Experimental Research of a Water-Source Heat Pump Water Heater System

Directory of Open Access Journals (Sweden)

Zhongchao Zhao

2018-05-01

Full Text Available The heat pump water heater (HPWH, as a portion of the eco-friendly technologies using renewable energy, has been applied for years in developed countries. Air-source heat pump water heaters and solar-assisted heat pump water heaters have been widely applied and have become more and more popular because of their comparatively higher energy efficiency and environmental protection. Besides use of the above resources, the heat pump water heater system can also adequately utilize an available water source. In order to study the thermal performance of the water-source heat pump water heater (WSHPWH system, an experimental prototype using the cyclic heating mode was established. The heating performance of the water-source heat pump water heater system, which was affected by the difference between evaporator water fluxes, was investigated. The water temperature unfavorably exceeded 55 °C when the experimental prototype was used for heating; otherwise, the compressor discharge pressure was close to the maximum discharge temperature, which resulted in system instability. The evaporator water flux allowed this system to function satisfactorily. It is necessary to reduce the exergy loss of the condenser to improve the energy utilization of the system.

Heating and Domestic Hot Water Systems in Buildings Supplied by Low-Temperature District Heating

DEFF Research Database (Denmark)

Brand, Marek

solutions simply redirect the bypassed water back to the DH network without additional cooling, but bypassed water can instead be redirected to floor heating in the bathroom to be further cooled and thus reduce heat loss from the DH network while improving comfort for occupants and still ensure fast DHW...... increased risk of Legionella if the DH substation and DHW system are designed for the low-temperature supply conditions. To ensure the fast provision of DHW during non-heating periods, the supply service pipe should be kept warm, preferably with the bypass solution redirecting the bypass flow to bathroom...... temperature. To accord with the literature, the modelling of internal heat gains reflected the improved efficiency of equipment by reduction of value from 5W/m2 to 4.2W/m2, also modelled as intermittent heat gains based on a realistic week schedule. Furthermore, the indoor set-point temperature was increased...

Performance analysis of a low-temperature waste heat-driven adsorption desalination prototype

KAUST Repository

Thu, Kyaw

2013-10-01

This paper discusses the performance analysis of an advanced adsorption desalination (AD) cycle with an internal heat recovery between the condenser and the evaporator. The AD cycle employs the adsorption-desorption principles to convert sea or brackish water into high-grade potable water with total dissolved solids (TDS) less than 10 ppm (mg/L) utilizing low-temperature heat source. The salient features of the AD cycle are the utilization of low temperature waste heat (typically 55 C to 85 C) with the employment of an environment-friendly silica gel/water pair and the low maintenance as it has no major moving parts other than the pumps and valves. For improved performance of the AD pilot plant, the internal heat recovery scheme between the condenser and evaporator has been implemented with a run-about water circuit between them. The efficacy of the scheme is analyzed in terms of key performance indicators such as the specific daily water production (SDWP) and the performance ratio (PR). Extensive experiments were performed for assorted heat source temperatures ranging from 70 C to 50 C. From the experiments, the SDWP of the AD cycle with the proposed heat recovery scheme is found to be 15 m3 of water per ton of silica gel that is almost twice that of the yield obtained by a conventional AD cycle for the same operation conditions. Another important finding of AD desalination plant is that the advanced AD cycle could still be operational with an inlet heat source temperature of 50 C and yet achieving a SDWP of 4.3 m3 - a feat that never seen by any heat-driven cycles. © 2013 Elsevier Ltd. All rights reserved.

Design and modelling of a novel compact power cycle for low temperature heat sources

DEFF Research Database (Denmark)

Wronski, Jorrit; Skovrup, Morten Juel; Elmegaard, Brian

2012-01-01

Power cycles for the efficient use of low temperature heat sources experience increasing attention. This paper describes an alternative cycle design that offers potential advantages in terms of heat source exploitation. A concept for a reciprocating expander is presented that performs both, work ...

Industrial waste heat utilization for low temperature district heating

International Nuclear Information System (INIS)

Fang, Hao; Xia, Jianjun; Zhu, Kan; Su, Yingbo; Jiang, Yi

2013-01-01

Large quantities of low grade waste heat are discharged into the environment, mostly via water evaporation, during industrial processes. Putting this industrial waste heat to productive use can reduce fossil fuel usage as well as CO 2 emissions and water dissipation. The purpose of this paper is to propose a holistic approach to the integrated and efficient utilization of low-grade industrial waste heat. Recovering industrial waste heat for use in district heating (DH) can increase the efficiency of the industrial sector and the DH system, in a cost-efficient way defined by the index of investment vs. carbon reduction (ICR). Furthermore, low temperature DH network greatly benefits the recovery rate of industrial waste heat. Based on data analysis and in-situ investigations, this paper discusses the potential for the implementation of such an approach in northern China, where conventional heat sources for DH are insufficient. The universal design approach to industrial-waste-heat based DH is proposed. Through a demonstration project, this approach is introduced in detail. This study finds three advantages to this approach: (1) improvement of the thermal energy efficiency of industrial factories; (2) more cost-efficient than the traditional heating mode; and (3) CO 2 and pollutant emission reduction as well as water conservation. -- Highlights: •We review situation of industrial waste heat recovery with a global perspective. •We present a way to analyze the potential to utilize industrial waste heat for DH. •Northern China has huge potential for using low-grade industrial waste heat for DH. •A demonstration project is introduced using the universal approach we propose. •It proves huge benefits for factories, heat-supply companies and the society

Performance of ammonia–water based cycles for power generation from low enthalpy heat sources

International Nuclear Information System (INIS)

Mergner, Hanna; Weimer, Thomas

2015-01-01

Cost efficient power generation from low temperature heat sources requires an optimal usage of the available heat. In addition to the ORC (Organic Rankine Cycles), cycles with ammonia and water as working fluid show promising results regarding efficiency. Due to their non-isothermal phase change, mixtures can adapt well to a liquid heat source temperature profile and reduce the exergetic losses. In this analysis thermodynamic calculations on the layouts of two existing ammonia–water cycles are compared: a geothermal power plant based on a Siemens’ patent and a modified lab plant based on a patent invented by Kalina (KCS-34). The difference between the two cycles is the position of the internal heat recovery. Cycle simulations were carried out at defined boundary conditions in order to identify optimal operation parameters. For the selected heat source of 393.15 K (hot water) the ammonia mass fraction between 80% and 90% results in the best performance in both configurations. In general, the layout of Siemens achieves a slightly better efficiency compared to the KCS-34. Compared to an ORC using R245fa as working fluid, the exergetic efficiency can be increased by the ammonia/water based cycles by approximately 25%. - Highlights: • Two NH 3 /H 2 O based cycles based on existing plants are analyzed and compared. • A simple KCS-34 focuses on a high enthalpy difference at the turbine. • The Kalina cycle of a Siemens patent KC SG1 runs on a high vapor mass flow. • The layout of the KC SG1 shows slightly better results compared to the KCS-34. • NH 3 /H 2 O cycles show an efficiency increase compared to a regular ORC with R245fa

Measured Performance of a Low Temperature Air Source Heat Pump

Energy Technology Data Exchange (ETDEWEB)

R.K. Johnson

2013-09-01

A 4-ton Low Temperature Heat Pump (LTHP) manufactured by Hallowell International was installed in a residence near New Haven, Connecticut and monitored over two winters of operation. After attending to some significant service issues, the heat pump operated as designed. This report should be considered a review of the dual compressor “boosted heat pump” technology. The Low Temperature Heat Pump system operates with four increasing levels of capacity (heat output) as the outdoor temperature drops.

Decentralized substations for low-temperature district heating with no Legionella risk, and low return temperatures

International Nuclear Information System (INIS)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

To improve energy efficiency and give more access to renewable energy sources, low-temperature district heating (LTDH) is a promising concept to be realized in the future. However, concern about Legionella proliferation restricts applying low-temperature district heating in conventional systems with domestic hot water (DHW) circulation. In this study, a system with decentralized substations was analysed as a solution to this problem. Furthermore, a modification for the decentralized substation system were proposed in order to reduce the average return temperature. Models of conventional system with medium-temperature district heating, decentralized substation system with LTDH, and innovative decentralized substation system with LTDH were built based on the information of a case building. The annual distribution heat loss and the operating costs of the three scenarios were calculated and compared. From the results, realizing LTDH by the decentralized substation unit, 30% of the annual distribution heat loss inside the building can be saved compared to a conventional system with medium-temperature district heating. Replacing the bypass pipe with an in-line supply pipe and a heat pump, the innovative decentralized substation system can reduce distribution heat loss by 39% compared to the conventional system and by 12% compared to the normal decentralized substation system with bypass. - Highlights: • The system of decentralized substations can realize low-temperature district heating without running the risk of Legionella. • Decentralized substations help reduce the distribution heat loss inside the building compared to conventional system. • A new concept that can reduce the return temperature for district heating is proposed and analysed.

Heat pump using dual heat sources of air and water. Performance with heat sources arranged in parallel; Mizu kuki ryonetsugen heat pump no kenkyu. Netsugen heiretsu unten ni okeru seino

Energy Technology Data Exchange (ETDEWEB)

Ito, S; Miura, N; Sato, S [Kanagawa Institute of Technology, Kanagawa (Japan); Uchikawa, Y; Hamada, K [Kubota Corp., Osaka (Japan)

1996-10-27

A heat pump system using water and air as heat sources was built and evaluated for its performance. In this system, evaporators may be operated singly or as connected in parallel or series, and, for each case, the quantity of heat acquired may be measured and system performance may be quantitatively evaluated. The findings follow. When the two heat sources are equal in temperature in the single-evaporator operation, the evaporation temperature is about 7{degree}C higher on the water side than on the air side, and the performance coefficient is about 0.7 higher. When the air heat source temperature is 25{degree}C in the parallel operation, like quantities of heat are obtained from both heat sources, and collection of heat from the water increases with a decrease in the air heat source temperature but, with an increase, collection from the air increases. When the air heat source temperature decreases, the evaporation temperature decreases in the single-evaporator working on the air and in the parallel operation but it levels off in the single-evaporator working on the water alone. When the water heat source temperature decreases, evaporation temperature drop is sharper in the single-evaporator working on the water than in the parallel operation, which suggests the transfer from the parallel operation to the single-evaporator working on the air. In the single-evaporator operation on the water heat source, the evaporation temperature linearly decreases with an increase in superheating. 1 ref., 10 figs.

Comparison of LCA results of low temperature heat plant using electric heat pump, absorption heat pump and gas-fired boiler

International Nuclear Information System (INIS)

Nitkiewicz, Anna; Sekret, Robert

2014-01-01

Highlights: • Usage of geothermal heat pump can bring environmental benefits. • The lowest environmental impact for whole life cycle is obtained for absorption heat pump. • The value of heat pump COP has a significant influence on environmental impact. • In case of coal based power generation the damage to human health is significant. - Abstract: This study compares the life cycle impacts of three heating plant systems which differ in their source of energy and the type of system. The following heating systems are considered: electric water-water heat pump, absorption water-water heat pump and natural gas fired boiler. The heat source for heat pump systems is low temperature geothermal source with temperature below 20 °C and spontaneous outflow 24 m 3 /h. It is assumed that the heat pumps and boiler are working in monovalent system. The analysis was carried out for heat networks temperature characteristic at 50/40 °C which is changing with outdoor temperature during heating season. The environmental life cycle impact is evaluated within life cycle assessment methodological framework. The method used for life cycle assessment is eco-indicator ‘99. The functional unit is defined as heating plant system with given amount of heat to be delivered to meet local heat demand in assumed average season. The data describing heating plant system is derived from literature and energy analysis of these systems. The data describing the preceding life cycle phases: extraction of raw materials and fuels, production of heating devices and their transportation is taken from Ecoinvent 2.0 life cycle inventory database. The results were analyzed on three levels of indicators: single score indicator, damage category indicators and impact category indicator. The indicators were calculated for characterization, normalization and weighting phases as well. SimaPro 7.3.2 is the software used to model the systems’ life cycle. The study shows that heating plants using a low

Renewable-based low-temperature district heating for existing buildings in various stages of refurbishment

DEFF Research Database (Denmark)

Brand, Marek; Svendsen, Svend

2013-01-01

Denmark is aiming for a fossil-free heating sector for buildings by 2035. Judging by the national heating plan, this will be achieved mainly by a further spread of DH (district heating) based on the renewable heat sources. To make the most cost-effective use of these sources, the DH supply...... and, for 98% of the year, to below 60 °C. However for the temperatures below 60 °C a low-temperature DH substation is required for DHW (domestic hot water) heating. This research shows that renewable sources of heat can be integrated into the DH system without problems and contribute to the fossil...... temperature should be as low as possible. We used IDA–ICE software to simulate a typical Danish single-family house from the 1970s connected to DH at three different stages of envelope and space heating system refurbishment. We wanted to investigate how low the DH supply temperature can be without reducing...

Experimental study of energy performance in low-temperature hydronic heating systems

DEFF Research Database (Denmark)

Hesaraki, Arefeh; Bourdakis, Eleftherios; Ploskić, Adnan

2015-01-01

Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply....... The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45°C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22°C in all cases. For energy calculations......, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2...

Alternative solutions for inhibiting Legionella in domestic hot water systems based on low-temperature district heating

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2015-01-01

Abstract District heating is a cost-effective way of providing heat to high heat density areas. Low-temperature district heating (LTDH) is a promising way to make district heating more energy-efficient and adaptable to well-insulated buildings with low heating demand in the future. However, one c...... systems. They have the additional benefit of reducing the heat loss of the hot water system. The alternative design solutions both enrich our options for water sanitation and improve the energy efficiency of our energy systems....... concern is the multiplication of Legionella due to insufficient temperature elevation with low-temperature supply. The aim of this study was to find optimal solutions to this dilemma for specific situations. The solutions were of two types: alternative system designs and various methods of sterilization...... methods, thermal treatment, ionization, chlorine, chlorine dioxide, ultraviolet light, photocatalysis and filtration are discussed as the most frequently used methods in hot water systems. The characteristics, efficacy and operation methods of LTDH using the solutions investigated are documented...

Exploitation of low-temperature energy sources from cogeneration gas engines

International Nuclear Information System (INIS)

Caf, A.; Urbancl, D.; Trop, P.; Goricanec, D.

2016-01-01

This paper describes an original and innovative technical solution for exploiting low-temperature energy sources from cogeneration gas reciprocating engines installed within district heating systems. This solution is suitable for those systems in which the heat is generated by the use of reciprocating engines powered by gaseous fuel for combined heat and power production. This new technical solution utilizes low-temperature energy sources from a reciprocating gas engine which is used for a combined production of heat and power. During the operation of the cogeneration system low-temperature heat is released, which can be raised to as much as 85 °C with the use of a high-temperature heat-pump, thus enabling a high-temperature regime for heating commercial buildings, district heating or in industrial processes. In order to demonstrate the efficiency of utilizing low-temperature heat sources in the cogeneration system, an economic calculation is included which proves the effectiveness and rationality of integrating high-temperature heat-pumps into new or existing systems for combined heat and power production with reciprocating gas engines. - Highlights: • The use of low-temperature waste heat from the CHP is described. • Total energy efficiency of the CHP can be increased to more than 103.3%. • Low-temperature heat is exploited with high-temperature heat pump. • High-temperature heat pump allows temperature rise to up to 85 °C. • Exploitation of low-temperature waste heat increases the economics of the CHP.

Solar-assisted heat pump – A sustainable system for low-temperature water heating applications

International Nuclear Information System (INIS)

Chaturvedi, S.K.; Gagrani, V.D.; Abdel-Salam, T.M.

2014-01-01

Highlights: • DX-SAHP water heaters systems are economical as well as energy conserving. • The economic analysis is performed using the life cycle cost (LCC) analysis. • LCC can be optimized with respect to the collector area at a specific temperature. • For high load temperature range a two stage heat pump system is more appropriate. - Abstract: Direct expansion solar assisted heat pump systems (DX-SAHP) have been widely used in many applications including water heating. In the DX-SAHP systems the solar collector and the heat pump evaporator are integrated into a single unit in order to transfer the solar energy to the refrigerant. The present work is aimed at studying the use of the DX-SAHP for low temperature water heating applications. The novel aspect of this paper involves a detailed long-term thermo-economic analysis of the energy conservation potential and economic viability of these systems. The thermal performance is simulated using a computer program that incorporates location dependent radiation, collector, economic, heat pump and load data. The economic analysis is performed using the life cycle cost (LCC) method. Results indicate that the DX-SAHP water heaters systems when compared to the conventional electrical water heaters are both economical as well as energy conserving. The analysis also reveals that the minimum value of the system life cycle cost is achieved at optimal values of the solar collector area as well as the compressor displacement capacity. Since the cost of SAHP system presents a barrier to mass scale commercialization, the results of the present study indicating that the SAHP life cycle cost can be minimized by optimizing the collector area would certainly be helpful in lowering, if not eliminating, the economic barrier to these systems. Also, at load temperatures higher than 70 °C, the performance of the single stage heat pump degrades to the extent that its cost and efficiency advantages over the electric only system are

Thermodynamic analysis of a low-temperature waste heat recovery system based on the concept of solar chimney

International Nuclear Information System (INIS)

Chen, Kai; Wang, Jiangfeng; Dai, Yiping; Liu, Yuqi

2014-01-01

Highlights: • A low grade waste heat recovery system based on the concept of solar chimney is proposed. • The effects of three key factors on the system performance are examined. • Thermodynamics analysis is to find a better way to utilize low grade heat source efficiently. - Abstract: The utilization of low-temperature waste heat draws more and more attention due to serious energy crisis nowadays. This paper proposes a low-temperature waste heat recovery system based on the concept of solar chimney. In the system, low-temperature waste heat is used to heat air to produce an air updraft in the chimney tower. The air updraft propels a turbine fixed at the base of the chimney tower to convert waste heat into electricity. The mathematical model of the system is established based on first law and second law of thermodynamics. Hot water is selected as the representative of low-temperature waste heat sources for researching. The heat source temperature, ambient air temperature and area of heat transfer are examined to evaluate their effects on the system performance such as velocity of updraft, mass flow rate of air, power output, conversion efficiency, and exergy efficiency. The velocity of air demonstrates a better stability than the mass flow rate of air and the pressure difference when temperature of heat source, ambient air temperature or area of heat transfer changes

Experimental investigation and feasibility analysis on a capillary radiant heating system based on solar and air source heat pump dual heat source

International Nuclear Information System (INIS)

Zhao, M.; Gu, Z.L.; Kang, W.B.; Liu, X.; Zhang, L.Y.; Jin, L.W.; Zhang, Q.L.

2017-01-01

Graphical abstract: (a) Vertical temperature gradient in Case 3, (b) PMV and PPD of the test room in Case 3, (c) operating time of SPCTS and ASHP systems in Case 3 and (d) the proportion of SPCTS operating time. - Highlights: • A capillary heating system based on solar and air source heat pump was developed. • Influence of supply water temperature on solar energy saving rate was investigated. • Heating performance and thermal comfort of capillary heating system were analyzed. • Low temperature heating with capillary is suitable for solar heating system. - Abstract: Due to sustainable development, solar energy has drawn much attention and been widely applied in buildings. However, the application of solar energy is limited because of its instability, intermittency and low energy density in winter. In order to use low density and instable solar energy source for heating and improve the utilization efficiency of solar energy, a solar phase change thermal storage (SPCTS) heating system using a radiant-capillary-terminal (RCT) to effectively match the low temperature hot water, a phase change thermal storage (PCTS) to store and continuously utilize the solar energy, and an air source heat pump (ASHP) as an alternate energy, was proposed and set up in this research. Series of experiments were conducted to obtain the relation between the solar radiation utilization rate and the heating supply temperatures, and to evaluate the performance of the RCT module and the indoor thermal environment of the system for its practical application in a residential building in the north-western City of Xi’an, China. The results show that energy saving of the solar heating system can be significantly improved by reducing the supplied water temperature, and the supplied water temperature of the RCT would be no more than 35 °C. The capillary radiation heating can adopt a lower water temperature and create a good thermal comfort environment as well. These results may lead to the

Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC

Science.gov (United States)

Mikielewicz, Dariusz; Mikielewicz, Jarosław

2011-12-01

In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.

Heat pump using dual heat sources of air and water. Performance in cooling mode; Mizu kuki ryonetsugen heat pump no kenkyu. Reibo unten ni okeru seino

Energy Technology Data Exchange (ETDEWEB)

Ito, S; Miura, N [Kanagawa Institute of Technology, Kanagawa (Japan); Uchikawa, Y [Kubota Corp., Osaka (Japan)

1997-11-25

When a heat pump is used for cooling purpose, it is possible to utilize different kinds of waste water as high-heat sources. However, these heat sources would have their temperatures vary with seasons and time in a day. Therefore, a discussion was given on performance of a heat pump when water and air heat sources are used for condensers during cooling operation independently, in series and in parallel, respectively. The air condenser shows an equivalent COP as compared with the water condenser when air temperature is lower by about 8 degC than water temperature. At the same heat source temperature, the COP for the water condenser indicated a value higher by about 0.6 than the case of the air condenser. A method to use condensers in parallel experiences little contribution from the air heat source, and performance of the heat pump decreases below the case of using the water heat source independently when the air heat source temperature becomes higher than that of the water heat source. In the case of series use in which a water condenser is installed in front and an air condenser in rear, its effect is exhibited when temperature in the air heat source is lower than that in the water heat source. Better performance was shown than in operating the water heat source independently. 2 refs., 9 figs.

Measured Performance of a Low Temperature Air Source Heat Pump

Energy Technology Data Exchange (ETDEWEB)

Johnson, R. K. [Johnson Research LLC, Pueblo West, CO (United States)

2013-09-01

A 4-ton Low Temperature Heat Pump (LTHP) manufactured by Hallowell International was installed in a residence near New Haven, Connecticut and monitored over two winters of operation. After attending to some significant service issues, the heat pump operated as designed. This report should be considered a review of the dual compressor 'boosted heat pump' technology. The Low Temperature Heat Pumpsystem operates with four increasing levels of capacity (heat output) as the outdoor temperature drops. The system was shown to select capacity correctly, supplying the appropriate amount of heat to the house across the full range of outdoor temperatures. The system's Coefficient of Performance (Seasonal COP, or SCOP) over two entire winters was calculated, based on measured data, to be 3.29over the first winter and 2.68 over the second winter. A second seasonal efficiency calculation by a different method yielded a SCOP of 2.78 for the first winter and 2.83 for the second winter. This second seasonal efficiency calculation was determined by comparing measured heat pump energy use to the in situ energy use with resistance heat alone. This method is the ratio of the slopes of thedaily energy use load lines.

Ground-water temperature of the Wyoming quadrangle in central Delaware : with application to ground-water-source heat pumps

Science.gov (United States)

Hodges, Arthur L.

1982-01-01

Ground-water temperature was measured during a one-year period (1980-81) in 20 wells in the Wyoming Quadrangle in central Delaware. Data from thermistors set at fixed depths in two wells were collected twice each week, and vertical temperature profiles of the remaining 18 wells were made monthly. Ground-water temperature at 8 feet below land surface in well Jc55-1 ranged from 45.0 degrees F in February to 70.1 degrees F in September. Temperature at 35 feet below land surface in the same well reached a minimum of 56.0 degrees F in August, and a maximum of 57.8 degrees F in February. Average annual temperature of ground water at 25 feet below land surface in all wells ranged from 54.6 degrees F to 57.8 degrees F. Variations of average temperature probably reflect the presence or absence of forestation in the recharge areas of the wells. Ground-water-source heat pumps supplied with water from wells 30 or more feet below land surface will operate more efficiently in both heating and cooling modes than those supplied with water from shallower depths. (USGS)

Energy, economy and exergy evaluations of the solutions for supplying domestic hot water from low-temperature district heating in Denmark

International Nuclear Information System (INIS)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

Highlights: • Provided domestic hot water configurations for low-temperature district heating. • Various building typologies and district heating supply temperatures were included. • Different scenarios were evaluated from the energy, economy and exergy aspects. • The benefits of lower return temperature to district heating were investigated. - Abstract: District heating in Denmark is going through the transition from 3rd generation (80/40 °C) to 4th generation (50–55 °C/25 °C) systems in preparation for district heating based completely on renewable fuels by 2035. However, concern about Legionella growth and reduced comfort with low-temperature domestic hot water supply may be discouraging the implementation of low-temperature district heating. Aimed at providing possible solutions, this study modelled various proposals for district heating systems with supply temperatures of 65 °C, 50 °C and 35 °C and for two different building topologies. Evaluation models were built to investigate the energy, economy and exergy performances of the proposed domestic hot water systems in various configurations. The configurations of the devised domestic hot water substations were optimised to fit well with both low and ultra-low-temperature district heating and to reduce the return temperature to district heating. The benefits of lower return temperatures were also analysed compared with the current district heating situation. The evaluation results show that the decentralized substation system with instantaneous heat exchanger unit performed better under the 65 °C and 50 °C district heating scenarios, while the individual micro tank solution consumed less energy and cost less in the 35 °C district heating scenario.

Desalination by very low temperature nuclear heat

International Nuclear Information System (INIS)

Saari, Risto

1977-01-01

A new sea water desalination method has been developed: Nord-Aqua Vacuum Evaporation, which utilizes waste heat at a very low temperature. The requisite vacuum is obtained by the aid of a barometric column and siphon, and the dissolved air is removed from the vacuum by means of water flows. According to test results from a pilot plant, the process is operable if the waste heat exists at a temperature 7degC higher than ambient. The pumping energy which is then required is 9 kcal/kg, or 1.5% of the heat of vaporization of water. Calculations reveal that the method is economically considerably superior to conventional distilling methods. (author)

Energy and exergy analysis of low temperature district heating network

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

2012-01-01

is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand...... energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply.......Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network...

Off-design performance analysis of Kalina cycle for low temperature geothermal source

International Nuclear Information System (INIS)

Li, Hang; Hu, Dongshuai; Wang, Mingkun; Dai, Yiping

2016-01-01

Highlights: • The off-design performance analysis of Kalina cycle is conducted. • The off-design models are established. • The genetic algorithm is used in the design phase. • The sliding pressure control strategy is applied. - Abstract: Low temperature geothermal sources with brilliant prospects have attracted more and more people’s attention. Kalina cycle system using ammonia water as working fluid could exploit geothermal energy effectively. In this paper, the quantitative analysis of off-design performance of Kalina cycle for the low temperature geothermal source is conducted. The off-design models including turbine, pump and heat exchangers are established preliminarily. Genetic algorithm is used to maximize the net power output and determine the thermodynamic parameters in the design phase. The sliding pressure control strategy applied widely in existing Rankine cycle power plants is adopted to response to the variations of geothermal source mass flow rate ratio (70–120%), geothermal source temperature (116–128 °C) and heat sink temperature (0–35 °C). In the off-design research scopes, the guidance for pump rotational speed adjustment is listed to provide some reference for off-design operation of geothermal power plants. The required adjustment rate of pump rotational speed is more sensitive to per unit geothermal source temperature than per unit heat sink temperature. Influence of the heat sink variation is greater than that of the geothermal source variation on the ranges of net power output and thermal efficiency.

Research results from a prototype for power generation from low temperature heat sources in small and medium sized sawmills

Energy Technology Data Exchange (ETDEWEB)

Tveit, Tor-Martin; Hoeeg, Arne; Asphjell, Trond-Atle; Horn, Henning

2010-07-01

In this paper we present research results from a low temperature power generation unit prototype, SPP 2-67A, installed at the timber company Moelven Eidsvold Vaerk in Norway. The power generation unit is a Stirling cycle reciprocating engine connected to a generator, which is designed to combine the mature technology for high temperature Stirling engines (as seen for instance as air independent propulsion (AIP) units in submarines) and recent academic work on low temperature Stirling engines. The power generation unit is installed in a boiler room at the Moelven Eidsvold Vaerk plant and uses steam at approximately 1.5 bar pressure as a heat source. The steam is generated in the 5.5 MW biomass-fuelled boiler, where bark of Norway spruce (Picea abies) is the main biofuel. The installation has been intended both to use hot water as a heat sink to demonstrate CHP operation, and cold water from the grid to demonstrate maximum power generation from surplus steam. The installation is part of a research project partly financed by the Research Council of Norway, with the goal of testing new technology to improve the use of bioenergy resources and conversion of heat from biofuels to power. (Author)

Performance of low-temperature district heating for low-energy houses

DEFF Research Database (Denmark)

Brand, Marek; Dalla Rosa, Alessandro; Svendsen, Svend

2010-01-01

A Low Energy District Heating (LEDH) network supplying district heating water with temperature 50°C was built in Lærkehaven-Lystrup, Denmark, as a part of the ongoing “Energy Technology Development and Demonstration Programme” [EUDP, 2008] focused on “CO2-reduction in low energy buildings and com...

New nuclear heat sources for district heating

International Nuclear Information System (INIS)

Lerouge, B.

1975-01-01

The means by which urban oil heating may be taken over by new energy sources, especially nuclear, are discussed. Several possibilities exist: pressurized water reactors for high powers, and low-temperature swimming-pool-type process-heat reactors for lower powers. Both these cases are discussed [fr

Energy, economy and exergy evaluations of the solutions for supplying domestic hot water from low-temperature district heating in Denmark

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

District heating in Denmark is going through the transition from 3rd generation (80/40 °C) to 4th generation (50-55 °C/25 °C) systems in,preparation for district heating based completely on renewable fuels by 2035. However, concern about Legionella growth and reduced comfort with low......-temperature domestic hot water supply may be discouraging the implementation of low-temperature district heating. Aimed at providing possible solutions, this study modelled various proposals for district heating systems with supply temperatures of 65 °C, 50 °C and 35 °C and for two different building topologies....... Evaluation models were built to investigate the energy, economy and exergy performances of the proposed domestic hot water systems in various configurations. The configurations of the devised domestic hot water substations were optimised to fit well with both low and ultra-low-temperature district heating...

Low-temperature synthesis of allyl dimethylamine by selective heating under microwave irradiation used for water treatment

International Nuclear Information System (INIS)

Tian Binghui; Luan Zhaokun; Li Mingming

2005-01-01

Low-temperature synthesis of allyl dimethylamine (ADA) by selective heating under microwave irradiation (MI) used for water treatment is investigated. The effect of MI, ultrasound irradiation (UI) and conventional heating on yield of ADA, reaction time and the flocculation efficiency of polydiallyl dimethylammunion chloride (PDADMAC) prepared form ADA were studied. The results show that by selective heating at low temperature, MI not only increases yield of ADA and reduces reaction time, but also greatly enhances the flocculation efficiency of PDADMAC

Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic......This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 degrees C and around 40 degrees C at the substations. To avoid the proliferation...... performance of the substations, separate models were built based on standard assumptions. The relative heat and electricity delivered for preparing DHW were calculated. The results showed that substations with storage tanks and heat pumps have high relative electricity demand, which leads to higher integrated...

A thermoacoustic engine capable of utilizing multi-temperature heat sources

International Nuclear Information System (INIS)

Qiu Limin; Wang Bo; Sun Daming; Liu Yu; Steiner, Ted

2009-01-01

Low-grade energy is widespread. However, it cannot be utilized with high thermal efficiency directly. Following the principle of thermal energy cascade utilization, a thermoacoustic engine (TE) with a new regenerator that can be driven by multiple heat sources at different temperature levels is proposed. Taking a regenerator that utilizes heat sources at two temperatures as an example, theoretical research has been conducted on a traveling-wave TE with the new regenerator to predict its performance. Experimental verification is also done to demonstrate the benefits of the new regenerator. Results indicate that a TE with the new regenerator utilizing additional heat at a lower temperature experiences an increase in pressure ratio, acoustic power, efficiency, and exergy efficiency with proper heat input at an appropriate temperature at the mid-heater. A regenerator that uses multi-temperature heat sources can provide a means of recovering lower grade heat.

Power Optimization of Organic Rankine-cycle System with Low-Temperature Heat Source Using HFC-134a

Energy Technology Data Exchange (ETDEWEB)

Baik, Young Jin; Kim, Min Sung; Chang, Ki Chang; Lee, Young Soo; Ra, Ho Sang [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

2011-01-15

In this study, an organic Rankine-cycle system using HFC-134a, which is a power cycle corresponding to a low temperature heat source, such as that for geothermal power generation, was investigated from the view point of power optimization. In contrast to conventional approaches, the heat transfer and pressure drop characteristics of the working fluid within the heat exchangers were taken into account by using a discretized heat exchanger model. The inlet flow rates and temperatures of both the heat source and the heat sink were fixed. The total heat transfer area was fixed, whereas the heat-exchanger areas of the evaporator and the condenser were allocated to maximize the power output. The power was optimized on the basis of three design parameters. The optimal combination of parameters that can maximize power output was determined on the basis of the results of the study. The results also indicate that the evaporation process has to be optimized to increase the power output.

