Climate forcing and response to idealized changes in surface latent and sensible heat

International Nuclear Information System (INIS)

Ban-Weiss, George A; Cao Long; Pongratz, Julia; Caldeira, Ken; Bala, Govindasamy

2011-01-01

Land use and land cover changes affect the partitioning of latent and sensible heat, which impacts the broader climate system. Increased latent heat flux to the atmosphere has a local cooling influence known as 'evaporative cooling', but this energy will be released back to the atmosphere wherever the water condenses. However, the extent to which local evaporative cooling provides a global cooling influence has not been well characterized. Here, we perform a highly idealized set of climate model simulations aimed at understanding the effects that changes in the balance between surface sensible and latent heating have on the global climate system. We find that globally adding a uniform 1 W m -2 source of latent heat flux along with a uniform 1 W m -2 sink of sensible heat leads to a decrease in global mean surface air temperature of 0.54 ± 0.04 K. This occurs largely as a consequence of planetary albedo increases associated with an increase in low elevation cloudiness caused by increased evaporation. Thus, our model results indicate that, on average, when latent heating replaces sensible heating, global, and not merely local, surface temperatures decrease.

A state-of-the-art review on hybrid heat pipe latent heat storage systems

International Nuclear Information System (INIS)

Naghavi, M.S.; Ong, K.S.; Mehrali, M.; Badruddin, I.A.; Metselaar, H.S.C.

2015-01-01

The main advantage of latent heat thermal energy storage systems is the capability to store a large quantity of thermal energy in an isothermal process by changing phase from solid to liquid, while the most important weakness of these systems is low thermal conductivity that leads to unsuitable charging/discharging rates. Heat pipes are used in many applications – as one of the most efficient heat exchanger devices – to amplify the charging/discharging processes rate and are used to transfer heat from a source to the storage or from the storage to a sink. This review presents and critically discusses previous investigations and analysis on the incorporation of heat pipe devices into latent heat thermal energy storage with heat pipe devices. This paper categorizes different applications and configurations such as low/high temperature solar, heat exchanger and cooling systems, analytical approaches and effective parameters on the performance of hybrid HP–LHTES systems.

GPM SLH: Convective Latent Heating Estimated with GPM Dual-frequency Precipitation Radar Data

Science.gov (United States)

Takayabu, Y. N.; Hamada, A.; Yokoyama, C.; Ikuta, Y.; Shige, S.; Yamaji, M.; Kubota, T.

2017-12-01

Three dimensional diabatic heating distribution plays essential roles to determine large-scale circulation, as well as to generate mesoscale circulation associated with tropical convection (e.g. Hartmann et al., 1984; Houze et al. 1982). For mid-latitude systems also, diabatic heating contributes to generate PVs resulting in, for example, explosive intensifications of mid-lattitude storms (Boettcher and Wernli, 2011). Previously, with TRMM PR data, we developed a Spectral Latent Heating algorithm (SLH; Shige et al. 2004, etc.) for 36N-36S region. It was based on the spectral LH tables produced from a simulation utilizing the Goddard Cloud Ensemble Model forced with the TOGA-COARE data. With GPM DPR, the observation region is extended to 65N-65S. Here, we introduce a new version of SLH algorithm which is applicable also to the mid-latitude precipitation. A new global GPM SLH ver.5 product is released as one of NASA/JAXA GPM standard products on July 11, 2017. For GPM SLH mid-latitude algorithm, we employ the Japan Meteorological Agency (JMA)'s high resolution (horizontally 2km) Local Forecast Model (LFM) to construct the LUTs. With collaborations of JMA's forecast group, forecast data for 8 extratropical cyclone cases are collected and utilized. For mid-latitude precipitation, we have to deal with large temperature gradients and complex relationship between the freezing level and cloud base levels. LUTs are constructed for LH, Q1-QR, and Q2 (Yanai et al. 1973), for six different precipitation types: Convective and shallow stratiform LUTs are made against precipitation top heights. For deep stratiform and other precipitation, LUTs are made against maximum precipitation to handle the unknown cloud-bases. Finally, three-dimensional convective latent heating is retrieved, utilizing the LUTs and precipitation profile data from GPM 2AKu. We can confirm that retrieved LH looks very similar to simulated LH, for a consistency check. We also confirm a good continuities of

Comparative Assessment of Two Vegetation Fractional Cover Estimating Methods and Their Impacts on Modeling Urban Latent Heat Flux Using Landsat Imagery

Directory of Open Access Journals (Sweden)

Kai Liu

2017-05-01

Full Text Available Quantifying vegetation fractional cover (VFC and assessing its role in heat fluxes modeling using medium resolution remotely sensed data has received less attention than it deserves in heterogeneous urban regions. This study examined two approaches (Normalized Difference Vegetation Index (NDVI-derived and Multiple Endmember Spectral Mixture Analysis (MESMA-derived methods that are commonly used to map VFC based on Landsat imagery, in modeling surface heat fluxes in urban landscape. For this purpose, two different heat flux models, Two-source energy balance (TSEB model and Pixel Component Arranging and Comparing Algorithm (PCACA model, were adopted for model evaluation and analysis. A comparative analysis of the NDVI-derived and MESMA-derived VFCs showed that the latter achieved more accurate estimates in complex urban regions. When the two sources of VFCs were used as inputs to both TSEB and PCACA models, MESMA-derived urban VFC produced more accurate urban heat fluxes (Bowen ratio and latent heat flux relative to NDVI-derived urban VFC. Moreover, our study demonstrated that Landsat imagery-retrieved VFC exhibited greater uncertainty in obtaining urban heat fluxes for the TSEB model than for the PCACA model.

Comprehensive thermodynamic analysis of a renewable energy sourced hybrid heating system combined with latent heat storage

International Nuclear Information System (INIS)

Utlu, Zafer; Aydın, Devrim; Kıncay, Olcay

2014-01-01

Highlights: • An experimental thermal investigation of hybrid renewable heating system is presented. • Analyses were done by using real data obtained from a prototype structure. • Exergy efficiency of system components investigated during discharging period are close to each other as 32%. • The average input energy and exergy rates to the LHS were 0.770 and 0.027 kW. • Overall total energy and exergy efficiencies of LHS calculated as 72% and 28.4%. - Abstract: In this study an experimental thermal investigation of hybrid renewable heating system is presented. Latent heat storage stores energy, gained by solar collectors and supplies medium temperature heat to heat pump both day time also night time while solar energy is unavailable. In addition to this an accumulation tank exists in the system as sensible heat storage. It provides supply–demand balance with storing excess high temperature heat. Analyses were done according to thermodynamic’s first and second laws by using real data obtained from a prototype structure, built as part of a project. Results show that high percent of heat loses took place in heat pump with 1.83 kW where accumulator-wall heating cycle followed it with 0.42 kW. Contrarily highest break-down of exergy loses occur accumulator-wall heating cycle with 0.28 kW. Averagely 2.42 kW exergy destruction took place in whole system during the experiment. Solar collectors and heat pump are the promising components in terms of exergy destruction with 1.15 kW and 1.09 kW respectively. Exergy efficiency of system components, investigated during discharging period are in a close approximately of 32%. However, efficiency of solar collectors and charging of latent heat storage are 2.3% and 7% which are relatively low. Average overall total energy and exergy efficiencies of latent heat storage calculated as 72% and 28.4% respectively. Discharging energy efficiency of latent heat storage is the highest through all system components. Also heat

Estimation of sensible and latent heat flux from natural sparse vegetation surfaces using surface renewal

Science.gov (United States)

Zapata, N.; Martínez-Cob, A.

2001-12-01

This paper reports a study undertaken to evaluate the feasibility of the surface renewal method to accurately estimate long-term evaporation from the playa and margins of an endorreic salty lagoon (Gallocanta lagoon, Spain) under semiarid conditions. High-frequency temperature readings were taken for two time lags ( r) and three measurement heights ( z) in order to get surface renewal sensible heat flux ( HSR) values. These values were compared against eddy covariance sensible heat flux ( HEC) values for a calibration period (25-30 July 2000). Error analysis statistics (index of agreement, IA; root mean square error, RMSE; and systematic mean square error, MSEs) showed that the agreement between HSR and HEC improved as measurement height decreased and time lag increased. Calibration factors α were obtained for all analyzed cases. The best results were obtained for the z=0.9 m ( r=0.75 s) case for which α=1.0 was observed. In this case, uncertainty was about 10% in terms of relative error ( RE). Latent heat flux values were obtained by solving the energy balance equation for both the surface renewal ( LESR) and the eddy covariance ( LEEC) methods, using HSR and HEC, respectively, and measurements of net radiation and soil heat flux. For the calibration period, error analysis statistics for LESR were quite similar to those for HSR, although errors were mostly at random. LESR uncertainty was less than 9%. Calibration factors were applied for a validation data subset (30 July-4 August 2000) for which meteorological conditions were somewhat different (higher temperatures and wind speed and lower solar and net radiation). Error analysis statistics for both HSR and LESR were quite good for all cases showing the goodness of the calibration factors. Nevertheless, the results obtained for the z=0.9 m ( r=0.75 s) case were still the best ones.

An Empirical Orthogonal Function-Based Algorithm for Estimating Terrestrial Latent Heat Flux from Eddy Covariance, Meteorological and Satellite Observations.

Science.gov (United States)

Feng, Fei; Li, Xianglan; Yao, Yunjun; Liang, Shunlin; Chen, Jiquan; Zhao, Xiang; Jia, Kun; Pintér, Krisztina; McCaughey, J Harry

2016-01-01

Accurate estimation of latent heat flux (LE) based on remote sensing data is critical in characterizing terrestrial ecosystems and modeling land surface processes. Many LE products were released during the past few decades, but their quality might not meet the requirements in terms of data consistency and estimation accuracy. Merging multiple algorithms could be an effective way to improve the quality of existing LE products. In this paper, we present a data integration method based on modified empirical orthogonal function (EOF) analysis to integrate the Moderate Resolution Imaging Spectroradiometer (MODIS) LE product (MOD16) and the Priestley-Taylor LE algorithm of Jet Propulsion Laboratory (PT-JPL) estimate. Twenty-two eddy covariance (EC) sites with LE observation were chosen to evaluate our algorithm, showing that the proposed EOF fusion method was capable of integrating the two satellite data sets with improved consistency and reduced uncertainties. Further efforts were needed to evaluate and improve the proposed algorithm at larger spatial scales and time periods, and over different land cover types.

Cold Heat Storage Characteristics of O/W-type Latent Heat Emulsion Including Continuum Phase of Water Treated with a Freezing Point Depression

Science.gov (United States)

Inaba, Hideo; Morita, Shin-Ichi

This paper deals with flow and cold heat storage characteristics of the oil (tetradecane, C14H30, freezing point 278.9 K, Latent heat 229 kJ/kg)/water emulsion as a latent heat storage material having a low melting point. The test emulsion includes a water-urea solution as a continuum phase. The freezing point depression of the continuum phase permits enhancement of the heat transfer rate of the emulison, due to the large temperature difference between the latent heat storage material and water-urea solution. The velocity of emulsion flow and the inlet temperature of coolant in a coiled double tube heat exchanger are chosen as the experimental parameters. The pressure drop, the heat transfer coefficient of the emulsion in the coiled tube are measured in the temperture region over solid and liquid phase of the latent heat storage material. The finishing time of the cold heat storage is defined experimentally in the range of sensible and latent heat storage. It is clarified that the flow behavior of the emulsion as a non-Newtonian fluid has an important role in cold heat storage. The useful nondimentional correlation equations for the additional pressure loss coefficient, the heat transfer coefficient and the finishing time of the cold heat storage are derived in terms of Dean number and heat capacity ratio.

Indirectly heated biomass gasification using a latent-heat ballast-part 3: refinement of the heat transfer model

International Nuclear Information System (INIS)

Cummer, Keith; Brown, Robert C.

2005-01-01

An indirectly heated gasifier is under development at Iowa State University. This gasifier integrates a latent-heat ballast with a fluidized-bed reactor. The latent heat ballast is an array of stainless-steel tubes filled with lithium fluoride, which is a high-temperature phase-change material (PCM). Previous studies have presented experimental results from the gasifier and described a mathematical model of the pyrolysis phase of the cyclic gasification process. This model considers both heat transfer and chemical reactions that occur during pyrolysis, but discrepancies between model predictions and experimental data have demonstrated the need to refine the model. In particular, cooling curves for the ballasting system are not well predicted during phase change of the lithium fluoride. A reformulated model, known as the Receding Interface (RI) model, postulates the existence of a receding liquid phase within the ballast tubes as they cool, which progressively decreases the rate of heat transfer from the tubes. The RI model predicts behavior that is more consistent with experimental results during the phase-change process, while retaining accuracy before and after the process of phase change

Roughness Length of Water Vapor over Land Surfaces and Its Influence on Latent Heat Flux

Directory of Open Access Journals (Sweden)

Sang-Jong Park

2010-01-01

Full Text Available Latent heat flux at the surface is largely dependent on the roughness length for water vapor (z0q. The determination of z0q is still uncertain because of its multifaceted characteristics of surface properties, atmospheric conditions and insufficient observations. In this study, observed values from the Fluxes Over Snow Surface II field experiment (FLOSS-II from November 2002 to March 2003 were utilized to estimate z0q over various land surfaces: bare soil, snow, and senescent grass. The present results indicate that the estimated z0q over bare soil is much smaller than the roughness length of momentum (z0m; thus, the ratio z0m/z0q is larger than those of previous studies by a factor of 20 - 150 for the available flow regime of the roughness Reynolds number, Re* > 0.1. On the snow surface, the ratio is comparable to a previous estimation for the rough flow (Re* > 1, but smaller by a factor of 10 - 50 as the flow became smooth (Re* < 1. Using the estimated ratio, an optimal regression equation of z0m/z0q is determined as a function of Re* for each surface type. The present parameterization of the ratio is found to greatly reduce biases of latent heat flux estimation compared with that estimated by the conventional method, suggesting the usefulness of current parameterization for numerical modeling.

Cold Heat Release Characteristics of Solidified Oil Droplet-Water Solution Latent Heat Emulsion by Air Bubbles

Science.gov (United States)

Inaba, Hideo; Morita, Shin-Ichi

The present work investigates the cold heat-release characteristics of the solidified oil droplets (tetradecane, C14H30, freezing point 278.9 K)/water solution emulsion as a latent heat-storage material having a low melting point. An air bubbles-emulsion direct-contact heat exchange method is selected for the cold heat-results from the solidified oil droplet-emulsion layer. This type of direct-contact method results in the high thermal efficiency. The diameter of air bubbles in the emulsion increases as compared with that in the pure water. The air bubbles blown from a nozzle show a strong mixing behavior during rising in the emulsion. The temperature effectiveness, the sensible heat release time and the latent heat release time have been measured as experimental parameters. The useful nondimensional emulsion level equations for these parameters have been derived in terms of the nondimensional emalsion level expressed the emulsion layer dimensions, Reynolds number for air flow, Stefan number and heat capacity ratio.

Modeling and impacts of the latent heat of phase change and specific heat for phase change materials

Science.gov (United States)

Scoggin, J.; Khan, R. S.; Silva, H.; Gokirmak, A.

2018-05-01

We model the latent heats of crystallization and fusion in phase change materials with a unified latent heat of phase change, ensuring energy conservation by coupling the heat of phase change with amorphous and crystalline specific heats. We demonstrate the model with 2-D finite element simulations of Ge2Sb2Te5 and find that the heat of phase change increases local temperature up to 180 K in 300 nm × 300 nm structures during crystallization, significantly impacting grain distributions. We also show in electrothermal simulations of 45 nm confined and 10 nm mushroom cells that the higher amorphous specific heat predicted by this model increases nucleation probability at the end of reset operations. These nuclei can decrease set time, leading to variability, as demonstrated for the mushroom cell.

Ultra high temperature latent heat energy storage and thermophotovoltaic energy conversion

OpenAIRE

Datas Medina, Alejandro; Ramos Cabal, Alba; Martí Vega, Antonio; Cañizo Nadal, Carlos del; Luque López, Antonio

2016-01-01

A conceptual energy storage system design that utilizes ultra high temperature phase change materials is presented. In this system, the energy is stored in the form of latent heat and converted to electricity upon demand by TPV (thermophotovoltaic) cells. Silicon is considered in this study as PCM (phase change material) due to its extremely high latent heat (1800 J/g or 500 Wh/kg), melting point (1410 C), thermal conductivity (~25 W/mK), low cost (less than $2/kg or $4/kWh) and a...

Latent heat of traffic moving from rest

Science.gov (United States)

Farzad Ahmadi, S.; Berrier, Austin S.; Doty, William M.; Greer, Pat G.; Habibi, Mohammad; Morgan, Hunter A.; Waterman, Josam H. C.; Abaid, Nicole; Boreyko, Jonathan B.

2017-11-01

Contrary to traditional thinking and driver intuition, here we show that there is no benefit to ground vehicles increasing their packing density at stoppages. By systematically controlling the packing density of vehicles queued at a traffic light on a Smart Road, drone footage revealed that the benefit of an initial increase in displacement for close-packed vehicles is completely offset by the lag time inherent to changing back into a ‘liquid phase’ when flow resumes. This lag is analogous to the thermodynamic concept of the latent heat of fusion, as the ‘temperature’ (kinetic energy) of the vehicles cannot increase until the traffic ‘melts’ into the liquid phase. These findings suggest that in situations where gridlock is not an issue, drivers should not decrease their spacing during stoppages in order to lessen the likelihood of collisions with no loss in flow efficiency. In contrast, motion capture experiments of a line of people walking from rest showed higher flow efficiency with increased packing densities, indicating that the importance of latent heat becomes trivial for slower moving systems.

High-temperature thermocline TES combining sensible and latent heat - CFD modeling and experimental validation

Science.gov (United States)

Zavattoni, Simone A.; Geissbühler, Lukas; Barbato, Maurizio C.; Zanganeh, Giw; Haselbacher, Andreas; Steinfeld, Aldo

2017-06-01

The concept of combined sensible/latent heat thermal energy storage (TES) has been exploited to mitigate an intrinsic thermocline TES systems drawback of heat transfer fluid outflow temperature reduction during discharging. In this study, the combined sensible/latent TES prototype under investigation is constituted by a packed bed of rocks and a small amount of encapsulated phase change material (AlSi12) as sensible heat and latent heat sections respectively. The thermo-fluid dynamics behavior of the combined TES prototype was analyzed by means of a computational fluid dynamics approach. Due to the small value of the characteristic vessel-to-particles diameter ratio, the effect of radial void-fraction variation, also known as channeling, was accounted for. Both the sensible and the latent heat sections of the storage were modeled as porous media under the assumption of local thermal non-equilibrium (LTNE). The commercial code ANSYS Fluent 15.0 was used to solve the model's constitutive conservation and transport equations obtaining a fairly good agreement with reference experimental measurements.

Statistical inference based on latent ability estimates

NARCIS (Netherlands)

Hoijtink, H.J.A.; Boomsma, A.

The quality of approximations to first and second order moments (e.g., statistics like means, variances, regression coefficients) based on latent ability estimates is being discussed. The ability estimates are obtained using either the Rasch, oi the two-parameter logistic model. Straightforward use

Generalized correlation of latent heats of vaporization of coal liquid model compounds between their freezing points and critical points

Energy Technology Data Exchange (ETDEWEB)

Sivaraman, A.; Kobuyashi, R.; Mayee, J.W.

1984-02-01

Based on Pitzer's three-parameter corresponding states principle, the authors have developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds for a temperature range from the freezing point to the critical point. An expansion of the form L = L/sub 0/ + ..omega..L /sub 1/ is used for the dimensionless latent heat of vaporization. This model utilizes a nonanalytic functional form based on results derived from renormalization group theory of fluids in the vicinity of the critical point. A simple expression for the latent heat of vaporization L = D/sub 1/epsilon /SUP 0.3333/ + D/sub 2/epsilon /SUP 0.8333/ + D/sub 4/epsilon /SUP 1.2083/ + E/sub 1/epsilon + E/sub 2/epsilon/sup 2/ + E/sub 3/epsilon/sup 3/ is cast in a corresponding states principle correlation for coal liquid compounds. Benzene, the basic constituent of the functional groups of the multi-ring coal liquid compounds, is used as the reference compound in the present correlation. This model works very well at both low and high reduced temperatures approaching the critical point (0.02 < epsilon = (T /SUB c/ - T)/(T /SUB c/- 0.69)). About 16 compounds, including single, two, and three-ring compounds, have been tested and the percent root-mean-square deviations in latent heat of vaporization reported and estimated through the model are 0.42 to 5.27%. Tables of the coefficients of L/sub 0/ and L/sub 1/ are presented. The contributing terms of the latent heat of vaporization function are also presented in a table for small increments of epsilon.

Accuracy of latent-variable estimation in Bayesian semi-supervised learning.

Science.gov (United States)

Yamazaki, Keisuke

2015-09-01

Hierarchical probabilistic models, such as Gaussian mixture models, are widely used for unsupervised learning tasks. These models consist of observable and latent variables, which represent the observable data and the underlying data-generation process, respectively. Unsupervised learning tasks, such as cluster analysis, are regarded as estimations of latent variables based on the observable ones. The estimation of latent variables in semi-supervised learning, where some labels are observed, will be more precise than that in unsupervised, and one of the concerns is to clarify the effect of the labeled data. However, there has not been sufficient theoretical analysis of the accuracy of the estimation of latent variables. In a previous study, a distribution-based error function was formulated, and its asymptotic form was calculated for unsupervised learning with generative models. It has been shown that, for the estimation of latent variables, the Bayes method is more accurate than the maximum-likelihood method. The present paper reveals the asymptotic forms of the error function in Bayesian semi-supervised learning for both discriminative and generative models. The results show that the generative model, which uses all of the given data, performs better when the model is well specified. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modeling the Daly Gap: The Influence of Latent Heat Production in Controlling Magma Extraction and Eruption

Science.gov (United States)

Nelson, B. K.; Ghiorso, M. S.; Bachmann, O.; Dufek, J.

2011-12-01

model, we move the extracted liquid to a shallower chamber (1.5 kbar as inferred for Tenerife phonolite) and resume crystallization. At the optimal magma extraction window of ≈50% crystallinity, the composition matches well with the observed composition of the second peak of the bimodal distribution. In contrast, CI does not show an early spike in latent heat production, but a late (≈900°C) pseudo-invariant point where latent heat production spikes. This spike is very near the 50% crystallinity window, again enhancing the probability of magma extraction. The model liquid composition at this crystallinity matches the observed trachyte composition. In both systems, phase chemistry supports a two-chamber evolution, one deep and the second shallow, corresponding to two primary melt extraction events. Realistically incorporating chemical, thermal and physical processes in magma chamber models provides composition-volume estimates of extracted magma that coincide with observed bimodal composition-volume relations. The strong variability in latent heat production is an important control, and its characterization is central to physical models of magma chamber evolution.

Anthropogenic Heat Flux Estimation from Space: Results of the second phase of the URBANFLUXES Project

Science.gov (United States)

Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean-Philippe; Grimmond, Sue; Feigenwinter, Christian; Lindberg, Fredrik; Del Frate, Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

2017-04-01

The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. The Discrete Anisotropic Radiative Transfer (DART) model is employed to improve the estimation of the net all-wave radiation balance, whereas the Element Surface Temperature Method (ESTM), adjusted to satellite observations is used to improve the estimation the estimation of the net change in heat storage. Furthermore the estimation of the turbulent sensible and latent heat fluxes is based on the Aerodynamic Resistance Method (ARM). Based on these outcomes, QF is estimated by regressing the sum of the turbulent heat fluxes versus the available energy. In-situ flux measurements are used to evaluate URBANFLUXES outcomes, whereas uncertainties are specified and analyzed. URBANFLUXES is expected to prepare the ground for further innovative exploitation of EO in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation. This study presents the results of the second phase of the project and detailed information on URBANFLUXES is available at: http://urbanfluxes.eu

Latent heat transport and microlayer evaporation in nucleate boiling

International Nuclear Information System (INIS)

Jawurek, H.H.

1977-08-01

Part 1 of this work provides a broad overview and, where possible, a quantitative assessment of the complex physical processes which together constitute the mechanism of nucleate boiling heat transfer. It is shown that under a wide range of conditions the primary surface-to-liquid heat flows within an area of bubble influence are so redistributed as to manifest themselves predominantly as latent heat transport, that is, as vaporisation into attached bubbles. Part 2 deals in greater detail with one of the component processes of latent heat transport, namely microlayer evaporation. A literature review reveals the need for synchronised records of microlayer geometry versus time and of normal bubble growth and departure. An apparatus developed to provide such records is described. High-speed cine interference photography from beneath and through a transparent heating surface provided details of microlayer geometry and an image reflection system synchronised these records with the bubble profile views. Results are given for methanol and ethanol boiling at sub-atmospheric pressures and at various heat fluxes and bulk subcoolings. In all cases it is found that microlayers were of sub-micron thickness, that microlayer thinning was restricted to the inner layer edge (with the thickness elsewhere remaining constant or increasing with time) and that the contribution of this visible evaporation to the total vapour flow into bubbles was negligible. The observation of thickening towards the outer microlayer edge, however, demonstrates that a liquid replenishment flow occurred simultaneously with the evaporation process

A Latent Class Approach to Estimating Test-Score Reliability

Science.gov (United States)

van der Ark, L. Andries; van der Palm, Daniel W.; Sijtsma, Klaas

2011-01-01

This study presents a general framework for single-administration reliability methods, such as Cronbach's alpha, Guttman's lambda-2, and method MS. This general framework was used to derive a new approach to estimating test-score reliability by means of the unrestricted latent class model. This new approach is the latent class reliability…

A model for the latent heat of melting in free standing metal nanoparticles

International Nuclear Information System (INIS)

Shin, Jeong-Heon; Deinert, Mark R.

2014-01-01

Nanoparticles of many metals are known to exhibit scale dependent latent heats of melting. Analytical models for this phenomenon have so far failed to completely capture the observed phenomena. Here we present a thermodynamic analysis for the melting of metal nanoparticles in terms of their internal energy and a scale dependent surface tension proposed by Tolman. The resulting model predicts the scale dependence of the latent heat of melting and is confirmed using published data for tin and aluminum

A One-Source Approach for Estimating Land Surface Heat Fluxes Using Remotely Sensed Land Surface Temperature

Directory of Open Access Journals (Sweden)

Yongmin Yang

2017-01-01

Full Text Available The partitioning of available energy between sensible heat and latent heat is important for precise water resources planning and management in the context of global climate change. Land surface temperature (LST is a key variable in energy balance process and remotely sensed LST is widely used for estimating surface heat fluxes at regional scale. However, the inequality between LST and aerodynamic surface temperature (Taero poses a great challenge for regional heat fluxes estimation in one-source energy balance models. To address this issue, we proposed a One-Source Model for Land (OSML to estimate regional surface heat fluxes without requirements for empirical extra resistance, roughness parameterization and wind velocity. The proposed OSML employs both conceptual VFC/LST trapezoid model and the electrical analog formula of sensible heat flux (H to analytically estimate the radiometric-convective resistance (rae via a quartic equation. To evaluate the performance of OSML, the model was applied to the Soil Moisture-Atmosphere Coupling Experiment (SMACEX in United States and the Multi-Scale Observation Experiment on Evapotranspiration (MUSOEXE in China, using remotely sensed retrievals as auxiliary data sets at regional scale. Validated against tower-based surface fluxes observations, the root mean square deviation (RMSD of H and latent heat flux (LE from OSML are 34.5 W/m2 and 46.5 W/m2 at SMACEX site and 50.1 W/m2 and 67.0 W/m2 at MUSOEXE site. The performance of OSML is very comparable to other published studies. In addition, the proposed OSML model demonstrates similar skills of predicting surface heat fluxes in comparison to SEBS (Surface Energy Balance System. Since OSML does not require specification of aerodynamic surface characteristics, roughness parameterization and meteorological conditions with high spatial variation such as wind speed, this proposed method shows high potential for routinely acquisition of latent heat flux estimation

Estimating Non-Normal Latent Trait Distributions within Item Response Theory Using True and Estimated Item Parameters

Science.gov (United States)

Sass, D. A.; Schmitt, T. A.; Walker, C. M.

2008-01-01

Item response theory (IRT) procedures have been used extensively to study normal latent trait distributions and have been shown to perform well; however, less is known concerning the performance of IRT with non-normal latent trait distributions. This study investigated the degree of latent trait estimation error under normal and non-normal…

Standard Errors of Estimated Latent Variable Scores with Estimated Structural Parameters

Science.gov (United States)

Hoshino, Takahiro; Shigemasu, Kazuo

2008-01-01

The authors propose a concise formula to evaluate the standard error of the estimated latent variable score when the true values of the structural parameters are not known and must be estimated. The formula can be applied to factor scores in factor analysis or ability parameters in item response theory, without bootstrap or Markov chain Monte…

Flat plate solar air heater with latent heat storage

Science.gov (United States)

Touati, B.; Kerroumi, N.; Virgone, J.

2017-02-01

Our work contains two parts, first is an experimental study of the solar air heater with a simple flow and forced convection, we can use thatlaste oneit in many engineering's sectors as solardrying, space heating in particular. The second part is a numerical study with ansys fluent 15 of the storage of part of this solar thermal energy produced,using latent heat by using phase change materials (PCM). In the experimental parts, we realize and tested our solar air heater in URER.MS ADRAR, locate in southwest Algeria. Where we measured the solarradiation, ambient temperature, air flow, thetemperature of the absorber, glasses and the outlet temperature of the solar air heater from the Sunrise to the sunset. In the second part, we added a PCM at outlet part of the solar air heater. This PCM store a part of the energy produced in the day to be used in peak period at evening by using the latent heat where the PCMs present a grateful storagesystem.A numerical study of the fusion or also named the charging of the PCM using ANSYS Fluent 15, this code use the method of enthalpies to solve the fusion and solidification formulations. Furthermore, to improve the conjugate heat transfer between the heat transfer fluid (Air heated in solar plate air heater) and the PCM, we simulate the effect of adding fins to our geometry. Also, four user define are write in C code to describe the thermophysicalpropriety of the PCM, and the inlet temperature of our geometry which is the temperature at the outflow of the solar heater.

Development of graphite foam infiltrated with MgCl 2 for a latent heat based thermal energy storage (LHTES) system

Energy Technology Data Exchange (ETDEWEB)

Singh, Dileep; Kim, Taeil; Zhao, Weihuan; Yu, Wenhua; France, David M.

2016-08-01

Thermal energy storage (TES) systems that are compatible with high temperature power cycles for concentrating solar power (CSP) require high temperature media for transporting and storing thermal energy. To that end, TES systems have been proposed based on the latent heat of fusion of the phase change materials (PCMs). However, PCMs have relatively low thermal conductivities. In this paper, use of high-thermal-conductivity graphite foam infiltrated with a PCM (MgCl2) has been investigated as a potential TES system. Graphite foams with two porosities were infiltrated with MgCl2. The infiltrated composites were evaluated for density, heat of fusion, melting/freezing temperatures, and thermal diffusivities. Estimated thermal conductivities of MgCl2/graphite foam composites were significantly higher than those of MgCl2 alone over the measured temperature range. Furthermore, heat of fusion, melting/freezing temperatures, and densities showed comparable values to those of pure MgCl2. Results of this study indicate that MgCl2/graphite foam composites show promise as storage media for a latent heat thermal energy storage system for CSP applications.

Performance investigation of a lab–scale latent heat storage prototype – Numerical results

International Nuclear Information System (INIS)

Niyas, Hakeem; Prasad, Sunku; Muthukumar, P.

2017-01-01

Highlights: • Developed a numerical tool for analyzing a shell-and-tube LHS system. • Effective heat capacity method is used for incorporating the latent heat. • Number of heat transfer fluid tubes and fins are optimized. • Partial charging/discharging is efficient than complete charging/discharging. • Numerically predicted values match well with the experimental results. - Abstract: In the current study, numerical analysis of the charging and discharging characteristics of a lab-scale latent heat storage (LHS) prototype is presented. A mathematical model is developed to analyze the performance characteristics of the LHS prototype of shell and tube heat exchanger configuration. Effective heat capacity (EHC) method is implemented to consider the latent heat of the phase change material (PCM) and Boussinesq approximation is used to incorporate the buoyancy effect of the molten layer of the PCM in the model. For proper modeling of velocities in the PCM, Darcy law’s source term is added. The governing equations involved in the model are solved using a finite element based software product, COMSOL Multiphysics 4.3a. The number of embedded tubes and fins on the embedded tubes are optimized based on the discharging time of the model. Various performance parameters such as charging/discharging time, energy storage/discharge rate and melt fraction are evaluated. Numerically predicted temperature variations of the model during charging and discharging processes were compared with the experimental data extracted from the lab-scale LHS prototype and a good agreement was found between them.

Surface latent heat flux as an earthquake precursor

Directory of Open Access Journals (Sweden)

S. Dey

2003-01-01

Full Text Available The analysis of surface latent heat flux (SLHF from the epicentral regions of five recent earthquakes that occurred in close proximity to the oceans has been found to show anomalous behavior. The maximum increase of SLHF is found 2–7 days prior to the main earthquake event. This increase is likely due to an ocean-land-atmosphere interaction. The increase of SLHF prior to the main earthquake event is attributed to the increase in infrared thermal (IR temperature in the epicentral and surrounding region. The anomalous increase in SLHF shows great potential in providing early warning of a disastrous earthquake, provided that there is a better understanding of the background noise due to the tides and monsoon in surface latent heat flux. Efforts have been made to understand the level of background noise in the epicentral regions of the five earthquakes considered in the present paper. A comparison of SLHF from the epicentral regions over the coastal earthquakes and the earthquakes that occurred far away from the coast has been made and it has been found that the anomalous behavior of SLHF prior to the main earthquake event is only associated with the coastal earthquakes.

Residual Entropy, the Third Law and Latent Heat

Directory of Open Access Journals (Sweden)

Frank L. Lambert

2008-09-01

Full Text Available A novel thermodynamic treatment of residual entropy in crystals, involving the configurational partition function, is suggested, which is consistent with both classical and statistical thermodynamics. It relates residual entropy to the inherent latent heat which would be released upon cooling if the reversible path were available. The nature of this heat is that if the crystal possessing residual entropy freezes above its Boltzmann’s characteristic temperature of molecular alignment, the difference in energy between different molecular arrangements is overcome by the kT heat bath to form a nearly-ideal solution. However, upon cooling below this characteristic temperature, they would separate with a concomitant release of the corresponding energy, provided the reversible path were available.

On the Equality Assumption of Latent and Sensible Heat Energy Transfer Coefficients of the Bowen Ratio Theory for Evapotranspiration Estimations: Another Look at the Potential Causes of Inequalities

Directory of Open Access Journals (Sweden)

Suat Irmak

2014-08-01

Full Text Available Evapotranspiration (ET and sensible heat (H flux play a critical role in climate change; micrometeorology; atmospheric investigations; and related studies. They are two of the driving variables in climate impact(s and hydrologic balance dynamics. Therefore, their accurate estimate is important for more robust modeling of the aforementioned relationships. The Bowen ratio energy balance method of estimating ET and H diffusions depends on the assumption that the diffusivities of latent heat (KV and sensible heat (KH are always equal. This assumption is re-visited and analyzed for a subsurface drip-irrigated field in south central Nebraska. The inequality dynamics for subsurface drip-irrigated conditions have not been studied. Potential causes that lead KV to differ from KH and a rectification procedure for the errors introduced by the inequalities were investigated. Actual ET; H; and other surface energy flux parameters using an eddy covariance system and a Bowen Ratio Energy Balance System (located side by side on an hourly basis were measured continuously for two consecutive years for a non-stressed and subsurface drip-irrigated maize canopy. Most of the differences between KV and KH appeared towards the higher values of KV and KH. Although it was observed that KV was predominantly higher than KH; there were considerable data points showing the opposite. In general; daily KV ranges from about 0.1 m2∙s−1 to 1.6 m2∙s−1; and KH ranges from about 0.05 m2∙s−1 to 1.1 m2∙s−1. The higher values for KV and KH appear around March and April; and around September and October. The lower values appear around mid to late December and around late June to early July. Hourly estimates of KV range between approximately 0 m2∙s−1 to 1.8 m2∙s−1 and that of KH ranges approximately between 0 m2∙s−1 to 1.7 m2∙s−1. The inequalities between KV and KH varied diurnally as well as seasonally. The inequalities were greater during the non

Explicit estimating equations for semiparametric generalized linear latent variable models

KAUST Repository

Ma, Yanyuan

2010-07-05

We study generalized linear latent variable models without requiring a distributional assumption of the latent variables. Using a geometric approach, we derive consistent semiparametric estimators. We demonstrate that these models have a property which is similar to that of a sufficient complete statistic, which enables us to simplify the estimating procedure and explicitly to formulate the semiparametric estimating equations. We further show that the explicit estimators have the usual root n consistency and asymptotic normality. We explain the computational implementation of our method and illustrate the numerical performance of the estimators in finite sample situations via extensive simulation studies. The advantage of our estimators over the existing likelihood approach is also shown via numerical comparison. We employ the method to analyse a real data example from economics. © 2010 Royal Statistical Society.

Thermophysical Properties of Fluid Latent Heat Storage Material using Urea-Water Mixture

Science.gov (United States)

Hokamura, Taku; Ohkubo, Hidetoshi; Ashizawa, Kiyonori

This study is concerned with the measurement of thermophysical properties of a urea-water mixture with the aim of adopting the mixture as a latent heat storage material for air-conditioning systems. The urea-water mixture is made of natural substances and has a good fluidity. The urea concentration in the mixture was controlled by measuring the refractive index of the mixture. Being a multi-component substance, a urea-water solution has a liquid-solid co-existent phase on a phase-diagram. Therefore, the liquidus temperature was measured to establish a relationship between the fraction of the solid-phase and temperature. Furthermore, apparent values of specific heat and coefficient of viscosity were measured in the two-phase region where the solid phase is ice. The apparent specific heat and coefficient of viscosity were measure by using an adiabatic calorimeter and a stirring torque meter respectively. The results revealed that the urea-water mixture can probably be used as a latent heat storage material of good fluidity.

Estimators for longitudinal latent exposure models: examining measurement model assumptions.

Science.gov (United States)

Sánchez, Brisa N; Kim, Sehee; Sammel, Mary D

2017-06-15

Latent variable (LV) models are increasingly being used in environmental epidemiology as a way to summarize multiple environmental exposures and thus minimize statistical concerns that arise in multiple regression. LV models may be especially useful when multivariate exposures are collected repeatedly over time. LV models can accommodate a variety of assumptions but, at the same time, present the user with many choices for model specification particularly in the case of exposure data collected repeatedly over time. For instance, the user could assume conditional independence of observed exposure biomarkers given the latent exposure and, in the case of longitudinal latent exposure variables, time invariance of the measurement model. Choosing which assumptions to relax is not always straightforward. We were motivated by a study of prenatal lead exposure and mental development, where assumptions of the measurement model for the time-changing longitudinal exposure have appreciable impact on (maximum-likelihood) inferences about the health effects of lead exposure. Although we were not particularly interested in characterizing the change of the LV itself, imposing a longitudinal LV structure on the repeated multivariate exposure measures could result in high efficiency gains for the exposure-disease association. We examine the biases of maximum likelihood estimators when assumptions about the measurement model for the longitudinal latent exposure variable are violated. We adapt existing instrumental variable estimators to the case of longitudinal exposures and propose them as an alternative to estimate the health effects of a time-changing latent predictor. We show that instrumental variable estimators remain unbiased for a wide range of data generating models and have advantages in terms of mean squared error. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Heat Transfer and Latent Heat Storage in Inorganic Molten Salts for Concentrating Solar Power Plants

Energy Technology Data Exchange (ETDEWEB)

Mathur, Anoop [Terrafore Inc.

2013-08-14

A key technological issue facing the success of future Concentrating Solar Thermal Power (CSP) plants is creating an economical Thermal Energy Storage (TES) system. Current TES systems use either sensible heat in fluids such as oil, or molten salts, or use thermal stratification in a dual-media consisting of a solid and a heat-transfer fluid. However, utilizing the heat of fusion in inorganic molten salt mixtures in addition to sensible heat , as in a Phase change material (PCM)-based TES, can significantly increase the energy density of storage requiring less salt and smaller containers. A major issue that is preventing the commercial use of PCM-based TES is that it is difficult to discharge the latent heat stored in the PCM melt. This is because when heat is extracted, the melt solidifies onto the heat exchanger surface decreasing the heat transfer. Even a few millimeters of thickness of solid material on heat transfer surface results in a large drop in heat transfer due to the low thermal conductivity of solid PCM. Thus, to maintain the desired heat rate, the heat exchange area must be large which increases cost. This project demonstrated that the heat transfer coefficient can be increase ten-fold by using forced convection by pumping a hyper-eutectic salt mixture over specially coated heat exchanger tubes. However,only 15% of the latent heat is used against a goal of 40% resulting in a projected cost savings of only 17% against a goal of 30%. Based on the failure mode effect analysis and experience with pumping salt at near freezing point significant care must be used during operation which can increase the operating costs. Therefore, we conclude the savings are marginal to justify using this concept for PCM-TES over a two-tank TES. The report documents the specialty coatings, the composition and morphology of hypereutectic salt mixtures and the results from the experiment conducted with the active heat exchanger along with the lessons learnt during

Regional CO2 and latent heat surface fluxes in the Southern Great Plains: Measurements, modeling, and scaling

Energy Technology Data Exchange (ETDEWEB)

Riley, W. J.; Biraud, S.C.; Torn, M.S.; Fischer, M.L.; Billesbach, D.P.; Berry, J.A.

2009-08-15

Characterizing net ecosystem exchanges (NEE) of CO{sub 2} and sensible and latent heat fluxes in heterogeneous landscapes is difficult, yet critical given expected changes in climate and land use. We report here a measurement and modeling study designed to improve our understanding of surface to atmosphere gas exchanges under very heterogeneous land cover in the mostly agricultural U.S. Southern Great Plains (SGP). We combined three years of site-level, eddy covariance measurements in several of the dominant land cover types with regional-scale climate data from the distributed Mesonet stations and Next Generation Weather Radar precipitation measurements to calibrate a land surface model of trace gas and energy exchanges (isotope-enabled land surface model (ISOLSM)). Yearly variations in vegetation cover distributions were estimated from Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index and compared to regional and subregional vegetation cover type estimates from the U.S. Department of Agriculture census. We first applied ISOLSM at a 250 m spatial scale to account for vegetation cover type and leaf area variations that occur on hundred meter scales. Because of computational constraints, we developed a subsampling scheme within 10 km 'macrocells' to perform these high-resolution simulations. We estimate that the Atmospheric Radiation Measurement Climate Research Facility SGP region net CO{sub 2} exchange with the local atmosphere was -240, -340, and -270 gC m{sup -2} yr{sup -1} (positive toward the atmosphere) in 2003, 2004, and 2005, respectively, with large seasonal variations. We also performed simulations using two scaling approaches at resolutions of 10, 30, 60, and 90 km. The scaling approach applied in current land surface models led to regional NEE biases of up to 50 and 20% in weekly and annual estimates, respectively. An important factor in causing these biases was the complex leaf area index (LAI) distribution

Convective and Stratiform Precipitation Processes and their Relationship to Latent Heating

Science.gov (United States)

Tao, Wei-Kuo; Lang, Steve; Zeng, Xiping; Shige, Shoichi; Takayabu, Yukari

2009-01-01

The global hydrological cycle is central to the Earth's climate system, with rainfall and the physics of its formation acting as the key links in the cycle. Two-thirds of global rainfall occurs in the Tropics. Associated with this rainfall is a vast amount of heat, which is known as latent heat. It arises mainly due to the phase change of water vapor condensing into liquid droplets; three-fourths of the total heat energy available to the Earth's atmosphere comes from tropical rainfall. In addition, fresh water provided by tropical rainfall and its variability exerts a large impact upon the structure and motions of the upper ocean layer. An improved convective -stratiform heating (CSH) algorithm has been developed to obtain the 3D structure of cloud heating over the Tropics based on two sources of information: 1) rainfall information, namely its amount and the fraction due to light rain intensity, observed directly from the Precipitation Radar (PR) on board the TRMM satellite and 2) synthetic cloud physics information obtained from cloud-resolving model (CRM) simulations of cloud systems. The cloud simulations provide details on cloud processes, specifically latent heating, eddy heat flux convergence and radiative heating/cooling, that. are not directly observable by satellite. The new CSH algorithm-derived heating has a noticeably different heating structure over both ocean and land regions compared to the previous CSH algorithm. One of the major differences between new and old algorithms is that the level of maximum cloud heating occurs 1 to 1.5 km lower in the atmosphere in the new algorithm. This can effect the structure of the implied air currents associated with the general circulation of the atmosphere in the Tropics. The new CSH algorithm will be used provide retrieved heating data to other heating algorithms to supplement their performance.

Experimental Investigation of A Heat Pipe-Assisted Latent Heat Thermal Energy Storage System

Science.gov (United States)

Tiari, Saeed; Mahdavi, Mahboobe; Qiu, Songgang

2016-11-01

In the present work, different operation modes of a latent heat thermal energy storage system assisted by a heat pipe network were studied experimentally. Rubitherm RT55 enclosed by a vertical cylindrical container was used as the Phase Change Material (PCM). The embedded heat pipe network consisting of a primary heat pipe and an array of four secondary heat pipes were employed to transfer heat to the PCM. The primary heat pipe transports heat from the heat source to the heat sink. The secondary heat pipes transfer the extra heat from the heat source to PCM during charging process or retrieve thermal energy from PCM during discharging process. The effects of heat transfer fluid (HTF) flow rate and temperature on the thermal performance of the system were investigated for both charging and discharging processes. It was found that the HTF flow rate has a significant effect on the total charging time of the system. Increasing the HTF flow rate results in a remarkable increase in the system input thermal power. The results also showed that the discharging process is hardly affected by the HTF flow rate but HTF temperature plays an important role in both charging and discharging processes. The authors would like to acknowledge the financial supports by Temple University for the project.

Active latent heat storage with a screw heat exchanger - experimental results for heat transfer and concept for high pressure steam

Science.gov (United States)

Zipf, Verena; Willert, Daniel; Neuhäuser, Anton

2016-05-01

An innovative active latent heat storage concept was invented and developed at Fraunhofer ISE. It uses a screw heat exchanger (SHE) for the phase change during the transport of a phase change material (PCM) from a cold to a hot tank or vice versa. This separates heat transfer and storage tank in comparison to existing concepts. A test rig has been built in order to investigate the heat transfer coefficients of the SHE during melting and crystallization of the PCM. The knowledge of these characteristics is crucial in order to assess the performance of the latent heat storage in a thermal system. The test rig contains a double shafted SHE, which is heated or cooled with thermal oil. The overall heat transfer coefficient U and the convective heat transfer coefficient on the PCM side hPCM both for charging and discharging have been calculated based on the measured data. For charging, the overall heat transfer coefficient in the tested SHE was Uch = 308 W/m2K and for discharging Udis = 210 W/m2K. Based on the values for hPCM the overall heat transfer coefficients for a larger SHE with steam as heat transfer fluid and an optimized geometry were calculated with Uch = 320 W/m2K for charging and Udis = 243 W/m2K for discharging. For pressures as high as p = 100 bar, an SHE concept has been developed, which uses an organic fluid inside the flight of the SHE as working media. With this concept, the SHE can also be deployed for very high pressure, e.g. as storage in solar thermal power plants.

Solar thermoelectricity via advanced latent heat storage

Science.gov (United States)

Olsen, M. L.; Rea, J.; Glatzmaier, G. C.; Hardin, C.; Oshman, C.; Vaughn, J.; Roark, T.; Raade, J. W.; Bradshaw, R. W.; Sharp, J.; Avery, A. D.; Bobela, D.; Bonner, R.; Weigand, R.; Campo, D.; Parilla, P. A.; Siegel, N. P.; Toberer, E. S.; Ginley, D. S.

2016-05-01

We report on a new modular, dispatchable, and cost-effective solar electricity-generating technology. Solar ThermoElectricity via Advanced Latent heat Storage (STEALS) integrates several state-of-the-art technologies to provide electricity on demand. In the envisioned STEALS system, concentrated sunlight is converted to heat at a solar absorber. The heat is then delivered to either a thermoelectric (TE) module for direct electricity generation, or to charge a phase change material for thermal energy storage, enabling subsequent generation during off-sun hours, or both for simultaneous electricity production and energy storage. The key to making STEALS a dispatchable technology lies in the development of a "thermal valve," which controls when heat is allowed to flow through the TE module, thus controlling when electricity is generated. The current project addresses each of the three major subcomponents, (i) the TE module, (ii) the thermal energy storage system, and (iii) the thermal valve. The project also includes system-level and techno- economic modeling of the envisioned integrated system and will culminate in the demonstration of a laboratory-scale STEALS prototype capable of generating 3kWe.

HYBRID INDIRECT SOLAR COOKER WITH LATENT HEAT STORAGE

OpenAIRE

Benazeer Hassan K. Ibrahim *, Victor Jose

2016-01-01

Solar cooking is the simplest, safest, most convenient way to cook food without consuming fuels or heating up the kitchen. All the conventional solar cooker designs have the disadvantage of inability to cook during off-shine and night hours.This disadvantage can be eliminated if the solar cooker is designed with thermal storage arrangement. In this paper, a hybrid solar cooker with evacuated tube collector and latent thermal storage unit and alternate electric heatingsource is simulated. The...

Thermal properties and thermal reliability of eutectic mixtures of some fatty acids as latent heat storage materials

International Nuclear Information System (INIS)

Sari, Ahmet; Sari, Hayati; Oenal, Adem

2004-01-01

The present study deals with two subjects. The first one is to determine the thermal properties of lauric acid (LA)-stearic acid (SA), myristic acid (MA)-palmitic acid (PA) and palmitic acid (PA)-stearic acid (SA) eutectic mixtures as latent heat storage material. The properties were measured by the differential scanning calorimetry (DSC) analysis technique. The second one is to study the thermal reliability of these materials in view of the change in their melting temperatures and latent heats of fusion with respect to repeated thermal cycles. For this aim, the eutectic mixtures were subjected to 360 repeated melt/freeze cycles, and their thermal properties were measured after 0, 90,180 and 360 thermal cycles by the technique of DSC analysis. The DSC thermal analysis results show that the binary systems of LA-SA in the ratio of 75.5:24.5 wt.%, MA-PA in the ratio of 58:42 wt.% and PA-SA in the ratio of 64.2:35.8 wt.% form eutectic mixtures with melting temperatures of 37.0, 42.60 and 52.30 deg. C and with latent heats of fusion of 182.7, 169.7 and 181.7 J g -1 , respectively. These thermal properties make them possible for heat storage in passive solar heating applications with respect to climate conditions. The accelerated thermal cycle tests indicate that the changes in the melting temperatures and latent heats of fusion of the studied eutectic mixtures are not regular with increasing number of thermal cycles. However, these materials, latent heat energy storage materials, have good thermal reliability in terms of the change in their thermal properties with respect to thermal cycling for about a one year utility period

Efficiency gains of photovoltaic system using latent heat thermal energy storage

NARCIS (Netherlands)

Tan, Lippong; Date, Abhijit; Fernandes, Gabriel; Singh, Baljit; Ganguly, Sayantan

This paper presents experimental assessments of the thermal and electrical performance of photovoltaic (PV) system by comparing the latent heat-cooled PV panel with the naturally-cooled equivalent. It is commonly known that the energy conversion efficiency of the PV cells declines with the increment

Verification of High Resolution Soil Moisture and Latent Heat in Germany

Science.gov (United States)

Samaniego, L. E.; Warrach-Sagi, K.; Zink, M.; Wulfmeyer, V.

