October 3, 2006 in Boulder, Colorado, discusses the modeling, performance, cost, and financing of concentrating solar, photovoltaic, and solar heat systems.
FEFLOW finite element modeling of flow, mass and heat transport in porous and fractured media
Diersch, Hans-Jörg G
2013-01-01
Placing advanced theoretical and numerical methods in the hands of modeling practitioners and scientists, this book explores the FEFLOW system for solving flow, mass and heat transport processes in porous and fractured media. Offers applications and exercises.
Modeling and Optimization of a CoolingTower-Assisted Heat Pump System
National Research Council Canada - National Science Library
Xiaoqing Wei; Nianping Li; Jinqing Peng; Jianlin Cheng; Jinhua Hu; Meng Wang
2017-01-01
To minimize the total energy consumption of a cooling tower-assisted heat pump (CTAHP) system in cooling mode, a model-based control strategy with hybrid optimization algorithm for the system is presented in this paper...
Modeling of a heat pump charged with a non-azeotropic refrigerant mixture
Domanski, P.
1986-01-01
An analysis of the vapor compression cycle and the main components of an air-to-air heat pump charged with a binary non-azeotropic mixture has been performed for steady-state operation. The general heat pump simulation model HPBI has been formulated which is based on independent, analytical models of system components and the logic linking them together. The logic of the program requires an iterative solution of refrigerant pressure and enthalpy balances, and refrigerant mixture and individual mixture component mass inventories. The modeling effort emphasis was on the local thermodynamic phenomena which were described by fundamental heat transfer equations and equation of state relationships among material properties. In the compressor model several refrigerant locations were identified and the processes taking place between these locations accounted for all significant heat and pressure losses.
[Mass Transfer Kinetics Model of Ultrasonic Extraction of Pomegranate Peel Polyphenols].
Wang, Zhan-yi; Zhang, Li-hua; Wang, Yu-hai; Zhang, Yuan-hu; Ma, Li; Zheng, Dan-dan
2015-05-01
The dynamic mathematical model of ultrasonic extraction of polyphenols from pomegranate peel was constructed with the Fick's second law as the theoretical basis. The spherical model was selected, with mass concentrations of pomegranate peel polyphenols as the index, 50% ethanol as the extraction solvent and ultrasonic extraction as the extraction method. In different test conditions including the liquid ratio, extraction temperature and extraction time, a series of kinetic parameters were solved, such as the extraction process (k), relative raffinate rate, surface diffusion coefficient(D(S)), half life (t½) and the apparent activation energy (E(a)). With the extraction temperature increasing, k and D(S) were gradually increased with t½ decreasing,which indicated that the elevated temperature was favorable to the extraction of pomegranate peel polyphenols. The exponential equation of relative raffinate rate showed that the established numerical dynamics model fitted the extraction of pomegranate peel polyphenols, and the relationship between the reaction conditions and pomegranate peel polyphenols concentration was well reflected by the model. Based on the experimental results, a feasible and reliable kinetic model for ultrasonic extraction of polyphenols from pomegranate peel is established, which can be used for the optimization control of engineering magnifying production.
Vehicle Exhaust Waste Heat Recovery Model with Integrated Thermal Load Leveling
2015-08-01
advantages that make them particularly attractive for mobile applications including being lightweight , solid- state, and passive. This has the potential for...recovery from automobile engine. Energy. 2010;35:1447–1454. 14 12. Ceraianu MO, Gontean A. Parasitic elements modelling in thermoelectric...JP, Sampath S. Heat transfer modeling and geometry optimization of TEG for automobile applications. Proceedings of the ASME Summer Heat Transfer
Savvinova, Nadezhda A.; Sleptsov, Semen D.; Rubtsov, Nikolai A.
2017-11-01
A mathematical phase change model is a formulation of the Stefan problem. Various formulations of the Stefan problem modeling of radiative-conductive heat transfer during melting or solidification of a semitransparent material are presented. Analysis of numerical results show that the radiative heat transfer has a significant effect on temperature distributions during melting (solidification) of the semitransparent material. In this paper conditions for application of various statements of the Stefan problem are analyzed.
3D modeling of groundwater heat transport in the shallow Westliches Leibnitzer Feld aquifer, Austria
Rock, Gerhard; Kupfersberger, Hans
2018-02-01
For the shallow Westliches Leibnitzer feld aquifer (45 km2) we applied the recently developed methodology by Kupfersberger et al. (2017a) to derive the thermal upper boundary for a 3D heat transport model from observed air temperatures. We distinguished between land uses of grass and agriculture, sealed surfaces, forest and water bodies. To represent the heat flux from heated buildings and the mixture between different land surfaces in urban areas we ran the 1D vertical heat conduction module SoilTemp which is coupled to the heat transport model (using FEFLOW) on a time step basis. Over a simulation period of 23 years the comparison between measured and observed groundwater temperatures yielded NSE values ranging from 0.41 to 0.92 including readings at different depths. The model results showed that the thermal input signals lead to distinctly different vertical groundwater temperature distributions. To overcome the influence of specific warm or cold years we introduced the computation of an annual averaged groundwater temperature profile. With respect to the use of groundwater cooling or heating facilities we evaluated the application of vertically averaged statistical groundwater temperature distributions compared to the use of temperature distributions at selected dates. We concluded that the heat transport model serves well as an aquifer scale management tool to optimize the use of the shallow subsurface for thermal purposes and to analyze the impacts of corresponding measures on groundwater temperatures.