Simulation analysis on dynamic performance of a combined solar/air dual source heat pump water heater

International Nuclear Information System (INIS)

Deng, Weishi; Yu, Jianlin

2016-01-01

Highlights: • A modified direct expansion solar-assisted heat pump water heater is investigated. • An additional air source evaporator is used in parallel way in the M-DX-SHPWH system. • The M-DX-SHPWH system displays a higher performance at the low solar radiation. • Effects of solar radiation and air temperature on the performance are discussed. - Abstract: This paper investigated a combined solar/air dual source heat pump water heater system for domestic water heating application. In the dual source system, an additional air source evaporator is introduced in parallel way based on a conventional direct expansion solar-assisted heat pump water heaters (DX-SHPWH) system, which can improve the performance of the DX-SHPWH system at a low solar radiation. In the present study, a dynamic mathematical model based on zoned lump parameter approach is developed to simulate the performance of the system (i.e. a modified DX-SHPWH (M-DX-SHPWH) system). Using the model, the performance of M-DX-SHPWH system is evaluated and then compared with that of the conventional DX-SHPWH system. The simulation results show the M-DX-SHPWH system has a better performance than that of the conventional DX-SHPWH system. At a low solar radiation of 100 W/m"2, the heating time of the M-DX-SHPWH decreases by 19.8% compared to the DX-SHPWH when water temperature reaches 55 °C. Meanwhile, the COP on average increases by 14.1%. In addition, the refrigerant mass flow rate distribution in the air source evaporator and the solar collector of the system, the allocation between the air source evaporator and the solar collector areas and effects of solar radiation and ambient air temperature on the system performance are discussed.

Energy consumption modeling of air source electric heat pump water heaters

International Nuclear Information System (INIS)

Bourke, Grant; Bansal, Pradeep

2010-01-01

Electric heat pump air source water heaters may provide an opportunity for significant improvements in residential water heater energy efficiency in countries with temperate climates. As the performance of these appliances can vary widely, it is important for consumers to be able to accurately assess product performance in their application to maximise energy savings and ensure uptake of this technology. For a given ambient temperature and humidity, the performance of an air source heat pump water heater is strongly correlated to the water temperature in or surrounding the condenser. It is therefore important that energy consumption models for these products duplicate the real-world water temperatures applied to the heat pump condenser. This paper examines a recently published joint Australian and New Zealand Standard, AS/NZS 4234: 2008; Heated water systems - Calculation of energy consumption. Using this standard a series TRNSYS models were run for several split type air source electric heat pump water heaters. An equivalent set of models was then run utilizing an alternative water use pattern. Unfavorable errors of up to 12% were shown to occur in modeling of heat pump water heater performance using the current standard compared to the alternative regime. The difference in performance of a model using varying water use regimes can be greater than the performance difference between models of product.

Low Temperature District Heating for Future Energy Systems

DEFF Research Database (Denmark)

Schmidt, Dietrich; Kallert, Anna; Blesl, Markus

2017-01-01

of the building stock. Low temperature district heating (LTDH) can contribute significantly to a more efficient use of energy resources as well as better integration of renewable energy (e.g. geothermal or solar heat), and surplus heat (e.g. industrial waste heat) into the heating sector. LTDH offers prospects......The building sector is responsible for more than one third of the final energy consumption of societies and produces the largest amount of greenhouse gas emissions of all sectors. This is due to the utilisation of combustion processes of mainly fossil fuels to satisfy the heating demand...... for both the demand side (community building structure) and the supply side (network properties or energy sources). Especially in connection with buildings that demand only low temperatures for space heating. The utilisation of lower temperatures reduces losses in pipelines and can increase the overall...

Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating

International Nuclear Information System (INIS)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 °C and around 40 °C at the substations. To avoid the proliferation of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic performance of the substations, separate models were built based on standard assumptions. The relative heat and electricity delivered for preparing DHW were calculated. The results showed that substations with storage tanks and heat pumps have high relative electricity demand, which leads to higher integrated costs considering both heat and electricity for DHW preparation. The substations with in-line electric heaters have low relative electricity usage because very little heat is lost due to the instantaneous DHW preparation. Accordingly, the substations with in-line electric heaters would have the lowest energy cost for DHW preparation. To achieve optimal design and operation for the ULTDH substation, the electricity peak loads of the in-line electric heaters were analysed according to different DHW-heating strategies. - Highlights: • Five different substations supplied with ultra-low-temperature district heating were measured. • The relative heat and electricity delivered for DHW preparation were modelled for different substations. • The levelized cost of the five substations in respect of DHW preparation was calculated. • The feasibility of applying instantaneous electric heater with normal power supply was tested.

Experimental investigation on water quality standard of Yangtze River water source heat pump.

Science.gov (United States)

Qin, Zenghu; Tong, Mingwei; Kun, Lin

2012-01-01

Due to the surface water in the upper reaches of Yangtze River in China containing large amounts of silt and algae, high content of microorganisms and suspended solids, the water in Yangtze River cannot be used for cooling a heat pump directly. In this paper, the possibility of using Yangtze River, which goes through Chongqing, a city in southwest China, as a heat source-sink was investigated. Water temperature and quality of the Yangtze River in the Chongqing area were analyzed and the performance of water source heat pump units in different sediment concentrations, turbidity and algae material conditions were tested experimentally, and the water quality standards, in particular surface water conditions, in the Yangtze River region that adapt to energy-efficient heat pumps were also proposed. The experimental results show that the coefficient of performance heat pump falls by 3.73% to the greatest extent, and the fouling resistance of cooling water in the heat exchanger increases up to 25.6% in different water conditions. When the sediment concentration and the turbidity in the river water are no more than 100 g/m3 and 50 NTU respectively, the performance of the heat pump is better, which can be used as a suitable river water quality standard for river water source heat pumps.

Exergy and Energy Analysis of Low Temperature District Heating Network

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

is in line with a pilot project that is carrying out in Denmark with network supply/return temperature at 55oC/25 oC. The consumer domestic hot water (DHW) demand is supplied with a special designed district heating (DH) storage tank. The space heating (SH) demand is supplied with a low temperature radiator......Low temperature district heating (LTDH) with reduced network supply and return temperature provides better match of the low quality building thermal demand and the low quality waste heat supply. In this paper, an exemplary LTDH network was designed for 30 low energy demand residential houses, which....... The network thermal and hydraulic conditions were simulated under steady state with an in-house district heating network design and simulation code. Through simulation, the overall system energetic and exergetic efficiencies were calculated and the exergy losses for the major district heating system...

Low temperature nuclear heat

Energy Technology Data Exchange (ETDEWEB)

Kotakorpi, J.; Tarjanne, R. [comps.

1977-08-01

The meeting was concerned with the use of low grade nuclear heat for district heating, desalination, process heat, and agriculture and aquaculture. The sessions covered applications and demand, heat sources, and economics.

Modelling and multi-scenario analysis for electric heat tracing system combined with low temperature district heating for domestic hot water supply

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

Low temperature district heating (LTDH) is a cost-efficient way of supplying space heating and domestic hot water (DHW) for buildings in urban areas. However, there is concern that the potential hygiene problems (Legionella) might occur if LTDH is implemented, especially for large buildings...... performance on heat loss saving, and it also gave benefits to district heating network by sharing part of the heating load....

Energy and exergy analysis of low temperature district heating network

International Nuclear Information System (INIS)

Li, Hongwei; Svendsen, Svend

2012-01-01

Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand. The space heating demand is supplied through floor heating in the bathroom and low temperature radiators in the rest of rooms. The network thermal and hydraulic conditions are simulated under steady state. A district heating network design and simulation code is developed to incorporate the network optimization procedure and the network simultaneous factor. Through the simulation, the overall system energy and exergy efficiencies are calculated and the exergy losses for the major district heating system components are identified. Based on the results, suggestions are given to further reduce the system energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply. -- Highlights: ► Exergy and energy analysis for low and medium temperature district heating systems. ► Different district heating network dimensioning methods are analyzed. ► Major exergy losses are identified in the district heating network and the in-house substations. ► Advantages to apply low temperature district heating are highlighted through exergy analysis. ► The influence of thermal by-pass on system exergy/energy performance is analyzed.

Mapping of potential heat sources for heat pumps for district heating in Denmark

International Nuclear Information System (INIS)

Lund, Rasmus; Persson, Urban

2016-01-01

The ambitious policy in Denmark on having a 100% renewable energy supply in 2050 requires radical changes to the energy systems to avoid an extensive and unsustainable use of biomass resources. Currently, wind power is being expanded and the increasing supply of electricity is slowly pushing the CHP (combined heat and power) plants out of operation, reducing the energy efficiency of the DH (district heating) supply. Here, large heat pumps for district heating is a frequently mentioned solution as a flexible demand for electricity and an energy efficient heat producer. The idea is to make heat pump use a low temperature waste or ambient heat source, but it has so far been very unclear which heat sources are actually available for this purpose. In this study eight categories of heat sources are analysed for the case of Denmark and included in a detailed spatial analysis where the identified heat sources are put in relation to the district heating areas and the corresponding demands. The analysis shows that potential heat sources are present near almost all district heating areas and that sea water most likely will have to play a substantial role as a heat source in future energy systems in Denmark. - Highlights: • The availability of heat sources for heat pumps in Denmark are mapped and quantified. • A novel methodology for assessment of low temperature industrial excess heat is presented. • There are heat sources available for 99% of district heating networks in Denmark. • The concentration of heat sources is generally bigger around bigger cities than smaller. • Ambient temperature heat sources will be more needed in district heating of big cities.

A novel absorption refrigeration cycle for heat sources with large temperature change

International Nuclear Information System (INIS)

Yan, Xiaona; Chen, Guangming; Hong, Daliang; Lin, Shunrong; Tang, Liming

2013-01-01

To increase the use efficiency of available thermal energy in the waste gas/water, a novel high-efficient absorption refrigeration cycle regarded as an improved single-effect/double-lift configuration is proposed. The improved cycle using an evaporator/absorber (E/A) promotes the coefficient of performance and reduces the irreversible loss. Water–lithium bromide is used as the working pair and a simulation study under the steady working conditions is conducted. The results show that the temperature of waste gas discharged is about 20 °C lower than that of the conventional single-effect cycle and the novel cycle we proposed can achieve more cooling capacity per unit mass of waste gas/water at the simulated working conditions. -- Graphical abstract: Pressure – temperature diagram for water – lithium bromide. Highlights: ► A novel waste heat-driven absorption refrigeration cycle is presented. ► The novel cycle can reject heat at much lower temperature. ► The available temperature range of heat source of the proposed cycle is wider. ► Multiple heat sources with different temperatures can be used in the novel cycle

Desalination using low grade heat sources

Science.gov (United States)

Gude, Veera Gnaneswar

A new, low temperature, energy-efficient and sustainable desalination system has been developed in this research. This system operates under near-vacuum conditions created by exploiting natural means of gravity and barometric pressure head. The system can be driven by low grade heat sources such as solar energy or waste heat streams. Both theoretical and experimental studies were conducted under this research to evaluate and demonstrate the feasibility of the proposed process. Theoretical studies included thermodynamic analysis and process modeling to evaluate the performance of the process using the following alternate energy sources for driving the process: solar thermal energy, solar photovoltaic/thermal energy, geothermal energy, and process waste heat emissions. Experimental studies included prototype scale demonstration of the process using grid power as well as solar photovoltaic/thermal sources. Finally, the feasibility of the process in reclaiming potable-quality water from the effluent of the city wastewater treatment plant was studied. The following results have been obtained from theoretical analysis and modeling: (1) The proposed process can produce up to 8 L/d of freshwater for 1 m2 area of solar collector and evaporation chamber respectively with a specific energy requirement of 3122 kJ for 1 kg of freshwater production. (2) Photovoltaic/thermal (PV/T) energy can produce up to 200 L/d of freshwater with a 25 m2 PV/T module which meets the electricity needs of 21 kWh/d of a typical household as well. This configuration requires a specific energy of 3122 kJ for 1 kg of freshwater production. (3) 100 kg/hr of geothermal water at 60°C as heat source can produce up to 60 L/d of freshwater with a specific energy requirement of 3078 kJ for 1 kg of freshwater production. (4) Waste heat released from an air conditioning system rated at 3.25 kW cooling, can produce up to 125 L/d of freshwater. This configuration requires an additional energy of 208 kJ/kg of

Energy Efficiency of Low-Temperature Deaeration of Makeup Water for a District Heating System

Energy Technology Data Exchange (ETDEWEB)

Sharapov, V. I., E-mail: vlad-sharapov2008@yandex.ru; Kudryavtseva, E. V. [Ulyanovsk State Technical University (Russian Federation)

2016-07-15

It is shown that the temperature of makeup water in district heating systems has a strong effect on the energy efficiency of turbines of thermal power plants. A low-temperature deaeration process that considerably improves the energy efficiency of thermal power plants is developed. The desorbing agent is the gas supplied to the burners of the boiler. The energy efficiency of the process for a typical unit of thermal power plant is assessed.

Optimization criteria for low temperature waste heat utilization

International Nuclear Information System (INIS)

Kranebitter, F.

1977-01-01

A special case in this field is the utilization of very low temperature waste heat. The temperature level under consideration in this paper is in the range between the body temperature of human beings and their environment. The waste heat from power generation and industrial processes is also considered. Thermal energy conversion will be mainly accomplished by heat cycles where discharged waste heat is reverse proportional to the upper cycle temperature. Limiting this upper cycle temperature by technological reasons the optimization of the heat cycle will depend on the nature of the cycle itself and specially on the temperature selected for the heat discharge. The waste heat discharge is typical for the different kinds of heat cycles and the paper presents the four most important of them. Feasible heat transfer methods and their economic evaluations are discussed and the distillation processes will be the basis for further considerations. The waste heat utilization for distillation purposes could be realized by three different cycles, the open cycle, the closed cycle and the multy cycle. Resulting problems as deaeration of large water streams and removal of the dissolved gases and their solutions are also discussed. (M.S.)

Domestic Hot Water Production with Ground Source Heat Pump in Apartment Buildings

Directory of Open Access Journals (Sweden)

Jukka Yrjölä

2015-08-01

Full Text Available Producing domestic hot water (DHW with a ground source heat pump (GSHP is challenging due to the high temperature (HT of DHW. There are many studies proving the better performance of cascade heat pumps compared to single-stage heat pumps when the difference between the condensing and the evaporation temperature is large. In this system approach study, different GSHP arrangements are described and computationally compared. A two-stage heat pump arrangement is introduced in which water tanks of the heating system are utilized for warming up the DHW in two stages. It is shown that the electricity consumption with this two-stage system is approximately 31% less than with the single-stage heat pump and 12% less than with the cascade system. Further, both low temperature (LT and HT heat pumps can run alone, which is not common in cascade or other two-stage heat pumps. This is advantageous because the high loads of the space heating and DHW production are not simultaneous. Proper insulation of the DHW and recirculation pipe network is essential, and drying towel rails or other heating coils should be avoided when aiming for a high efficiency. The refrigerants in the calculations are R407C for the LT heat pump and R134a for the HT heat pump. Investment costs are excluded from calculations.

Energetic and Exergetic Analysis of Low and Medium Temperature District Heating Network Integration

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

In this paper, energetic and exergetic approaches were applied to an exemplary low temperature district heating (LTDH) network with supply/return water temperature at 55oC/25 oC. The small LTDH network is annexed to a large medium temperature district heating (MTDH) network. The LTDH network can ...... will reduce the amount of water supply from the MTDH network and improve the system energy conversion efficiency. Through the simulation, the system energetic and exergetic efficiencies based on the two network integration approaches were calculated and evaluated.......In this paper, energetic and exergetic approaches were applied to an exemplary low temperature district heating (LTDH) network with supply/return water temperature at 55oC/25 oC. The small LTDH network is annexed to a large medium temperature district heating (MTDH) network. The LTDH network can...... be supplied through upgrading the return water from the MTDH network with a small centralized heat pump. Alternatively, the supply and return water from the MTDH network can be mixed with a shunt at the junction point to supply the LTDH network. Comparing with the second approach, the heat pump system...

Innovative system for delivery of low temperature district heating

Directory of Open Access Journals (Sweden)

Anton Ivanov Ianakiev

2017-01-01

Full Text Available An innovative Low Temperature District Heating (LTDH local network is developed in Nottingham, supported by REMOURBAN project, part of the H2020 Smart City and Community Lighthouse scheme. It was proposed that a branch emanating from the return pipe of the of the existing district heating system in Nottingham would be created to use low temperature heating for the first time in UK. The development is aimed to extract wasted (unused heat from existing district heating system and make it more efficient and profitable. Four maisonette blocks of 94 low-raised flats, at Nottingham demo site of the REMOURBAN project will be connected to this new LTDH system. The scheme will provide a primary supply of heat and hot water at approximately 50oC to 60oC. Innovated solutions have been put forward to overcome certain barriers, such as legionella related risks and peak loads during extreme heating seasons and occasional maintenance.

Potential of low-temperature nuclear heat applications

International Nuclear Information System (INIS)

1986-12-01

At present, more than one third of the fossil fuel currently used is being consumed to produce space heating and to meet industrial needs in many countries of the world. Imported oil still represents a large portion of this fossil fuel and despite its present relatively low price future market evolutions with consequent upward cost revisions cannot be excluded. Thus the displacement of the fossil fuel by cheaper low-temperature heat produced in nuclear power plants is a matter which deserves careful consideration. Technico-economic studies in many countries have shown that the use of nuclear heat is fully competitive with most of fossil-fuelled plants, the higher investment costs being offset by lower production cost. Another point in favour of heat generation by nuclear source is its indisputable advantage in terms of benefits to the environment. The IAEA activity plans for 1985-86 concentrate on information exchange with specific emphasis on the design criteria, operating experience, safety requirements and specifications of heat-only reactors, co-generation plants and existing power plants backfitted for additional heat applications. The information gained up to 1985 was discussed during the Advisory Group Meeting on the Potential of Low-Temperature Nuclear Heat Applications held in the Federal Institute for Reactor Research, Wuerenlingen, Switzerland in September 1985 and, is included in the present Technical Document

Heat flux estimate of warm water flow in a low-temperature diffuse flow site, southern East Pacific Rise 17°25‧ S

Science.gov (United States)

Goto, Shusaku; Kinoshita, Masataka; Mitsuzawa, Kyohiko

2003-09-01

A low-temperature diffuse flow site associated with abundant vent fauna was found by submersible observations on the southern East Pacific Rise at 17°25‧ S in 1997. This site was characterized by thin sediment covered pillow and sheet lavas with collapsed pits up to ˜15 m in diameter. There were three warm water vents (temperature: 6.5 to 10.5 °C) within the site above which the vented fluids rise as plumes. To estimate heat flux of the warm water vents, a temperature logger array was deployed and the vertical temperature distribution in the water column up to 38 m above the seafloor was monitored. A stationary deep seafloor observatory system was also deployed to monitor hydrothermal activity in this site. The temperature logger array measured temperature anomalies, while the plumes from the vents passed through the array. Because the temperature anomalies were measured in only specific current directions, we identified one of the vents as the source. Heat flux from the vent was estimated by applying a plume model in crossflow in a density-stratified environment. The average heat flux from September 13 to October 18, 1997 was 39 MW. This heat flux is as same order as those of high-temperature black smokers, indicating that a large volume flux was discharged from the vent (1.9 m3/s). Previous observations found many similar warm water flow vents along the spreading axis between 17°20‧ S 30‧ S. The total heat flux was estimated to be at least a few hundred mega-watts. This venting style would contribute to form effluent hydrothermal plumes extended above the spreading axis.

Energy, economy and exergy evaluations of the solutions for supplying domestic hot water from low-temperature district heating in Denmark

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

. Evaluation models were built to investigate the energy, economy and exergy performances of the proposed domestic hot water systems in various configurations. The configurations of the devised domestic hot water substations were optimised to fit well with both low and ultra-low-temperature district heating...... °C and 50 °C district heating scenarios, while the individual micro tank solution consumed less energy and cost less in the 35 °C district heating scenario....

Research on a Household Dual Heat Source Heat Pump Water Heater with Preheater Based on ASPEN PLUS

Directory of Open Access Journals (Sweden)

Xiang Gou

2016-12-01

Full Text Available This article proposes a dual heat source heat pump bathroom unit with preheater which is feasible for a single family. The system effectively integrates the air source heat pump (ASHP and wastewater source heat pump (WSHP technologies, and incorporates a preheater to recover shower wastewater heat and thus improve the total coefficient of performance (COP of the system, and it has no electric auxiliary heating device, which is favorable to improve the security of the system operation. The process simulation software ASPEN PLUS, widely used in the design and optimization of thermodynamic systems, was used to simulate various cases of system use and to analyze the impact of the preheater on the system. The average COP value of a system with preheater is 6.588 and without preheater it is 4.677. Based on the optimization and analysis, under the standard conditions of air at 25 °C, relative humidity of 70%, wastewater at 35 °C, wastewater flow rate of 0.07 kg/s, tap water at 15 °C, and condenser outlet water temperature at 50 °C, the theoretical COP of the system can reach 9.784 at an evaporating temperature of 14.96 °C, condensing temperature of 48.74 °C, and preheated water temperature of 27.19 °C.

Design of a low temperature district heating network with supply recirculation

DEFF Research Database (Denmark)

Li, Hongwei; Dalla Rosa, Alessandro; Svendsen, Svend

2010-01-01

The focus on continuing improving building energy efficiency and reducing building energy consumption brings the key impetus for the development of the new generation district heating (DH) system. In the new generation DH network, the supply and return temperature are designed low in order to sig...... calculates the heat loss in the twin pipe as that in the single pipe. The influence of this simplification on the supply/return water temperature prediction was analyzed by solving the coupled differential energy equations.......-pass system starts to function. The aim of this paper is to investigate the influence of by-pass water on the network return temperature and introduce the concept of supply water recirculation into the network design so that the traditional by-pass system can be avoided. Instead of mixing the by-pass water......The focus on continuing improving building energy efficiency and reducing building energy consumption brings the key impetus for the development of the new generation district heating (DH) system. In the new generation DH network, the supply and return temperature are designed low in order...

Experimental investigation on a small pumpless ORC (organic rankine cycle) system driven by the low temperature heat source

International Nuclear Information System (INIS)

Gao, P.; Wang, L.W.; Wang, R.Z.; Jiang, L.; Zhou, Z.S.

2015-01-01

A small pumpless ORC (organic rankine cycle) system with different scroll expanders modified from compressors of the automobile air-conditioner is established, and the refrigerant R245fa is chosen as the working fluid. Different hot water temperatures of 80, 85, 90 and 95 °C are employed to drive the pumpless ORC system. Experimental results show that a maximum shaft power of 361.0 W is obtained under the hot water temperature of 95 °C, whereas the average shaft power is 155.8 W. The maximum energy efficiency of 2.3% and the maximum exergy efficiency of 12.8% are obtained at the hot water temperature of 90 °C. Meanwhile a test rig for investigating the mechanical loss of the scroll expander is established. The torque caused by the internal mechanical friction of the expander is about 0.4 N m. Additionally, another scroll expander with a displacement of 86 ml/r is also employed to investigate how scroll expander displacement influences the performance of the pumpless ORC system. Finally, the performance of the pumpless ORC system is compared with that of the conventional ORC system, and experimental results show that the small pumpless ORC system has more advantages for the low-grade heat recovery. - Highlights: • A small pumpless ORC (organic rankine cycle) system is established, and different scroll expanders are tested. • The maximum energy and exergy efficiency are 2.3% and 12.8% respectively. • A maximum shaft power of 361.0 W is obtained under the heat source temperature of 95 °C. • The small pumpless ORC system has characteristics of the high efficiency.

Hybrid district heating system with heat supply from nuclear source

International Nuclear Information System (INIS)

Havelka, Z.; Petrovsky, I.

1987-01-01

Several designs are described of heat supply from large remote power sources (e.g., WWER-1000 nuclear power plants with a 1000 MW turbine) to localities where mainly steam distribution networks have been built but only some or none networks for hot water distribution. The benefits of the designs stem from the fact that they do not require the conversion of the local steam distribution system to a hot water system. They are based on heat supply from the nuclear power plant to the consumer area in hot water of a temperature of 150 degC to 200 degC. Part of the hot water heat will be used for the production of low-pressure steam which will be compressed using heat pumps (steam compressors) to achieve the desired steam distribution network specifications. Water of lower temperature can be used in the hot water network. The hot water feeder forms an automatic pressure safety barrier in heat supply of heating or technological steam from a nuclear installation. (Z.M.). 5 figs., 9 refs

Soil temperature distribution around a U-tube heat exchanger in a multi-function ground source heat pump system

International Nuclear Information System (INIS)

Li Shuhong; Yang Weihua; Zhang Xiaosong

2009-01-01

The imbalance of heat extracted from the earth by the underground heat exchangers in winter and ejected into it in summer is expected to affect the long term performance of conventional ground source heat pump (GSHP) in territories with a cold winter and a warm summer such as the middle and downstream areas of the Yangtze River in China. This paper presents a new multi-function ground source heat pump (MFGSHP) system which supplies hot water as well as space cooling/heating to mitigate the soil imbalance of the extracted and ejected heat by a ground source heat pump system. The heat transfer characteristic is studied and the soil temperature around the underground heat exchangers are simulated under a typical climatic condition of the Yangtze River. A three-dimensional model was constructed with the commercial computational fluid dynamics software FLUENT based on the inner heat source theory. Temperature distribution and variation trend of a tube cluster of the underground heat exchanger are simulated for the long term performance. The results show that the soil temperature around the underground tube keeps increasing due to the surplus heat ejected into the earth in summer, which deteriorates the system performance and may lead to the eventual system deterioration. The simulation shows that MFGSHP can effectively alleviate the temperature rise by balancing the heat ejected to/extracted from underground by the conventional ground source heat pump system. The new system also improves the energy efficiency.

Analysis and research on promising solutions of low temperature district heating without risk of legionella

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Fog, Jette M.

2014-01-01

Most regulations of domestic hot water supply temperature is around 55-60 oC, which potentially requires higher district heating temperature. However, high supply temperature of district heating causes many problems, such as the high heating loss, and obstacles for applying renewable energy...... resources. The most crucial restriction for applying low temperature district heating is the worry about the breakout of legionella, which exists preferably in low temperature hot water systems. Several novel techniques such as electric tracing and flat station were investigated for such dilemma. The pros...... and cons were compared in this paper. Both the energy and economy saving ratios were analysed comparing with high temperature supply scenario. Furthermore, the viability of the applications in different types of buildings for low temperature district heating (LTDH) was also discussed by using dynamic...

A general framework to select working fluid and configuration of ORCs for low-to-medium temperature heat sources

International Nuclear Information System (INIS)

Vivian, Jacopo; Manente, Giovanni; Lazzaretto, Andrea

2015-01-01

Highlights: • General guidelines are proposed to select ORC working fluid and cycle layout. • Distance between critical and heat source temperature for optimal fluid selection. • Separate contributions of cycle efficiency and heat recovery factor. - Abstract: The selection of the most suitable working fluid and cycle configuration for a given heat source is a fundamental step in the search for the optimum design of Organic Rankine Cycles. In this phase cycle efficiency and heat source recovery factor lead to opposite design choices in the achievement of maximum system efficiency and, in turn, maximum power output. In this work, both separate and combined effects of these two performance factors are considered to supply a thorough understanding of the compromise resulting in maximum performance. This goal is pursued by carrying out design optimizations of four different ORC configurations operating with twenty-seven working fluids and recovering heat from sensible heat sources in the temperature range 120–180 °C. Optimum working fluids and thermodynamic parameters are those which simultaneously allow high cycle efficiency and high heat recovery from the heat source to be obtained. General guidelines are suggested to reach this target for any system configuration. The distance between fluid critical temperature and inlet temperature of the heat source is found to play a key role in predicting the optimum performance of all system configurations regardless of the inlet temperature of the heat source

Increase of COP for heat transformer in water purification systems. Part II - Without increasing heat source temperature

International Nuclear Information System (INIS)

Romero, R.J.; Siqueiros, J.; Huicochea, A.

2007-01-01

The integration of a water purification system allows a heat transformer to increase the actual coefficient of performance, by the reduction of the amount of heat supplied by unit of heat. A new defined COP called COP WP is proposed for the present system, which considers the fraction of heat recycled. Simulation with proven software compares the performance of the modeling of an absorption heat transformer for water purification (AHTWP) operating with water/lithium bromide, as working fluid-absorbent pair. Plots of enthalpy-based coefficients of performance (COP ET ) and water purification coefficient of performance (COP WP ) are shown against absorber temperature for several thermodynamic operating conditions. The results showed that the proposed (AHTWP) system is capable of increasing the original value of COP ET up to 1.6 times its original value by recycling energy from a water purification system. The proposed COP WP allows increments for COP values from any experimental data for water purification or for any other distillation system integrated to a heat transformer, regardless of actual COP A value or working fluid-absorbent pair

Low Temperature Geothermal Resource Assessment for Membrane Distillation Desalination in the United States

Energy Technology Data Exchange (ETDEWEB)

Akar, Sertac; Turchi, Craig

2017-05-01

Substantial drought and declines in potable groundwater in the United States over the last decade has increased the demand for fresh water. Desalination of saline water such as brackish surface or groundwater, seawater, brines co-produced from oil and gas operations, industrial wastewater, blow-down water from power plant cooling towers, and agriculture drainage water can reduce the volume of water that requires disposal while providing a source of high-quality fresh water for industrial or commercial use. Membrane distillation (MD) is a developing technology that uses low-temperature thermal energy for desalination. Geothermal heat can be an ideal thermal-energy source for MD desalination technology, with a target range of $1/m3 to $2/m3 for desalinated water depending on the cost of heat. Three different cases were analyzed to estimate levelized cost of heat (LCOH) for integration of MD desalination technology with low-grade geothermal heat: (1) residual heat from injection brine at a geothermal power plant, (2) heat from existing underutilized low-temperature wells, and (3) drilling new wells for low-temperature resources. The Central and Western United States have important low-temperature (<90 degrees C) geothermal resource potential with wide geographic distribution, but these resources are highly underutilized because they are inefficient for power production. According to the USGS, there are 1,075 identified low temperature hydrothermal systems, 55 low temperature sedimentary systems and 248 identified medium to high temperature geothermal systems in the United States. The estimated total beneficial heat potential from identified low temperature hydrothermal geothermal systems and residual beneficial heat from medium to high temperature systems is estimated as 36,300 MWth, which could theoretically produce 1.4 to 7 million m3/day of potable water, depending on desalination efficiency.

Analytical investigation of low temperature lift energy conversion systems with renewable energy source

International Nuclear Information System (INIS)

Lee, Hoseong; Hwang, Yunho; Radermacher, Reinhard

2014-01-01

The efficiency of the renewable energy powered energy conversion system is typically low due to its moderate heat source temperature. Therefore, improving its energy efficiency is essential. In this study, the performance of the energy conversion system with renewable energy source was theoretically investigated in order to explore its design aspect. For this purpose, a computer model of n-stage low temperature lift energy conversion (LTLEC) system was developed. The results showed that under given operating conditions such as temperatures and mass flow rates of heat source and heat sink fluids the unit power generation of the system increased with the number of stage, and it became saturated when the number of staging reached four. Investigation of several possible working fluids for the optimum stage LTLEC system revealed that ethanol could be an alternative to ammonia. The heat exchanger effectiveness is a critical factor on the system performance. The power generation was increased by 7.83% for the evaporator and 9.94% for the condenser with 10% increase of heat exchanger effectiveness. When these low temperature source fluids are applied to the LTLEC system, the heat exchanger performance would be very critical and it has to be designed accordingly. - Highlights: •Energy conversion system with renewable energy is analytically investigated. •A model of multi-stage low temperature lift energy conversion systems was developed. •The system performance increases as the stage number is increased. •The unit power generation is increased with increase of HX effectiveness. •Ethanol is found to be a good alternative to ammonia

A novel PV/T-air dual source heat pump water heater system: Dynamic simulation and performance characterization

International Nuclear Information System (INIS)

Cai, Jingyong; Ji, Jie; Wang, Yunyun; Zhou, Fan; Yu, Bendong

2017-01-01

Highlights: • The PV/T evaporator and air source evaporator connect in parallel and operate simultaneously. • A dynamic model is developed to simulate the behavior of the system. • The thermal and electrical characteristics of the PV/T evaporator are evaluated. • The contribution of the air source evaporator and PV/T evaporator has been discussed. - Abstract: To enable the heat pump water heater maintain efficient operation under diverse circumstances, a novel PV/T-air dual source heat pump water heater (PV/T-AHPWH) has been proposed in this study. In the PV/T-AHPWH system, a PV/T evaporator and an air source evaporator connect in parallel and operate simultaneously to recover energy from both solar energy and environment. A dynamic model is presented to simulate the behavior of the PV/T-AHPWH system. On this basis, the influences of solar irradiation, ambient temperature and packing factor have been discussed, and the contributions of air source evaporator and PV/T evaporator are evaluated. The results reveal that the system can obtain efficient operation with the average COP above 2.0 under the ambient temperature of 10 °C and solar irradiation of 100 W/m 2 . The PV/T evaporator can compensate for the performance degradation of the air source evaporator caused by the increasing condensing temperature. As the evaporating capacity in PV/T evaporator remains at relatively low level under low irradiation, the air source evaporator can play the main role of recovering heat. Comparing the performance of dual source heat pump system employing PV/T collector with that utilizing normal solar thermal collector, the system utilizing PV/T evaporator is more efficient in energy saving and performance improvement.