2012-12-01

Improving our understanding of soil-land-surface-atmosphere feedbacks is fundamental to make reliable predictions of water and energy fluxes on land systems influenced by anthropogenic activities. Estimating, for instance, which would be the likely consequences of changing climatic regimes on water availability and crop yield, requires of high resolution soil moisture. Modeling it at large-scales, however, is difficult and uncertain because of the interplay between state variables and fluxes and the significant parameter uncertainty of the predicting models. At larger scales, the sub-grid variability of the variables involved and the nonlinearity of the processes complicate the modeling exercise even further because parametrization schemes might be scale dependent. Two contrasting modeling paradigms (WRF/Noah-MP and mHM) were employed to quantify the effects of model and data complexity on soil moisture and latent heat over Germany. WRF/Noah-MP was forced ERA-interim on the boundaries of the rotated CORDEX-Grid (www.meteo.unican.es/wiki/cordexwrf) with a spatial resolution of 0.11o covering Europe during the period from 1989 to 2009. Land cover and soil texture were represented in WRF/Noah-MP with 1×1~km MODIS images and a single horizon, coarse resolution European-wide soil map with 16 soil texture classes, respectively. To ease comparison, the process-based hydrological model mHM was forced with daily precipitation and temperature fields generated by WRF during the same period. The spatial resolution of mHM was fixed at 4×4~km. The multiscale parameter regionalization technique (MPR, Samaniego et al. 2010) was embedded in mHM to be able to estimate effective model parameters using hyper-resolution input data (100×100~km) obtained from Corine land cover and detailed soil texture fields for various horizons comprising 72 soil texture classes for Germany, among other physiographical variables. mHM global parameters, in contrast with those of Noah-MP, were

Latent Heat Flow in Light Weight Roofs and its Influence on the Thermal Performance

DEFF Research Database (Denmark)

Rode, Carsten; Rudbeck, Claus Christian

1998-01-01

Under certain conditions, migration of small amounts of moisture in the envelope of buildings can cause heat flow through permeable thermal insulation materials due to the conversion of latent heat when moisture evaporates from a warm surface, diffuses through the insulation, and condenses...

Experimental investigation for the optimization of heat pipe performance in latent heat thermal storage

Energy Technology Data Exchange (ETDEWEB)

Ladekar, Chandrakishor; Choudhary, S. K. [RTM Nagpur University, Wardha (India); Khandare, S. S. [B. D. College of Engineering, Wardha (India)

2017-06-15

We investigated the optimum performance of heat pipe in Latent heat thermal energy storage (LHTES), and compared it with copper pipe. Classical plan of experimentation was used to optimize the parameters of heat pipe. Heat pipe fill ratio, evaporator section length to condenser section length ratio i.e., Heat pipe length ratio (HPLR) and heat pipe diameter, was the parameter used for optimization, as result of parametric analysis. Experiment with flow rate of 10 lit./min. was conducted for different fill ratio, HPLR and different diameter. Fill ratio of 80 %, HPLR of 0.9 and heat pipe with diameter of 18 mm showed better trend in charging and discharging. Comparison between the storage tank with optimized heat pipe and copper pipe showed almost 186 % improvement in charging and discharging time compared with the copper pipe embedded thermal storage. Heat transfer between Heat transferring fluid (HTF) and Phase change material (PCM) increased with increase in area of heat transferring media, but storage density of storage tank decreased. Storage tank with heat pipe embedded in place of copper pipe is a better option in terms of charging and discharging time as well heat storage capacity due to less heat lost. This justifies the better efficiency and effectiveness of storage tank with embedded optimized heat pipe.

Evaporative cooling: Effective latent heat of evaporation in relation to evaporation distance from the skin

NARCIS (Netherlands)

Havenith, G.; Bröde, P.; Hartog, E.A. den; Kuklane, K.; Holmer, I.; Rossi, R.M.; Richards, M.; Farnworth, B.; Wang, X.

2013-01-01

Calculation of evaporative heat loss is essential to heat balance calculations. Despite recognition that the value for latent heat of evaporation, used in these calculations, may not always reflect the real cooling benefit to the body, only limited quantitative data on this is available, which has

Preparation and flow characteristic of a novel phase change fluid for latent heat transfer

Energy Technology Data Exchange (ETDEWEB)

Zou, Deqiu [Marine College of Ningbo University, Ningbo 315211, Zhejiang (China); Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); Feng, Ziping; Xiao, Rui; Qin, Kun; Zhang, Jianjun; Song, Wenji; Tu, Qiu [Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China)

2010-12-15

A novel phase change emulsion (PCE) was prepared and its latent heat was measured by DSC. To analyze its feasibility in heat transportation through a piping system, an experimental system was built. The pressure drop of the PCE for turbulent flow was measured and the effects of such facts as the paraffin concentration and flow velocity were discussed. According to the pressure characteristic and latent heat of the PCE, the pumping power consumption rates of PCE to water under the same pipe diameter and a given heat transportation quantity can be obtained. The results show that mass flow rate and pumping power consumption of the PCE decrease greatly compared with water. For example, the decrease can be up to about 73% at V=0.6 m/s (20 and 30 wt%). Furthermore, the results show that PCE of 20 wt% can obtain almost the same pumping power consumption savings as PCE of 30 wt% in a certain flow velocity range. Finally, the applications of the PCE in the area of waste heat usage, electrical boiler and solar energy usage were commented. (author)

Radiation budget, soil heat flux and latent heat flux at the forest floor in warm, temperate mixed forest

International Nuclear Information System (INIS)

Tamai, K.; Abe, T.; Araki, M.; Ito, H.

1998-01-01

Seasonal changes in the radiation budget and soil heat flux of a forest floor were measured in a mixed forest located in Kyoto, Japan. The basal area at breast height in the survey forest was about 15·82 m 2 ha −1 , for evergreen trees, and 12·46 m 2 ha −1 , for deciduous trees. The sky view factor was 16 and 22% at the survey site in the foliate and defoliate seasons, respectively. The small difference between the sky view factor in the two seasons was reflected in the seasonal change in the radiation budget of the forest floor. Namely, the net long-wave radiation changed rapidly in leafing and falling days, and the rate of net short-wave radiation was highest in April. The distinctive characteristic of the radiation budget was that the rates of available radiation in the daytime and at night were almost equal in September and October. Latent heat flux at the forest floor was estimated to be around 94 MJ m −2 annually, from our measurement with the simulation model. (author)

Numerical Heat Transfer Studies of a Latent Heat Storage System Containing Nano-Enhanced Phase Change Material

Directory of Open Access Journals (Sweden)

S F Hosseinizadeh

2011-01-01

Full Text Available The heat transfer enhancement in the latent heat thermal energy storage system through dispersion of nanoparticle is reported. The resulting nanoparticle-enhanced phase change materials (NEPCM exhibit enhanced thermal conductivity in comparison to the base material. The effects of nanoparticle volume fraction and some other parameters such as natural convection are studied in terms of solid fraction and the shape of the solid-liquid phase front. It has been found that higher nanoparticle volume fraction result in a larger solid fraction. The present results illustrate that the suspended nanoparticles substantially increase the heat transfer rate and also the nanofluid heat transfer rate increases with an increase in the nanoparticles volume fraction. The increase of the heat release rate of the NEPCM shows its great potential for diverse thermal energy storage application.

Mixtures of Gaussians for uncertainty description in bivariate latent heat flux proxies

NARCIS (Netherlands)

Wójcik, R.; Troch, P.A.A.; Stricker, J.N.M.; Torfs, P.J.J.F.

2006-01-01

This paper proposes a new probabilistic approach for describing uncertainty in the ensembles of latent heat flux proxies. The proxies are obtained from hourly Bowen ratio and satellite-derived measurements, respectively, at several locations in the southern Great Plains region in the United States.

Joseph Black, carbon dioxide, latent heat, and the beginnings of the discovery of the respiratory gases.

Science.gov (United States)

West, John B

2014-06-15

The discovery of carbon dioxide by Joseph Black (1728-1799) marked a new era of research on the respiratory gases. His initial interest was in alkalis such as limewater that were thought to be useful in the treatment of renal stone. When he studied magnesium carbonate, he found that when this was heated or exposed to acid, a gas was evolved that he called "fixed air" because it had been combined with a solid material. He showed that the new gas extinguished a flame, that it could not support life, and that it was present in gas exhaled from the lung. Within a few years of his discovery, hydrogen, nitrogen, and oxygen were also isolated. Thus arguably Black's work started the avalanche of research on the respiratory gases carried out by Priestley, Scheele, Lavoisier, and Cavendish. Black then turned his attention to heat and he was the first person to describe latent heat, that is the heat added or lost when a liquid changes its state, for example when water changes to ice or steam. Latent heat is a key concept in thermal physiology because of the heat lost when sweat evaporates. Black was a friend of the young James Watt (1736-1819) who was responsible for the development of early steam engines. Watt was puzzled why so much cooling was necessary to condense steam into water, and Black realized that the answer was the latent heat. The resulting improvements in steam engines ushered in the Industrial Revolution. Copyright © 2014 the American Physiological Society.

Modelling and simulation of phase change material latent heat storages applied to a solar-powered Organic Rankine Cycle

International Nuclear Information System (INIS)

Manfrida, Giampaolo; Secchi, Riccardo; Stańczyk, Kamil

2016-01-01

Highlights: • A mathematical model of a Latent Heat Storage system was developed. • Energy and exergy analysis of the storage system were carried out. • A solar powered ORC unit coupled with the Latent Heat Storage was studied. • The dynamic performance of the overall plant was simulated with TRNSYS. - Abstract: Solar energy is one of the most promising renewable energy sources, but is intermittent by its nature. The study of efficient thermal heat storage technologies is of fundamental importance for the development of solar power systems. This work focuses on a robust mathematical model of a Latent Heat Storage (LHS) system constituted by a storage tank containing Phase Change Material spheres. The model, developed in EES environment, provides the time-dependent temperature profiles for the PCM and the heat transfer fluid flowing in the storage tank, and the energy and exergy stored as well. A case study on the application of the LHS technology is also presented. The operation of a solar power plant associated with a latent heat thermal storage and an ORC unit is simulated under dynamic (time-varying) solar radiation conditions with the software TRNSYS. The performance of the proposed plant is simulated over a one week period, and the results show that the system is able to provide power in 78.5% of the time, with weekly averaged efficiencies of 13.4% for the ORC unit, and of 3.9% for the whole plant (from solar radiation to net power delivered by the ORC expander).

Wallboard with Latent Heat Storage for Passive Solar Applications; TOPICAL

International Nuclear Information System (INIS)

Kedl, R.J.

2001-01-01

Conventional wallboard impregnated with octadecane paraffin[melting point-23 C (73.5 F)] is being developed as a building material with latent heat storage for passive solar and other applications. Impregnation was accomplished simply by soaking the wallboard in molten wax. Concentrations of wax in the combined product as high as 35% by weight can be achieved. Scale-up of the soaking process, from small laboratory samples to full-sized 4- by 8-ft sheets, has been successfully accomplished. The required construction properties of wallboard are maintained after impregnation, that is, it can be painted and spackled. Long-term, high-temperature exposure tests and thermal cycling tests showed no tendency of the paraffin to migrate within the wallboard, and there was no deterioration of thermal energy storage capacity. In support of this concept, a computer model was developed to handle thermal transport and storage by a phase change material (PCM) dispersed in a porous media. The computer model was confirmed by comparison with known analytical solutions and also by comparison with temperatures measured in wallboard during an experimentally generated thermal transient. Agreement between the model and known solution was excellent. Agreement between the model and thermal transient was good, only after the model was modified to allow the PCM to melt over a temperature range, rather than at a specific melting point. When the melting characteristics of the PCM (melting point, melting range, and heat of fusion), as determined from a differential scanning calorimeter plot, were used in the model, agreement between the model and transient data was very good. The confirmed computer model may now be used in conjunction with a building heating and cooling code to evaluate design parameters and operational characteristics of latent heat storage wallboard for passive solar applications

Spectral estimates of net radiation and soil heat flux

International Nuclear Information System (INIS)

Daughtry, C.S.T.; Kustas, W.P.; Moran, M.S.; Pinter, P.J. Jr.; Jackson, R.D.; Brown, P.W.; Nichols, W.D.; Gay, L.W.

1990-01-01

Conventional methods of measuring surface energy balance are point measurements and represent only a small area. Remote sensing offers a potential means of measuring outgoing fluxes over large areas at the spatial resolution of the sensor. The objective of this study was to estimate net radiation (Rn) and soil heat flux (G) using remotely sensed multispectral data acquired from an aircraft over large agricultural fields. Ground-based instruments measured Rn and G at nine locations along the flight lines. Incoming fluxes were also measured by ground-based instruments. Outgoing fluxes were estimated using remotely sensed data. Remote Rn, estimated as the algebraic sum of incoming and outgoing fluxes, slightly underestimated Rn measured by the ground-based net radiometers. The mean absolute errors for remote Rn minus measured Rn were less than 7%. Remote G, estimated as a function of a spectral vegetation index and remote Rn, slightly overestimated measured G; however, the mean absolute error for remote G was 13%. Some of the differences between measured and remote values of Rn and G are associated with differences in instrument designs and measurement techniques. The root mean square error for available energy (Rn - G) was 12%. Thus, methods using both ground-based and remotely sensed data can provide reliable estimates of the available energy which can be partitioned into sensible and latent heat under non advective conditions

Retrieving latent heating vertical structure from cloud and precipitation Profiles—Part I: Warm rain processes

International Nuclear Information System (INIS)

Min, Qilong; Li, Rui; Wu, Xiaoqing; Fu, Yunfei

2013-01-01

An exploratory study on physical based latent heat (LH) retrieval algorithm is conducted by parameterizing the physical linkages of hydrometeor profiles of cloud and precipitation to the major processes related to the phase change of atmospheric water. Specifically, rain events are segregated into three rain types: warm, convective, and stratiform, based on their dynamical and thermodynamical characteristics. As the first of the series, only the warm rain LH algorithm is presented and evaluated here. The major microphysical processes of condensation and evaporation for warm rain are parameterized through traditional rain growth theory, with the aid of Cloud Resolving Model (CRM) simulations. The evaluation or the self-consistency tests indicate that the physical based retrievals capture the fundamental LH processes associated with the warm rain life cycle. There is no significant systematic bias in terms of convection strength, illustrated by the month-long CRM simulation as the mesoscale convective systems (MCSs) experience from initial, mature, to decay stages. The overall monthly-mean LH comparison showed that the total LH, as well as condensation heating and evaporation cooling components, agree with the CRM simulation. -- Highlights: ► An exploratory study on physics-based warm rain latent heat retrieval algorithm. ► Utilize the full information of the vertical structures of cloud and rainfall. ► Directly link water mass measurements to latent heat at instantaneous pixel level. ► Applicable at various stages of cloud system life cycle

Experimental and numerical study of latent heat thermal energy storage systems assisted by heat pipes for concentrated solar power application

Science.gov (United States)

Tiari, Saeed

A desirable feature of concentrated solar power (CSP) with integrated thermal energy storage (TES) unit is to provide electricity in a dispatchable manner during cloud transient and non-daylight hours. Latent heat thermal energy storage (LHTES) offers many advantages such as higher energy storage density, wider range of operating temperature and nearly isothermal heat transfer relative to sensible heat thermal energy storage (SHTES), which is the current standard for trough and tower CSP systems. Despite the advantages mentioned above, LHTES systems performance is often limited by low thermal conductivity of commonly used, low cost phase change materials (PCMs). Research and development of passive heat transfer devices, such as heat pipes (HPs) to enhance the heat transfer in the PCM has received considerable attention. Due to its high effective thermal conductivity, heat pipe can transport large amounts of heat with relatively small temperature difference. The objective of this research is to study the charging and discharging processes of heat pipe-assisted LHTES systems using computational fluid dynamics (CFD) and experimental testing to develop a method for more efficient energy storage system design. The results revealed that the heat pipe network configurations and the quantities of heat pipes integrated in a thermal energy storage system have a profound effect on the thermal response of the system. The optimal placement of heat pipes in the system can significantly enhance the thermal performance. It was also found that the inclusion of natural convection heat transfer in the CFD simulation of the system is necessary to have a realistic prediction of a latent heat thermal storage system performance. In addition, the effects of geometrical features and quantity of fins attached to the HPs have been studied.

Resveratrol Reactivates Latent HIV through Increasing Histone Acetylation and Activating Heat Shock Factor 1.

Science.gov (United States)

Zeng, Xiaoyun; Pan, Xiaoyan; Xu, Xinfeng; Lin, Jian; Que, Fuchang; Tian, Yuanxin; Li, Lin; Liu, Shuwen

2017-06-07

The persistence of latent HIV reservoirs presents a significant challenge to viral eradication. Effective latency reversing agents (LRAs) based on "shock and kill" strategy are urgently needed. The natural phytoalexin resveratrol has been demonstrated to enhance HIV gene expression, although its mechanism remains unclear. In this study, we demonstrated that resveratrol was able to reactivate latent HIV without global T cell activation in vitro. Mode of action studies showed resveratrol-mediated reactivation from latency did not involve the activation of silent mating type information regulation 2 homologue 1 (SIRT1), which belonged to class-3 histone deacetylase (HDAC). However, latent HIV was reactivated by resveratrol mediated through increasing histone acetylation and activation of heat shock factor 1 (HSF1). Additionally, synergistic activation of the latent HIV reservoirs was observed under cotreatment with resveratrol and conventional LRAs. Collectively, this research reveals that resveratrol is a natural LRA and shows promise for HIV therapy.

Examination of Conservatism in Early/Latent Fatality Estimation in Level 3 PRA

International Nuclear Information System (INIS)

Kim, Sung-yeop; Lee, Haneol; Yim, Man-Sung

2014-01-01

Due to the computational model driven-nature of the work, there exist various sources of uncertainty in level 3 PRA. They are related with source release, environmental transport and deposition, human behavior involved in dosimetry, health effect and risk assessment. For instance, a total of 376 parameters have been considered in Probabilistic Accident Consequence Uncertainty Assessment Using COSYMA and the details on the number of parameters in each analysis are listed in Table 1. In 2012, the report of NPP accident consequence simulation was distributed by the Korean Federation for Environmental Movement (KFEM). They insisted that Kori Nuclear Power Plant (NPP) accident would lead to 48,000 early fatalities and 850,000 cancer fatalities in Busan and Hanbit NPP accident would lead to 550,000 cancer fatalities in Seoul. This report exemplifies the misuse of collective dose, that is effective dose multiplied by population and time. Even though very low effective dose is considered, collective dose could give over-conservative estimate when high population and long time period is multiplied. International Commission on Radiological Protection (ICRP) forewarned about the misuse of collective dose, in their ICRP Publication 103, such as applying it to simplified calculation of fatality and risk. As part of investigation of conservatism in early and latent fatality estimation, the existing methods of early and latent fatality calculation was reviewed and the results from the use of the existing methodology were examined in this study. The method of early and latent fatality estimation in level 3 PRA was investigated and the conservatism in the result was examined in this study. For the purpose of estimating both early and latent fatality, appropriate dose distributions among the affected population are found to be important. This study showed that large conservatism may be involved in the estimated fatality if the distribution of population dose as a function of

Examination of Conservatism in Early/Latent Fatality Estimation in Level 3 PRA

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung-yeop; Lee, Haneol; Yim, Man-Sung [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2014-10-15

Due to the computational model driven-nature of the work, there exist various sources of uncertainty in level 3 PRA. They are related with source release, environmental transport and deposition, human behavior involved in dosimetry, health effect and risk assessment. For instance, a total of 376 parameters have been considered in Probabilistic Accident Consequence Uncertainty Assessment Using COSYMA and the details on the number of parameters in each analysis are listed in Table 1. In 2012, the report of NPP accident consequence simulation was distributed by the Korean Federation for Environmental Movement (KFEM). They insisted that Kori Nuclear Power Plant (NPP) accident would lead to 48,000 early fatalities and 850,000 cancer fatalities in Busan and Hanbit NPP accident would lead to 550,000 cancer fatalities in Seoul. This report exemplifies the misuse of collective dose, that is effective dose multiplied by population and time. Even though very low effective dose is considered, collective dose could give over-conservative estimate when high population and long time period is multiplied. International Commission on Radiological Protection (ICRP) forewarned about the misuse of collective dose, in their ICRP Publication 103, such as applying it to simplified calculation of fatality and risk. As part of investigation of conservatism in early and latent fatality estimation, the existing methods of early and latent fatality calculation was reviewed and the results from the use of the existing methodology were examined in this study. The method of early and latent fatality estimation in level 3 PRA was investigated and the conservatism in the result was examined in this study. For the purpose of estimating both early and latent fatality, appropriate dose distributions among the affected population are found to be important. This study showed that large conservatism may be involved in the estimated fatality if the distribution of population dose as a function of

Latent heat storage by silica-coated polymer beads containing organic phase change materials

Czech Academy of Sciences Publication Activity Database

Feczkó, T.; Trif, L.; Horák, Daniel

2016-01-01

Roč. 132, July (2016), s. 405-414 ISSN 0038-092X R&D Projects: GA MŠk(CZ) LH14318 Institutional support: RVO:61389013 Keywords : latent heat storage * phase change materials * porous beads by suspension polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.018, year: 2016

Time and spatial heat transfer performance around an isothermally heated sphere placed in a uniform, downwardly directed flow (in relation to the enhancement of latent heat storage rate in a spherical capsule)

International Nuclear Information System (INIS)

Koizumi, H.

2004-01-01

The aim of this study is to reveal the temporal and spatial heat transfer performance of an isothermally heated sphere placed in a uniform, downwardly directed flow using a micro-foil heat flow sensor (HFS). A HFS, whose response time is about 0.02 s, was pasted on the surface of a heated copper sphere. Experiments were carried out using air with a Grashof number of 3.3 x 10 5 and with several Reynolds numbers (Re) up to 1800. Three flow patterns appeared: a chaotic flow at Re<240; a two-dimensional steady separated flow at 240 ≤ Re<500, and a three-dimensional unsteady separated flow at Re ≥ 500. In addition, the instantaneous and time-averaged heat transfer performance around the sphere in each of the three regions was clarified. Next, enhancement of the latent heat storage rate of a solid phase change material (PCM) in a spherical capsule was performed. The flow around the spherical capsule, in which the solid PCM was filled and placed in a heated, upwardly directed flow, is the approximate adverse flow phenomenon around the heated sphere which was placed in a downwardly directed flow. In other words, the buoyant flow and the forced flow are in the opposite directions in these two cases. Tests of latent heat storage were run for two Reynolds numbers which represented different flow characteristics in the heat transfer experiments, Re=150 and 1800. Furthermore, copper plates were inserted into the solid PCM, of which thermal conductivity was considerably low, to enhance the latent heat storage rate for the two Reynolds number flows

An experimental investigation of shell and tube latent heat storage for solar dryer using paraffin wax as heat storage material

Directory of Open Access Journals (Sweden)

Ashish Agarwal

2016-03-01

Full Text Available In the presented study the shell and tube type latent heat storage (LHS has been designed for solar dryer and paraffin wax is used as heat storage material. In the first part of the study, the thermal and heat transfer characteristics of the latent heat storage system have been evaluated during charging and discharging process using air as heat transfer fluid (HTF. In the last section of the study the effectiveness of the use of an LHS for drying of food product and also on the drying kinetics of a food product has been determined. A series of experiments were conducted to study the effects of flow rate and temperature of HTF on the charging and discharging process of LHS. The temperature distribution along the radial and longitudinal directions was obtained at different time during charging process to analyze the heat transfer phenomenon in the LHS. Thermal performance of the system is evaluated in terms of cumulative energy charged and discharged, during the charging and discharging process of LHS, respectively. Experimental results show that the LHS is suitable to supply the hot air for drying of food product during non-sunshine hours or when the intensity of solar energy is very low. Temperature gain of air in the range of 17 °C to 5 °C for approximately 10 hrs duration was achieved during discharging of LHS.

Incorporating Latent Variables into Discrete Choice Models - A Simultaneous Estimation Approach Using SEM Software

Directory of Open Access Journals (Sweden)

Dirk Temme

2008-12-01

Full Text Available Integrated choice and latent variable (ICLV models represent a promising new class of models which merge classic choice models with the structural equation approach (SEM for latent variables. Despite their conceptual appeal, applications of ICLV models in marketing remain rare. We extend previous ICLV applications by first estimating a multinomial choice model and, second, by estimating hierarchical relations between latent variables. An empirical study on travel mode choice clearly demonstrates the value of ICLV models to enhance the understanding of choice processes. In addition to the usually studied directly observable variables such as travel time, we show how abstract motivations such as power and hedonism as well as attitudes such as a desire for flexibility impact on travel mode choice. Furthermore, we show that it is possible to estimate such a complex ICLV model with the widely available structural equation modeling package Mplus. This finding is likely to encourage more widespread application of this appealing model class in the marketing field.

Complementary-relationship-based 30 year normals (1981-2010) of monthly latent heat fluxes across the contiguous United States

Science.gov (United States)

Szilagyi, Jozsef

2015-11-01

Thirty year normal (1981-2010) monthly latent heat fluxes (ET) over the conterminous United States were estimated by a modified Advection-Aridity model from North American Regional Reanalysis (NARR) radiation and wind as well as Parameter-Elevation Regressions on Independent Slopes Model (PRISM) air and dew-point temperature data. Mean annual ET values were calibrated with PRISM precipitation (P) and validated against United States Geological Survey runoff (Q) data. At the six-digit Hydrologic Unit Code level (sample size of 334) the estimated 30 year normal runoff (P - ET) had a bias of 18 mm yr-1, a root-mean-square error of 96 mm yr-1, and a linear correlation coefficient value of 0.95, making the estimates on par with the latest Land Surface Model results but without the need for soil and vegetation information or any soil moisture budgeting.

Melting and solidification characteristics of a mixture of two types of latent heat storage material in a vessel

Science.gov (United States)

Yu, JikSu; Horibe, Akihiko; Haruki, Naoto; Machida, Akito; Kato, Masashi

2016-11-01

In this study, we investigated the fundamental melting and solidification characteristics of mannitol, erythritol, and their mixture (70 % by mass mannitol: 30 % by mass erythritol) as potential phase-change materials (PCMs) for latent heat thermal energy storage systems, specifically those pertaining to industrial waste heat, having temperatures in the range of 100-250 °C. The melting point of erythritol and mannitol, the melting peak temperature of their mixture, and latent heat were measured using differential scanning calorimetry. The thermal performance of the mannitol mixture was determined during melting and solidification processes, using a heat storage vessel with a pipe heat exchanger. Our results indicated phase-change (fusion) temperatures of 160 °C for mannitol and 113 and 150 °C for the mannitol mixture. Nondimensional correlation equations of the average heat transfer during the solidification process, as well as the temperature and velocity efficiencies of flowing silicon oil in the pipe and the phase-change material (PCM), were derived using several nondimensional parameters.

Experimental investigations on cylindrical latent heat storage units with sodium acetate trihydrate composites utilizing supercooling

DEFF Research Database (Denmark)

Dannemand, Mark; Johansen, Jakob Berg; Kong, Weiqiang

2016-01-01

Latent heat storage units utilizing stable supercooling of sodium acetate trihydrate (SAT) composites were tested in a laboratory. The stainless steel units were 1.5 m high cylinders with internal heat exchangers of tubes with fins. One unit was tested with 116 kg SAT with 6% extra water. Another...... in the thickened phase change material after melting. The heat content in the fully charged state and the heat released after solidification of the supercooled SAT mixtures at ambient temperature was higher for the unit with the thickened SAT mixture. The heat discharged after solidification of the supercooled SAT...

Thermal properties and reliability of eutectic mixture of stearic acid-acetamide as phase change material for latent heat storage

International Nuclear Information System (INIS)

Ma, Guixiang; Han, Lipeng; Sun, Jinhe; Jia, Yongzhong

2017-01-01

Highlights: • The system of stearic acid-acetamide binary mixtures were studied as phase change material. • The eutectic mixtures featured low melting temperatures and high latent heats of fusion for latent heat storage. • Solid-liquid phase diagrams for the system were constructed. • Negligible change in stability after 500 heating/cooling cycles. - Abstract: The thermal properties and reliability of the stearic acid (SA) with acetamide (AC) binary mixture were characterized using differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). The phase diagrams for the SA-AC binary mixture with AC in the metastable and the stable form were constructed. The eutectic system with stable AC is 0.604 mol fraction SA, and displayed a melting temperature (T m ) of 64.55 °C and latent heat of melting (ΔH m ) of 193.87 J·g −1 . The eutectic systems with metastable AC are 0.397 and 0.604 mol fraction SA. The melting temperatures are 62.23 °C and 62.54 °C, and latent heats of fusion are 222.10 J·g −1 and 194.28 J·g −1 , respectively. Following accelerated thermal cycling tests, TG and FT-IR analysis indicate that the eutectic mixture (χ SA = 0.397) with the metastable AC has good cyclic and thermal stability. The results show that the SA-AC eutectic mixture use as phase change material (PCM) possess good prospect for low temperature thermal energy storage (TES) applications.

Changing storm track diffusivity and the upper limit to poleward latent heat transport

Science.gov (United States)

Caballero, R.

2010-12-01

Poleward atmospheric energy transport plays a key role in the climate system by helping set the mean equator-pole temperature gradient. The mechanisms controlling the response of poleward heat flux to climate change are still poorly understood. Recent work shows that midlatitude poleward latent heat flux in atmospheric GCMs generally increases as the climate warms but reaches an upper limit at sufficiently high temperature and decreases with further warming. The reasons for this non-monotonic behavior have remained unclear. Simple arguments suggests that the latent heat flux Fl should scale as Fl ˜ vref qs, where vref is a typical meridional velocity in the baroclinic zone and qs is saturation humidity. While vref decreases with temperature, qs increases much more rapidly, so this scaling implies monotonically increasing moisture flux. We study this problem using a series of simulations employing NCAR’s CAM3 GCM coupled to a slab-ocean aquaplanet and spanning a wide range of atmospheric CO2 concentrations. We find that a modified scaling, Fl ˜ vref2 qs, describes the changes in moisture flux much more accurately. Using Lagrangian trajectory analysis, we explain the success of this scaling in terms of changes in the mixing length, which contracts proportionally to vref.

Eutectic mixtures of some fatty acids for latent heat storage: Thermal properties and thermal reliability with respect to thermal cycling

International Nuclear Information System (INIS)

Sari, Ahmet

2006-01-01

Accelerated thermal cycle tests have been conducted to study the change in melting temperatures and latent heats of fusion of the eutectic mixtures of lauric acid (LA)-myristic acid (MA), lauric acid (LA)-palmitic acid (PA) and myristic acid (MA)-stearic acid (SA) as latent heat storage materials. The thermal properties of these materials were determined by the differential scanning calorimetry (DSC) analysis method. The thermal reliability of the eutectic mixtures after melt/freeze cycles of 720, 1080 and 1460 was also evaluated using the DSC curves. The accelerated thermal cycle tests indicate that the melting temperatures usually tend to decrease, and the variations in the latent heats of fusion are irregular with increasing number of thermal cycles. Moreover, the probable reasons for the change in thermal properties of the eutectic mixtures after repeated thermal cycles were investigated. Fourier Transform Infrared (FT-IR) spectroscopic analysis indicates that the accelerated melt/freeze processes do not cause any degradation in the chemical structure of the mixtures. The change in thermal properties of the eutectic mixtures with increasing number of thermal cycles is only because of the presence of certain amounts of impurities in the fatty acids used in their preparation. It is concluded that the tested eutectic mixtures have reasonable thermal properties and thermal reliability as phase change materials (PCMs) for latent heat storage in any solar heating applications that include a four year utilization period

Statistical analysis of latent generalized correlation matrix estimation in transelliptical distribution.

Science.gov (United States)

Han, Fang; Liu, Han

2017-02-01

Correlation matrix plays a key role in many multivariate methods (e.g., graphical model estimation and factor analysis). The current state-of-the-art in estimating large correlation matrices focuses on the use of Pearson's sample correlation matrix. Although Pearson's sample correlation matrix enjoys various good properties under Gaussian models, its not an effective estimator when facing heavy-tail distributions with possible outliers. As a robust alternative, Han and Liu (2013b) advocated the use of a transformed version of the Kendall's tau sample correlation matrix in estimating high dimensional latent generalized correlation matrix under the transelliptical distribution family (or elliptical copula). The transelliptical family assumes that after unspecified marginal monotone transformations, the data follow an elliptical distribution. In this paper, we study the theoretical properties of the Kendall's tau sample correlation matrix and its transformed version proposed in Han and Liu (2013b) for estimating the population Kendall's tau correlation matrix and the latent Pearson's correlation matrix under both spectral and restricted spectral norms. With regard to the spectral norm, we highlight the role of "effective rank" in quantifying the rate of convergence. With regard to the restricted spectral norm, we for the first time present a "sign subgaussian condition" which is sufficient to guarantee that the rank-based correlation matrix estimator attains the optimal rate of convergence. In both cases, we do not need any moment condition.

Latent Heating Profiles Derived from ARM Radar Observations in MC3E and GoAmazon Field Campaigns

Science.gov (United States)

Min, Q.; Li, R.; Mu, Z.; Giangrande, S. E.; Wang, Y.

2016-12-01

Atmosphere latent heating (LH) is released through water phase change processes in the atmosphere. There is a physical connection between LH rate and updraft velocity (ω) inside clouds. In this study, we develop a new LH algorithm based on a quantified LH-ω relationship found in cloud resolving model (CRM) simulations. The self-consistency check with CRM simulations shows that the retrievals correctly replicate the main features of LH profiles, including their total and individual components (i.e. condensation-evaporation heating rate, deposition-sublimation heating rate, and freezing-melting heating rate). Further, the algorithm is applied to real cases from the DOE-ARM MC3E and GoAmazon2014/6 Field Campaigns using available UHF (915 and 1290 MHz) zenith radar retrievals of vertical velocity and rain rate as input. The retrieved LH profiles in the deep convective rains show positive heating throughout the column, the LH profiles in the stratiform rains with well-defined bright-band showing clear dipole patterns with positive heating above and negative cooling below the freezing level. The altitudes of maximum heating in the widespread stratiform regimes are clearly higher than those found within deep convective regions. Overall, these Latent heating rate profiles, as an important geophysical quantity of interest, can provide useful climate diagnostic data, and ultimately, constraints for model-based analyses of large-scale heating distributions.

Thermal reliability test of Al-34%Mg-6%Zn alloy as latent heat storage material and corrosion of metal with respect to thermal cycling

International Nuclear Information System (INIS)

Sun, J.Q.; Zhang, R.Y.; Liu, Z.P.; Lu, G.H.

2007-01-01

The purpose of this study is to determine the thermal reliability and corrosion of the Al-34%Mg-6%Zn alloy as a latent heat energy storage material with respect to various numbers of thermal cycles. The differential scanning calorimeter (DSC) analysis technique was applied to the alloy after 0, 50, 500 and 1000 melting/solidification cycles in order to measure the melting temperatures and the latent heats of fusion of the alloy. The containment materials were stainless steel (SS304L), carbon steel (steel C20) in the corrosion tests. The DSC results indicated that the change in melting temperature for the alloy was in the range of 3.06-5.3 K, and the latent heat of fusion decreased 10.98% after 1000 thermal cycles. The results show that the investigated Al-34%Mg-6%Zn alloy has a good thermal reliability as a latent heat energy storage material with respect to thermal cycling for thermal energy storage applications in the long term in view of the small changes in the latent heat of fusion and melting temperature. Gravimetric analysis as mass loss (mg/cm 2 ), corrosion rate (mg/day) and a microscopic or metallographic investigation were performed for corrosion tests and showed that SS304L may be considered a more suitable alloy than C20 in long term thermal storage applications

Process for using a saturated salt hydrate solution as a heat storing material in a latent heat storage device. Anvendelse av en mettet salthydratloesning som varme-lagringsmateriale i et latent varmemagasin

Energy Technology Data Exchange (ETDEWEB)

Wasel-Nielen, J.; Merkenich, K.; Gehrig, O.; Sommer, K.

1984-06-12

Disclosed is a process for preparing a salt composition having a phase transition heat greater than the heat capacity of water at a corresponding temperature, for charging a latent heat storage device. The process comprises the steps of providing an acid component of the salt hydrate; providing a base component of the salt hydrate, wherein at least one of the acid or base components comprises a liquid; and mixing the acid component and the base component together to cause a neutralization reaction. The acid and base components are mixed in a ratio and in respective concentrations to produce a salt hydrate solution saturated at the desired phase transition point. The claims concern the use of saturated salt hydrate solution with a certain phase transition heat produced in a particular way.

Computational modeling of latent-heat-storage in PCM modified interior plaster

Energy Technology Data Exchange (ETDEWEB)

Fořt, Jan; Maděra, Jiří; Trník, Anton; Pavlíková, Milena; Pavlík, Zbyšek [Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague (Czech Republic)

2016-06-08

The latent heat storage systems represent a promising way for decrease of buildings energy consumption with respect to the sustainable development principles of building industry. The presented paper is focused on the evaluation of the effect of PCM incorporation on thermal performance of cement-lime plasters. For basic characterization of the developed materials, matrix density, bulk density, and total open porosity are measured. Thermal conductivity is accessed by transient impulse method. DSC analysis is used for the identification of phase change temperature during the heating and cooling process. Using DSC data, the temperature dependent specific heat capacity is calculated. On the basis of the experiments performed, the supposed improvement of the energy efficiency of characteristic building envelope system where the designed plasters are likely to be used is evaluated by a computational analysis. Obtained experimental and computational results show a potential of PCM modified plasters for improvement of thermal stability of buildings and moderation of interior climate.

Two-wavelength Method Estimates Heat fluxes over Heterogeneous Surface in North-China

Science.gov (United States)

Zhang, G.; Zheng, N.; Zhang, J.

2017-12-01

Heat fluxes is a key process of hydrological and heat transfer of soil-plant-atmosphere continuum (SPAC), and now it is becoming an important topic in meteorology, hydrology, ecology and other related research areas. Because the temporal and spatial variation of fluxes at regional scale is very complicated, it is still difficult to measure fluxes at the kilometer scale over a heterogeneous surface. A technique called "two-wavelength method" which combines optical scintillometer with microwave scintillometer is able to measure both sensible and latent heat fluxes over large spatial scales at the same time. The main purpose of this study is to investigate the fluxes over non-uniform terrain in North-China. Estimation of heat fluxes was carried out with the optical-microwave scintillometer and an eddy covariance (EC) system over heterogeneous surface in Tai Hang Mountains, China. EC method was set as a benchmark in the study. Structure parameters obtained from scintillometer showed that the typical measurement values of Cn2 are around 10-13 m-2/3 for microwave scintillometer, and values of Cn2 were around 10-15 m-2/3 for optical scintillometer. The correlation of heat fluxes (H) derived from scintillometer and EC system showed as a ratio of 1.05,and with R2=0.75, while the correlation of latent heat fluxes (LE) showed as 1.29 with R2=0.67. It was also found that heat fluxes derived from the two system showed good agreement (R2=0.9 for LE, R2=0.97 for H) when the Bowen ratio (β) was 1.03, while discrepancies showed significantly when β=0.75, and RMSD in H was 139.22 W/m2, 230.85 W/m2 in LE respectively.Experiment results in our research shows that, the two-wavelength method gives a larger heat fluxes over the study area, and a deeper study should be conduct. We expect that our investigate and analysis can be promoted the application of scintillometry method in regional evapotranspiration measurements and relevant disciplines.

Theoretical predictions for latent heats and phase-change temperatures of polycrystalline PCMs

Science.gov (United States)

Medved', Igor; Trník, Anton

2017-07-01

We had previously developed a microscopic approach from which it is possible to fit enthalpy jumps and heat capacity peaks of polycrystalline phase-change materials that consists of a large number of grains. It is also possible to determine the corresponding latent heat and phase-change temperature. These results are given in a form of sums over grain diameters that can be evaluated numerically. Therefore, their behavior and dependence on physical parameters are not susceptible to straightforward interpretations. Here we use the results to derive simple formulas for the maximum position (Tmax), height (H), and an asymmetry factor (α) of those heat capacity peaks that are very asymmetric. In addition, we express the phase-change temperature as a simple combination of Tmax, H, α, and the peak's area. We apply our formulas to Rhubitherm 27 as an example PCM for which the heat capacity peak is so asymmetric that it has about 80 % of its total area below its maximum position.

An experimental study on the heat transfer characteristics of a heat pipe heat exchanger with latent heat storage. Part II: Simultaneous charging/discharging modes

International Nuclear Information System (INIS)

Liu Zhongliang; Wang Zengyi; Ma Chongfang

2006-01-01

In this part of the paper, the performance of the simultaneous charging/discharging operation modes of the heat pipe heat exchanger with latent heat storage is experimentally studied. The experimental results show that the device may operate under either the fluid to fluid heat transfer with charging heat to the phase change material (PCM) or the fluid to fluid heat transfer with discharging heat from the PCM modes according to the initial temperature of the PCM. The melting/solidification curves, the performances of the heat pipes and the device, the influences of the inlet temperature and the mass flow rate of the cold water on the operation performance are investigated by extensive experiments. The experimental results also disclose that under the simultaneous charging/discharging operation mode, although the heat transfer from the hot water directly to the cold water may vary, it always takes up a major part of the total heat recovered by the cold water due to the very small thermal resistance compared with the thermal resistance of the PCM side. The melting/solidification processes taking place in the simultaneous charging/discharging operation are compared with those in the charging only and discharging only processes. By applying a simplified thermal resistance analysis, a criterion for predicting the exact operation modes was derived and used to explain the observed experimental phenomena

Development of Latent Heat Storage Phase Change Material Containing Plaster

Directory of Open Access Journals (Sweden)

Diana BAJARE

2016-05-01

Full Text Available This paper reviews the development of latent heat storage Phase Change Material (PCM containing plaster as in passive application. Due to the phase change, these materials can store higher amounts of thermal energy than traditional building materials and can be used to add thermal inertia to lightweight constructions. It was shown that the use of PCMs have advantages stabilizing the room temperature variations during summer days, provided sufficient night ventilation is allowed. Another advantage of PCM usage is stabilized indoor temperature on the heating season. The goal of this study is to develop cement and lime based plaster containing microencapsulated PCM. The plaster is expected to be used for passive indoor applications and enhance the thermal properties of building envelope. The plaster was investigated under Scanning Electron Microscope and the mechanical, physical and thermal properties of created plaster samples were determined.

Applying a Weighted Maximum Likelihood Latent Trait Estimator to the Generalized Partial Credit Model

Science.gov (United States)

Penfield, Randall D.; Bergeron, Jennifer M.

2005-01-01

This article applies a weighted maximum likelihood (WML) latent trait estimator to the generalized partial credit model (GPCM). The relevant equations required to obtain the WML estimator using the Newton-Raphson algorithm are presented, and a simulation study is described that compared the properties of the WML estimator to those of the maximum…

Solar heating and cooling system with absorption chiller and low temperature latent heat storage: Energetic performance and operational experience

Energy Technology Data Exchange (ETDEWEB)

Helm, M.; Keil, C.; Hiebler, S.; Mehling, H.; Schweigler, C. [Bavarian Center for Applied Energy Research (ZAE Bayern) (Germany)

2009-06-15

Absorption cooling systems based on water/lithium bromide (LiBr) solution typically require an open wet cooling tower to transfer the reject heat to the ambient. Yet, water consumption, the need for water make-up and cleaning, formation of fog, and the risk of Legionella bacteria growth are hindering factors for the implementation of small solar cooling systems. The application of a latent heat storage supporting the heat rejection of the absorption chiller in conjunction with a dry cooling system allows eliminating the wet cooling tower. By that means heat rejection of the chiller is shifted to periods with lower ambient temperatures, i.e. night time or off-peak hours. The system concept and the hydraulic scheme together with an analysis of the energetic performance of the system are presented, followed by a report on the operation of a first pilot installation. (author)

Lauric and palmitic acids eutectic mixture as latent heat storage material for low temperature heating applications

International Nuclear Information System (INIS)

Tuncbilek, Kadir; Sari, Ahmet; Tarhan, Sefa; Erguenes, Gazanfer; Kaygusuz, Kamil

2005-01-01

Palmitic acid (PA, 59.8 deg. C) and lauric acid (LA, 42.6 deg. C) are phase change materials (PCM) having quite high melting temperatures which can limit their use in low temperature solar applications such as solar space heating and greenhouse heating. However, their melting temperatures can be tailored to appropriate value by preparing a eutectic mixture of the lauric and the palmitic acids. In the present study, the thermal analysis based on differential scanning calorimetry (DSC) technique shows that the mixture of 69.0 wt% LA and 31 wt% PA forms a eutectic mixture having melting temperature of 35.2 deg. C and the latent heat of fusion of 166.3 J g -1 . This study also considers the experimental determination of the thermal characteristics of the eutectic mixture during the heat charging and discharging processes. Radial and axial temperature distribution, heat transfer coefficient between the heat transfer fluid (HTF) pipe and the PCM, heat recovery rate and heat charging and discharging fractions were experimentally established employing a vertical concentric pipe-in-pipe energy storage system. The changes of these characteristics were evaluated with respect to the effect of inlet HTF temperature and mass flow rate. The DSC thermal analysis and the experimental results indicate that the LA-PA eutectic mixture can be a potential material for low temperature thermal energy storage applications in terms of its thermo-physical and thermal characteristics

Phase change and heat transfer characteristics of a eutectic mixture of palmitic and stearic acids as PCM in a latent heat storage system

International Nuclear Information System (INIS)

Baran, Guelseren; Sari, Ahmet

2003-01-01

The phase change and heat transfer characteristics of a eutectic mixture of palmitic and stearic acids as phase change material (PCM) during the melting and solidification processes were determined experimentally in a vertical two concentric pipes energy storage system. This study deals with three important subjects. First is determination of the eutectic composition ratio of the palmitic acid (PA) and stearic acid (SA) binary system and measurement of its thermophysical properties by differential scanning calorimetry (DSC). Second is establishment of the phase transition characteristics of the mixture, such as the total melting and solidification temperatures and times, the heat transfer modes in the melted and solidified PCM and the effect of Reynolds and Stefan numbers as initial heat transfer fluid (HTF) conditions on the phase transition behaviors. Third is calculation of the heat transfer coefficients between the outside wall of the HTF pipe and the PCM, the heat recovery rates and heat fractions during the phase change processes of the mixture and also discussion of the effect of the inlet HTF parameters on these characteristics. The DSC results showed that the PA-SA binary system in the mixture ratio of 64.2:35.8 wt% forms a eutectic, which melts at 52.3 deg. C and has a latent heat of 181.7 J g -1 , and thus, these properties make it a suitable PCM for passive solar space heating and domestic water heating applications with respect to climate conditions. The experimental results also indicated that the eutectic mixture of PA-SA encapsulated in the annulus of concentric double pipes has good phase change and heat transfer characteristics during the melting and solidification processes, and it is an attractive candidate as a potential PCM for heat storage in latent heat thermal energy storage systems

Economic impact of latent heat thermal energy storage systems within direct steam generating solar thermal power plants with parabolic troughs

International Nuclear Information System (INIS)

Seitz, M.; Johnson, M.; Hübner, S.

2017-01-01

Highlights: • Integration of a latent heat thermal energy storage system into a solar direct steam generation power cycle. • Parametric study of solar field and storage size for determination of the optimal layout. • Evaluation of storage impact on the economic performance of the solar thermal power plant. • Economic comparison of new direct steam generation plant layout with state-of-the-art oil plant layout. - Abstract: One possible way to further reduce levelized costs of electricity of concentrated solar thermal energy is to directly use water/steam as the primary heat transfer fluid within a concentrated collector field. This so-called direct steam generation offers the opportunity of higher operating temperatures and better exergy efficiency. A technical challenge of the direct steam generation technology compared to oil-driven power cycles is a competitive storage technology for heat transfer fluids with a phase change. Latent heat thermal energy storages are suitable for storing heat at a constant temperature and can be used for direct steam generation power plants. The calculation of the economic impact of an economically optimized thermal energy storage system, based on a latent heat thermal energy storage system with phase change material, is the main focus of the presented work. To reach that goal, a thermal energy storage system for a direct steam generation power plant with parabolic troughs in the solar field was thermally designed to determine the boundary conditions. This paper discusses the economic impact of the designed thermal energy storage system based on the levelized costs of electricity results, provided via a wide parametric study. A state-of-the-art power cycle with a primary and a secondary heat transfer fluid and a two-tank thermal energy storage is used as a benchmark technology for electricity generation with solar thermal energy. The benchmark and direct steam generation systems are compared to each other, based respectively

Geothermal electricity generation and desalination: an integrated process design to conserve latent heat with operational improvements

KAUST Repository

Missimer, Thomas M.; Ng, Kim Choon; Thuw, Kyaw; Wakil Shahzad, Muhammad

2016-01-01

A new process combination is proposed to link geothermal electricity generation with desalination. The concept involves maximizing the utilization of harvested latent heat by passing the turbine exhaust steam into a multiple effect distillation system and then into an adsorption desalination system. Processes are fully integrated to produce electricity, desalted water for consumer consumption, and make-up water for the geothermal extraction system. Further improvements in operational efficiency are achieved by adding a seawater reverse osmosis system to the site to utilize some of the generated electricity and using on-site aquifer storage and recovery to maximize water production with tailoring of seasonal capacity requirements and to meet facility maintenance requirements. The concept proposed conserves geothermally harvested latent heat and maximizes the economics of geothermal energy development. Development of a fully renewable energy electric generation-desalination-aquifer storage campus is introduced within the framework of geothermal energy development. © 2016 The Author(s). Published by Taylor & Francis

Geothermal electricity generation and desalination: an integrated process design to conserve latent heat with operational improvements

KAUST Repository

Missimer, Thomas M.