A thermoelectric power generating heat exchanger: Part II – Numerical modeling and optimization
DEFF Research Database (Denmark)
Sarhadi, Ali; Bjørk, Rasmus; Lindeburg, N.
2016-01-01
In Part I of this study, the performance of an experimental integrated thermoelectric generator (TEG)-heat exchanger was presented. In the current study, Part II, the obtained experimental results are compared with those predicted by a finite element (FE) model. In the simulation of the integrated...... TEG-heat exchanger, the thermal contact resistance between the TEG and the heat exchanger is modeled assuming either an ideal thermal contact or using a combined Cooper–Mikic–Yovanovich (CMY) and parallel plate gap formulation, which takes into account the contact pressure, roughness and hardness...
An axisymmetrical non-linear finite element model for induction heating in injection molding tools
DEFF Research Database (Denmark)
Guerrier, Patrick; Nielsen, Kaspar Kirstein; Menotti, Stefano
2016-01-01
To analyze the heating and cooling phase of an induction heated injection molding tool accurately, the temperature dependent magnetic properties, namely the non-linear B-H curves, need to be accounted for in an induction heating simulation. Hence, a finite element model has been developed...... in to the injection molding tool. The model shows very good agreement with the experimental temperature measurements. It is also shown that the non-linearity can be used without the temperature dependency in some cases, and a proposed method is presented of how to estimate an effective linear permeability to use...
Modeling the influence of potassium content and heating rate on biomass pyrolysis
DEFF Research Database (Denmark)
Trubetskaya, Anna; Surup, Gerrit; Shapiro, Alexander
2017-01-01
. The shrinking particle model considers internal and external heat transfer limitations and incorporates catalytic effects of potassium on the product yields. Modeling parameters were tuned with experimentally determined char yields at high heating rates (>200 K s−1) using a wire mesh reactor, a single particle...... burner, and a drop tube reactor. The experimental data demonstrated that heating rate and potassium content have significant effects on the char yield. The importance of shrinkage on the devolatilization time becomes greater with increasing particle size, but showed little influence on the char yields....
Modeling the film condensate fluid dynamics and heat transfer within the bubble membrane radiator
Energy Technology Data Exchange (ETDEWEB)
Pauley, K.A. [Pacific Northwest Lab., Richland, WA (United States); Thornborrow, J.O. [National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center
1992-01-01
An analytical model of the fluid dynamics and heat transfer characteristics of the condensate within the rotating Bubble Membrane Radiator is developed. The steady-state, three-dimensional heat transfer and flow equations were reduced to a set of third-order ordinary differential equations by employing similarity transformation techniques. These equations are then solved for the radial, axial, and angular flow distributions in the film condensate. Pressure, temperature, heat transfer, film thickness and mass flow rate distributions are also calculated. The analytical model is the basis of the SCRABBLE code which is used both as a zero-g design tool and a ground-test bed analyzer.
Model calculations for three-dimensional heat conduction in a real tooth
Foth, Hans-Jochen; Luke, Manfred
2003-06-01
To generate the three-dimensional grid net for a real tooth, an extracted tooth was grinded in steps of some millimetres from the top to the root. After each grinding step the displayed cross section was documented by photography showing clearly all transition lines between enamel, dentin and the pulp. The photographic reprints were used to determine the x-y-z-coordinates of selected points to represent the transition lines. In a fairly large-scale procedure these points were combined to a three dimensional net. FEM calculations were carried out to solve the heat equation numerically for the boundary condition that an IR laser pulse hits the surface for laser ablation. Since all the information of the various types of tissue is included in this model, the results give a huge variety of information. For example: the outer shell of enamel could be displayed exclusively to show its inner surface and which temperature distribution as well as mechanical stress got build up there.
European Regional Climate Zone Modeling of a Commercial Absorption Heat Pump Hot Water Heater
Energy Technology Data Exchange (ETDEWEB)
Sharma, Vishaldeep [ORNL; Shen, Bo [ORNL; Keinath, Chris [Stone Mountain Technologies, Inc., Johnson City; Garrabrant, Michael A. [Stone Mountain Technologies, Inc., Johnson City; Geoghegan, Patrick J [ORNL
2017-01-01
High efficiency gas-burning hot water heating takes advantage of a condensing heat exchanger to deliver improved combustion efficiency over a standard non-condensing configuration. The water heating is always lower than the gas heating value. In contrast, Gas Absorption Heat Pump (GAHP) hot water heating combines the efficiency of gas burning with the performance increase from a heat pump to offer significant gas energy savings. An ammonia-water system also has the advantage of zero Ozone Depletion Potential and low Global Warming Potential. In comparison with air source electric heat pumps, the absorption system can maintain higher coefficients of performance in colder climates. In this work, a GAHP commercial water heating system was compared to a condensing gas storage system for a range of locations and climate zones across Europe. The thermodynamic performance map of a single effect ammonia-water absorption system was used in a building energy modeling software that could also incorporate the changing ambient air temperature and water mains temperature for a specific location, as well as a full-service restaurant water draw pattern.