Low-cost low-enthalpy geothermal heat for freshwater production: Innovative applications using thermal desalination processes

KAUST Repository

Bundschuh, Jochen; Ghaffour, NorEddine; Mahmoudi, Hacè ne; Goosen, Mattheus F A; Mushtaq, Shahbaz; Hoinkis, Jan

2015-01-01

The study is dedicated to exploring different types of low-cost low-enthalpy geothermal and their potential integration with conventional thermal-based water desalination and treatment technologies to deliver energy efficient, environmentally friendly solutions for water desalination and treatment, addressing global water crises. Our in-depth investigation through reviews of various low-enthalpy geothermal and conventional thermal-based technologies suggest that the geothermal option is superior to the solar option if low-cost geothermal heat is available because it provides a constant heat source in contrast to solar. Importantly, the stable heat source further allows up-scaling (> 1000 m3/day), which is not currently possible with solar. Solar-geothermal hybrid constellations may also be suitable in areas where both sources are available. The review also discovers that the innovative Membrane distillation (MD) process is very promising as it can be used for many different water compositions, salinity and temperature ranges. Either the geothermal water itself can be desalinated/treated or the geothermal heat can be used to heat feed water from other sources using heat exchangers. However, there are only few economic analyses for large-scale MD units and these are based on theoretical models using often uncertain assumptions resulting in a large variety of results.

Low-cost low-enthalpy geothermal heat for freshwater production: Innovative applications using thermal desalination processes

KAUST Repository

Bundschuh, Jochen

2015-03-01

The study is dedicated to exploring different types of low-cost low-enthalpy geothermal and their potential integration with conventional thermal-based water desalination and treatment technologies to deliver energy efficient, environmentally friendly solutions for water desalination and treatment, addressing global water crises. Our in-depth investigation through reviews of various low-enthalpy geothermal and conventional thermal-based technologies suggest that the geothermal option is superior to the solar option if low-cost geothermal heat is available because it provides a constant heat source in contrast to solar. Importantly, the stable heat source further allows up-scaling (> 1000 m3/day), which is not currently possible with solar. Solar-geothermal hybrid constellations may also be suitable in areas where both sources are available. The review also discovers that the innovative Membrane distillation (MD) process is very promising as it can be used for many different water compositions, salinity and temperature ranges. Either the geothermal water itself can be desalinated/treated or the geothermal heat can be used to heat feed water from other sources using heat exchangers. However, there are only few economic analyses for large-scale MD units and these are based on theoretical models using often uncertain assumptions resulting in a large variety of results.

Utilization of low temperature geothermal water in traditional and advanced agricultural applications

International Nuclear Information System (INIS)

Rossi, L.; Pacciaroni, F.

1992-01-01

The locations of large amounts of low temperature geothermal sources (30 to 80 degrees C) have been identified in Italy and in many European countries; one of the most interesting utilization of these sources is greenhouse heating. Surplus investment in comparison with conventional heating systems is justified only by the application of low cost technologies for well completion, heating distribution and waste heat treatment. In the last few years, many efforts have been made in the development of these technologies and selection of more profitable crops. Since 1984, ENEA (Italian Agency for Energy, New Technologies and the Environment) has carried out experimental work in two geothermal stations located in Canino (VT) and in Gorgo di Latisana (UD). In these plants, a number of greenhouses enveloped with plastic film are provided with different heating systems; the combination of soil and forced air heating is preferred. Plastic pipes, buried in the soil, are used as soil heating for horticulture and fruit production. For plot plant cultivation, soil heating is obtained by plastic pipes half-buried in a concrete floor. Asparagus cultivation is carried out with buried pipes. No additional heating with conventional fuel is provided in any greenhouse. During these years, ENEA has developed heating and water distribution technologies: current industrial components are generally utilized. Moreover, ENEA has recently completed an advanced automatic control system able to control geothermal greenhouses, manage water distribution, save energy and optimize environmental conditions

Utilization of low temperature geothermal water in traditional and advanced agricultural applications

Energy Technology Data Exchange (ETDEWEB)

Rossi, L.; Pacciaroni, F.

1992-12-31

The locations of large amounts of low temperature geothermal sources (30 to 80 degrees C) have been identified in Italy and in many European countries; one of the most interesting utilization of these sources is greenhouse heating. Surplus investment in comparison with conventional heating systems is justified only by the application of low cost technologies for well completion, heating distribution and waste heat treatment. In the last few years, many efforts have been made in the development of these technologies and selection of more profitable crops. Since 1984, ENEA (Italian Agency for Energy, New Technologies and the Environment) has carried out experimental work in two geothermal stations located in Canino (VT) and in Gorgo di Latisana (UD). In these plants, a number of greenhouses enveloped with plastic film are provided with different heating systems; the combination of soil and forced air heating is preferred. Plastic pipes, buried in the soil, are used as soil heating for horticulture and fruit production. For plot plant cultivation, soil heating is obtained by plastic pipes half-buried in a concrete floor. Asparagus cultivation is carried out with buried pipes. No additional heating with conventional fuel is provided in any greenhouse. During these years, ENEA has developed heating and water distribution technologies: current industrial components are generally utilized. Moreover, ENEA has recently completed an advanced automatic control system able to control geothermal greenhouses, manage water distribution, save energy and optimize environmental conditions.

Conversion of medium and low temperature heat to power

Science.gov (United States)

Fischer, Johann; Wendland, Martin; Lai, Ngoc Anh

2013-04-01

Presently most electricity is produced in power plants which use high temperature heat supplied by coal, oil, gas or nuclear fission and Clausius-Rankine cycles (CRC) with water as working fluid (WF). On the other hand, geo-, solar-, ocean-, and biogenic-heat have medium and low temperatures. At these temperatures, however, the use of other WF and/or other cycles can yield higher efficiencies than those of the water-CRC. For an assessment of the efficiency we model systems which include the heat transfer to and from the WF and the cycle. Optimization criterion is the exergy efficiency defined as the ratio of the net power output to the incoming exergy flow of the heat carrier. First, for a better understanding we discuss some thermodynamic properties of the WFs: 1) the critical point parameters, 2) the shape of the vapour- liquid coexistence curve in the temperature vs entropy (T,s)-diagram which may be either bell-shaped or overhanging [1,2], and 3) the shape of sub- and supercritical isobars for pure fluids and fluid mixtures. Second, we show that the problems of a CRC with water at lower temperatures are 1) the shape of the T,s-diagram and 2) the exergy loss during heat transfer to the WF. The first problem can be overcome by using an organic working fluid in the CRC which then is called organic Rankine cycle (ORC). The second problem is reduced by supercritical organic Rankine cycles (sORC) [1,2], trilateral cycles (TLC) and the more general power-flash cycles (PFC) [2], and organic flash cycles (OFC) [3]. Next, selected results for systems with the above mentioned cycles will be presented. The heat carrier inlet temperatures THC range from 120°C to 350°C.The pure working fluids are water, refrigerants, alkanes, aromates and siloxanes and have to be selected to match with THC. It is found that TLC with water have the highest efficiencies but show very large volume flows at lower temperatures. Moreover, expansion machines for TLC and PFC are still under

Low Temperature Geothermal Resource Assessment for Membrane Distillation Desalination in the United States: Preprint

Energy Technology Data Exchange (ETDEWEB)

Akar, Sertac; Turchi, Craig

2016-10-01

Substantial drought and declines in potable groundwater in the United States over the last decade has increased the demand for fresh water. Desalination of saline water such as brackish surface or groundwater, seawater, brines co-produced from oil and gas operations, industrial wastewater, blow-down water from power plant cooling towers, and agriculture drainage water can reduce the volume of water that requires disposal while providing a source of high-quality fresh water for industrial or commercial use. Membrane distillation (MD) is a developing technology that uses low-temperature thermal energy for desalination. Geothermal heat can be an ideal thermal-energy source for MD desalination technology, with a target range of $1/m3 to $2/m3 for desalinated water depending on the cost of heat. Three different cases were analyzed to estimate levelized cost of heat (LCOH) for integration of MD desalination technology with low-grade geothermal heat: (1) residual heat from injection brine at a geothermal power plant, (2) heat from existing underutilized low-temperature wells, and (3) drilling new wells for low-temperature resources. The Central and Western United States have important low-temperature (<90 degrees C) geothermal resource potential with wide geographic distribution, but these resources are highly underutilized because they are inefficient for power production. According to the USGS, there are 1,075 identified low temperature hydrothermal systems, 55 low temperature sedimentary systems and 248 identified medium to high temperature geothermal systems in the United States. The estimated total beneficial heat potential from identified low temperature hydrothermal geothermal systems and residual beneficial heat from medium to high temperature systems is estimated as 36,300 MWth, which could theoretically produce 1.4 to 7 million m3/day of potable water, depending on desalination efficiency.

Application of Abaqus to analysis of the temperature field in elements heated by moving heat sources

Directory of Open Access Journals (Sweden)

W. Piekarska

2010-10-01

Full Text Available Numerical analysis of thermal phenomena occurring during laser beam heating is presented in this paper. Numerical models of surface andvolumetric heat sources were presented and the influence of different laser beam heat source power distribution on temperature field wasanalyzed. Temperature field was obtained by a numerical solution the transient heat transfer equation with activity of inner heat sources using finite element method. Temperature distribution analysis in welded joint was performed in the ABAQUS/Standard solver. The DFLUXsubroutine was used for implementation of the movable welding heat source model. Temperature-depended thermophysical properties for steelwere assumed in computer simulations. Temperature distribution in laser beam surface heated and butt welded plates was numericallyestimated.

Performance analysis of double organic Rankine cycle for discontinuous low temperature waste heat recovery

International Nuclear Information System (INIS)

Wang Dongxiang; Ling Xiang; Peng Hao

2012-01-01

This research proposes a double organic Rankine cycle for discontinuous waste heat recovery. The optimal operation conditions of several working fluids have been calculated by a procedure employing MATLAB and REFPROP. The influence of outlet temperature of heat source on the net power output, thermal efficiency, power consumption, mass flow rate, expander outlet temperature, cycle irreversibility and exergy efficiency at a given pinch point temperature difference (PPTD) has been analyzed. Pinch point analysis has also been employed to obtain a thermodynamic understanding of the ORC performance. Of all the working fluids investigated, some performances between each working fluid are rather similar. For a fixed low temperature heat source, the optimal operation condition should be mainly determined by the heat carrier of the heat source, and working fluids have limited influence. Lower outlet temperature of heat source does not always mean more efficient energy use. Acetone exhibits the least exergy destruction, while R245fa possesses the maximal exergy efficiency at a fixed PPTD. Wet fluids exhibit lower thermal efficiency than the others with the increasing of PPTD at a fixed outlet temperature of heat source. Dry and isentropic fluids offer attractive performance. - Highlights: ► We propose a double organic Rankine cycle for discontinuous waste heat recovery. ► Performance of organic Rankine cycle (ORC) is analyzed by pinch point analysis. ► The heat carrier of the heat source determines ORC optimal operation condition. ► Design of ORC heat exchangers prefers lower pinch point temperature difference.

Minimizing temperature instability of heat recovery hot water system utilizing optimized thermal energy storage

Science.gov (United States)

Suamir, I. N.; Sukadana, I. B. P.; Arsana, M. E.

2018-01-01

temperature of hot water during peak hot water demand and on that time between 06.00 and 10.00 hours, the hotel also experiences a low cooling demand. Subsequently, the temperature of hot water supplied drops down as low as 45 °C. The study was found that optimization on the TES can significantly minimize temperature variation of the hot water supplied to the hotel appliances. A TES of 30 m3 storage capacity is considered the optimum capacity which can reduce the temperature fluctuation from 17 K down to 3 K. The study also found that maintaining the storage temperature relatively lower than the condenser temperature could increase hot water production of the heat recovery system.

Challenges in Smart Low-Temperature District Heating Development

DEFF Research Database (Denmark)

Li, Hongwei; Wang, Stephen Jia

2014-01-01

Previous research and development shows that low temperature district heating (LTDH) system is economic feasible for low energy buildings and buildings at sparse areas. Coupling with reduced network temperature and well-designed district heating (DH) networks, LTDH can reduce network heat loss by...

Low to moderate temperature nanolaminate heater

Science.gov (United States)

Eckels, J Del [Livermore, CA; Nunes, Peter J [Danville, CA; Simpson, Randall L [Livermore, CA; Hau-Riege, Stefan [Fremont, CA; Walton, Chris [Oakland, CA; Carter, J Chance [Livermore, CA; Reynolds, John G [San Ramon, CA

2011-01-11

A low to moderate temperature heat source comprising a high temperature energy source modified to output low to moderate temperatures wherein the high temperature energy source modified to output low to moderate temperatures is positioned between two thin pieces to form a close contact sheath. In one embodiment the high temperature energy source modified to output low to moderate temperatures is a nanolaminate multilayer foil of reactive materials that produces a heating level of less than 200.degree. C.

Simulation and analysis on thermodynamic performance of surface water source heat pump system

Institute of Scientific and Technical Information of China (English)

Nan Lv; Qing Zhang; Zhenqian Chen; Dongsheng Wu

2017-01-01

This work established a thermodynamic performance model of a heat pump system containing a heat pump unit model, an air conditioning cooling and heating load calculation model, a heat exchanger model and a water pump performance model based on mass and energy balances. The thermodynamic performance of a surface water source heat pump air conditioning system was simulated and verified by comparing the simulation results to an actual engineering project. In addition, the effects of the surface water temperature, heat exchanger structure and surface water pipeline transportation system on the thermodynamic performance of the heat pump air conditioning system were analyzed. Under the simulated conditions in this paper with a cooling load of 3400 kW, the results showed that a 1 ℃ decrease in the surface water temperature leads to a 2.3 percent increase in the coefficient of performance; furthermore, an additional 100 m of length for the closed-loop surface water heat exchanger tube leads to a 0.08 percent increase in the coefficient of performance. To decrease the system energy consumption, the optimal working point should be specified according to the surface water transportation length.

Design of serially connected ammonia-water hybrid absorption-compression heat pumps for district heating with the utilisation of a geothermal heat source

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix

2016-01-01

District heating (DH) can reduce the primary energy consumption in urban areas with significant heat demands. The design of a serially connected ammonia-water hybrid absorption-compression heat pump system was investigated for operation in the Greater Copenhagen DH network in Denmark, in order...... to supply 7.2 MW heat at 85 °C utilizing a geothermal heat source at 73 °C. Both the heat source and heat sink experience a large temperature change over the heat transfer process, of which a significant part may be achieved by direct heat exchange. First a generic study with a simple representation...

Heat transfer and carryover of low pressure water in a heated vertical tube

International Nuclear Information System (INIS)

Smith, T.A.

1976-01-01

Local heat transfer coefficients in the stable film boiling and dispersed flow regimes were studied for the upward flow of low pressure water in a heated vertical tube. Wall temperatures were maintained constant with time and along the tube so that both axial and time temperature gradients approached zero. Heat flux along the tube was not constant but was applied so as to maintain a steady state temperature profile. A preheater was used to bring the liquid to saturation before it entered the main portion of the test section and in some cases the equilibrium quality was greater than zero at the entrance to the main test section. The test section was made of stainless steel, and the lower portion, the preheater, was heated directly by dc current. Copper block heat spikes were clamped to the upper test section and were used to apply the heat flux to maintain the wall temperature constant with time. Several theories for the different possible types of flow (laminar or turbulent, tube or film) were compared with the experimental data. The carry-over point for low flooding rates (1 inch/sec or less) was inferred from these comparisons and gave good agreement with the Plummer critical mass criterion for liquid carry-over

Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

of Legionella in the DHW (domestic hot water) and assure the comfortable temperature, all substations were installed with supplementary heating devices. Detailed measurements were taken in the substations, including the electricity demand of the supplementary heating devices. To compare the energy and economic...

Experimental investigation of moderately high temperature water source heat pump with non-azeotropic refrigerant mixtures

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shengjun; Wang, Huaixin; Guo, Tao [Department of Thermal Energy and Refrigeration Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China)

2010-05-15

Experimental investigations were carried out on non-azeotropic refrigerant mixtures, named M1A (mass fraction of 20%R152a and 80%R245fa), M1B (mass fraction of 37% R152a and 63%R245fa) and M1C (mass fraction of 50%R152a and 50%R245fa), based on a water-to-water heat pump system in the condensing temperature range of 70-90 C with a cycle temperature lift of 45 C. Performance of R245fa was tested for comparison. Unfair factors in experimental comparative evaluation research with the same apparatus were identified and corrected. Experimental cycle performance of the mixtures were tested and compared with improved experimental assessment methodology. The results show that all of the mixtures deliver higher discharge temperature, higher heating capacity, higher COP and higher {epsilon}{sub h,c} than R245fa. M1B presents the most excellent cycle performance and is recommended as working fluid for moderate/high temperature heat pump. (author)

Low-Temperature Baseboard Heaters in Built Environments

Energy Technology Data Exchange (ETDEWEB)

Ploskic, Adnan

2010-10-15

The European Union has adopted a plan to decrease 20 % of total energy consumption through improved energy efficiency by 2020. One way of achieving this challenging goal may be to use efficient water-based heating systems supplied by heat pumps or other sustainable systems. The goal of this research was to analyze and improve the thermal performance of water-based baseboard heaters at low-temperature water supply. Both numerical (CFD) and analytical simulations were used to investigate the heat efficiency of the system. An additional objective of this work was to ensure that the indoor thermal comfort was satisfied in spaces served by such a low-temperature heating system. Analyses showed that it was fully possible to cover both transmission and ventilation heat losses using baseboard heaters supplied by 45 deg C water flow. The conventional baseboards, however, showed problems in suppressing the cold air down-flow created by 2.0 m high glazing and an outdoor temperature of -12 deg C. The draught discomfort at ankle level was slightly above the upper limit recommended by international and national standards. On the other hand, thermal baseboards with integrated ventilation air supply showed better ability to neutralize cold downdraught at the same height and conditions. Calculations also showed that the heat output from the integrated system with one ventilation inlet was approximately twice as high as that of the conventional one. The general conclusion from this work was that low temperature baseboards, especially with integrated ventilation air supply, are an efficient heating system and able to be combined with devices that utilize the low-quality sustainable energy sources such as heat pumps

Air source absorption heat pump in district heating: Applicability analysis and improvement options

International Nuclear Information System (INIS)

Wu, Wei; Shi, Wenxing; Li, Xianting; Wang, Baolong

2015-01-01

Highlights: • Applicability of air source absorption heat pump (ASAHP) district heating is studied. • Return temperature and energy saving rate (ESR) in various conditions are optimized. • ASAHP is more suitable for shorter distance or lower temperature district heating. • Two options can reduce the primary return temperature and improve the applicability. • The maximum ESR is improved from 13.6% to 20.4–25.6% by compression-assisted ASAHP. - Abstract: The low-temperature district heating system based on the air source absorption heat pump (ASAHP) was assessed to have great energy saving potential. However, this system may require smaller temperature drop leading to higher pump consumption for long-distance distribution. Therefore, the applicability of ASAHP-based district heating system is analyzed for different primary return temperatures, pipeline distances, pipeline resistances, supplied water temperatures, application regions, and working fluids. The energy saving rate (ESR) under different conditions are calculated, considering both the ASAHP efficiency and the distribution consumption. Results show that ASAHP system is more suitable for short-distance district heating, while for longer-distance heating, lower supplied hot water temperature is preferred. In addition, the advantages of NH 3 /H 2 O are inferior to those of NH 3 /LiNO 3 , and the advantages for warmer regions and lower pipeline resistance are more obvious. The primary return temperatures are optimized to obtain maximum ESRs, after which the suitable distances under different acceptable ESRs are summarized. To improve the applicability of ASAHP, the integration of cascaded heat exchanger (CHX) and compression-assisted ASAHP (CASAHP) are proposed, which can reduce the primary return temperature. The integration of CHX can effectively improve the applicability of ASAHP under higher supplied water temperatures. As for the utilization of CASAHP, higher compression ratio (CR) is better in

Low-temperature heating systems and public administration

Energy Technology Data Exchange (ETDEWEB)

Boerner, H

1981-06-01

The even temperature distribution and comfortable climate in rooms heated by low-temperature heating systems is mostly due to one of the preconditions of this type of heating system namely, efficient thermal insulation of the rooms. Thermal insulation is already required as part of the pertinent legal regulations but it is also in the interest of the builder-owner as it will, in the long run, greatly reduce the heating cost.

Energy saving analysis on mine-water source heat pump in a residential district of Henan province, central China

Science.gov (United States)

Wang, Hong; Duan, Huanlin; Chen, Aidong

2018-02-01

In this paper, the mine-water source heat pump system is proposed in residential buildings of a mining community. The coefficient of performance (COP) and the efficiency of exergy are analyzed. The results show that the COP and exergy efficiency of the mine-water source heat pump are improved, the exergy efficiency of mine-water source heat pump is more than 10% higher than that of the air source heat pump.The electric power conservation measure of “peak load shifting” is also emphasized in this article. It shows that itis a very considerable cost in the electric saving by adopting the trough period electricity to produce hot water. Due to the proper temperature of mine water, the mine-watersource heat pump unit is more efficient and stable in performance, which further shows the advantage of mine-water source heat pump in energy saving and environmental protection. It provides reference to the design of similar heat pump system as well.

A flexible and low cost experimental stand for air source heat pump for Smart Buildings

DEFF Research Database (Denmark)

Crăciun, Vasile S.; Bojesen, Carsten; Blarke, Morten

2012-01-01

Energy systems are faced with the challenges of reducing dependency on fossil fuels, while handling increasing penetration levels of intermittent renewables such as wind and solar power. At the same time, the efficient consumption of energy is vital for avoiding the impacts from increasing fuel...... prices. A significant part of this challenge may be dealt with in the way space heating, space cooling, and domestic hot water production which is provided to residential and commercial buildings. Air source heat pumps (ASHP) are widely used conversion technologies for providing building thermal energy...... services; cooling, heating, and water heating. ASHP does not have a constant temperature for the primary source like: soil, ground water, or surface water heat pumps. In result, laboratory experiments and tests are faced by the problem of having to handle a wide range of conditions under which...

Measurement of low-temperature specific heat

International Nuclear Information System (INIS)

Stewart, G.R.

1983-01-01

The measurement of low-temperature specific heat (LTSH) (0.1 K< T<60 K) has seen a number of breakthroughs both in design concepts and instrumentation in the last 15 years: particularly in small sample calorimetry. This review attempts to provide an overview of both large and small sample calorimetry techniques at temperatures below 60 K, with sufficient references to enable more detailed study. A comprehensive review is made of the most reliable measurements of the LTSH of 84 of the elements to illustrate briefly some of the problems of measurements and analysis, as well as to provide additional references. More detail is devoted to three special areas of low-temperature calorimetry that have seen rapid development recently: (1) measurement of the specific heat of highly radioactive samples, (2) measurement of the specific heat of materials in high magnetic fields (18 T), and (3) measurement of the specific heat of very small (100 μg) samples. The review ends with a brief discussion of the frontier research currently underway on microcalorimetry for nanogram sample weights

Low temperature heat source for power generation: Exhaustive analysis of a carbon dioxide transcritical power cycle

International Nuclear Information System (INIS)

Velez, Fredy; Segovia, Jose; Chejne, Farid; Antolin, Gregorio; Quijano, Ana; Carmen Martin, M.

2011-01-01

The main results of a theoretical work on the use of a low temperature heat source for power generation through a carbon dioxide transcritical power cycle are reported in this paper. The procedure for analyzing the behaviour of the proposed cycle consisted in modifying the input pressure to the turbine from 66 bar, maintained constant each evaluated temperature (60 o C, 90 o C, 120 o C and 150 o C) until the net work was approximately zero. As a result, the maximum exergy efficiency was 50%, while the energy efficiencies obtained were 9.8%, 7.3%, 4.9% and 2.4% and the net specific work was 18.2 kJ/kg, 12.8 kJ/kg, 7.8 kJ/kg and 3.5 kJ/kg, respectively. Furthermore, the effect of the addition of an internal heat exchanger, which obviously supposed an increase in the efficiency, was analyzed. The analysis of the proposed system shows the viability of implementing this type of process as an energy alternative and/or strengthener of non-conventional energy sources in non-provided zones, or for increasing the energy efficiency in the industry. -- Highlights: → Energy and exergy analysis of a carbon dioxide transcritical power cycle is reported. → The effect of the inlet temperature to the turbine is evaluated. → Conditions of maximum efficiency and maximum net work are compared. → The inclusion of an IHX is also analysed.

Experimental Research of a Water-Source Heat Pump Water Heater System

OpenAIRE

Zhongchao Zhao; Yanrui Zhang; Haojun Mi; Yimeng Zhou; Yong Zhang

2018-01-01

The heat pump water heater (HPWH), as a portion of the eco-friendly technologies using renewable energy, has been applied for years in developed countries. Air-source heat pump water heaters and solar-assisted heat pump water heaters have been widely applied and have become more and more popular because of their comparatively higher energy efficiency and environmental protection. Besides use of the above resources, the heat pump water heater system can also adequately utilize an available wat...

Performance comparison of air-source heat pump water heater with different expansion devices

International Nuclear Information System (INIS)

Peng, Jing-Wei; Li, Hui; Zhang, Chun-Lu

2016-01-01

Highlights: • An air-source heat pump water heater model was developed and validated. • System performance with EEV, capillary tube or short tube orifice were compared. • Short tube orifice is more suitable for heat pump water heater than capillary tube. - Abstract: Air source heat pump water heater (ASHPWH) is designed to work under wide operating conditions. Therefore, both the system and components require higher reliability and stability than ordinary heat pump air-conditioning systems. In this paper, a quasi-steady-state system model of ASHPWH using electronic expansion valve (EEV), capillary tube or short tube orifice as expansion device is developed and validated by a prototype using R134a and scroll compressor, by which the system performance is evaluated and compared at varying water temperature and different ambient temperature. Flow characteristics of those three expansion devices in ASHPWH are comparatively analyzed. Results show that the EEV throttling system performs best. Compared with capillary tube, flow characteristics of short tube orifice are closer to that of EEV and therefore more suitable for ASHPWH. Reliability concern of liquid carryover to the compressor in the system using short tube orifice is investigated as well. Higher superheat or less system refrigerant charge could help mitigate the risk.

Heat source reconstruction from noisy temperature fields using an optimised derivative Gaussian filter

Science.gov (United States)

Delpueyo, D.; Balandraud, X.; Grédiac, M.

2013-09-01

The aim of this paper is to present a post-processing technique based on a derivative Gaussian filter to reconstruct heat source fields from temperature fields measured by infrared thermography. Heat sources can be deduced from temperature variations thanks to the heat diffusion equation. Filtering and differentiating are key-issues which are closely related here because the temperature fields which are processed are unavoidably noisy. We focus here only on the diffusion term because it is the most difficult term to estimate in the procedure, the reason being that it involves spatial second derivatives (a Laplacian for isotropic materials). This quantity can be reasonably estimated using a convolution of the temperature variation fields with second derivatives of a Gaussian function. The study is first based on synthetic temperature variation fields corrupted by added noise. The filter is optimised in order to reconstruct at best the heat source fields. The influence of both the dimension and the level of a localised heat source is discussed. Obtained results are also compared with another type of processing based on an averaging filter. The second part of this study presents an application to experimental temperature fields measured with an infrared camera on a thin plate in aluminium alloy. Heat sources are generated with an electric heating patch glued on the specimen surface. Heat source fields reconstructed from measured temperature fields are compared with the imposed heat sources. Obtained results illustrate the relevancy of the derivative Gaussian filter to reliably extract heat sources from noisy temperature fields for the experimental thermomechanics of materials.

Space heating with ultra-low-temperature district heating - a case study of four single-family houses from the 1980s

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

2017-01-01

. These benefits can be maximized if district heating temperatures are lowered as much as possible. In this paper we report on a project where 18 Danish single-family houses from the 1980s were supplied by ultra-low temperature district heating with a supply temperature as low as 45 degrees C for the main part...... of the year. The houses were heated by the existing hydraulic radiator systems, while domestic hot water was prepared by use of district heating and electric boosting. This paper evaluated the heating system temperatures that were necessary in order to maintain thermal comfort in four of the houses. First...... the four houses were modelled in the building simulation tool IDA ICE. The simulation models included the actual radiator sizes and the models were used to simulate the expected thermal comfort in the houses and resulting district heating return temperatures. Secondly measurements of the actual district...

On the development of high temperature ammonia-water hybrid absorption-compression heat pumps

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Markussen, Wiebke Brix; Reinholdt, Lars

2015-01-01

Ammonia-water hybrid absorption-compression heat pumps (HACHP) are a promising technology for development of ecient high temperature industrial heat pumps. Using 28 bar components HACHPs up to 100 °C are commercially available. Components developed for 50 bar and 140 bar show that these pressure...... limits may be possible to exceed if needed for actual applications. Feasible heat supply temperatures using these component limits are investigated. A feasible solution is defined as one that satisfies constraints on the COP, low and high pressure, compressor discharge temperature, vapour water content...... and volumetric heat capacity. The ammonia mass fraction and the liquid circulation ratio both influence these constraining parameters. The paper investigates feasible combinations of these parameters through the use of a numerical model. 28 bar components allow temperatures up to 111 °C, 50 bar up to 129°C...

Operational Performance Characterization of a Heat Pump System Utilizing Recycled Water as Heat Sink and Heat Source in a Cool and Dry Climate

Directory of Open Access Journals (Sweden)

Piljae Im

2018-01-01

Full Text Available The wastewater leaving from homes and businesses contains abundant low-grade energy, which can be utilized through heat pump technology to heat and cool buildings. Although the energy in the wastewater has been successfully utilized to condition buildings in other countries, it is barely utilized in the United States, until recently. In 2013, the Denver Museum of Nature & Science at Denver, the United States implemented a unique heat pump system that utilizes recycled wastewater from a municipal water system to cool and heat its 13,000 m2 new addition. This recycled water heat pump (RWHP system uses seven 105 kW (cooling capacity modular water-to-water heat pumps (WWHPs. Each WWHP uses R-410A refrigerant, has two compressors, and can independently provide either 52 °C hot water (HW or 7 °C chilled water (CHW to the building. This paper presents performance characterization results of this RWHP system based on the measured data from December 2014 through August 2015. The annual energy consumption of the RWHP system was also calculated and compared with that of a baseline Heating, Ventilation, and Air Conditioning (HVAC system which meets the minimum energy efficiencies that are allowed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 90.1-2013. The performance analysis results indicate that recycled water temperatures were favorable for effective operation of heat pumps. As a result, on an annual basis, the RWHP system avoided 50% of source energy consumption (resulting from reduction in natural gas consumption although electricity consumption was increased slightly, reduced CO2 emissions by 41%, and saved 34% in energy costs as compared with the baseline system.

Thermal performance of a modified ammonia–water power cycle for reclaiming mid/low-grade waste heat

International Nuclear Information System (INIS)

Junye, Hua; Yaping, Chen; Jiafeng, Wu

2014-01-01

Highlights: • A modified Kalina cycle is proposed for power and heat cogeneration from mid/low-grade waste heat. • A water-cooling solution cooler is set for cogeneration of sanitary or heating hot water. • Work concentration is determined for suitable turbine inlet pressure and positive back pressure. • Basic concentration should match work concentration for higher efficiency. • Sanitary water with 50.7 °C and capacity of a quarter of total reclaimed heat load is cogenerated. - Abstract: A modified Kalina cycle was simulated, which is a triple-pressure ammonia–water power cycle adding a preheater and a water-cooling solution cooler to the original loop. The cycle acquires higher power recovery efficiency by realizing proper internal recuperation and suitable temperature-difference in phase change processes to match both heat source and cooling water. The influences of some key parameters on the thermodynamic performance of the cycle were discussed, including the work and basic concentrations of solution, circulation multiple and the turbine inlet temperature. It is shown that the basic concentration should match the work concentration for higher efficiency. Although higher work concentration could be slightly beneficial to cycle efficiency, the work concentration is mainly determined by considering the suitable turbine inlet/back pressure. Besides, this cycle can be used as a cogeneration system of power and sanitary or heating hot water. The calculation example presented finally with the turbine inlet parameters of 300 °C/6 MPa and the cycle lowest temperature of 30 °C shows that the power recovery efficiency reaches 15.87%, which is about 16.6% higher than that of the steam Rankine cycle. And it also provides 50.7 °C sanitary water with about a quarter of the total heating load reclaimed

Examination of thermophotovoltaic GaSb cell technology in low and medium temperatures waste heat

Science.gov (United States)

Utlu, Z.; Önal, B. S.