2016-02-05

A new process combination is proposed to link geothermal electricity generation with desalination. The concept involves maximizing the utilization of harvested latent heat by passing the turbine exhaust steam into a multiple effect distillation system and then into an adsorption desalination system. Processes are fully integrated to produce electricity, desalted water for consumer consumption, and make-up water for the geothermal extraction system. Further improvements in operational efficiency are achieved by adding a seawater reverse osmosis system to the site to utilize some of the generated electricity and using on-site aquifer storage and recovery to maximize water production with tailoring of seasonal capacity requirements and to meet facility maintenance requirements. The concept proposed conserves geothermally harvested latent heat and maximizes the economics of geothermal energy development. Development of a fully renewable energy electric generation-desalination-aquifer storage campus is introduced within the framework of geothermal energy development. © 2016 The Author(s). Published by Taylor & Francis

Thermal performance evaluation of a latent heat storage unit for late evening cooking in a solar cooker having three reflectors

Energy Technology Data Exchange (ETDEWEB)

Buddhi, D.; Sharma, A. [Devi Ahilya University, Indore (India). School of Energy and Environmental Studies, Thermal Energy Storage Laboratory; Sharma, S.D. [Mie University, Tsu (Japan). Faculty of Engineering, Department of Architecture

2003-04-01

In this paper, a phase change material (PCM) storage unit for a solar cooker was designed and developed to store energy during sunshine hours. The stored energy was utilised to cook food in the late evening. Commercial grade acetanilide (melting point 118.9 {sup o}C, latent heat of fusion 222 kJ/kg) was used as a latent heat storage material. Evening cooking experiments were conducted with different loads and loading times during the winter season. The experimental results showed that late evening cooking is possible in a solar cooker having three reflectors to enhance the incident solar radiation with the PCM storage unit. (author)

A flexible latent class approach to estimating test-score reliability

NARCIS (Netherlands)

van der Palm, D.W.; van der Ark, L.A.; Sijtsma, K.

2014-01-01

The latent class reliability coefficient (LCRC) is improved by using the divisive latent class model instead of the unrestricted latent class model. This results in the divisive latent class reliability coefficient (DLCRC), which unlike LCRC avoids making subjective decisions about the best solution

Sex Differences in Fluid Reasoning: Manifest and Latent Estimates from the Cognitive Abilities Test

Directory of Open Access Journals (Sweden)

Joni M. Lakin

2014-06-01

Full Text Available The size and nature of sex differences in cognitive ability continues to be a source of controversy. Conflicting findings result from the selection of measures, samples, and methods used to estimate sex differences. Existing sex differences work on the Cognitive Abilities Test (CogAT has analyzed manifest variables, leaving open questions about sex differences in latent narrow cognitive abilities and the underlying broad ability of fluid reasoning (Gf. This study attempted to address these questions. A confirmatory bifactor model was used to estimate Gf and three residual narrow ability factors (verbal, quantitative, and figural. We found that latent mean differences were larger than manifest estimates for all three narrow abilities. However, mean differences in Gf were trivial, consistent with previous research. In estimating group variances, the Gf factor showed substantially greater male variability (around 20% greater. The narrow abilities varied: verbal reasoning showed small variability differences while quantitative and figural showed substantial differences in variance (up to 60% greater. These results add precision and nuance to the study of the variability and masking hypothesis.

Method of flash evaporation and condensation – heat pump for deep cooling of coal-fired power plant flue gas: Latent heat and water recovery

International Nuclear Information System (INIS)

Li, Yuzhong; Yan, Min; Zhang, Liqiang; Chen, Guifang; Cui, Lin; Song, Zhanlong; Chang, Jingcai; Ma, Chunyuan

2016-01-01

Highlights: • A method is developed for deep cooling of flue gas in coal-fired boilers. • The method can recover both latent heat and water from flue gas. • The method utilizes FGD scrubber as a deep cooling exchanger. • The method adopts the direct heat exchange mode to avoid the corrosion problem. - Abstract: Flue gas waste heat recovery and utilization is an efficient means to improve the energy efficiency of coal-fired power plants. At present, the surface corrosion and fouling problems of heat exchanger hinder the development of flue gas deep cooling. In this study, a novel flue gas deep cooling method that can reduce flue gas temperature below the dew point of vapor to recover latent heat and obtain clean water simultaneously is proposed to achieve improved energy efficiency. The heat transfer mode of this method is the direct contact mode, which takes the scrubber, e.g. the flue gas desulfurization (FGD) scrubber, as the deep cooling exchanger. The flash evaporation and condensation (FEC) device and heat pump (HP) are utilized to provide low-temperature medium, such as FGD slurry or water, for washing and deep cooling flue gas, to collect recovered water, and to absorb recovered waste heat. This method is called as the FEC–HP method. This paper elaborated on two optional models of the proposed method. The mechanism for recovering heat and water was also analyzed using the customized flue gas humidity chart, and the method to quantitate recovered heat and water, as well as the results of the case of a 300 MW coal-fired generator set were provided. Net present value calculations showed that this method is profitable in the scenario of burning high-water-content coals. Several potential advantages of this method and suggestions for practical application were also discussed.

Latent-failure risk estimates for computer control

Science.gov (United States)

Dunn, William R.; Folsom, Rolfe A.; Green, Owen R.

1991-01-01

It is shown that critical computer controls employing unmonitored safety circuits are unsafe. Analysis supporting this result leads to two additional, important conclusions: (1) annual maintenance checks of safety circuit function do not, as widely believed, eliminate latent failure risk; (2) safety risk remains even if multiple, series-connected protection circuits are employed. Finally, it is shown analytically that latent failure risk is eliminated when continuous monitoring is employed.

Mixture Item Response Theory-MIMIC Model: Simultaneous Estimation of Differential Item Functioning for Manifest Groups and Latent Classes

Science.gov (United States)

Bilir, Mustafa Kuzey

2009-01-01

This study uses a new psychometric model (mixture item response theory-MIMIC model) that simultaneously estimates differential item functioning (DIF) across manifest groups and latent classes. Current DIF detection methods investigate DIF from only one side, either across manifest groups (e.g., gender, ethnicity, etc.), or across latent classes…

Estimating Evapotranspiration from an Improved Two-Source Energy Balance Model Using ASTER Satellite Imagery

Directory of Open Access Journals (Sweden)

Qifeng Zhuang

2015-11-01

Full Text Available Reliably estimating the turbulent fluxes of latent and sensible heat at the Earth’s surface by remote sensing is important for research on the terrestrial hydrological cycle. This paper presents a practical approach for mapping surface energy fluxes using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER images from an improved two-source energy balance (TSEB model. The original TSEB approach may overestimate latent heat flux under vegetative stress conditions, as has also been reported in recent research. We replaced the Priestley-Taylor equation used in the original TSEB model with one that uses plant moisture and temperature constraints based on the PT-JPL model to obtain a more accurate canopy latent heat flux for model solving. The collected ASTER data and field observations employed in this study are over corn fields in arid regions of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER area, China. The results were validated by measurements from eddy covariance (EC systems, and the surface energy flux estimates of the improved TSEB model are similar to the ground truth. A comparison of the results from the original and improved TSEB models indicates that the improved method more accurately estimates the sensible and latent heat fluxes, generating more precise daily evapotranspiration (ET estimate under vegetative stress conditions.

Equal Area Laws and Latent Heat for d-Dimensional RN-AdS Black Hole

International Nuclear Information System (INIS)

Ma, Meng-Sen; Zhao, Ren; Zhang, Li-Chun; Zhao, Hui-Hua

2014-01-01

We study the equal area laws of d-dimensional RN-AdS black hole. We choose two kinds of phase diagrams, P-V and T-S. We employ the equal area laws to find an isobar which is the real two-phase coexistence line. Our calculation is much simpler to derive the critical value of the thermodynamic quantities. According to the thermodynamic quantities, we also study the latent heat of the black hole

A simple model for local scale sensible and latent heat advection contributions to snowmelt

OpenAIRE

Harder, Phillip; Pomeroy, John W.; Helgason, Warren D.

2018-01-01

Local-scale advection of energy from warm snow-free surfaces to cold snow-covered surfaces is an important component of the energy balance during snowcover depletion. Unfortunately, this process is difficult to quantify in one-dimensional snowmelt models. This manuscript proposes a simple sensible and latent heat advection model for snowmelt situations that can be readily coupled to one-dimensional energy balance snowmelt models. An existing advection parameterization was coupled to a concept...

Application of latent heat storage devices and thermal solar collectors; Einsatz von Latentwaermespeichern und Solarthermie

Energy Technology Data Exchange (ETDEWEB)

Leonhardt, Corinna; Mueller, Dirk [RWTH Aachen, E.ON Energieforschungszentrum, Lehrstuhl fuer Gebaeude- und Raumklimatechnik (Germany)

2010-12-15

Modern heating systems for buildings need a supply temperature of approximately 35 C. In this temperature range it is possible to use low temperature storage systems. Therefore the heat losses over the envelope can be reduced because of the smaller temperature difference between the ambient air and the storage. In order to use the existing technique of the buffer storages more efficiently, latent heat storage devices are put into the storage volume. For the operating temperature range of 30 to 40 C paraffins or salt hydrates can be used. Because of the low operating temperature it is possible to integrate solar thermal systems in the heating system (especially in spring and autumn). The overall system performance will be analysed. (Copyright copyright 2010 Ernst and Sohn Verlag fuer Architektur und technische Wissenschaften GmbH and Co. KG, Berlin)

Estimating Classification Errors Under Edit Restrictions in Composite Survey-Register Data Using Multiple Imputation Latent Class Modelling (MILC

Directory of Open Access Journals (Sweden)

Boeschoten Laura

2017-12-01

Full Text Available Both registers and surveys can contain classification errors. These errors can be estimated by making use of a composite data set. We propose a new method based on latent class modelling to estimate the number of classification errors across several sources while taking into account impossible combinations with scores on other variables. Furthermore, the latent class model, by multiply imputing a new variable, enhances the quality of statistics based on the composite data set. The performance of this method is investigated by a simulation study, which shows that whether or not the method can be applied depends on the entropy R2 of the latent class model and the type of analysis a researcher is planning to do. Finally, the method is applied to public data from Statistics Netherlands.

Spurious Latent Class Problem in the Mixed Rasch Model: A Comparison of Three Maximum Likelihood Estimation Methods under Different Ability Distributions

Science.gov (United States)

Sen, Sedat

2018-01-01

Recent research has shown that over-extraction of latent classes can be observed in the Bayesian estimation of the mixed Rasch model when the distribution of ability is non-normal. This study examined the effect of non-normal ability distributions on the number of latent classes in the mixed Rasch model when estimated with maximum likelihood…

Prevalence Estimation and Validation of New Instruments in Psychiatric Research: An Application of Latent Class Analysis and Sensitivity Analysis

Science.gov (United States)

Pence, Brian Wells; Miller, William C.; Gaynes, Bradley N.

2009-01-01

Prevalence and validation studies rely on imperfect reference standard (RS) diagnostic instruments that can bias prevalence and test characteristic estimates. The authors illustrate 2 methods to account for RS misclassification. Latent class analysis (LCA) combines information from multiple imperfect measures of an unmeasurable latent condition to…

Abstract: Inference and Interval Estimation for Indirect Effects With Latent Variable Models.

Science.gov (United States)

Falk, Carl F; Biesanz, Jeremy C

2011-11-30

Models specifying indirect effects (or mediation) and structural equation modeling are both popular in the social sciences. Yet relatively little research has compared methods that test for indirect effects among latent variables and provided precise estimates of the effectiveness of different methods. This simulation study provides an extensive comparison of methods for constructing confidence intervals and for making inferences about indirect effects with latent variables. We compared the percentile (PC) bootstrap, bias-corrected (BC) bootstrap, bias-corrected accelerated (BC a ) bootstrap, likelihood-based confidence intervals (Neale & Miller, 1997), partial posterior predictive (Biesanz, Falk, and Savalei, 2010), and joint significance tests based on Wald tests or likelihood ratio tests. All models included three reflective latent variables representing the independent, dependent, and mediating variables. The design included the following fully crossed conditions: (a) sample size: 100, 200, and 500; (b) number of indicators per latent variable: 3 versus 5; (c) reliability per set of indicators: .7 versus .9; (d) and 16 different path combinations for the indirect effect (α = 0, .14, .39, or .59; and β = 0, .14, .39, or .59). Simulations were performed using a WestGrid cluster of 1680 3.06GHz Intel Xeon processors running R and OpenMx. Results based on 1,000 replications per cell and 2,000 resamples per bootstrap method indicated that the BC and BC a bootstrap methods have inflated Type I error rates. Likelihood-based confidence intervals and the PC bootstrap emerged as methods that adequately control Type I error and have good coverage rates.

Active heat exchange system development for latent heat thermal energy storage

Science.gov (United States)

Alario, J.; Kosson, R.; Haslett, R.

1980-01-01

Various active heat exchange concepts were identified from among three generic categories: scrapers, agitators/vibrators and slurries. The more practical ones were given a more detailed technical evaluation and an economic comparison with a passive tube-shell design for a reference application (300 MW sub t storage for 6 hours). Two concepts were selected for hardware development: (1) a direct contact heat exchanger in which molten salt droplets are injected into a cooler counterflowing stream of liquid metal carrier fluid, and (2) a rotating drum scraper in which molten salt is sprayed onto the circumference of a rotating drum, which contains the fluid salt is sprayed onto the circumference of a rotating drum, which contains the fluid heat sink in an internal annulus near the surface. A fixed scraper blade removes the solidified salt from the surface which was nickel plated to decrease adhesion forces. In addition to improving performance by providing a nearly constant transfer rate during discharge, these active heat exchanger concepts were estimated to cost at least 25% less than the passive tube-shell design.

The Global Burden of Latent Tuberculosis Infection: A Re-estimation Using Mathematical Modelling.

Directory of Open Access Journals (Sweden)

Rein M G J Houben

2016-10-01

Full Text Available The existing estimate of the global burden of latent TB infection (LTBI as "one-third" of the world population is nearly 20 y old. Given the importance of controlling LTBI as part of the End TB Strategy for eliminating TB by 2050, changes in demography and scientific understanding, and progress in TB control, it is important to re-assess the global burden of LTBI.We constructed trends in annual risk in infection (ARI for countries between 1934 and 2014 using a combination of direct estimates of ARI from LTBI surveys (131 surveys from 1950 to 2011 and indirect estimates of ARI calculated from World Health Organisation (WHO estimates of smear positive TB prevalence from 1990 to 2014. Gaussian process regression was used to generate ARIs for country-years without data and to represent uncertainty. Estimated ARI time-series were applied to the demography in each country to calculate the number and proportions of individuals infected, recently infected (infected within 2 y, and recently infected with isoniazid (INH-resistant strains. Resulting estimates were aggregated by WHO region. We estimated the contribution of existing infections to TB incidence in 2035 and 2050. In 2014, the global burden of LTBI was 23.0% (95% uncertainty interval [UI]: 20.4%-26.4%, amounting to approximately 1.7 billion people. WHO South-East Asia, Western-Pacific, and Africa regions had the highest prevalence and accounted for around 80% of those with LTBI. Prevalence of recent infection was 0.8% (95% UI: 0.7%-0.9% of the global population, amounting to 55.5 (95% UI: 48.2-63.8 million individuals currently at high risk of TB disease, of which 10.9% (95% UI:10.2%-11.8% was isoniazid-resistant. Current LTBI alone, assuming no additional infections from 2015 onwards, would be expected to generate TB incidences in the region of 16.5 per 100,000 per year in 2035 and 8.3 per 100,000 per year in 2050. Limitations included the quantity and methodological heterogeneity of direct ARI

Thermal Analysis of Fluidized Bed and Fixed Bed Latent Heat Thermal Storage System

Science.gov (United States)

Beemkumar, N.; Karthikeyan, A.; Shiva Keshava Reddy, Kota; Rajesh, Kona; Anderson, A.

2017-05-01

Thermal energy storage technology is essential because its stores available energy at low cost. Objective of the work is to store the thermal energy in a most efficient method. This work is deal with thermal analysis of fluidized bed and fixed bed latent heat thermal storage (LHTS) system with different encapsulation materials (aluminium, brass and copper). D-Mannitol has been used as phase change material (PCM). Encapsulation material which is in orbicular shape with 4 inch diameter and 2 mm thickness orbicular shaped product is used. Therminol-66 is used as a heat transfer fluid (HTF). Arrangement of encapsulation material is done in two ways namely fluidized bed and fixed bed thermal storage system. Comparison was made between the performance of fixed bed and fluidized bed with different encapsulation material. It is observed that from the economical point of view aluminium in fluidized bed LHTS System has highest efficiency than copper and brass. The thermal energy storage system can be analyzed with fixed bed by varying mass flow rate of oil paves a way to find effective heat energy transfer.

The Latent Structure of Autistic Traits: A Taxometric, Latent Class and Latent Profile Analysis of the Adult Autism Spectrum Quotient

Science.gov (United States)

James, Richard J.; Dubey, Indu; Smith, Danielle; Ropar, Danielle; Tunney, Richard J.

2016-01-01

Autistic traits are widely thought to operate along a continuum. A taxometric analysis of Adult Autism Spectrum Quotient data was conducted to test this assumption, finding little support but identifying a high severity taxon. To understand this further, latent class and latent profile models were estimated that indicated the presence of six…

Numerical performance study of paraffin wax dispersed with alumina in a concentric pipe latent heat storage system

Directory of Open Access Journals (Sweden)

Valan Arasu Amirtham

2013-01-01

Full Text Available Latent heat energy storage systems using paraffin wax could have lower heat transfer rates during melting/freezing processes due to its inherent low thermal conductivity. The thermal conductivity of paraffin wax can be enhanced by employing high conductivity materials such as alumina (Al2O3. A numerical analysis has been carried out to study the performance enhancement of paraffin wax with nanoalumina (Al2O3 particles in comparison with simple paraffin wax in a concentric double pipe heat exchanger. Numerical analysis indicates that the charge-discharge rates of thermal energy can be greatly enhanced using paraffin wax with alumina as compared with a simple paraffin wax as PCM.

Exploitation of humid air latent heat by means of solar assisted heat pumps operating below the dew point

International Nuclear Information System (INIS)

Scarpa, Federico; Tagliafico, Luca A.

2016-01-01

Highlights: • The opportunity of humid air latent heat exploitation by DX-SAHP is investigated. • A set of experimental tests confirms this opportunity and quantifies it as relevant. • A parametric analysis is performed, via simulation, to deepen the subject. • The energy gain is relevant during both night and daytime. - Abstract: Nowadays, the exploitation of environmental exergy resources for heating purposes (solar energy, convection heat transfer from ambient air, moist air humidity condensation) by means of properly designed heat pump systems is a possible opportunity. In particular, the use of direct expansion solar assisted heat pumps (DX-SAHP) is investigated in this study, when a bare external plate (the solar collector) is kept at temperatures lower than the dew point temperature of ambient air, so that condensation takes place on it. The potential of this technology is settled and an instrumented prototype of a small DX-SAHP system is used to verify the actual performance of the system, in terms of specific thermal energy delivered to the user, efficiency and regulation capabilities. Results clearly show that the contribution of the condensation is significant (20%–30% of the total harvested energy) overnight or in cloudy days with very low or no solar irradiation, and must be taken into account in a system model devoted to describe the DX-SAHP behavior. During daytime, the percentage gain decreases but is still consistent. By investigating along these lines, the heat due to condensation harvested by the collector is found to be a function of the dew-point temperature alone.

Response surface method optimization of V-shaped fin assisted latent heat thermal energy storage system during discharging process

Directory of Open Access Journals (Sweden)

Sina Lohrasbi

2016-09-01

Full Text Available Latent Heat Thermal Energy Storage Systems (LHTESS containing Phase Change Material (PCM are used to establish balance between energy supply and demand. PCMs have high latent heat but low thermal conductivity, which affects their heat transfer performance. In this paper, a novel fin array has been optimized by multi-objective Response Surface Method (RSM based on discharging process of PCM, and then this fin configuration is applied on LHTESS, and comparison between full discharging time by applying this fin array and LHTESS with other fin structures has been carried out. The employed numerical method in this paper is Standard Galerkin Finite Element Method. Adaptive grid refinement is used to solve the equations. Since the enhancement technique, which has been employed in the present study reduces the employed PCM mass, maximum energy storage capacity variations have been considered. Therefore phase change expedition and maximum energy storage capacity have been considered as the objectives of optimization and the importance of second objective is indicated which is proposed as the novelty here. Results indicate that considering maximum energy storage capacity as the objective of optimization procedure leads to efficient shape design of LHTESS. Also employing optimized V-shaped fin in LHTESS, expedites discharging process considerably in comparison with the LHTESS without fin.

Fitting Latent Cluster Models for Networks with latentnet

Directory of Open Access Journals (Sweden)

Pavel N. Krivitsky

2007-12-01

Full Text Available latentnet is a package to fit and evaluate statistical latent position and cluster models for networks. Hoff, Raftery, and Handcock (2002 suggested an approach to modeling networks based on positing the existence of an latent space of characteristics of the actors. Relationships form as a function of distances between these characteristics as well as functions of observed dyadic level covariates. In latentnet social distances are represented in a Euclidean space. It also includes a variant of the extension of the latent position model to allow for clustering of the positions developed in Handcock, Raftery, and Tantrum (2007.The package implements Bayesian inference for the models based on an Markov chain Monte Carlo algorithm. It can also compute maximum likelihood estimates for the latent position model and a two-stage maximum likelihood method for the latent position cluster model. For latent position cluster models, the package provides a Bayesian way of assessing how many groups there are, and thus whether or not there is any clustering (since if the preferred number of groups is 1, there is little evidence for clustering. It also estimates which cluster each actor belongs to. These estimates are probabilistic, and provide the probability of each actor belonging to each cluster. It computes four types of point estimates for the coefficients and positions: maximum likelihood estimate, posterior mean, posterior mode and the estimator which minimizes Kullback-Leibler divergence from the posterior. You can assess the goodness-of-fit of the model via posterior predictive checks. It has a function to simulate networks from a latent position or latent position cluster model.

Retrieving latent heating vertical structure from cloud and precipitation profiles—Part II: Deep convective and stratiform rain processes

International Nuclear Information System (INIS)

Li, Rui; Min, Qilong; Wu, Xiaoqing; Fu, Yunfei

2013-01-01

An exploratory study on physical based latent heat (LH) retrieval algorithm is conducted by parameterizing the physical linkages between observed cloud and precipitation profiles to the major processes of phase change of atmospheric water. Specifically, rain is segregated into three rain types: warm, convective, and stratiform rain, based on their dynamical and thermodynamical characteristics. As the second of series, both convective and stratiform rain LH algorithms are presented and evaluated here. For convective and stratiform rain, the major LH-related microphysical processes including condensation, deposition, evaporation, sublimation, and freezing–melting are parameterized with the aid of Cloud Resolving Model (CRM) simulations. The condensation and deposition processes are parameterized in terms of rain formation processes through the precipitation formation theory. LH associated with the freezing–melting process is relatively small and is assumed to be a fraction of total condensation and deposition LH. The evaporation and sublimation processes are parameterized for three unsaturated scenarios: rain out of the cloud body, clouds at cloud boundary and clouds and rain in downdraft region. The evaluation or self-consistency test indicates the retrievals capture the major features of LH profiles and reproduce the double peaks at right altitudes. The LH products are applicable at various stages of cloud system life cycle for high-resolution models, as well as for large-scale climate models. -- Highlights: ► An exploratory study on physics-based cold rain latent heat retrieval algorithm. ► Utilize the full information of the vertical structures of cloud and rainfall. ► Include all major LH-related microphysical processes (in ice and liquid phase). ► Directly link water mass measurements to latent heat at instantaneous pixel level. ► Applicable at various stages of cloud system life cycle

Utilization of the PCM latent heat for energy savings in buildings

Science.gov (United States)

Fořt, Jan; Trník, Anton; Pavlík, Zbyšek

2017-07-01

Increase of the energy consumption for buildings operation creates a great challenge for sustainable development issues. Thermal energy storage systems present promising way to achieve this goal. The latent heat storage systems with high density of thermal storage via utilization of phase change materials (PCMs) enable to improve thermal comfort of buildings and reduce daily temperature fluctuations of interior climate. The presented study is focused on the evaluation of the effect of PCM admixture on thermal performance of a cement-lime plaster. On the basis of the experimentally accessed properties of newly developed plasters, computational modeling is carried out in order to rate the acquired thermal improvement. The calculated results show that incorporation of 24 mass% of paraffinic wax based PCM decreased the energy demand of approx. 14.6%.

On the use of radiative surface temperature to estimate sensible heat flux over sparse shrubs in Nevada

Science.gov (United States)

Chehbouni, A.; Nichols, W. D.; Qi, J.; Njoku, E. G.; Kerr, Y. H.; Cabot, F.

1994-01-01

The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

Estimating Classification Errors under Edit Restrictions in Composite Survey-Register Data Using Multiple Imputation Latent Class Modelling (MILC)

NARCIS (Netherlands)

Boeschoten, Laura; Oberski, Daniel; De Waal, Ton

2017-01-01

Both registers and surveys can contain classification errors. These errors can be estimated by making use of a composite data set. We propose a new method based on latent class modelling to estimate the number of classification errors across several sources while taking into account impossible

Experimental process investigation of a latent heat energy storage system with a staggered heat exchanger with different phase change materials for solar thermal energy storage applications

Directory of Open Access Journals (Sweden)

Tsolakoglou Nikolas P.

2017-01-01

Full Text Available This work investigates melting and solidification processes of four different Phase Change Materials (PCM used as latent heat thermal storage system. The experimental rig was consisted of an insulated tank, filled with the under investigation PCM, a staggered heat exchanger to supply or extract heat from the PCM cavity and a water pump to circulate Heat Transfer Fluid (HTF. Both charging (melting and discharging (solidification processes were conducted for two different HTF flow rates. The main scope of this work was to develop a first approach and to investigate the behaviour of PCM under various load conditions (different HTF flow rates. Results show that different HTF flow rates affect melting and solidification time periods; in both processes time was reduced while HTF flow rate was increased but in differentways due to the transition from conduction to convection heat transfer mechanisms.

Experimental process investigation of a latent heat energy storage system with a staggered heat exchanger with different phase change materials for solar thermal energy storage applications

Science.gov (United States)

Tsolakoglou, Nikolas P.; Koukou, Maria K.; Vrachopoulos, Michalis Gr.; Tachos, Nikolaos; Lymberis, Kostas; Stathopoulos, Vassilis

2017-11-01

This work investigates melting and solidification processes of four different Phase Change Materials (PCM) used as latent heat thermal storage system. The experimental rig was consisted of an insulated tank, filled with the under investigation PCM, a staggered heat exchanger to supply or extract heat from the PCM cavity and a water pump to circulate Heat Transfer Fluid (HTF). Both charging (melting) and discharging (solidification) processes were conducted for two different HTF flow rates. The main scope of this work was to develop a first approach and to investigate the behaviour of PCM under various load conditions (different HTF flow rates). Results show that different HTF flow rates affect melting and solidification time periods; in both processes time was reduced while HTF flow rate was increased but in differentways due to the transition from conduction to convection heat transfer mechanisms.

Energy and exergy analyses of medium temperature latent heat thermal storage with high porosity metal matrix

International Nuclear Information System (INIS)

Kumar, Ashish; Saha, Sandip K.

2016-01-01

Graphical abstract: I. Metal matrix is used as the thermal conductivity enhancers (TCE) in PCM-based TES. II. Time evolution second law analysis is evaluated for different porosities and pore diameters. III. Reduction in fluctuation in HTF temperature is significantly affected by the change in porosity (ε) shown in figure. IV. Maximum energy and exergy efficiencies are obtained for porosity of 0.85. V. Effect of pore diameter on first law and second law efficiencies is found to be marginal. - Abstract: Thermal energy storage system in a concentrating solar plant (CSP) reduces the gap between energy demand and supply caused by the intermittent behaviour of solar radiation. In this paper, detailed exergy and energy analyses of shell and tube type latent heat thermal storage system (LHTES) for medium temperature solar thermal power plant (∼200 °C) are performed to estimate the net useful energy during the charging and discharging period in a cycle. A commercial-grade organic phase change material (PCM) is stored inside the annular space of the shell and the heat transfer fluid (HTF) flows through the tubes. Thermal conductivity enhancer (TCE) in the form of metal matrix is embedded in PCM to augment heat transfer. A numerical model is developed to investigate the fluid flow and heat transfer characteristics using the momentum equation and the two-temperature non-equilibrium energy equation coupled with the enthalpy method to account for phase change in PCM. The effects of storage material, porosity and pore-diameter on the net useful energy that can be stored and released during a cycle, are studied. It is found that the first law efficiency of sensible heat storage system is less compared to LHTES. With the decrease in porosity, the first law and second law efficiencies of LHTES increase for both the charging and discharging period. There is no significant variation in energy and exergy efficiencies with the change in pore-diameter of the metal matrix.

Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling

International Nuclear Information System (INIS)

Efimova, Anastasia; Pinnau, Sebastian; Mischke, Matthias; Breitkopf, Cornelia; Ruck, Michael; Schmidt, Peer

2014-01-01

Graphical abstract: - Highlights: • Inorganic salt hydrates. • Latent heat thermal energy storage. • Thermal behavior of melting and crystallization. • Cycling stability. • Nucleation. - Abstract: Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 °C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO 3 ) 2 ·6H 2 O, Mn(NO 3 ) 2 ·4H 2 O, and KNO 3 with the melting temperature range 18–21 °C and the enthalpy of fusion of about 110 kJ kg −1 . Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation

Feasibility of Storing Latent Heat with Liquid Crystals. Proof of Concept at Lab Scale

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Rocío Bayón

2016-04-01

Full Text Available In this work, the first experimental results of thermotropic liquid crystals used as phase change materials for thermal storage are presented. For that purpose, the n = 10 derivative from the family of 4′-n-alkoxybiphenyl-4-carboxylic acids has been prepared. Different techniques like polarized-light microscopy, differential scanning calorimetry, thermogravimetric analysis and rheological measurements have been applied for its characterization. Having a mesophase/isotropic transition temperature around 251 °C, a clearing enthalpy of 55 kJ/kg, a thermal heat capacity of around 2.4 kJ/kg and a dynamic viscosity lower than 0.6 Pas, this compound fulfills the main requirements for being considered as latent heat storage material. Although further studies on thermal stability are necessary, the results already obtained are both promising and encouraging since they demonstrate de viability of this new application of liquid crystals as thermal storage media.

Preparation and thermal properties of form-stable palmitic acid/active aluminum oxide composites as phase change materials for latent heat storage

International Nuclear Information System (INIS)

Fang, Guiyin; Li, Hui; Cao, Lei; Shan, Feng

2012-01-01

Form-stable palmitic acid (PA)/active aluminum oxide composites as phase change materials were prepared by adsorbing liquid palmitic acid into active aluminum oxide. In the composites, the palmitic acid was used as latent heat storage materials, and the active aluminum oxide was used as supporting material. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine the chemical structure, crystalloid phase and microstructure of the composites, respectively. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetry analyzer (TGA). The FT-IR analyses results indicated that there is no chemical interaction between the palmitic acid and active aluminum oxide. The SEM results showed that the palmitic acid was well adsorbed into porous network of the active aluminum oxide. The DSC results indicated that the composites melt at 60.25 °C with a latent heat of 84.48 kJ kg −1 and solidify at 56.86 °C with a latent heat of 78.79 kJ kg −1 when the mass ratio of the PA to active aluminum oxide is 0.9:1. Compared with that of the PA, the melting and solidifying time of the composites CPCM5 was reduced by 20.6% and 21.4% because of the increased heat transfer rate through EG addition. The TGA results showed that the active aluminum oxide can improve the thermal stability of the composites. -- Highlights: ► Form-stable PA/active aluminum oxide composites as PCMs were prepared. ► Chemical structure, crystalloid phase and microstructure of composites were determined. ► Thermal properties and thermal stability of the composites were investigated. ► Expanded graphite can improve thermal conductivity of the composites.

Durability of a fin-tube latent heat storage using high density polyethylene as PCM

Science.gov (United States)

Zauner, Christoph; Hengstberger, Florian; Etzel, Mark; Lager, Daniel; Hofmann, Rene; Walter, Heimo

2017-10-01

Polymers have rarely been used as storage materials in latent heat storages up to now. Thus, we systematically screened all polymers available on a large-scale, selected promising ones based on their theoretical properties and experimentally tested more than 50 candidates. We found that polyethylene, polyoxymethylene and polyamides are promising even as recycled material. Especially high density polyethylene (HDPE) turned out to be suitable as was shown by detailed thermophysical characterization including more than 1000 heating and cooling cycles for INEOS Rigidex HD6070EA. We built a storage with 170 kg HDPE and a total mass of 600 kg based on a fin-tube heat exchanger and characterized its energy capacity, power characteristics and temperature profiles using a thermal oil test rig. In total we performed 30 melting and crystallization cycles where the whole storage was above 100 °C for more than 140 hours. After usage we examined the interior of the storage by cutting it into various pieces. A thin layer of degradation was observed on the surfaces of the PCM which is most likely related to thermo-oxidative degeneration of HDPE. However, the bulk of the PCM is still intact as well as the heat exchanger itself.

Assessment and simulation of global terrestrial latent heat flux by synthesis of CMIP5 climate models and surface eddy covariance observations

Science.gov (United States)

Yunjun Yao; Shunlin Liang; Xianglan Li; Shaomin Liu; Jiquan Chen; Xiaotong Zhang; Kun Jia; Bo Jiang; Xianhong Xie; Simon Munier; Meng Liu; Jian Yu; Anders Lindroth; Andrej Varlagin; Antonio Raschi; Asko Noormets; Casimiro Pio; Georg Wohlfahrt; Ge Sun; Jean-Christophe Domec; Leonardo Montagnani; Magnus Lund; Moors Eddy; Peter D. Blanken; Thomas Grunwald; Sebastian Wolf; Vincenzo Magliulo

2016-01-01

The latent heat flux (LE) between the terrestrial biosphere and atmosphere is a major driver of the globalhydrological cycle. In this study, we evaluated LE simulations by 45 general circulation models (GCMs)in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by a comparison...

Preparation of fine powdered composite for latent heat storage

Energy Technology Data Exchange (ETDEWEB)

Fořt, Jan, E-mail: jan.fort.1@fsv.cvut.cz; Trník, Anton, E-mail: anton.trnik@fsv.cvut.cz; Pavlíková, Milena, E-mail: milena.pavlikova@fsv.cvut.cz; Pavlík, Zbyšek, E-mail: pavlikz@fsv.cvut.cz [Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague (Czech Republic); Pomaleski, Marina, E-mail: marina-pomaleski@fsv.cvut.cz [Faculty of Civil Engineering, Architecture and Urbanism, University of Campinas, R. Saturnino de Brito 224, 13083-889 Campinas – SP (Brazil)

2016-07-07

Application of latent heat storage building envelope systems using phase-change materials represents an attractive method of storing thermal energy and has the advantages of high-energy storage density and the isothermal nature of the storage process. This study deals with a preparation of a new type of powdered phase change composite material for thermal energy storage. The idea of a composite is based upon the impregnation of a natural silicate material by a reasonably priced commercially produced pure phase change material and forming the homogenous composite powdered structure. For the preparation of the composite, vacuum impregnation method is used. The particle size distribution accessed by the laser diffraction apparatus proves that incorporation of the organic phase change material into the structure of inorganic siliceous pozzolana does not lead to the clustering of the particles. The compatibility of the prepared composite is characterized by the Fourier transformation infrared analysis (FTIR). Performed DSC analysis shows potential of the developed composite for thermal energy storage that can be easily incorporated into the cement-based matrix of building materials. Based on the obtained results, application of the developed phase change composite can be considered with a great promise.

Effects of Initial Values and Convergence Criterion in the Two-Parameter Logistic Model When Estimating the Latent Distribution in BILOG-MG 3.

Directory of Open Access Journals (Sweden)

Ingo W Nader

Full Text Available Parameters of the two-parameter logistic model are generally estimated via the expectation-maximization algorithm, which improves initial values for all parameters iteratively until convergence is reached. Effects of initial values are rarely discussed in item response theory (IRT, but initial values were recently found to affect item parameters when estimating the latent distribution with full non-parametric maximum likelihood. However, this method is rarely used in practice. Hence, the present study investigated effects of initial values on item parameter bias and on recovery of item characteristic curves in BILOG-MG 3, a widely used IRT software package. Results showed notable effects of initial values on item parameters. For tighter convergence criteria, effects of initial values decreased, but item parameter bias increased, and the recovery of the latent distribution worsened. For practical application, it is advised to use the BILOG default convergence criterion with appropriate initial values when estimating the latent distribution from data.

Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling

Energy Technology Data Exchange (ETDEWEB)

Efimova, Anastasia [Brandenburgische Technische Universität (BTU) Cottbus – Senftenberg, Chair of Inorganic Chemistry, Großenhainer Str. 57, 01968 Senftenberg (Germany); Pinnau, Sebastian; Mischke, Matthias; Breitkopf, Cornelia [Technische Universität Dresden, Chair of Technical Thermodynamics, Helmholtzstr. 14, 01069 Dresden (Germany); Ruck, Michael [Technische Universität Dresden, Chair of Inorganic Chemistry, Bergstr. 66, 01062 Dresden (Germany); Schmidt, Peer, E-mail: peer.schmidt@hs-lausitz.de [Brandenburgische Technische Universität (BTU) Cottbus – Senftenberg, Chair of Inorganic Chemistry, Großenhainer Str. 57, 01968 Senftenberg (Germany)

2014-01-10

Graphical abstract: - Highlights: • Inorganic salt hydrates. • Latent heat thermal energy storage. • Thermal behavior of melting and crystallization. • Cycling stability. • Nucleation. - Abstract: Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 °C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO{sub 3}){sub 2}·6H{sub 2}O, Mn(NO{sub 3}){sub 2}·4H{sub 2}O, and KNO{sub 3} with the melting temperature range 18–21 °C and the enthalpy of fusion of about 110 kJ kg{sup −1}. Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation.

Latent palmprint matching.

Science.gov (United States)

Jain, Anil K; Feng, Jianjiang

2009-06-01

The evidential value of palmprints in forensic applications is clear as about 30 percent of the latents recovered from crime scenes are from palms. While biometric systems for palmprint-based personal authentication in access control type of applications have been developed, they mostly deal with low-resolution (about 100 ppi) palmprints and only perform full-to-full palmprint matching. We propose a latent-to-full palmprint matching system that is needed in forensic applications. Our system deals with palmprints captured at 500 ppi (the current standard in forensic applications) or higher resolution and uses minutiae as features to be compatible with the methodology used by latent experts. Latent palmprint matching is a challenging problem because latent prints lifted at crime scenes are of poor image quality, cover only a small area of the palm, and have a complex background. Other difficulties include a large number of minutiae in full prints (about 10 times as many as fingerprints), and the presence of many creases in latents and full prints. A robust algorithm to reliably estimate the local ridge direction and frequency in palmprints is developed. This facilitates the extraction of ridge and minutiae features even in poor quality palmprints. A fixed-length minutia descriptor, MinutiaCode, is utilized to capture distinctive information around each minutia and an alignment-based minutiae matching algorithm is used to match two palmprints. Two sets of partial palmprints (150 live-scan partial palmprints and 100 latent palmprints) are matched to a background database of 10,200 full palmprints to test the proposed system. Despite the inherent difficulty of latent-to-full palmprint matching, rank-1 recognition rates of 78.7 and 69 percent, respectively, were achieved in searching live-scan partial palmprints and latent palmprints against the background database.

poLCA: An R Package for Polytomous Variable Latent Class Analysis

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Drew A. Linzer

2011-08-01

Full Text Available poLCA is a software package for the estimation of latent class and latent class regression models for polytomous outcome variables, implemented in the R statistical computing environment. Both models can be called using a single simple command line. The basic latent class model is a finite mixture model in which the component distributions are assumed to be multi-way cross-classification tables with all variables mutually independent. The latent class regression model further enables the researcher to estimate the effects of covariates on predicting latent class membership. poLCA uses expectation-maximization and Newton-Raphson algorithms to find maximum likelihood estimates of the model parameters.

Study of the thermal properties of selected PCMs for latent heat storage in buildings

Science.gov (United States)

Valentova, Katerina; Pechackova, Katerina; Prikryl, Radek; Ostry, Milan; Zmeskal, Oldrich

2017-07-01

The paper is focused on measurements of thermal properties of selected phase change materials (PCMs) which can be used for latent heat storage in building structures. The thermal properties were measured by the transient step-wise method and analyzed by the thermal spectroscopy. The results of three different materials (RT18HC, RT28HC, and RT35HC) and their thermal properties in solid, liquid, and phase change region were determined. They were correlated with the differential scanning calorimetry (DSC) measurement. The results will be used to determine the optimum ratio of components for the construction of drywall and plasters containing listed ingredients, respectively.

Novel functional materials from renewable lipids: Amphiphilic antimicrobial polymers and latent heat thermal energy storage

Science.gov (United States)

Floros, Michael Christopher

Vegetable oils represent an ideal and renewable feedstock for the synthesis of a variety of functional materials. However, without financial incentive or unique applications motivating a switch, commercial products continue to be manufactured from petrochemical resources. Two different families of high value, functional materials synthesized from vegetable oils were studied. These materials demonstrate superior and unique performance to comparable petrochemical analogues currently on the market. In the first approach, 3 amphiphilic thermoplastic polytriazoles with differing lipophilic segment lengths were synthesized in a polymerization process without solvents or catalysts. Investigation of monomer structure influence on the resultant functional behaviour of these polymers found distinctive odd/even behaviour reliant on the number of carbon atoms in the monomers. Higher concentrations of triazole groups, due to shorter CH2 chains in the monomeric dialkynes, resulted in more brittle polymers, displaying higher tensile strengths but reduced elongation to break characteristics. These polymers had similar properties to commercial petroleum derived thermoplastics. One polymer demonstrated self-assembled surface microstructuring, and displayed hydrophobic properties. Antimicrobial efficacy of the polymers were tested by applying concentrated bacterial solutions to the surfaces, and near complete inhibition was demonstrated after 4 hours. Scanning electron microscope images of killed bacteria showed extensive membrane damage, consistent with the observed impact of other amphiphilic compounds in literature. These polytriazoles are suited for applications in medical devices and implants, where major concerns over antibiotic resistance are prevalent. In the second approach, a series of symmetric, saturated diester phase change materials (PCMs) were also synthesized with superior latent heat values compared to commercial petrochemical analogues. These diesters exhibit

Using Nanoparticles for Enhance Thermal Conductivity of Latent Heat Thermal Energy Storage

Directory of Open Access Journals (Sweden)

Baydaa Jaber Nabhan

2015-06-01

Full Text Available Phase change materials (PCMs such as paraffin wax can be used to store or release large amount of energy at certain temperature at which their solid-liquid phase changes occurs. Paraffin wax that used in latent heat thermal energy storage (LHTES has low thermal conductivity. In this study, the thermal conductivity of paraffin wax has been enhanced by adding different mass concentration (1wt.%, 3wt.%, 5wt.% of (TiO2 nano-particles with about (10nm diameter. It is found that the phase change temperature varies with adding (TiO2 nanoparticles in to the paraffin wax. The thermal conductivity of the composites is found to decrease with increasing temperature. The increase in thermal conductivity has been found to increase by about (10% at nanoparticles loading (5wt.% and 15oC.

A Comparison of the Box Type Two Solar Cookers with Latent Heat Storage

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Numan YÜKSEL

2013-04-01

Full Text Available In this study, the use potential of solar cookers storing by latent heat technical of solar energy was experimentally researched and these cookers were compared. For this purpose, the temperatures of the cookers’ phase change material (PCM were continuously measured during the day, both during sun and after sunset, by filling with the phase change material around the solar cooker manufactured. From the measurements, while the temperature of the PCM in the big cooker filled the large amount of PCM is 92,8 °C, the temperature of the PCM in the other cooker is 80,4 °C.However, the better performance is reached by the cooker-1 in which the maximum surface temperature during the day is 111 °C and the heat is preserved to 52 °C until the next morning. Also, the surface temperature in the cooker is reached to the temperature of 85 °C at the end of 1 hour. It is obtained that the utilization rate or efficiency of the solar cooker-1 is % 36,89 and that of the other cooker is %30,10. It is seen that the solar cookers should be designed for the purpose, depending on the amount of PCM and the cooker’s size. It is concluded that the solar cooker designed can be effectively used with the different purposes, such as heating-cooking, on 24 hours a day, an important part of the year without the need for the other heat source

Enhanced Thermal Properties of Novel Latent Heat Thermal Storage Material Through Confinement of Stearic Acid in Meso-Structured Onion-Like Silica

Science.gov (United States)

Gao, Junkai; Lv, Mengjiao; Lu, Jinshu; Chen, Yan; Zhang, Zijun; Zhang, Xiongjie; Zhu, Yingying

2017-12-01

Meso-structured onion-like silica (MOS), which had a highly ordered, onion-like multilayer; large surface area and pore volume; and highly curved mesopores, were synthesized as a support for stearic acid (SA) to develop a novel shape-stabilized phase change material (SA/MOS). The characterizations of SA/MOS were studied by the analysis technique of scanning electron microscope, infrared spectroscopy, x-ray diffraction, differential scanning calorimeter (DSC), and thermal gravimetry analysis (TGA). The results showed that the interaction between the SA and the MOS was physical adsorption and that the MOS had no effect on the crystal structure of the SA. The DSC results suggested that the melting and solidifying temperature of the SA/MOS were 72.7°C and 63.9°C with a melting latent heat of 108.0 J/g and a solidifying latent heat of 126.0 J/g, respectively, and the TGA results indicated that the SA/MOS had a good thermal stability. All of the results demonstrated that the SA/MOS was a promising thermal energy storage material candidate for practical applications.

Visualizing Confidence Bands for Semiparametrically Estimated Nonlinear Relations among Latent Variables

Science.gov (United States)

Pek, Jolynn; Chalmers, R. Philip; Kok, Bethany E.; Losardo, Diane

2015-01-01

Structural equation mixture models (SEMMs), when applied as a semiparametric model (SPM), can adequately recover potentially nonlinear latent relationships without their specification. This SPM is useful for exploratory analysis when the form of the latent regression is unknown. The purpose of this article is to help users familiar with structural…

Solar Thermoelectricity via Advanced Latent Heat Storage: A Cost-Effective Small-Scale CSP Application

Energy Technology Data Exchange (ETDEWEB)

Glatzmaier, Greg C.; Rea, J.; Olsen, Michele L.; Oshman, C.; Hardin, C.; Alleman, Jeff; Sharp, J.; Weigand, R.; Campo, D.; Hoeschele, G.; Parilla, Philip A.; Siegel, N. P.; Toberer, Eric S.; Ginley, David S.

2017-06-27

We are developing a novel concentrating solar electricity-generating technology that is both modular and dispatchable. Solar ThermoElectricity via Advanced Latent heat Storage (STEALS) uses concentrated solar flux to generate high-temperature thermal energy, which directly converts to electricity via thermoelectric generators (TEGs), stored within a phase-change material (PCM) for electricity generation at a later time, or both allowing for simultaneous charging of the PCM and electricity generation. STEALS has inherent features that drive its cost-competitive scale to be much smaller than current commercial concentrating solar power (CSP) plants. Most obvious is modularity of the solid-state TEG, which favors smaller scales in the kilowatt range as compared to CSP steam turbines, which are minimally 50 MWe for commercial power plants. Here, we present techno-economic and market analyses that show STEALS can be a cost-effective electricity-generating technology with particular appeal to small-scale microgrid applications. We evaluated levelized cost of energy (LCOE) for STEALS and for a comparable photovoltaic (PV) system with battery storage. For STEALS, we estimated capital costs and the LCOE as functions of the type of PCM including the use of recycled aluminum alloys, and evaluated the cost tradeoffs between plasma spray coatings and solution-based boron coatings that are applied to the wetted surfaces of the PCM subsystem. We developed a probabilistic cost model that accounts for uncertainties in the cost and performance inputs to the LCOE estimation. Our probabilistic model estimated LCOE for a 100-kWe STEALS system that had 5 hours of thermal storage and 8-10 hours of total daily power generation. For these cases, the solar multiple for the heliostat field varied between 1.12 and 1.5. We identified microgrids as a likely market for the STEALS system. We characterized microgrid markets in terms of nominal power, dispatchability, geographic location, and

Solar thermoelectricity via advanced latent heat storage: A cost-effective small-scale CSP application

Science.gov (United States)

Glatzmaier, G. C.; Rea, J.; Olsen, M. L.; Oshman, C.; Hardin, C.; Alleman, J.; Sharp, J.; Weigand, R.; Campo, D.; Hoeschele, G.; Parilla, P. A.; Siegel, N. P.; Toberer, E. S.; Ginley, D. S.

2017-06-01

We are developing a novel concentrating solar electricity-generating technology that is both modular and dispatchable. Solar ThermoElectricity via Advanced Latent heat Storage (STEALS) uses concentrated solar flux to generate high-temperature thermal energy, which directly converts to electricity via thermoelectric generators (TEGs), stored within a phase-change material (PCM) for electricity generation at a later time, or both allowing for simultaneous charging of the PCM and electricity generation. STEALS has inherent features that drive its cost-competitive scale to be much smaller than current commercial concentrating solar power (CSP) plants. Most obvious is modularity of the solid-state TEG, which favors smaller scales in the kilowatt range as compared to CSP steam turbines, which are minimally 50 MWe for commercial power plants. Here, we present techno-economic and market analyses that show STEALS can be a cost-effective electricity-generating technology with particular appeal to small-scale microgrid applications. We evaluated levelized cost of energy (LCOE) for STEALS and for a comparable photovoltaic (PV) system with battery storage. For STEALS, we estimated capital costs and the LCOE as functions of the type of PCM including the use of recycled aluminum alloys, and evaluated the cost tradeoffs between plasma spray coatings and solution-based boron coatings that are applied to the wetted surfaces of the PCM subsystem. We developed a probabilistic cost model that accounts for uncertainties in the cost and performance inputs to the LCOE estimation. Our probabilistic model estimated LCOE for a 100-kWe STEALS system that had 5 hours of thermal storage and 8-10 hours of total daily power generation. For these cases, the solar multiple for the heliostat field varied between 1.12 and 1.5. We identified microgrids as a likely market for the STEALS system. We characterized microgrid markets in terms of nominal power, dispatchability, geographic location, and

Heat storage in forest biomass improves energy balance closure

Science.gov (United States)

Lindroth, A.; Mölder, M.; Lagergren, F.

2010-01-01

Temperature measurements in trunks and branches in a mature ca. 100 years-old mixed pine and spruce forest in central Sweden were used to estimate the heat storage in the tree biomass. The estimated heat flux in the sample trees and data on biomass distributions were used to scale up to stand level biomass heat fluxes. The rate of change of sensible and latent heat storage in the air layer below the level of the flux measurements was estimated from air temperature and humidity profile measurements and soil heat flux was estimated from heat flux plates and soil temperature measurements. The fluxes of sensible and latent heat from the forest were measured with an eddy covariance system in a tower. The analysis was made for a two-month period in summer of 1995. The tree biomass heat flux was the largest of the estimated storage components and varied between 40 and -35 W m-2 on summer days with nice weather. Averaged over two months the diurnal maximum of total heat storage was 45 W m-2 and the minimum was -35 W m-2. The soil heat flux and the sensible heat storage in air were out of phase with the biomass flux and they reached maximum values that were about 75% of the maximum of the tree biomass heat storage. The energy balance closure improved significantly when the total heat storage was added to the turbulent fluxes. The slope of a regression line with sum of fluxes and storage as independent and net radiation as dependent variable, increased from 0.86 to 0.95 for half-hourly data and the scatter was also reduced. The most significant finding was, however, that during nights with strongly stable conditions when the sensible heat flux dropped to nearly zero, the total storage matched the net radiation very well. Another interesting result was that the mean energy imbalance started to increase when the Richardson number became more negative than ca. -0.1. In fact, the largest energy deficit occurred at maximum instability. Our conclusion is that eddy covariance

Scale aggregation - comparison of flux estimates from NOPEX

DEFF Research Database (Denmark)

Gottschalk, L.; Batchvarova, E.; Gryning, Sven-Erik

1999-01-01

The NOPEX two concentrated field efforts (CFEs) (June 1994 and April-July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes of latent and sensible heat, but these flux...