Valero, M; Sarrías, J A; Alvarez, D; Salmerón, M C
2006-06-01
The effect of electron beam irradiation (EBI) on Bacillus cereus spore heat resistance was investigated. Irradiation with accelerated electrons had an important heat-sensitizing effect on distilled-water spore suspensions. After irradiation doses of 1.3, 3.1, or 5.7 kGy followed by heating at 90 degrees C, calculated D(90)-values for strains Escuela Politécnica Superior de Orihuela (EPSO)-41WR and EPSO-50UR were reduced more than 1.3, 2.4, and 4.6 times, respectively. Plots of calculated log D(T)-values versus irradiation doses (1.3, 3.1, and 5.7 kGy) yielded straight parallel lines for the 85-100 degrees C heating temperature range, which made it possible to develop an equation to predict the changes in heat sensitivity of B. cereus spores that occurred with changing irradiation dose. Radiation-induced heat-sensitivity was characterized by a z(EBI)-value which was determined as the irradiation dose that should be required to reduce the decimal reduction time (D(T)) by one log(10) cycle when log(10)D(T) was plotted against irradiation treatment. A model is proposed to describe the influence of a pre-irradiation treatment with electron beams followed by heating on the heat resistance of B. cereus spores. This study also suggests the potential use of EBI followed by heating for food preservation.
GEOMETRY, HEAT REMOVAL AND KINETICS SCOPING MODELS FOR HYDROGEN STORAGE SYSTEMS
Energy Technology Data Exchange (ETDEWEB)
Hardy, B
2007-11-16
It is recognized that detailed models of proposed hydrogen storage systems are essential to gain insight into the complex processes occurring during the charging and discharging processes. Such insight is an invaluable asset for both assessing the viability of a particular system and/or for improving its design. The detailed models, however, require time to develop and run. Clearly, it is much more efficient to begin a modeling effort with a good system design and to progress from that point. To facilitate this approach, it is useful to have simplified models that can quickly estimate optimal loading and discharge kinetics, effective hydrogen capacities, system dimensions and heat removal requirements. Parameters obtained from these models can then be input to the detailed models to obtain an accurate assessment of system performance that includes more complete integration of the physical processes. This report describes three scoping models that assess preliminary system design prior to invoking a more detailed finite element analysis. The three models address the kinetics, the scaling and heat removal parameters of the system, respectively. The kinetics model is used to evaluate the effect of temperature and hydrogen pressure on the loading and discharge kinetics. As part of the kinetics calculations, the model also determines the mass of stored hydrogen per mass of hydride (in a particular reference form). As such, the model can determine the optimal loading and discharge rates for a particular hydride and the maximum achievable loading (over an infinite period of time). The kinetics model developed with the Mathcad{reg_sign} solver, runs in a mater of seconds and can quickly be used to identify the optimal temperature and pressure for either the loading or discharge processes. The geometry scoping model is used to calculate the size of the system, the optimal placement of heat transfer elements, and the gravimetric and volumetric capacities for a particular
3D numerical modeling of coupled phenomena in induced processes of heat treatment with malice
Directory of Open Access Journals (Sweden)
Triwong Peeteenut
2008-01-01
Full Text Available This paper describes a multi-method Malice package for three dimension coupled phenomena in induced processes of heat treatment by an algorithm weakly coupled with the Migen package integral method defining the electromagnetic model and the Flux-Expert package finite element method defining the thermal model. The integral method is well suited to inductive systems undergoing sinusoidal excitation at midrange or high frequency. The unknowns of both models are current density, scalar potential and temperature. Joule power in the electromagnetic model is generated by Eddy currents. It becomes the heat source in the thermal model.
Directory of Open Access Journals (Sweden)
Tao Zhi
2016-10-01
Full Text Available A variety of turbulence models were used to perform numerical simulations of heat transfer for hydrocarbon fuel flowing upward and downward through uniformly heated vertical pipes at supercritical pressure. Inlet temperatures varied from 373 K to 663 K, with heat flux ranging from 300 kW/m2 to 550 kW/m2. Comparative analyses between predicted and experimental results were used to evaluate the ability of turbulence models to respond to variable thermophysical properties of hydrocarbon fuel at supercritical pressure. It was found that the prediction performance of turbulence models is mainly determined by the damping function, which enables them to respond differently to local flow conditions. Although prediction accuracy for experimental results varied from condition to condition, the shear stress transport (SST and launder and sharma models performed better than all other models used in the study. For very small buoyancy-influenced runs, the thermal-induced acceleration due to variations in density lead to the impairment of heat transfer occurring in the vicinity of pseudo-critical points, and heat transfer was enhanced at higher temperatures through the combined action of four thermophysical properties: density, viscosity, thermal conductivity and specific heat. For very large buoyancy-influenced runs, the thermal-induced acceleration effect was over predicted by the LS and AB models.