2018-02-01

In this study, waste heat was evaluated and examined by means of thermophotovoltaic systems with the application of energy production potential GaSb cells. The aim of our study is to examine GaSb cell technology at low and medium temperature waste heat. The evaluation of the waste heat to be used in the system is designed to be used in the electricity, industry and iron and steel industry. Our work is research. Graphic analysis is done with Matlab program. The low and medium temperature waste heat graphs applied on the GaSb cell are in the results section. Our study aims to provide a source for future studies.

Discussion on application of water source heat pump technology to uranium mines

International Nuclear Information System (INIS)

An Qiang

2011-01-01

Application of water source heat pump units in recovering waste heat from uranium mines is discussed, and several forms of waste heat recovery are introduced. The problems in the application of water source heat pump technology are analyzed. Analysis results show that the water source heat pump technology has broad application prospects in uranium mines, and it is a way to exchange existing structure of heat and cold sources in uranium mines. (authors)

Investigation of ammonia/water hybrid absorption/compression heat pumps for heat supply temperatures above 100 °C

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Reinholdt, Lars; Markussen, Wiebke Brix

2014-01-01

The hybrid absorption/compression heat pump (HACHP) using ammonia-water as working fluid is a promising technology for development of a high temperature industrial heat pump. This is due to two properties inherent to the use of zeotropic mixtures: non-isothermal phase change and reduced vapour...... using these components. A technically and economically feasible solution is defined as one that satisfies constraints on the coefficient of performance (COP), low and high pressure, compressor discharge temperature and volumetric heat capacity. The ammonia mass fraction of the rich solution...

A novel design method for ground source heat pump

Directory of Open Access Journals (Sweden)

Dong Xing-Jie

2014-01-01

Full Text Available This paper proposes a novel design method for ground source heat pump. The ground source heat pump operation is controllable by using several parameters, such as the total meters of buried pipe, the space between wells, the thermal properties of soil, thermal resistance of the well, the initial temperature of soil, and annual dynamic load. By studying the effect of well number and well space, we conclude that with the increase of the well number, the inlet and outlet water temperatures decrease in summer and increase in winter, which enhance the efficiency of ground source heat pump. The well space slightly affects the water temperatures, but it affects the soil temperature to some extent. Also the ground source heat pump operations matching with cooling tower are investigated to achieve the thermal balance. This method greatly facilitates ground source heat pump design.

Ground Source Heat Supply in Moscow Oblast: Temperature Potential and Sustainable Depth of Heat Wells

Science.gov (United States)

Vasil'ev, G. P.; Gornov, V. F.; Dmitriev, A. N.; Kolesova, M. V.; Yurchenko, V. A.

2018-01-01

The paper is devoted to a problem of increasing the efficiency of low-potential geothermal heat in heat pump systems of residential buildings the Moscow oblast of Russia, including Moscow. Estimates of a natural geothermal potential in the Moscow oblast (based on climatological data for the period from 1982 to 2011) are presented and a "Typical climatic year of natural soil temperature variations for the geoclimatic conditions of the Moscow oblast, including the city of Moscow" is proposed. Numerical simulation of the influence of geothermal energy potential and the depth of heat wells on the efficiency of ground source heat pump systems for the heat supply of residential buildings is carried out. Analysis of the numerical simulation showed that the operation of a heat pump system in a house heating mode under the geoclimatic conditions of the Moscow oblast leads to a temperature drop of the heat-exchange medium circulating through heat wells to 5-6°C by the end of the first 10 years of operation, and the process stabilizes by the 15th year of operation, and further changes in the heat-exchange medium temperature do not any longer significantly affect the temperature of the heat-exchange medium in the heat well. In this case, the exact dependence of the heat-exchange medium temperature drop on the depth is not revealed. Data on the economically expedient heat well depth for the conditions of the Moscow oblast ensuring a net present value for the whole residential building life cycle are presented. It is found that the heat well depth of 60 m can be considered as an endpoint for the Moscow oblast, and a further heat well deepening is economically impractical.

Comparative technical-economic analysis of the low temperature heating systems

International Nuclear Information System (INIS)

Sharevski, Vasko; Sharevski, Milan

1994-01-01

A method for comparative technical-economic analysis between low temperature heating systems and heating systems with fossil fuel boiler plant, heat pump heating system and electrical heating systems is presented. The single and combined heating systems are analyzed. The technical-economic priority application of the heating system is determined according to the prices of the low temperature heat energy, fossil fuel heat energy, electrical energy, as well as to the coefficient of the annual use of the installed heating capacity, investment expenses, structure of the combined heating system and coefficient of performances of the heat pump. The combined heating system, composed with a low temperature heating subsystem, which is used to cover the base heat demands, and a oil boiler plant heating subsystem, for the top heat demands, have technical-economic justification and wide range of priority application, in comparison with single heating systems. (author)

Innovative system for delivery of low temperature district heating

OpenAIRE

Ianakiev, A; Cui, JM; Garbett, S; Filer, A

2017-01-01

An innovative low temperature district heating (LTDH) local network is developed in Nottingham, supported by the REMOURBAN project, part of the H2020 Smart City and Community Lighthouse scheme. It was proposed that a branch emanating from the return pipe of the existing district heating system in Nottingham would be created to use low temperature heating for the first time on such scale in the UK. The development is aimed to extract unused heat from existing district heating system and to mak...

Thermodynamic performance analysis of a combined power cycle using low grade heat source and LNG cold energy

International Nuclear Information System (INIS)

Kim, Kyoung Hoon; Kim, Kyung Chun

2014-01-01

Thermodynamic analysis of a combined cycle using a low grade heat source and LNG cold energy was carried out. The combined cycle consisted of an ammonia–water Rankine cycle with and without regeneration and a LNG Rankine cycle. A parametric study was conducted to examine the effects of the key parameters, such as ammonia mass fraction, turbine inlet pressure, condensation temperature. The effects of the ammonia mass fraction on the temperature distributions of the hot and cold streams in heat exchangers were also investigated. The characteristic diagram of the exergy efficiency and heat transfer capability was proposed to consider the system performance and expenditure of the heat exchangers simultaneously. The simulation showed that the system performance is influenced significantly by the parameters with the ammonia mass fraction having largest effect. The net work output of the ammonia–water cycle may have a peak value or increase monotonically with increasing ammonia mass fraction, which depends on turbine inlet pressure or condensation temperature. The exergy efficiency may decrease or increase or have a peak value with turbine inlet pressure depending on the ammonia mass fraction. - Highlights: • Thermodynamic analysis was performed for a combined cycle utilizing LNG cold energy. • Ammonia–water Rankine cycle and LNG Rankine cycle was combined. • A parametric study was conducted to examine the effects of the key parameters. • Characteristics of the exergy efficiency and heat transfer capability were proposed. • The system performance was influenced significantly by the ammonia mass fraction

The economics of supplying the supplementary heat in a closed loop water source heat pump system

International Nuclear Information System (INIS)

Johnson, R.P.; Bartkus, V.E.; Singh, J.B.

1993-01-01

The paper describes the details of a research and demonstration project that will be completed in August 1992 at a healthcare facility in northeastern Pennsylvania. The purpose of the project is to compare the economics of several methods of supplying the supplementary heating in a facility served by a closed loop water source heat pump system. The systems being tested include a storage hot water tank with electric resistance heaters and three air source heat pumps that have the ability to supply the same heat during on-peak hours as well as off-peak hours. The paper compares the projected operating costs of the following: (1) Gas boiler supplying the supplementary heat. (2) Stored hot water supplying the supplementary heat which is generated and stored during off-peak hours using resistance heat on PP ampersand L's offpeak rate. (3) Stored hot water supplying the supplementary heat generated during off-peak hours using the air source heat pumps on PP ampersand L's off-peak rate. (4) Hot water generated by the air source heat pumps supplying the supplementary loop heating on PP ampersand L's general service and time-of-day electric rates. It is generally known in the HVAC industry that a closed loop water source heat pump system can provide one of the most efficient means of space conditioning to a building with high internal gains by transferring the excess heat available in one part of the building to another part of the building where it may be needed for heating. The following flow diagram depicts the relationship of the air source heat pumps with the storage tanks and the building closed water loop

Performance variations of river water source heat pump system according to heat exchanger capacity variations

International Nuclear Information System (INIS)

Park, Seong Ryong; Baik, Young Jin; Lee, Young Soo; Kim, Hee Hwan

2003-01-01

The utilization of unused energy is important because it can afford to offer a chance to increase energy efficiency of a heat pump system. One of the promising unused energy sources is river water. It can be used as a heat source in both heating and cooling effectively with its superior features as a secondary working fluids. In this study, the performance of a 5HP heat pump system using river water as a heat source is investigated by both experiment and simulation. According to system simulation results, performance improvement of condenser seems more effective than that of evaporator for better COPH. The serial connection is also preferred among several methods to improve plate type heat exchanger performance. The experimental results show that the hot water of 50∼60 .deg. C can be acquired from water heat source of 5∼9 .deg. C with COPH of 2.7∼3.5

Performance analysis of ORC power generation system with low-temperature waste heat of aluminum reduction cell

Science.gov (United States)

Wang, Zhiqi; Zhou, Naijun; Jing, Guo

Performance of organic Rankine cycle (ORC) system to recover low-temperature waste heat from aluminum reduction cell was analyzed. The temperature of waste heat is 80°C-200°C and the flow rate is 3×105m3/h. The pinch temperature difference between waste heat and working fluids is 10°C. The results show that there is optimal evaporating temperature for maximum net power under the same pinch point. For heat source temperature range of 80°C-140°C and 150°C-170°C, the working fluid given biggest net power is R227ea and R236fa, respectively. When the temperature is higher than 180°C, R236ea generates the biggest net power. The variation of heat source temperature has important effect on net power. When the temperature decreases 10%, the net power will deviate 30% from the maximum value.

Nuclear heat source design for an advanced HTGR process heat plant

International Nuclear Information System (INIS)

McDonald, C.F.; O'Hanlon, T.W.

1983-01-01

A high-temperature gas-cooled reactor (HTGR) coupled with a chemical process facility could produce synthetic fuels (i.e., oil, gasoline, aviation fuel, methanol, hydrogen, etc.) in the long term using low-grade carbon sources (e.g., coal, oil shale, etc.). The ultimate high-temperature capability of an advanced HTGR variant is being studied for nuclear process heat. This paper discusses a process heat plant with a 2240-MW(t) nuclear heat source, a reactor outlet temperature of 950 0 C, and a direct reforming process. The nuclear heat source outputs principally hydrogen-rich synthesis gas that can be used as a feedstock for synthetic fuel production. This paper emphasizes the design of the nuclear heat source and discusses the major components and a deployment strategy to realize an advanced HTGR process heat plant concept

Experimental study of adsorption chiller driven by variable heat source

Energy Technology Data Exchange (ETDEWEB)

Wang, D.C.; Wang, Y.J.; Zhang, J.P.; Tian, X.L. [College of Electromechanical Engineering, Qingdao University, Qingdao 266071 (China); Wu, J.Y. [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030 (China)

2008-05-15

A silica gel-water adsorption chiller has been developed in recent years and has been applied in an air conditioning system driven by solar energy. The heat source used to drive the adsorption chiller is variable at any moment because the solar radiation intensity or the waste heat from engines varies frequently. An adsorption cooling system may be badly impacted by a variable heat source with temperature variations in a large range. In this work, a silica gel-water adsorption chiller driven by a variable heat source is experimentally studied. The influences of the variable heat source on the performance of the chiller are analyzed, especially for a continuous temperature increase process and a continuous temperature decrease process of the heat source. As an example, the dynamic characteristics of the heat source are also analyzed when solar energy is taken as the heat source of the adsorption chiller. According to the experimental results for the adsorption chiller and the characteristics of the heat source from solar energy, control strategies of the adsorption chiller driven by solar energy are proposed. (author)

Experimental study of adsorption chiller driven by variable heat source

International Nuclear Information System (INIS)

Wang, D.C.; Wang, Y.J.; Zhang, J.P.; Tian, X.L.; Wu, J.Y.

2008-01-01

A silica gel-water adsorption chiller has been developed in recent years and has been applied in an air conditioning system driven by solar energy. The heat source used to drive the adsorption chiller is variable at any moment because the solar radiation intensity or the waste heat from engines varies frequently. An adsorption cooling system may be badly impacted by a variable heat source with temperature variations in a large range. In this work, a silica gel-water adsorption chiller driven by a variable heat source is experimentally studied. The influences of the variable heat source on the performance of the chiller are analyzed, especially for a continuous temperature increase process and a continuous temperature decrease process of the heat source. As an example, the dynamic characteristics of the heat source are also analyzed when solar energy is taken as the heat source of the adsorption chiller. According to the experimental results for the adsorption chiller and the characteristics of the heat source from solar energy, control strategies of the adsorption chiller driven by solar energy are proposed

Analysis and comparison of methods for the preparation of domestic hot water from district heating system, selected renewable and non-renewable sources in low-energy buildings

Directory of Open Access Journals (Sweden)

Knapik Maciej

2018-01-01

Full Text Available The article presents an economic analysis and comparison of selected (district heating, natural gas, heat pump with renewable energy sources methods for the preparation of domestic hot water in a building with low energy demand. In buildings of this type increased demand of energy for domestic hot water preparation in relation to the total energy demand can be observed. As a result, the proposed solutions allow to further lower energy demand by using the renewable energy sources. This article presents the results of numerical analysis and calculations performed mainly in MATLAB software, based on typical meteorological years. The results showed that system with heat pump and renewable energy sources Is comparable with district heating system.

Analysis and comparison of methods for the preparation of domestic hot water from district heating system, selected renewable and non-renewable sources in low-energy buildings

Science.gov (United States)

Knapik, Maciej

2018-02-01

The article presents an economic analysis and comparison of selected (district heating, natural gas, heat pump with renewable energy sources) methods for the preparation of domestic hot water in a building with low energy demand. In buildings of this type increased demand of energy for domestic hot water preparation in relation to the total energy demand can be observed. As a result, the proposed solutions allow to further lower energy demand by using the renewable energy sources. This article presents the results of numerical analysis and calculations performed mainly in MATLAB software, based on typical meteorological years. The results showed that system with heat pump and renewable energy sources Is comparable with district heating system.

Low Temperature District Heating for Future Energy Systems

DEFF Research Database (Denmark)

Ford, Rufus; Pietruschka, Dirk; Sipilä, Kari

participants being VTT Technical Research Centre of Finland (VTT), Technical University of Denmark (DTU), Norwegian University of Science and Technology (NTNU), Stuttgart Technology University of Applied Sciences (HFT) and SSE Enterprise in United Kingdom. The demonstration cases described in the report......This report titled “Case studies and demonstrations” is the subtask D report of the IEA DHC|CHP Annex TS1 project “Low Temperature District Heating for Future Energy Systems” carried out between 2013 and 2016. The project was led by Fraunhofer Institute for Building Physics (IBP) with the other...... include examples on low temperature district heating systems, solar heating in a district heating system, heat pump based heat supply and energy storages for both peak load management and for seasonal heat storage. Some demonstrations have been implemented while others are at planning phase...

Sustainable renewable energy seawater desalination using combined-cycle solar and geothermal heat sources

KAUST Repository

Missimer, Thomas M.

2013-01-01

Key goals in the improvement of desalination technology are to reduce overall energy consumption, make the process "greener," and reduce the cost of the delivered water. Adsorption desalination (AD) is a promising new technology that has great potential to reduce the need for conventional power, to use solely renewable energy sources, and to reduce the overall cost of water treatment. This technology can desalt seawater or water of even higher salinity using waste heat, solar heat, or geothermal heat. An AD system can operate effectively at temperatures ranging from 55 to 80 °C with perhaps an optimal temperature of 80 °C. The generally low temperature requirement for the feedwater allows the system to operate quite efficiently using an alternative energy source, such as solar power. Solar power, particularly in warm dry regions, can generate a consistent water temperature of about 90 °C. Although this temperature is more than adequate to run the system, solar energy collection only can occur during daylight hours, thereby necessitating the use of heat storage during nighttime or very cloudy days. With increasing capacity, the need for extensive thermal storage may be problematic and could add substantial cost to the development of an AD system. However, in many parts of the world, there are subsurface geothermal energy sources that have not been extensively used. Combining a low to moderate geothermal energy recovery system to an AD system would provide a solution to the thermal storage issue. However, geothermal energy development from particularly Hot Dry Rock is limited by the magnitude of the heat flow required for the process and the thermal conductivity of the rock material forming the heat reservoir. Combining solar and geothermal energy using an alternating 12-h cycle would reduce the probability of depleting the heat source within the geothermal reservoir and provide the most effective use of renewable energy. © 2013 Desalination Publications.

Decentralized substations for low-temperature district heating with no Legionella risk, and low return temperatures

DEFF Research Database (Denmark)

Yang, Xiaochen; Li, Hongwei; Svendsen, Svend

2016-01-01

. From the results, realizing LTDH by the decentralized substation unit, 30% of the annual distribution heat loss inside the building can be saved compared to a conventional system with medium-temperature district heating. Replacing the bypass pipe with an in-line supply pipe and a heat pump...... with domestic hot water (DHW) circulation. In this study, a system with decentralized substations was analysed as a solution to this problem. Furthermore, a modification for the decentralized substation system were proposed in order to reduce the average return temperature. Models of conventional system...... with medium-temperature district heating, decentralized substation system with LTDH, and innovative decentralized substation system with LTDH were built based on the information of a case building. The annual distribution heat loss and the operating costs of the three scenarios were calculated and compared...

Temperature distribution of a simplified rotor due to a uniform heat source

Science.gov (United States)

Welzenbach, Sarah; Fischer, Tim; Meier, Felix; Werner, Ewald; kyzy, Sonun Ulan; Munz, Oliver

2018-03-01

In gas turbines, high combustion efficiency as well as operational safety are required. Thus, labyrinth seal systems with honeycomb liners are commonly used. In the case of rubbing events in the seal system, the components can be damaged due to cyclic thermal and mechanical loads. Temperature differences occurring at labyrinth seal fins during rubbing events can be determined by considering a single heat source acting periodically on the surface of a rotating cylinder. Existing literature analysing the temperature distribution on rotating cylindrical bodies due to a stationary heat source is reviewed. The temperature distribution on the circumference of a simplified labyrinth seal fin is calculated using an available and easy to implement analytical approach. A finite element model of the simplified labyrinth seal fin is created and the numerical results are compared to the analytical results. The temperature distributions calculated by the analytical and the numerical approaches coincide for low sliding velocities, while there are discrepancies of the calculated maximum temperatures for higher sliding velocities. The use of the analytical approach allows the conservative estimation of the maximum temperatures arising in labyrinth seal fins during rubbing events. At the same time, high calculation costs can be avoided.

Heat Transfer and Cooling Techniques at Low Temperature

CERN Document Server

Baudouy, B

2014-07-17

The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.

Heat Transfer and Cooling Techniques at Low Temperature

Energy Technology Data Exchange (ETDEWEB)

Baudouy, B [Saclay (France)

2014-07-01

The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.

Heat transfer coefficient: Medivance Arctic Sun Temperature Management System vs. water immersion.

Science.gov (United States)

English, M J; Hemmerling, T M

2008-07-01

To improve heat transfer, the Medivance Arctic Sun Temperature Management System (Medivance, Inc., Louisville, CO, USA) features an adhesive, water-conditioned, highly conductive hydrogel pad for intimate skin contact. This study measured and compared the heat transfer coefficient (h), i.e. heat transfer efficiency, of this pad (hPAD), in a heated model and in nine volunteers' thighs; and of 10 degrees C water (hWATER) in 33 head-out immersions by 11 volunteers. Volunteer studies had ethical approval and written informed consent. Calibrated heat flux transducers measured heat flux (W m-2). Temperature gradient (DeltaT) was measured between skin and pad or water temperatures. Temperature gradient was changed through the pad's water temperature controller or by skin cooling on immersion. The heat transfer coefficient is the slope of W m-2/DeltaT: its unit is W m-2 degrees C-1. Average with (95% CI) was: model, hPAD = 110.4 (107.8-113.1), R2 = 0.99, n = 45; volunteers, hPAD = 109.8 (95.5-124.1), R2 = 0.83, n = 51; and water immersion, hWATER = 107.1 (98.1-116), R2 = 0.86, n = 94. The heat transfer coefficient for the pad was the same in the model and volunteers, and equivalent to hWATER. Therefore, for the same DeltaT and heat transfer area, the Arctic Sun's heat transfer rate would equal water immersion. This has important implications for body cooling/rewarming rates.

Water temperature, body mass and fasting heat production of pacu (Piaractus mesopotamicus).

Science.gov (United States)

Aguilar, Fredy A A; Cruz, Thaline M P DA; Mourão, Gerson B; Cyrino, José Eurico P

2017-01-01

Knowledge on fasting heat production (HEf) of fish is key to develop bioenergetics models thus improving feeding management of farmed species. The core of knowledge on HEf of farmed, neotropical fish is scarce. This study assessed the effect of body mass and water temperature on standard metabolism and fasting heat production of pacu, Piaractus mesopotamicus, an omnivore, Neotropical fresh water characin important for farming and fisheries industries all through South American continent. An automated, intermittent flow respirometry system was used to measure standard metabolic rate (SMR) of pacu (17 - 1,050 g) at five water temperatures: 19, 23, 26, 29 and 33 °C. Mass specific SMR increased with increasing water temperature but decreased as function of body mass. The allometric exponent for scaling HEf was 0.788, and lied in the range recorded for all studied warm-water fish. The recorded van't Hoff factor (Q10) for pacu (2.06) shows the species low response to temperature increases. The model HEf = 0.04643×W0.7882×T1.837 allows to predict HEf (kJ d-1) from body mass (W, kg) and water temperature (T, °C), and can be used in bioenergetical models for the species.

Water temperature, body mass and fasting heat production of pacu (Piaractus mesopotamicus

Directory of Open Access Journals (Sweden)

FREDY A.A. AGUILAR

Full Text Available ABSTRACT Knowledge on fasting heat production (HEf of fish is key to develop bioenergetics models thus improving feeding management of farmed species. The core of knowledge on HEf of farmed, neotropical fish is scarce. This study assessed the effect of body mass and water temperature on standard metabolism and fasting heat production of pacu, Piaractus mesopotamicus, an omnivore, Neotropical fresh water characin important for farming and fisheries industries all through South American continent. An automated, intermittent flow respirometry system was used to measure standard metabolic rate (SMR of pacu (17 - 1,050 g at five water temperatures: 19, 23, 26, 29 and 33 °C. Mass specific SMR increased with increasing water temperature but decreased as function of body mass. The allometric exponent for scaling HEf was 0.788, and lied in the range recorded for all studied warm-water fish. The recorded van't Hoff factor (Q10 for pacu (2.06 shows the species low response to temperature increases. The model HEf = 0.04643×W0.7882×T1.837 allows to predict HEf (kJ d-1 from body mass (W, kg and water temperature (T, °C, and can be used in bioenergetical models for the species.

Optimization and Thermoeconomics Research of a Large Reclaimed Water Source Heat Pump System

Directory of Open Access Journals (Sweden)

Zi-ping Zhang

2013-01-01

Full Text Available This work describes a large reclaimed water source heat pump system (RWSHPS and elaborates on the composition of the system and its design principles. According to the characteristics of the reclaimed water and taking into account the initial investment, the project is divided into two stages: the first stage adopts distributed heat pump heating system and the second adopts the combination of centralized and decentralized systems. We analyze the heating capacity of the RWSHPS, when the phase II project is completed, the system can provide hydronic heating water with the supply and return water temperature of 55°C/15°C and meet the hydronic heating demand of 8 million square meters of residential buildings. We make a thermal economics analysis by using Thermal Economics theory on RWSHPS and gas boiler system, it is known that the RWSHPS has more advantages, compared with the gas boiler heating system; both its thermal efficiency and economic efficiency are relatively high. It provides a reference for future applications of the RWSHPS.

A Comparative Cycle and Refrigerant Simulation Procedure Applied on Air-Water Heat Pumps

DEFF Research Database (Denmark)

Mader, Gunda; Palm, Björn; Elmegaard, Brian

2012-01-01

A vapor compression heat pump absorbs heat from the environment at a low temperature level and rejects heat at a high temperature level. The bigger the difference between the two temperature levels the more challenging is it to gain high energy efficiency with a basic cycle layout as found in most...... small capacity heat pump applications today. Many of the applicable refrigerants also reach their technical limits regarding low vapor pressure for very low source temperatures and high discharge temperatures for high sink temperatures. These issues are especially manifest for air-water heat pumps. Many...... alternative cycle setups and refrigerants are known to improve the energy efficiency of a vapor compression cycle and reduce discharge temperatures. However not all of them are feasible for small capacity heat pumps from a cost and complexity point of view. This paper presents a novel numerical approach...

Thermodynamic analysis of vapor compression heat pump cycle for tap water heating and development of CO_2 heat pump water heater for residential use

International Nuclear Information System (INIS)

Saikawa, Michiyuki; Koyama, Shigeru

2016-01-01

Highlights: • The ideal vapor compression cycle for tap water heating and its COP were defined. • It was verified theoretically that CO_2 achieves the highest COP for tap water heating. • The prototype of CO_2 heat pump water heater for residential use was developed. • Further COP improvement of CO_2 heat pump water heater was estimated. - Abstract: The ideal vapor compression cycle for tap water heating and its coefficient of performance (COP) have been studied theoretically at first. The ideal cycle is defined as the cycle whose high temperature heat source varies temperature with constant specific heat and other processes are same as the reverse Carnot cycle. The COP upper limit of single stage compression heat pump cycle for tap water heating with various refrigerants such as fluorocarbons and natural refrigerants was calculated. The refrigerant which achieves the highest COP for supplying hot water is CO_2. Next, the prototype of CO_2 heat pump water heater for residential use has been developed. Its outline and experimental results are described. Finally its further possibility of COP improvement has been studied. The COP considered a limit from a technical point of view was estimated about 6.0 at the Japanese shoulder season (spring and autumn) test condition of heating water from 17 °C to 65 °C at 16 °C heat source air temperature (dry bulb)/12 °C (wet bulb).

Low temperature humidification dehumidification desalination process

International Nuclear Information System (INIS)

Al-Enezi, Ghazi; Ettouney, Hisham; Fawzy, Nagla

2006-01-01

The humidification dehumidification desalination process is viewed as a promising technique for small capacity production plants. The process has several attractive features, which include operation at low temperature, ability to utilize sustainable energy sources, i.e. solar and geothermal, and requirements of low technology level. This paper evaluates the characteristics of the humidification dehumidification desalination process as a function of operating conditions. A small capacity experimental system is used to evaluate the process characteristics as a function of the flow rate of the water and air streams, the temperature of the water stream and the temperature of the cooling water stream. The experimental system includes a packed humidification column, a double pipe glass condenser, a constant temperature water circulation tank and a chiller for cooling water. The water production is found to depend strongly on the hot water temperature. Also, the water production is found to increase upon the increase of the air flow rate and the decrease of the cooling water temperature. The measured air and water temperatures, air relative humidity and the flow rates are used to calculate the air side mass transfer coefficient and the overall heat transfer coefficient. Measured data are found to be consistent with previous literature results

Development of two-stage compression heat pump for hot water supply in commercial use. Establishment of design method for water and air heat source system; Gyomuyo nidan asshukushiki kyuto heat pump no kaihatsu. Suinetguen oyobi kuki netsugen sytem no sekkei hoho no kakuritsu

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, H; Hashimoto, K; Saikawa, M; Iwatsubo, T; Mimaki, T [Central Research Institute of Electric Power Industry, Tokyo (Japan)

1996-07-01

The two-stage compression cascade heating heat pump cycle was devised for hot water supply in business use such as hotel and store use which allows hot water supply less in primary energy consumption than gas boilers, and higher in temperature than conventional heat pumps. This cycle heats water in cascade manner by two-stage compression using two compressors in both low- and high-stage refrigerant circuits, and two condensers different in condensation temperature (intermediate heat exchanger and condenser) to achieve higher hot water temperature and higher COP. For cost reduction, the new system design method was established which is possible to cope with conventional compressors such as screw and scroll ones with different theoretical suction volume for every one. System design parameters such as thermal output and COP of hot water supply were largely affected by theoretical suction volume ratio of low- and high-stage compressors dependent on combination of the compressors, and refrigerant condensing temperature in an intermediate heat exchanger as proper parameter. 4 refs., 17 figs., 13 tabs.

Influence of ambient temperatures on performance of a CO2 heat pump water heating system

International Nuclear Information System (INIS)

Yokoyama, Ryohei; Shimizu, Takeshi; Ito, Koichi; Takemura, Kazuhisa

2007-01-01

In residential applications, an air-to-water CO 2 heat pump is used in combination with a domestic hot water storage tank, and the performance of this system is affected significantly not only by instantaneous ambient air and city water temperatures but also by hourly changes of domestic hot water consumption and temperature distribution in the storage tank. In this paper, the performance of a CO 2 heat pump water heating system is analyzed by numerical simulation. A simulation model is created based on thermodynamic equations, and the values of model parameters are estimated based on measured data for existing devices. The calculated performance is compared with the measured one, and the simulation model is validated. The system performance is clarified in consideration of seasonal changes of ambient air and city water temperatures

High temperature absorption compression heat pump for industrial waste heat

DEFF Research Database (Denmark)

Reinholdt, Lars; Horntvedt, B.; Nordtvedt, S. R.

2016-01-01

Heat pumps are currently receiving extensive interest because they may be able to support the integration of large shares of fluctuating electricity production based on renewable sources, and they have the potential for the utilization of low temperature waste heat from industry. In most industries......, the needed temperature levels often range from 100°C and up, but until now, it has been quite difficult to find heat pump technologies that reach this level, and thereby opening up the large-scale heat recovery in the industry. Absorption compression heat pumps can reach temperatures above 100°C......, and they have proved themselves a very efficient and reliable technology for applications that have large temperature changes on the heat sink and/or heat source. The concept of Carnot and Lorenz efficiency and its use in the analysis of system integration is shown. A 1.25 MW system having a Carnot efficiency...

Shallow Groundwater Temperatures and the Urban Heat Island Effect: the First U.K City-wide Geothermal Map to Support Development of Ground Source Heating Systems Strategy

Science.gov (United States)

Patton, Ashley M.; Farr, Gareth J.; Boon, David P.; James, David R.; Williams, Bernard; Newell, Andrew J.

2015-04-01

The first UK city-wide heat map is described based on measurements of groundwater from a shallow superficial aquifer in the coastal city of Cardiff, Wales, UK. The UK Government has a target of reducing greenhouse gas emissions by 80% by 2050 (Climate Change Act 2008) and low carbon technologies are key to achieving this. To support the use of ground source heating we characterised the shallow heat potential of an urban aquifer to produce a baseline dataset which is intended to be used as a tool to inform developers and to underpin planning and regulation. We exploited an existing network of 168 groundwater monitoring boreholes across the city, recording the water temperature in each borehole at 1m depth intervals up to a depth of 20m. We recorded groundwater temperatures during the coldest part of 2014, and repeat profiling of the boreholes in different seasons has added a fourth dimension to our results and allowed us to characterise the maximum depth of seasonal temperature fluctuation. The temperature profiles were used to create a 3D model of heat potential within the aquifer using GOCAD® and the average borehole temperatures were contoured using Surfer® 10 to generate a 2D thermal resource map to support future assessment of urban Ground Source Heat Pumps prospectively. The average groundwater temperature in Cardiff was found to be above the average for England and Wales (11.3°C) with 90% of boreholes in excess of this figure by up to 4°C. The subsurface temperature profiles were also found to be higher than forecast by the predicted geothermal gradient for the area. Potential sources for heat include: conduction from buildings, basements and sub-surface infrastructure; insulation effects of the urban area and of the geology, and convection from leaking sewers. Other factors include recharge inhibition by drains, localised confinement and rock-water interaction in specific geology. It is likely to be a combination of multiple factors which we are hoping

Consumer Unit for Low Energy District Heating Net

DEFF Research Database (Denmark)

Paulsen, Otto; Fan, Jianhua; Furbo, Simon

2008-01-01

to reduce heat loss in the network. The consumer’s installation is a unit type with an accumulation tank for smoothing the heat load related to the domestic hot water. The building heat load is delivered by an under-floor heating system. The heavy under-floor heating system is assumed to smooth the room...... heat load on a daily basis, having a flow temperature control based on outdoor climate. The unit is designed for a near constant district heating water flow. The paper describes two concepts. The analyses are based on TRNSYS (Klein et al., 2006) simulation, supplied with laboratory verification......A low energy/ low temperature consumer installation is designed and analyzed. The consumer type is a low energy single family house 145 m2 with annual energy consumption in the range of 7000 kWh, incl. domestic hot water in a 2800 degree day climate. The network is an extreme low temperature system...