Estimating heat-to-heat variation from a statistician's point of view

International Nuclear Information System (INIS)

Hebble, T.L.

1976-01-01

Heat-to-heat variability is the change in results that occurs when the same tests under the same conditions are applied to samples from different heats of the same material. Heat-to-heat variability reflects, among other things, difference in chemistry and in processing history. Published Japanese tensile and creep tests on types 304 and 316 stainless steel tube are used to illustrate the analysis of variance technique as a tool for isolating heat-to-heat variation. The importance of the underlying model and the role of replication are indicated. Finally, confidence intervals and tolerance limits are computed from numerical estimates of heat-to-heat variation. 17 tables

Performance modeling and techno-economic analysis of a modular concentrated solar power tower with latent heat storage

Energy Technology Data Exchange (ETDEWEB)

Rea, Jonathan E.; Oshman, Christopher J.; Olsen, Michele L.; Hardin, Corey L.; Glatzmaier, Greg C.; Siegel, Nathan P.; Parilla, Philip A.; Ginley, David S.; Toberer, Eric S.

2018-05-01

In this paper, we present performance simulations and techno-economic analysis of a modular dispatchable solar power tower. Using a heliostat field and power block three orders of magnitude smaller than conventional solar power towers, our unique configuration locates thermal storage and a power block directly on a tower receiver. To make the system dispatchable, a valved thermosyphon controls heat flow from a latent heat thermal storage tank to a Stirling engine. The modular design results in minimal balance of system costs and enables high deployment rates with a rapid realization of economies of scale. In this new analysis, we combine performance simulations with techno-economic analysis to evaluate levelized cost of electricity, and find that the system has potential for cost-competitiveness with natural gas peaking plants and alternative dispatchable renewables.

Tests of a robust eddy correlation system for sensible heat flux

Science.gov (United States)

Blanford, J. H.; Gay, L. W.

1992-03-01

Sensible heat flux estimates from a simple, one-propeller eddy correlation system (OPEC) were compared with those from a sonic anemometer eddy correlation system (SEC). In accordance with similarity theory, the performance of the OPEC system improved with increasing height of the sensor above the surface. Flux totals from the two systems at sites with adequate fetch were in excellent agreement after frequency response corrections were applied. The propeller system appears suitable for long periods of unattended measurement. The sensible heat flux measurements can be combined with net radiation and soil heat flux measurements to estimate latent heat as a residual in the surface energy balance.

Estimating Nitrogen Availability of Heat-Dried Bio solids

International Nuclear Information System (INIS)

Cogger, C.G.; Bary, A.I.; Myhre, E.A.

2011-01-01

As heat-dried bio solids become more widely produced and marketed, it is important to improve estimates of N availability from these materials. Objectives were to compare plant-available N among three different heat-dried bio solids and determine if current guidelines were adequate for estimating application rates. Heat-dried bio solids were surface applied to tall fescue (Festuca arundinacea Schreb.) in Washington State, USA, and forage yield and N uptake measured for two growing seasons following application. Three rates of urea and a zero-N control were used to calculate N fertilizer efficiency regressions. Application year plant-available N (estimated as urea N equivalent) for two bio solids exceeded 60% of total N applied, while urea N equivalent for the third bio solids was 45%. Residual (second-year) urea N equivalent ranged from 5 to 10%. Guidelines for the Pacific Northwest USA recommend mineralization estimates of 35 to 40% for heat-dried bio solids, but this research shows that some heat-dried materials fall well above that range.

Second law analysis of a diesel engine waste heat recovery with a combined sensible and latent heat storage system

International Nuclear Information System (INIS)

Pandiyarajan, V.; Chinnappandian, M.; Raghavan, V.; Velraj, R.

2011-01-01

The exhaust gas from an internal combustion engine carries away about 30% of the heat of combustion. The energy available in the exit stream of many energy conversion devices goes as waste. The major technical constraint that prevents successful implementation of waste heat recovery is due to intermittent and time mismatched demand for and availability of energy. The present work deals with the use of exergy as an efficient tool to measure the quantity and quality of energy extracted from a diesel engine and stored in a combined sensible and latent heat storage system. This analysis is utilized to identify the sources of losses in useful energy within the components of the system considered, and provides a more realistic and meaningful assessment than the conventional energy analysis. The energy and exergy balance for the overall system is quantified and illustrated using energy and exergy flow diagrams. In order to study the discharge process in a thermal storage system, an illustrative example with two different cases is considered and analyzed, to quantify the destruction of exergy associated with the discharging process. The need for promoting exergy analysis through policy decision in the context of energy and environment crisis is also emphasized. - Highlights: → WHR with TES system eliminates the mismatch between the supply of energy and demand. → A saving of 15.2% of energy and 1.6% of exergy is achieved with PCM storage. → Use of multiple PCMs with cascaded system increases energy and exergy efficiency.

Elastocaloric cooling of additive manufactured shape memory alloys with large latent heat

International Nuclear Information System (INIS)

Hou, Huilong; Stasak, Drew; Hasan, Naila Al; Takeuchi, Ichiro; Simsek, Emrah; Ott, Ryan; Cui, Jun; Qian, Suxin

2017-01-01

The stress-induced martensitic phase transformation of shape memory alloys (SMAs) is the basis for elastocaloric cooling. Here we employ additive manufacturing to fabricate TiNi SMAs, and demonstrate compressive elastocaloric cooling in the TiNi rods with transformation latent heat as large as 20 J g −1 . Adiabatic compression on as-fabricated TiNi displays cooling Δ T as high as  −7.5 °C with recoverable superelastic strain up to 5%. Unlike conventional SMAs, additive manufactured TiNi SMAs exhibit linear superelasticity with narrow hysteresis in stress–strain curves under both adiabatic and isothermal conditions. Microstructurally, we find that there are Ti 2 Ni precipitates typically one micron in size with a large aspect ratio enclosing the TiNi matrix. A stress transfer mechanism between reversible phase transformation in the TiNi matrix and mechanical deformation in Ti 2 Ni precipitates is believed to be the origin of the unique superelasticity behavior. (paper)

Coupling of latent heat flux and the greenhouse effect by large-scale tropical/subtropical dynamics diagnosed in a set of observations and model simulations

Energy Technology Data Exchange (ETDEWEB)

Gershunov, A. [Climate Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0224 (United States); Roca, R. [Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, 91128 Palaiseau (France)

2004-03-01

Coupled variability of the greenhouse effect (GH) and latent heat flux (LHF) over the tropical - subtropical oceans is described, summarized and compared in observations and a coupled ocean-atmosphere general circulation model (CGCM). Coupled seasonal and interannual modes account for much of the total variability in both GH and LHF. In both observations and model, seasonal coupled variability is locally 180 out-of-phase throughout the tropics. Moisture is brought into convergent/convective regions from remote source areas located partly in the opposite, non-convective hemisphere. On interannual time scales, the tropical Pacific GH in the ENSO region of largest interannual variance is 180 out of phase with local LHF in observations but in phase in the model. A local source of moisture is thus present in the model on interannual time scales while in observations, moisture is mostly advected from remote source regions. The latent cooling and radiative heating of the surface as manifested in the interplay of LHF and GH is an important determinant of the current climate. Moreover, the hydrodynamic processes involved in the GH-LHF interplay determine in large part the climate response to external perturbations mainly through influencing the water vapor feedback but also through their intimate connection to the hydrological cycle. The diagnostic process proposed here can be performed on other CGCMs. Similarly, it should be repeated using a number of observational latent heat flux datasets to account for the variability in the different satellite retrievals. A realistic CGCM could be used to further study these coupled dynamics in natural and anthropogenically altered climate conditions. (orig.)

The capric and lauric acid mixture with chemical additives as latent heat storage materials for cooling application

Energy Technology Data Exchange (ETDEWEB)

Roxas-Dimaano, M.N. [University of Santo Tomas, Manila (Philippines). Research Center for the Natural Sciences; Watanabe, T. [Tokyo Institute of Technology (Japan). Research Laboratory for Nuclear Reactors

2002-09-01

The mixture of capric acid and lauric acid (C-L acid), with the respective mole composition of 65% and 35%, is a potential phase change material (PCM). Its melting point of 18.0{sup o}C, however, is considered high for cooling application of thermal energy storage. The thermophysical and heat transfer characteristics of the C-L acid with some organic additives are investigated. Compatibility of C-L acid combinations with additives in different proportions and their melting characteristics are analyzed using the differential scanning calorimeter (DSC). Among the chemical additives, methyl salicylate, eugenol, and cineole presented the relevant melting characteristics. The individual heat transfer behavior and thermal storage performance of 0.1 mole fraction of these additives in the C-L acid mixture are evaluated. The radial and axial temperature distribution during charging and discharging at different concentrations of selected PCM combinations are experimentally determined employing a vertical cylindrical shell and tube heat exchanger. The methyl salicylate in the C-L acid provided the most effective additive in the C-L acid. It demonstrated the least melting band width aimed at lowering the melting point of the C-L acid with the highest heat of fusion value with relatively comparable rate of heat transfer. Furthermore, the thermal performance based on the total amount of transferred energy and their rates, established the PCM's latent heat storage capability. (author)

Impact of air-sea drag coefficient for latent heat flux on large scale climate in coupled and atmosphere stand-alone simulations

Science.gov (United States)

Torres, Olivier; Braconnot, Pascale; Marti, Olivier; Gential, Luc

2018-05-01

The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation. Despite decades of effort and improvements, representation of these fluxes still presents a challenge due to the small-scale acting turbulent processes compared to the resolved scales of the models. Beyond this subgrid parameterization issue, a comprehensive understanding of the impact of air-sea interactions on the climate system is still lacking. In this paper we investigates the large-scale impacts of the transfer coefficient used to compute turbulent heat fluxes with the IPSL-CM4 climate model in which the surface bulk formula is modified. Analyzing both atmosphere and coupled ocean-atmosphere general circulation model (AGCM, OAGCM) simulations allows us to study the direct effect and the mechanisms of adjustment to this modification. We focus on the representation of latent heat flux in the tropics. We show that the heat transfer coefficients are highly similar for a given parameterization between AGCM and OAGCM simulations. Although the same areas are impacted in both kind of simulations, the differences in surface heat fluxes are substantial. A regional modification of heat transfer coefficient has more impact than uniform modification in AGCM simulations while in OAGCM simulations, the opposite is observed. By studying the global energetics and the atmospheric circulation response to the modification, we highlight the role of the ocean in dampening a large part of the disturbance. Modification of the heat exchange coefficient modifies the way the coupled system works due to the link between atmospheric circulation and SST, and the different feedbacks between ocean and atmosphere. The adjustment that takes place implies a balance of net incoming solar radiation that is the same in all simulations. As there is no change in model physics other than drag coefficient, we obtain similar latent heat flux

Preliminary investigation of thermal behaviour of PCM based latent heat thermal energy storage

Science.gov (United States)

Pop, Octavian G.; Fechete Tutunaru, Lucian; Bode, Florin; Balan, Mugur C.

2018-02-01

Solid-liquid phase change is used to accumulate and release cold in latent heat thermal energy storage (LHTES) in order to reduce energy consumption of air cooling system in buildings. The storing capacity of the LHTES depends greatly on the exterior air temperatures during the summer nights. One approach in intensifying heat transfer is by increasing the air's velocity. A LHTES was designed to be integrated in the air cooling system of a building located in Bucharest, during the month of July. This study presents a numerical investigation concerning the impact of air inlet temperatures and air velocity on the formation of solid PCM, on the cold storing capacity and energy consumption of the LHTES. The peak amount of accumulated cold is reached at different air velocities depending on air inlet temperature. For inlet temperatures of 14°C and 15°C, an increase of air velocity above 50% will not lead to higher amounts of cold being stored. For Bucharest during the hottest night of the year, a 100 % increase in air velocity will result in 5.02% more cold being stored, at an increase in electrical energy consumption of 25.30%, when compared to the reference values.

Evaluation of Latent Heat Flux Fields from Satellites and Models during SEMAPHORE.

Science.gov (United States)

Bourras, Denis; Liu, W. Timothy; Eymard, Laurence; Tang, Wenqing

2003-02-01

Latent heat fluxes were derived from satellite observations in the region of Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE), which was conducted near the Azores islands in the North Atlantic Ocean in autumn of 1993. The satellite fluxes were compared with output fields of two atmospheric circulation models and in situ measurements. The rms error of the instantaneous satellite fluxes is between 35 and 40 W m-2 and the bias is 60-85 W m-2. The large bias is mainly attributed to a bias in satellite-derived atmospheric humidity and is related to the particular shape of the vertical humidity profiles during SEMAPHORE. The bias in humidity implies that the range of estimated fluxes is smaller than the range of ship fluxes, by 34%-38%. The rms errors for fluxes from models are 30-35 W m-2, and the biases are smaller than the biases in satellite fluxes (14-18 W m-2). Two case studies suggest that the satellites detect horizontal gradients of wind speed and specific humidity if the magnitude of the gradients exceeds a detection threshold, which is 1.27 g kg-1 (100 km)-1 for specific humidity and between 0.35 and 0.82 m s-1 (30 km)-1 for wind speed. In contrast, the accuracy of the spatial gradients of bulk variables from models always varies as a function of the location and number of assimilated observations. A comparison between monthly fluxes from satellites and models reveals that satellite-derived flux anomaly fields are consistent with reanalyzed fields, whereas operational model products lack part of the mesoscale structures present in the satellite fields.

Development and prototype testing of MgCl 2 /graphite foam latent heat thermal energy storage system

Energy Technology Data Exchange (ETDEWEB)

Singh, Dileep; Yu, Wenhua; Zhao, Weihuan; Kim, Taeil; France, David M.; Smith, Roger K.

2018-01-01

Composites of graphite foam infiltrated with a magnesium chloride phase-change material have been developed as high-temperature thermal energy storage media for concentrated solar power applications. This storage medium provides a high thermal energy storage density, a narrow operating temperature range, and excellent heat transfer characteristics. In this study, experimental investigations were conducted on laboratory-scale prototypes with magnesium chloride/graphite foam composite as the latent heat thermal energy storage system. Prototypes were designed and built to monitor the melt front movement during the charging/discharging tests. A test loop was built to ensure the charging/discharging of the prototypes at temperatures > 700 degrees C. Repeated thermal cycling experiments were carried out on the fabricated prototypes, and the experimental temperature profiles were compared to the predicted results from numerical simulations using COMSOL Multiphysics software. Experimental results were found to be in good agreement with the simulations to validate the thermal models.

Study of the thermal behavior of a latent heat cold storage unit operating under frosting conditions

International Nuclear Information System (INIS)

Simard, A.P.; Lacroix, M.

2003-01-01

A study is performed of the thermal behavior of a latent heat cold storage unit operating under frosting conditions. This unit is employed to maintain the temperature inside the refrigerated compartment of a truck below 265 K. The system consists of parallel plates filled with a phase change material (PCM) that absorbs heat from the flow of warm moist air. A mathematical model for the system is first presented and, next, validated with numerical and experimental data. It is then exploited to assess the effects of design parameters and operating conditions on the performance of the system. The recommended thickness and distance separating the PCM plates are found to be 50x10 -3 and 30x10 -3 m, respectively. The results indicate that the performance of the unit is enhanced by turbulent air flow in spite of the increased pressure loss and accentuated frost growth. The unit also performs well even when the surrounding relative humidity is 100%

A Non-Gaussian Spatial Generalized Linear Latent Variable Model

KAUST Repository

Irincheeva, Irina; Cantoni, Eva; Genton, Marc G.

2012-01-01

We consider a spatial generalized linear latent variable model with and without normality distributional assumption on the latent variables. When the latent variables are assumed to be multivariate normal, we apply a Laplace approximation. To relax the assumption of marginal normality in favor of a mixture of normals, we construct a multivariate density with Gaussian spatial dependence and given multivariate margins. We use the pairwise likelihood to estimate the corresponding spatial generalized linear latent variable model. The properties of the resulting estimators are explored by simulations. In the analysis of an air pollution data set the proposed methodology uncovers weather conditions to be a more important source of variability than air pollution in explaining all the causes of non-accidental mortality excluding accidents. © 2012 International Biometric Society.

A Non-Gaussian Spatial Generalized Linear Latent Variable Model

KAUST Repository

Irincheeva, Irina

2012-08-03

We consider a spatial generalized linear latent variable model with and without normality distributional assumption on the latent variables. When the latent variables are assumed to be multivariate normal, we apply a Laplace approximation. To relax the assumption of marginal normality in favor of a mixture of normals, we construct a multivariate density with Gaussian spatial dependence and given multivariate margins. We use the pairwise likelihood to estimate the corresponding spatial generalized linear latent variable model. The properties of the resulting estimators are explored by simulations. In the analysis of an air pollution data set the proposed methodology uncovers weather conditions to be a more important source of variability than air pollution in explaining all the causes of non-accidental mortality excluding accidents. © 2012 International Biometric Society.

Latent heat loss and sweat gland histology of male goats in an equatorial semi-arid environment

Science.gov (United States)

de Melo Costa, Cíntia Carol; Maia, Alex Sandro Campos; Neto, José Domingues Fontenele; Oliveira, Steffan Edward Octávio; de Queiroz, João Paulo Araújo Fernandes

2014-03-01

The objective of this work was to quantify the heat loss by cutaneous evaporation of goats in an equatorial semi-arid environment. The latent heat loss from the body surfaces of these ten undefined breed goats was measured using a ventilated capsule in sun and shade and in the three body regions (neck, flank and hindquarters). Skin samples from these three regions were histologically analyzed to relate the quantity of sweat glands, the area of sweat glands and the epithelium thickness of each of these regions to the heat loss by cutaneous evaporation of the examined goats. The epithelium thickness that was measured varied significantly for body regions with different quantities and areas of sweat glands ( P < 0.01). Among the body regions that were examined, the samples from the neck demonstrated the highest epithelium thickness (16.23 ± 0.13 μm). However, the samples of sweat glands from the flank had the biggest area (43330.51 ± 778.71 μm2) and quantity per square centimeter (390 ± 9 cm-2). After the animals were exposed to sun, the flanks lost the greatest amount of heat by cutaneous evaporation (73.03 ± 1.75 W m-2) and possessed the highest surface temperatures (39.47 ± 0.18 °C). The histological characteristics may have influenced the heat loss by cutaneous evaporation that was observed in the flank region after the animals were exposed to sun.

Coupling heat and chemical tracer experiments for estimating heat transfer parameters in shallow alluvial aquifers.

Science.gov (United States)

Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A

2014-11-15

Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for

Estimation of heat transfer and heat source in a molten pool

Energy Technology Data Exchange (ETDEWEB)

Yun, J.I.; Suh, K.Y.; Kang, C.S. [Seoul National Univ., Dept. of Nuclear Engineering (Korea, Republic of)

2001-07-01

Heat transfer and fluid flow in a molten pool are influenced by internal volumetric heat generated from the radioactive decay of fission product species retained in the pool. The pool superheat is determined based on the overall energy balance that equates the heat production rate to the heat loss rate. Decay heat of fission products in the pool was estimated by product of the mass concentration and energy conversion factor of each fission product. For the calculation of heat generation rate in the pool, twenty-nine (29) elements were chosen and classified by their chemical properties. The mass concentration of a fission product is obtained from released fraction and the tabular output of the ORIGEN 2 code. The initial core and pool inventories at each time can also be estimated using ORIGEN 2. The released fraction of each fission product is calculated based on the bubble dynamics and mass transport. Numerical analysis was performed for the TMI-2 accident. The pool is assumed to be a partially filled hemispherical geometry, 1.45 m in radius and 32,700 kg in mass. The change of pool geometry during the numerical calculation was neglected. The peak temperature sizably decreased by about 60 K as the fission products were released from the pool. (author)

Estimation of heat transfer and heat source in a molten pool

International Nuclear Information System (INIS)

Yun, J.I.; Suh, K.Y.; Kang, C.S.

2001-01-01

Heat transfer and fluid flow in a molten pool are influenced by internal volumetric heat generated from the radioactive decay of fission product species retained in the pool. The pool superheat is determined based on the overall energy balance that equates the heat production rate to the heat loss rate. Decay heat of fission products in the pool was estimated by product of the mass concentration and energy conversion factor of each fission product. For the calculation of heat generation rate in the pool, twenty-nine (29) elements were chosen and classified by their chemical properties. The mass concentration of a fission product is obtained from released fraction and the tabular output of the ORIGEN 2 code. The initial core and pool inventories at each time can also be estimated using ORIGEN 2. The released fraction of each fission product is calculated based on the bubble dynamics and mass transport. Numerical analysis was performed for the TMI-2 accident. The pool is assumed to be a partially filled hemispherical geometry, 1.45 m in radius and 32,700 kg in mass. The change of pool geometry during the numerical calculation was neglected. The peak temperature sizably decreased by about 60 K as the fission products were released from the pool. (author)

Stability of latent class segments over time

DEFF Research Database (Denmark)

Mueller, Simone

2011-01-01

Dynamic stability, as the degree to which identified segments at a given time remain unchanged over time in terms of number, size and profile, is a desirable segment property which has received limited attention so far. This study addresses the question to what degree latent classes identified from...... logit model suggests significant changes in the price sensitivity and the utility from environmental claims between both experimental waves. A pooled scale adjusted latent class model is estimated jointly over both waves and the relative size of latent classes is compared across waves, resulting...... in significant differences in the size of two out of seven classes. These differences can largely be accounted for by the changes on the aggregated level. The relative size of latent classes is correlated at 0.52, suggesting a fair robustness. An ex-post characterisation of latent classes by behavioural...

Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective

DEFF Research Database (Denmark)

Morillas, L.; Garcia Garcia, Monica; Nieto Solana, Hector

2013-01-01

A two-source model (TSM) for surface energy balance, considering explicitly soil and vegetation components, was tested under water stress conditions. The TSM evaluated estimates the sensible heat flux (H) using the surface-air thermal gradient and the latent heat flux (LE) as a residual from the ...

Wavelet maxima curves of surface latent heat flux associated with two recent Greek earthquakes

Science.gov (United States)

Cervone, G.; Kafatos, M.; Napoletani, D.; Singh, R. P.

2004-05-01

Multi sensor data available through remote sensing satellites provide information about changes in the state of the oceans, land and atmosphere. Recent studies have shown anomalous changes in oceans, land, atmospheric and ionospheric parameters prior to earthquakes events. This paper introduces an innovative data mining technique to identify precursory signals associated with earthquakes. The proposed methodology is a multi strategy approach which employs one dimensional wavelet transformations to identify singularities in the data, and an analysis of the continuity of the wavelet maxima in time and space to identify the singularities associated with earthquakes. The proposed methodology has been employed using Surface Latent Heat Flux (SLHF) data to study the earthquakes which occurred on 14 August 2003 and on 1 March 2004 in Greece. A single prominent SLHF anomaly has been found about two weeks prior to each of the earthquakes.

Using latent variable approach to estimate China's economy-wide energy rebound effect over 1954–2010

International Nuclear Information System (INIS)

Shao, Shuai; Huang, Tao; Yang, Lili

2014-01-01

The energy rebound effect has been a significant issue in China, which is undergoing economic transition, since it reflects the effectiveness of energy-saving policy relying on improved energy efficiency. Based on the IPAT equation and Brookes' explanation of the rebound effect, this paper develops an alternative estimation model of the rebound effect. By using the estimation model and latent variable approach, which is achieved through a time-varying coefficient state space model, we estimate China's economy-wide energy rebound effect over 1954–2010. The results show that the rebound effect evidently exists in China as a result of the annual average of 39.73% over 1954–2010. Before and after the implementation of China's reform and opening-up policy in 1978, the rebound effects are 47.24% and 37.32%, with a strong fluctuation and a circuitously downward trend, respectively, indicating that a stable political environment and the development of market economy system facilitate the effectiveness of energy-saving policy. Although the energy-saving effect of improving energy efficiency has been partly realised, there remains a large energy-saving potential in China. - Highlights: • We present an improved estimation methodology of economy-wide energy rebound effect. • We use the latent variable approach to estimate China's economy-wide rebound effect. • The rebound exists in China and varies before and after reform and opening-up. • After 1978, the average rebound is 37.32% with a circuitously downward trend. • Traditional Solow remainder method underestimates the rebound in most cases

Estimating heat-to-heat variation in mechanical properties from a statistician's point of view

International Nuclear Information System (INIS)

Hebble, T.L.

1976-01-01

A statistical technique known as analysis of variance (ANOVA) is used to estimate the variance and standard deviation of differences among heats. The total variation of a collection of observations and how an ANOVA can be used to partition the total variation into its sources are discussed. Then, the ANOVA is adapted to published Japanese data indicating how to estimate heat-to-heat variation. Finally, numerical results are computed for several tensile and creep properties of Types 304 and 316 SS

The data assimilation method ''Latent Heat Nudging'' assessed with the Dynamic State Index

Energy Technology Data Exchange (ETDEWEB)

Claussnitzer, Antje [Freie Univ. Berlin (Germany). Inst. fuer Meteorologie; Deutscher Wetterdienst, Offenbach (Germany); Schartner, Thomas; Nevir, Peter; Cubasch, Ulrich [Freie Univ. Berlin (Germany). Inst. fuer Meteorologie; Stephan, Klaus [Deutscher Wetterdienst, Offenbach (Germany)

2011-04-15

In April 2007, the German Weather Service (DWD) added the non-hydrostatic limited area model COSMODE to its model chain. COSMO-DE covers mainly Germany and bordering countries and has a horizontal resolution of 2.8 km (0.025 ). An advantage of the COSMO-DE is that deep convection is expected to be resolved explicitly. In order to improve the initial state of COSMO-DE an assimilation of radar derived precipitation rates is applied by using ''Latent Heat Nudging'' (LHN). The aim of LHN is to adjust the model state so that the model will respond by producing a rain rate close to the observed value. In this study, the influence of LHN on diabatic processes is investigated by evaluation of the Dynamic State Index (DSI). The DSI is calculated on both isentropic (DSI{sub {theta}}) and model levels (DSI{sub {sigma}}). To analyse the influence of LHN, model analyses with and without LHN are examined for summer 2009 (June to August). The influence of LHN is also examined in more detail in a case study of a heavy rainfall event on July 18, 2009 where a strong rainfall area was developed on the front side of a trough. Results, based on a statistical investigation and the case study, show that the model with LHN can reproduce the observed rainfall better than the runs without LHN. This is also suggested by a higher correlation between DSI and observed precipitation. The release of latent heat enhances the diabatic processes associated with the formation of additional potential vorticity anomalies resulting in stronger DSI -signals. (orig.)

Latent lifestyle preferences and household location decisions

Science.gov (United States)

Walker, Joan L.; Li, Jieping

2007-04-01

Lifestyle, indicating preferences towards a particular way of living, is a key driver of the decision of where to live. We employ latent class choice models to represent this behavior, where the latent classes are the lifestyles and the choice model is the choice of residential location. Thus, we simultaneously estimate lifestyle groups and how lifestyle impacts location decisions. Empirical results indicate three latent lifestyle segments: suburban dwellers, urban dwellers, and transit-riders. The suggested lifestyle segments have intriguing policy implications. Lifecycle characteristics are used to predict lifestyle preferences, although there remain significant aspects that cannot be explained by observable variables.

Estimating the Heat of Formation of Foodstuffs and Biomass

Energy Technology Data Exchange (ETDEWEB)

Burnham, Alan K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2010-11-23

Calorie estimates for expressing the energy content of food are common, however they are inadequate for the purpose of estimating the chemically defined heat of formation of foodstuffs for two reasons. First, they assume utilization factors by the body.1,2,3 Second, they are usually based on average values for their components. The best way to solve this problem would be to measure the heat of combustion of each material of interest. The heat of formation can then be calculated from the elemental composition and the heats of formation of CO2, H2O, and SO2. However, heats of combustion are not always available. Sometimes elemental analysis only is available, or in other cases, a breakdown into protein, carbohydrates, and lipids. A simple way is needed to calculate the heat of formation from various sorts of data commonly available. This report presents improved correlations for relating the heats of combustion and formation to the elemental composition, moisture content, and ash content. The correlations are also able to calculate heats of combustion of carbohydrates, proteins, and lipids individually, including how they depend on elemental composition. The starting point for these correlations are relationships commonly used to estimate the heat of combustion of fossil fuels, and they have been modified slightly to agree better with the ranges of chemical structures found in foodstuffs and biomass.

Techno-economic analysis of a concentrating solar collector with built-in shell and tube latent heat thermal energy storage

International Nuclear Information System (INIS)

Li, Qiyuan; Tehrani, S. Saeed Mostafavi; Taylor, Robert A.

2017-01-01

In this paper, the feasibility of a medium temperature, low profile concentrated solar thermal collector integrated with latent heat thermal energy storage (LHTES) is investigated. The proposed modular integrated collector storage (ICS) system consists of six solar receiver units and seven cylindrical shell and tube LHTES tanks. By implementing an innovative optical concentration assembly and an internal linear tracking mechanism, the collector can concentrate beam radiation to the tube receivers during the highest flux hours of a day without any external or rotational motion. The collector's efficiency correlations were obtained experimentally and its integrated performance – with the LHTES units – was evaluated numerically. To demonstrate the potential of this proposed ICS system, an annual analysis was carried out for a characteristic industrial application – a dairy dehydration process that requires a constant 50 kW th of heat in the 120–150 °C temperature range. It was found that adding the storage units will increase the capital costs by ∼10%, but it can increase the annual thermal output of the system by up to ∼20%. A solar fraction of 65% was achievable with some design alternatives, but the optimum techno-economic design had a solar fraction of ∼35% and an annual charging efficiency of nearly 100%. It was also found that if the capital cost of the ICS (collector and LHTES tank) system could be reduced by 50% from an estimated ∼1000 US$/m 2 to ∼500 US$/m 2 through mass production and/or further design optimizations, this system could provide industrial process heat with a levelized cost of heating (LCOH) of ∼0.065 US$/kWh th . - Highlights: • An innovative ICS system was proposed and analyzed for industrial heat applications. • The optimum design can achieve a ∼35% solar fraction with ∼100% charging efficiency. • A 0.12 US$/kWh LCOH was found, but further reductions could result in 0.065 US$/kWh. • Costs reductions of

Gradient estimates on the weighted p-Laplace heat equation

Science.gov (United States)

Wang, Lin Feng

2018-01-01

In this paper, by a regularization process we derive new gradient estimates for positive solutions to the weighted p-Laplace heat equation when the m-Bakry-Émery curvature is bounded from below by -K for some constant K ≥ 0. When the potential function is constant, which reduce to the gradient estimate established by Ni and Kotschwar for positive solutions to the p-Laplace heat equation on closed manifolds with nonnegative Ricci curvature if K ↘ 0, and reduce to the Davies, Hamilton and Li-Xu's gradient estimates for positive solutions to the heat equation on closed manifolds with Ricci curvature bounded from below if p = 2.

Evapotranspiration and heat fluxes over a patchy forest - studied using modelling and measurements

DEFF Research Database (Denmark)

Sogachev, Andrey; Dellwik, Ebba; Boegh, Eva

using these parameters without a proper interpretation in mesoscale or global circulation models can results in serious bias of estimates of modelled evapotranspiration or heat fluxes from given area. Since representative measurements focused on heterogeneous effects are scarce numerical modelling can...... and latent heat flux above forest downwind of a forest edge show these fluxes to be larger than the available energy over the forest (Klaassen et al. 2002, Theor. Appl. Climatol. 72, 231-243). Because such flux measurements are very often used for calibration of forest parameters or model constants, further......, Ecological. Appl. 18, 1454-1459). In the present work, we apply the SCADIS with enhanced turbulence closure including buoyancy for investigation of the spatial distribution of latent and sensible heat vertical fluxes over patchy forested terrain in Denmark during selected days in the summer period. A closer...

Wavelet maxima curves of surface latent heat flux associated with two recent Greek earthquakes

Directory of Open Access Journals (Sweden)

G. Cervone

2004-01-01

Full Text Available Multi sensor data available through remote sensing satellites provide information about changes in the state of the oceans, land and atmosphere. Recent studies have shown anomalous changes in oceans, land, atmospheric and ionospheric parameters prior to earthquakes events. This paper introduces an innovative data mining technique to identify precursory signals associated with earthquakes. The proposed methodology is a multi strategy approach which employs one dimensional wavelet transformations to identify singularities in the data, and an analysis of the continuity of the wavelet maxima in time and space to identify the singularities associated with earthquakes. The proposed methodology has been employed using Surface Latent Heat Flux (SLHF data to study the earthquakes which occurred on 14 August 2003 and on 1 March 2004 in Greece. A single prominent SLHF anomaly has been found about two weeks prior to each of the earthquakes.

Seasonal and annual heat budgets offshore the Hanko Peninsula, Gulf of Finland

Energy Technology Data Exchange (ETDEWEB)

Merkouriadi, I.; Lepparanta, M. [Helsinki Univ. (Finland). Dept. of Physics], Email: ioanna.merkouriadi@helsinki.fi; Shirasawa, K. [Hokkaido Univ., Sapporo (Japan). Pan-Okhotsk Research Center, Inst. of Low Temperature Science

2013-06-01

A joint Finnish-Japanese sea-ice experiment 'Hanko-9012' carried out offshore the Hanko Peninsula included seasonal monitoring and intensive field campaigns. Ice, oceanographic and meteorological data were collected to examine the structure and properties of the Baltic Sea brackish ice, heat budget and solar radiation transfer through the ice cover. Here, the data from two years (2000 and 2001) are used for the estimation of the seasonal and annual heat budgets. Results present the surface heat balance, and the heat budget of the ice sheet and the waterbody. The ice cover acted as a good control measure of the net surface heat exchange. Solar radiation had a strong seasonal cycle with a monthly maximum at 160 and a minimum below 10 W m{sup -2}, while net terrestrial radiation was mostly between -40 and -60 W m{sup -2}. Latent heat exchange was much more important than sensible heat exchange, similar the net terrestrial radiation values in summer and autumn. A comparison between the latent heat flux released or absorbed by the ice and the net surface heat fluxes showed similar patterns, with a clearly better fit in 2001. The differences can be partly explained by the oceanic heat flux to the lower ice boundary. (orig.)

Latent effectiveness of desiccant wheel: A silica gels- water system

International Nuclear Information System (INIS)

Rabah, A. A.; Mohamed, S. A.

2009-01-01

A latent heat effectiveness model in term of dimensionless groups? =f (NTU, m * ,Crm * ) for energy wheel has been analytically derived. The energy wheel is divided into humidification and dehumidification sections. For each section macroscopic mass differential equations for gas and the matrix were applied. In this process local latent effectiveness (? c ,? h ) for the humidification and dehumidification section of the wheel were obtained. The Latent effectiveness of the wheel is then derived form local effectiveness [? =f (? c ,? h)]. The model is compared with the existing experimental investigation and manufacturer data for energy wheel. More than 90% of the experimental data within a confidence limit of 95%. (Author)

Latent variables and route choice behavior

DEFF Research Database (Denmark)

Prato, Carlo Giacomo; Bekhor, Shlomo; Pronello, Cristina

2012-01-01

In the last decade, a broad array of disciplines has shown a general interest in enhancing discrete choice models by considering the incorporation of psychological factors affecting decision making. This paper provides insight into the comprehension of the determinants of route choice behavior...... and bound algorithm. A hybrid model consists of measurement equations, which relate latent variables to measurement indicators and utilities to choice indicators, and structural equations, which link travelers’ observable characteristics to latent variables and explanatory variables to utilities. Estimation...

Ridge Width Correlations between Inked Prints and Powdered Latent Fingerprints.

Science.gov (United States)

De Alcaraz-Fossoul, Josep; Barrot-Feixat, Carme; Zapico, Sara C; Mancenido, Michelle; Broatch, Jennifer; Roberts, Katherine A; Carreras-Marin, Clara; Tasker, Jack

2017-10-03

A methodology to estimate the time of latent fingerprint deposition would be of great value to law enforcement and courts. It has been observed that ridge topography changes as latent prints age, including the widths of ridges that could be measured as a function of time. Crime suspects are commonly identified using fingerprint databases that contain reference inked tenprints (flat and rolled impressions). These can be of interest in aging studies as they provide baseline information relating to the original (nonaged) ridges' widths. In practice, the age of latent fingerprints could be estimated following a comparison process between the evidentiary aged print and the corresponding reference inked print. The present article explores possible correlations between inked and fresh latent fingerprints deposited on different substrates and visualized with TiO 2 . The results indicate that the ridge width of flat inked prints is most similar to fresh latent fingerprints , and these should be used as the comparison standard for future aging studies. © 2017 American Academy of Forensic Sciences.

Thermal conductivity and latent heat thermal energy storage properties of LDPE/wax as a shape-stabilized composite phase change material

International Nuclear Information System (INIS)

Trigui, Abdelwaheb; Karkri, Mustapha; Krupa, Igor

2014-01-01

Highlights: • This study deals with the comparison of experimental results for different PCM composite to be used in passive solar walls. • This paper reports on the successful use of a specific experimental method in order to characterize the phase change effects. • The results have shown that most important thermal properties of these composites at the solid and liquid states. • Results indicate the thermal effectiveness of phase change material and significant amount of energy saving can be achieved. • Heat flux measurements are a very interesting experimental source of data which comes to complete the calorimetric device (DSC). - Abstract: Phase change material (PCM) composites based on low-density polyethylene (LDPE) with paraffin waxes were investigated in this study. The composites were prepared using a meltmixing method with a Brabender-Plastograph. The LDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (LDPE) is a necessary property for effective energy storage. Therefore, this type paraffin can be used in a latent heat storage system without encapsulation. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. In addition, a DSC analysis was carried out. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Results indicate the performance of the proposed system is affected by the thermal effectiveness of

Heat storage in forest biomass significantly improves energy balance closure particularly during stable conditions

Science.gov (United States)

Lindroth, A.; Mölder, M.; Lagergren, F.

2009-08-01

Temperature measurements in trunks and branches in a mature ca. 100 years-old mixed pine and spruce forest in central Sweden were used to estimate the heat storage in the tree biomass. The estimated heat flux in the sample trees and data on biomass distributions were used to scale up to stand level biomass heat fluxes. The rate of change of sensible and latent heat storage in the air layer below the level of the flux measurements was estimated from air temperature and humidity profile measurements and soil heat flux was estimated from heat flux plates and soil temperature measurements. The fluxes of sensible and latent heat from the forest were measured with an eddy covariance system in a tower. The analysis was made for a two-month period in summer of 1995. The tree biomass heat flux was the largest of the estimated storage components and varied between 40 and -35 W m-2 on summer days with nice weather. Averaged over two months the diurnal maximum of total heat storage was 45 W m-2 and the minimum was -35 W m-2. The soil heat flux and the sensible heat storage in air were out of phase with the biomass flux and they reached maximum values that were about 75% of the maximum of the tree biomass heat storage. The energy balance closure improved significantly when the total heat storage was added to the turbulent fluxes. The slope of a regression line with sum of fluxes and storage as independent and net radiation as dependent variable, increased from 0.86 to 0.95 for half-hourly data and the scatter was also reduced. The most significant finding was, however, that during nights with strongly stable conditions when the sensible heat flux dropped to nearly zero, the total storage matched the net radiation nearly perfectly. Another interesting result was that the mean energy imbalance started to increase when the Richardson number became more negative than ca. -0.1. In fact, the largest energy deficit occurred at maximum instability. Our conclusion is that eddy

Monitoring the latent and sensible heat fluxes in vineyard by applying the energy balance model METRIC

Directory of Open Access Journals (Sweden)

J. González-Piqueras

2015-06-01

Full Text Available The monitoring of the energy fluxes over vineyard applying the one source energy balance model METRIC (Allen et al., 2007b are shown in this work. This model is considered operaive because it uses an internalized calibration method derived from the selection of two extreme pixels in the scene, from the minimum ET values such as the bare soil to a maximum that corresponds to full cover active vegetation. The model provides the maps of net radiation (Rn, soil heat flux (G, sensible heat (H, latent heat (LE, evapotranspiration (ET and crop coefficient (Kc. The flux values have been validated with a flux tower installed in the plot, providing a RMSE for instantaneous fluxes of 43 W m2, 33 W m2, 55 W m2 y 40 W m2 on Rn, G, H and LE. In relative terms are 8%, 29%, 21% and 20% respectively. The RMSE at daily scale for the ET is 0.58 mm day-1, with a value in the crop coefficient for the mid stage of 0.42±0.08. These results allow considering the model adequate for crop monitoring and irrigation purposes in vineyard. The values obtained have been compared to other studies over vineyard and with alternative energy balance models showing similar results.

Agricultural greenhouse with storage of sensible and latent heat in the soil. Modeling and simulation of thermal and hydric transfer. Experimental validation

Energy Technology Data Exchange (ETDEWEB)

Al Cheikh Kassem, N.; Miriel, J.; Roux, A. [Institut National des Sciences Appliquees (INSA), 35 - Rennes (France)

1993-12-31

This work presents a simulation model of sensible and latent heat storage in the soil of an agricultural greenhouse. Results recorded by the laboratory device of grounded storage and thermo-physic parameter values of soil experimentally obtained by a three rod thermal shock probe are used for checking the simulation model and thus assessing the performance of such a system and the coupling between the greenhouse and the storage. (Authors). 3 refs., 6 figs.

Development of a tube-type solar still equipped with heat accumulation for irrigation

International Nuclear Information System (INIS)

Murase, Kazuo; Yamagishi, Yusuke; Iwashita, Yusuke; Sugino, Keita

2008-01-01

A tube-type solar still is found to be suitable for use in desert irrigation. The effectiveness of a heat accumulator with regard to distillate productivity is experimentally and numerically verified. The heat accumulator consists of tube bundles immersed in wax in order to utilize the latent heat of wax. The dynamic response to stepwise variation of irradiative intensity verified the contribution of wax to an increase of productivity only when the phase change of wax occurred. The effective distillate productivity was found to be 294.3 g/m 2 during the cyclic stepwise change of irradiative intensity, from 200 to 600 W/m 2 and back. Velocity vectors driven by natural convection and temperature contours estimated by numerical simulation verified the effectiveness of the heat accumulator especially after peak solar intensity. The latent heat of wax effectively contributed to a 15% increase in total distillate productivity per day. The still can feasibly meet irrigation water supply demands above an irrigative threshold of 17 MJ/m 2 d

Preparation, Characterization and Thermal Properties of Paraffin Wax – Expanded Perlite Form-Stable Composites for Latent Heat Storage

Directory of Open Access Journals (Sweden)

Tugba GURMEN OZCELIK

2017-02-01

Full Text Available In this study, form-stable composite phase change materials (PCM for latent heat storage were prepared by impregnating paraffin wax into the pores of the expanded perlite (EP. The characterization of the composite PCMs was performed by FTIR, TGA, SEM and DSC analysis. The melting point and heat of fusion were determined for 25 % paraffin included composite, as 54.3 °C and 94.71 J/g and for 45 % paraffin included composite as 53.6 °C and 106.69 J/g, respectively. The FTIR results showed that there were no chemical reaction between the perlite and paraffin. TGA analysis indicated that both composite PCMs had good thermal stability. SEM images showed that the paraffin was dispersed uniformly into the pores and on the EP surface. There was no leakage and degradation at the composite PCMs after heating and cooling cycles. According to the results, both prepared composites showed good thermal energy storage properties, reliability and stability. All results suggested that the presented form- stable composite PCMs has great potential for thermal energy storage applications.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.13661

Micro/nano encapsulation of some paraffin eutectic mixtures with poly(methyl methacrylate) shell: Preparation, characterization and latent heat thermal energy storage properties

International Nuclear Information System (INIS)

Sarı, Ahmet; Alkan, Cemil; Bilgin, Cahit

2014-01-01

Graphical abstract: Four kinds of micro/nano capsules, PMMA/(C17-C24), PMMA/(C19-C18), PMMA/(C19-C24) and PMMA/(C20-C24), were synthesized successfully as novel encapsulated phase change materials (PCMs) for the different monomer/PEM ratios via emulsion polymerization. The FTIR spectroscopy analysis confirmed the polymerization reaction occurred around the PEMs to be used as core materials. The POM, SEM and PSD analysis results showed that the synthesized PMMA/PEM micro/nano capsules had spherical shape appearance and micro/nano sizes. DSC analysis measurements revealed that the prepared micro/nano capsules containing the highest PEM content had a melting temperature range of about 20–36 °C and latent heat capacities in the range of about 86–169 J/g. TGA findings demonstrated that the encapsulated PEMs had good thermal reliability and chemical stability even after subjecting them to 5000 melting/freezing cycles. Furthermore, the prepared micro/nano capsules had reasonable thermal conductivity values and fine melting–freezing reversibility. - Highlights: • PSD analysis results showed that the encapsulated PEMs had micro/nano sized-spheres. • The encapsulated PEMs melt in the temperature range of about 20–36 °C. • The encapsulated PEMs had latent heat capacities of in the range of about 86–169 J/g. • TGA results demonstrated that they had good thermal stability. • The encapsulated PEMs had good thermal conductivity and phase change reversibility. - Abstract: This work is aimed to prepare, characterize and determine the latent heat thermal energy storage properties of micro/nano encapsulated paraffin eutectic mixtures (PEMs) with polymethylmethacrylate (PMMA) shell. The eutectic combination ratios and optimum melting temperatures of C17-C24, C19-C18, C19-C24 and C20-C24 mixtures were find out prior to the encapsulation processes. Four kinds of micro/nano capsules, PMMA/(C17-C24), PMMA/(C19-C18), PMMA/(C19-C24) and PMMA/(C20-C24), were synthesized

Scan-rate and vacuum pressure dependence of the nucleation and growth dynamics in a spin-crossover single crystal: the role of latent heat.

Science.gov (United States)

Ridier, Karl; Rat, Sylvain; Salmon, Lionel; Nicolazzi, William; Molnár, Gábor; Bousseksou, Azzedine

2018-04-04

Using optical microscopy we studied the vacuum pressure dependence (0.1-1000 mbar) of the nucleation and growth dynamics of the thermally induced first-order spin transition in a single crystal of the spin-crossover compound [Fe(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl). A crossover between a quasi-static hysteresis regime and a temperature-scan-rate-dependent kinetic regime is evidenced around 5 mbar due to the change of the heat exchange coupling between the crystal and its external environment. Remarkably, the absorption/dissipation rate of latent heat was identified as the key factor limiting the switching speed of the crystal.

Surface Heat Balance Analysis of Tainan City on March 6, 2001 Using ASTER and Formosat-2 Data

Directory of Open Access Journals (Sweden)

Chen-Yi Sun

2008-09-01

Full Text Available The urban heat island phenomenon occurs as a mixed result of anthropogenic heat discharge, decreased vegetation, and increased artificial impervious surfaces. To clarify the contribution of each factor to the urban heat island, it is necessary to evaluate the surface heat balance. Satellite remote sensing data of Tainan City, Taiwan, obtained from Terra ASTER and Formosat-2 were used to estimate surface heat balance in this study. ASTER data is suitable for analyzing heat balance because of the wide spectral range. We used Formosat-2 multispectral data to classify the land surface, which was used to interpolate some surface parameters for estimating heat fluxes. Because of the high spatial resolution of the Formosat-2 image, more roads, open spaces and small vegetation areas could be distinguished from buildings in urban areas; however, misclassifications of land cover in such areas using ASTER data would overestimate the sensible heat flux. On the other hand, the small vegetated areas detected from the Formosat-2 image slightly increased the estimation of latent heat flux. As a result, the storage heat flux derived from Formosat-2 is higher than that derived from ASTER data in most areas. From these results, we can conclude that the higher resolution land coverage map increases accuracy of the heat balance analysis. Storage heat flux occupies about 60 to 80% of the net radiation in most of the artificial surface areas in spite of their usages. Because of the homogeneity of the building roof materials, there is no contrast between the storage heat flux in business and residential areas. In sparsely vegetated urban areas, more heat is stored and latent heat is smaller than that in the forested suburbs. This result implies that density of vegetation has a significant influence in decreasing temperatures.

Estimation of transient heat flux density during the heat supply of a catalytic wall steam methane reformer

Science.gov (United States)

Settar, Abdelhakim; Abboudi, Saïd; Madani, Brahim; Nebbali, Rachid

2018-02-01

Due to the endothermic nature of the steam methane reforming reaction, the process is often limited by the heat transfer behavior in the reactors. Poor thermal behavior sometimes leads to slow reaction kinetics, which is characterized by the presence of cold spots in the catalytic zones. Within this framework, the present work consists on a numerical investigation, in conjunction with an experimental one, on the one-dimensional heat transfer phenomenon during the heat supply of a catalytic-wall reactor, which is designed for hydrogen production. The studied reactor is inserted in an electric furnace where the heat requirement of the endothermic reaction is supplied by electric heating system. During the heat supply, an unknown heat flux density, received by the reactive flow, is estimated using inverse methods. In the basis of the catalytic-wall reactor model, an experimental setup is engineered in situ to measure the temperature distribution. Then after, the measurements are injected in the numerical heat flux estimation procedure, which is based on the Function Specification Method (FSM). The measured and estimated temperatures are confronted and the heat flux density which crosses the reactor wall is determined.

CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

Science.gov (United States)

Crespo, J.; Posselt, D. J.

2017-12-01

The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

Study of the Melting Latent Heat of Semicrystalline PVDF applied to High Gamma Dose Dosimetry

Energy Technology Data Exchange (ETDEWEB)

Batista, Adriana S.M. [Departamento de Anatomia e Imagem - IMA, Universidade Federal de Minas Gerais, Av. Prof. Alfredo Balena, 190, 30130-100, Belo Horizonte, MG (Brazil); Gual, Maritza R.; Faria, Luiz O. [Centro de Desenvolvimento da Tecnologia Nuclear - CDTN, Av. Antonio Carlos 6627, C.P. 941, 31270-901, Belo Horizonte, MG (Brazil); Lima, Claubia P.B. [Departamento de Engenharia Nuclear - DEN, Universidade Federal de Minas Gerais - UFMG, Av. Antonio Carlos 6627, 31270-970 Belo Horizonte, MG (Brazil)

2015-07-01

Poly(vinylidene fluoride) homopolymers [PVDF] homopolymers were irradiated with gamma doses ranging from 0.5 to 2.75 MGy. Differential scanning calorimetry (DSC) and FTIR spectrometry were used in order to study the effects of gamma radiation in the amorphous and crystalline polymer structures. The FTIR data revealed absorption bands at 1730 and 1853 cm{sup -1} which were attributed to the stretch of C=O bonds, at 1715 and 1754 cm{sup -1} which were attributed to the C=C stretching and at 3518, 3585 and 3673 cm{sup -1} which were associated with NH stretch of NH{sub 2} and OH. The melting latent heat (LM) measured by DSC was used to construct an unambiguous relationship with the delivered dose. Regression analyses revealed that the best mathematical function that fits the experimental calibration curve is a 4-degree polynomial function, with an adjusted Rsquare of 0.99817. (authors)

Active heat exchange system development for latent heat thermal energy storage

Science.gov (United States)

Lefrois, R. T.; Mathur, A. K.

1980-01-01

Five tasks to select, design, fabricate, test and evaluate candidate active heat exchanger modules for future applications to solar and conventional utility power plants were discussed. Alternative mechanizations of active heat exchange concepts were analyzed for use with heat of fusion phase change materials (PCMs) in the temperature range of 250 to 350 C. Twenty-six heat exchange concepts were reviewed, and eight were selected for detailed assessment. Two candidates were selected for small-scale experimentation: a coated tube and shell heat exchanger and a direct contact reflux boiler. A dilute eutectic mixture of sodium nitrate and sodium hydroxide was selected as the PCM from over 50 candidate inorganic salt mixtures. Based on a salt screening process, eight major component salts were selected initially for further evaluation. The most attractive major components in the temperature range of 250 to 350 C appeared to be NaNO3, NaNO2, and NaOH. Sketches of the two active heat exchange concepts selected for test are given.

Heat flux variations over sea ice observed at the coastal area of the Sejong Station, Antarctica

Science.gov (United States)

Park, Sang-Jong; Choi, Tae-Jin; Kim, Seong-Joong

2013-08-01

This study presents variations of sensible heat flux and latent heat flux over sea ice observed in 2011 from the 10-m flux tower located at the coast of the Sejong Station on King George Island, Antarctica. A period from July to September was selected as a sea ice period based on daily record of sea state and hourly photos looking at the Marian Cove in front of the Sejong Station. For the sea ice period, mean sensible heat flux is about -11 Wm-2, latent heat flux is about +2 W m-2, net radiation is -12 W m-2, and residual energy is -3 W m-2 with clear diurnal variations. Estimated mean values of surface exchange coefficients for momentum, heat and moisture are 5.15 × 10-3, 1.19 × 10-3, and 1.87 × 10-3, respectively. The observed exchange coefficients of heat shows clear diurnal variations while those of momentum and moisture do not show diurnal variation. The parameterized exchange coefficients of heat and moisture produces heat fluxes which compare well with the observed diurnal variations of heat fluxes.

Accounting for standard errors of vision-specific latent trait in regression models.

Science.gov (United States)

Wong, Wan Ling; Li, Xiang; Li, Jialiang; Wong, Tien Yin; Cheng, Ching-Yu; Lamoureux, Ecosse L

2014-07-11

To demonstrate the effectiveness of Hierarchical Bayesian (HB) approach in a modeling framework for association effects that accounts for SEs of vision-specific latent traits assessed using Rasch analysis. A systematic literature review was conducted in four major ophthalmic journals to evaluate Rasch analysis performed on vision-specific instruments. The HB approach was used to synthesize the Rasch model and multiple linear regression model for the assessment of the association effects related to vision-specific latent traits. The effectiveness of this novel HB one-stage "joint-analysis" approach allows all model parameters to be estimated simultaneously and was compared with the frequently used two-stage "separate-analysis" approach in our simulation study (Rasch analysis followed by traditional statistical analyses without adjustment for SE of latent trait). Sixty-six reviewed articles performed evaluation and validation of vision-specific instruments using Rasch analysis, and 86.4% (n = 57) performed further statistical analyses on the Rasch-scaled data using traditional statistical methods; none took into consideration SEs of the estimated Rasch-scaled scores. The two models on real data differed for effect size estimations and the identification of "independent risk factors." Simulation results showed that our proposed HB one-stage "joint-analysis" approach produces greater accuracy (average of 5-fold decrease in bias) with comparable power and precision in estimation of associations when compared with the frequently used two-stage "separate-analysis" procedure despite accounting for greater uncertainty due to the latent trait. Patient-reported data, using Rasch analysis techniques, do not take into account the SE of latent trait in association analyses. The HB one-stage "joint-analysis" is a better approach, producing accurate effect size estimations and information about the independent association of exposure variables with vision-specific latent traits

Influence of accuracy of thermal property data of a phase change material on the result of a numerical model of a packed bed latent heat storage with spheres

Energy Technology Data Exchange (ETDEWEB)

Arkar, C.; Medved, S. [University of Ljubljana, Faculty of Mechanical Engineering, Askerceva 6, 1000 Ljubljana (Slovenia)

2005-11-01

With the integration of latent-heat thermal energy storage (LHTES) in building services, solar energy and the coldness of ambient air can be efficiently used to reduce the energy used for heating and cooling and to improve the level of living comfort. For this purpose, a cylindrical LHTES containing spheres filled with paraffin was developed. For the proper modelling of the LHTES thermal response the thermal properties of the phase change material (PCM) must be accurately known. This article presents the influence of the accuracy of thermal property data of the PCM on the result of the prediction of the LHTES's thermal response. A packed bed numerical model was adapted to take into account the non-uniformity of the PCM's porosity and the fluid's velocity. Both are the consequence of a small tube-to-sphere diameter ratio, which is characteristic of the developed LHTES. The numerical model can also take into account the PCM's temperature-dependent thermal properties. The temperature distribution of the latent heat of the paraffin (RT20) used in the experiment in the form of apparent heat capacity was determined using a differential scanning calorimeter (DSC) at different heating and cooling rates. A comparison of the numerical and experimental results confirmed our hypothesis relating to the important role that the PCM's thermal properties play, especially during slow running processes, which are characteristic for our application.

Comparison of surface sensible and latent heat fluxes over the Tibetan Plateau from reanalysis and observations

Science.gov (United States)

Xie, Jin; Yu, Ye; Li, Jiang-lin; Ge, Jun; Liu, Chuan

2018-02-01

Surface sensible and latent heat fluxes (SH and LE) over the Tibetan Plateau (TP) have been under research since 1950s, especially for recent several years, by mainly using observation, reanalysis, and satellite data. However, the spatiotemporal changes are not consistent among different studies. This paper focuses on the spatiotemporal variation of SH and LE over the TP from 1981 to 2013 using reanalysis data sets (ERA-Interim, JRA-55, and MERRA) and observations. Results show that the spatiotemporal changes from the three reanalysis data sets are significantly different and the probable causes are discussed. Averaged for the whole TP, both SH and LE from MERRA are obviously higher than the other two reanalysis data sets. ERA-Interim shows a significant downward trend for SH and JRA-55 shows a significant increase of LE during the 33 years with other data sets having no obvious changes. By comparing the heat fluxes and some climate factors from the reanalysis with observations, it is found that the differences of heat fluxes among the three reanalysis data sets are closely related to their differences in meteorological conditions as well as the different parameterizations for surface transfer coefficients. In general, the heat fluxes from the three reanalysis have a better representation in the western TP than that in the eastern TP under inter-annual scale. While in terms of monthly variation, ERA-Interim may have better applicability in the eastern TP with dense vegetation conditions, while SH of JRA-55 and LE of MERRA are probably more representative for the middle and western TP with poor vegetation conditions.

Solar Air Heaters with Thermal Heat Storages

OpenAIRE

Saxena, Abhishek; Goel, Varun

2013-01-01

Solar energy can be converted into different forms of energy, either to thermal energy or to electrical energy. Solar energy is converted directly into electrical power by photovoltaic modules, while solar collector converts solar energy into thermal energy. Solar collector works by absorbing the direct solar radiation and converting it into thermal energy, which can be stored in the form of sensible heat or latent heat or a combination of sensible and latent heats. A theoretical study has be...

Estimating surface turbulent heat fluxes from land surface temperature and soil moisture using the particle batch smoother

Science.gov (United States)

Lu, Yang; Dong, Jianzhi; Steele-Dunne, Susan; van de Giesen, Nick

2016-04-01

This study is focused on estimating surface sensible and latent heat fluxes from land surface temperature (LST) time series and soil moisture observations. Surface turbulent heat fluxes interact with the overlying atmosphere and play a crucial role in meteorology, hydrology and other climate-related fields, but in-situ measurements are costly and difficult. It has been demonstrated that the time series of LST contains information of energy partitioning and that surface turbulent heat fluxes can be determined from assimilation of LST. These studies are mainly based on two assumptions: (1) a monthly value of bulk heat transfer coefficient under neutral conditions (CHN) which scales the sum of the fluxes, and (2) an evaporation fraction (EF) which stays constant during the near-peak hours of the day. Previous studies have applied variational and ensemble approaches to this problem. Here the newly developed particle batch smoother (PBS) algorithm is adopted to test its capability in this application. The PBS can be seen as an extension of the standard particle filter (PF) in which the states and parameters within a fix window are updated in a batch using all observations in the window. The aim of this study is two-fold. First, the PBS is used to assimilate only LST time series into the force-restore model to estimate fluxes. Second, a simple soil water transfer scheme is introduced to evaluate the benefit of assimilating soil moisture observations simultaneously. The experiments are implemented using the First ISLSCP (International Satellite Land Surface Climatology Project) (FIFE) data. It is shown that the restored LST time series using PBS agrees very well with observations, and that assimilating LST significantly improved the flux estimation at both daily and half-hourly time scales. When soil moisture is introduced to further constrain EF, the accuracy of estimated EF is greatly improved. Furthermore, the RMSEs of retrieved fluxes are effectively reduced at both

An inverse hyperbolic heat conduction problem in estimating surface heat flux by the conjugate gradient method

International Nuclear Information System (INIS)

Huang, C.-H.; Wu, H.-H.

2006-01-01

In the present study an inverse hyperbolic heat conduction problem is solved by the conjugate gradient method (CGM) in estimating the unknown boundary heat flux based on the boundary temperature measurements. Results obtained in this inverse problem will be justified based on the numerical experiments where three different heat flux distributions are to be determined. Results show that the inverse solutions can always be obtained with any arbitrary initial guesses of the boundary heat flux. Moreover, the drawbacks of the previous study for this similar inverse problem, such as (1) the inverse solution has phase error and (2) the inverse solution is sensitive to measurement error, can be avoided in the present algorithm. Finally, it is concluded that accurate boundary heat flux can be estimated in this study

Fiscal 1993 investigational report on heat pump heat storage technology; 1993 nendo heat pump chikunetsu gijutsu ni kansuru chosa hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1994-03-01

This project is for an investigation into the heat pump (HP) use heat storage technology, with the aim of clarifying the present status of HP heat storage technology, the utilization status, and the developmental trend of technology and of contributing to the spread of heat energy effective use using HP heat storage technology and to the promotion of the technical development. Accordingly, the evaluation of the following was made: sensible heat (SH), latent heat (LH), chemical heat storage technology (CH), and heat storage technology (HS). Investigations were made on the sensible heat use heat storage technology of water, brine, stone, soil, etc. in terms of SH; the phase change sensible heat use heat storage technology of ice, hydrate salt, paraffins, etc. in terms of LH; hydration, hydroxide, 2-propanol pyrolysis, adsorption of silica gel, zeolite and water, and heat storage technology using metal hydride, etc. in terms of CH. In terms of HS, the following were studied and evaluated from the study results of the heat storage system in which HP is applied to the sensible heat and latent heat type heat storage technology: contribution to the power load levelling and the reduction of heat source capacity, heat recovery and the use of unused energy, improvement of the system efficiency by combining HP and heat storage technology. 24 refs., 242 figs., 56 tabs.

The Integration of Continuous and Discrete Latent Variable Models: Potential Problems and Promising Opportunities

Science.gov (United States)

Bauer, Daniel J.; Curran, Patrick J.

2004-01-01

Structural equation mixture modeling (SEMM) integrates continuous and discrete latent variable models. Drawing on prior research on the relationships between continuous and discrete latent variable models, the authors identify 3 conditions that may lead to the estimation of spurious latent classes in SEMM: misspecification of the structural model,…

Uncertainty characterization of HOAPS 3.3 latent heat-flux-related parameters

Science.gov (United States)

Liman, Julian; Schröder, Marc; Fennig, Karsten; Andersson, Axel; Hollmann, Rainer

2018-03-01

Latent heat flux (LHF) is one of the main contributors to the global energy budget. As the density of in situ LHF measurements over the global oceans is generally poor, the potential of remotely sensed LHF for meteorological applications is enormous. However, to date none of the available satellite products have included estimates of systematic, random, and sampling uncertainties, all of which are essential for assessing their quality. Here, the challenge is taken on by matching LHF-related pixel-level data of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS) climatology (version 3.3) to in situ measurements originating from a high-quality data archive of buoys and selected ships. Assuming the ground reference to be bias-free, this allows for deriving instantaneous systematic uncertainties as a function of four atmospheric predictor variables. The approach is regionally independent and therefore overcomes the issue of sparse in situ data densities over large oceanic areas. Likewise, random uncertainties are derived, which include not only a retrieval component but also contributions from in situ measurement noise and the collocation procedure. A recently published random uncertainty decomposition approach is applied to isolate the random retrieval uncertainty of all LHF-related HOAPS parameters. It makes use of two combinations of independent data triplets of both satellite and in situ data, which are analysed in terms of their pairwise variances of differences. Instantaneous uncertainties are finally aggregated, allowing for uncertainty characterizations on monthly to multi-annual timescales. Results show that systematic LHF uncertainties range between 15 and 50 W m-2 with a global mean of 25 W m-2. Local maxima are mainly found over the subtropical ocean basins as well as along the western boundary currents. Investigations indicate that contributions from qa (U) to the overall LHF uncertainty are on the order of 60 % (25 %). From an

Análise e estimativa dos componentes do balanço de energia em ecossistema de manguezal amazônico Analysis and estimation of energy balance components in amazonian mangrove ecosystem

Directory of Open Access Journals (Sweden)

Priscila Lima Pereira

2013-03-01

Full Text Available As medições e estimativas dos componentes do balanço de energia foram feitos acima da copa das árvores no ecossistema de manguezal natural, localizada a 30 km da cidade de Bragança-PA, entre novembro de 2002 e agosto de 2003. Os dados foram utilizados para a análise das variações sazonais e horárias do fluxo de calor sensível e calor latente, bem como a avaliação da partição de energia. Os dados meteorológicos foram coletados pela estação meteorológica automática (EMA e os fluxos foram calculados utilizando-se a técnica de covariância de vórtices turbulentos. Os modelos de Penman-Monteith e Shuttleworth foram usados ​​para estimar o fluxo de calor sensível e calor latente. O objetivo deste estudo foi analisar o equilíbrio e a partição de energia no manguezal, assim como fazer uma avaliação do comportamento de modelos empíricos para estimar os fluxos de energia. O saldo de radiação apresentou valores mais elevados no período menos chuvoso. A razão de Bowen mostrou valor geralmente baixo, o que indica que uma proporção maior de energia foi utilizada sob a forma de calor latente. O modelo Shuttleworth é mais eficiente na estimativa de fluxos de calor sensível. Para estimar o fluxo de calor latente do modelo de Penman-Monteith foi mais eficiente durante a estação seca e o modelo Shuttleworth durante a estação chuvosa.Measurements and estimates of the components of energy balance were made above the canopy of trees in natural mangrove ecosystem, located 30 km from the city of Bragança-PA, between November 2002 and August 2003. The data were used in the analysis of seasonal and hourly variations of the sensible and latent heat flows, as well as the evaluation of the energy partition. Meteorological data were collected by the automatic weather station (AWS and the energy flows were calculated using the technique of eddy covariance. The Penman-Monteith and Shuttleworth models were used to estimate the

Comparison of surface energy fluxes with satellite-derived surface energy flux estimates from a shrub-steppe

International Nuclear Information System (INIS)

Kirkham, R.R.

1993-12-01

This thesis relates the components of the surface energy balance (i.e., net radiation, sensible and latent heat flux densities, soil heat flow) to remotely sensed data for native vegetation in a semi-arid environment. Thematic mapper data from Landsat 4 and 5 were used to estimate net radiation, sensible heat flux (H), and vegetation amount. Several sources of ground truth were employed. They included soil water balance using the neutron thermalization method and weighing lysimeters, and the measurement of energy fluxes with the Bowen ratio energy balance (BREB) technique. Sensible and latent heat flux were measured at four sites on the U.S. Department of Energy's Hanford Site using a weighing lysimeter and/or BREB stations. The objective was to calibrate an aerodynamic transport equation that related H to radiant surface temperature. The transport equation was then used with Landsat thermal data to generate estimates of H and compare these estimates against H values obtained with BREB/lysimeters at the time of overflight. Landsat and surface meteorologic data were used to estimate the radiation budget terms at the surface. Landsat estimates of short-wave radiation reflected from the surface correlate well with reflected radiation measured using inverted Eppley pyranometers. Correlation of net radiation estimates determined from satellite data, pyranometer, air temperature, and vapor pressure compared to net radiometer values obtained at time of overflight were excellent for a single image, but decrease for multiple images. Soil heat flux, G T , is a major component of the energy balance in arid systems and G T generally decreases as vegetation cover increases. Normalized difference vegetation index (NDVI) values generated from Landsat thermatic mapper data were representative of field observations of the presence of green vegetation, but it was not possible to determine a single relationship between NDVI and G T for all sites

Thermophysical and heat transfer properties of phase change material candidate for waste heat transportation system

Science.gov (United States)

Kaizawa, Akihide; Maruoka, Nobuhiro; Kawai, Atsushi; Kamano, Hiroomi; Jozuka, Tetsuji; Senda, Takeshi; Akiyama, Tomohiro

2008-05-01

A waste heat transportation system trans-heat (TH) system is quite attractive that uses the latent heat of a phase change material (PCM). The purpose of this paper is to study the thermophysical properties of various sugars and sodium acetate trihydrate (SAT) as PCMs for a practical TH system and the heat transfer property between PCM selected and heat transfer oil, by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA) and a heat storage tube. As a result, erythritol, with a large latent heat of 344 kJ/kg at melting point of 117°C, high decomposition point of 160°C and excellent chemical stability under repeated phase change cycles was found to be the best PCM among them for the practical TH system. In the heat release experiments between liquid erythritol and flowing cold oil, we observed foaming phenomena of encapsulated oil, in which oil droplet was coated by solidification of PCM.

Hamilton's gradient estimate for the heat kernel on complete manifolds

OpenAIRE

Kotschwar, Brett

2007-01-01

In this paper we extend a gradient estimate of R. Hamilton for positive solutions to the heat equation on closed manifolds to bounded positive solutions on complete, non-compact manifolds with $Rc \\geq -Kg$. We accomplish this extension via a maximum principle of L. Karp and P. Li and a Bernstein-type estimate on the gradient of the solution. An application of our result, together with the bounds of P. Li and S.T. Yau, yields an estimate on the gradient of the heat kernel for complete manifol...

The Relationship Between Latent Heating, Vertical Velocity, and Precipitation Processes: the Impact of Aerosols on Precipitation in Organized Deep Convective Systems

Science.gov (United States)

Tao, Wei-Kuo; Li, Xiaowen

2016-01-01

A high-resolution, two-dimensional cloud-resolving model with spectral-bin microphysics is used to study the impact of aerosols on precipitation processes in both a tropical oceanic and a midlatitude continental squall line with regard to three processes: latent heating (LH), cold pool dynamics, and ice microphysics. Evaporative cooling in the lower troposphere is found to enhance rainfall in low cloud condensation nuclei (CCN) concentration scenarios in the developing stages of a midlatitude convective precipitation system. In contrast, the tropical case produced more rainfall under high CCN concentrations. Both cold pools and low-level convergence are stronger for those configurations having enhanced rainfall. Nevertheless, latent heat release is stronger (especially after initial precipitation) in the scenarios having more rainfall in both the tropical and midlatitude environment. Sensitivity tests are performed to examine the impact of ice and evaporative cooling on the relationship between aerosols, LH, and precipitation processes. The results show that evaporative cooling is important for cold pool strength and rain enhancement in both cases. However, ice microphysics play a larger role in the midlatitude case compared to the tropics. Detailed analysis of the vertical velocity-governing equation shows that temperature buoyancy can enhance updraftsdowndrafts in the middlelower troposphere in the convective core region; however, the vertical pressure gradient force (PGF) is of the same order and acts in the opposite direction. Water loading is small but of the same order as the net PGF-temperature buoyancy forcing. The balance among these terms determines the intensity of convection.

Latent fingermark development using low-vacuum vaporization of ninhydrin.

Science.gov (United States)

Chen, Chun-Chieh; Yang, Chao-Kai; Liao, Jeh-Shane; Wang, Sheng-Meng

2015-12-01

The vacuum technique is a method of vaporizing a solid material to its gas phase, helping deposit reagents gently on target surfaces to develop latent fingermarks. However, this application is rarely reported in the literature. In this study, a homemade fume hood with a built-in vacuum control system and programmable heating system designed by the Taiwan Criminal Investigation Bureau is introduced. Factors that affect the instrument's performance in developing fingermarks are discussed, including the quantity of chemicals for vaporization, heating program arrangement, and paper of different materials. The results show that fingermarks are effectively developed by vaporizing solid ninhydrin. This would be an alternative application in selecting a solvent-free method for protecting the environment and reducing health hazards in the lab. In terms of the heating program, the result indicates that under a low-vacuum condition (50 mTorr), 80-90 °C is a suitable temperature range for ninhydrin vaporization, allowing ninhydrin to be vaporized without bumping and waste. In terms of the performance on different material papers, this instrument demonstrates its capacity by developing latent fingermarks on thermal paper without discoloration or damaging the original writing, and the same results are also observed on Taiwan and United States banknotes. However, a coherent result could be hardly obtained using the same vaporization setting because different banknotes have their own surface features and water absorption ability or other unique factors may influence the effect of ninhydrin deposition. This study provides a reliable application for developing latent fingermarks without using solvents, and it is also expected to contribute to environmental protection along with the trend of green chemistry technology. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Evaporation estimation of rift valley lakes: comparison of models.

Science.gov (United States)

Melesse, Assefa M; Abtew, Wossenu; Dessalegne, Tibebe

2009-01-01

Evapotranspiration (ET) accounts for a substantial amount of the water flux in the arid and semi-arid regions of the World. Accurate estimation of ET has been a challenge for hydrologists, mainly because of the spatiotemporal variability of the environmental and physical parameters governing the latent heat flux. In addition, most available ET models depend on intensive meteorological information for ET estimation. Such data are not available at the desired spatial and temporal scales in less developed and remote parts of the world. This limitation has necessitated the development of simple models that are less data intensive and provide ET estimates with acceptable level of accuracy. Remote sensing approach can also be applied to large areas where meteorological data are not available and field scale data collection is costly, time consuming and difficult. In areas like the Rift Valley regions of Ethiopia, the applicability of the Simple Method (Abtew Method) of lake evaporation estimation and surface energy balance approach using remote sensing was studied. The Simple Method and a remote sensing-based lake evaporation estimates were compared to the Penman, Energy balance, Pan, Radiation and Complementary Relationship Lake Evaporation (CRLE) methods applied in the region. Results indicate a good correspondence of the models outputs to that of the above methods. Comparison of the 1986 and 2000 monthly lake ET from the Landsat images to the Simple and Penman Methods show that the remote sensing and surface energy balance approach is promising for large scale applications to understand the spatial variation of the latent heat flux.

Evaporation Estimation of Rift Valley Lakes: Comparison of Models

Directory of Open Access Journals (Sweden)

Tibebe Dessalegne

2009-12-01

Full Text Available Evapotranspiration (ET accounts for a substantial amount of the water flux in the arid and semi-arid regions of the World. Accurate estimation of ET has been a challenge for hydrologists, mainly because of the spatiotemporal variability of the environmental and physical parameters governing the latent heat flux. In addition, most available ET models depend on intensive meteorological information for ET estimation. Such data are not available at the desired spatial and temporal scales in less developed and remote parts of the world. This limitation has necessitated the development of simple models that are less data intensive and provide ET estimates with acceptable level of accuracy. Remote sensing approach can also be applied to large areas where meteorological data are not available and field scale data collection is costly, time consuming and difficult. In areas like the Rift Valley regions of Ethiopia, the applicability of the Simple Method (Abtew Method of lake evaporation estimation and surface energy balance approach using remote sensing was studied. The Simple Method and a remote sensing-based lake evaporation estimates were compared to the Penman, Energy balance, Pan, Radiation and Complementary Relationship Lake Evaporation (CRLE methods applied in the region. Results indicate a good correspondence of the models outputs to that of the above methods. Comparison of the 1986 and 2000 monthly lake ET from the Landsat images to the Simple and Penman Methods show that the remote sensing and surface energy balance approach is promising for large scale applications to understand the spatial variation of the latent heat flux.

Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin

Science.gov (United States)

Zeng, Yujin; Xie, Zhenghui; Liu, Shuang

2017-02-01

Irrigation, which constitutes ˜ 70 % of the total amount of freshwater consumed by the human population, is significantly impacting land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM4.5) with an active crop model, two high-resolution (˜ 1 km) simulations investigating the effects of irrigation on latent heat (LH), sensible heat (SH), and carbon fluxes (or net ecosystem exchange, NEE) from land to atmosphere in the Heihe River basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity of the developed models to reproduce ecological and hydrological processes. The results revealed that the effects of irrigation on LH and SH are strongest during summer, with a LH increase of ˜ 100 W m-2 and a SH decrease of ˜ 60 W m-2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate is below 5 mm day-1, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm day-1, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC m-2 day-1, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by ˜ 0.8 gC m-2 day-1. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH, and NEE.

Interferon-gamma release assay for the diagnosis of latent tuberculosis infection: A latent-class analysis.

Directory of Open Access Journals (Sweden)

Tan N Doan

Full Text Available Accurate diagnosis and subsequent treatment of latent tuberculosis infection (LTBI is essential for TB elimination. However, the absence of a gold standard test for diagnosing LTBI makes assessment of the true prevalence of LTBI and the accuracy of diagnostic tests challenging. Bayesian latent class models can be used to make inferences about disease prevalence and the sensitivity and specificity of diagnostic tests using data on the concordance between tests. We performed the largest meta-analysis to date aiming to evaluate the performance of tuberculin skin test (TST and interferon-gamma release assays (IGRAs for LTBI diagnosis in various patient populations using Bayesian latent class modelling.Systematic search of PubMeb, Embase and African Index Medicus was conducted without date and language restrictions on September 11, 2017 to identify studies that compared the performance of TST and IGRAs for LTBI diagnosis. Two IGRA methods were considered: QuantiFERON-TB Gold In Tube (QFT-GIT and T-SPOT.TB. Studies were included if they reported 2x2 agreement data between TST and QFT-GIT or T-SPOT.TB. A Bayesian latent class model was developed to estimate the sensitivity and specificity of TST and IGRAs in various populations, including immune-competent adults, immune-compromised adults and children. A TST cut-off value of 10 mm was used for immune-competent subjects and 5 mm for immune-compromised individuals.A total of 157 studies were included in the analysis. In immune-competent adults, the sensitivity of TST and QFT-GIT were estimated to be 84% (95% credible interval [CrI] 82-85% and 52% (50-53%, respectively. The specificity of QFT-GIT was 97% (96-97% in non-BCG-vaccinated and 93% (92-94% in BCG-vaccinated immune-competent adults. The estimated figures for TST were 100% (99-100% and 79% (76-82%, respectively. T-SPOT.TB has comparable specificity (97% for both tests and better sensitivity (68% versus 52% than QFT-GIT in immune-competent adults

A Composite Likelihood Inference in Latent Variable Models for Ordinal Longitudinal Responses

Science.gov (United States)

Vasdekis, Vassilis G. S.; Cagnone, Silvia; Moustaki, Irini

2012-01-01

The paper proposes a composite likelihood estimation approach that uses bivariate instead of multivariate marginal probabilities for ordinal longitudinal responses using a latent variable model. The model considers time-dependent latent variables and item-specific random effects to be accountable for the interdependencies of the multivariate…

Long-term heat storage in calcium sulfoaluminate cement (CSA) based concrete

Energy Technology Data Exchange (ETDEWEB)

Kaufmann, Josef P.; Winnefeld, Frank [Empa Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland). Lab. for Concrete and Construction Chemistry

2011-07-01

In general, the selection of materials proposed for solar heat storage is based on one of two principal processes: sensible heat storage or latent heat storage. Sensible heat storage utilizes the specific heat capacity of a material, while latent heat storage is based on the change in enthalpy (heat content) associated with a phase change of the material. Long time sensible heat storage requires excellent thermal insulation whereas latent heat storage allows permanent (seasonal) storage without significant energy losses and any special insulation. Ettringite, one of the cement hydration products, exhibits a high dehydration enthalpy. Calcium sulfoaluminate cement based concrete containing a high amount of ettringite is henceproposed as an efficient latent heat storage material. Compared to conventional heat storage materials this innovative concrete mixture has a high loss-free storage energy density (> 100-150 kWh/m{sup 3}) which is much higher than the one of paraffin or the (loss-sensitive) sensible heat of water. Like common concrete the CSA-concrete is stable and even may carry loads. The dehydration of the CSA-concrete is achieved at temperatures below 100 C. The rehydration process occurs as soon as water (liquid or vapor) is added. In contrast to paraffin, the phase change temperature is not fixed and the latent heat may be recovered at any desired temperature. Furthermore the heat conductivity of this material is high, so that the energy transfer from/to an exchange medium is easy. Additionally CSA-concrete is not flammable and absolutely safe regarding any health aspects. The cost of such CSA-concrete isin the order of normal concrete. The main application is seen in house heating systems. Solar heat, mostly generated during the summer period by means of roof collectors, can be stored in CSA-concrete until the winter. A part or even the whole annual heatingenergy may be produced and saved locally by the householder himself. Additional applications may be

Residual stresses estimation in tubes after rapid heating of surface

International Nuclear Information System (INIS)

Serikov, S.V.

1992-01-01

Results are presented on estimation of residual stresses in tubes of steel types ShKh15, EhP836 and 12KIMF after heating by burning pyrotechnic substance inside tubes. External tube surface was heated up to 400-450 deg C under such treatment. Axial stresses distribution over tube wall thickness was determined for initial state, after routine heat treatment and after heating with the use of fireworks. Inner surface heating was shown to essentially decrease axial stresses in tubes

Heat flux variations over sea-ice observed at the coastal area of the Sejong Station, Antarctica

Science.gov (United States)

Park, S.; Choi, T.; Kim, S.

2012-12-01

This study presents variations of sensible heat flux and latent heat flux over sea-ice observed in 2011 from the 10-m flux tower located at the coast of the Sejong Station on King George Island, Antarctica. A period from June to November was divided into three parts: "Freezing", "Frozen", and "Melting" periods based on daily monitoring of sea state and hourly photos looking at the Marian Cove in front of the Sejong Station. The division of periods enabled us to look into the heat flux variations depending on the sea-ice conditions. Over freezing sea surface during the freezing period of late June, daily mean sensible heat flux was -11.9 Wm-2 and daily mean latent heat flux was +16.3 Wm-2. Over the frozen sea-ice, daily mean sensible heat flux was -10.4 Wm-2 while daily mean latent heat flux was +2.4 Wm-2. During the melting period of mid-October to early November, magnitudes of sensible heat flux increased to -14.2 Wm-2 and latent heat flux also increased to +13.5 Wm-2. In short, latent heat flux was usually upward over sea-ice most of the time while sensible heat flux was downward from atmosphere to sea-ice. Magnitudes of the fluxes were small but increased when freezing or melting of sea-ice was occurring. Especially, latent heat flux increased five to six times compared to that of "frozen" period implying that early melting of sea-ice may cause five to six times larger supply of moisture to the atmosphere.

Recov'Heat: An estimation tool of urban waste heat recovery potential in sustainable cities

Science.gov (United States)

Goumba, Alain; Chiche, Samuel; Guo, Xiaofeng; Colombert, Morgane; Bonneau, Patricia

2017-02-01

Waste heat recovery is considered as an efficient way to increase carbon-free green energy utilization and to reduce greenhouse gas emission. Especially in urban area, several sources such as sewage water, industrial process, waste incinerator plants, etc., are still rarely explored. Their integration into a district heating system providing heating and/or domestic hot water could be beneficial for both energy companies and local governments. EFFICACITY, a French research institute focused on urban energy transition, has developed an estimation tool for different waste heat sources potentially explored in a sustainable city. This article presents the development method of such a decision making tool which, by giving both energetic and economic analysis, helps local communities and energy service companies to make preliminary studies in heat recovery projects.

High performance passive solar heating system with heat pipe energy transfer and latent heat storage

NARCIS (Netherlands)

Dijk, van H.A.L.; Galen, van E; Hensen, J.L.M.; Wit, de M.H.

1983-01-01

Preliminar results are reported from a current project on the development of a high performance passive solar heating system. Two special components are introduced: a. A heat pipe as a thermal diode tube for the efficient transfer of collected solar heat from the absorber plate to behind an

Influence of nanomaterials on properties of latent heat solar thermal energy storage materials – A review

International Nuclear Information System (INIS)

Raam Dheep, G.; Sreekumar, A.

2014-01-01

Highlights: • Classification of phase change materials. • Studies on phase change properties of various phase change materials. • Influence of nanomaterials on properties of phase change materials. - Abstract: Thermal energy storage system plays a critical role in developing an efficient solar energy device. As far as solar thermal devices are concerned, there is always a mismatch between supply and demand due to intermittent and unpredictable nature of solar radiation. A well designed thermal energy storage system is capable to alleviate this demerit by providing a constant energy delivery to the load. Many research works is being carried out to determine the suitability of thermal energy storage system to integrate with solar thermal gadgets. This review paper summarizes the numerous investigations on latent heat thermal energy storage using phase change materials (PCM) and its classification, properties, selection criteria, potential research areas and studies involved to analyze the thermal–physical properties of PCM

Latent heat increases storage capacity. Heat transport by truck; Latente warmte vergroot opslagcapaciteit. Warmtetransport per vrachtauto is soms heel slim

Energy Technology Data Exchange (ETDEWEB)

De Jong, K.

2012-11-15

The project-group Biomass CHP (combined production of heat and power) organized a tour with a workshop in Dortmund, Germany, September 26, 2012, on storage and transport of heat and biogas. There are several projects in Germany involving road transport of heat by means of containers. A swimming pool in Dortmund already is using this option since 2008. Waste heat from a CHP-installation for landfill gas is collected from a waste dump [Dutch] De projectgroep Biomassa en WKK organiseerde 26 September een excursie met workshop in Dortmund over opslag en transport van warmte en biogas. Er zijn in Duitsland al meerdere projecten waarbij warmte per container over de weg wordt vervoerd. Een Dortmunds zwembad werkt hier al sinds 2008 mee. De restwarmte van een wkk op stortgas wordt opgehaald bij een afvalstortplaats.

Linear latent variable models: the lava-package

DEFF Research Database (Denmark)

Holst, Klaus Kähler; Budtz-Jørgensen, Esben

2013-01-01

are implemented including robust standard errors for clustered correlated data, multigroup analyses, non-linear parameter constraints, inference with incomplete data, maximum likelihood estimation with censored and binary observations, and instrumental variable estimators. In addition an extensive simulation......An R package for specifying and estimating linear latent variable models is presented. The philosophy of the implementation is to separate the model specification from the actual data, which leads to a dynamic and easy way of modeling complex hierarchical structures. Several advanced features...

Confidence Intervals for a Semiparametric Approach to Modeling Nonlinear Relations among Latent Variables

Science.gov (United States)

Pek, Jolynn; Losardo, Diane; Bauer, Daniel J.

2011-01-01

Compared to parametric models, nonparametric and semiparametric approaches to modeling nonlinearity between latent variables have the advantage of recovering global relationships of unknown functional form. Bauer (2005) proposed an indirect application of finite mixtures of structural equation models where latent components are estimated in the…

Experimental and numerical investigation of a tube-in-tank latent thermal energy storage unit using composite PCM

International Nuclear Information System (INIS)

Meng, Z.N.; Zhang, P.

2017-01-01

Highlights: • A tube-in-tank latent thermal energy storage (LTES) unit using composite PCM is built. • Thermal performances of the LTES unit are experimentally and numerically studied. • Thermal performances of the LTES unit under different operation conditions are comparatively studied. • A 3D numerical model is established to study the heat transfer mechanisms of the LTES unit. - Abstract: Paraffin is a commonly used phase change material (PCM) which has been frequently applied for thermal energy storage. A tube-in-tank latent thermal energy storage (LTES) unit using paraffin as PCM is built in the present study, which can be used in many applications. In order to enhance the thermal performance of the LTES unit, the composite PCM is fabricated by embedding copper foam into pure paraffin. The performances of the LTES unit with the composite PCM during the heat charging and discharging processes are investigated experimentally, and a series of experiments are carried out under different inlet temperatures and inlet flow velocities of the heat transfer fluid (HTF). The temperature evolutions of the LTES unit are obtained during the experiments, and the time-durations, mean powers and energy efficiencies are estimated to evaluate the performance of the LTES unit. Meanwhile, a three-dimensional (3D) mathematical model based on enthalpy-porosity and melting/solidification models is established to investigate the heat transfer mechanisms of the LTES unit and the detailed heat transfer characteristics of the LTES unit are obtained. It can be concluded that the LTES unit with the composite PCM shows good heat transfer performance, and larger inlet flow velocity of the HTF and larger temperature difference between the HTF and PCM can enhance the heat transfer and benefit the thermal energy utilization. Furthermore, a LTES system with larger thermal energy storage capacity can be easily assembled by several such LTES units, which can meet versatile demands in

Latent Class Analysis of Criminal Social Identity in a Prison Sample

Directory of Open Access Journals (Sweden)

Boduszek Daniel

2014-06-01

Full Text Available This study aimed to examine the number of latent classes of criminal social identity that exist among male recidivistic prisoners. Latent class analysis was used to identify homogeneous groups of criminal social identity. Multinomial logistic regression was used to interpret the nature of the latent classes, or groups, by estimating the associationsto number of police arrests, recidivism, and violent offending while controlling for current age. The best fitting latent class model was a five-class solution: ‘High criminal social identity’ (17%, ‘High Centrality, Moderate Affect, Low Ties’ (21.7%, ‘Low Centrality, Moderate Affect, High Ties’ (13.3%,‘Low Cognitive, High Affect, Low Ties’ (24.6%, and ‘Low criminal social identity’ (23.4%. Each of the latent classes was predicted by differing external variables. Criminal social identity is best explained by five homogenous classes that display qualitative and quantitative differences.

Latent tuberculosis in nursing professionals of a Brazilian hospital

Directory of Open Access Journals (Sweden)

Valim Andréia

2011-05-01

Full Text Available Abstract Tuberculosis (TB is considered an occupational disease among health-care workers (HCWs. Direct contact with TB patients leads to an increased risk to become latently infected by Mycobacterium tuberculosis. The objective of this study is to estimate the prevalence of latent M. tuberculosis minfection among nursing professionals of a hospital in Rio Grande do Sul, Brazil, assessed by tuberculin skin test (TST. From November 2009 to May 2010, latent M. tuberculosis infection was assessed by TST in 55 nursing professionals. Epidemiological information was collected using a standardized questionnaire. A positive TST result (> or = 10 mm was observed in 47.3% of the HCWs tested. There was no significant difference in TST positivity when duration of employment or professional category (technician or nurse was evaluated. The results of this work reinforce the need for control measures to prevent latent M. tuberculosis infection among nursing professionals at the hospital where the study was conducted.

Inverse heat transfer analysis of a functionally graded fin to estimate time-dependent base heat flux and temperature distributions

International Nuclear Information System (INIS)

Lee, Haw-Long; Chang, Win-Jin; Chen, Wen-Lih; Yang, Yu-Ching

2012-01-01

Highlights: ► Time-dependent base heat flux of a functionally graded fin is inversely estimated. ► An inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied. ► The distributions of temperature in the fin are determined as well. ► The influence of measurement error and measurement location upon the precision of the estimated results is also investigated. - Abstract: In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown time-dependent base heat flux of a functionally graded fin from the knowledge of temperature measurements taken within the fin. Subsequently, the distributions of temperature in the fin can be determined as well. It is assumed that no prior information is available on the functional form of the unknown base heat flux; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors and measurement location upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent base heat flux and temperature distributions can be obtained for the test case considered in this study.

Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat and carbon fluxes in semi-arid basin

Science.gov (United States)

Xie, Zhenghui; Zeng, Yujin

2017-04-01

Irrigation, which constitutes 70% of the total amount of fresh water consumed by the human population, is significantly impacting the land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM 4.5) with an active crop model, two high resolution ( 1 km) simulations investigating the effects of irrigation on Latent Heat (LH), Sensible Heat (SH) and Carbon Fluxes (or net ecosystem exchange, NEE) from land to atmosphere on the Heihe River Basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity and viability of the developed models to reproduce ecological and hydrological processes. The results revealed the effects of irrigation on LH and SH are strongest during summer with a LH increase of 100 W/m2 and a SH decrease of 60 W/m2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate below 5 mm/day, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm/day, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC/m2/day, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by 0.8 gC/m2/day. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH and NEE. The study indicates that how a land surface model with high spatial resolution can represent crop growing and its effects over basin scale.

Studies on heat storage, 9

International Nuclear Information System (INIS)

Taoda, Hiroshi; Hayakawa, Kiyoshi; Kawase, Kaoru; Kosaka, Mineo

1985-01-01

To estimate the extent of thermal oxidative aging of the crosslinked and surface coated polyethylene pellets used as a latent heat thermal storage material, their deterioration was investigated by applying the heating-cooling cycle which simulated the daily insolation over 6 months (8-hour holding at 150 deg C as the highest temperature in a day followed by 5-hour holding at 30 deg C as the lowest one). The degradation, e.g., the lowering of heat of crystallization and in crystallization temperature, is thought to be caused by both the decrease in molecular weight of polyethylene due to thermal oxidative decomposition and the crosslinking between produced radicals. With the increase in the degree of crosslinking and branching in a molecular chain which has low bond dissociation energy, thermal deterioration of polyethylene proceeds more rapidly. Polyethylene pellets can endure long periods of practical heat cycling as a thermal storage material when they are treated with radical scavengers under proper control of their crosslinking degrees. The repeating heat storage experiments by using the developed polyethylene thermal storage material were performed and very promising results were obtained. (author)

Cryogenic heat transfer

CERN Document Server

Barron, Randall F

2016-01-01

Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.

Estimating surface fluxes over the north Tibetan Plateau area with ASTER imagery

Directory of Open Access Journals (Sweden)

Weiqiang Ma

2009-01-01

Full Text Available Surface fluxes are important boundary conditions for climatological modeling and Asian monsoon system. The recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection radiometer sensor has enabled us to estimate surface fluxes to bridge the gap between local scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A parameterization method based on ASTER data and field observations has been proposed and tested for deriving surface albedo, surface temperature, Normalized Difference Vegetation Index (NDVI, Modified Soil Adjusted Vegetation Index (MSAVI, vegetation coverage, Leaf Area Index (LAI, net radiation flux, soil heat flux, sensible heat flux and latent heat flux over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the Coordinated Enhanced Observing Period (CEOP Asia-Australia Monsoon Project (CAMP on the Tibetan Plateau (CAMP/Tibet, located at the north Tibetan Plateau. The ASTER data of 24 July 2001, 29 November 2001 and 12 March 2002 was used in this paper for the case of summer, winter and spring. To validate the proposed methodology, the ground-measured surface variables (surface albedo and surface temperature and land surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in three different months over the study area are in good accordance with the land surface status. Also, the estimated land surface variables and land surface heat fluxes are in good accordance with ground measurements, and all their absolute percentage difference (APD is less than 10% in the validation sites

Simple future weather files for estimating heating and cooling demand

DEFF Research Database (Denmark)

Cox, Rimante Andrasiunaite; Drews, Martin; Rode, Carsten

2015-01-01

useful estimates of future energy demand of a building. Experimental results based on both the degree-day method and dynamic simulations suggest that this is indeed the case. Specifically, heating demand estimates were found to be within a few per cent of one another, while estimates of cooling demand...... were slightly more varied. This variation was primarily due to the very few hours of cooling that were required in the region examined. Errors were found to be most likely when the air temperatures were close to the heating or cooling balance points, where the energy demand was modest and even...... relatively large errors might thus result in only modest absolute errors in energy demand....

Estimating Antarctic Geothermal Heat Flux using Gravity Inversion

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V.; Sasha Rogozhina, Irina

2013-04-01

Geothermal heat flux (GHF) in Antarctica is very poorly known. We have determined (Vaughan et al. 2012) top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008). Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Knowing GHF distribution for East Antarctica and the Gamburtsev Subglacial Mountains (GSM) region in particular is critical because: 1) The GSM likely acted as key nucleation point for the East Antarctic Ice Sheet (EAIS); 2) the region may contain the oldest ice of the EAIS - a prime target for future ice core drilling; 3) GHF is important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). An integrated multi-dataset-based GHF model for East Antarctica is planned that will resolve the wide range of estimates previously published using single datasets. The new map and existing GHF distribution estimates available for Antarctica will be evaluated using direct ice temperature measurements obtained from deep ice cores, estimates of GHF derived from subglacial lakes, and a thermodynamic ice-sheet model of the Antarctic Ice Sheet driven by past climate reconstructions and each of analysed heat flow maps, as has recently been done for the Greenland region (Rogozhina et al. 2012). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N

Association between latent toxoplasmosis and cognition in adults: a cross-sectional study.

Science.gov (United States)

Gale, S D; Brown, B L; Erickson, L D; Berrett, A; Hedges, D W

2015-04-01

Latent infection from Toxoplasma gondii (T. gondii) is widespread worldwide and has been associated with cognitive deficits in some but not all animal models and in humans. We tested the hypothesis that latent toxoplasmosis is associated with decreased cognitive function in a large cross-sectional dataset, the National Health and Nutrition Examination Survey (NHANES). There were 4178 participants aged 20-59 years, of whom 19.1% had IgG antibodies against T. gondii. Two ordinary least squares (OLS) regression models adjusted for the NHANES complex sampling design and weighted to represent the US population were estimated for simple reaction time, processing speed and short-term memory or attention. The first model included only main effects of latent toxoplasmosis and demographic control variables, and the second added interaction terms between latent toxoplasmosis and the poverty-to-income ratio (PIR), educational attainment and race-ethnicity. We also used multivariate models to assess all three cognitive outcomes in the same model. Although the models evaluating main effects only demonstrated no association between latent toxoplasmosis and the cognitive outcomes, significant interactions between latent toxoplasmosis and the PIR, between latent toxoplasmosis and educational attainment, and between latent toxoplasmosis and race-ethnicity indicated that latent toxoplasmosis may adversely affect cognitive function in certain groups.

Evapotranspiration and heat fluxes over a small forest - a study using modelling and measurements

DEFF Research Database (Denmark)

Sogachev, Andrey; Dellwik, Ebba; Boegh, Eva

2013-01-01

are very often used for calibration of forest parameters or model constants, further use of these parameters without a proper interpretation in mesoscale or global circulation models can result in serious bias of estimates of modelled evapotranspiration or heat fluxes from the given area. In the present...... work, we apply the atmospheric boundary layer (ABL) model SCADIS with enhanced turbulence closure including buoyancy for investigation of the spatial distribution of latent and sensible heat vertical fluxes over patchy forested terrain in Denmark during selected days in the summer period. The approach...

Bayesian leave-one-out cross-validation approximations for Gaussian latent variable models

DEFF Research Database (Denmark)

Vehtari, Aki; Mononen, Tommi; Tolvanen, Ville

2016-01-01

The future predictive performance of a Bayesian model can be estimated using Bayesian cross-validation. In this article, we consider Gaussian latent variable models where the integration over the latent values is approximated using the Laplace method or expectation propagation (EP). We study...... the properties of several Bayesian leave-one-out (LOO) cross-validation approximations that in most cases can be computed with a small additional cost after forming the posterior approximation given the full data. Our main objective is to assess the accuracy of the approximative LOO cross-validation estimators...

Prevalence of latent Mycobacterium tuberculosis infection among professionals of the primary healthcare network

Directory of Open Access Journals (Sweden)

Tássia Silvana Borges

2014-06-01

Full Text Available Objective: To estimate the prevalence of latent M. tuberculosis infection and identify characteristics related to latent infection among workers of the primary healthcare network.Methods: Cross-sectional, observational and descriptive study, conducted in 2011, included 137 basic health workers who performed their activities in a municipality. Interviews were carried out addressing characteristics of exposure at work (BCG vaccination, length of time working in the health system, potential exposure to tuberculosis, HIV infection, use of corticosteroids, diabetes, use of tobacco or alcohol and subsequently performed tuberculin skin test (TST. Data was analyzed with Fischer and Student’s t-test (p < 0.05. Results: Health professionals were mostly women (n=126, 92% with mean age of 35.3 (± 9.1 years. Among the reactors, 25 (55.5% sought medical care, and of these, 7 (28% underwent prophylactic treatment. The prevalence of latent tuberculosis was 32.8%. Of the characteristics evaluated, only smoking (OR 3.03; 95%CI 1.05-8.77 was associated with latent infection. Conclusion: The estimated prevalence of latent M. tuberculosis infection among the evaluated health workers was 32.8%. As for the characteristics studied, it was not possible to relate them to latent infection among workers in primary healthcare network, with the exception of the smoking habit. doi: 10.5020/18061230.2014.p269

Estimating spatially distributed turbulent heat fluxes from high-resolution thermal imagery acquired with a UAV system.

Science.gov (United States)

Brenner, Claire; Thiem, Christina Elisabeth; Wizemann, Hans-Dieter; Bernhardt, Matthias; Schulz, Karsten

2017-05-19

In this study, high-resolution thermal imagery acquired with a small unmanned aerial vehicle (UAV) is used to map evapotranspiration (ET) at a grassland site in Luxembourg. The land surface temperature (LST) information from the thermal imagery is the key input to a one-source and two-source energy balance model. While the one-source model treats the surface as a single uniform layer, the two-source model partitions the surface temperature and fluxes into soil and vegetation components. It thus explicitly accounts for the different contributions of both components to surface temperature as well as turbulent flux exchange with the atmosphere. Contrary to the two-source model, the one-source model requires an empirical adjustment parameter in order to account for the effect of the two components. Turbulent heat flux estimates of both modelling approaches are compared to eddy covariance (EC) measurements using the high-resolution input imagery UAVs provide. In this comparison, the effect of different methods for energy balance closure of the EC data on the agreement between modelled and measured fluxes is also analysed. Additionally, the sensitivity of the one-source model to the derivation of the empirical adjustment parameter is tested. Due to the very dry and hot conditions during the experiment, pronounced thermal patterns developed over the grassland site. These patterns result in spatially variable turbulent heat fluxes. The model comparison indicates that both models are able to derive ET estimates that compare well with EC measurements under these conditions. However, the two-source model, with a more complex treatment of the energy and surface temperature partitioning between the soil and vegetation, outperformed the simpler one-source model in estimating sensible and latent heat fluxes. This is consistent with findings from prior studies. For the one-source model, a time-variant expression of the adjustment parameter (to account for the difference between

The physical properties of Santowax 'R' for heat transfer calculations (AERE R/M 183 revised)

International Nuclear Information System (INIS)

Bowring, R.W.; Garton, D.A.; Kinneir, J.H.