A combined power cycle utilizing low-temperature waste heat and LNG cold energy

International Nuclear Information System (INIS)

Shi Xiaojun; Che Defu

2009-01-01

This paper has proposed a combined power system, in which low-temperature waste heat can be efficiently recovered and cold energy of liquefied natural gas (LNG) can be fully utilized as well. This system consists of an ammonia-water mixture Rankine cycle and an LNG power generation cycle, and it is modelled by considering mass, energy and species balances for every component and thermodynamic analyses are conducted. The results show that the proposed combined cycle has good performance, with net electrical efficiency and exergy efficiency of 33% and 48%, respectively, for a typical operating condition. The power output is equal to 1.25 MWh per kg of ammonia-water mixture. About 0.2 MW of electrical power for operating sea water pumps can be saved. Parametric analyses are performed for the proposed combined cycle to evaluate the effects of key factors on the performance of the proposed combined cycle through simulation calculations. Results show that a maximum net electrical efficiency can be obtained as the inlet pressure of ammonia turbine increases and the peak value increases as the ammonia mass fraction increases. Exergy efficiency goes up with the increased ammonia turbine inlet pressure. With the ammonia mass fraction increases, the net electrical efficiency increases, whereas exergy efficiency decreases. For increasing LNG turbine inlet pressure or heat source temperature, there is also a peak of net electrical efficiency and exergy efficiency. With the increase of LNG gas turbine outlet pressure, exergy efficiency increases while net electrical efficiency drops

Analysis of Low-Temperature Utilization of Geothermal Resources

Energy Technology Data Exchange (ETDEWEB)

Anderson, Brian

2015-06-30

Full realization of the potential of what might be considered “low-grade” geothermal resources will require that we examine many more uses for the heat than traditional electricity generation. To demonstrate that geothermal energy truly has the potential to be a national energy source we will be designing, assessing, and evaluating innovative uses for geothermal-produced water such as hybrid biomass-geothermal cogeneration of electricity and district heating and efficiency improvements to the use of cellulosic biomass in addition to utilization of geothermal in district heating for community redevelopment projects. The objectives of this project were: 1) to perform a techno-economic analysis of the integration and utilization potential of low-temperature geothermal sources. Innovative uses of low-enthalpy geothermal water were designed and examined for their ability to offset fossil fuels and decrease CO2 emissions. 2) To perform process optimizations and economic analyses of processes that can utilize low-temperature geothermal fluids. These processes included electricity generation using biomass and district heating systems. 3) To scale up and generalize the results of three case study locations to develop a regionalized model of the utilization of low-temperature geothermal resources. A national-level, GIS-based, low-temperature geothermal resource supply model was developed and used to develop a series of national supply curves. We performed an in-depth analysis of the low-temperature geothermal resources that dominate the eastern half of the United States. The final products of this study include 17 publications, an updated version of the cost estimation software GEOPHIRES, and direct-use supply curves for low-temperature utilization of geothermal resources. The supply curves for direct use geothermal include utilization from known hydrothermal, undiscovered hydrothermal, and near-hydrothermal EGS resources and presented these results at the Stanford

Simulation of a combined heating, cooling and domestic hot water system based on ground source absorption heat pump

International Nuclear Information System (INIS)

Wu, Wei; You, Tian; Wang, Baolong; Shi, Wenxing; Li, Xianting

2014-01-01

Highlights: • A combined heating/cooling/DHW system based on GSAHP is proposed in cold regions. • The soil imbalance is effectively reduced and soil temperature can be kept stable. • 20% and 15% of condensation/absorption heat is recovered by GSAHP to produce DHW. • The combined system can improve the primary energy efficiency by 23.6% and 44.4%. - Abstract: The amount of energy used for heating and domestic hot water (DHW) is very high and will keep increasing. The conventional ground source electrical heat pump used in heating-dominated buildings has the problems of thermal imbalance, decrease of soil temperature, and deterioration of heating performance. Ground source absorption heat pump (GSAHP) is advantageous in both imbalance reduction and primary energy efficiency (PEE) improvement; however, the imbalance is still unacceptable in the warmer parts of cold regions. A combined heating/cooling/DHW (HCD) system based on GSAHP is proposed to overcome this problem. The GSAHPs using generator absorber heat exchange (GAX) and single-effect (SE) cycles are simulated to obtain the performance under various working conditions. Different HCD systems in Beijing and Shenyang are simulated comparatively in TRNSYS, based on which the thermal imbalance, soil temperature, heat recovery, and energy efficiency are analyzed. Results show that GSAHP–GAX–HCD is suitable for Beijing and GSAHP–SE–HCD is suitable for Shenyang. The imbalance ratio can be reduced to −14.8% in Beijing and to 6.0% in Shenyang with an annual soil temperature variation of only 0.5 °C and 0.1 °C. Furthermore, about 20% and 15% of the total condensation/absorption heat is recovered to produce DHW, and the PEE can reach 1.516 in Beijing and 1.163 in Shenyang. The combined HCD systems can achieve a PEE improvement of 23.6% and 44.4% compared with the normal heating/cooling systems

Heat sources for heat pumps in the energetic and economic comparison

International Nuclear Information System (INIS)

Bockelmann, Franziska; Fisch, M. Norbert; Schlosser, Mathias; Peter, Markus

2016-01-01

Because of the growing application of heat pumps also the number of potentially usable low-temperature heat sources and corresponding heat exchangers for heat-pump systems present in the market increases. Thereby products like energy fences, high-power piles, ore ice reservoir come into applications without any knowledge ab out their power or the cost-profit ratio. The optimized lay-out of the coupling to the building are however essential conditions in order to reach an energy-efficient and durable operation of the facilities. The research project ''future heat pump'' sponsored by the BMWi is dedicated to the energetic and economic evaluation of heat sources for heat pumps. In this connection a pre-check-tool for the preliminary selection of low-temperature heat sources and connected, suitable heat-exchange systems is developed and their actual status of development presented. The holistic, comparing consideration of the different heat sources and heat-exchanger systems is related among others to the power numbers of the heat pumps, the entry and withdrawal services of the heat-exchangers, and the general performance of the systems. Additionally an estimation of economic and ecologic aspects (investment and operation costs, CO_2 emissions) is made. Aim is the determination of the plausibility of applications and essential boundary conditions of single source systems. For the qualitative comparison in a project-accompanying monitoring different facilities and source systems are measurement-technically comprehended.

The structural design of the experimental equipment for unconventional heating water using heat transfer surfaces located in the heat source

Directory of Open Access Journals (Sweden)

Jandačka J.

2013-04-01

Full Text Available Flue gas temperature at throat of most industrially produced fireplaces is around 250 to 350 °C. It's quite interesting thermal potential, which can be even before sucking up the chimney back utilize. One of the potential uses of this device to heat the hot water. Article refers to the structural design of such a device, which works with the transfer of heat through a substance changes phase from liquid to steam in a sealed tube (heat pipe. Benefits of heat pipes is their light weight, the thermal effect of a rapid and low maintenance costs.

The structural design of the experimental equipment for unconventional heating water using heat transfer surfaces located in the heat source

Science.gov (United States)

Kaduchová, K.; Lenhard, R.; Gavlas, S.; Jandačka, J.

2013-04-01

Flue gas temperature at throat of most industrially produced fireplaces is around 250 to 350 °C. It's quite interesting thermal potential, which can be even before sucking up the chimney back utilize. One of the potential uses of this device to heat the hot water. Article refers to the structural design of such a device, which works with the transfer of heat through a substance changes phase from liquid to steam in a sealed tube (heat pipe). Benefits of heat pipes is their light weight, the thermal effect of a rapid and low maintenance costs.

Development of low grade waste heat thermoelectric power generator

Directory of Open Access Journals (Sweden)

Suvit Punnachaiya

2010-07-01

Full Text Available This research aimed to develop a 50 watt thermoelectric power generator using low grade waste heat as a heat source,in order to recover and utilize the excess heat in cooling systems of industrial processes and high activity radioisotope sources. Electricity generation was based on the reverse operation of a thermoelectric cooling (TEC device. The TEC devices weremodified and assembled into a set of thermal cell modules operating at a temperature less than 100°C. The developed powergenerator consisted of 4 modules, each generating 15 watts. Two cascade modules were connected in parallel. Each modulecomprised of 96 TEC devices, which were connected in series. The hot side of each module was mounted on an aluminumheat transfer pipe with dimensions 12.212.250 cm. Heat sinks were installed on the cold side with cooling fans to provideforced air cooling.To test electricity generation in the experiment, water steam was used as a heat source instead of low grade waste heat.The open-circuit direct current (DC of 250 V and the short-circuit current of 1.2 A was achieved with the following operatingconditions: a hot side temperature of 96°C and a temperature difference between the hot and cold sides of 25°C. The DC poweroutput was inverted to an AC power source of 220 V with 50 Hz frequency, which can continuously supply more than 50 wattsof power to a resistive load as long as the heat source was applied to the system. The system achieved an electrical conversionefficiency of about 0.47 percent with the capital cost of 70 US$/W.

Final Report Low-temperature Resource Assessment Program

Energy Technology Data Exchange (ETDEWEB)

Lienau, P.J. [Geo-Heat Center, Oregon Institute of Technology, Klamath Falls, OR (US); Ross, H. [Earth Sciences and Resources Institute, University of Utah

1996-02-01

The U.S. Department of Energy - Geothermal Division (DOE/GD) recently sponsored the Low-Temperature Resource Assessment project to update the inventory of the nation's low- and moderate-temperature geothermal resources and to encourage development of these resources. A database of 8,977 thermal wells and springs that are in the temperature range of 20 degrees Celsius to 150 degrees Celsius has been compiled for ten western states, an impressive increase of 82% compared to the previous assessments. The database includes location, descriptive data, physical parameters, water chemistry and references for sources of data. Computer-generated maps are also available for each state. State Teams have identified 48 high-priority areas for near-term comprehensive resource studies and development. Resources with temperatures greater than 50 degrees Celsius located within 8 km of a population center were identified for 271 collocated cities. Geothermal energy costevaluation software has been developed to quickly identify the cost of geothermally supplied heat to these areas in a fashion similar to that used for conventionally fueled heat sources.

Performance investigation of a novel frost-free air-source heat pump water heater combined with energy storage and dehumidification

International Nuclear Information System (INIS)

Wang, Fenghao; Wang, Zhihua; Zheng, Yuxin; Lin, Zhang; Hao, Pengfei; Huan, Chao; Wang, Tian

2015-01-01

Highlights: • Experiments are carried out to investigate a novel frost-free ASHPWH system. • Dynamic characteristics of the system are studied at different ambient conditions. • Test results confirm the expected potential to control the frost-free process. • The COP increased 17.9% and 3.4% respectively in comparison with RCD at −3 °C and 3 °C. - Abstract: Air-source heat pump (ASHP) often operates with substantial frost formation on the outdoor heat exchanger at low ambient temperature in winter, it insulates the finned surface and also reduces heat transfer rate, leading to performance degradation or even shutdown of ASHP systems. Although several defrosting methods have been reported, the frosting and defrosting processes reduced energy efficiency and resulted in, in some cases, heat pump breakdown. To solve this problem, a novel frost-free air-source heat pump water heater (ASHPWH) system has been developed, which coupled with an extra heat exchanger coated by a solid desiccant (EHECSD) with an energy storage device (ESD). Based on the previous studies, a further analysis and comprehensive research on the novel frost-free ASHPWH system is presented in this paper. The dynamic characteristics of the novel system are investigated experimentally in different ambient conditions. An experimental setup and experimental procedures are described in detail. Thereafter, the dehumidification efficiency and regeneration efficiency of EHECSD, suction and discharge pressures of the compressor, the temperature of PCM are evaluated during the heating and regeneration modes respectively. Results indicate that the system can keep the evaporator frost-free for 32, 34, 36 min during heating mode at the ambient temperatures of −3 °C, 0 °C and 3 °C and 85% RH. Compared with the reverse-cycle defrosting (RCD), COP of the frost-free ASHPWH are 17.9% and 3.4% higher at the ambient temperature of −3 °C and 3 °C respectively. With this innovative technology, it has

Comparison of shell-and-tube with plate heat exchangers for the use in low-temperature organic Rankine cycles

International Nuclear Information System (INIS)

Walraven, Daniël; Laenen, Ben; D’haeseleer, William

2014-01-01

Highlights: • Binary cycles for low-temperature heat sources are investigated. • Shell-and-tube and plate heat exchangers are modeled. • System optimization of the cycle variables and heat exchanger geometry. • ORCs with plate heat exchangers obtain in most cases higher efficiencies. - Abstract: Organic Rankine cycles (ORCs) can be used for electricity production from low-temperature heat sources. These ORCs are often designed based on experience, but this experience will not always lead to the most optimal configuration. The ultimate goal is to design ORCs by performing a system optimization. In such an optimization, the configuration of the components and the cycle parameters (temperatures, pressures, mass flow rate) are optimized together to obtain the optimal configuration of power plant and components. In this paper, the configuration of plate heat exchangers or shell-and-tube heat exchangers is optimized together with the cycle configuration. In this way every heat exchanger has the optimum allocation of heat exchanger surface, pressure drop and pinch-point-temperature difference for the given boundary conditions. ORCs with plate heat exchangers perform mostly better than ORCs with shell-and-tube heat exchangers, but one disadvantage of plate heat exchangers is that the geometry of both sides is the same, which can result in an inefficient heat exchanger. It is also shown that especially the cooling-fluid inlet temperature and mass flow have a strong influence on the performance of the power plant

District Heating Expansion Potential with Low-Temperature and End-Use Heat Savings

DEFF Research Database (Denmark)

Nielsen, Steffen; Grundahl, Lars

2018-01-01

District heating has the potential to play a key role in the transition towards a renewable energy system. However, the development towards reduced heat demands threatens the feasibility of district heating. Despite this challenge, opportunity exists in the form of fourth generation district...... heating, which operates at lower temperatures and enables better renewable integration. This article investigates this challenge by examining the district heating potential within three scenarios: The first is a reference scenario with current heat demand and temperatures, the second includes heat demand...... costs. The models are applied using an example case of The Northern Region of Denmark. The article concludes that the district heating potential is highest in the reference scenario. When heat savings are introduced, district heating expansions, in most cases, will not be feasible. Introducing low...

Analysis of a carbon dioxide transcritical power cycle using a low temperature source

International Nuclear Information System (INIS)

Cayer, Emmanuel; Galanis, Nicolas; Desilets, Martin; Nesreddine, Hakim; Roy, Philippe

2009-01-01

A detailed analysis of a carbon dioxide transcritical power cycle using an industrial low-grade stream of process gases as its heat source is presented. The methodology is divided in four steps: energy analysis, exergy analysis, finite size thermodynamics and calculation of the heat exchangers' surface. The results have been calculated for fixed temperature and mass flow rate of the heat source, fixed maximum and minimum temperatures in the cycle and a fixed sink temperature by varying the high pressure of the cycle and its net power output. The main results show the existence of an optimum high pressure for each of the four steps; in the first two steps, the optimum pressure maximises the thermal or exergetic efficiency while in the last two steps it minimises the product UA or the heat exchangers' surface. These high pressures are very similar for the energy and exergy analyses. The last two steps also have nearly identical optimizing high pressures that are significantly lower that the ones for the first two steps. In addition, the results show that the augmentation of the net power output produced from the limited energy source has no influence on the results of the energy analysis, decreases the exergetic efficiency and increases the heat exchangers' surface. Changing the net power output has no significant impact on the high pressures optimizing each of the four steps

Synergistic effect of solar radiation and solar heating to disinfect drinking water sources.

Science.gov (United States)

Rijal, G K; Fujioka, R S

2001-01-01

Waterborne diseases are still common in developing countries as drinking water sources are contaminated and feasible means to reliably treat and disinfect these waters are not available. Many of these developing countries are in the tropical regions of the world where sunlight is plentiful. The objective of this study was to evaluate the effectiveness of combining solar radiation and solar heating to disinfect contaminated water using a modified Family Sol*Saver System (FSP). The non-UV transmittable cover sheet of the former FSP system was replaced with an UV transmittable plastic cover sheet to enable more wavelengths of sunlight to treat the water. Disinfection efficiency of both systems was evaluated based on reduction of the natural populations of faecal coliform, E. coli, enterococci, C. perfringens, total heterotrophic bacteria, hydrogen sulphide producing bacteria and FRNA virus. The results showed that under sunny and partly sunny conditions, water was heated to critical temperature (60 degrees C) in both the FSP systems inactivating more than 3 log (99.9%) of the concentrations of faecal coliform and E. coli to undetectable levels of heat worked synergistically to enhance the inactivation of faecal indicator bacteria. The relative log removal of indicator microorganism in the FSP treated water was total heterotrophic bacteria heat and radiation effects of sunlight were important in disinfecting water by solar units. The data indicated that direct radiation of sunlight worked synergistically with solar heating of the water to disinfect the water. Thus, effective disinfection was observed even when the water temperature did not reach 60 degrees C. Finally, the hydrogen sulphide test is a simple and reliable test that householders can use to determine whether their water had been sufficiently disinfected.

A simulation study on the operating performance of a solar-air source heat pump water heater

International Nuclear Information System (INIS)

Xu Guoying; Zhang Xiaosong; Deng Shiming

2006-01-01

A simulation study on the operating performance of a new type of solar-air source heat pump water heater (SAS-HPWH) has been presented. The SAS-HPWH used a specially designed flat-plate heat collector/evaporator with spiral-finned tubes to obtain energy from both solar irradiation and ambient air for hot water heating. Using the meteorological data in Nanjing, China, the simulation results based on 150 L water heating capacity showed that such a SAS-HPWH can heat water up to 55 deg. C efficiently under various weather conditions all year around. In this simulation study, the influences of solar radiation, ambient temperature and compressor capacity on the performance of the SAS-HPWH were analyzed. In order to improve the overall operating performance, the use of a variable-capacity compressor has been proposed

Optimal operating conditions of a transcritical endoreversible cycle using a low enthalpy heat source

International Nuclear Information System (INIS)

Rachedi, Malika; Feidt, Michel; Amirat, Madjid; Merzouk, Mustapha

2016-01-01

Highlights: • Thermodynamics analysis of a finite size heat engine driven by a finite heat source. • Mathematical modelling of a transcritical endoreversible organic Rankine cycle. • Parametric study of the optimum operating conditions of transcritical cycle. • Choice of appropriate parameters could lead to very promising efficiencies. - Abstract: In the context of thermodynamic analysis of finite dimensions systems, we studied the optimum operating conditions of an endoreversible thermal machine. In this study, we considered a transcritical cycle, considering external irreversibilities. The hot reservoir is a low enthalpy geothermal heat source; therefore, it is assumed to be finite, whereas the cold reservoir is assumed to be infinite. The power optimisation is investigated by searching the optimum effectiveness of the heat-exchanger at the hot side of the engine. The sum of the total effectiveness and the second law of thermodynamics are used as constraints for optimisation. The optimal temperatures of the working fluid and optimum performances are evaluated based on the most significant parameters of the system: (1) the ratio of heat capacity rate of the working fluid to the heat capacity rate of the coolant and (2) the ratio of the sink temperature to the temperature of the hot source. The parametric study of the cycle and its approximation by a trilateral cycle enabled us to determine the optimum value of the effectiveness of the heat exchangers and the optimal operating temperatures of the cycle considered. The efficiencies obtained are in the range of 15–25% and was found to exceed the efficiency expected by the Curzon and Ahlborn prevision; meanwhile, the Carnot efficiency remains at a high limit.

Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers

Energy Technology Data Exchange (ETDEWEB)

Edward Levy; Harun Bilirgen; John DuPoint

2011-03-31

Most of the water used in a thermoelectric power plant is used for cooling, and DOE has been focusing on possible techniques to reduce the amount of fresh water needed for cooling. DOE has also been placing emphasis on recovery of usable water from sources not generally considered, such as mine water, water produced from oil and gas extraction, and water contained in boiler flue gas. This report deals with development of condensing heat exchanger technology for recovering moisture from flue gas from coal-fired power plants. The report describes: (1) An expanded data base on water and acid condensation characteristics of condensing heat exchangers in coal-fired units. This data base was generated by performing slip stream tests at a power plant with high sulfur bituminous coal and a wet FGD scrubber and at a power plant firing high-moisture, low rank coals. (2) Data on typical concentrations of HCl, HNO{sub 3} and H{sub 2}SO{sub 4} in low temperature condensed flue gas moisture, and mercury capture efficiencies as functions of process conditions in power plant field tests. (3) Theoretical predictions for sulfuric acid concentrations on tube surfaces at temperatures above the water vapor dewpoint temperature and below the sulfuric acid dew point temperature. (4) Data on corrosion rates of candidate heat exchanger tube materials for the different regions of the heat exchanger system as functions of acid concentration and temperature. (5) Data on effectiveness of acid traps in reducing sulfuric acid concentrations in a heat exchanger tube bundle. (6) Condensed flue gas water treatment needs and costs. (7) Condensing heat exchanger designs and installed capital costs for full-scale applications, both for installation immediately downstream of an ESP or baghouse and for installation downstream of a wet SO{sub 2} scrubber. (8) Results of cost-benefit studies of condensing heat exchangers.

Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers

Energy Technology Data Exchange (ETDEWEB)

Levy, Edward; Bilirgen, Harun; DuPont, John

2011-03-31

Most of the water used in a thermoelectric power plant is used for cooling, and DOE has been focusing on possible techniques to reduce the amount of fresh water needed for cooling. DOE has also been placing emphasis on recovery of usable water from sources not generally considered, such as mine water, water produced from oil and gas extraction, and water contained in boiler flue gas. This report deals with development of condensing heat exchanger technology for recovering moisture from flue gas from coal-fired power plants. The report describes: • An expanded data base on water and acid condensation characteristics of condensing heat exchangers in coal-fired units. This data base was generated by performing slip stream tests at a power plant with high sulfur bituminous coal and a wet FGD scrubber and at a power plant firing highmoisture, low rank coals. • Data on typical concentrations of HCl, HNO{sub 3} and H{sub 2}SO{sub 4} in low temperature condensed flue gas moisture, and mercury capture efficiencies as functions of process conditions in power plant field tests. • Theoretical predictions for sulfuric acid concentrations on tube surfaces at temperatures above the water vapor dewpoint temperature and below the sulfuric acid dew point temperature. • Data on corrosion rates of candidate heat exchanger tube materials for the different regions of the heat exchanger system as functions of acid concentration and temperature. • Data on effectiveness of acid traps in reducing sulfuric acid concentrations in a heat exchanger tube bundle. • Condensed flue gas water treatment needs and costs. • Condensing heat exchanger designs and installed capital costs for full-scale applications, both for installation immediately downstream of an ESP or baghouse and for installation downstream of a wet SO{sub 2} scrubber. • Results of cost-benefit studies of condensing heat exchangers.

Residential CO{sub 2} heat pump system for combined space heating and hot water heating

Energy Technology Data Exchange (ETDEWEB)

Stene, Joern

2004-02-01

Carbon dioxide (CO{sub 2}, R-744) has been identified as a promising alternative to conventional working fluids in a number of applications due to its favourable environmental and thermophysical properties. Previous work on residential CO{sub 2} heat pumps has been dealing with systems for either space heating or hot water heating, and it was therefore considered interesting to carry out a theoretical and experimental study of residential CO{sub 2} heat pump systems for combined space heating and hot water heating - o-called integrated CO{sub 2} heat pump systems. The scope of this thesis is limited to brine-to-water and water-to-water heat pumps connected to low-temperature hydronic space heating systems. The main conclusions are: (1) Under certain conditions residential CO{sub 2} heat pump systems for combined space heating and hot water heating may achieve the same or higher seasonal performance factor (SPF) than the most energy efficient state-of-the-art brine-to-water heat pumps. (2) In contrary to conventional heat pump systems for combined space heating and DHW heating, the integrated CO{sub 2} heat pump system achieves the highest COP in the combined heating mode and the DHW heating mode, and the lowest COP in the space heating mode. Hence, the larger the annual DHW heating demand, the higher the SPF of the integrated CO{sub 2} heat pump system. (3) The lower the return temperature in the space heating system and the lower the DHW storage temperature, the higher the COP of the integrated CO{sub 2} heat pump. A low return temperature in the space heating system also results in a moderate DHW heating capacity ratio, which means that a relatively large part of the annual space heating demand can be covered by operation in the combined heating mode, where the COP is considerably higher than in the space heating mode. (4) During operation in the combined heating mode and the DHW heating mode, the COP of the integrated CO{sub 2} heat pump is heavily influenced by

Low-temperature waste-heat recovery in the food and paper industries

Energy Technology Data Exchange (ETDEWEB)

Foell, W.K.; Lund, D.; Mitchell, J.W.; Ray, D.; Stevenson, R.; TenWolde, A.

1980-11-01

The potential of low-temperature waste-heat recovery technology is examined. An examination of barriers to impede waste-heat recovery is made and research programs are identified. Extensive information and data are presented in the following chapters: Waste Heat Recovery in the Wisconsin Food Industry; Waste Heat Recovery in the Wisconsin Pulp and Paper Industry; Industries' Economic Analysis of Energy Conservation Projects; Industrial Waste Heat Recovery (selection of heat-recovery heat exchangers for industrial applications, simplified procedure for selection of heat recovery heat exchangers for industrial applications, selection of heat pumps for industrial applications); Institutional Aspects of Industrial Energy Conservation (economic motivation for energy conservation and the industrial response, intrafirm idea channels and their sources, evaluation and approval of plant improvement projects, reported barriers to adopting waste heat recovery projects and recommendations for government involvement, and the final chapter is a summary with major conclusions given. Additional information is given in two appendices on the potential waste heat recovery in a cheese plant (calculation) and conditions for optimum exchanger size and break-even fuel cost. (MCW)

Geothermal heat pumps - Trends and comparisons

Energy Technology Data Exchange (ETDEWEB)

Lund, John W

1989-01-01

Heat pumps are used where geothermal water or ground temperatures are only slightly above normal, generally 50 to 90 deg. F. Conventional geothermal heating (and cooling) systems are not economically efficient at these temperatures. Heat pumps, at these temperatures, can provide space heating and cooling, and with a desuperheater, domestic hot water. Two basic heat pump systems are available, air-source and water- or ground-source. Water- and ground-coupled heat pumps, referred to as geothermal heat pumps (GHP), have several advantages over air-source heat pumps. These are: (1) they consume about 33% less annual energy, (2) they tap the earth or groundwater, a more stable energy source than air, (3) they do not require supplemental heat during extreme high or low outside temperatures, (4) they use less refrigerant (freon), and (5) they have a simpler design and consequently less maintenance.

The influence of heat sink temperature on the seasonal efficiency of shallow geothermal heat pumps

Science.gov (United States)

Pełka, Grzegorz; Luboń, Wojciech; Sowiżdżał, Anna; Malik, Daniel

2017-11-01

Geothermal heat pumps, also known as ground source heat pumps (GSHP), are the most efficient heating and cooling technology utilized nowadays. In the AGH-UST Educational and Research Laboratory of Renewable Energy Sources and Energy Saving in Miękinia, shallow geothermal heat is utilized for heating. In the article, the seasonal efficiency of two geothermal heat pump systems are described during the 2014/2015 heating season, defined as the period between 1st October 2014 and 30th April 2015. The first system has 10.9 kW heating capacity (according to European Standard EN 14511 B0W35) and extracts heat from three vertical geothermal loops at a depth of 80m each. During the heating season, tests warmed up the buffer to 40°C. The second system has a 17.03 kW heating capacity and extracts heat from three vertical geothermal loops at a depth of 100 m each, and the temperature of the buffer was 50°C. During the entire heating season, the water temperatures of the buffers was constant. Seasonal performance factors were calculated, defined as the quotient of heat delivered by a heat pump to the system and the sum of electricity consumed by the compressor, source pump, sink pump and controller of heat pumps. The measurements and calculations give the following results: - The first system was supplied with 13 857 kWh/a of heat and consumed 3 388 kWh/a electricity. The SPF was 4.09 and the average temperature of outlet water from heat pump was 40.8°C, and the average temperature of brine flows into the evaporator was 3.7 °C; - The second system was supplied with 12 545 kWh/a of heat and consumed 3 874 kWh/a electricity. The SPF was 3.24 and the average temperature of outlet water from heat pump was 51.6°C, and the average temperature of brine flows into the evaporator was 5.3°C. To summarize, the data shown above presents the real SPF of the two systems. It will be significant in helping to predict the SPF of objects which will be equipped with ground source heat pumps.

Low order modelling and closed-loop thermal control of a ventilated plate subject to a heat source disturbance

International Nuclear Information System (INIS)

Videcoq, E; Girault, M; Petit, D

2012-01-01

A multi-input multi-output (MIMO) thermal control problem in real-time is investigated. An aluminum slab is heated on one side by a radiative heat source and cooled on the other side by a fan panel. Starting from a nominal steady state configuration of heat source power and ventilation level, the objective is to control temperature at 4 chosen locations on the rear side when the thermal system is subject to a perturbation: the heat source power. The 4 actuators are the ventilation levels of 4 fans. The hypothesis of small inputs and temperature responses deviations is made, resulting in the assumption of a linear control problem. The originality of this work is twofold: (i) instead of a (large-sized) classical heat transfer model built from spatial discretization of local partial differential equations governing physics over the system domain, a low order model is identified from experimental data using the Modal Identification Method, (ii) this low order model is used to perform state feedback control in real time through a Linear Quadratic Gaussian (LQG) compensator.

Advanced Energy and Water Recovery Technology from Low Grade Waste Heat

Energy Technology Data Exchange (ETDEWEB)

Dexin Wang

2011-12-19

The project has developed a nanoporous membrane based water vapor separation technology that can be used for recovering energy and water from low-temperature industrial waste gas streams with high moisture contents. This kind of exhaust stream is widely present in many industrial processes including the forest products and paper industry, food industry, chemical industry, cement industry, metal industry, and petroleum industry. The technology can recover not only the sensible heat but also high-purity water along with its considerable latent heat. Waste heats from such streams are considered very difficult to recover by conventional technology because of poor heat transfer performance of heat-exchanger type equipment at low temperature and moisture-related corrosion issues. During the one-year Concept Definition stage of the project, the goal was to prove the concept and technology in the laboratory and identify any issues that need to be addressed in future development of this technology. In this project, computational modeling and simulation have been conducted to investigate the performance of a nanoporous material based technology, transport membrane condenser (TMC), for waste heat and water recovery from low grade industrial flue gases. A series of theoretical and computational analyses have provided insight and support in advanced TMC design and experiments. Experimental study revealed condensation and convection through the porous membrane bundle was greatly improved over an impermeable tube bundle, because of the membrane capillary condensation mechanism and the continuous evacuation of the condensate film or droplets through the membrane pores. Convection Nusselt number in flue gas side for the porous membrane tube bundle is 50% to 80% higher than those for the impermeable stainless steel tube bundle. The condensation rates for the porous membrane tube bundle also increase 60% to 80%. Parametric study for the porous membrane tube bundle heat transfer

Development of an Air-Source Heat Pump Integrated with a Water Heating / Dehumidification Module

Energy Technology Data Exchange (ETDEWEB)

Rice, C Keith [ORNL; Uselton, Robert B. [Lennox Industries, Inc; Shen, Bo [ORNL; Baxter, Van D [ORNL; Shrestha, Som S [ORNL

2014-01-01

A residential-sized dual air-source integrated heat pump (AS-IHP) concept is under development in partnership between ORNL and a manufacturer. The concept design consists of a two-stage air-source heat pump (ASHP) coupled on the air distribution side with a separate novel water heating/dehumidification (WH/DH) module. The motivation for this unusual equipment combination is the forecast trend for home sensible loads to be reduced more than latent loads. Integration of water heating with a space dehumidification cycle addresses humidity control while performing double-duty. This approach can be applied to retrofit/upgrade applications as well as new construction. A WH/DH module capable of ~1.47 L/h water removal and ~2 kW water heating capacity was assembled by the manufacturer. A heat pump system model was used to guide the controls design; lab testing was conducted and used to calibrate the models. Performance maps were generated and used in a TRNSYS sub-hourly simulation to predict annual performance in a well-insulated house. Annual HVAC/WH energy savings of ~35% are predicted in cold and hot-humid U.S. climates compared to a minimum efficiency baseline.

Low temperature industrial waste heat utilization in the area 'Speyer-Ludwigshafen-Frankenthal-Worms'

International Nuclear Information System (INIS)

Nunold, K.; Krebs, A.

1982-01-01

The aim of the study is the elaboration of reliable facts whether and under which conditions low temperature industrial waste heat systems can be economically utilized for heating purposes. The source of the waste heat are power- and industrial plants. In order to obtain reliable results, investigations have been carried out in the area Speyer-Ludwigshafen-Frankenthal and Worms. These investigations showed a number of application possibilities for heat pumps and it became moreover evident that there is a high variaiton of the heat requirement due to social components and the different type of building structures of the consumers. The economic results showed that the application of this heating system can under certain conditions supplement resp. replace other heating systems. (orig.) [de

Performance of ultra low temperature district heating systems with utility plant and booster heat pumps

DEFF Research Database (Denmark)

Ommen, Torben Schmidt; Thorsen, Jan Eric; Markussen, Wiebke Brix

2017-01-01

The optimal integration of booster heat pumps in ultra low temperature district heating (ULTDH) was investigated and compared to the performance of low temperature district heating. Two possible heat production technologies for the DH networks were analysed, namely extraction combined heat...... temperature and the heat consumption profile. For reference conditions, the optimal return of ULTDH varies between 21 °C and 27 °C. When using a central HP to supply the DH system, the resulting coefficient of system performance (COSP) was in the range of 3.9 (-) to 4.7 (-) for equipment with realistic...... component efficiencies and effectiveness, when including the relevant parameters such as DH system pressure and heat losses. By using ULTDH with booster HPs, performance improvements of 12% for the reference calculations case were found, if the system was supplied by central HPs. Opposite results were found...