1961-03-01

Values of the following physical properties of Santowax 'R' are presented in graphical and/or tabular form in both English and Metric units: Vapour Pressure, Specific heat, Enthalpy, Density, Dynamic viscosity, Kinematic viscosity, Thermal conductivity, Prandtl number, Surface tension, Latent heat of vaporisation, Critical properties, Gas solubilities. The data were obtained by new experimental measurements, by calculation or from the published literature. Wherever possible an estimate of the probable error is given. Conversion factors and Tables are also presented to facilitate the conversion of any of the properties to convenient units required for calculations. (author)

A combined ANN-GA and experimental based technique for the estimation of the unknown heat flux for a conjugate heat transfer problem

Science.gov (United States)

M K, Harsha Kumar; P S, Vishweshwara; N, Gnanasekaran; C, Balaji

2018-05-01

The major objectives in the design of thermal systems are obtaining the information about thermophysical, transport and boundary properties. The main purpose of this paper is to estimate the unknown heat flux at the surface of a solid body. A constant area mild steel fin is considered and the base is subjected to constant heat flux. During heating, natural convection heat transfer occurs from the fin to ambient. The direct solution, which is the forward problem, is developed as a conjugate heat transfer problem from the fin and the steady state temperature distribution is recorded for any assumed heat flux. In order to model the natural convection heat transfer from the fin, an extended domain is created near the fin geometry and air is specified as a fluid medium and Navier Stokes equation is solved by incorporating the Boussinesq approximation. The computational time involved in executing the forward model is then reduced by developing a neural network (NN) between heat flux values and temperatures based on back propagation algorithm. The conjugate heat transfer NN model is now coupled with Genetic algorithm (GA) for the solution of the inverse problem. Initially, GA is applied to the pure surrogate data, the results are then used as input to the Levenberg- Marquardt method and such hybridization is proven to result in accurate estimation of the unknown heat flux. The hybrid method is then applied for the experimental temperature to estimate the unknown heat flux. A satisfactory agreement between the estimated and actual heat flux is achieved by incorporating the hybrid method.

Inverse Estimation of Heat Flux and Temperature Distribution in 3D Finite Domain

International Nuclear Information System (INIS)

Muhammad, Nauman Malik

2009-02-01

Inverse heat conduction problems occur in many theoretical and practical applications where it is difficult or practically impossible to measure the input heat flux and the temperature of the layer conducting the heat flux to the body. Thus it becomes imperative to devise some means to cater for such a problem and estimate the heat flux inversely. Adaptive State Estimator is one such technique which works by incorporating the semi-Markovian concept into a Bayesian estimation technique thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters. The problem presented in this study deals with a three dimensional system of a cube with one end conducting heat flux and all the other sides are insulated while the temperatures are measured on the accessible faces of the cube. The measurements taken on these accessible faces are fed into the estimation algorithm and the input heat flux and the temperature distribution at each point in the system is calculated. A variety of input heat flux scenarios have been examined to underwrite the robustness of the estimation algorithm and hence insure its usability in practical applications. These include sinusoidal input flux, a combination of rectangular, linearly changing and sinusoidal input flux and finally a step changing input flux. The estimator's performance limitations have been examined in these input set-ups and error associated with each set-up is compared to conclude the realistic application of the estimation algorithm in such scenarios. Different sensor arrangements, that is different sensor numbers and their locations are also examined to impress upon the importance of number of measurements and their location i.e. close or farther from the input area. Since practically it is both economically and physically tedious to install more number of measurement sensors, hence optimized number and location is very important to determine for making the study more

Methodology for estimation of potential for solar water heating in a target area

International Nuclear Information System (INIS)

Pillai, Indu R.; Banerjee, Rangan

2007-01-01

Proper estimation of potential of any renewable energy technology is essential for planning and promotion of the technology. The methods reported in literature for estimation of potential of solar water heating in a target area are aggregate in nature. A methodology for potential estimation (technical, economic and market potential) of solar water heating in a target area is proposed in this paper. This methodology links the micro-level factors and macro-level market effects affecting the diffusion or adoption of solar water heating systems. Different sectors with end uses of low temperature hot water are considered for potential estimation. Potential is estimated at each end use point by simulation using TRNSYS taking micro-level factors. The methodology is illustrated for a synthetic area in India with an area of 2 sq. km and population of 10,000. The end use sectors considered are residential, hospitals, nursing homes and hotels. The estimated technical potential and market potential are 1700 m 2 and 350 m 2 of collector area, respectively. The annual energy savings for the technical potential in the area is estimated as 110 kW h/capita and 0.55 million-kW h/sq. km. area, with an annual average peak saving of 1 MW. The annual savings is 650-kW h per m 2 of collector area and accounts for approximately 3% of the total electricity consumption of the target area. Some of the salient features of the model are the factors considered for potential estimation; estimation of electrical usage pattern for typical day, amount of electricity savings and savings during the peak load. The framework is general and enables accurate estimation of potential of solar water heating for a city, block. Energy planners and policy makers can use this framework for tracking and promotion of diffusion of solar water heating systems. (author)

Latent factors and route choice behaviour

DEFF Research Database (Denmark)

Prato, Carlo Giacomo

. A reliable dataset was prepared through measures of internal consistency and sampling adequacy, and data were analyzed with a proper application of factor analysis to the route choice context. For the dataset obtained from the survey, six latent constructs affecting driver behaviour were extracted and scores...... on each factor for each survey participant were calculated. Path generation algorithms were examined with respect to observed behaviour, through a measure of reproduction with deterministic techniques of the routes indicated in the answers to the survey. Results presented evidence that the majority...... and Link Nested Logit. Estimates were produced from model specifications that considered level-of-service, label and facility dummy variables. Moreover, a modelling framework was designed to represent drivers’ choices as affected by the latent constructs extracted with factor analysis. Previous experience...

Water, Energy, and Carbon with Artificial Neural Networks (WECANN): a statistically based estimate of global surface turbulent fluxes and gross primary productivity using solar-induced fluorescence

Science.gov (United States)

Hamed Alemohammad, Seyed; Fang, Bin; Konings, Alexandra G.; Aires, Filipe; Green, Julia K.; Kolassa, Jana; Miralles, Diego; Prigent, Catherine; Gentine, Pierre

2017-09-01

A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by novel remotely sensed solar-induced fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H, and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on a triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H, and GPP from 2007 to 2015 at 1° × 1° spatial resolution and at monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from the FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analyzing WECANN retrievals across three extreme drought and heat wave events demonstrates the capability of the retrievals to capture the extent of these events. Uncertainty estimates of the retrievals are analyzed and the interannual variability in average global and regional fluxes shows the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.

Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers.

Science.gov (United States)

Tu, Y D; Wang, R Z; Ge, T S; Zheng, X

2017-01-12

Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8-3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump's efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications.

Development of latent heat storage systems. New storage materials and concepts for solar energy, efficient use, and spaceflight applications. Entwicklung von Latentwaermespeichern. Neue Speichermaterialien und Konzepte fuer Solarenergie, rationelle Energienutzung und Raumfahrtanwendungen

Energy Technology Data Exchange (ETDEWEB)

Glueck, A.; Krause, S.; Lindner, F.; Staehle, H.J.; Tamme, R. (DLR, Stuttgart (Germany). Inst. fuer Technische Thermodynamik)

1991-11-01

To extend the operational range of thermal energy storage systems and to provide access to new fields of applications, it is necessary to develop storage systems with higher energy densities than can be achieved with conventional materials. Advanced storage concepts such as latent heat storage and chemical storage are suitable for this. (orig.).

Condition monitoring of steam generator by estimating the overall heat transfer coefficient

International Nuclear Information System (INIS)

Furusawa, Hiroaki; Gofuku, Akio

2013-01-01

This study develops a technique for monitoring in on-line the state of the steam generator of the fast-breeder reactor (FBR) “Monju”. Because the FBR uses liquid sodium as coolant, it is necessary to handle liquid sodium with caution due to its chemical characteristics. The steam generator generates steam by the heat of secondary sodium coolant. The sodium-water reaction may happen if a pinhole or crack occurs at the thin metal tube wall that separates the secondary sodium coolant and water/steam. Therefore, it is very important to detect an anomaly of the wall of heat transfer tubes at an early stage. This study aims at developing an on-line condition monitoring technique of the steam generator by estimating overall heat transfer coefficient from process signals. This paper describes simplified mathematical models of superheater and evaporator to estimate the overall heat transfer coefficient and a technique to diagnose the state of the steam generator. The applicability of the technique is confirmed by several estimations using simulated process signals with artificial noises. The results of the estimations show that the developed technique can detect the occurrence of an anomaly. (author)

An inter-comparison of six latent and sensible heat flux products over the Southern Ocean

Directory of Open Access Journals (Sweden)

Lejiang Yu

2011-11-01

Full Text Available The latent heat fluxes (LHF and sensible heat fluxes (SHF over the Southern Ocean from six different data sets are inter-compared for the period 1988–2000. The six data sets include three satellite-based products, namely, the second version of the Goddard Satellite-Based Surface Turbulent Fluxes data set (GSSTF-2, the third version of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3 and the Japanese Ocean Fluxes Data Sets with Use of Remote Sensing Observations (J-OFURO; two global reanalysis products, namely, the National Centers for Environmental Prediction–Department of Energy Reanalysis 2 data set (NCEP-2 and the European Centre for Medium-Range Weather Forecasts 40 Year Re-analysis data set (ERA-40; and the Objectively Analyzed Air–Sea Fluxes for the Global Oceans data set (OAFlux. All these products reveal a similar pattern in the averaged flux fields. The zonal mean LHF fields all exhibit a continuous increase equatorward. With an exception of HOAPS-3, the zonal mean SHF fields display a minimum value near 50°S, increasing both pole- and equatorward. The differences in the standard deviation for LHF are larger among the six data products than the differences for SHF. Over the regions where the surface fluxes are significantly influenced by the Antarctic Oscillation and the Pacific–South American teleconnection, the values and distributions of both LHF and SHF are consistent among the six products. It was found that the spatial patterns of the standard deviations and trends of LHF and SHF can be explained primarily by sea–air specific humidity and temperature differences; wind speed plays a minor role.

Natural convection heat transfer of fluid with temperature-dependent specific heat

International Nuclear Information System (INIS)

Tanaka, Amane; Kubo, Shinji; Akino, Norio

1998-01-01

The present study investigates natural convection from a heated vertical plate of fluid with temperature-dependent specific heat, which is introduced as a model of microencapsulated phase change material slurries (MCPCM slurries). The temperature dependence of specific heat is represented by Gauss function with three physical parameters (peak temperature, width of phase change temperature and latent heat). Boundary layer equations are solved numerically, and the velocity and temperature fields of the flow are obtained. The relation between the heat transfer coefficients and the physical parameters of specific heat is discussed. The results show that the velocities and temperatures are smaller, and the heat transfer coefficients are larger comparing with those of the fluid with constant specific heat. (author)

Effects of high-frequency activity on latent heat flux of MJO

Science.gov (United States)

Gao, Yingxia; Hsu, Pang-Chi; Li, Tim

2018-04-01

The effect of high-frequency (HF) variability on latent heat flux (LHF) associated with the Madden-Julian Oscillation (MJO) during the boreal winter is investigated through diagnosis using two reanalysis datasets and numerical experiments of an atmospheric general circulation model (AGCM). The diagnostic results show that the HF activities exert an impact on the variability of MJO LHF mainly through their interactions with the longer than 90-day low-frequency background state (LFBS). The contribution of intraseasonal LHF induced by the interactions between LFBS and HF activities accounts for more than 20% of the total intraseasonal LHF over active MJO regions. The intraseasonal LHF induced by the LFBS-HF interaction is in phase with the MJO convection, while the total intraseasonal LHF appears at and to the west of the MJO convection center. This suggests that the intraseasonal LHF via the feedback of HF activity interacting with LFBS is conducive to the maintenance and eastward propagation of MJO convection. To confirm the role of HF disturbances in MJO convection activity, we carry out a series of experiments using the AGCM of ECHAM4, which captures well the general features of MJO. We select a number of MJO cases with enhanced convective signals and significant eastward propagation from a 30-year climatological simulation. Once the HF components of surface wind and moisture fields in LHF are excluded in model integration for each MJO case, most of the simulated MJO convection shows weakened activity and a slower propagation speed compared to the simulations containing all time-scale components. The outputs of these sensitivity experiments support the diagnostic results that HF activities contribute to the maintenance and propagation of MJO convection through the intraseasonal LHF induced by the scale interaction of HF activities with lower frequency variability.

A latent transition model of the effects of a teen dating violence prevention initiative.

Science.gov (United States)

Williams, Jason; Miller, Shari; Cutbush, Stacey; Gibbs, Deborah; Clinton-Sherrod, Monique; Jones, Sarah

2015-02-01

Patterns of physical and psychological teen dating violence (TDV) perpetration, victimization, and related behaviors were examined with data from the evaluation of the Start Strong: Building Healthy Teen Relationships initiative, a dating violence primary prevention program targeting middle school students. Latent class and latent transition models were used to estimate distinct patterns of TDV and related behaviors of bullying and sexual harassment in seventh grade students at baseline and to estimate transition probabilities from one pattern of behavior to another at the 1-year follow-up. Intervention effects were estimated by conditioning transitions on exposure to Start Strong. Latent class analyses suggested four classes best captured patterns of these interrelated behaviors. Classes were characterized by elevated perpetration and victimization on most behaviors (the multiproblem class), bullying perpetration/victimization and sexual harassment victimization (the bully-harassment victimization class), bullying perpetration/victimization and psychological TDV victimization (bully-psychological victimization), and experience of bully victimization (bully victimization). Latent transition models indicated greater stability of class membership in the comparison group. Intervention students were less likely to transition to the most problematic pattern and more likely to transition to the least problem class. Although Start Strong has not been found to significantly change TDV, alternative evaluation models may find important differences. Latent transition analysis models suggest positive intervention impact, especially for the transitions at the most and the least positive end of the spectrum. Copyright © 2015. Published by Elsevier Inc.

Phase Change Energy Storage Material Suitable for Solar Heating System

Science.gov (United States)

Li, Xiaohui; Li, Haihua; Zhang, Lihui; Liu, Zhenfa

2018-01-01

Differential scanning calorimetry (DSC) was used to investigate the thermal properties of palmitic acid, myristic acid, laurel acid and the binary composite of palmitic/laurel acid and palmitic/myristic acid. The results showed that the phase transition temperatures of the three monomers were between 46.9-65.9°C, and the latent heats were above 190 J/g, which could be used as solar energy storage material. When the mass ratio of Palmitic acid and myristic was 1:1, the eutectic mixture could be formed. The latent heat of the eutectic mixture was 186.6 J/g, the melting temperature and the solidification temperature was 50.6°C and 43.8°C respectively. The latent heat of phase change and the melting temperature had not obvious variations after 400 thermal cycles, which proved that the binary composite had good thermal stability and was suitable for solar floor radiant heating system.

Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

Science.gov (United States)

Tunnell, James W; Torres, Jorge H; Anvari, Bahman

2002-01-01

Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

Estimating the true accuracy of diagnostic tests for dengue infection using bayesian latent class models.

Directory of Open Access Journals (Sweden)

Wirichada Pan-ngum

Full Text Available Accuracy of rapid diagnostic tests for dengue infection has been repeatedly estimated by comparing those tests with reference assays. We hypothesized that those estimates might be inaccurate if the accuracy of the reference assays is not perfect. Here, we investigated this using statistical modeling.Data from a cohort study of 549 patients suspected of dengue infection presenting at Colombo North Teaching Hospital, Ragama, Sri Lanka, that described the application of our reference assay (a combination of Dengue IgM antibody capture ELISA and IgG antibody capture ELISA and of three rapid diagnostic tests (Panbio NS1 antigen, IgM antibody and IgG antibody rapid immunochromatographic cassette tests were re-evaluated using bayesian latent class models (LCMs. The estimated sensitivity and specificity of the reference assay were 62.0% and 99.6%, respectively. Prevalence of dengue infection (24.3%, and sensitivities and specificities of the Panbio NS1 (45.9% and 97.9%, IgM (54.5% and 95.5% and IgG (62.1% and 84.5% estimated by bayesian LCMs were significantly different from those estimated by assuming that the reference assay was perfect. Sensitivity, specificity, PPV and NPV for a combination of NS1, IgM and IgG cassette tests on admission samples were 87.0%, 82.8%, 62.0% and 95.2%, respectively.Our reference assay is an imperfect gold standard. In our setting, the combination of NS1, IgM and IgG rapid diagnostic tests could be used on admission to rule out dengue infection with a high level of accuracy (NPV 95.2%. Further evaluation of rapid diagnostic tests for dengue infection should include the use of appropriate statistical models.

Total decay heat estimates in a proto-type fast reactor

International Nuclear Information System (INIS)

Sridharan, M.S.

2003-01-01

Full text: In this paper, total decay heat values generated in a proto-type fast reactor are estimated. These values are compared with those of certain fast reactors. Simple analytical fits are also obtained for these values which can serve as a handy and convenient tool in engineering design studies. These decay heat values taken as their ratio to the nominal operating power are, in general, applicable to any typical plutonium based fast reactor and are useful inputs to the design of decay-heat removal systems

Fitting and interpreting continuous-time latent Markov models for panel data.

Science.gov (United States)

Lange, Jane M; Minin, Vladimir N

2013-11-20

Multistate models characterize disease processes within an individual. Clinical studies often observe the disease status of individuals at discrete time points, making exact times of transitions between disease states unknown. Such panel data pose considerable modeling challenges. Assuming the disease process progresses accordingly, a standard continuous-time Markov chain (CTMC) yields tractable likelihoods, but the assumption of exponential sojourn time distributions is typically unrealistic. More flexible semi-Markov models permit generic sojourn distributions yet yield intractable likelihoods for panel data in the presence of reversible transitions. One attractive alternative is to assume that the disease process is characterized by an underlying latent CTMC, with multiple latent states mapping to each disease state. These models retain analytic tractability due to the CTMC framework but allow for flexible, duration-dependent disease state sojourn distributions. We have developed a robust and efficient expectation-maximization algorithm in this context. Our complete data state space consists of the observed data and the underlying latent trajectory, yielding computationally efficient expectation and maximization steps. Our algorithm outperforms alternative methods measured in terms of time to convergence and robustness. We also examine the frequentist performance of latent CTMC point and interval estimates of disease process functionals based on simulated data. The performance of estimates depends on time, functional, and data-generating scenario. Finally, we illustrate the interpretive power of latent CTMC models for describing disease processes on a dataset of lung transplant patients. We hope our work will encourage wider use of these models in the biomedical setting. Copyright © 2013 John Wiley & Sons, Ltd.

Hidden Markov latent variable models with multivariate longitudinal data.

Science.gov (United States)

Song, Xinyuan; Xia, Yemao; Zhu, Hongtu

2017-03-01

Cocaine addiction is chronic and persistent, and has become a major social and health problem in many countries. Existing studies have shown that cocaine addicts often undergo episodic periods of addiction to, moderate dependence on, or swearing off cocaine. Given its reversible feature, cocaine use can be formulated as a stochastic process that transits from one state to another, while the impacts of various factors, such as treatment received and individuals' psychological problems on cocaine use, may vary across states. This article develops a hidden Markov latent variable model to study multivariate longitudinal data concerning cocaine use from a California Civil Addict Program. The proposed model generalizes conventional latent variable models to allow bidirectional transition between cocaine-addiction states and conventional hidden Markov models to allow latent variables and their dynamic interrelationship. We develop a maximum-likelihood approach, along with a Monte Carlo expectation conditional maximization (MCECM) algorithm, to conduct parameter estimation. The asymptotic properties of the parameter estimates and statistics for testing the heterogeneity of model parameters are investigated. The finite sample performance of the proposed methodology is demonstrated by simulation studies. The application to cocaine use study provides insights into the prevention of cocaine use. © 2016, The International Biometric Society.

Environmentally friendly and highly productive bi-component melt spinning of thermoregulated smart polymer fibres with high latent heat capacity

Directory of Open Access Journals (Sweden)

Ch. Cherif

2018-03-01

Full Text Available A stable and reproducible bi-component melt spinning process on an industrial scale incorporating Phase Change Material (PCM into textile fibres has been successfully developed and carried out using a melt spinning machine. The key factor for a successful bi-component melt spinning process is that a deep insight into the thermal and rheological behaviour of PCM using Difference Scanning Calorimetry (DSC, Thermogravimetric Analysis (TGA, and an oscillatory rheological investigation. PCM is very sensitive to the temperature and residence time of the melt spinning process. It is found that the optimal process temperature of PCM is 210 °C. The textile-physical properties and the morphology of the melt spun and further drawn bi-component core and sheath fibres (bico fibres were investigated and interpreted. The heat capacities of PCM incorporated in bico fibres were also determined by means of DSC. The melt spun bico fibres integrating PCM provide a high latent heat of up to 22 J/g, which is three times higher than that of state-of-the-art fibres, which were also obtained using the melt spinning process. Therefore, they have the potential to be used as smart polymer fibres for textile and other technical applications.

Estimation of low-potential heat recuperation efficiency of smoke fumes in a condensation heat utilizer under various operation conditions of a boiler and a heating system

Science.gov (United States)

Ionkin, I. L.; Ragutkin, A. V.; Luning, B.; Zaichenko, M. N.

2016-06-01

For enhancement of the natural gas utilization efficiency in boilers, condensation heat utilizers of low-potential heat, which are constructed based on a contact heat exchanger, can be applied. A schematic of the contact heat exchanger with a humidifier for preheating and humidifying of air supplied in the boiler for combustion is given. Additional low-potential heat in this scheme is utilized for heating of the return delivery water supplied from a heating system. Preheating and humidifying of air supplied for combustion make it possible to use the condensation utilizer for heating of a heat-transfer agent to temperature exceeding the dewpoint temperature of water vapors contained in combustion products. The decision to mount the condensation heat utilizer on the boiler was taken based on the preliminary estimation of the additionally obtained heat. The operation efficiency of the condensation heat utilizer is determined by its structure and operation conditions of the boiler and the heating system. The software was developed for the thermal design of the condensation heat utilizer equipped by the humidifier. Computation investigations of its operation are carried out as a function of various operation parameters of the boiler and the heating system (temperature of the return delivery water and smoke fumes, air excess, air temperature at the inlet and outlet of the condensation heat utilizer, heating and humidifying of air in the humidifier, and portion of the circulating water). The heat recuperation efficiency is estimated for various operation conditions of the boiler and the condensation heat utilizer. Recommendations on the most effective application of the condensation heat utilizer are developed.

Original article Latent classes of criminal intent associated with criminal behaviour

Directory of Open Access Journals (Sweden)

Daniel Boduszek

2014-07-01

Full Text Available Background This study aimed to examine the number of latent classes of criminal intent that exist among prisoners and to look at the associations with recidivism, number of police arrests, type of offending (robbery, violent offences, murder, and multiple offences, and age. Participants and procedure Latent class analysis was used to identify homogeneous subgroups of prisoners based on their responses to the 10 questions reflecting criminal intent. Participants were 309 male recidivistic prisoners incarcerated in a maximum security prison. Multinomial logistic regression was used to interpret the nature of the latent classes, or groups, by estimating the association between recidivism and latent classes of criminal intent while controlling for offence type (robbery, violent offences, murder, and multiple offences, number of arrests, and age. Results The best fitting latent class model was a three-class solution: ‘High criminal intent’ (49.3%, ‘Intermediate criminal intent’ (41.3%, and ‘Low criminal intent’ (9.4%. The latent classes were differentially related to the external variables (recidivism, violent offences, and age. Conclusions Criminal intent is best explained by three homogeneous classes that appear to represent an underlying continuum. Future work is needed to identify whether these distinct classes of criminal intent may predict engagement in various types of criminal behaviour.

Estimation of shutdown heat generation rates in GHARR-1 due to ...

African Journals Online (AJOL)

Fission products decay power and residual fission power generated after shutdown of Ghana Research Reactor-1 (GHARR-1) by reactivity insertion accident were estimated by solution of the decay and residual heat equations. A Matlab program code was developed to simulate the heat generation rates by fission product ...

Geothermal Heat Flux Underneath Ice Sheets Estimated From Magnetic Satellite Data

DEFF Research Database (Denmark)

Fox Maule, Cathrine; Purucker, M.E.; Olsen, Nils

The geothermal heat flux is an important factor in the dynamics of ice sheets, and it is one of the important parameters in the thermal budgets of subglacial lakes. We have used satellite magnetic data to estimate the geothermal heat flux underneath the ice sheets in Antarctica and Greenland...

A review of chemical heat pumps, thermodynamic cycles and thermal energy storage technologies for low grade heat utilisation

International Nuclear Information System (INIS)

Chan, C.W.; Ling-Chin, J.; Roskilly, A.P.

2013-01-01

A major cause of energy inefficiency is a result of the generation of waste heat and the lack of suitable technologies for cost-effective utilisation of low grade heat in particular. The market potential for surplus/waste heat from industrial processes in the UK is between 10 TWh and 40 TWh, representing a significant potential resource which has remained unexploited to date. This paper reviews selected technologies suitable for utilisation of waste heat energy, with specific focus on low grade heat, including: (i) chemical heat pumps, such as adsorption and absorption cycles for cooling and heating; (ii) thermodynamic cycles, such as the organic Rankine cycle (ORC), the supercritical Rankine cycle (SRC) and the trilateral cycle (TLC), to produce electricity, with further focus on expander and zeotropic mixtures, and (iii) thermal energy storage, including sensible and latent thermal energy storages and their corresponding media to improve the performance of low grade heat energy systems. - Highlights: ► The review of various thermal technologies for the utilisation of under exploited low grade heat. ► The analyses of the absorption and adsorption heat pumps possibly with performance enhancement additives. ► The analyses of thermal energy storage technologies (latent and sensible) for heat storage. ► The analyses of low temperature thermodynamic cycles to maximise power production.

Effects of spatial aggregation on the multi-scale estimation of evapotranspiration

KAUST Repository

Ershadi, Ali

2013-04-01

The influence of spatial resolution on the estimation of land surface heat fluxes from remote sensing is poorly understood. In this study, the effects of aggregation from fine (< 100 m) to medium (approx. 1. km) scales are investigated using high resolution Landsat 5 overpasses. A temporal sequence of satellite imagery and needed meteorological data were collected over an agricultural region, capturing distinct variations in crop stage and phenology. Here, we investigate both the impact of aggregating the input forcing and of aggregating the derived latent heat flux. In the input aggregation scenario, the resolution of the Landsat based radiance data was increased incrementally from 120. m to 960. m, with the land surface temperature calculated at each specific resolution. Reflectance based land surface parameters such as vegetation height and leaf area index were first calculated at the native 30. m Landsat resolution and then aggregated to multiple spatial scales. Using these data and associated meteorological forcing, surface heat fluxes were calculated at each distinct resolution using the Surface Energy Balance System (SEBS) model. Results indicate that aggregation of input forcing using a simple averaging method has limited effect on the land surface temperature and available energy, but can reduce evapotranspiration estimates at the image scale by up to 15%, and at the pixel scale by up to 50%. It was determined that the predominant reason for the latent heat flux reduction in SEBS was a decrease in the aerodynamic resistance at coarser resolutions, which originates from a change in the roughness length parameters of the land surface due to the aggregation. In addition, the magnitude of errors in surface heat flux estimation due to input aggregation was observed to be a function of the heterogeneity of the land surface and evaporative elements. In examining the response of flux aggregation, fine resolution (120. m) heat fluxes were aggregated to coarser

The latent effect of inertia in the modal choice

DEFF Research Database (Denmark)

Cherchi, Elisabetta; Meloni, Italo; Ortúzar, Juan de Dios

2014-01-01

The existence of habit (leading to inertia) in the choice process has been approached in the literature in a number of ways. In transport, inertia has been studied mainly using “long panel” data, or mixed revealed and stated preference data. In these studies inertia links the choice made in two...... approaches. We assume that inertia is revealed by past behaviour and affects also the initial condition, but we recognise that past behaviour is only an indicator of habitual behaviour, the true process behind the formation of habitual behaviour being latent. We estimate a hybrid choice model using a set...... of revealed and stated mode choice preferences collected in Cagliari (Italy). We found a significant latent inertia in the revealed preference data, indicating that inertia affects the initial conditions. The latent inertia is revealed by the frequency of past behaviour but the effect of trip frequency...

Thermal energy storage system using phase change materials: Constant heat source

Directory of Open Access Journals (Sweden)

Reddy Meenakshi R.

2012-01-01

Full Text Available The usage of phase change materials (PCM to store the heat in the form of latent heat is increased, because large quantity of thermal energy is stored in smaller volumes. In the present experimental investigation paraffin and stearic acid are employed as PCMs in thermal energy storage (TES system to store the heat as sensible and latent heat also. A constant heat source is used to supply heat transfer fluid (HTF at constant temperature to the TES system. In the TES system PCMs are stored in the form of spherical capsules of 38 mm diameter made of high density poly ethylene (HDPE. The results of the investigation are related to the charging time and recovery of stored energy from the TES system.

Modeling heat loss from the udder of a dairy cow.

Science.gov (United States)

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.

Prevalence and risk factors of latent Tuberculosis among ...

African Journals Online (AJOL)

termine the risk factors of prevalent LTBI. We used a mixed effects binomial model with a logarithmic link function to estimate prevalence ratios (PR) for risk fac- tors of latent tuberculosis infection (LTBI). Ethical consideration. The study was approved by the Makerere University. School of Public Health–Higher Degrees and ...

An experimental study of the latent functionally thermal fluid with micro-encapsulated phase change material particles flowing in microchannels

International Nuclear Information System (INIS)

Wang, Yan; Chen, Zhenqian; Ling, Xiang

2016-01-01

Graphical abstract: Fig. 1. Relationship between Nu and Re for MEPCM slurry with various particle volume fractions. The interrupt of the well dispersed particles would destroy the thermal boundary layer and reduces its thickness, resulting in large Nusselt number for the suspension with 2% volume fraction of MEPCM. Large amount of heat could be absorbed and transferred rapidly during MEPCM melting process, which would result in remarkable increase of Nusselt number. The heat transfer performance of latent thermal fluid would be enhanced as 1.34 times of that of pure water. With smaller particle volume fraction (1% in this context), phase change occurs at lower temperature and more intensive heat flux is required for higher concentration suspension to induce the phase change occurrence, which is useful for application of the thermal management design. - Highlights: • The experiments of latent fluid flowing in parallel microchannels were conducted. • The performance of water with well dispersed micro-encapsulated phase change material particles was examined. • The Nusselt number of MEPCM slurry could achieve 1.36 times as that of pure water. - Abstract: Phase change material holds a good promise as a media of thermal energy storage and intensive heat flux removal. In this context, experiments were conducted to investigate the hydrodynamic and thermodynamic properties of a latent thermal fluid, which consisted of water and well dispersed micro-encapsulated phase change material (MEPCM) particles, flowing in parallel microchannels. It is suggested that MEPCM particles loading induces much higher pressure drop, which is very sensitive to temperature. Compared against water, the heat transfer performance of MEPCM slurry performs much better owing to particles aggregation, collision and micro-convective around the particles. Besides these, latent heat absorbed during phase change process makes the key contribution. It is found that with melting occurrence, Nusselt

Energy and cost savings potential of oscillating heat pipes for waste heat recovery ventilation

Directory of Open Access Journals (Sweden)

Govinda Mahajan

2017-11-01

Full Text Available The feasibility of using finned oscillating heat pipes (OHPs for heat exchange between counter-flowing air streams in HVAC air systems (i.e., outdoor and exhaust air flows, along with the associated cost savings in typical North American climates, is investigated. For a prescribed temperature difference and volumetric flow rate of air, rudimentary design parameters for a viable OHP Heat Recovery Ventilator (OHP-HRV were determined using the ε-NTU (effectiveness-Number of Transfer Unit method. The two-phase heat transfer within the OHP-HRV is modeled via effective evaporation/condensation heat transfer coefficients, while the latent heat transfer required to initiate OHP operation via boiling and evaporation is also considered. Results suggest that an OHP-HRV can possess a reasonable pressure drop (5 kW. The proposed OHP-HRV can possess an effectiveness near 0.5 and can pre-cool/heat HVAC air by >5°C. Potential energy and cost savings associated with using an OHP-HRV were estimated for commercial building envelopes in various regions of the United States. It is found that the proposed OHP-HRV can save more than $2500 annually in cities that have continental climatic conditions, such as Chicago and Denver, and for the selected locations the average yearly cost savings per building is found to be on-the-order of $700. Overall, the OHP-HRV shows potential in effectively reducing energy consumption and the operational cost of air handling units in buildings.

Estimating Venezuelas Latent Inflation

OpenAIRE

Juan Carlos Bencomo; Hugo J. Montesinos; Hugo M. Montesinos; Jose Roberto Rondo

2011-01-01

Percent variation of the consumer price index (CPI) is the inflation indicator most widely used. This indicator, however, has some drawbacks. In addition to measurement errors of the CPI, there is a problem of incongruence between the definition of inflation as a sustained and generalized increase of prices and the traditional measure associated with the CPI. We use data from 1991 to 2005 to estimate a complementary indicator for Venezuela, the highest inflation country in Latin America. Late...

A coarse to fine minutiae-based latent palmprint matching.

Science.gov (United States)

Liu, Eryun; Jain, Anil K; Tian, Jie

2013-10-01

With the availability of live-scan palmprint technology, high resolution palmprint recognition has started to receive significant attention in forensics and law enforcement. In forensic applications, latent palmprints provide critical evidence as it is estimated that about 30 percent of the latents recovered at crime scenes are those of palms. Most of the available high-resolution palmprint matching algorithms essentially follow the minutiae-based fingerprint matching strategy. Considering the large number of minutiae (about 1,000 minutiae in a full palmprint compared to about 100 minutiae in a rolled fingerprint) and large area of foreground region in full palmprints, novel strategies need to be developed for efficient and robust latent palmprint matching. In this paper, a coarse to fine matching strategy based on minutiae clustering and minutiae match propagation is designed specifically for palmprint matching. To deal with the large number of minutiae, a local feature-based minutiae clustering algorithm is designed to cluster minutiae into several groups such that minutiae belonging to the same group have similar local characteristics. The coarse matching is then performed within each cluster to establish initial minutiae correspondences between two palmprints. Starting with each initial correspondence, a minutiae match propagation algorithm searches for mated minutiae in the full palmprint. The proposed palmprint matching algorithm has been evaluated on a latent-to-full palmprint database consisting of 446 latents and 12,489 background full prints. The matching results show a rank-1 identification accuracy of 79.4 percent, which is significantly higher than the 60.8 percent identification accuracy of a state-of-the-art latent palmprint matching algorithm on the same latent database. The average computation time of our algorithm for a single latent-to-full match is about 141 ms for genuine match and 50 ms for impostor match, on a Windows XP desktop system with 2

Estimating end-use emissions factors for policy analysis: the case of space cooling and heating.

Science.gov (United States)

Jacobsen, Grant D

2014-06-17

This paper provides the first estimates of end-use specific emissions factors, which are estimates of the amount of a pollutant that is emitted when a unit of electricity is generated to meet demand from a specific end-use. In particular, this paper provides estimates of emissions factors for space cooling and heating, which are two of the most significant end-uses. The analysis is based on a novel two-stage regression framework that estimates emissions factors that are specific to cooling or heating by exploiting variation in cooling and heating demand induced by weather variation. Heating is associated with similar or greater CO2 emissions factor than cooling in all regions. The difference is greatest in the Midwest and Northeast, where the estimated CO2 emissions factor for heating is more than 20% larger than the emissions factor for cooling. The minor differences in emissions factors in other regions, combined with the substantial difference in the demand pattern for cooling and heating, suggests that the use of overall regional emissions factors is reasonable for policy evaluations in certain locations. Accurately quantifying the emissions factors associated with different end-uses across regions will aid in designing improved energy and environmental policies.

Best estimate radiation heat transfer model developed for TRAC-BD1

International Nuclear Information System (INIS)

Spore, J.W.; Giles, M.M.; Shumway, R.W.

1981-01-01

A best estimate radiation heat transfer model for analysis of BWR fuel bundles has been developed and compared with 8 x 8 fuel bundle data. The model includes surface-to-surface and surface-to-two-phase fluid radiation heat transfer. A simple method of correcting for anisotropic reflection effects has been included in the model

Modeling change in learning strategies throughout higher education: a multi-indicator latent growth perspective.

Science.gov (United States)

Coertjens, Liesje; Donche, Vincent; De Maeyer, Sven; Vanthournout, Gert; Van Petegem, Peter

2013-01-01

The change in learning strategies during higher education is an important topic of research in the Student Approaches to Learning field. Although the studies on this topic are increasingly longitudinal, analyses have continued to rely primarily on traditional statistical methods. The present research is innovative in the way it uses a multi-indicator latent growth analysis in order to more accurately estimate the general and differential development in learning strategy scales. Moreover, the predictive strength of the latent growth models are estimated. The sample consists of one cohort of Flemish University College students, 245 of whom participated in the three measurement waves by filling out the processing and regulation strategies scales of the Inventory of Learning Styles--Short Versions. Independent-samples t-tests revealed that the longitudinal group is a non-random subset of students starting University College. For each scale, a multi-indicator latent growth model is estimated using Mplus 6.1. Results suggest that, on average, during higher education, students persisting in their studies in a non-delayed manner seem to shift towards high-quality learning and away from undirected and surface-oriented learning. Moreover, students from the longitudinal group are found to vary in their initial levels, while, unexpectedly, not in their change over time. Although the growth models fit the data well, significant residual variances in the latent factors remain.

Modeling change in learning strategies throughout higher education: a multi-indicator latent growth perspective.

Directory of Open Access Journals (Sweden)

Liesje Coertjens

Full Text Available The change in learning strategies during higher education is an important topic of research in the Student Approaches to Learning field. Although the studies on this topic are increasingly longitudinal, analyses have continued to rely primarily on traditional statistical methods. The present research is innovative in the way it uses a multi-indicator latent growth analysis in order to more accurately estimate the general and differential development in learning strategy scales. Moreover, the predictive strength of the latent growth models are estimated. The sample consists of one cohort of Flemish University College students, 245 of whom participated in the three measurement waves by filling out the processing and regulation strategies scales of the Inventory of Learning Styles--Short Versions. Independent-samples t-tests revealed that the longitudinal group is a non-random subset of students starting University College. For each scale, a multi-indicator latent growth model is estimated using Mplus 6.1. Results suggest that, on average, during higher education, students persisting in their studies in a non-delayed manner seem to shift towards high-quality learning and away from undirected and surface-oriented learning. Moreover, students from the longitudinal group are found to vary in their initial levels, while, unexpectedly, not in their change over time. Although the growth models fit the data well, significant residual variances in the latent factors remain.

Evaluation of Validity and Reliability for Hierarchical Scales Using Latent Variable Modeling

Science.gov (United States)

Raykov, Tenko; Marcoulides, George A.

2012-01-01

A latent variable modeling method is outlined, which accomplishes estimation of criterion validity and reliability for a multicomponent measuring instrument with hierarchical structure. The approach provides point and interval estimates for the scale criterion validity and reliability coefficients, and can also be used for testing composite or…

Data demonstrating the influence of the latent storage efficiency on the dynamic thermal characteristics of a PCM layer

Directory of Open Access Journals (Sweden)

D. Mazzeo

2017-06-01

Full Text Available Dynamic thermal characteristics, for each month of the year, of PCM layers with different melting temperatures and thermophysical properties, in a steady periodic regime, were determined (Mazzeo et al., 2017 [1]. The layer is subjected to climatic conditions characterizing two locations, one with a continental climate and the second one with a Mediterranean climate. This data article provides detailed numerical data, as a function of the latent storage efficiency, including monthly average daily values: of the latent energy fraction, of the decrement factors of the temperature, of the heat flux and of the energy, and of the time lags of the maximum and minimum peaks of the temperature and of the heat flux.

Inverse estimation of heat flux and temperature on nozzle throat-insert inner contour

Energy Technology Data Exchange (ETDEWEB)

Chen, Tsung-Chien [Department of Power Vehicle and Systems Engineering, Chung Cheng Institute of Technology, National Defense University, Ta-Hsi, Tao-Yuan 33509 (China); Liu, Chiun-Chien [Chung Shan Institute of Science and Technology, Lung-Tan, Tao-Yuan 32526 (China)

2008-07-01

During the missile flight, the jet flow with high temperature comes from the heat flux of propellant burning. An enormous heat flux from the nozzle throat-insert inner contour conducted into the nozzle shell will degrade the material strength of nozzle shell and reduce the nozzle thrust efficiency. In this paper, an on-line inverse method based on the input estimation method combined with the finite-element scheme is proposed to inversely estimate the unknown heat flux on the nozzle throat-insert inner contour and the inner wall temperature by applying the temperature measurements of the nozzle throat-insert. The finite-element scheme can easily define the irregularly shaped boundary. The superior capability of the proposed method is demonstrated in two major time-varying estimation cases. The computational results show that the proposed method has good estimation performance and highly facilitates the practical implementation. An effective analytical method can be offered to increase the operation reliability and thermal-resistance layer design in the solid rocket motor. (author)

Solar heating system

Science.gov (United States)

Schreyer, James M.; Dorsey, George F.

1982-01-01

An improved solar heating system in which the incident radiation of the sun is absorbed on collector panels, transferred to a storage unit and then distributed as heat for a building and the like. The improvement is obtained by utilizing a storage unit comprising separate compartments containing an array of materials having different melting points ranging from 75.degree. to 180.degree. F. The materials in the storage system are melted in accordance with the amount of heat absorbed from the sun and then transferred to the storage system. An efficient low volume storage system is provided by utilizing the latent heat of fusion of the materials as they change states in storing and releasing heat for distribution.

Review of PCMS and heat transfer enhancement methods applied ...

African Journals Online (AJOL)

Most available PCMs have low thermal conductivity making heat transfer enhancement necessary for power applications. The various methods of heat transfer enhancement in latent heat storage systems were also reviewed systematically. The review showed that three commercially - available PCMs are suitable in the ...

Estimation of heat rejection based on the air conditioner use time and its mitigation from buildings in Taipei City

Energy Technology Data Exchange (ETDEWEB)

Hsieh, Chun-Ming; Aramaki, Toshiya; Hanaki, Keisuke [The University of Tokyo, Bunkyo-ku, Tokyo (Japan). Department of Urban Engineering

2007-09-15

The main work in the research focuses on the analysis and mitigation of the anthropogenic heat discharged from buildings, which is one of the main reasons leading to the heat island effect. The residential and commercial buildings, divided into 10 categories, with HVAC systems were analyzed by the building energy program, EnergyPlus. With the help of GIS, the heat rejection of all the residential and commercial buildings in DaAn Ward of Taipei City were evaluated, in which the spatial data and diurnal variation of the heat rejection were described by 3-h time periods. Furthermore, the effect of mitigation strategies was discussed. The first strategy was to change the wall/roof material of building envelope. The second and third strategies, from the viewpoint of energy saving, were to change the temperature setting of air conditioners and to turn off the lighting and equipment when not in use. The fourth strategy was to use a better efficiency of the cooling systems. Finally, the evaluation of installing the water-cooled cooling system, which discharges heat in the form of sensible and latent heat, was also included. (author)

Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

Science.gov (United States)

Goodge, John W.

2018-02-01

Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2-2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 µW m-3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m-2 and an average of 48.0 ± 13.6 mW m-2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central

Latent-trait latent-class analysis of selfdisclosure in the work environment

NARCIS (Netherlands)

Maij - de Meij, A.M.; Kelderman, H.; van der Flier, H.

2006-01-01

Based on the literature about self-disclosure, it was hypothesized that different groups of subjects differ in their pattern of self-disclosure with respect to different areas of social interaction. An extended latent-trait latent-class model was proposed to describe these general patterns of

Latent-trait latent-class analysis of selfdisclosure in the work environment

NARCIS (Netherlands)

Maij - de Meij, A.M.; Kelderman, H.; van der Flier, H.

2005-01-01

Based on the literature about self-disclosure, it was hypothesized that different groups of subjects differ in their pattern of self-disclosure with respect to different areas of social interaction. An extended latent-trait latent-class model was proposed to describe these general patterns of

Thermal contact resistance in carbon nanotube enhanced heat storage materials

NARCIS (Netherlands)

Zhang, H.; Nedea, S.V.; Rindt, C.C.M.; Smeulders, D.M.J.

2015-01-01

Solid-liquid phase change is one of the most favorable means of compact and economical heat storage in the built environment. In such storage systems, the vast available solar heat is stored as latent heat in the storage materials. Recent studies suggest using sugar alcohols as seasonal heat storage

Validation and scale dependencies of the triangle method for the evaporative fraction estimation over heterogeneous areas

DEFF Research Database (Denmark)

de Tomás, Alberto; Nieto, Héctor; Guzinski, Radoslaw

2014-01-01

Remote sensing has proved to be a consistent tool for monitoring water fluxes at regional scales. The triangle method, in particular, estimates the evaporative fraction (EF), defined as the ratio of latent heat flux (LE) to available energy, based on the relationship between satellite observations...... of land surface temperature and a vegetation index. Among other methodologies, this approach has been commonly used as an approximation to estimate LE, mainly over large semi-arid areas with uniform landscape features. In this study, an interpretation of the triangular space has been applied over...

Coupled cooling method and application of latent heat thermal energy storage combined with pre-cooling of envelope: Method and model development

International Nuclear Information System (INIS)

Yuan, Yanping; Gao, Xiangkui; Wu, Hongwei; Zhang, Zujin; Cao, Xiaoling; Sun, Liangliang; Yu, Nanyang

2017-01-01

The traditional cooling methods cannot meet the requirements of safety, stability, reliability and no-power at the same time under some special circumstances. In this study, a new coupled cooling method of Latent Heat Thermal Energy Storage (LHTES) combined with Pre-cooling of Envelope (PE) is proposed and the numerical model of the coupled cooling method is developed. In the current study, a refuge chamber is selected as a case study. A semi-analytical method is used to analyze the cold storage performance of the Surrounding Rock (SR). Afterwards, a numerical model of the coupled cooling system, which takes the heat source, SR, Phase Change Material (PCM) and air heat transfer into consideration, is further established. The study identified that the simplified semi-analytical calculation formula with the diagram of the cold storage quantity of SR are very helpful for engineering calculation. The influence of the Fourier and Biot number on the cold storage capacity of SR can be easily analyzed. In addition, the whole-field model of the coupled cooling system is completely developed based on the PCM unit. - Highlights: • A new coupled cooling method that combines LHTES with PE is proposed. • This method can be applicable to a high-temperature and no-power circumstance. • The simplified calculation formula of the cold storage quantity of SR is given. • An efficient simulation model of the coupled cooling system is established.

Latent cluster analysis of ALS phenotypes identifies prognostically differing groups.

Directory of Open Access Journals (Sweden)

Jeban Ganesalingam

2009-09-01

Full Text Available Amyotrophic lateral sclerosis (ALS is a degenerative disease predominantly affecting motor neurons and manifesting as several different phenotypes. Whether these phenotypes correspond to different underlying disease processes is unknown. We used latent cluster analysis to identify groupings of clinical variables in an objective and unbiased way to improve phenotyping for clinical and research purposes.Latent class cluster analysis was applied to a large database consisting of 1467 records of people with ALS, using discrete variables which can be readily determined at the first clinic appointment. The model was tested for clinical relevance by survival analysis of the phenotypic groupings using the Kaplan-Meier method.The best model generated five distinct phenotypic classes that strongly predicted survival (p<0.0001. Eight variables were used for the latent class analysis, but a good estimate of the classification could be obtained using just two variables: site of first symptoms (bulbar or limb and time from symptom onset to diagnosis (p<0.00001.The five phenotypic classes identified using latent cluster analysis can predict prognosis. They could be used to stratify patients recruited into clinical trials and generating more homogeneous disease groups for genetic, proteomic and risk factor research.

An eddy covariance system to characterize the atmospheric surface layer and turbulent latent heat fluxes over a debris-covered Himalayan glacier.

Science.gov (United States)

Litt, Maxime; Steiner, Jakob F.; Stigter, Emmy E.; Immerzeel, Walter; Shea, Joseph Michael

2017-04-01

Over debris-covered glaciers, water content variations in the debris layer can drive significant changes in its thermal conductivity and significantly impact melt rates. Since sublimation and evaporation are favoured in high-altitude conditions, e.g., low atmospheric pressure and high wind speeds, they are expected to strongly influence the water balance of the debris-layer. Dedicated latent heat fluxes measurements at the debris surface are essential to characterize the debris heat conductivity in order to assess underlying ice melt. Furthermore, the contribution of the turbulent fluxes in the surface energy balance over debris covered glacier remains uncertain since they are generally evaluated through similarity methods which might not be valid in complex terrain. We present the first results of a 15-day eddy-covariance experiment installed at the end of the monsoon (September-October) on a 3-m tower above the debris-covered Lirung glacier in Nepal. The tower also included measurements of the 4 radiation components. The eddy covariance measurements allowed for the characterization of the turbulence in the atmospheric surface layer, as well as the direct measurements of evaporation, sublimation and turbulent sensible heat fluxes. The experiment helps us to evaluate the contribution of turbulent fluxes to the surface energy balance over this debris-covered glacier, through a precise characterization of the overlying turbulent atmospheric surface layer. It also helps to study the role of the debris-layer water content changes through evaporation and sublimation and its feedback on heat conduction in this layer. The large observed turbulent fluxes play a significant role in the energy balance at the debris surface and significantly influence debris moisture, conductivity and subsequently underlying ice melt.

Occurence of internet addiction in a general population sample: A latent class analysis

NARCIS (Netherlands)

Rumpf, H.J.; Vermulst, A.A.; Bischof, A.; Kastirke, N.; Gürtler, D.; Bischof, G.; Meerkerk, G.J.; John, U.; Meyer, C.

2014-01-01

Background: Prevalence studies of Internet addiction in the general population are rare. In addition, a lack of approved criteria hampers estimation of its occurrence. Aims: This study conducted a latent class analysis (LCA) in a large general population sample to estimate prevalence. Methods: A

The Impacts of Heating Strategy on Soil Moisture Estimation Using Actively Heated Fiber Optics.

Science.gov (United States)

Dong, Jianzhi; Agliata, Rosa; Steele-Dunne, Susan; Hoes, Olivier; Bogaard, Thom; Greco, Roberto; van de Giesen, Nick

2017-09-13

Several recent studies have highlighted the potential of Actively Heated Fiber Optics (AHFO) for high resolution soil moisture mapping. In AHFO, the soil moisture can be calculated from the cumulative temperature ( T cum ), the maximum temperature ( T max ), or the soil thermal conductivity determined from the cooling phase after heating ( λ ). This study investigates the performance of the T cum , T max and λ methods for different heating strategies, i.e., differences in the duration and input power of the applied heat pulse. The aim is to compare the three approaches and to determine which is best suited to field applications where the power supply is limited. Results show that increasing the input power of the heat pulses makes it easier to differentiate between dry and wet soil conditions, which leads to an improved accuracy. Results suggest that if the power supply is limited, the heating strength is insufficient for the λ method to yield accurate estimates. Generally, the T cum and T max methods have similar accuracy. If the input power is limited, increasing the heat pulse duration can improve the accuracy of the AHFO method for both of these techniques. In particular, extending the heating duration can significantly increase the sensitivity of T cum to soil moisture. Hence, the T cum method is recommended when the input power is limited. Finally, results also show that up to 50% of the cable temperature change during the heat pulse can be attributed to soil background temperature, i.e., soil temperature changed by the net solar radiation. A method is proposed to correct this background temperature change. Without correction, soil moisture information can be completely masked by the background temperature error.

Environmental Forcing of Supertyphoon Paka's (1997) Latent Heat Structure.

Science.gov (United States)

Rodgers, Edward; Olson, William; Halverson, Jeff; Simpson, Joanne; Pierce, Harold

2000-12-01

The distribution and intensity of total (i.e., combined stratified and convective processes) rain rate/latent heat release (LHR) were derived for Tropical Cyclone Paka during the period 9-21 December 1997 from the F-10, F-11, F-13, and F-14 Defense Meteorological Satellite Special Sensor Microwave Imager and the Tropical Rainfall Measuring Mission Microwave Imager observations. These observations were frequent enough to capture three episodes of inner-core convective bursts and a convective rainband cycle that preceded periods of rapid intensification. During these periods of convective bursts, satellite sensors revealed that the rain rates/LHR 1) increased within the inner-core region, 2) were mainly convectively generated (nearly a 65% contribution), 3) propagated inward, 4) extended upward within the mid- and upper troposphere, and 5) became electrically charged. These factors may have increased the areal mean ascending motion in the mid- and upper-troposphere eyewall region, creating greater cyclonic angular momentum, and, thereby, warming the center and intensifying the system.Radiosonde measurements from Kwajalein Atoll and Guam, sea surface temperature observations, and the European Centre for Medium-Range Forecasts analyses were used to examine the necessary and sufficient conditions for initiating and maintaining these inner-core convective bursts. For example, the necessary conditions such as the atmospheric thermodynamics [i.e., cold tropopause temperatures, moist troposphere, and warm SSTs (>26°C)] fulfill the necessary conditions and suggested that the atmosphere was ideally suited for Paka's maximum potential intensity to approach supertyphoon strength. Further, Paka encountered moderate vertical wind shear (<15 m s1) before interacting with the westerlies on 21 December. The sufficient conditions that include horizontal moisture and the upper-tropospheric eddy relative angular momentum fluxes, on the other hand, appeared to have some influence on

The efficiency of parameter estimation of latent path analysis using summated rating scale (SRS) and method of successive interval (MSI) for transformation of score to scale

Science.gov (United States)

Solimun, Fernandes, Adji Achmad Rinaldo; Arisoesilaningsih, Endang

2017-12-01

Research in various fields generally investigates systems and involves latent variables. One method to analyze the model representing the system is path analysis. The data of latent variables measured using questionnaires by applying attitude scale model yields data in the form of score, before analyzed should be transformation so that it becomes data of scale. Path coefficient, is parameter estimator, calculated from scale data using method of successive interval (MSI) and summated rating scale (SRS). In this research will be identifying which data transformation method is better. Path coefficients have smaller varieties are said to be more efficient. The transformation method that produces scaled data and used in path analysis capable of producing path coefficients (parameter estimators) with smaller varieties is said to be better. The result of analysis using real data shows that on the influence of Attitude variable to Intention Entrepreneurship, has relative efficiency (ER) = 1, where it shows that the result of analysis using data transformation of MSI and SRS as efficient. On the other hand, for simulation data, at high correlation between items (0.7-0.9), MSI method is more efficient 1.3 times better than SRS method.

Estimation of the Relationship Between Remotely Sensed Anthropogenic Heat Discharge and Building Energy Use

Science.gov (United States)

Zhou, Yuyu; Weng, Qihao; Gurney, Kevin R.; Shuai, Yanmin; Hu, Xuefei

2012-01-01

This paper examined the relationship between remotely sensed anthropogenic heat discharge and energy use from residential and commercial buildings across multiple scales in the city of Indianapolis, Indiana, USA. The anthropogenic heat discharge was estimated with a remote sensing-based surface energy balance model, which was parameterized using land cover, land surface temperature, albedo, and meteorological data. The building energy use was estimated using a GIS-based building energy simulation model in conjunction with Department of Energy/Energy Information Administration survey data, the Assessor's parcel data, GIS floor areas data, and remote sensing-derived building height data. The spatial patterns of anthropogenic heat discharge and energy use from residential and commercial buildings were analyzed and compared. Quantitative relationships were evaluated across multiple scales from pixel aggregation to census block. The results indicate that anthropogenic heat discharge is consistent with building energy use in terms of the spatial pattern, and that building energy use accounts for a significant fraction of anthropogenic heat discharge. The research also implies that the relationship between anthropogenic heat discharge and building energy use is scale-dependent. The simultaneous estimation of anthropogenic heat discharge and building energy use via two independent methods improves the understanding of the surface energy balance in an urban landscape. The anthropogenic heat discharge derived from remote sensing and meteorological data may be able to serve as a spatial distribution proxy for spatially-resolved building energy use, and even for fossil-fuel CO2 emissions if additional factors are considered.

Cost estimation of hydrogen and DME produced by nuclear heat utilization system. Joint research

International Nuclear Information System (INIS)

Shiina, Yasuaki; Nishihara, Tetsuo

2003-09-01

Research of hydrogen energy has been performed in order to spread use of the hydrogen energy in 2020 or 2030. It will take, however, many years for the hydrogen energy to be used very easily like gasoline, diesel oil and city gas in all of countries. During the periods, low CO 2 release liquid fuels would be used together with hydrogen. Recently, di-methyl-either (DME) has been noticed as one of the substitute liquid fuels of petroleum. Such liquid fuels can be produced from the mixed gas such as hydrogen and carbon oxide which are produced by steam reforming hydrogen generation system by the use of nuclear heat. Therefore, the system would be one of the candidates of future system of nuclear heat utilization. In the present study, we focused on the production of hydrogen and DME. Economic evaluation was estimated for hydrogen and DME production in commercial and nuclear heat utilization plant. At first, heat and mass balance of each process in commercial plant of hydrogen production was estimated and commercial prices of each process were derived. Then, price was estimated when nuclear heat was used instead of required heat of commercial plant. Results showed that the production prices produced by nuclear heat were cheaper by 10% for hydrogen and 3% for DME. With the consideration of reduction effect of CO 2 release, utilization of nuclear heat would be more effective. (author)

Calibration of Ocean Forcing with satellite Flux Estimates (COFFEE)

Science.gov (United States)

Barron, Charlie; Jan, Dastugue; Jackie, May; Rowley, Clark; Smith, Scott; Spence, Peter; Gremes-Cordero, Silvia

2016-04-01

Predicting the evolution of ocean temperature in regional ocean models depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. Within the COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates, real-time satellite observations are used to estimate shortwave, longwave, sensible, and latent air-sea heat flux corrections to a background estimate from the prior day's regional or global model forecast. These satellite-corrected fluxes are used to prepare a corrected ocean hindcast and to estimate flux error covariances to project the heat flux corrections for a 3-5 day forecast. In this way, satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. While traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle, COFFEE endeavors to appropriately partition and reduce among various surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using operational global or regional atmospheric forcing. Experiment cases combine different levels of flux calibration with assimilation alternatives. The cases use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is

Membrane heat exchanger in HVAC energy recovery systems, systems energy analysis

Energy Technology Data Exchange (ETDEWEB)

Nasif, M. [School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Opus International Consultants (New Zealand); AL-Waked, R. [Mechanical Engineering Department, Prince Mohammad Bin Fahd University (PMU), P.O. Box 1614, AlKhobar 31952 (Saudi Arabia); Morrison, G. [School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Behnia, M. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia)

2010-10-15

The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system. (author)

Empirically Estimated Heats of Combustion of Oxygenated Hydrocarbon Bio-type Oils

Directory of Open Access Journals (Sweden)

Dmitry A. Ponomarev

2015-04-01

Full Text Available An empirical method is proposed by which the heats of combustion of oxygenated hydrocarbon oils, typically found from wood pyrolysis, may be calculated additively from empirically predicted heats of combustion of individual compounds. The predicted values are in turn based on four types of energetically inequivalent carbon and four types of energetically inequivalent hydrogen atomic energy values. A method is also given to estimate the condensation heats of oil mixtures based on the presence of four types of intermolecular forces. Agreement between predicted and experimental values of combustion heats for a typical mixture of known compounds was ± 2% and < 1% for a freshly prepared mixture of known compounds.

Estimation of test characteristics of real-time PCR and bacterial culture for diagnosis of subclinical intramammary infections with Streptococcus agalactiae in Danish dairy cattle in 2012 using latent class analysis

DEFF Research Database (Denmark)

Mahmmod, Yasser; Toft, Nils; Katholm, Jørgen

2013-01-01

threshold (Ct) values against bacterial culture (BC) for diagnosis of S. agalactiae IMI using latent class analysis to avoid the assumption of a perfect reference test. A total of 614 dairy cows were randomly selected from 6 herds with bulk tank PCR Ct value ≤ 39 for S. agalactiae and S. aureus. At milk...... cut-offs, indicating under estimation of S. agalactiae IMI in the examined dairy cows. In conclusion, Se of PCR is always higher than Se of BC at all tested cut-offs. The lower cut-off, the more comparable becomes Se of PCR and Se of BC. The changes in Se in both PCR and BC at different Ct-value cut...... definition of infection may reflect a more general condition of cows being positive for S. agalactiae. Our findings indicate that PCR Ct-value cut-offs should be chosen according to the underlying latent infection definition of interest. Latent class analysis proposes a useful alternative to classic test...

Inverse problem of estimating transient heat transfer rate on external wall of forced convection pipe

International Nuclear Information System (INIS)

Chen, W.-L.; Yang, Y.-C.; Chang, W.-J.; Lee, H.-L.

2008-01-01

In this study, a conjugate gradient method based inverse algorithm is applied to estimate the unknown space and time dependent heat transfer rate on the external wall of a pipe system using temperature measurements. It is assumed that no prior information is available on the functional form of the unknown heat transfer rate; hence, the procedure is classified as function estimation in the inverse calculation. The accuracy of the inverse analysis is examined by using simulated exact and inexact temperature measurements. Results show that an excellent estimation of the space and time dependent heat transfer rate can be obtained for the test case considered in this study

A multi-method and multi-scale approach for estimating city-wide anthropogenic heat fluxes

Science.gov (United States)

Chow, Winston T. L.; Salamanca, Francisco; Georgescu, Matei; Mahalov, Alex; Milne, Jeffrey M.; Ruddell, Benjamin L.

2014-12-01

A multi-method approach estimating summer waste heat emissions from anthropogenic activities (QF) was applied for a major subtropical city (Phoenix, AZ). These included detailed, quality-controlled inventories of city-wide population density and traffic counts to estimate waste heat emissions from population and vehicular sources respectively, and also included waste heat simulations derived from urban electrical consumption generated by a coupled building energy - regional climate model (WRF-BEM + BEP). These component QF data were subsequently summed and mapped through Geographic Information Systems techniques to enable analysis over local (i.e. census-tract) and regional (i.e. metropolitan area) scales. Through this approach, local mean daily QF estimates compared reasonably versus (1.) observed daily surface energy balance residuals from an eddy covariance tower sited within a residential area and (2.) estimates from inventory methods employed in a prior study, with improved sensitivity to temperature and precipitation variations. Regional analysis indicates substantial variations in both mean and maximum daily QF, which varied with urban land use type. Average regional daily QF was ∼13 W m-2 for the summer period. Temporal analyses also indicated notable differences using this approach with previous estimates of QF in Phoenix over different land uses, with much larger peak fluxes averaging ∼50 W m-2 occurring in commercial or industrial areas during late summer afternoons. The spatio-temporal analysis of QF also suggests that it may influence the form and intensity of the Phoenix urban heat island, specifically through additional early evening heat input, and by modifying the urban boundary layer structure through increased turbulence.

Latent-Trait Latent-Class Analysis of Self-disclosure in the Work Environment

NARCIS (Netherlands)

Maij - de Meij, A.M.; Kelderman, H.; van der Flier, H.

2005-01-01

Based on the literature about self-disclosure, it was hypothesized that different groups of subjects differ in their pattern of self-disclosure with respect to different areas of social interaction. An extended latent-trait latent-class model was proposed to describe these general patterns of

Latent classification models

DEFF Research Database (Denmark)

Langseth, Helge; Nielsen, Thomas Dyhre

2005-01-01

parametric family ofdistributions.  In this paper we propose a new set of models forclassification in continuous domains, termed latent classificationmodels. The latent classification model can roughly be seen ascombining the \\NB model with a mixture of factor analyzers,thereby relaxing the assumptions...... classification model, and wedemonstrate empirically that the accuracy of the proposed model issignificantly higher than the accuracy of other probabilisticclassifiers....

Estimation of respiratory heat flows in prediction of heat strain among Taiwanese steel workers.

Science.gov (United States)

Chen, Wang-Yi; Juang, Yow-Jer; Hsieh, Jung-Yu; Tsai, Perng-Jy; Chen, Chen-Peng

2017-01-01

International Organization for Standardization 7933 standard provides evaluation of required sweat rate (RSR) and predicted heat strain (PHS). This study examined and validated the approximations in these models estimating respiratory heat flows (RHFs) via convection (C res ) and evaporation (E res ) for application to Taiwanese foundry workers. The influence of change in RHF approximation to the validity of heat strain prediction in these models was also evaluated. The metabolic energy consumption and physiological quantities of these workers performing at different workloads under elevated wet-bulb globe temperature (30.3 ± 2.5 °C) were measured on-site and used in the calculation of RHFs and indices of heat strain. As the results show, the RSR model overestimated the C res for Taiwanese workers by approximately 3 % and underestimated the E res by 8 %. The C res approximation in the PHS model closely predicted the convective RHF, while the E res approximation over-predicted by 11 %. Linear regressions provided better fit in C res approximation (R 2  = 0.96) than in E res approximation (R 2  ≤ 0.85) in both models. The predicted C res deviated increasingly from the observed value when the WBGT reached 35 °C. The deviations of RHFs observed for the workers from those predicted using the RSR or PHS models did not significantly alter the heat loss via the skin, as the RHFs were in general of a level less than 5 % of the metabolic heat consumption. Validation of these approximations considering thermo-physiological responses of local workers is necessary for application in scenarios of significant heat exposure.

Estimation of surface absorptivity in laser surface heating process with experimental data

International Nuclear Information System (INIS)

Chen, H-T; Wu, X-Y

2006-01-01

This study applies a hybrid technique of the Laplace transform and finite-difference methods in conjunction with the least-squares method and experimental temperature data inside the test material to predict the unknown surface temperature, heat flux and absorptivity for various surface conditions in the laser surface heating process. In this study, the functional form of the surface temperature is unknown a priori and is assumed to be a function of time before performing the inverse calculation. In addition, the whole time domain is divided into several analysis sub-time intervals and then these unknown estimates on each analysis interval can be predicted. In order to show the accuracy of the present inverse method, comparisons are made among the present estimates, direct results and previous results, showing that the present estimates agree with the direct results for the simulated problem. However, the present estimates of the surface absorptivity deviate slightly from previous estimated results under the assumption of constant thermal properties. The effect of the surface conditions on the surface absorptivity and temperature is not negligible

Estimation of the temperature, heat gain and heat loss by solar parabolic trough collector under Algerian climate using different thermal oils

International Nuclear Information System (INIS)

Ouagued, Malika; Khellaf, Abdallah; Loukarfi, Larbi

2013-01-01

Highlights: • Estimation of direct solar radiations for different tracking systems at six typical locations in Algeria. • PTC thermal model uses energy balances from the HTF to the atmosphere. • The model depends on the collector type, nature of HTF, optical properties, and ambient conditions. • Estimation of temperature, heat gain and energy cost of thermal oils used in the model. • Comparison between monthly mean heat gain of the various thermal oils for six Algerian locations. - Abstract: Algeria is blessed with a very important renewable, and more particularly solar, energy potential. This potential opens for Algeria reel opportunities to cope with the increasing energy demand and the growing environmental problems link to the use of fossil fuel. In order to develop and to promote concrete actions in the areas of renewable energy and energy efficiency, Algeria has introduced a national daring program for the period 2011–2030. In this program, solar energy, and more particularly solar thermal energy plays an important role. In this paper, the potential of direct solar irradiance in Algeria and the performance of solar parabolic trough collector (PTC) are estimated under the climate conditions of the country. These two factors are treated as they play an important role in the design of solar thermal plant. In order to determine the most promising solar sites in Algeria, monthly mean daily direct solar radiation have been estimated and compared for different locations corresponding to different climatic region. Different tilted and tracking collectors are considered so as to determine the most efficient system for the PTC. In order to evaluate the performance of a tracking solar parabolic trough collector, a heat transfer model is developed. The receiver, heat collector element (HCE), is divided into several segments and heat balance is applied in each segment over a section of the solar receiver. Different oils are considered to determine the thermal

Heat experiment design to estimate temperature dependent thermal properties

International Nuclear Information System (INIS)

Romanovski, M

2008-01-01

Experimental conditions are studied to optimize transient experiments for estimating temperature dependent thermal conductivity and volumetric heat capacity. A mathematical model of a specimen is the one-dimensional heat equation with boundary conditions of the second kind. Thermal properties are assumed to vary nonlinearly with temperature. Experimental conditions refer to the thermal loading scheme, sampling times and sensor location. A numerical model of experimental configurations is studied to elicit the optimal conditions. The numerical solution of the design problem is formulated on a regularization scheme with a stabilizer minimization without a regularization parameter. An explicit design criterion is used to reveal the optimal sensor location, heating duration and flux magnitude. Results obtained indicate that even the strongly nonlinear experimental design problem admits the aggregation of its solution and has a strictly defined optimal measurement scheme. Additional region of temperature measurements with allowable identification error is revealed.

Testing of PCM Heat Storage Modules with Solar Collectors as Heat Source

DEFF Research Database (Denmark)

Englmair, Gerald; Dannemand, Mark; Johansen, Jakob Berg

2016-01-01

A latent heat storage based on the phase change material Sodium Acetate Trihydrate (SAT) has been tested as part of a demonstration system. The full heat storage consisted of 4 individual modules each containing about 200 kg of sodium acetate trihydrate with different additives. The aim...... was to actively utilize the ability of the material to supercool to obtain long storage periods. The modules were charged with solar heat supplied by 22.4 m2 evacuated tubular collectors. The investigation showed that it was possible to fully charge one module within a period of 270 minutes with clear skies...

Specific heat and magnetization of a ZrB12 single crystal: characterization of a type II/1 superconductor

OpenAIRE

Wang, Yuxing; Lortz, Rolf; Paderno, Yuriy; Filippov, Vladimir; Abe, Satoko; Tutsch, Ulrich; Junod, Alain

2005-01-01

We measured the specific heat, the magnetization, and the magnetoresistance of a single crystal of ZrB12, which is superconducting below Tc ~ 6 K. The specific heat in zero field shows a BCS-type superconducting transition. The normal- to superconducting-state transition changes from first order (with a latent heat) to second order (without latent heat) with increasing magnetic field, indicating that the pure compound is a low-kappa, type-II/1 superconductor in the classification of Auer and ...

Estimating heats of detonation and detonation velocities of aromatic energetic compounds

Energy Technology Data Exchange (ETDEWEB)

Keshavarz, Mohammad Hossein [Department of Chemistry, Malek-ashtar University of Technology, Shahin-shahr, P. O. Box 83145/115 (Iran)

2008-12-15

A new method is introduced to predict reliable estimation of heats of detonation of aromatic energetic compounds. At first step, this procedure assumes that the heat of detonation of an explosive compound of composition C{sub a}H{sub b}N{sub c}O{sub d} can be approximated as the difference between the heat of formation of all H{sub 2}O-CO{sub 2} arbitrary (H{sub 2}O, CO{sub 2}, N{sub 2}) detonation products and that of the explosive, divided by the formula weight of the explosive. Overestimated results based on (H{sub 2}O-CO{sub 2} arbitrary) can be corrected in the next step. Predicted heats of detonation of pure energetic compounds with the product H{sub 2}O in the liquid state for 31 aromatic energetic compounds have a root mean square (rms) deviation of 2.08 and 0.34 kJ g{sup -1} from experiment for (H{sub 2}O-CO{sub 2} arbitrary) and new method, respectively. The new method also gives good results as compared to the second sets of decomposition products, which consider H{sub 2},N{sub 2}, H{sub 2}O,CO, and CO{sub 2} as major gaseous products. It is shown here how the predicted heats of detonation by the new method can be used to obtain reliable estimation of detonation velocity over a wide range of loading densities. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Estimate of the global-scale joule heating rates in the thermosphere due to time mean currents

International Nuclear Information System (INIS)

Roble, R.G.; Matsushita, S.

1975-01-01

An estimate of the global-scale joule heating rates in the thermosphere is made based on derived global equivalent overhead electric current systems in the dynamo region during geomagnetically quiet and disturbed periods. The equivalent total electric field distribution is calculated from Ohm's law. The global-scale joule heating rates are calculated for various monthly average periods in 1965. The calculated joule heating rates maximize at high latitudes in the early evening and postmidnight sectors. During geomagnetically quiet times the daytime joule heating rates are considerably lower than heating by solar EUV radiation. However, during geomagnetically disturbed periods the estimated joule heating rates increase by an order of magnitude and can locally exceed the solar EUV heating rates. The results show that joule heating is an important and at times the dominant energy source at high latitudes. However, the global mean joule heating rates calculated near solar minimum are generally small compared to the global mean solar EUV heating rates. (auth)

Robust Measurement via A Fused Latent and Graphical Item Response Theory Model.

Science.gov (United States)

Chen, Yunxiao; Li, Xiaoou; Liu, Jingchen; Ying, Zhiliang

2018-03-12

Item response theory (IRT) plays an important role in psychological and educational measurement. Unlike the classical testing theory, IRT models aggregate the item level information, yielding more accurate measurements. Most IRT models assume local independence, an assumption not likely to be satisfied in practice, especially when the number of items is large. Results in the literature and simulation studies in this paper reveal that misspecifying the local independence assumption may result in inaccurate measurements and differential item functioning. To provide more robust measurements, we propose an integrated approach by adding a graphical component to a multidimensional IRT model that can offset the effect of unknown local dependence. The new model contains a confirmatory latent variable component, which measures the targeted latent traits, and a graphical component, which captures the local dependence. An efficient proximal algorithm is proposed for the parameter estimation and structure learning of the local dependence. This approach can substantially improve the measurement, given no prior information on the local dependence structure. The model can be applied to measure both a unidimensional latent trait and multidimensional latent traits.

Non-destructive forensic latent fingerprint acquisition with chromatic white light sensors

Science.gov (United States)

Leich, Marcus; Kiltz, Stefan; Dittmann, Jana; Vielhauer, Claus

2011-02-01

Non-destructive latent fingerprint acquisition is an emerging field of research, which, unlike traditional methods, makes latent fingerprints available for additional verification or further analysis like tests for substance abuse or age estimation. In this paper a series of tests is performed to investigate the overall suitability of a high resolution off-the-shelf chromatic white light sensor for the contact-less and non-destructive latent fingerprint acquisition. Our paper focuses on scanning previously determined regions with exemplary acquisition parameter settings. 3D height field and reflection data of five different latent fingerprints on six different types of surfaces (HDD platter, brushed metal, painted car body (metallic and non-metallic finish), blued metal, veneered plywood) are experimentally studied. Pre-processing is performed by removing low-frequency gradients. The quality of the results is assessed subjectively; no automated feature extraction is performed. Additionally, the degradation of the fingerprint during the acquisition period is observed. While the quality of the acquired data is highly dependent on surface structure, the sensor is capable of detecting the fingerprint on all sample surfaces. On blued metal the residual material is detected; however, the ridge line structure dissolves within minutes after fingerprint placement.

Exact solution for a two-phase Stefan problem with variable latent heat and a convective boundary condition at the fixed face

Science.gov (United States)

Bollati, Julieta; Tarzia, Domingo A.

2018-04-01

Recently, in Tarzia (Thermal Sci 21A:1-11, 2017) for the classical two-phase Lamé-Clapeyron-Stefan problem an equivalence between the temperature and convective boundary conditions at the fixed face under a certain restriction was obtained. Motivated by this article we study the two-phase Stefan problem for a semi-infinite material with a latent heat defined as a power function of the position and a convective boundary condition at the fixed face. An exact solution is constructed using Kummer functions in case that an inequality for the convective transfer coefficient is satisfied generalizing recent works for the corresponding one-phase free boundary problem. We also consider the limit to our problem when that coefficient goes to infinity obtaining a new free boundary problem, which has been recently studied in Zhou et al. (J Eng Math 2017. https://doi.org/10.1007/s10665-017-9921-y).

Heat flux estimation for neutral beam line components using inverse heat conduction procedures

International Nuclear Information System (INIS)

Bharathi, P.; Prahlad, V.; Quereshi, K.; Bansal, L.K.; Rambabu, S.; Sharma, S.K.; Parmar, S.; Patel, P.J.; Baruah, U.K.; Patel, Ravi

2015-01-01

In this work, we describe and compare the analytical IHCP methods such-as semi-infinite method, finite slab method and a numerical method called Stolz method for estimating the incident heat flux from the experimentally measured temperature data. In case of analytical methods, the finite time response of the sensor is needed to be accounted for an accurate power density estimations. The modified models corrected for the response time of the sensors are also discussed in this paper. Application of these methods using example temperature waveforms obtained on the SST1-NBI test stand is presented and discussed. For choosing the suitable method for the calorimetry on beam line components, the estimated results are also validated using the ANSYS analysis done on these beam Iine components. As a conclusion, the finite slab method corrected for the influence of the sensor response time found out to be the most suitable method for the inversion of temperature data in case of neutral beam line components

Transcriptional regulation of latent feline immunodeficiency virus in peripheral CD4+ T-lymphocytes.

Science.gov (United States)

McDonnel, Samantha J; Sparger, Ellen E; Luciw, Paul A; Murphy, Brian G

2012-05-01

Feline immunodeficiency virus (FIV), the lentivirus of domestic cats responsible for feline AIDS, establishes a latent infection in peripheral blood CD4+ T-cells approximately eight months after experimental inoculation. In this study, cats experimentally infected with the FIV-C strain in the asymptomatic phase demonstrated an estimated viral load of 1 infected cell per approximately 10(3) CD4+ T-cells, with about 1 copy of viral DNA per cell. Approximately 1 in 10 proviral copies was capable of transcription in the asymptomatic phase. The latent FIV proviral promoter was associated with deacetylated, methylated histones, which is consistent with a condensed chromatin structure. In contrast, the transcriptionally active FIV promoter was associated with histone acetylation and demethylation. In addition, RNA polymerase II appeared to be paused on the latent viral promoter, and short promoter-proximal transcripts were detected. Our findings for the FIV promoter in infected cats are similar to results obtained in studies of human immunodeficiency virus (HIV)-1 latent proviruses in cell culture in vitro studies. Thus, the FIV/cat model may offer insights into in vivo mechanisms of HIV latency and provides a unique opportunity to test novel therapeutic interventions aimed at eradicating latent virus.

Investigations of the corrosion behaviour of special heat exchanging materials in sodium acetate trihydrate melt for the application latent heat storage; Untersuchungen des Korrosionsverhaltens ausgewaehlter Waermeaustauscherwerkstoffe in Natriumacetat-Trihydrat-Schmelze fuer den Anwendungsfall Latentwaermespeichersysteme

Energy Technology Data Exchange (ETDEWEB)

Brandt, B.; Stimming, U. [ZAE Bayern, Walter-Meissner-Str. 6, 87748 Garching (Germany)

2004-06-01

The development activities in the area of latent heat storage have more and more increased in the last years. The reason is the search for new energy storage systems of higher energy efficiency and the reinforced utilisation of renewable and alternative energies which are often only irregularly available. The special advantage of latent heat storage is the high energy storage density which could be reached at the melting point of selected storage materials and the resulting reduction of required space respectively the nearly constant temperature. An important topic relating to the development of these storage systems was the investigation of the long time stability, especially the corrosion stability. At the same time the heat exchange material has the function to transfer the heat and coldness from a heat transfer medium, e. g. water which has drawn the energy from an external source to the storage material. Among the storage materials the sodium acetate trihydrate (melting point: 58 C) has interesting advantages. In that reason the investigation of the corrosion behaviour and the choose of suitable materials for heat exchangers was an important goal. In the present report important results of the investigation of selected metals at 80 C in sodium acetate trihydrate are described. The corrosion influencing impurities chloride, sulphate and carbonate which could be contained in the much more inexpensive salt hydrate of technical quality were added to the analytically pure sodium acetate trihydrate. Furthermore the addition of graphite (for increasing the heat conductivity) and the contact with air were investigated. Some promising metals of high corrosion resistance are the result of the investigations. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] In den letzten Jahren haben sich die Entwicklungsaktivitaeten auf dem Gebiet der Latentwaermespeicherung erheblich verstaerkt. Grund dafuer ist die Suche nach Energiespeichern mit hoeherer Effizienz und

Energy-Storage Modules for Active Solar Heating and Cooling

Science.gov (United States)

Parker, J. C.

1982-01-01

34 page report describes a melting salt hydrate that stores 12 times as much heat as rocks and other heavy materials. Energy is stored mostly as latent heat; that is, heat that can be stored and recovered without any significant change in temperature. Report also describes development, evaluation and testing of permanently sealed modules containing salt hydrate mixture.

Temporal and spatial changes in mixed layer properties and atmospheric net heat flux in the Nordic Seas

International Nuclear Information System (INIS)

Smirnov, A; Alekseev, G; Korablev, A; Esau, I

2010-01-01

The Nordic Seas are an important area of the World Ocean where warm Atlantic waters penetrate far north forming the mild climate of Northern Europe. These waters represent the northern rim of the global thermohaline circulation. Estimates of the relationships between the net heat flux and mixed layer properties in the Nordic Seas are examined. Oceanographic data are derived from the Oceanographic Data Base (ODB) compiled in the Arctic and Antarctic Research Institute. Ocean weather ship 'Mike' (OWS) data are used to calculate radiative and turbulent components of the net heat flux. The net shortwave flux was calculated using a satellite albedo dataset and the EPA model. The net longwave flux was estimated by Southampton Oceanography Centre (SOC) method. Turbulent fluxes at the air-sea interface were calculated using the COARE 3.0 algorithm. The net heat flux was calculated by using oceanographic and meteorological data of the OWS 'Mike'. The mixed layer depth was estimated for the period since 2002 until 2009 by the 'Mike' data as well. A good correlation between these two parameters has been found. Sensible and latent heat fluxes controlled by surface air temperature/sea surface temperature gradient are the main contributors into net heat flux. Significant correlation was found between heat fluxes variations at the OWS 'Mike' location and sea ice export from the Arctic Ocean.

Temporal and spatial changes in mixed layer properties and atmospheric net heat flux in the Nordic Seas

Energy Technology Data Exchange (ETDEWEB)

Smirnov, A; Alekseev, G [SI ' Arctic and Antarctic Research Institute' , St. Petersburg (Russian Federation); Korablev, A; Esau, I, E-mail: avsmir@aari.nw.r [Nansen Environmental and Remote Sensing Centre, Bergen (Norway)

2010-08-15

The Nordic Seas are an important area of the World Ocean where warm Atlantic waters penetrate far north forming the mild climate of Northern Europe. These waters represent the northern rim of the global thermohaline circulation. Estimates of the relationships between the net heat flux and mixed layer properties in the Nordic Seas are examined. Oceanographic data are derived from the Oceanographic Data Base (ODB) compiled in the Arctic and Antarctic Research Institute. Ocean weather ship 'Mike' (OWS) data are used to calculate radiative and turbulent components of the net heat flux. The net shortwave flux was calculated using a satellite albedo dataset and the EPA model. The net longwave flux was estimated by Southampton Oceanography Centre (SOC) method. Turbulent fluxes at the air-sea interface were calculated using the COARE 3.0 algorithm. The net heat flux was calculated by using oceanographic and meteorological data of the OWS 'Mike'. The mixed layer depth was estimated for the period since 2002 until 2009 by the 'Mike' data as well. A good correlation between these two parameters has been found. Sensible and latent heat fluxes controlled by surface air temperature/sea surface temperature gradient are the main contributors into net heat flux. Significant correlation was found between heat fluxes variations at the OWS 'Mike' location and sea ice export from the Arctic Ocean.

Heat transfer and evaporative cooling in the function of pot-in-pot coolers

Science.gov (United States)

Chemin, Arsène; Levy Dit Vehel, Victor; Caussarieu, Aude; Plihon, Nicolas; Taberlet, Nicolas

2018-03-01

A pot-in-pot cooler is an affordable electricity-free refrigerator which uses the latent heat of vaporization of water to maintain a low temperature inside an inner compartment. In this article, we experimentally investigate the influence of the main physical parameters in model pot-in-pot coolers. The effect of the wind on the evaporation rate of the cooling fluid is studied in model experiments while the influence of the fluid properties (thermal conductivity, specific heat, and latent heat) is elucidated using a variety of cooling fluids (water, ethanol, and ether). A model based on a simplified heat conduction equation is proposed and is shown to be in good quantitative agreement with the experimental measurements.

Large differences in the diabatic heat budget of the tropical UTLS in reanalyses

Science.gov (United States)

Wright, J. S.; Fueglistaler, S.

2013-04-01

We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: MERRA, ERA-Interim, CFSR, JRA-25/JCDAS, and NCEP/NCAR. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Although they may be expected given difficulties in representing moist convection in models, the discrepancies in latent heating are still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention).

Pipeline heating method based on optimal control and state estimation

Energy Technology Data Exchange (ETDEWEB)

Vianna, F.L.V. [Dept. of Subsea Technology. Petrobras Research and Development Center - CENPES, Rio de Janeiro, RJ (Brazil)], e-mail: fvianna@petrobras.com.br; Orlande, H.R.B. [Dept. of Mechanical Engineering. POLI/COPPE, Federal University of Rio de Janeiro - UFRJ, Rio de Janeiro, RJ (Brazil)], e-mail: helcio@mecanica.ufrj.br; Dulikravich, G.S. [Dept. of Mechanical and Materials Engineering. Florida International University - FIU, Miami, FL (United States)], e-mail: dulikrav@fiu.edu

2010-07-01

In production of oil and gas wells in deep waters the flowing of hydrocarbon through pipeline is a challenging problem. This environment presents high hydrostatic pressures and low sea bed temperatures, which can favor the formation of solid deposits that in critical operating conditions, as unplanned shutdown conditions, may result in a pipeline blockage and consequently incur in large financial losses. There are different methods to protect the system, but nowadays thermal insulation and chemical injection are the standard solutions normally used. An alternative method of flow assurance is to heat the pipeline. This concept, which is known as active heating system, aims at heating the produced fluid temperature above a safe reference level in order to avoid the formation of solid deposits. The objective of this paper is to introduce a Bayesian statistical approach for the state estimation problem, in which the state variables are considered as the transient temperatures within a pipeline cross-section, and to use the optimal control theory as a design tool for a typical heating system during a simulated shutdown condition. An application example is presented to illustrate how Bayesian filters can be used to reconstruct the temperature field from temperature measurements supposedly available on the external surface of the pipeline. The temperatures predicted with the Bayesian filter are then utilized in a control approach for a heating system used to maintain the temperature within the pipeline above the critical temperature of formation of solid deposits. The physical problem consists of a pipeline cross section represented by a circular domain with four points over the pipe wall representing heating cables. The fluid is considered stagnant, homogeneous, isotropic and with constant thermo-physical properties. The mathematical formulation governing the direct problem was solved with the finite volume method and for the solution of the state estimation problem

Latent-Trait Latent-Class Analysis of Self-Disclosure in the Work Environment

Science.gov (United States)

Maij-de Meij, Annette M.; Kelderman, Henk; van der Flier, Henk

2005-01-01

Based on the literature about self-disclosure, it was hypothesized that different groups of subjects differ in their pattern of self-disclosure with respect to different areas of social interaction. An extended latent-trait latent-class model was proposed to describe these general patterns of self-disclosure. The model was used to analyze the data…

Improved solar heating systems

Science.gov (United States)

Schreyer, J.M.; Dorsey, G.F.

1980-05-16

An improved solar heating system is described in which the incident radiation of the sun is absorbed on collector panels, transferred to a storage unit and then distributed as heat for a building and the like. The improvement is obtained by utilizing a storage unit comprising separate compartments containing an array of materials having different melting points ranging from 75 to 180/sup 0/F. The materials in the storage system are melted in accordance with the amount of heat absorbed from the sun and then transferred to the storage system. An efficient low volume storage system is provided by utilizing the latent heat of fusion of the materials as they change states in storing ad releasing heat for distribution.

Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data

Science.gov (United States)

Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.

2006-01-01

Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.

Estimation of test characteristics of real-time PCR and bacterial culture for diagnosis of subclinical intramammary infections with Streptococcus agalactiae in Danish dairy cattle in 2012 using latent class analysis.

Science.gov (United States)

Mahmmod, Yasser S; Toft, Nils; Katholm, Jørgen; Grønbæk, Carsten; Klaas, Ilka C

2013-05-01

The misdiagnosis of intramammary infections (IMI) with Streptococcus agalactiae (S. agalactiae) could lead farmers to treat or cull animals unnecessarily. The objective of this field study was to estimate the sensitivity (Se) and specificity (Sp) of real-time PCR at different cut-offs for cycle threshold (Ct) values against bacterial culture (BC) for diagnosis of S. agalactiae IMI using latent class analysis to avoid the assumption of a perfect reference test. A total of 614 dairy cows were randomly selected from 6 herds with bulk tank PCR Ct value ≤ 39 for S. agalactiae and S. aureus. At milk recording, 2456 quarter milk samples were taken aseptically for BC and the routinely taken cow level milk samples were analyzed by PCR. Results showed that 53 cows (8.6%) were positive for S. agalactiae IMI by BC. Sensitivity of PCR at cut-offs; ≤ 39, ≤ 37, ≤ 34, and ≤ 32, was 96.2%, 91.9%, 87.2% and 73.9%, while Se of BC was 25.7%, 29.9%, 59.9% and 72.1%. Specificity of PCR at cut-offs; ≤ 39, ≤ 37, ≤ 34, and ≤ 32, was 96.8%, 96.9%, 96.7%, and 97.22%, while Sp of BC was 99.7%, 99.5%, 99.2%, and 98.9%. The estimated prevalence of S. agalactiae IMI by PCR was higher than the apparent prevalence at the tested cut-offs, indicating under estimation of S. agalactiae IMI in the examined dairy cows. In conclusion, Se of PCR is always higher than Se of BC at all tested cut-offs. The lower cut-off, the more comparable becomes Se of PCR and Se of BC. The changes in Se in both PCR and BC at different Ct-value cut-offs may indicate a change in the definition of the latent infection. The similar Se of both tests at cut-off ≤ 32 may indicate high concentrations of S. agalactiae viable cells, representing a cow truly/heavily infected with S. agalactiae and thus easier to detect with BC. At cut-off ≤ 39 the latent definition of infection may reflect a more general condition of cows being positive for S. agalactiae. Our findings indicate that PCR Ct-value cut-offs should

Local heat transfer estimation in microchannels during convective boiling under microgravity conditions: 3D inverse heat conduction problem using BEM techniques

Science.gov (United States)

Luciani, S.; LeNiliot, C.

2008-11-01

Two-phase and boiling flow instabilities are complex, due to phase change and the existence of several interfaces. To fully understand the high heat transfer potential of boiling flows in microscale's geometry, it is vital to quantify these transfers. To perform this task, an experimental device has been designed to observe flow patterns. Analysis is made up by using an inverse method which allows us to estimate the local heat transfers while boiling occurs inside a microchannel. In our configuration, the direct measurement would impair the accuracy of the searched heat transfer coefficient because thermocouples implanted on the surface minichannels would disturb the established flow. In this communication, we are solving a 3D IHCP which consists in estimating using experimental data measurements the surface temperature and the surface heat flux in a minichannel during convective boiling under several gravity levels (g, 1g, 1.8g). The considered IHCP is formulated as a mathematical optimization problem and solved using the boundary element method (BEM).

Estimation of Surface Temperature and Heat Flux by Inverse Heat Transfer Methods Using Internal Temperatures Measured While Radiantly Heating a Carbon/Carbon Specimen up to 1920 F

Science.gov (United States)

Pizzo, Michelle; Daryabeigi, Kamran; Glass, David

2015-01-01

The ability to solve the heat conduction equation is needed when designing materials to be used on vehicles exposed to extremely high temperatures; e.g. vehicles used for atmospheric entry or hypersonic flight. When using test and flight data, computational methods such as finite difference schemes may be used to solve for both the direct heat conduction problem, i.e., solving between internal temperature measurements, and the inverse heat conduction problem, i.e., using the direct solution to march forward in space to the surface of the material to estimate both surface temperature and heat flux. The completed research first discusses the methods used in developing a computational code to solve both the direct and inverse heat transfer problems using one dimensional, centered, implicit finite volume schemes and one dimensional, centered, explicit space marching techniques. The developed code assumed the boundary conditions to be specified time varying temperatures and also considered temperature dependent thermal properties. The completed research then discusses the results of analyzing temperature data measured while radiantly heating a carbon/carbon specimen up to 1920 F. The temperature was measured using thermocouple (TC) plugs (small carbon/carbon material specimens) with four embedded TC plugs inserted into the larger carbon/carbon specimen. The purpose of analyzing the test data was to estimate the surface heat flux and temperature values from the internal temperature measurements using direct and inverse heat transfer methods, thus aiding in the thermal and structural design and analysis of high temperature vehicles.

Modeling Nonlinear Change via Latent Change and Latent Acceleration Frameworks: Examining Velocity and Acceleration of Growth Trajectories

Science.gov (United States)

Grimm, Kevin; Zhang, Zhiyong; Hamagami, Fumiaki; Mazzocco, Michele

2013-01-01

We propose the use of the latent change and latent acceleration frameworks for modeling nonlinear growth in structural equation models. Moving to these frameworks allows for the direct identification of "rates of change" and "acceleration" in latent growth curves--information available indirectly through traditional growth…

Surface layer scintillometry for estimating the sensible heat flux component of the surface energy balance

Directory of Open Access Journals (Sweden)

M. J. Savage

2010-01-01

Full Text Available The relatively recently developed scintillometry method, with a focus on the dual-beam surface layer scintillometer (SLS, allows boundary layer atmospheric turbulence, surface sensible heat and momentum flux to be estimated in real-time. Much of the previous research using the scintillometer method has involved the large aperture scintillometer method, with only a few studies using the SLS method. The SLS method has been mainly used by agrometeorologists, hydrologists and micrometeorologists for atmospheric stability and surface energy balance studies to obtain estimates of sensible heat from which evaporation estimates representing areas of one hectare or larger are possible. Other applications include the use of the SLS method in obtaining crucial input parameters for atmospheric dispersion and turbulence models. The SLS method relies upon optical scintillation of a horizontal laser beam between transmitter and receiver for a separation distance typically between 50 and 250 m caused by refractive index inhomogeneities in the atmosphere that arise from turbulence fluctuations in air temperature and to a much lesser extent the fluctuations in water vapour pressure. Measurements of SLS beam transmission allow turbulence of the atmosphere to be determined, from which sub-hourly, real-time and in situ path-weighted fluxes of sensible heat and momentum may be calculated by application of the Monin-Obukhov similarity theory. Unlike the eddy covariance (EC method for which corrections for flow distortion and coordinate rotation are applied, no corrections to the SLS measurements, apart from a correction for water vapour pressure, are applied. Also, path-weighted SLS estimates over the propagation path are obtained. The SLS method also offers high temporal measurement resolution and usually greater spatial coverage compared to EC, Bowen ratio energy balance, surface renewal and other sensible heat measurement methods. Applying the shortened surface

Reconstruction of temporal variations of evapotranspiration using instantaneous estimates at the time of satellite overpass

Directory of Open Access Journals (Sweden)

E. Delogu

2012-08-01

Full Text Available Evapotranspiration estimates can be derived from remote sensing data and ancillary, mostly meterorological, information. For this purpose, two types of methods are classically used: the first type estimates a potential evapotranspiration rate from vegetation indices, and adjusts this rate according to water availability derived from either a surface temperature index or a first guess obtained from a rough estimate of the water budget, while the second family of methods relies on the link between the surface temperature and the latent heat flux through the surface energy budget. The latter provides an instantaneous estimate at the time of satellite overpass. In order to compute daily evapotranspiration, one needs an extrapolation algorithm. Since no image is acquired during cloudy conditions, these methods can only be applied during clear sky days. In order to derive seasonal evapotranspiration, one needs an interpolation method. Two combined interpolation/extrapolation methods based on the self preservation of evaporative fraction and the stress factor are compared to reconstruct seasonal evapotranspiration from instantaneous measurements acquired in clear sky conditions. Those measurements are taken from instantaneous latent heat flux from 11 datasets in Southern France and Morocco. Results show that both methods have comparable performances with a clear advantage for the evaporative fraction for datasets with several water stress events. Both interpolation algorithms tend to underestimate evapotranspiration due to the energy limiting conditions that prevail during cloudy days. Taking into account the diurnal variations of the evaporative fraction according to an empirical relationship derived from a previous study improved the performance of the extrapolation algorithm and therefore the retrieval of the seasonal evapotranspiration for all but one datasets.

The dry-heat loss effect of melt-spun phase change material fibres.

Science.gov (United States)

Tjønnås, Maria Suong; Færevik, Hilde; Sandsund, Mariann; Reinertsen, Randi E

2015-01-01

Phase change materials (PCM) have the ability to store latent heat when they change phases, a property that gives clothing that incorporates PCM its cooling effect. This study investigated the effect of dry-heat loss (cooling) of a novel melt-spun PCM fibre on the basis of the area covered, mass, the latent heat of fusion and melting temperature, compared to a known PCM clothing product. PCM fibres with melting temperatures of 28.4 and 32.0°C and PCM packs with melting temperatures of 28.0 and 32.0°C were studied. The results showed that the PCM fibres had a larger initial peak cooling effect than that of the PCM packs. The duration of the cooling effect of PCM fibres was primarily dependent on the PCM mass and the latent heat of fusion capacity, and secondly on the covered area and melting temperature of the PCM. This study investigates the cooling effect of PCM fibres on a thermal manikin. The PCM fibres had a high but short-lasting cooling effect. This study contributes to the knowledge of how the body's temperature regulation may be affected by the cooling properties of clothing that incorporates PCM.

On estimation of reliability for pipe lines of heat power plants under cyclic loading

International Nuclear Information System (INIS)

Verezemskij, V.G.

1986-01-01

One of the possible methods to obtain a quantitative estimate of the reliability for pipe lines of the welded heat power plants under cyclic loading due to heating-cooling and due to vibration is considered. Reliability estimate is carried out for a common case of loading by simultaneous cycles with different amplitudes and loading asymmetry. It is shown that scattering of the breaking number of cycles for the metal of welds may perceptibly decrease reliability of the welded pipe line

Regularization and error estimates for nonhomogeneous backward heat problems

Directory of Open Access Journals (Sweden)

Duc Trong Dang

2006-01-01

Full Text Available In this article, we study the inverse time problem for the non-homogeneous heat equation which is a severely ill-posed problem. We regularize this problem using the quasi-reversibility method and then obtain error estimates on the approximate solutions. Solutions are calculated by the contraction principle and shown in numerical experiments. We obtain also rates of convergence to the exact solution.

The Urban Tree as a Tool to Mitigate the Urban Heat Island in Mexico City: A Simple Phenomenological Model.

Science.gov (United States)

Ballinas, Mónica; Barradas, Víctor L

2016-01-01

The urban heat island (UHI) is mainly a nocturnal phenomenon, but it also appears during the day in Mexico City. The UHI may affect human thermal comfort, which can influence human productivity and morbidity in the spring/summer period. A simple phenomenological model based on the energy balance was developed to generate theoretical support of UHI mitigation in Mexico City focused on the latent heat flux change by increasing tree coverage to reduce sensible heat flux and air temperature. Half-hourly data of the urban energy balance components were generated in a typical residential/commercial neighborhood of Mexico City and then parameterized using easily measured variables (air temperature, humidity, pressure, and visibility). Canopy conductance was estimated every hour in four tree species, and transpiration was estimated using sap flow technique and parameterized by the envelope function method. Averaged values of net radiation, energy storage, and sensible and latent heat flux were around 449, 224, 153, and 72 W m, respectively. Daily tree transpiration ranged from 3.64 to 4.35 Ld. To reduce air temperature by 1°C in the studied area, 63 large would be required per hectare, whereas to reduce the air temperature by 2°C only 24 large trees would be required. This study suggests increasing tree canopy cover in the city cannot mitigate UHI adequately but requires choosing the most appropriate tree species to solve this problem. It is imperative to include these types of studies in tree selection and urban development planning to adequately mitigate UHI. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Enhancement of melting heat transfer of ice slurries by an injection flow in a rectangular cross sectional horizontal duct

International Nuclear Information System (INIS)

Fujii, Kota; Yamada, Masahiko

2013-01-01

Ice slurries are now commonly used as cold thermal storage materials, and have the potential to be applied to other engineering fields such as quenching metals to control properties, emergency cooling systems, and preservation of food and biomaterials at low temperatures. Although ice slurries have been widely utilized because of their high thermal storage densities, previous studies have revealed that the latent heat of ice particles is not completely released on melting because of insufficient contact between the ice particles and a heated surface. In this study, an injection flow that was bifurcated from the main flow of an ice slurry was employed to promote melting heat transfer of ice particles on a horizontal heated surface. The effects of injection angle and injection flow rate on local heat transfer coefficients and heat transfer coefficient ratios were determined experimentally. The results show that from two to three times higher heat transfer coefficients can be obtained by using large injection flow rates and injection angles. However, low injection angles improved the utilization rate of the latent heat of ice near the injection point by approximately a factor of two compared to that without injection. -- Highlights: • Melting of ice slurries were enhanced by the injection under constant total flow rate. • Contribution of ice particles and their latent heat to heat transfer was investigated. • Effect of velocity ratio of injection to that of main flow was examined. • Effect of the angle of injection flow to the main flow was also examined. • Appropriate conditions for the use of latent heat of ice and heat transfer did not coincide

Active space cooling with night-coldness - development of a decentralized ventilation system with latent heat storage; Aktive Raumkuehlung mit Nachkaelte - Entwicklung eines dezentralen Lueftungsgeraetes mit Latentwaermespeicher. Imtech-Haus, Hamburg Referenzanlage

Energy Technology Data Exchange (ETDEWEB)

Luedemann, B.; Detzer, R. [Imtech Deutschland, Hamburg (Germany)

2007-04-15

Imtech Germany a decentralized ventilation system with a latent heat-storage unit made of Phase Change Material. The equipment was used successfully in a first reference asset in the Imtech house in Hamburg. During the day active space cooling is realized by storage of night-cold. In combination with a night ventilation the attached areas could be held continuous within the comfort range under 26 C under normal summer conditions. The decentralized ventilation system including control is developed to series production readiness and will be introduced now on the market. (orig.)