Low-temperature nuclear heat applications: Nuclear power plants for district heating

International Nuclear Information System (INIS)

1987-08-01

The IAEA reflected the needs of its Member States for the exchange of information in the field of nuclear heat application already in the late 1970s. In the early 1980s, some Member States showed their interest in the use of heat from electricity producing nuclear power plants and in the development of nuclear heating plants. Accordingly, a technical committee meeting with a workshop was organized in 1983 to review the status of nuclear heat application which confirmed both the progress made in this field and the renewed interest of Member States in an active exchange of information about this subject. In 1985 an Advisory Group summarized the Potential of Low-Temperature Nuclear Heat Application; the relevant Technical Document reviewing the situation in the IAEA's Member States was issued in 1986 (IAEA-TECDOC-397). Programme plans were made for 1986-88 and the IAEA was asked to promote the exchange of information, with specific emphasis on the design criteria, operating experience, safety requirements and specifications for heat-only reactors, co-generation plants and power plants adapted for heat application. Because of a growing interest of the IAEA's Member States about nuclear heat employment in the district heating domaine, an Advisory Group meeting was organized by the IAEA on ''Low-Temperature Nuclear Heat Application: Nuclear Power Plants for District Heating'' in Prague, Czechoslovakia in June 1986. The information gained up to 1986 and discussed during this meeting is embodied in the present Technical Document. 22 figs, 11 tabs

Supply of domestic hot Water at comfortable temperatures by low-temperature district heating without risk of Legionella

DEFF Research Database (Denmark)

Yang, Xiaochen

disinfection efficacy for Legionella if supplied by LTDH, and inject no additives into the water. Thus, they can be considered as feasible sterilization solutions. In terms of the DHW system design methods, in addition to ensure the safe and hygiene DHW supply, the potential DHW systems should also...... temperature for space heating but lower than LTDH. Therefore, to meet the comfort and hygiene requirements for DHW supply, supplementary heating methods should be combined. However, one obstacle to realize the LTDH/ULTDH is the concern of the violation of the comfort and hygiene requirements of DHW supply....... According to the Danish standard, the supply for DHW should be able to reach 45 °C for the kitchen use and 40 °C for other uses for comfort. Regarding to the hygiene requirements, large DHW system with DHW storage tank and circulation has to use high temperature regime to get rid of Legionella. The storage...

Development of an innovative low temperature heat supply concept for a new housing area

OpenAIRE

Schmidt, Dietrich; Kallert, Anna; Orozaliev, Janybek; Best, Isabelle; Vajen, Klaus; Reul, Oliver; Bennewitz, Jochen; Gerhold, Petra

2017-01-01

The domestic energy demand of buildings is responsible for one third of the world's final energy consumption. To increase the sustainability of new housing areas, the identification of innovative heat supply concepts based on renewable energy sources (RES) is required. For the new housing area “Zum Feldlager” (Kassel, Germany), various supply concepts are studied. Main objective is the development of an innovative and efficient supply concept based on RES and low temperature district heating ...

Potential ability of zeolite to generate high-temperature vapor using waste heat

Science.gov (United States)

Fukai, Jun; Wijayanta, Agung Tri

2018-02-01

In various material product industries, a large amount of high temperature steam as heat sources are produced from fossil fuel, then thermal energy retained by condensed water at lower than 100°C are wasted. Thermal energies retained by exhaust gases at lower than 200°C are also wasted. Effective utilization of waste heat is believed to be one of important issues to solve global problems of energy and environment. Zeolite/water adsorption systems are introduced to recover such low-temperature waste heats in this study. Firstly, an adsorption steam recovery system was developed to generate high temperature steam from unused hot waste heat. The system used a new principle that adsorption heat of zeolite/water contact was efficiently extracted. A bench-scaled system was constructed, demonstrating contentious generation of saturated steam nearly 150°C from hot water at 80°C. Energy conservation is expected by returning the generated steam to steam lines in the product processes. Secondly, it was demonstrated that superheated steam/vapor at higher than 200°C could be generated from those at nearly 120°C using a laboratory-scaled setup. The maximum temperature and the time variation of output temperature were successfully estimated using macroscopic heat balances. Lastly, the maximum temperatures were estimated whose saturate air at the relative humidity 20-80% were heated by the present system. Theoretically, air at higher than 200°C was generated from saturate air at higher than 70°C. Consequently, zeolite/water adsorption systems have potential ability to regenerate thermal energy of waste water and exhaust gases.

Low grade waste heat recovery using heat pumps and power cycles

International Nuclear Information System (INIS)

Bor, D.M. van de; Infante Ferreira, C.A.; Kiss, Anton A.

2015-01-01

Thermal energy represents a large part of the global energy usage and about 43% of this energy is used for industrial applications. Large amounts are lost via exhaust gases, liquid streams and cooling water while the share of low temperature waste heat is the largest. Heat pumps upgrading waste heat to process heat and cooling and power cycles converting waste heat to electricity can make a strong impact in the related industries. The potential of several alternative technologies, either for the upgrading of low temperature waste heat such as compression-resorption, vapor compression and trans-critical heat pumps, or for the conversion of this waste heat by using organic Rankine, Kalina and trilateral cycle engines, are investigated with regards to energetic and economic performance by making use of thermodynamic models. This study focuses on temperature levels of 45–60 °C as at this temperature range large amounts of heat are rejected to the environment but also investigates the temperature levels for which power cycles become competitive. The heat pumps deliver 2.5–11 times more energy value than the power cycles in this low temperature range at equal waste heat input. Heat engines become competitive with heat pumps at waste heat temperatures at 100 °C and above. - Highlights: • Application of heat pump technology for heating and cooling. • Compression resorption heat pumps operating with large glides approaching 100 K. • Compression-resorption heat pumps with wet compression. • Potential to convert Industrial waste heat to power or high grade heat. • Comparison between low temperature power cycles and heat pumps

Generation of Hydrogen and Methane during Experimental Low-Temperature Reaction of Ultramafic Rocks with Water

Science.gov (United States)

McCollom, Thomas M.; Donaldson, Christopher

2016-06-01

Serpentinization of ultramafic rocks is widely recognized as a source of molecular hydrogen (H2) and methane (CH4) to support microbial activity, but the extent and rates of formation of these compounds in low-temperature, near-surface environments are poorly understood. Laboratory experiments were conducted to examine the production of H2 and CH4 during low-temperature reaction of water with ultramafic rocks and minerals. Experiments were performed by heating olivine or harzburgite with aqueous solutions at 90°C for up to 213 days in glass bottles sealed with butyl rubber stoppers. Although H2 and CH4 increased steadily throughout the experiments, the levels were very similar to those found in mineral-free controls, indicating that the rubber stoppers were the predominant source of these compounds. Levels of H2 above background were observed only during the first few days of reaction of harzburgite when CO2 was added to the headspace, with no detectable production of H2 or CH4 above background during further heating of the harzburgite or in experiments with other mineral reactants. Consequently, our results indicate that production of H2 and CH4 during low-temperature alteration of ultramafic rocks may be much more limited than some recent experimental studies have suggested. We also found no evidence to support a recent report suggesting that spinels in ultramafic rocks may stimulate H2 production. While secondary silicates were observed to precipitate during the experiments, formation of these deposits was dominated by Si released by dissolution of the glass bottles, and reaction of the primary silicate minerals appeared to be very limited. While use of glass bottles and rubber stoppers has become commonplace in experiments intended to study processes that occur during serpentinization of ultramafic rocks at low temperatures, the high levels of H2, CH4, and SiO2 released during heating indicate that these reactor materials are unsuitable for this purpose.

The low-temperature water-water reactor for district heating atomic power plant (DHPP)

International Nuclear Information System (INIS)

Skvortsov, S.A.; Sokolov, I.N.; Krauze, L.V.; Nikiporetz, Yu.G.; Philimonov, Yu.V.

1977-01-01

The district heating atomic power plant in the article is distinguished by the increased reliability and safety of operation that was provided by the use of following main principles: relatively low parameters of the coolant; the intergral arrangement of equipment and accordingly the minimum branching of the reactor circuit; the natural circulation of coolant of the primary circuit in the steady-state, transient and emergency regimes of reactor operation; the considerable reserves of cold water of the primary circuit in the reactor vessel, providing the emergency cooling; the application of two shells each of which is designed for the total working pressure, the second shell is made of prestressed reinforced concrete that eliminates its brittle failure. (M.S.)

Effects of the generator and evaporator temperature differences on a double absorption heat transformer—Different control strategies on utilizing heat sources

International Nuclear Information System (INIS)

Wang, Hanzhi; Li, Huashan; Bu, Xianbiao; Wang, Lingbao

2017-01-01

Highlights: • Effects of the GETD on the DAHT system performance are analyzed. • Three different configurations are compared in detail. • Suggestions on the heat source control strategies are given. - Abstract: The combination of the absorption heat transformer with renewable energy systems, like solar thermal systems, is raising more and more concern. In those combined systems the strategies on utilizing heat sources can affect system thermodynamic performance significantly. Therefore, this study presents a detailed analysis on the effect of the heat source temperature and different heat source flow patterns on the performance of a double absorption heat transformer (DAHT). A detailed comparative study is carried out to clarify the impact of the generator and evaporator temperature differences (GETD) on the coefficient of performance (COP), exergy efficient (ECOP), exergy destruction rates in the individual components and heat transfer areas needed for each component. The results show that the generator, condenser and absorber-evaporator are responsible for most of the exergy destruction rate in the DAHT system; the parallel-flow configuration (the generator temperature is equal to the evaporator temperature) performs better under the high gross temperature lift conditions; in the case of the counter-flow configuration (the generator temperature is relatively higher), better performance can be obtained in both the COP and ECOP under the proper heat source temperature (85 and 95 °C); the fair-flow configuration (higher temperature in the evaporator) is not recommended in this paper due to no advantages found in either thermodynamic performance or system size.

A dilution refrigerator combining low base temperature, high cooling power and low heat leak for use with nuclear cooling

International Nuclear Information System (INIS)

Bradley, D.I.; Guenault, A.M.; Keith, V.; Miller, I.E.; Pickett, G.R.; Bradshaw, T.W.; Locke-Scobie, B.G.

1982-01-01

The design philosophy, design, construction and performance of a dilution refrigerator specifically intended for nuclear cooling experiments in the submillikelvin regime is described. Attention has been paid from the outset to minimizing sources of heat leaks, and to achieving a low base temperature and relatively high cooling power below 10 mK. The refrigerator uses sintered silver heat exchangers similar to those developed at Grenoble. The machine has a base temperature of 3 mK or lower and can precool a copper nuclear specimen in 6.8 T to 8 mK in 70 h. The heat leak to the innermost nuclear stage is < 30 pW after only a few days' running. (author)

Solar radiative heating of fiber-optic cables used to monitor temperatures in water

Science.gov (United States)

Neilson, Bethany T.; Hatch, Christine E.; Ban, Heng; Tyler, Scott W.

2010-08-01

In recent years, applications of distributed temperature sensing (DTS) have increased in number and diversity. Because fiber-optic cables used for DTS are typically sheathed in dark UV-resistant materials, the question arises as to how shortwave solar radiation penetrating a water column influences the accuracy of absolute DTS-derived temperatures in aquatic applications. To quantify these effects, we completed a modeling effort that accounts for the effects of radiation and convection on a submersed cable to predict when solar heating may be important. Results indicate that for cables installed at shallow depths in clear, low-velocity water bodies, measurable heating of the cable is likely during peak solar radiation. However, at higher velocities, increased turbidity and/or greater depths, the effects of solar heating are immeasurable. A field study illustrated the effects of solar radiation by installing two types of fiber-optic cable at multiple water depths (from 0.05 to 0.8 m) in the center and along the sidewall of a trapezoidal canal. Thermistors were installed at similar depths and shielded from solar radiation to record absolute water temperatures. During peak radiation, thermistor data showed small temperature differences (˜0.003°C-0.04°C) between depths suggesting minor thermal stratification in the canal center. DTS data from cables at these same depths show differences of 0.01°C-0.17°C. The DTS differences cannot be explained by stratification alone and are likely evidence of additional heating from solar radiation. Sidewall thermistor strings also recorded stratification. However, corresponding DTS data suggested that bed conduction overwhelmed the effects of solar radiation.

Dynamic study of steam generation from low-grade waste heat in a zeolite–water adsorption heat pump

International Nuclear Information System (INIS)

Xue, Bing; Meng, Xiangrui; Wei, Xinli; Nakaso, Koichi; Fukai, Jun

2015-01-01

A novel zeolite–water adsorption heat pump system based on a direct-contact heat exchange method to generate steam from low-grade waste gas and water has been proposed and examined experimentally. Superheated steam (200 °C, 0.1 MPa) is generated from hot water (70–80 °C) and dry air (100–130 °C). A dynamic model for steam generation process is developed to describe local mass and heat transfer. This model features a three-phase calculation and a moving water–gas interface. The calculations are carried out in the zeolite–water and zeolite–gas regions. Model outputs are compared with experimental results for validation. The thermal response inside the reactor and mass of steam generated is well predicted. Numerical results show that preheat process with low-temperature steam is an effective method to achieve local equilibrium quickly, thus generation process is enhanced by prolonging the time and increasing mass of the generated steam. Besides, high-pressure steam generation up to 0.5 MPa is possible from the validated dynamic model. Future work could be emphasized on enhancing high-pressure steam generation with preheat process or mass recovery operation

A renewable energy scenario for Aalborg Municipality based on low-temperature geothermal heat, wind power and biomass

DEFF Research Database (Denmark)

Østergaard, Poul Alberg; Mathiesen, Brian Vad; Möller, Bernd

2010-01-01

Aalborg Municipality, Denmark, wishes to investigate the possibilities of becoming independent of fossil fuels. This article describes a scenario for supplying Aalborg Municipality’s energy needs through a combination of low-temperature geothermal heat, wind power and biomass. Of particular focus...... in the scenario is how low-temperature geothermal heat may be utilised in district heating (DH) systems. The analyses show that it is possible to cover Aalborg Municipality’s energy needs through the use of locally available sources in combination with significant electricity savings, heat savings, reductions...... in industrial fuel use and savings and fuel-substitutions in the transport sector. With biomass resources being finite, the two marginal energy resources in Aalborg are geothermal heat and wind power. If geothermal heat is utilised more, wind power may be limited and vice versa. The system still relies...

Design and application for a high-temperature nuclear heat source

International Nuclear Information System (INIS)

Quade, R.N.

1980-01-01

Recent actions by OPEC have sharply increased interest in the United States in synfuels, with coal being the logical choice for the carbon source. Two coal liquefaction processes, direct and indirect, have been examined. Each can produce about 50% more output when coupled to an HTGR for process heat. The nuclear reactor designed for process heat has a power output of 842MW(t), a core outlet temperature of 950 0 C (1742 0 F), and an intermediate helium loop to separate the heat source from the process heat exchangers. Steam-methane reforming is the reference process. As part of the development of a nuclear process heat system, a computer code, Process Heat Reactor Evaluation and Design, is being developed. This code models both the reactor plant and a steam reforming plant. When complete, the program will have the capability to calculate an overall mass and heat balance, size the plant components, and estimate the plant cost for a wide variety of independent variables. (author)

Case study of low-temperature heating in an existing single-family house-A test of methods for simulation of heating system temperatures

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

2016-01-01

and the calculated indoor temperatures and radiator return temperatures were compared to temperatures measured in the case house. The results showed that the detail of the simulation model has a large influence on the results obtained. The estimated return temperatures from the radiators varied by up to 16 degrees C...... depending on the assumptions made in the simulation model. The results indicated that a detailed building simulation model can provide a good estimate of the actual heating system operation, provided that actual radiators and realistic indoor temperatures are taken into account in the model. (C) 2016......Low-temperature heating provides an efficient way of heating our buildings. To obtain a high efficiency it is important that the heating systems in the buildings are operated with both low supply and return temperatures. This study set out to investigate how typical assumptions in the modelling...

Transient thermal stress distribution in a circular pipe heated externally with a periodically moving heat source

International Nuclear Information System (INIS)

Özışık, Gülşah; Genç, M. Serdar; Yapıcı, Hüseyin

2012-01-01

This study presents the effects of periodically moving heat source on a circular steel pipe heated partly from its outer surface under stagnant ambient conditions. While the pipe is heated with this heat source applied on a certain section having a thickness of heat flux, the water flows through it to transfer heat. It is assumed that the flow is a fully-developed laminar flow. The heat source moves along from one end of the outer to the other end with a constant speed and then returns to the first end with the same speed. It is assumed that the heat transfer rate has a constant value, and that the thermo-physical properties of the steel do not change with temperature (elastic analysis). The numerical calculations have been performed individually for a wide range of thermal conductivity of steel and for different thicknesses of heat flux. The moving heat source produces the non-uniform temperature gradient and the non-uniform effective thermal stress, and when it arrives at the ends of the pipe, the temperature and effective thermal stress ratio profiles rise more excessively. The tangential component is more dominant in the effective thermal stress than the radial component. Highlights: ► Moving heat source produces non-uniform temperature gradients and thermal stresses. ► When moving heat source arrives at ends of pipe, temperature gradients rise excessively. ► With increasing of heat flux thickness and thermal conductivity, the temperature gradients reduce. ► Temperature gradients in thermal boundary layers slightly increase. ► Tangential component is more dominant in thermal stress than radial component.

Critical heat flux analysis on change of plate temperature and cooling water flow rate for rectangular narrow gap with bilateral-heated cases

International Nuclear Information System (INIS)

M Hadi Kusuma; Mulya Juarsa; Anhar Riza Antariksawan

2013-01-01

Boiling heat transfer phenomena on rectangular narrow gap was related to the safety of nuclear reactors. Research done in order to study the safety of nuclear reactors in particular relating to boiling heat transfer and useful on the improvement of next-generation reactor designs. The research focused on calculation of the heat flux during the cooling process in rectangular narrow gap size 1.0 mm. with initial temperatures 200°C. 400°C, and 600°C, also the flow rates of cooling water 0,1 liters/second. 0,2 liters/second. and 0,3 liters/second. Experiments carried out by injecting water at a certain flow rate with the water temperature 85°C. Transient temperature measurement data recorded by the data acquisition system. Transient temperature measurement data is used to calculate the flux of heat gain is then used to obtain the heat transfer coefficient. This research aimed to obtain the correlation between critical heat flux and heat transfer coefficient to changes in temperatures and water flow rates for bilaterally-heated cases on rectangular narrow gap. The results obtained for a constant cooling water flow rate, critical heat flux will increase when hot plate temperature also increased. While on a constant hot plate temperature, coefficient heat transfer will increase when cooling water flow rate also increased. Thus it can be said that the cooling water flow rate and temperature of the hot plate has a significant effect on the critical heat flux and heat transfer coefficient resulted in quenching process of vertical rectangular narrow gap with double-heated cases. (author)

Energetic and exergetic investigation of an organic Rankine cycle at different heat source temperatures

International Nuclear Information System (INIS)

Li, Jing; Pei, Gang; Li, Yunzhu; Wang, Dongyue; Ji, Jie

2012-01-01

The energetic and exergetic performance of an updated ORC (organic Rankine cycle) is investigated. The thermal efficiencies of the ORC at different heat source temperatures of about 100, 90, 80, and 70 °C are explored. The thermodynamic irreversibility that takes place in the evaporator, condenser, turbine, pump, and separator is revealed. The ORC feasibility for low-temperature applications is demonstrated. With a hot side temperature of around 80 °C, a thermal efficiency of 7.4% and a turbine isentropic efficiency of 0.68 can be achieved. The present research further indicates that exergy destruction caused by heat transfer through an appreciable temperature difference in the evaporator is the largest in the energy conversion process, followed by that in the condenser. The exergy destroyed in the heat exchangers amounts to 74% of the overall exergy loss. The total system exergy efficiency is approximately 40%; thus, ways to improve exergy efficiency are required. HCFC-123, a dry fluid, is experimentally confirmed to be highly superheated after expansion in this study. A regenerator should be used to preheat HCFC-123 prior to entering the evaporator. Meanwhile the heat-transfer configuration with two oil cycles can be a good solution to overcome the thermodynamic disadvantage of a one-stage evaporator. -- Highlights: ► An updated ORC system is introduced. ► The ORC feasibility for low-temperature applications is experimentally demonstrated. ► Thermodynamic irreversibility in ORC components is revealed. ► Suggestions are given to reduce the exergy destruction.

Long distance transmission of low grade heat

International Nuclear Information System (INIS)

Arnott, P.T.W.

1977-01-01

This paper is concerned with low and medium temperature water carried by pipeline as a heat transfer medium for the purpose of utilising the waste heat arising from the nuclear power generation process. Different pipelines, single and double, and alternative pipe materials to steel are presented. Later in the paper the effect of the sending-end temperature on the viability of a water pipeline transmission system is discussed and the consequences of using small quantities of steam in order to boost the water temperature are explained. (M.S.)

Expieriences On Low-Temperature District Heating In Lystrup – Denmark

DEFF Research Database (Denmark)

Thorsen, Jan Eric; Christiansen, Christian Holm; Brand, Marek

2011-01-01

by implementing Low-temperature district heating systems. Demonstration cases in EnergyFlexHouse and Boligforeningen Ringgården” EUDP 2011. A key challenge for optimum and competitive district heating (DH) system operation is reducing heat loss in networks. Today building regulations in most countries demand...

TWO-STAGE HEAT PUMPS FOR ENERGY SAVING TECHNOLOGIES

Directory of Open Access Journals (Sweden)

A. E. Denysova

2017-09-01

Full Text Available The problem of energy saving becomes one of the most important in power engineering. It is caused by exhaustion of world reserves in hydrocarbon fuel, such as gas, oil and coal representing sources of traditional heat supply. Conventional sources have essential shortcomings: low power, ecological and economic efficiencies, that can be eliminated by using alternative methods of power supply, like the considered one: low-temperature natural heat of ground waters of on the basis of heat pump installations application. The heat supply system considered provides an effective use of two stages heat pump installation operating as heat source at ground waters during the lowest ambient temperature period. Proposed is a calculation method of heat pump installations on the basis of groundwater energy. Calculated are the values of electric energy consumption by the compressors’ drive, and the heat supply system transformation coefficient µ for a low-potential source of heat from ground waters allowing to estimate high efficiency of two stages heat pump installations.

Active pipe-embedded structures in buildings for utilizing low-grade energy sources: A review

International Nuclear Information System (INIS)

Xu, Xinhua; Wang, Jinbo; Wang, Shengwei; Xiao, Fu

2010-01-01

Low-grade energy sources such as geothermal energy, favorable ambient air and industrial waste heat etc. exist widely. Sufficient utilization of these low-grade energy sources may reduce our daily dependence on high-grade energy sources such as electricity resulting in reduced emission of green house gas for environmental conservation. Active pipe-embedded structure as floor/ceiling usually with water as the medium to carry heat or coolth may utilize these low-grade energy sources for providing space air-conditioning. Compact arrangement of pipes in the structure may significantly enlarge heat transfer surface between the slab mass and water in the pipe allowing substantial heat flows even for relatively small temperature differences. Application of the heat or coolth storage capacity of this structure for preheating or pre-cooling is also one among the advantages of this structure for shifting load and exploiting the nighttime cheap electricity tariff in some regions. This paper presents the technology of the active pipe-embedded structure for utilizing widely existing low-grade energy sources following by a comprehensive review on the heat transfer calculation models of this structure and its practical applications in real building systems for space air-conditioning. This review shows that more works on the active structure, especially simple and transient models for dynamic and accurate performance prediction and easy integration with existing building energy simulation packages, are worthwhile for further promoting the practical application wherever the low-grade energy sources are favorable. (author)

Thermodynamic analysis on an instantaneous water heating system of shower wastewater source heat pump

Directory of Open Access Journals (Sweden)

Yuguo Wu

2018-09-01

Full Text Available Water reuse and desalination systems are energy intensive processes, and their increasing use is leading energy consumption within water systems to be an increasingly important issue. Shower wastewater contains large amounts of heat, so there is an opportunity to recover energy from shower water to offset energy consumption elsewhere in water systems. This paper found ways to increase the output of hot water and lower the energy consumption by establishing a thermodynamic model of an instantaneous wastewater source heat pump. The system proved to be very effective, the heating COP (coefficient of performance can reach 3.3 even in the winter. Under the conditions of limited heat transfer area, reducing the suction pressure of a compressor is a more feasible way to increase the hot water output to meet the needs of users rather than increasing the discharge pressure. Besides, increasing the heat transfer area of the evaporator is a more effective option. When the heat transfer area of evaporator varies from 0.5 to 1.0 square meters, a notable change is that the heating COP increases from 3.283 to 3.936. The heating COP in a system with a recuperator can reach 5.672, almost double that compared to the original systems.

Thermodynamic performance analysis of sequential Carnot cycles using heat sources with finite heat capacity

International Nuclear Information System (INIS)

Park, Hansaem; Kim, Min Soo

2014-01-01

The maximum efficiency of a heat engine is able to be estimated by using a Carnot cycle. Even though, in terms of efficiency, the Carnot cycle performs the role of reference very well, its application is limited to the case of infinite heat reservoirs, which is not that realistic. Moreover, considering that one of the recent key issues is to produce maximum work from low temperature and finite heat sources, which are called renewable energy sources, more advanced theoretical cycles, which can present a new standard, and the research about them are necessary. Therefore, in this paper, a sequential Carnot cycle, where multiple Carnot cycles are connected in parallel, is studied. The cycle adopts a finite heat source, which has a certain initial temperature and heat capacity, and an infinite heat sink, which is assumed to be ambient air. Heat transfer processes in the cycle occur with the temperature difference between a heat reservoir and a cycle. In order to resolve the heat transfer rate in those processes, the product of an overall heat transfer coefficient and a heat transfer area is introduced. Using these conditions, the performance of a sequential Carnot cycle is analytically calculated. Furthermore, as the efforts for enhancing the work of the cycle, the optimization research is also conducted with numerical calculation. - Highlights: • Modified sequential Carnot cycles are proposed for evaluating low grade heat sources. • Performance of sequential Carnot cycles is calculated analytically. • Optimization study for the cycle is conducted with numerical solver. • Maximum work from a heat source under a certain condition is obtained by equations

Effect of Challenge Temperature and Solute Type on Heat Tolerance of Salmonella Serovars at Low Water Activity

Science.gov (United States)

Mattick, K. L.; Jørgensen, F.; Wang, P.; Pound, J.; Vandeven, M. H.; Ward, L. R.; Legan, J. D.; Lappin-Scott, H. M.; Humphrey, T. J.

2001-01-01

Salmonella spp. are reported to have an increased heat tolerance at low water activity (aw; measured by relative vapor pressure [rvp]), achieved either by drying or by incorporating solutes. Much of the published data, however, cover only a narrow treatment range and have been analyzed by assuming first-order death kinetics. In this study, the death of Salmonella enterica serovar Typhimurium DT104 when exposed to 54 combinations of temperature (55 to 80°C) and aw (rvp 0.65 to 0.90, reduced using glucose-fructose) was investigated. The Weibull model (LogS = −btn) was used to describe microbial inactivation, and surface response models were developed to predict death rates for serovar Typhimurium at all points within the design surface. The models were evaluated with data generated by using six different Salmonella strains in place of serovar Typhimurium DT104 strain 30, two different solutes in place of glucose-fructose to reduce aw, or six low-aw foods artificially contaminated with Salmonella in place of the sugar broths. The data demonstrate that, at temperatures of ≥70°C, Salmonella cells at low aw were more heat tolerant than those at a higher aw but below 65°C the reverse was true. The same patterns were generated when sucrose (rvp 0.80 compared with 0.90) or NaCl (0.75 compared with 0.90) was used to reduce aw, but the extent of the protection afforded varied with solute type. The predictions of thermal death rates in the low-aw foods were usually fail-safe, but the few exceptions highlight the importance of validating models with specific foods that may have additional factors affecting survival. PMID:11526015

The Influence of the Heat Source Temperature on the Multivane Expander Output Power in an Organic Rankine Cycle (ORC System

Directory of Open Access Journals (Sweden)

Piotr Kolasiński

2015-04-01

Full Text Available Organic Rankine Cycle (ORC power systems are nowadays an option for local and domestic cogeneration of heat and electric power. Very interesting are micropower systems for heat recovery from low potential (40–90 °C waste and renewable heat sources. Designing an ORC system dedicated to heat recovery from such a source is very difficult. Most important problems are connected with the selection of a suitable expander. Volumetric machines, such as scroll and screw expanders, are adopted as turbine alternative in small-power ORC systems. However, these machines are complicated and expensive. Vane expanders on the other hand are simple and cheap. This paper presents a theoretical and experimental analysis of the operation of a micro-ORC rotary vane expander under variable heat source temperature conditions. The main objective of this research was therefore a comprehensive analysis of relation between the vane expander output power and the heat source temperature. A series of experiments was performed using the micropower ORC test-stand. Results of these experiments are presented here, together with a mathematical description of multivane expanders. The analysis presented in this paper indicates that the output power of multivane expanders depend on the heat source temperature, and that multivane expanders are cheap alternatives to other expanders proposed for micropower ORC systems.

Experimental study on local heat transfer characteristics of porous media with internal heat source

International Nuclear Information System (INIS)

Zan Yuanfeng; Wang Taotao; Xiao Zejun; Wang Fei; Huang Yanping

2008-01-01

Model of porous media with internal heat source is established. The model uses water as flowing media, and the stainless steel test section is packed with steel spheres in manner of regular triangle, respectively. The armoured resistance wire is inserted inside the steel sphere. On the basis of the experimental model, many parameters of the local heat transfer characteristics including current velocity and wall temperature of steel sphere are measured. The experimental results show that the coefficient of heat transfer scarcely changes with pressure. The coefficient of heat transfer increases with the surface heat flux of steel sphere. When raising the inlet temperature of the cooling water, the coefficient of heat transfer presents the descending trend. In addition, the influence of entrance effect on heat transfer is discovered in the experiment, which is much less than the liquid flow in the light tube. After experiment data are analyzed and processed, the relation model of heat transfer on local heat transfer characteristic of porous media with internal heat source was described with a power-law-equation. The deviations between calculation and experimental values are within ±10%. (authors)

Hoosac tunnel geothermal heat source. Final report

Energy Technology Data Exchange (ETDEWEB)

1982-06-10

The Hoosac Rail Tunnel has been analyzed as a central element in a district heating system for the City of North Adams. The tunnel has been viewed as a collector of the earth's geothermal heat and a seasonal heat storage facility with heat piped to the tunnel in summer from existing facilities at a distance. Heated fluid would be transported in winter from the tunnel to users who would boost the temperature with individual heat pumps. It was concluded the tunnel is a poor source of geothermal heat. The maximum extractable energy is only 2200 million BTU (20000 gallons of oil) at 58/sup 0/F. The tunnel is a poor heat storage facility. The rock conductivity is so high that 75% of the heat injected would escape into the mountain before it could be recaptured for use. A low temperature system, with individual heat pumps for temperature boost could be economically attractive if a low cost fuel (byproduct, solid waste, cogeneration) or a cost effective seasonal heat storage were available.

Climate Adaptivity and Field Test of the Space Heating Used Air-Source Transcritical CO2 Heat Pump

Science.gov (United States)

Song, Yulong; Ye, Zuliang; Cao, Feng

2017-08-01

In this study, an innovation of air-sourced transcritical CO2 heat pump which was employed in the space heating application was presented and discussed in order to solve the problem that the heating performances of the transcritical CO2 heat pump water heater deteriorated sharply with the augment in water feed temperature. An R134a cycle was adopted as a subcooling device in the proposed system. The prototype of the presented system was installed and supplied hot water for three places in northern China in winter. The field test results showed that the acceptable return water temperature can be increased up to 55°C, while the supply water temperature was raised rapidly by the presented prototype to up to 70°C directly, which was obviously appropriate to the various conditions of heating radiator in space heating application. Additionally, though the heating capacity and power dissipation decreased with the decline in ambient temperature or the augment in water temperature, the presented heat pump system performed efficiently whatever the climate and water feed temperature were. The real time COP of the presented system was generally more than 1.8 in the whole heating season, while the seasonal performance coefficient (SPC) was also appreciable, which signified that the economic efficiency of the presented system was more excellent than other space heating approaches such as fuel, gas, coal or electric boiler. As a result, the novel system will be a promising project to solve the energy issues in future space heating application.