Transcriptional Regulation of Latent Feline Immunodeficiency Virus in Peripheral CD4+ T-lymphocytes

Directory of Open Access Journals (Sweden)

Brian G. Murphy

2012-05-01

Full Text Available Feline immunodeficiency virus (FIV, the lentivirus of domestic cats responsible for feline AIDS, establishes a latent infection in peripheral blood CD4+ T-cells approximately eight months after experimental inoculation. In this study, cats experimentally infected with the FIV-C strain in the asymptomatic phase demonstrated an estimated viral load of 1 infected cell per approximately 10³ CD4+ T-cells, with about 1 copy of viral DNA per cell. Approximately 1 in 10 proviral copies was capable of transcription in the asymptomatic phase. The latent FIV proviral promoter was associated with deacetylated, methylated histones, which is consistent with a condensed chromatin structure. In contrast, the transcriptionally active FIV promoter was associated with histone acetylation and demethylation. In addition, RNA polymerase II appeared to be paused on the latent viral promoter, and short promoter-proximal transcripts were detected. Our findings for the FIV promoter in infected cats are similar to results obtained in studies of human immunodeficiency virus (HIV-1 latent proviruses in cell culture in vitro studies. Thus, the FIV/cat model may offer insights into in vivo mechanisms of HIV latency and provides a unique opportunity to test novel therapeutic interventions aimed at eradicating latent virus.

On the Estimation of Disease Prevalence by Latent Class Models for Screening Studies Using Two Screening Tests with Categorical Disease Status Verified in Test Positives Only

Science.gov (United States)

Chu, Haitao; Zhou, Yijie; Cole, Stephen R.; Ibrahim, Joseph G.

2010-01-01

Summary To evaluate the probabilities of a disease state, ideally all subjects in a study should be diagnosed by a definitive diagnostic or gold standard test. However, since definitive diagnostic tests are often invasive and expensive, it is generally unethical to apply them to subjects whose screening tests are negative. In this article, we consider latent class models for screening studies with two imperfect binary diagnostic tests and a definitive categorical disease status measured only for those with at least one positive screening test. Specifically, we discuss a conditional independent and three homogeneous conditional dependent latent class models and assess the impact of misspecification of the dependence structure on the estimation of disease category probabilities using frequentist and Bayesian approaches. Interestingly, the three homogeneous dependent models can provide identical goodness-of-fit but substantively different estimates for a given study. However, the parametric form of the assumed dependence structure itself is not “testable” from the data, and thus the dependence structure modeling considered here can only be viewed as a sensitivity analysis concerning a more complicated non-identifiable model potentially involving heterogeneous dependence structure. Furthermore, we discuss Bayesian model averaging together with its limitations as an alternative way to partially address this particularly challenging problem. The methods are applied to two cancer screening studies, and simulations are conducted to evaluate the performance of these methods. In summary, further research is needed to reduce the impact of model misspecification on the estimation of disease prevalence in such settings. PMID:20191614

EPB standard EN ISO 52016: calculation of the building’s energy needs for heating and cooling, internal temperatures and heating and cooling load

NARCIS (Netherlands)

Dijk, H.A.L. van; Spiekman, M.E.; Hoes-van Oeffelen, E.C.M.

2016-01-01

EN ISO 52016-1 presents a coherent set of calculation methods at different levels of detail, for the (sensible) energy needs for the space heating and cooling and (latent) energy needs (de)humidification of a building and/or internal temperatures and heating and/or cooling loads, including the

Intraclass Correlation Coefficients in Hierarchical Designs: Evaluation Using Latent Variable Modeling

Science.gov (United States)

Raykov, Tenko

2011-01-01

Interval estimation of intraclass correlation coefficients in hierarchical designs is discussed within a latent variable modeling framework. A method accomplishing this aim is outlined, which is applicable in two-level studies where participants (or generally lower-order units) are clustered within higher-order units. The procedure can also be…

Soil heat flux and day time surface energy balance closure

Indian Academy of Sciences (India)

Soil heat flux; surface energy balance; Bowen's ratio; sensible and latent ... The energy storage term for the soil layer 0–0.05 m is calculated and the ground heat ... When a new method that accounts for both soil thermal conduction and soil ...

Satellite data based approach for the estimation of anthropogenic heat flux over urban areas

Science.gov (United States)

Nitis, Theodoros; Tsegas, George; Moussiopoulos, Nicolas; Gounaridis, Dimitrios; Bliziotis, Dimitrios

2017-09-01

Anthropogenic effects in urban areas influence the thermal conditions in the environment and cause an increase of the atmospheric temperature. The cities are sources of heat and pollution, affecting the thermal structure of the atmosphere above them which results to the urban heat island effect. In order to analyze the urban heat island mechanism, it is important to estimate the anthropogenic heat flux which has a considerable impact on the urban energy budget. The anthropogenic heat flux is the result of man-made activities (i.e. traffic, industrial processes, heating/cooling) and thermal releases from the human body. Many studies have underlined the importance of the Anthropogenic Heat Flux to the calculation of the urban energy budget and subsequently, the estimation of mesoscale meteorological fields over urban areas. Therefore, spatially disaggregated anthropogenic heat flux data, at local and city scales, are of major importance for mesoscale meteorological models. The main objectives of the present work are to improve the quality of such data used as input for mesoscale meteorological models simulations and to enhance the application potential of GIS and remote sensing in the fields of climatology and meteorology. For this reason, the Urban Energy Budget concept is proposed as the foundation for an accurate determination of the anthropogenic heat discharge as a residual term in the surface energy balance. The methodology is applied to the cities of Athens and Paris using the Landsat ETM+ remote sensing data. The results will help to improve our knowledge on Anthropogenic Heat Flux, while the potential for further improvement of the methodology is also discussed.

Heat flux exchange estimation by using ATSR SST data in TOGA area

Science.gov (United States)

Xue, Yong; Lawrence, Sean P.; Llewellyn-Jones, David T.

1995-12-01

The study of phenomena such as ENSO requires consideration of the dynamics and thermodynamics of the coupled ocean-atmosphere system. The dynamic and thermal properties of the atmosphere and ocean are directly affected by air-sea transfers of fluxes of momentum, heat and moisture. In this paper, we present results of turbulent heat fluxes calculated by using two years (1992 and 1993) monthly average TOGA data and ATSR SST data in TOGA area. A comparison with published results indicates good qualitative agreement. Also, we compared the results of heat flux exchange by using ATSR SST data and by using the TOGA bucket SST data. The ATSR SST data set has been shown to be useful in helping to estimate the large space scale heat flux exchange.

Causes of Potential Urban Heat Island Space Using Heat flux Budget Under Urban Canopy

Science.gov (United States)

Kwon, Y. J.; Lee, D. K.

2017-12-01

, or latent heat, though they are exposed to heat due to a lot sensible heat in the air. Third, in the severe areas at night time, the latent heat was not effective but storage heat flux from the day time was emitted in the air which made the space still warm after sunset. Lastly, the comfort areas at night time have a low SVF rate, and had the large shadow effect during day time.

A review of models and micrometeorological methods used to estimate wetland evapotranspiration

Science.gov (United States)

Drexler, J.Z.; Snyder, R.L.; Spano, D.; Paw, U.K.T.

2004-01-01

Within the past decade or so, the accuracy of evapotranspiration (ET) estimates has improved due to new and increasingly sophisticated methods. Yet despite a plethora of choices concerning methods, estimation of wetland ET remains insufficiently characterized due to the complexity of surface characteristics and the diversity of wetland types. In this review, we present models and micrometeorological methods that have been used to estimate wetland ET and discuss their suitability for particular wetland types. Hydrological, soil monitoring and lysimetric methods to determine ET are not discussed. Our review shows that, due to the variability and complexity of wetlands, there is no single approach that is the best for estimating wetland ET. Furthermore, there is no single foolproof method to obtain an accurate, independent measure of wetland ET. Because all of the methods reviewed, with the exception of eddy covariance and LIDAR, require measurements of net radiation (Rn) and soil heat flux (G), highly accurate measurements of these energy components are key to improving measurements of wetland ET. Many of the major methods used to determine ET can be applied successfully to wetlands of uniform vegetation and adequate fetch, however, certain caveats apply. For example, with accurate Rn and G data and small Bowen ratio (??) values, the Bowen ratio energy balance method can give accurate estimates of wetland ET. However, large errors in latent heat flux density can occur near sunrise and sunset when the Bowen ratio ?? ??? - 1??0. The eddy covariance method provides a direct measurement of latent heat flux density (??E) and sensible heat flux density (II), yet this method requires considerable expertise and expensive instrumentation to implement. A clear advantage of using the eddy covariance method is that ??E can be compared with Rn-G H, thereby allowing for an independent test of accuracy. The surface renewal method is inexpensive to replicate and, therefore, shows

Longitudinal Research with Latent Variables

CERN Document Server

van Montfort, Kees; Satorra, Albert

2010-01-01

This book combines longitudinal research and latent variable research, i.e. it explains how longitudinal studies with objectives formulated in terms of latent variables should be carried out, with an emphasis on detailing how the methods are applied. Because longitudinal research with latent variables currently utilizes different approaches with different histories, different types of research questions, and different computer programs to perform the analysis, the book is divided into nine chapters. Starting from some background information about the specific approach, short history and the ma

Estimate of thermoelastic heat production from superconducting composites in pulsed poloidal coil systems

International Nuclear Information System (INIS)

Ballou, J.K.; Gray, W.H.

1976-01-01

In the design of the cryogenic system and superconducting magnets for the poloidal field system in a tokamak, it is important to have an accurate estimate of the heat produced in superconducting magnets as a result of rapidly changing magnetic fields. A computer code, PLASS (Pulsed Losses in Axisymmetric Superconducting Solenoids), was written to estimate the contributions to the heat production from superconductor hysteresis losses, superconductor coupling losses, stabilizing material eddy current losses, and structural material eddy current losses. Recently, it has been shown that thermoelastic dissipation in superconducting composites can contribute as much to heat production as the other loss mechanisms mentioned above. A modification of PLASS which takes into consideration thermoelastic dissipation in superconducting composites is discussed. A comparison between superconductor thermoelastic dissipation and the other superconductor loss mechanisms is presented in terms of the poloidal coil system of the ORNL Experimental Power Reactor design

Structural observability analysis and EKF based parameter estimation of building heating models

Directory of Open Access Journals (Sweden)

D.W.U. Perera

2016-07-01

Full Text Available Research for enhanced energy-efficient buildings has been given much recognition in the recent years owing to their high energy consumptions. Increasing energy needs can be precisely controlled by practicing advanced controllers for building Heating, Ventilation, and Air-Conditioning (HVAC systems. Advanced controllers require a mathematical building heating model to operate, and these models need to be accurate and computationally efficient. One main concern associated with such models is the accurate estimation of the unknown model parameters. This paper presents the feasibility of implementing a simplified building heating model and the computation of physical parameters using an off-line approach. Structural observability analysis is conducted using graph-theoretic techniques to analyze the observability of the developed system model. Then Extended Kalman Filter (EKF algorithm is utilized for parameter estimates using the real measurements of a single-zone building. The simulation-based results confirm that even with a simple model, the EKF follows the state variables accurately. The predicted parameters vary depending on the inputs and disturbances.

A heat conduction simulator to estimate lung temperature distribution during percutaneous transthoracic cryoablation for lung cancer

International Nuclear Information System (INIS)

Futami, Hikaru; Arai, Tsunenori; Yashiro, Hideki; Nakatsuka, Seishi; Kuribayashi, Sachio; Izumi, Youtaro; Tsukada, Norimasa; Kawamura, Masafumi

2006-01-01

To develop an evaluation method for the curative field when using X-ray CT imaging during percutaneous transthoracic cryoablation for lung cancer, we constructed a finite-element heat conduction simulator to estimate temperature distribution in the lung during cryo-treatment. We calculated temperature distribution using a simple two-dimensional finite element model, although the actual temperature distribution spreads in three dimensions. Temperature time-histories were measured within 10 minutes using experimental ex vivo and in vivo lung cryoablation conditions. We adjusted specific heat and thermal conductivity in the heat conduction calculation and compared them with measured temperature time-histories ex vivo. Adjusted lung specific heat was 3.7 J/ (g·deg C) for unfrozen lung and 1.8 J/ (g·deg C) for frozen lung. Adjusted lung thermal conductivity in our finite element model fitted proportionally to the exponential function of lung density. We considered the heat input by blood flow circulation and metabolic heat when we calculated the temperature time-histories during in vivo cryoablation of the lung. We assumed that the blood flow varies in inverse proportion to the change in blood viscosity up to the maximum blood flow predicted from cardiac output. Metabolic heat was set as heat generation in the calculation. The measured temperature time-histories of in vivo cryoablation were then estimated with an accuracy of ±3 deg C when calculated based on this assumption. Therefore, we successfully constructed a two-dimensional heat conduction simulator that is capable of estimating temperature distribution in the lung at the time of first freezing during cryoablation. (author)

Solution of axisymmetric transient inverse heat conduction problems using parameter estimation and multi block methods

International Nuclear Information System (INIS)

Azimi, A.; Hannani, S.K.; Farhanieh, B.

2005-01-01

In this article, a comparison between two iterative inverse techniques to solve simultaneously two unknown functions of axisymmetric transient inverse heat conduction problems in semi complex geometries is presented. The multi-block structured grid together with blocked-interface nodes is implemented for geometric decomposition of physical domain. Numerical scheme for solution of transient heat conduction equation is the finite element method with frontal technique to solve algebraic system of discrete equations. The inverse heat conduction problem involves simultaneous unknown time varying heat generation and time-space varying boundary condition estimation. Two parameter-estimation techniques are considered, Levenberg-Marquardt scheme and conjugate gradient method with adjoint problem. Numerically computed exact and noisy data are used for the measured transient temperature data needed in the inverse solution. The results of the present study for a configuration including two joined disks with different heights are compared to those of exact heat source and temperature boundary condition, and show good agreement. (author)

Latent segmentation based count models: Analysis of bicycle safety in Montreal and Toronto.

Science.gov (United States)

Yasmin, Shamsunnahar; Eluru, Naveen

2016-10-01

The study contributes to literature on bicycle safety by building on the traditional count regression models to investigate factors affecting bicycle crashes at the Traffic Analysis Zone (TAZ) level. TAZ is a traffic related geographic entity which is most frequently used as spatial unit for macroscopic crash risk analysis. In conventional count models, the impact of exogenous factors is restricted to be the same across the entire region. However, it is possible that the influence of exogenous factors might vary across different TAZs. To accommodate for the potential variation in the impact of exogenous factors we formulate latent segmentation based count models. Specifically, we formulate and estimate latent segmentation based Poisson (LP) and latent segmentation based Negative Binomial (LNB) models to study bicycle crash counts. In our latent segmentation approach, we allow for more than two segments and also consider a large set of variables in segmentation and segment specific models. The formulated models are estimated using bicycle-motor vehicle crash data from the Island of Montreal and City of Toronto for the years 2006 through 2010. The TAZ level variables considered in our analysis include accessibility measures, exposure measures, sociodemographic characteristics, socioeconomic characteristics, road network characteristics and built environment. A policy analysis is also conducted to illustrate the applicability of the proposed model for planning purposes. This macro-level research would assist decision makers, transportation officials and community planners to make informed decisions to proactively improve bicycle safety - a prerequisite to promoting a culture of active transportation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Heat transfer characteristics of liquid-gas Taylor flows incorporating microencapsulated phase change materials

International Nuclear Information System (INIS)

Howard, J A; Walsh, P A

2014-01-01

This paper presents an investigation on the heat transfer characteristics associated with liquid-gas Taylor flows in mini channels incorporating microencapsulated phase change materials (MPCM). Taylor flows have been shown to result in heat transfer enhancements due to the fluid recirculation experienced within liquid slugs which is attributable to the alternating liquid slug and gas bubble flow structure. Microencapsulated phase change materials (MPCM) also offer significant potential with increased thermal capacity due to the latent heat required to cause phase change. The primary aim of this work was to examine the overall heat transfer potential associated with combining these two novel liquid cooling technologies. By investigating the local heat transfer characteristics, the augmentation/degradation over single phase liquid cooling was quantified while examining the effects of dimensionless variables, including Reynolds number, liquid slug length and gas void fraction. An experimental test facility was developed which had a heated test section and allowed MPCM-air Taylor flows to be subjected to a constant heat flux boundary condition. Infrared thermography was used to record high resolution experimental wall temperature measurements and determine local heat transfer coefficients from the thermal entrance point. 30.2% mass particle concentration of the MPCM suspension fluid was examined as it provided the maximum latent heat for absorption. Results demonstrate a significant reduction in experimental wall temperatures associated with MPCM-air Taylor flows when compared with the Graetz solution for conventional single phase coolants. Total enhancement in the thermally developed region is observed to be a combination of the individual contributions due to recirculation within the liquid slugs and also absorption of latent heat. Overall, the study highlights the potential heat transfer enhancements that are attainable within heat exchange devices employing MPCM

Air to air fixed plate enthalpy heat exchanger, performance variation and energy analysis

Energy Technology Data Exchange (ETDEWEB)

Nasif, Mohammad Shakir [Universiti Teknologi Petronas, Bandar Seri Iskandar (Malaysia); Alwaked, Rafat [Prince Mohammad Bin Fahd University, Al Khobar (Saudi Arabia); Behnia, Masud [University of Sydney, Sydney (Australia); Morrison, Graham [The University of New South Wales, Sydney (Australia)

2013-11-15

The thermal performance of a Z shape enthalpy heat exchanger utilising 70 gsm Kraft paper as the heat and moisture transfer surface has been investigated. Effects of different inlet air humidity ratio conditions on the heat exchanger effectiveness and on the energy recovered by the heat exchanger have been the main focus of this investigation. A typical air conditioning cooling coil which incorporates an enthalpy heat exchanger has been modelled for tropical climate. Under test conditions, results have shown that latent effectiveness and the moisture resistance coefficient have strong dependency on the inlet air humidity ratio. Moreover, the latent effectiveness has been found to be strongly dependent on the moisture resistance coefficient rather than the convective mass transfer coefficient. Finally, annual energy analysis for Singapore weather conditions have also shown that energy recovered under variable inlet air conditions is 15% less than that recovered under constant inlet air conditions for the same heat exchanger.

The Latent Factor Structure of Acute Stress Disorder following Bank Robbery

DEFF Research Database (Denmark)

Hansen, M.; Lasgaard, M.; Elklit, A.

2013-01-01

of the latent structure of ASD were specified and estimated. METHOD: The analyses were based on a national study of bank robbery victims (N = 450) using the acute stress disorder scale. RESULTS: The results of the confirmatory factor analyses showed that the DSM-IV model provided the best fit to the data. Thus...

Performance of a new solar air heater with packed-bed latent storage energy for nocturnal use

International Nuclear Information System (INIS)

Bouadila, Salwa; Kooli, Sami; Lazaar, Mariem; Skouri, Safa; Farhat, Abdelhamid

2013-01-01

Highlights: • A new solar air heater collector using a phase change material. • Experimental study of the new solar air heater collector with latent storage. • Energy and exergy analysis of the solar heater with latent storage collector. • Nocturnal use of solar air heater collector. - Abstract: An experimental study was conducted to evaluate the thermal performance of a new solar air heater collector using a packed bed of spherical capsules with a latent heat storage system. Using both first and second law of thermodynamics, the energetic and exegetic daily efficiencies were calculated in Closed/Opened and Opened cycle mode. The solar energy was stored in the packed bed through the diurnal period and extracted at night. The experimentally obtained results are used to analyze the performance of the system, based on temperature distribution in different localization of the collectors. The daily energy efficiency varied between 32% and 45%. While the daily exergy efficiency varied between 13% and 25%

Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations

Science.gov (United States)

Martin, J.; Reichstein, M.

2012-12-01

We upscaled FLUXNET observations of carbon dioxide, water and energy fluxes to the global scale using the machine learning technique, Model Tree Ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5° x 0.5o spatial resolution and a monthly temporal resolution from 1982-2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were weak. Our products are increasingly used to evaluate global land surface models. However, depending on the flux of interest (e.g. gross primary production, terrestrial ecosystem respiration, net ecosystem exchange, evapotranspiration) and the pattern of interest (mean annual map, seasonal cycles, interannual variability, trends) the robustness and uncertainty of these products varies considerably. To avoid pitfalls, this talk also aims at providing an overview of uncertainties associated with these products, and to provide recommendations on the usage for land surface model evaluations. Finally, we present FLUXCOM - an ongoing activity that aims at generating an ensemble of data-driven FLUXNET based products based on diverse approaches.

Estimation of Key Parameters of the Coupled Energy and Water Model by Assimilating Land Surface Data

Science.gov (United States)

Abdolghafoorian, A.; Farhadi, L.

2017-12-01

Accurate estimation of land surface heat and moisture fluxes, as well as root zone soil moisture, is crucial in various hydrological, meteorological, and agricultural applications. Field measurements of these fluxes are costly and cannot be readily scaled to large areas relevant to weather and climate studies. Therefore, there is a need for techniques to make quantitative estimates of heat and moisture fluxes using land surface state observations that are widely available from remote sensing across a range of scale. In this work, we applies the variational data assimilation approach to estimate land surface fluxes and soil moisture profile from the implicit information contained Land Surface Temperature (LST) and Soil Moisture (SM) (hereafter the VDA model). The VDA model is focused on the estimation of three key parameters: 1- neutral bulk heat transfer coefficient (CHN), 2- evaporative fraction from soil and canopy (EF), and 3- saturated hydraulic conductivity (Ksat). CHN and EF regulate the partitioning of available energy between sensible and latent heat fluxes. Ksat is one of the main parameters used in determining infiltration, runoff, groundwater recharge, and in simulating hydrological processes. In this study, a system of coupled parsimonious energy and water model will constrain the estimation of three unknown parameters in the VDA model. The profile of SM (LST) at multiple depths is estimated using moisture diffusion (heat diffusion) equation. In this study, the uncertainties of retrieved unknown parameters and fluxes are estimated from the inverse of Hesian matrix of cost function which is computed using the Lagrangian methodology. Analysis of uncertainty provides valuable information about the accuracy of estimated parameters and their correlation and guide the formulation of a well-posed estimation problem. The results of proposed algorithm are validated with a series of experiments using a synthetic data set generated by the simultaneous heat and

Simultaneous estimation of strength and position of a heat source in a participating medium using DE algorithm

International Nuclear Information System (INIS)

Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P.M.V.

2013-01-01

An inverse heat transfer problem is discussed to estimate simultaneously the unknown position and timewise varying strength of a heat source by utilizing differential evolution approach. A two dimensional enclosure with isothermal and black boundaries containing non-scattering, absorbing and emitting gray medium is considered. Both radiation and conduction heat transfer are included. No prior information is used for the functional form of timewise varying strength of heat source. The finite volume method is used to solve the radiative transfer equation and the energy equation. In this work, instead of measured data, some temperature data required in the solution of the inverse problem are taken from the solution of the direct problem. The effect of measurement errors on the accuracy of estimation is examined by introducing errors in the temperature data of the direct problem. The prediction of source strength and its position by the differential evolution (DE) algorithm is found to be quite reasonable. -- Highlights: •Simultaneous estimation of strength and position of a heat source. •A conducting and radiatively participating medium is considered. •Implementation of differential evolution algorithm for such kind of problems. •Profiles with discontinuities can be estimated accurately. •No limitation in the determination of source strength at the final time

Reconciling estimates of the ratio of heat and salt fluxes at the ice-ocean interface

Science.gov (United States)

Keitzl, T.; Mellado, J. P.; Notz, D.

2016-12-01

The heat exchange between floating ice and the underlying ocean is determined by the interplay of diffusive fluxes directly at the ice-ocean interface and turbulent fluxes away from it. In this study, we examine this interplay through direct numerical simulations of free convection. Our results show that an estimation of the interface flux ratio based on direct measurements of the turbulent fluxes can be difficult because the flux ratio varies with depth. As an alternative, we present a consistent evaluation of the flux ratio based on the total heat and salt fluxes across the boundary layer. This approach allows us to reconcile previous estimates of the ice-ocean interface conditions. We find that the ratio of heat and salt fluxes directly at the interface is 83-100 rather than 33 as determined by previous turbulence measurements in the outer layer. This can cause errors in the estimated ice-ablation rate from field measurements of up to 40% if they are based on the three-equation formulation.

Heat receivers for solar dynamic space power systems

Science.gov (United States)

Perez-Davis, Marla Esther

A review of state-of-the-art technology is presented and discussed for phase change materials. Some of the advanced solar dynamic designs developed as part of the Advanced Heat Receiver Conceptual Design Study performed for LeRC are discussed. The heat receivers are analyzed and several recommendations are proposed, including two new concepts. The first concept evaluated the effect of tube geometries inside the heat receiver. It was found that a triangular configuration would provide better heat transfer to the working fluid, although not necessarily with a reduction in receiver size. A sensible heat receiver considered in this study uses vapor grown graphite fiber-carbon (VGCF/C) composite as the thermal storage media and was designed for a 7 kW Brayton engine. The proposed heat receiver stores the required energy to power the system during eclipse in the VGCF/C composite. The heat receiver analysis was conducted through the Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA) software package. The proposed heat receiver compares well with other latent and advanced sensible heat receivers while avoiding the problems associated with latent heat storage salts and liquid metal heat pipes. The weight and size of the system can be optimized by changes in geometry and technology advances for this new material. In addition to the new concepts, the effect of atomic oxygen on several materials is reviewed. A test was conducted for atomic oxygen attack on boron nitride, which experienced a negligible mass loss when exposed to an atomic oxygen fluence of 5 x 10 exp 21 atoms/sq cm. This material could be used to substitute the graphite aperture plate of the heat receiver.

A new approach to the joined estimation of the heat generated by a semicontiunuous emulsion polymerization Qr and the overall heat exchange parameter UA

Directory of Open Access Journals (Sweden)

Freire F. B.

2004-01-01

Full Text Available This work is concerned with the coupled estimation of the heat generated by the reaction (Qr and the overall heat transfer parameter (UA during the terpolymerization of styrene, butyl acrylate and methyl methacrylate from temperature measurements and the reactor heat balance. By making specific assumptions about the dynamics of the evolution of UA and Q R, we propose a cascade of observers to successively estimate these two parameters without the need for additional measurements of on-line samples. One further aspect of our approach is that only the energy balance around the reactor was employed. It means that the flow rate of the cooling jacket fluid was not required.

Process for the transport of heat energy released by a nuclear reactor

International Nuclear Information System (INIS)

Nuernberg, H.W.; Wolff, G.

1978-01-01

The heat produced in a nuclear reactor is converted into latent chemical binding energy. The heat can be released again below 400 0 C by recombination after transport by decomposition of ethane or propane into ethylene or propylene and hydrogen. (TK) [de

Heat pulse probe measurements of soil water evaporation in a corn field

Science.gov (United States)

Latent heat fluxes from cropped fields consist of soil water evaporation and plant transpiration. It is difficult to accurately separate evapotranspiration into evaporation and transpiration. Heat pulse probes have been used to measure bare field subsurface soil water evaporation, however, the appl...

A study on pre-heat conditions in equivalent-dose estimation of holocene loess using single-aliquot regenerative-dose (SAR) protocol

International Nuclear Information System (INIS)

Jia Yaofeng; Huang Chunchang; Pang Jiangli; Lu Xinwei; Zhang Xu

2007-01-01

Through various arrangements of pre-heat and cut-heat temperatures in the equivalent-dose estimation of Holocene loess using a Double-SAR dating protocol, the paper estimated the equivalent-doses from several loess samples by application of IRSL and Post-IR OSL signals, respectively. The measured results present that the equivalent-dose depends on the heat temperature, especially depends on the cut-heat temperature, showing the equivalent-dose increases with the cut-heat temperature; a plateau of equivalent-dose appears at the 200-300 degree C preheat temperatures and the 200-240 degree C cut-heat temperatures, furthermore, the equivalent-doses estimated by IRSL and Post-IR OSL signals respectively are close to each other, which resulted from the similar sensitivity change directions of optical stimulated signals and their smaller change ranges in the measurement cycles using the various temperatures of pre-heat and cut-heat. This suggests that the 200-300 degree C pre-heat temperatures and the 200-240 degree C cut-heat temperatures are fit for dating young Holocene loess samples. (authors)

Thermal performance analysis of heat exchanger for closed wet cooling tower using heat and mass transfer analogy

International Nuclear Information System (INIS)

Yoo, Seong Yeon; Han, Kyu Hyun; Kim, Jin Hyuck

2010-01-01

In closed wet cooling towers, the heat transfer between the air and external tube surfaces can be composed of the sensible heat transfer and the latent heat transfer. The heat transfer coefficient can be obtained from the equation for external heat transfer of tube banks. According to experimental data, the mass transfer coefficient was affected by the air velocity and spray water flow rate. This study provides the correlation equation for mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental data. The results from this correlation equation showed fairly good agreement with experimental data. The cooling capacity and thermal efficiency of the closed wet cooling tower were calculated from the correlation equation to analyze the performance of heat exchanger for the tower

Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean

Science.gov (United States)

Mazloff, M. R.; Cornuelle, B. D.; Gille, S. T.; Verdy, A.

2018-02-01

The spatial correlation scales of oceanic dissolved inorganic carbon, heat content, and carbon and heat exchanges with the atmosphere are estimated from a realistic numerical simulation of the Southern Ocean. Biases in the model are assessed by comparing the simulated sea surface height and temperature scales to those derived from optimally interpolated satellite measurements. While these products do not resolve all ocean scales, they are representative of the climate scale variability we aim to estimate. Results show that constraining the carbon and heat inventory between 35°S and 70°S on time-scales longer than 90 days requires approximately 100 optimally spaced measurement platforms: approximately one platform every 20° longitude by 6° latitude. Carbon flux has slightly longer zonal scales, and requires a coverage of approximately 30° by 6°. Heat flux has much longer scales, and thus a platform distribution of approximately 90° by 10° would be sufficient. Fluxes, however, have significant subseasonal variability. For all fields, and especially fluxes, sustained measurements in time are required to prevent aliasing of the eddy signals into the longer climate scale signals. Our results imply a minimum of 100 biogeochemical-Argo floats are required to monitor the Southern Ocean carbon and heat content and air-sea exchanges on time-scales longer than 90 days. However, an estimate of formal mapping error using the current Argo array implies that in practice even an array of 600 floats (a nominal float density of about 1 every 7° longitude by 3° latitude) will result in nonnegligible uncertainty in estimating climate signals.

Estimation of the Heat Flow Variation in the Chad Basin Nigeria ...

African Journals Online (AJOL)

Wireline logs from 14 oil wells from the Nigerian sector of the Chad Basin were analyzed and interpreted to estimate the heat flow trend in the basin. Geothermal gradients were computed from corrected bottom hole temperatures while the bulk effective thermal conductivity for the different stratigraphic units encountered in ...

Do gamblers eat more salt? Testing a latent trait model of covariance in consumption.

Science.gov (United States)

Goodwin, Belinda C; Browne, Matthew; Rockloff, Matthew; Donaldson, Phillip

2015-09-01

A diverse class of stimuli, including certain foods, substances, media, and economic behaviours, may be described as 'reward-oriented' in that they provide immediate reinforcement with little initial investment. Neurophysiological and personality concepts, including dopaminergic dysfunction, reward sensitivity and rash impulsivity, each predict the existence of a latent behavioural trait that leads to increased consumption of all stimuli in this class. Whilst bivariate relationships (co-morbidities) are often reported in the literature, to our knowledge, a multivariate investigation of this possible trait has not been done. We surveyed 1,194 participants (550 male) on their typical weekly consumption of 11 types of reward-oriented stimuli, including fast food, salt, caffeine, television, gambling products, and illicit drugs. Confirmatory factor analysis was used to compare models in a 3×3 structure, based on the definition of a single latent factor (none, fixed loadings, or estimated loadings), and assumed residual covariance structure (none, a-priori / literature based, or post-hoc / data-driven). The inclusion of a single latent behavioural 'consumption' factor significantly improved model fit in all cases. Also confirming theoretical predictions, estimated factor loadings on reward-oriented indicators were uniformly positive, regardless of assumptions regarding residual covariances. Additionally, the latent trait was found to be negatively correlated with the non-reward-oriented indicators of fruit and vegetable consumption. The findings support the notion of a single behavioural trait leading to increased consumption of reward-oriented stimuli across multiple modalities. We discuss implications regarding the concentration of negative lifestyle-related health behaviours.

Simultaneously estimation for surface heat fluxes of steel slab in a reheating furnace based on DMC predictive control

International Nuclear Information System (INIS)

Li, Yanhao; Wang, Guangjun; Chen, Hong

2015-01-01

The predictive control theory is utilized for the research of a simultaneous estimation of heat fluxes through the upper, side and lower surface of a steel slab in a walking beam type rolling steel reheating furnace. An inverse algorithm based on dynamic matrix control (DMC) is established. That is, each surface heat flux of a slab is simultaneously estimated through rolling optimization on the basis of temperature measurements in selected points of its interior by utilizing step response function as predictive model of a slab's temperature. The reliability of the DMC results is enhanced without prior assuming specific functions of heat fluxes over a period of future time. The inverse algorithm proposed a respective regularization to effectively improve the stability of the estimated results by considering obvious strength differences between the upper as well as lower and side surface heat fluxes of the slab. - Highlights: • The predictive control theory is adopted. • An inversion scheme based on DMC is established. • Upper, side and lower surface heat fluxes of slab are estimated based DMC. • A respective regularization is proposed to improve the stability of results

Estimates of error introduced when one-dimensional inverse heat transfer techniques are applied to multi-dimensional problems

International Nuclear Information System (INIS)

Lopez, C.; Koski, J.A.; Razani, A.

2000-01-01

A study of the errors introduced when one-dimensional inverse heat conduction techniques are applied to problems involving two-dimensional heat transfer effects was performed. The geometry used for the study was a cylinder with similar dimensions as a typical container used for the transportation of radioactive materials. The finite element analysis code MSC P/Thermal was used to generate synthetic test data that was then used as input for an inverse heat conduction code. Four different problems were considered including one with uniform flux around the outer surface of the cylinder and three with non-uniform flux applied over 360 deg C, 180 deg C, and 90 deg C sections of the outer surface of the cylinder. The Sandia One-Dimensional Direct and Inverse Thermal (SODDIT) code was used to estimate the surface heat flux of all four cases. The error analysis was performed by comparing the results from SODDIT and the heat flux calculated based on the temperature results obtained from P/Thermal. Results showed an increase in error of the surface heat flux estimates as the applied heat became more localized. For the uniform case, SODDIT provided heat flux estimates with a maximum error of 0.5% whereas for the non-uniform cases, the maximum errors were found to be about 3%, 7%, and 18% for the 360 deg C, 180 deg C, and 90 deg C cases, respectively

Revisiting Gill's Circulation. Dynamic Response to Diabatic Heating of Different Horizontal Extents

Science.gov (United States)

Reboredo, B.; Bellon, G.

2017-12-01

The horizontal extent of diabatic heating associated with the MJO is thought to be crucial to its development, and the inability of GCMs to simulate the spatial, horizontal organization of clouds is considered a leading hypothesis to explain their limited capacity to simulate MJO events. This prevents the MJO large-circulation response from developing and feeding back on the development of clouds. We apply mid-tropospheric heating of different size in simple linear and non-linear models of the tropical atmosphere following Gill's seminal work on heat-induced tropical circulations. Results show that there is a scale for which the characteristic circulation {Γ c} for the vertical advection of moisture to produce the latent heat mean {Q} gives a rough estimate of the real world MJO scale. Overturning circulation flow rates above {Γ c} account for a circulation that transports more moisture than necessary to be maintained, and below {Γ c}, circulation would not transport enough moisture to maintain circulation. This dynamic scale might constrain the size of the spatially-organised convection necessary to the development of an MJO event. However, other effects are expected to modulate this scale, such as vertical advection of moisture anomalies, horizontal advection, evaporation, radiative heating, and sensible heat fluxes.

Adaptive neuro-fuzzy based inferential sensor model for estimating the average air temperature in space heating systems

Energy Technology Data Exchange (ETDEWEB)

Jassar, S.; Zhao, L. [Department of Electrical and Computer Engineering, Ryerson University, 350 Victoria Street, Toronto, ON (Canada); Liao, Z. [Department of Architectural Science, Ryerson University (Canada)

2009-08-15

The heating systems are conventionally controlled by open-loop control systems because of the absence of practical methods for estimating average air temperature in the built environment. An inferential sensor model, based on adaptive neuro-fuzzy inference system modeling, for estimating the average air temperature in multi-zone space heating systems is developed. This modeling technique has the advantage of expert knowledge of fuzzy inference systems (FISs) and learning capability of artificial neural networks (ANNs). A hybrid learning algorithm, which combines the least-square method and the back-propagation algorithm, is used to identify the parameters of the network. This paper describes an adaptive network based inferential sensor that can be used to design closed-loop control for space heating systems. The research aims to improve the overall performance of heating systems, in terms of energy efficiency and thermal comfort. The average air temperature results estimated by using the developed model are strongly in agreement with the experimental results. (author)

On the exchange of sensible and latent heat between the atmosphere and melting snow

Science.gov (United States)

Stoy, Paul C.; Peitzsch, Erich H.; Wood, David J. A.; Rottinghaus, Daniel; Wohlfahrtd, Georg; Goulden, Michael; Ward, Helen

2018-01-01

The snow energy balance is difficult to measure during the snowmelt period, yet critical for predictions of water yield in regions characterized by snow cover. Robust simplifications of the snowmelt energy balance can aid our understanding of water resources in a changing climate. Research to date has demonstrated that the net turbulent flux (FT) between a melting snowpack and the atmosphere is negligible if the sum of atmospheric vapor pressure (ea) and temperature (Ta) equals a constant, but it is unclear how frequently this situation holds across different sites. Here, we quantified the contribution of FT to the snowpack energy balance during 59 snowmelt periods across 11 sites in the FLUXNET2015 database with a detailed analysis of snowmelt in subarctic tundra near Abisko, Sweden. At the Abisko site we investigated the frequency of occurrences during which sensible heat flux (H) and latent heat flux (λE) are of (approximately) equal but opposite sign, and if the sum of these terms, FT, is therefore negligible during the snowmelt period. H approximately equaled -λE for less than 50% of the melt period and FT was infrequently a trivial term in the snowmelt energy balance at Abisko. The reason is that the relationship between observed ea and Ta is roughly orthogonal to the “line of equality” at which H equals -λE as warmer Ta during the melt period usually resulted in greater ea. This relationship holds both within melt periods at individual sites and across different sites in the FLUXNET2015 database, where FTcomprised less than 20% of the energy available to melt snow, Qm, in 44% of the snowmelt periods studied here. FT/Qm was significantly related to the mean ea during the melt period, but not mean Ta, and FT tended to be near 0 W m−2 when ea averaged ca. 0.5 kPa. FT may become an increasingly important term in the snowmelt energy balance across many global regions as warmer temperatures are projected to cause snow

Estimation of sediment friction coefficient from heating upon APC penetration during the IODP NanTroSEIZE

Science.gov (United States)

Kinoshita, M.; Kawamura, K.; Lin, W.

2015-12-01

During the Nankai Trough Seismogenic Zone Experiments (NanTroSEIZE) of the Integrated Ocean Drilling Program (IODP), the advanced piston corer temperature (APC-T) tool was used to determine in situ formation temperatures while piston coring down to ~200 m below sea floor. When the corer is fired into the formation, temperature around the shoe abruptly increases due to the frictional heating. The temperature rise due to the frictional heat at the time of penetration is 10 K or larger. We found that the frictional temperature rise (=maximum temperature) increases with increasing depth, and that its intersection at the seafloor seems non-zero. Frictional heat energy is proportional to the maximum temperature rise, which is confirmed by a FEM numerical simulation of 2D cylindrical system. Here we use the result of numerical simulation to convert the observed temperature rise into the frictional heat energy. The frictional heat energy is represented as the product of the shooting length D and the shear stress (τ) between the pipe and the sediment. Assuming a coulomb slip regime, the shear stress is shows as: τ= τ0 + μ*(Sv-Pp), where τ0 is the cohesive stress, μ the dynamic frictional coefficient between the pipe and the sediment, Sv the normal stress at the pipe, and Pp the pore pressure. This can explain the non-zero intersection as well as depth-dependent increase for the frictional heating observed in the APC-T data. Assuming a hydrostatic state and by using the downhole bulk density data, we estimated the friction coefficient for each APC-T measurement. For comparison, we used the vane-shear strength measured on core samples to estimate the friction coefficients. The frictional coefficients μ were estimated as ranging 0.01 - 0.06, anomalously lower than expected for shallow marine sediments. They were lower than those estimated from vane-shear data, which range 0.05 to 0.2. Still, both estimates exhibit a significant increase in the friction coefficient at

Separate sensible and latent cooling system: A preliminary analysis of a novel approach

Energy Technology Data Exchange (ETDEWEB)

Nawaz, Kashif [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-10-01

Separate sensible and latent cooling systems offer significant increases in the overall performance of cooling/dehumidification systems compared with conventional vapor-compression air-conditioning systems. Key to the energy efficiency of such systems is the performance of the heat and mass exchangers that provide sensible cooling and dehumidification. A novel design is proposed for dehumidification applications, deploying metal foam as a substrate coated with solid desiccants. The current report provides some preliminary information regarding the development of the technology and discusses factors such as manufacturing of desiccants, characterization of desiccants, and development of the metal foam heat exchanger. All three aspects provide the necessary infrastructure for further development and validation of the proposed concept.

The study on pre-heat conditions in the equivalent-dose estimation of holocene loess using the single-aliquot regenerative-dose (SAR) protocol

International Nuclear Information System (INIS)

Jia Yaofeng; Huang Chunchang; Pang Jiangli; Lu Xinwei; Zhang Xu

2008-01-01

The thermal treatment in the equivalent-dose estimation often is carried in the OSL dating, and pre-heat is a main thermal treatment. Due to which will originate the problems of thermal transfer and thermal activation, the thermal treatment and the setup of their conditions are key problems influencing the accuracy of OSL dating. The paper combined the temperature of pre-heat and cut-heat used in the routine measurement of IRSL and Post-IR OSL, and then estimated the equivalent-dose of several loess samples. The estimated result presents that the equivalent-dose depends on the heat temperature, especially depends on the cut-heat temperature, which is to say that the equivalent-dose increases with the cut-heat temperature; a plateau of equivalent-dose appears when using the 200-240 degree C cut-heat in the range of 200-300 degree C pre-heat, and the equivalent-doses estimated by IRSL and Post-IR OSL respectively are close to each other, which resulted from the similar sensitivity change direction of optical stimulated signals and its smaller change range in the measurement cycles using the combined temperature of pre- heat and cut-heat, and the incomplete calibration of sensitivity change of optical stimulated signals in the whole measurement cycles caused the variation of estimated equivalent-dose corresponding to the cut-heat temperature. (authors)

Monitoring energy efficiency of condensing boilers via hybrid first-principle modelling and estimation

NARCIS (Netherlands)

Satyavada, Harish; Baldi, S.

2018-01-01

The operating principle of condensing boilers is based on exploiting heat from flue gases to pre-heat cold water at the inlet of the boiler: by condensing into liquid form, flue gases recover their latent heat of vaporization, leading to 10–12% increased efficiency with respect to traditional

Unravelling the influence of smoking initiation and cessation on premature mortality using a common latent factor model

OpenAIRE

Silvia Balia; Andrew M. Jones

2007-01-01

Duration models for lifespan and smoking, that focus on the socio-economic gradient in smoking durations and length of life, are estimated controlling for individual-specific unobservable heterogeneity by means of a latent factor model. The latent factor influences the risk of starting and quitting smoking as well as the hazard of mortality. Frailty could in°uence smoking behaviour through two mechanisms: the effect of life expectancy on initiation of smok- ing and the impact of adverse healt...

Satellite air temperature estimation for monitoring the canopy layer heat island of Milan

DEFF Research Database (Denmark)

Pichierri, Manuele; Bonafoni, Stefania; Biondi, Riccardo

2012-01-01

across the city center from June to September confirming that, in Milan, urban heating is not an occasional phenomenon. Furthermore, this study shows the utility of space missions to monitor the metropolis heat islands if they are able to provide nighttime observations when CLHI peaks are generally......In this work, satellite maps of the urban heat island of Milan are produced using satellite-based infrared sensor data. For this aim, we developed suitable algorithms employing satellite brightness temperatures for the direct air temperature estimation 2 m above the surface (canopy layer), showing...... 2007 and 2010 were processed. Analysis of the canopy layer heat island (CLHI) maps during summer months reveals an average heat island effect of 3–4K during nighttime (with some peaks around 5K) and a weak CLHI intensity during daytime. In addition, the satellite maps reveal a well defined island shape...

Estimation and harvesting of human heat power for wearable electronic devices

International Nuclear Information System (INIS)

Dziurdzia, P; Brzozowski, I; Bratek, P; Gelmuda, W; Kos, A

2016-01-01

The paper deals with the issue of self-powered wearable electronic devices that are capable of harvesting free available energy dissipated by the user in the form of human heat. The free energy source is intended to be used as a secondary power source supporting primary battery in a sensor bracelet. The main scope of the article is a presentation of the concept for a measuring setup used to quantitative estimation of heat power sources in different locations over the human body area. The crucial role in the measurements of the human heat plays a thermoelectric module working in the open circuit mode. The results obtained during practical tests are confronted with the requirements of the dedicated thermoelectric generator. A prototype design of a human warmth energy harvester with an ultra-low power DC-DC converter based on the LTC3108 circuit is analysed

Heat pipe solar receiver with thermal energy storage

Science.gov (United States)

Zimmerman, W. F.

1981-01-01

An HPSR Stirling engine generator system featuring latent heat thermal energy storge, excellent thermal stability and self regulating, effective thermal transport at low system delta T is described. The system was supported by component technology testing of heat pipes and of thermal storage and energy transport models which define the expected performance of the system. Preliminary and detailed design efforts were completed and manufacturing of HPSR components has begun.

A New Entropy Formula and Gradient Estimates for the Linear Heat Equation on Static Manifold

Directory of Open Access Journals (Sweden)

Abimbola Abolarinwa

2014-08-01

Full Text Available In this paper we prove a new monotonicity formula for the heat equation via a generalized family of entropy functionals. This family of entropy formulas generalizes both Perelman’s entropy for evolving metric and Ni’s entropy on static manifold. We show that this entropy satisfies a pointwise differential inequality for heat kernel. The consequences of which are various gradient and Harnack estimates for all positive solutions to the heat equation on compact manifold.

Modeling ground thermal regime of an ancient buried ice body in Beacon Valley, Antarctica using a 1-D heat equation with latent heat effect

Science.gov (United States)

Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.

2013-12-01

An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal

Biomarkers of latent TB infection

DEFF Research Database (Denmark)

Ruhwald, Morten; Ravn, Pernille

2009-01-01

For the last 100 years, the tuberculin skin test (TST) has been the only diagnostic tool available for latent TB infection (LTBI) and no biomarker per se is available to diagnose the presence of LTBI. With the introduction of M. tuberculosis-specific IFN-gamma release assays (IGRAs), a new area...... of in vitro immunodiagnostic tests for LTBI based on biomarker readout has become a reality. In this review, we discuss existing evidence on the clinical usefulness of IGRAs and the indefinite number of potential new biomarkers that can be used to improve diagnosis of latent TB infection. We also present...... early data suggesting that the monocyte-derived chemokine inducible protein-10 may be useful as a novel biomarker for the immunodiagnosis of latent TB infection....

Revisiting the latent heat nudging scheme for the rainfall assimilation of a simulated convective storm

Science.gov (United States)

Leuenberger, D.; Rossa, A.

2007-12-01

Next-generation, operational, high-resolution numerical weather prediction models require economical assimilation schemes for radar data. In the present study we evaluate and characterise the latent heat nudging (LHN) rainfall assimilation scheme within a meso-γ scale NWP model in the framework of identical twin simulations of an idealised supercell storm. Consideration is given to the model’s dynamical response to the forcing as well as to the sensitivity of the LHN scheme to uncertainty in the observations and the environment. The results indicate that the LHN scheme is well able to capture the dynamical structure and the right rainfall amount of the storm in a perfect environment. This holds true even in degraded environments but a number of important issues arise. In particular, changes in the low-level humidity field are found to affect mainly the precipitation amplitude during the assimilation with a fast adaptation of the storm to the system dynamics determined by the environment during the free forecast. A constant bias in the environmental wind field, on the other hand, has the potential to render a successful assimilation with the LHN scheme difficult, as the velocity of the forcing is not consistent with the system propagation speed determined by the wind. If the rainfall forcing moves too fast, the system propagation is supported and the assimilated storm and forecasts initialised therefrom develop properly. A too slow forcing, on the other hand, can decelerate the system and eventually disturb the system dynamics by decoupling the low-level moisture inflow from the main updrafts during the assimilation. This distortion is sustained in the free forecast. It has further been found that a sufficient temporal resolution of the rainfall input is crucial for the successful assimilation of a fast moving, coherent convective storm and that the LHN scheme, when applied to a convective storm, appears to necessitate a careful tuning.

A Bayesian analysis of sensible heat flux estimation: Quantifying uncertainty in meteorological forcing to improve model prediction

KAUST Repository

Ershadi, Ali

2013-05-01

The influence of uncertainty in land surface temperature, air temperature, and wind speed on the estimation of sensible heat flux is analyzed using a Bayesian inference technique applied to the Surface Energy Balance System (SEBS) model. The Bayesian approach allows for an explicit quantification of the uncertainties in input variables: a source of error generally ignored in surface heat flux estimation. An application using field measurements from the Soil Moisture Experiment 2002 is presented. The spatial variability of selected input meteorological variables in a multitower site is used to formulate the prior estimates for the sampling uncertainties, and the likelihood function is formulated assuming Gaussian errors in the SEBS model. Land surface temperature, air temperature, and wind speed were estimated by sampling their posterior distribution using a Markov chain Monte Carlo algorithm. Results verify that Bayesian-inferred air temperature and wind speed were generally consistent with those observed at the towers, suggesting that local observations of these variables were spatially representative. Uncertainties in the land surface temperature appear to have the strongest effect on the estimated sensible heat flux, with Bayesian-inferred values differing by up to ±5°C from the observed data. These differences suggest that the footprint of the in situ measured land surface temperature is not representative of the larger-scale variability. As such, these measurements should be used with caution in the calculation of surface heat fluxes and highlight the importance of capturing the spatial variability in the land surface temperature: particularly, for remote sensing retrieval algorithms that use this variable for flux estimation.