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

Post-CHF low-void heat transfer of water: measurements in the complete transition boiling region at atmospheric pressure

International Nuclear Information System (INIS)

Johannsen, K.; Meinen, W.

1984-01-01

An experimental investigation of low-void heat transfer of water has been performed in the range of CHF and the minimum stable film boiling temperature. The heat transfer system used consists of a vertically mounted copper tube of 1 cm I.D. and 5 cm length with surface-temperature controlled, indirect Joule heating. Results are presented for upflowing water at inverted annular flow conditions in the inlet subcooling range of 2.5 - 40 0 C and mass flux range of 137-600 kg/m 2 s in terms of boiling curves and heat transfer coefficients versus wall temperature. Heat transfer in the stationary rewetting front, which occurs within the test section during operation in the transition boiling mode, is also dealt with. At high mass flux, occurrence of an inverse rewetting front has been observed. It is also noted that, at fixed location, minimum heat flux observed is usually not associated with the minimum stable film boiling temperature

Regional Energy Planning Tool for Renewable Integrated Low-Energy District Heating Systems

DEFF Research Database (Denmark)

Tol, Hakan; Dincer, Ibrahim; Svendsen, Svend

2013-01-01

Low-energy district heating systems, operating at low temperature of 55 °C as supply and 25°C as return, can be the energy solution as being the prevailing heating infrastructure in urban areas, considering future energy schemesaiming at increased exploitation of renewable energy sources together...... with low-energy houses in focus with intensified energy efficiency measures. Employing low-temperature operation allows the ease to exploit not only any type of heat source but also low-grade sources, i.e., renewable and industrial waste heat, which would otherwise be lost. In this chapter, a regional...... energy planning tool is described considered with various energy conversion systems based on renewable energy sources to be supplied to an integrated energy infrastructure involving a low-energy district heating, a district cooling, and an electricity grid. The developed tool is performed for two case...

Air source integrated heat pump simulation model for EnergyPlus

Energy Technology Data Exchange (ETDEWEB)

Shen, Bo; New, Joshua; Baxter, Van

2017-12-01

An Air Source Integrated Heat Pump (AS-IHP) is an air source, multi-functional spacing conditioning unit with water heating function (WH), which can lead to great energy savings by recovering the condensing waste heat for domestic water heating. This paper summarizes development of the EnergyPlus AS-IHP model, introducing the physics, sub-models, working modes, and control logic. Based on the model, building energy simulations were conducted to demonstrate greater than 50% annual energy savings, in comparison to a baseline heat pump with electric water heater, over 10 US cities, using the EnergyPlus quick-service restaurant template building. We assessed water heating energy saving potentials using AS-IHP versus both gas and electric baseline systems, and pointed out climate zones where AS-IHPs are promising. In addition, a grid integration strategy was investigated to reveal further energy saving and electricity cost reduction potentials, via increasing the water heating set point temperature during off-peak hours and using larger water tanks.

Three dimensional optimization of small-scale axial turbine for low temperature heat source driven organic Rankine cycle

International Nuclear Information System (INIS)

Al Jubori, Ayad; Al-Dadah, Raya K.; Mahmoud, Saad; Bahr Ennil, A.S.; Rahbar, Kiyarash

2017-01-01

Highlights: • Three-dimensional optimization of axial turbine stage is presented. • Six organic fluids suitable for low-temperature heat source are considered. • Three-dimensional optimization has been done for each working fluid. • The results showed highlight the potential of optimization technique. • The performance of optimized turbine has been improved off-design conditions. - Abstract: Advances in optimization techniques can be used to enhance the performance of turbines in various applications. However, limited work has been reported on using such optimization techniques to develop small-scale turbines for organic Rankine cycles. This paper investigates the use of multi-objective genetic algorithm to optimize the stage geometry of a small-axial subsonic turbine. This optimization is integrated with organic Rankine cycle analysis using wide range of high density organic working fluids like R123, R134a, R141b, R152a, R245fa and isobutane suitable for low temperature heat sources <100 °C such as solar energy to achieve the best turbine design and highest organic Rankine cycle efficiency. The isentropic efficiency of the turbine in most of the reported organic Rankine cycle studies was assumed constant, while the current work allows the turbine isentropic efficiency to change (dynamic value) with both operating conditions and working fluids. Three-dimensional computational fluid dynamics analysis and multi-objective genetic algorithm optimization were performed using three-dimensional Reynolds-averaged Navier-Stokes equations with k-omega shear stress transport turbulence model in ANSYS"R"1"7-CFX and design exploration for various working fluids. The optimization was carried out using eight design parameters for the turbine stage geometry optimization including stator and rotor number of blades, rotor leading edge beta angle, trailing edge beta angle, stagger angle, throat width, trailing half wedge angle and shroud tip clearance. Results showed that

Energy and exergy analysis of a double effect absorption refrigeration system based on different heat sources

International Nuclear Information System (INIS)

Kaynakli, Omer; Saka, Kenan; Kaynakli, Faruk

2015-01-01

Highlights: • Energy and exergy analysis was performed on double effect series flow absorption refrigeration system. • The refrigeration system runs on various heat sources such as hot water, hot air and steam. • A comparative analysis was carried out on these heat sources in terms of exergy destruction and mass flow rate of heat source. • The effect of heat sources on the exergy destruction of high pressure generator was investigated. - Abstract: Absorption refrigeration systems are environmental friendly since they can utilize industrial waste heat and/or solar energy. In terms of heat source of the systems, researchers prefer one type heat source usually such as hot water or steam. Some studies can be free from environment. In this study, energy and exergy analysis is performed on a double effect series flow absorption refrigeration system with water/lithium bromide as working fluid pair. The refrigeration system runs on various heat sources such as hot water, hot air and steam via High Pressure Generator (HPG) because of hot water/steam and hot air are the most common available heat source for absorption applications but the first law of thermodynamics may not be sufficient analyze the absorption refrigeration system and to show the difference of utilize for different type heat source. On the other hand operation temperatures of the overall system and its components have a major effect on their performance and functionality. In this regard, a parametric study conducted here to investigate this effect on heat capacity and exergy destruction of the HPG, coefficient of performance (COP) of the system, and mass flow rate of heat sources. Also, a comparative analysis is carried out on several heat sources (e.g. hot water, hot air and steam) in terms of exergy destruction and mass flow rate of heat source. From the analyses it is observed that exergy destruction of the HPG increases at higher temperature of the heat sources, condenser and absorber, and lower

Ground-water heat pumps: an examination of hydrogeologic, environmental, legal, and economic factors affecting their use

Energy Technology Data Exchange (ETDEWEB)

Armitage, D M; Bacon, D J; Massey-Norton, J T; Miller, J D

1980-11-12

Groundwater is attractive as a potential low-temperature energy source in residential space-conditioning applications. When used in conjuncton with a heat pump, ground water can serve as both a heat source (for heating) and a heat sink (for cooling). Major hydrogeologic aspects that affect system use include groundwater temperature and availability at shallow depths as these factors influence operational efficiency. Ground-water quality is considered as it affects the performance and life-expectancy of the water-side heat exchanger. Environmental impacts related to groundwater heat pump system use are most influenced by water use and disposal methods. In general, recharge to the subsurface (usually via injection wells) is recommended. Legal restrictions on system use are often stricter at the municipal and county levels than at state and Federal levels. Although Federal regulations currently exist, the agencies are not equipped to regulate individual, domestic installations. Computer smulations indicate that under a variety of climatologic conditions, groundwater heat pumps use less energy than conventional heating and cooling equipment. Life-cycle cost comparisons with conventional equipment depend on alternative system choices and well cost options included in the groundwater heat pump system.

Low-Cost Solar Water Heating Research and Development Roadmap

Energy Technology Data Exchange (ETDEWEB)

Hudon, K.; Merrigan, T.; Burch, J.; Maguire, J.

2012-08-01

The market environment for solar water heating technology has changed substantially with the successful introduction of heat pump water heaters (HPWHs). The addition of this energy-efficient technology to the market increases direct competition with solar water heaters (SWHs) for available energy savings. It is therefore essential to understand which segment of the market is best suited for HPWHs and focus the development of innovative, low-cost SWHs in the market segment where the largest opportunities exist. To evaluate cost and performance tradeoffs between high performance hot water heating systems, annual energy simulations were run using the program, TRNSYS, and analysis was performed to compare the energy savings associated with HPWH and SWH technologies to conventional methods of water heating.

Heats of immersion in the thorium oxide-water system at elevated temperatures

International Nuclear Information System (INIS)

Holmes, H.F.

1976-01-01

The surface properties of ThO 2 were studied by heat of immersion calorimetry at 25 to 200 0 C. Results show that the integral heat of immersion of thorium oxide contains contributions which reflect considerable interaction with several layers of water adjacent to the oxide surface. It would be desirable to know the heat capacity changes which occur in the multilayer adsorption of water on an oxide surface. However, such data are not available and their acquisition would be an extremely difficult task. Structuring (a negative ΔCp) of several layers of water (by increased hydrogen bonding) adjacent to an oxide surface could explain an increase in the heat of immersion as the immersion temperature is increased. The more energetic, heterogeneous, high-surface-area samples are expected to induce more order in the adjacent water layers than the less energetic samples. This interpretation is similar to that offered for the temperature dependence of the heat of solution of the alkali halides

Remote Monitoring of Soil Water Content, Temperature, and Heat Flow Using Low-Cost Cellular (3G) IoT Technology

Science.gov (United States)

Ham, J. M.

2016-12-01

New microprocessor boards, open-source sensors, and cloud infrastructure developed for the Internet of Things (IoT) can be used to create low-cost monitoring systems for environmental research. This project describes two applications in soil science and hydrology: 1) remote monitoring of the soil temperature regime near oil and gas operations to detect the thermal signature associated with the natural source zone degradation of hydrocarbon contaminants in the vadose zone, and 2) remote monitoring of soil water content near the surface as part of a global citizen science network. In both cases, prototype data collection systems were built around the cellular (2G/3G) "Electron" microcontroller (www.particle.io). This device allows connectivity to the cloud using a low-cost global SIM and data plan. The systems have cellular connectivity in over 100 countries and data can be logged to the cloud for storage. Users can view data real time over any internet connection or via their smart phone. For both projects, data logging, storage, and visualization was done using IoT services like Thingspeak (thingspeak.com). The soil thermal monitoring system was tested on experimental plots in Colorado USA to evaluate the accuracy and reliability of different temperature sensors and 3D printed housings. The soil water experiment included comparison opens-source capacitance-based sensors to commercial versions. Results demonstrate the power of leveraging IoT technology for field research.

Thermal-hydraulic process for cooling, heating and power production with low-grade heat sources in residential sector

International Nuclear Information System (INIS)

Borgogno, R.; Mauran, S.; Stitou, D.; Marck, G.

2017-01-01

Highlights: • Assessment of solar thermal-hydraulic process for tri-generation application. • Choice of the most suitable working fluid pair (R1234yf/R1233zd). • Evaluation of the global annual performance in Mediterranean climate. • Global annual COP and heat amplification achieving 0.24 and 1.2 respectively. • Global annual performance achieving an electric efficiency of 3.7%. - Abstract: A new process based on thermal-hydraulic conversion actuated by low-grade thermal energy is investigated. Input thermal energy can be provided by the means of solar collectors, as well as other low temperature energy sources. In the following article, “thermo-hydraulic” term refers to a process involving an incompressible fluid used as an intermediate medium to transfer work hydraulically between different thermal operated components or sub-systems. The system aims at providing trigeneration energy features for the residential sector, that is providing heating, cooling and electrical power for meeting the energy needs of domestic houses. This innovative system is made of two dithermal processes (working at two different levels of temperatures) and featuring two different working fluids. The first process is able to directly supply either electrical energy generated by an hydraulic turbine or drives the second process thanks to the incompressible fluid, which is similar to a heat pump effect for heating or cooling purposes. The innovative aspect of this process relies on the use of an hydraulic transfer fluid to transfer the work between each sub-system and therefore simplifying the conversion chain. A model, assuming steady-state operation, is developed to assess the energy performances of different variants of this thermo-hydraulic process with various heat source temperatures (80–110 °C) or heat sinks (0–30 °C), as well as various pairs of working fluids. For instance, in the frame of a single-family home, located in the Mediterranean region, the working

Energy Efficiency and Performance Limiting Effects in Thermo-Osmotic Energy Conversion from Low-Grade Heat.

Science.gov (United States)

Straub, Anthony P; Elimelech, Menachem

2017-11-07

Low-grade heat energy from sources below 100 °C is available in massive quantities around the world, but cannot be converted to electricity effectively using existing technologies due to variability in the heat output and the small temperature difference between the source and environment. The recently developed thermo-osmotic energy conversion (TOEC) process has the potential to harvest energy from low-grade heat sources by using a temperature difference to create a pressurized liquid flux across a membrane, which can be converted to mechanical work via a turbine. In this study, we perform the first analysis of energy efficiency and the expected performance of the TOEC technology, focusing on systems utilizing hydrophobic porous vapor-gap membranes and water as a working fluid. We begin by developing a framework to analyze realistic mass and heat transport in the process, probing the impact of various membrane parameters and system operating conditions. Our analysis reveals that an optimized system can achieve heat-to-electricity energy conversion efficiencies up to 4.1% (34% of the Carnot efficiency) with hot and cold working temperatures of 60 and 20 °C, respectively, and an operating pressure of 5 MPa (50 bar). Lower energy efficiencies, however, will occur in systems operating with high power densities (>5 W/m 2 ) and with finite-sized heat exchangers. We identify that the most important membrane properties for achieving high performance are an asymmetric pore structure, high pressure resistance, a high porosity, and a thickness of 30 to 100 μm. We also quantify the benefits in performance from utilizing deaerated water streams, strong hydrodynamic mixing in the membrane module, and high heat exchanger efficiencies. Overall, our study demonstrates the promise of full-scale TOEC systems to extract energy from low-grade heat and identifies key factors for performance optimization moving forward.

Use of heat from the drainage water at the southern end of the Gotthard low-level rail tunnel - Feasibility study, phase II; Waermenutzung Tunnelwasser Basistunnel Gotthard, Suedportal. Machbarkeitsstudie Phase II

Energy Technology Data Exchange (ETDEWEB)

Dups, Ch.

2004-07-01

This final report for the Swiss Federal Office of Energy (SFOE) discusses the possibilities of using the drainage water at the southern end of the Gotthard low-level railway tunnel in Switzerland as a source of heat for several possible projects. The drainage water, estimated at 80 - 460 litres per second at a temperature of 30 - 35 {sup o}C, could possibly be used for heating greenhouses, providing a combined tropical greenhouse and fish farm, heating a wellness-spa, or for district heating or the heating of particular buildings. The thermal use of the water and its further use as drinking water is also considered. Figures on energy yields and costs are presented and estimates of the savings in fossil fuels and carbon dioxide emissions are quoted.

Study on the simulation of heat pump heating and cooling systems to hospital building

International Nuclear Information System (INIS)

Choi, Young Don; Han, Seong Ho; Cho, Sung Hwan; Kim, Du Sung; Um, Chul Jun

2008-01-01

In Korea, air source heat pump system is less efficient than conventional heat source facilities, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large hospital building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller and heater

Low grade heat driven adsorption system for cooling and power generation using advanced adsorbent materials

International Nuclear Information System (INIS)

Al-Mousawi, Fadhel Noraldeen; Al-Dadah, Raya; Mahmoud, Saad

2016-01-01

Highlights: • Adsorption system based on water and advanced physical adsorbents has the potential of producing cooling and power. • Adding an expander to physisorption system enhances efficiency by up to 11%. • MIL101Cr MOF can produce 95 W/kg and 1357 W/kg of specific power and cooling. • AQSOA Z02 can produce 73 W/kg and 640 W/kg of specific power and cooling. - Abstract: Globally there is abundance of low grade heat sources (around 150 °C) from renewables like solar energy or from industrial waste heat. The exploitation of such low grade heat sources will reduce fossil fuel consumption and CO_2 emissions. Adsorption technology offers the potential of using such low grade heat to generate cooling and power. In this work, the effect of using advanced adsorbent materials like AQSOA-Z02 (SAPO-34) zeolite and MIL101Cr Metal Organic Framework (MOF) at various operating conditions on power and cooling performance compared to that of commonly used silica-gel was investigated using water as refrigerant. A mathematical model for a two bed adsorption cooling cycle has been developed with the cycle modified to produce power by incorporating an expander between the desorber and the condenser. Results show that it is possible to produce power and cooling at the same time without affecting the cooling output. Results also show that for all adsorbents used as the heat source temperature increases, the cooling effect and power generated increase. As for increasing the cold bed temperature, this will decrease the cooling effect and power output except for SAPO-34 which shows slightly increasing trend of cooling and power output. As the condenser cooling temperature increases, the cooling effect and power output will decrease while for the chilled water temperature, the cooling load and power generated increased as the temperature increased. The maximum values of average specific power generation (SP), specific cooling power (SCP) and cycle efficiency are 73 W

In situ study of the effect of ground source heat pump on shallow ground-water quality in the late Pleistocene terrace area of Tokyo, Japan

Science.gov (United States)

Takemura, T.; Uemura, K.; Akiba, Y.; Ota, M.

2015-12-01

The implementation of ground source heat pump (GSHP) systems has rapidly increased around the world, since they reduce carbon dioxide emissions and save electric energy. The GSHP system transfer heat into the geosphere zone when air conditioners are used to cool rooms or buildings. However, the effects of temperature increase on the quality of underground water has yet to be fully investigated. In order to reduce the risks of ground-water pollution by the installed GSHPs, it is important to evaluate the effect of temperature change on the ground-water quality. In this study, we installed a closed loop GSHP system on a heat exchange well along with a monitoring well drilled to measure ground-water quality and temperature. The monitoring well was drilled at 0.1cm away from the heat exchange well. We observed that changes of temperature in the heat exchange well affected the water quality, especially turbidity, in gravelly layer.

The annual number of days that solar heated water satisfies a specified demand temperature

Energy Technology Data Exchange (ETDEWEB)

Yohanis, Y.G. [Thermal Systems Engineering Group, Faculty of Engineering, University of Ulster, BT37 0QB Northern Ireland (United Kingdom); Popel, O.; Frid, S.E. [Non-traditional Renewable Energy Sources, Institute for High Temperatures, Russian Academy of Sciences, 13/19 Izhorskaya str., IVTAN, Moscow 127412 (Russian Federation); Norton, B. [Dublin Institute of Technology, Aungier Street, Dublin 2 (Ireland)

2006-08-15

An analysis of solar water heating systems determines the number of days in each month when solar heated water wholly meets demand above a set temperature. The approach has been used to investigate the potential contribution to water heating loads of solar water heating in two UK locations. Correlations between the approach developed and the use of solar fractions are discussed. (author)

Water and sediment temperature dynamics in shallow tidal environments: The role of the heat flux at the sediment-water interface

Science.gov (United States)

Pivato, M.; Carniello, L.; Gardner, J.; Silvestri, S.; Marani, M.

2018-03-01

In the present study, we investigate the energy flux at the sediment-water interface and the relevance of the heat exchanged between water and sediment for the water temperature dynamics in shallow coastal environments. Water and sediment temperature data collected in the Venice lagoon show that, in shallow, temperate lagoons, temperature is uniform within the water column, and enabled us to estimate the net heat flux at the sediment-water interface. We modeled this flux as the sum of a conductive component and of the solar radiation reaching the bottom, finding the latter being negligible. We developed a "point" model to describe the temperature dynamics of the sediment-water continuum driven by vertical energy transfer. We applied the model considering conditions characterized by negligible advection, obtaining satisfactory results. We found that the heat exchange between water and sediment is crucial for describing sediment temperature but plays a minor role on the water temperature.

Researching of the possibility of using absorption heat exchangers for creating the low return temperature heat supply systems based on CHP generation

Science.gov (United States)

Yavorovsky, Y. V.; Malenkov, A. S.; Zhigulina, Y. V.; Romanov, D. O.; Kurzanov, S. Y.

2017-11-01

This paper deals with the variant of modernization of the heat point within urban heat supply network in order to create the system of heat and cold supply on its basis, providing the suppliers with heat in cold months and with heat and cold in warm months. However, in cold months in the course of heating system operation, the reverse delivery water temperature is maintained below 40 °C. The analysis of heat and power indicators of the heat and cold supply system under different operating conditions throughout the year was conducted. The possibility to use the existing heat networks for the cold supply needs was estimated. The advantages of the system over the traditional heat supply systems that use Combined Heat and Power (CHP) plant as a heat source as exemplified by heat supply system from CHP with ST-80 turbine were demonstrated.

Absorption cooling sources atmospheric emissions decrease by implementation of simple algorithm for limiting temperature of cooling water

Science.gov (United States)

Wojdyga, Krzysztof; Malicki, Marcin

2017-11-01

Constant strive to improve the energy efficiency forces carrying out activities aimed at reduction of energy consumption hence decreasing amount of contamination emissions to atmosphere. Cooling demand, both for air-conditioning and process cooling, plays an increasingly important role in the balance of Polish electricity generation and distribution system in summer. During recent years' demand for electricity during summer months has been steadily and significantly increasing leading to deficits of energy availability during particularly hot periods. This causes growing importance and interest in trigeneration power generation sources and heat recovery systems producing chilled water. Key component of such system is thermally driven chiller, mostly absorption, based on lithium-bromide and water mixture. Absorption cooling systems also exist in Poland as stand-alone systems, supplied with heating from various sources, generated solely for them or recovered as waste or useless energy. The publication presents a simple algorithm, designed to reduce the amount of heat for the supply of absorption chillers producing chilled water for the purposes of air conditioning by reducing the temperature of the cooling water, and its impact on decreasing emissions of harmful substances into the atmosphere. Scale of environmental advantages has been rated for specific sources what enabled evaluation and estimation of simple algorithm implementation to sources existing nationally.

On the low-temperature specific heat of icosahedral and decagonal quasicrystals

International Nuclear Information System (INIS)

Chernikov, M.A.

2005-01-01

Calorimetric experiments on icosahedral (Al-Re-Pd, Al-Mn-Pd) and decagonal (Al-Cu-Co, Al-Ni-Co) quasicrystals are described. For quasicrystals of both classes, the coefficient γ of the linear term to the specific heat falls into the range of 0.1-0.6 mJ/g-atom K 2 indicating a low density of energy states at Fermi level. For icosahedral Al-Mn-Pd, the cubic-in-temperature term to the specific heat is distinctly larger than the estimated contribution of long-wave acoustic excitations. On the contrary, the magnitude of the cubic-in-temperature term to the specific heat of decagonal Al-Ni-Co is in agreement,within the experimental accuracy, with the Debye acoustic contribution from the results of low-temperature measurements of the elastic modules [ru

Crystallization Analysis and Control of Ammonia-Based Air Source Absorption Heat Pump in Cold Regions

Directory of Open Access Journals (Sweden)

Wei Wu

2013-01-01

Full Text Available Energy consumption of heating and domestic hot water is very high and will keep increasing. Air source absorption heat pump (ASAHP was proposed to overcome the problems of low energy efficiency and high air pollution existing in boiler systems, as well as the problem of bad performance under low ambient temperatures for electrical heat pumps. In order to investigate the crystallization possibility of ammonia-salt ASAHP, crystallization margin (evaluated by solution mass concentration at generating temperature ranging from 100 to 150°C, evaporating temperature from −30 to 10°C, and condensing temperature from 30 to 65°C are analyzed. To prevent the NH3–NaSCN solution from crystallizing, ASAHP integrated with pressure booster located between the evaporator and absorber is simulated. Analysis and comparisons show that NH3–NaSCN is easy to crystallize at relatively high generating temperature, low evaporating temperature, and low condensing temperature. But crystallization margin of NH3–LiNO3 can always stay above 5% for most conditions, keeping away from crystallization. Pressure booster can effectively avoid the crystallization problem that will take place in the NH3–NaSCN ASAHP system.

A feasible system integrating combined heating and power system with ground-source heat pump

International Nuclear Information System (INIS)

Li, HongQiang; Kang, ShuShuo; Yu, Zhun; Cai, Bo; Zhang, GuoQiang

2014-01-01

A system integrating CHP (combined heating and power) subsystem based on natural gas and GSHP (ground-source heat pump subsystem) in series is proposed. By help of simulation software-Aspen Plus, the energy performance of a typical CHP and GSHP-S (S refers to ‘in series’) system was analyzed. The results show that the system can make a better use of waste heat in flue gas from CHP (combined heating and power subsystem). The total system energy efficiency is 123% and the COP (coefficient of performance) of GSHP (ground-source heat pump) subsystem is 5.3. A referenced CHP and GSHP-P (P refers to ‘in parallel’) system is used for comparison; its total system energy efficiency and COP of GSHP subsystem are 118.6% and 3.5 respectively. Compared with CHP and GSHP-P system with different operating parameters, the CHP and GSHP-S system can increase total system energy efficiency by 0.8–34.7%, with related output ratio of heat to power (R) from 1.9 to 18.3. Furthermore, the COP of GSHP subsystem can be increased between the range 3.6 and 6, which is much higher than that in conventional CHP and GSHP-P system. This study will be helpful for other efficient GSHP systems integrating if there is waste heat or other heat resources with low temperature. - Highlights: • CHP system based on natural gas and ground source heat pump. • The new system can make a better utilization of waste heat in flue gas by a special way. • The proposed system can realize energy saving potential from 0.8 to 34.7%. • The coefficient of performance of ground source heat pump subsystem is significantly improved from 3.5 to 3.6–6. • Warm water temperature and percentage of flue gas used to reheat are key parameters

A Direct Heat Exchanger Unit used for Domestic Hot Water Supply in a Single-family House Supplied by Low Energy District Heating

DEFF Research Database (Denmark)

Brand, Marek; Thorsen, Jan Eric; Svendsen, Svend

2010-01-01

The increasing number of new and renovated buildings with reduced heating requirements will soon make traditional District Heating (DH) systems uneconomic. To keep DH competitive in the future, the heat loss in DH networks needs to be reduced. One option is to reduce the supply temperature of DH...... as much as possible. This requires a review of the behaviour of the whole domestic hot water (DHW) supply system with focus on the user comfort and overall costs. This paper describes some practical approaches to the implementation of this Low Energy District Heating (LEDH) concept. It reports...... on the testing of the dynamic behaviour of an Instantaneous Heat Exchanger Unit(IHEU) designed for DHW heating and space heating in detached family houses supplied by LEDH ensuring an entry-to-substation temperature of 51 °C. We measured the time it takes for the IHEU to produce DHW with a temperature of 42 °C...

Ground Source Geothermal District Heating and Cooling System

Energy Technology Data Exchange (ETDEWEB)

Lowe, James William [Ball State Univ., Muncie, IN (United States)

2016-10-21

Ball State University converted its campus from a coal-fired steam boiler district heating system to a ground source heat pump geothermal district system that produces simultaneously hot water for heating and chilled water for cooling. This system will include the installation of 3,600 four hundred feet deep vertical closed loop boreholes making it the largest ground source geothermal district system in the country. The boreholes will act as heat exchangers and transfer heat by virtue of the earth’s ability to maintain an average temperature of 55 degree Fahrenheit. With growing international concern for global warming and the need to reduce worldwide carbon dioxide loading of the atmosphere geothermal is poised to provide the means to help reduce carbon dioxide emissions. The shift from burning coal to utilizing ground source geothermal will increase electrical consumption but an overall decrease in energy use and reduction in carbon dioxide output will be achieved. This achievement is a result of coupling the ground source geothermal boreholes with large heat pump chiller technology. The system provides the thermodynamic means to move large amounts of energy with limited energy input. Ball State University: http://cms.bsu.edu/About/Geothermal.aspx

Heat of fusion storage systems for combined solar systems in low energy buildings

DEFF Research Database (Denmark)

Schultz, Jørgen Munthe; Furbo, Simon

2004-01-01

Solar heating systems for combined domestic hot water and space heating has a large potential especially in low energy houses where it is possible to take full advantage of low temperature heating systems. If a building integrated heating system is used – e.g. floor heating - the supply temperature...... from solid to liquid form (Fig. 1). Keeping the temperature as low as possible is an efficient way to reduce the heat loss from the storage. Furthermore, the PCM storage might be smaller than the equivalent water storage as more energy can be stored per volume. If the PCM further has the possibility...... systems through further improvement of water based storages and in parallel to investigate the potential of using storage designs with phase change materials, PCM. The advantage of phase change materials is that large amounts of energy can be stored without temperature increase when the material is going...

Seasonal coefficient of performance for ground source heat pump and groundwater one in Białystok

Science.gov (United States)

Gajewski, Andrzej

2017-11-01

European Economic Area (EEA) states declare to contain greenhouse gases emissions at 20% by 2020, whereas European Union (EU) does 40% before 2030, which result in encouragement to apply low-carbon technologies. Coefficient of Performance (COP) and Seasonal Coefficient of Performance (SCOPnet) are obtained using temperature measurement done by The Institute of Meteorology and Water Management - National Research Institute (IMGW-PIB) at the weather station in Bialystok for ten-year period. The first variant is ground source heat pump (GSHP) and the second one is groundwater source heat pump (WSHP) which can be equipped with separating heat exchanger (SHE) optionally. In both cases heat is generated for heating system only. Ground temperature is determined from Baggs (1983) formula using Oleśkowicz-Popiel et. al. (2002) adaptation to Polish climate and substituting the local constants achieved by Biernacka (2010). Water temperature in a groundwater basin is obtained from Kowalski (2007) equation. Estimation is done in each hour of heating season. All COP values are higher than 3.5 required by EU (2013). SCOPnet are as follows: 6.12, 5.86, 5.03 for WSHP, WSHP+SHE, GSHP respectively. Insomuch as WSHP needs only two boreholes it is recommended to the areas beneath ones a groundwater basin is located.

Seasonal coefficient of performance for ground source heat pump and groundwater one in Białystok

Directory of Open Access Journals (Sweden)

Gajewski Andrzej

2017-01-01

Full Text Available European Economic Area (EEA states declare to contain greenhouse gases emissions at 20% by 2020, whereas European Union (EU does 40% before 2030, which result in encouragement to apply low-carbon technologies. Coefficient of Performance (COP and Seasonal Coefficient of Performance (SCOPnet are obtained using temperature measurement done by The Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB at the weather station in Bialystok for ten-year period. The first variant is ground source heat pump (GSHP and the second one is groundwater source heat pump (WSHP which can be equipped with separating heat exchanger (SHE optionally. In both cases heat is generated for heating system only. Ground temperature is determined from Baggs (1983 formula using Oleśkowicz-Popiel et. al. (2002 adaptation to Polish climate and substituting the local constants achieved by Biernacka (2010. Water temperature in a groundwater basin is obtained from Kowalski (2007 equation. Estimation is done in each hour of heating season. All COP values are higher than 3.5 required by EU (2013. SCOPnet are as follows: 6.12, 5.86, 5.03 for WSHP, WSHP+SHE, GSHP respectively. Insomuch as WSHP needs only two boreholes it is recommended to the areas beneath ones a groundwater basin is located.

Space heating with ultra-low-temperature district heating - A case study of four single-family houses from the 1980s

DEFF Research Database (Denmark)

Østergaard, Dorte Skaarup; Svendsen, Svend

. These benefits can be maximized if district heating temperatures are lowered as much as possible. In this paper we report on a project where 18 Danish single-family houses from the 1980s were supplied by ultra-low-temperature district heating with a supply temperature as low as 45 °C for the main part...... the four houses were modelled in the building simulation tool IDA ICE. The simulation models included the actual radiator sizes and the models were used to simulate the expected thermal comfort in the houses and resulting district heating return temperatures. Secondly measurements of the actual district...... heating return temperatures in the houses were analysed for different times of the year. The study found that existing Danish single-family houses from the 1980s can be heated with supply temperatures as low as 45 °C for the main part of the year. Both simulation models and test measurements showed...

Composting as a source of thermal energy for water heating in aquaculture; Compostagem como fonte termica de energia para aquecimento de agua na agricultura

Energy Technology Data Exchange (ETDEWEB)

Souza, Samuel Nelson Melegari de; Neitzke, Guilherme; Hermes, Cesar Ademar [Universidade Estadual do Oeste do Parana (UNIOESTE/CCET), Cascavel, PR (Brazil). Centro de Ciencias Exatas. Programa Institucional de Bolsas de Iniciacao Cientifica], Emails: ssouza@unioeste.br, guilherme_neitzke@yahoo.com.br, cahermes@ibestvip.com.br

2006-07-01

The objective of the work is to use the composting as thermal energy source in the maintenance of aquatic organisms. The area of Toledo has annual medium temperature of the air of 20,5 deg C and average in the hottest quarter of 27 deg C and in the more cold of 16,5 deg C. The used experimental material consisted of boxes of water, pipes of aluminum, hay of grassy, manure of birds and swine, aquarium compressors, hoses and pipes, porous stones, fish lingers and thermometer. The temperatures of the air, the composition and the water without heating were monitored. The medium temperatures obtained were of 20,9 and 31,1 deg C, for the air and the composition, respectively. The averages of temperature of the water with heating and without heating were of 22,0 deg C and 20,0 deg C. The weight difference among the fish lingers was of 24,0 %. It is ended that the composting can be a thermal source of energy in the aquaculture. (author)

Heat flow and subsurface temperature as evidence for basin-scale ground-water flow, North Slope of Alaska

Science.gov (United States)

Deming, D.; Sass, J.H.; Lachenbruch, A.H.; De Rito, R. F.

1992-01-01

Several high-resolution temperature logs were made in each of 21 drillholes and a total of 601 thermal conductivity measurements were made on drill cuttings and cores. Near-surface heat flow (??20%) is inversely correlated with elevation and ranges from a low of 27 mW/m2 in the foothills of the Brooks Range in the south, to a high of 90 mW/m2 near the north coast. Subsurface temperatures and thermal gradients estimated from corrected BHTs are similarly much higher on the coastal plain than in the foothills province to the south. Significant east-west variation in heat flow and subsurface temperature is also observed; higher heat flow and temperature coincide with higher basement topography. The observed thermal pattern is consistent with forced convection by a topographically driven ground-water flow system. Average ground-water (Darcy) velocity in the postulated flow system is estimated to be of the order of 0.1 m/yr; the effective basin-scale permeability is estimated to be of the order of 10-14 m2. -from Authors

Medium Deep High Temperature Heat Storage

Science.gov (United States)

Bär, Kristian; Rühaak, Wolfram; Schulte, Daniel; Welsch, Bastian; Chauhan, Swarup; Homuth, Sebastian; Sass, Ingo

2015-04-01

Heating of buildings requires more than 25 % of the total end energy consumption in Germany. Shallow geothermal systems for indirect use as well as shallow geothermal heat storage systems like aquifer thermal energy storage (ATES) or borehole thermal energy storage (BTES) typically provide low exergy heat. The temperature levels and ranges typically require a coupling with heat pumps. By storing hot water from solar panels or thermal power stations with temperatures of up to 110 °C a medium deep high temperature heat storage (MDHTS) can be operated on relatively high temperature levels of more than 45 °C. Storage depths of 500 m to 1,500 m below surface avoid conflicts with groundwater use for drinking water or other purposes. Permeability is typically also decreasing with greater depth; especially in the crystalline basement therefore conduction becomes the dominant heat transport process. Solar-thermal charging of a MDHTS is a very beneficial option for supplying heat in urban and rural systems. Feasibility and design criteria of different system configurations (depth, distance and number of BHE) are discussed. One system is designed to store and supply heat (300 kW) for an office building. The required boreholes are located in granodioritic bedrock. Resulting from this setup several challenges have to be addressed. The drilling and completion has to be planned carefully under consideration of the geological and tectonical situation at the specific site.

Comparison of Low-temperature District Heating Concepts in a Long-Term Energy System Perspective

DEFF Research Database (Denmark)

Lund, Rasmus Søgaard; Østergaard, Dorte Skaarup; Yang, Xiaochen

2017-01-01

renewable energy systems. This study compares three alternative concepts for DH temperature level: Low temperature (55/25 °C), Ultra-low temperature with electric boosting (45/25 °C), and Ultra-low temperature with heat pump boosting (35/20 °C) taking into account the grid losses, production efficiencies......District heating (DH) systems are important components in an energy efficient heat supply. With increasing amounts of renewable energy, the foundation for DH is changing and the approach to its planning will have to change. Reduced temperatures of DH are proposed as a solution to adapt it to future...... and building requirements. The scenarios are modelled and analysed in the analysis tool EnergyPLAN and compared on primary energy supply and socioeconomic costs. The results show that the low temperature solution (55/25°C) has the lowest costs, reducing the total costs by about 100 M€/year in 2050....

The Misselhorn Cycle: Batch-Evaporation Process for Efficient Low-Temperature Waste Heat Recovery

Directory of Open Access Journals (Sweden)

Moritz Gleinser

2016-05-01

Full Text Available The concept of the Misselhorn cycle is introduced as a power cycle that aims for efficient waste heat recovery of temperature sources below 100 °C. The basic idea shows advantages over a standard Organic Rankine Cycle (ORC in overall efficiency and utilization of the heat source. The main characteristic of this cycle is the use of at least three parallel batch evaporators instead of continuous heat exchangers. The operational phases of the evaporators are shifted so that there is always one vaporizer in discharge mode. A transient MATLAB® model (The MathWorks: Natick, MA, USA is used to simulate the achievable performance of the Misselhorn cycle. The calculations of the thermodynamic states of the system are based on the heat flux, the equations for energy conservation and the equations of state found in the NIST Standard Reference Database 23 (Reference Fluid Thermodynamic and Transport Properties - REFPROP, National Institute of Standards and Technology: Gaithersburg, MD, USA. In the isochoric batch evaporation, the pressure and the corresponding boiling temperature rise over time. With a gradually increasing boiling temperature, no pinch point limitation occurs. Furthermore, the heat source medium is passed through the evaporators in serial order to obtain a quasi-counter flow setup. It could be shown that these features offer the possibility to gain both high thermal efficiencies and an enhanced utilization of the heat source at the same time. A basic model with a fixed estimated heat transfer coefficient promises a possible system exergy efficiency of 44.4%, which is an increase of over 60% compared to a basic ORC with a system exergy efficiency of only 26.8%.

Containment for low temperature district nuclear-heating reactor

International Nuclear Information System (INIS)

He Shuyan; Dong Duo

1992-03-01

Integral arrangement is adopted for Low Temperature District Nuclear-heating Reactor. Primary heat exchangers, control rod drives and spent fuel elements are put in the reactor pressure vessel together with reactor core. Primary coolant flows through reactor core and primary heat exchangers in natural circulation. Primary coolant pipes penetrating the wall of reactor pressure vessel are all of small diameters. The reactor vessel constitutes the main part of pressure boundary of primary coolant. Therefore the small sized metallic containment closed to the wall of reactor vessel can be used for the reactor. Design principles and functions of the containment are as same as the containment for PWR. But the adoption of small sized containment brings about some benefits such as short period of manufacturing, relatively low cost, and easy for sealing. Loss of primary coolant accident would not be happened during the rupture accident of primary coolant pressure boundary inside the containment owing to its intrinsic safety

High temperature heat pipe experiments in low earth orbit

International Nuclear Information System (INIS)

Woloshun, K.; Merrigan, M.A.; Sena, J.T.; Critchley, E.

1993-01-01

Although high temperature, liquid metal heat pipe radiators have become a standard component on most high power space power system designs, there is no experimental data on the operation of these heat pipes in a zero gravity or micro-gravity environment. Experiments to benchmark the transient and steady state performance of prototypical heat pipe space radiator elements are in preparation for testing in low earth orbit. It is anticipated that these heat pipes will be tested aborad the Space Shuttle in 1995. Three heat pipes will be tested in a cargo bay Get Away Special (GAS) canister. The heat pipes are SST/potassium, each with a different wick structure; homogeneous, arterial, and annular gap, the heat pipes have been designed, fabricated, and ground tested. In this paper, the heat pipe designs are specified, and transient and steady-state ground test data are presented

Experimental and theoretic investigations of thermal behavior of a seasonal water pit heat storage

DEFF Research Database (Denmark)

Fan, Jianhua; Huang, Junpeng; Chatzidiakos, Angelos

Seasonal heat storages are considered essential for district heating systems because they offer flexibility for the system to integrate different fluctuating renewable energy sources. Water pit thermal storages (PTES) have been successfully implemented in solar district heating plants in Denmark....... Thermal behavior of a 75,000 m3 water pit heat storage in Marstal solar heating plant was investigated experimentally and numerically. Temperatures at different levels of the water pit storage and temperatures at different depths of the ground around the storage were monitored and analyzed. A simulation...... model of the water pit storage is built to investigate development of temperatures in and around the storage. The calculated temperatures are compared to the monitored temperatures with an aim to validate the simulation model. Thermal stratification in the water pit heat storage and its interaction...

Method and installation for the production of heat energy at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Prost, R; Broche, J

1976-07-08

The invention concerns a refrigeration source, whose temperature ajusts itself to a pre-set and definite value. The equipment includes two regenerators, whose refrigeration ends are connected to each other by a canal, which has a calibrated reduced section. The refrigeration ends and their connection are inserted into a copper block, which acts as the refrigeration source. The heating end of the lst regenerator is joined to the suction side of a compressor over a switchable valve, while the front side of the compressor is joined to the heating end of the 2nd regenerator over a exchanger and again a switchable valve; when the valve is switched the regenerators are joined to the circuit in an opposite way. The other side of the heat exchanger is, for example, flowed through by tap water for the purpose of cooling. The circuit described is charged with a gas mixture, which consists of hydrocarbon with different boiling points, and, when necessary, consisting of a nitrogen portion. Thus, the gas charge is led from the regenerator, under pressure, into the second one, where condenses by graduation from heat end to refriguration end. The valves are switched back as soon as the initial pressure of the gas has reached a reference value. For this purpose a pressure measuring sensor is provided, which activates a control device, i.e. an electronic control device, which is the main item of this invention.

Technical and economic working domains of industrial heat pumps: Part 2 - ammonia-water hybrid absorption-compression heat pumps

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix

2015-01-01

The ammonia-water hybrid absorption-compression heat pump (HACHP) has been proposed as a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase...... change of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best available...... vapour compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 150 °C and temperature lifts...

Technical and Economic Working Domains of Industrial Heat Pumps: Part 2 - Ammonia-Water Hybrid Absorption-Compression Heat Pumps

DEFF Research Database (Denmark)

Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix

2014-01-01

The ammonia-water hybrid absorption-compression heat pump (HACHP) is a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase change...... of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best possible vapour...... compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 140 XC and temperature lifts up to 60 K...

A hybrid geothermal energy conversion technology: Auxiliary heating of geothermally preheated water or CO2 - a potential solution for low-temperature resources

Science.gov (United States)

Saar, Martin; Garapati, Nagasree; Adams, Benjamin; Randolph, Jimmy; Kuehn, Thomas

2016-04-01

compare over a range of parameters the net power and efficiencies of hybrid geothermal power plants that use brine or CO2 as the subsurface working fluid, that are then heated further with a secondary energy source that is unspecified here. Parameters varied include the subsurface working fluid (brine vs. CO2), geothermal reservoir depth (2.5-4.5 km), and turbine inlet temperature (200-600°C) after auxiliary heating. The hybrid power plant is numerically modeled using an iterative coupling approach of TOUGH2-ECO2N/ECO2H (Pruess, 2004) for simulation of the subsurface reservoir and Engineering Equation Solver for well bore fluid flow and surface power plant performance. We find that hybrid power plants that are CO2-based (subsurface) systems produce more net power than the sum of the power produced by individual power plants at low turbine inlet temperatures and brine based systems produce more power at high turbine inlet temperatures. Specifically, our results indicate that geothermal hybrid plants that are CO2-based are more efficient than brine-based systems when the contribution of the geothermal resource energy is higher than 48%.

The potential to supply low temperature district heating to existing building area

DEFF Research Database (Denmark)

Li, Hongwei; Svendsen, Svend

2013-01-01

Low-temperature district heating (LTDH) has the advantages as reduced network heat loss, improved quality match between energy supply and energy demand, and increased utilization of low-grade waste heat and renewable energy. The LTDH represents the next generation district heating (DH) system...... to supply existing building areas which are characterized with high heating demand needs to be examined. In this paper, the DH network deliverable capacity to supply LTDH to an existing building area is studied based on building thermal performance and DH network hydraulic performance simulation....

Simulation and optimisation of a ground source heat pump with different ground heat exchanger configurations for a single-family residential house

DEFF Research Database (Denmark)

Pavlov, Georgi Krasimiroy; Olesen, Bjarne W.

2012-01-01

In the future there will be an increased demand for energy efficient cooling of residential buildings. Therefore it is essential to develop cooling concepts that are passive and/or using very little primary energy. A possible solution is a ground source heat pump combined with a low-temperature h....... For the studied geographical location, passive cooling by bypassing the heat pump and using only the ground heat exchanger can provide acceptable room temperatures.......In the future there will be an increased demand for energy efficient cooling of residential buildings. Therefore it is essential to develop cooling concepts that are passive and/or using very little primary energy. A possible solution is a ground source heat pump combined with a low......-temperature heating and high-temperature cooling system. The present work evaluates the performance in relation to thermal comfort and energy consumption of a GSHP with different GHE concepts. The different configurations are analyzed being part of the energy supply system of a low-energy residential house...

Low temperature barrier wellbores formed using water flushing

Science.gov (United States)

McKinzie, II; John, Billy [Houston, TX; Keltner, Thomas Joseph [Spring, TX

2009-03-10

A method of forming an opening for a low temperature well is described. The method includes drilling an opening in a formation. Water is introduced into the opening to displace drilling fluid or indigenous gas in the formation adjacent to a portion of the opening. Water is produced from the opening. A low temperature fluid is applied to the opening.

A parametric study of a humidification dehumidification (HDH) desalination system using low grade heat sources

International Nuclear Information System (INIS)

He, W.F.; Han, D.; Yue, C.; Pu, W.H.

2015-01-01

Highlights: • The HDH desalination system coupling with the waste heat plate LGHC is proposed. • Performance of the desalination system and the plate LGHC is presented. • Influence from the operation pressure on the system performance is investigated. • Gained investment ratio is proposed to characterize the desalination system consumption. - Abstract: Humidification dehumidification (HDH) desalination system is applicable to recover the low grade heat source to heat the seawater before the humidifier. In the paper, plate heat exchangers are integrated to recover the waste heat from the exhaust in the water heated closed air open water (CAOW) HDH desalination system. The performance of the HDH desalination system as well as the plate type of low grade heat collector (LGHC) is investigated at different operation pressures. Gain investment ratio (GIR) is proposed and defined to depict the overall consumption of the whole system. The simulation results show that the modified heat capacity ratio of the dehumidifier (HCRd) is vital for the performance of the HDH desalination system as well as the plate LGHC with a top value of gain output ratio (GOR) at the balance point, HCRd = 1, and the maximum GOR, GOR = 2.44, results from the raised pressure of p = 0.15 MPa. Furthermore, taking the cost for the heat transfer surface area of the LGHC and the air and seawater pipes into consideration, it is revealed that the conditions, HCRd > 1, are more economical due to the increase of GIR, which indicates the profit of unit consumption is more significant.

Potential market and characteristics of low-temperature reactors

International Nuclear Information System (INIS)

Lerouge, B.

1975-01-01

The low-temperature (100 to 200 deg C) heat market for industrial applications and district heating is very important. Two main studies have been developed: a swimming pool reactor delivering water at 110 deg C and a prestressed concrete vessel reactor delivering water at 200 deg C [fr

Technical Analysis of Organic Rankine Cycle System Using Low-Temperature Source to Generate Electricity in Ship

Directory of Open Access Journals (Sweden)

Akram Faisal

2017-01-01

Full Text Available Nowadays, the shipping sector has growth rapidly as followed by the increasing of world population and the demands for public transportation via sea. This issue entails the large attention on emission, energy efficiency and fuel consumption on the ship. Waste Heat Recovery (WHR is one of the solution to overcome the mentioned issue and one of the WHR method is by installing Organic Rankine Cycle (ORC system in ship. ORC demonstrate to recover and exploit the low temperature waste heat rejected by the ship power generation plant. The main source of heat to be utilized is obtained from container ship (7900 kW BHP, DWT 10969 mt ship jacket water cooling system and use R-134a as a refrigerant. The main equipment consists of evaporator, condenser, pump and steam turbine to generate the electricity. The main objective is to quantifying the estimation of electrical power which can be generated at typical loads of the main engine. As the final result of analysis, the ORC system is able to generate the electricity power ranged from 77,5% - 100% of main engine load producing power averagely 57,69 kW.

Thermodynamic modelling of a recompression CO_2 power cycle for low temperature waste heat recovery

International Nuclear Information System (INIS)

Banik, Shubham; Ray, Satyaki; De, Sudipta

2016-01-01

Highlights: • Thermodynamic model for recompression T-CO_2 is developed. • Energetic and exergetic analysis compared with S-CO_2 and Reg. Brayton cycle. • Maximum efficiency of 13.6% is obtained for T-CO_2 cycle. • Optimum recompression ratio of 0.48 is obtained for minimum irreversibility. • Reg. Brayton has better efficiency, T-CO_2 offers minimum irreversibility. - Abstract: Due to the rising prices of conventional fossil fuels, increasing the overall thermal efficiency of a power plant is essential. One way of doing this is waste heat recovery. This recovery is most difficult for low temperature waste heat, below 240 °C, which also covers majority of the waste heat source. Carbon dioxide, with its low critical temperature and pressure, offers an advantage over ozone-depleting refrigerants used in Organic Rankine Cycles (ORCs) and hence is most suitable for the purpose. This paper introduces parametric optimization of a transcritical carbon dioxide (T-CO_2) power cycle which recompresses part of the total mass flow of working fluid before entering the precooler, thereby showing potential for higher cycle efficiency. Thermodynamic model for a recompression T-CO_2 power cycle has been developed with waste heat source of 2000 kW and at a temperature of 200 °C. Results obtained from this model are analysed to estimate effects on energetic and exergetic performances of the power cycle with varying pressure and mass recompression ratio. Higher pressure ratio always improves thermodynamic performance of the cycle – both energetic and exergetic. Higher recompression ratio also increases exergetic efficiency of the cycle. However, it increases energy efficiency, only if precooler inlet temperature remains constant. Maximum thermal efficiency of the T-CO_2 cycle with a recompression ratio of 0.26 has been found to be 13.6%. To minimize total irreversibility of the cycle, an optimum ratio of 0.48 was found to be suitable.

The future of the low temperature district heating reactor

International Nuclear Information System (INIS)

Lu Yingzhong; Wang Dazhong; Ma Changwen; Dong Duo; Tian Jiafu.

1984-01-01

In this paper, the role, development and situation of the low temperature district heating reactor (LTDHR) are briefly summarized. There are four types of LTDHR. They are PWR, reactor with boiling in the chimney, organic reactor and swimming pool reactor. The features of these reactors are introduced. The situation and role of the LTDHR in the future of the energy system are also discussed. The experiment on nuclear district heating with the swimming pool reactor in Qinghua Univ. is described briefly. (Author)

Heat transfer analysis of underground U-type heat exchanger of ground source heat pump system.

Science.gov (United States)

Pei, Guihong; Zhang, Liyin

2016-01-01

Ground source heat pumps is a building energy conservation technique. The underground buried pipe heat exchanging system of a ground source heat pump (GSHP) is the basis for the normal operation of an entire heat pump system. Computational-fluid-dynamics (CFD) numerical simulation software, ANSYS-FLUENT17.0 have been performed the calculations under the working conditions of a continuous and intermittent operation over 7 days on a GSHP with a single-well, single-U and double-U heat exchanger and the impact of single-U and double-U buried heat pipes on the surrounding rock-soil temperature field and the impact of intermittent operation and continuous operation on the outlet water temperature. The influence on the rock-soil temperature is approximately 13 % higher for the double-U heat exchanger than that of the single-U heat exchanger. The extracted energy of the intermittent operation is 36.44 kw·h higher than that of the continuous mode, although the running time is lower than that of continuous mode, over the course of 7 days. The thermal interference loss and quantity of heat exchanged for unit well depths at steady-state condition of 2.5 De, 3 De, 4 De, 4.5 De, 5 De, 5.5 De and 6 De of sidetube spacing are detailed in this work. The simulation results of seven working conditions are compared. It is recommended that the side-tube spacing of double-U underground pipes shall be greater than or equal to five times of outer diameter (borehole diameter: 180 mm).

Energy Efficiency Modelling of Residential Air Source Heat Pump Water Heater

Directory of Open Access Journals (Sweden)

Cong Toan Tran

2016-03-01

Full Text Available The heat pump water heater is one of the most energy efficient technologies for heating water for household use. The present work proposes a simplified model of coefficient of performance and examines its predictive capability. The model is based on polynomial functions where the variables are temperatures and the coefficients are derived from the Australian standard test data, using regression technics. The model enables to estimate the coefficient of performance of the same heat pump water heater under other test standards (i.e. US, Japanese, European and Korean standards. The resulting estimations over a heat-up phase and a full test cycle including a draw off pattern are in close agreement with the measured data. Thus the model allows manufacturers to avoid the need to carry out physical tests for some standards and to reduce product cost. The limitations of the methodology proposed are also discussed.

Flue gas heat recovery operating below the dew point and its utilisation for low temperature heating installations

Energy Technology Data Exchange (ETDEWEB)

Wilsdorf, J.

1986-11-01

This paper deals at first with the characteristics of two principal systems for the flue gas heat recovery by reducing the temperature below the dew point. With test results on experimental plants are shown the typical differences between surface and direct contact heat exchange. A second part informs about experiences from the application for low temperature heating installations, especially about thermodynamics condensate quality and technical design. The possible increasing of the efficiency ranges between 10 to 20 per cent.

Heat treatments and low temperature fracture toughness of a Ti-6A1-4V alloy

International Nuclear Information System (INIS)

Nagai, K.; Hiraga, K.; Ishikawa, K.; Ogata, T.

1984-01-01

Titanium alloy is one of the reliable structural materials for cryogenic use owing to its high strength, high specific strength and low thermal conductivity. Heat treatment is one method of controlling the normally poor fracture toughness of this alloy at ambient temperature. However, there have been few attempts to improve the low temperature fracture toughness by heat treatment. This study was conducted to elucidate the effects of heat treatments on the low temperature fracture toughness in a Ti-6A1-4V alloy. The effects of the heat treatments were as follows: the beta treatment was a very feasible method to improve the low temperature fracture properties; the alpha+beta treatment was favorable for the increment in the low temperature ductility but did not largely improve the fracture toughness; the double treatment yielded good ductility but was not useful for improving the fracture toughness

An Estimate of Shallow, Low-Temperature Geothermal Resources of the United States

Energy Technology Data Exchange (ETDEWEB)

Mullane, Michelle; Gleason, Michael; Reber, Tim; McCabe, Kevin; Mooney, Meghan; Young, Katherine R.

2017-05-01

Low-temperature geothermal resources in the United States potentially hold an enormous quantity of thermal energy, useful for direct use in residential, commercial and industrial applications such as space and water heating, greenhouse warming, pool heating, aquaculture, and low-temperature manufacturing processes. Several studies published over the past 40 years have provided assessments of the resource potential for multiple types of low-temperature geothermal systems (e.g. hydrothermal convection, hydrothermal conduction, and enhanced geothermal systems) with varying temperature ranges and depths. This paper provides a summary and additional analysis of these assessments of shallow (= 3 km), low-temperature (30-150 degrees C) geothermal resources in the United States, suitable for use in direct-use applications. This analysis considers six types of geothermal systems, spanning both hydrothermal and enhanced geothermal systems (EGS). We outline the primary data sources and quantitative parameters used to describe resources in each of these categories, and present summary statistics of the total resources available. In sum, we find that low-temperature hydrothermal resources and EGS resources contain approximately 8 million and 800 million TWh of heat-in-place, respectively. In future work, these resource potential estimates will be used for modeling of the technical and market potential for direct-use geothermal applications for the U.S. Department of Energy's Geothermal Vision Study.

Analysis of chiller units capacity for different heat loads considering variation of ambient air and cooling water temperature

International Nuclear Information System (INIS)

Coman, Aurelia Camelia; Tenescu, Mircea

2010-01-01

The paper purpose is to analyze the chiller units capacity to determine whether they can cope with high air and cooling water temperatures during summer time to remove heat loads imposed from Heating, Ventilation and Air Conditioning (HVAC) units in a CANDU 6 Nuclear Power Plant. The starting point is calculation of the overall heat transfer coefficient at the evaporator and condenser. They are used in heat balance equations of heat exchangers. A mathematical model was developed that simulates the refrigeration cycle to assess the response of chilled water system and its performance at different heat loads. In this analysis there were calculated values for inlet/outlet chilled water temperature and the refrigerant cycle thermodynamic parameters (condenser and evaporator pressure/temperature, refrigerant mass flowrate, refrigerant quality at the evaporator, refrigerant vapour superheated temperature at the compressor outlet, refrigerant subcooled temperature at the condenser outlet). To find the adequate functioning parameters of the installation, the MathCAD 13 software was used in all cases analyzed. The behaviour of the chiller units was investigated by examining the variation of three basic parameters, namely: - cooling water (river water) temperature; - air temperature; - heat load. The simultaneous variation of these three independent parameters allows to identify the actual chillers unit operating point (including chiller trip). (authors)

Can high temperature steam electrolysis function with geothermal heat?

International Nuclear Information System (INIS)

Sigurvinsson, J.; Mansilla, C.; Werkoff, F.; Lovera, P.

2007-01-01

It is possible to improve the performance of electrolysis processes by operating at a high temperature. This leads to a reduction in electricity consumption but requires a part of the energy necessary for the dissociation of water to be in the form of thermal energy. Iceland produces low cost electricity and very low cost geothermal heat. However, the temperature of geothermal heat is considerably lower than the temperature required at the electrolyser's inlet, making heat exchangers necessary to recuperate part of the heat contained in the gases at the electrolyser's outlet. A techno-economic optimisation model devoted to a high-temperature electrolysis (HTE) process which includes electrolysers as well as a high temperature heat exchanger network was created. Concerning the heat exchangers, the unit costs used in the model are based on industrial data. For the electrolyser cells, the unit cost scaling law and the physical sub-model we used were formulated using analogies with solid oxide fuel cells. The method was implemented in a software tool, which performs the optimisation using genetic algorithms. The first application of the method is done by taking into account the prices of electricity and geothermal heat in the Icelandic context. It appears that even with a geothermal temperature as low as 230 degrees C, the HTE could compete with alkaline electrolysis. (authors)

Heat sources for heat pumps in the energetic and economic comparison; Waermequellen fuer Waermepumpen im energetischen und wirtschaftlichen Vergleich

Energy Technology Data Exchange (ETDEWEB)

Bockelmann, Franziska; Fisch, M. Norbert; Schlosser, Mathias; Peter, Markus [Technische Univ. Braunschweig (Germany). Inst. fuer Gebaeude- und Solartechnik

2016-07-01

Because of the growing application of heat pumps also the number of potentially usable low-temperature heat sources and corresponding heat exchangers for heat-pump systems present in the market increases. Thereby products like energy fences, high-power piles, ore ice reservoir come into applications without any knowledge ab out their power or the cost-profit ratio. The optimized lay-out of the coupling to the building are however essential conditions in order to reach an energy-efficient and durable operation of the facilities. The research project ''future heat pump'' sponsored by the BMWi is dedicated to the energetic and economic evaluation of heat sources for heat pumps. In this connection a pre-check-tool for the preliminary selection of low-temperature heat sources and connected, suitable heat-exchange systems is developed and their actual status of development presented. The holistic, comparing consideration of the different heat sources and heat-exchanger systems is related among others to the power numbers of the heat pumps, the entry and withdrawal services of the heat-exchangers, and the general performance of the systems. Additionally an estimation of economic and ecologic aspects (investment and operation costs, CO{sub 2} emissions) is made. Aim is the determination of the plausibility of applications and essential boundary conditions of single source systems. For the qualitative comparison in a project-accompanying monitoring different facilities and source systems are measurement-technically comprehended.

A mathematical model for two-phase water, air, and heat flow around a linear heat source emplaced in a permeable medium

International Nuclear Information System (INIS)

Doughty, C.; Pruess, K.

1991-03-01

A semianalytical solution for transient two-phase water, air, and heat flow in a uniform porous medium surrounding a constant-strength linear heat source has been developed, using a similarity variable η=r/√t (r is radial distance, t is time). Although the similarity transformation requires a simplified radial geometry, all the physical mechanisms involved in two-phase fluid and heat flow may be taken into account in a rigorous way. The solution includes nonlinear thermophysical fluid and material properties, such as relative permeability and capillary pressure variations with saturation, and density and viscosity variations with temperature and pressure. The resulting governing equations form a set of coupled nonlinear ODEs, necessitating numerical integration. The solution has been applied to a partially saturated porous medium initially at a temperature well below the saturation temperature, which is the setting for the potential nuclear waste repository site at Yucca Mountain, Nevada. The resulting heat and fluid flows provide a stringent test of many of the capabilities of numerical simulation models, making the similarity solution a useful tool for model verification. Comparisons to date have shown excellent agreement between the TOUGH2 simulator and the similarity solution for a variety of conditions. 13 refs., 6 figs., 1 tab

Evaluation of a flue gas driven open absorption system for heat and water recovery from fossil fuel boilers

International Nuclear Information System (INIS)

Wang, Zhenying; Zhang, Xiaoyue; Li, Zhen

2016-01-01

Highlights: • Flue gas driven open absorption system that efficiently recovers total heat. • Efficient heat and water recovery for various kinds of fossil fuel boilers. • Heat and water recovery efficiencies increase with moisture content of flue gas. • Temperature requirements for district heat supply and domestic hot water were met. • Experimental system surpasses conventional condensing system in total heat recovery. - Abstract: This paper presents an open absorption system for total heat recovery from fossil fuel boilers using the high temperature flue gas as the regeneration heat source. In this system, liquid desiccant serves as the recycling medium, which absorbs waste heat and moisture contained in the low temperature flue gas in the packed tower and then regenerates in the regenerator by the high temperature flue gas. Water vapor generated in the regenerator gets condensed after releasing heat to the heating water system and the condensing water also gets recycled. The return water collects heat from the solution water heat exchanger, the flue gas water heat exchanger and the condenser respectively and is then used for district heating. Driven by the vapor pressure difference between high humidity flue gas and the liquid desiccant, the heat recovery efficiency of the system is not limited by the dew point of the flue gas, enabling a warmer water to be heated up than the conventional condensing boiler. The performance of this system was analyzed theoretically and experimentally and the results showed that the system operated well for both district heat supply and domestic hot water supply. The system efficiency increased with the moisture content of flue gas and the total heat recovery was about 8.5%, 17.2%, 21.2%, and 9.2% higher than the conventional condensing system in the case of coal fired boiler, fuel oil boiler, natural gas boiler, and coke oven gas boiler, respectively.

Fuel fired heat sources

Energy Technology Data Exchange (ETDEWEB)

Ortlinghaus, U

1977-09-08

Fuel fired heat sources with a valve-controlled ignition and main burner, whose flame is monitored and whose control valve is closed or opened by a controller according to the control deviation between actual and reference heat source temperature, previously suffered the disadvantage of high consumption of ignition gas. According to the invention this disadvantage is avoided by closing the ignition valve from the controller via a delay unit and having the delay time of the delay unit controlled either by the temperature measured by the sensor or increasing it with increasing deviation of the actual value of pre-temperature from the reference value of the pre-temperature.

Scale Resistant Heat Exchanger for Low Temperature Geothermal Binary Cycle Power Plant

Energy Technology Data Exchange (ETDEWEB)

Hays, Lance G. [Energent Corporation, Santa Ana, CA (United States)

2014-11-18

Phase 1 of the investigation of improvements to low temperature geothermal power systems was completed. The improvements considered were reduction of scaling in heat exchangers and a hermetic turbine generator (eliminating seals, seal system, gearbox, and lube oil system). A scaling test system with several experiments was designed and operated at Coso geothermal resource with brine having a high scaling potential. Several methods were investigated at the brine temperature of 235 ºF. One method, circulation of abradable balls through the brine passages, was found to substantially reduce scale deposits. The test heat exchanger was operated with brine outlet temperatures as low as 125 ºF, which enables increased heat input available to power conversion systems. For advanced low temperature cycles, such as the Variable Phase Cycle (VPC) or Kalina Cycle, the lower brine temperature will result in a 20-30% increase in power production from low temperature resources. A preliminary design of an abradable ball system (ABS) was done for the heat exchanger of the 1 megawatt VPC system at Coso resource. The ABS will be installed and demonstrated in Phase 2 of this project, increasing the power production above that possible with the present 175 ºF brine outlet limit. A hermetic turbine generator (TGH) was designed and manufacturing drawings produced. This unit will use the working fluid (R134a) to lubricate the bearings and cool the generator. The 200 kW turbine directly drives the generator, eliminating a gearbox and lube oil system. Elimination of external seals eliminates the potential of leakage of the refrigerant or hydrocarbon working fluids, resulting in environmental improvement. A similar design has been demonstrated by Energent in an ORC waste heat recovery system. The existing VPC power plant at Coso was modified to enable the “piggyback” demonstration of the TGH. The existing heat exchanger, pumps, and condenser will be operated to provide the required

Recuperator with microjet technology as a proposal for heat recovery from low-temperature sources

Directory of Open Access Journals (Sweden)

Wajs Jan

2015-12-01

Full Text Available A tendency to increase the importance of so-called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative production of heat and electricity. For such systems the crucial points are connected with the heat exchangers, which should be small in size but be able to transfer high heat fluxes. In presented paper the prototype microjet heat exchanger dedicated for heat recovery systems is introduced. Its novel construction is described together with the systematical experimental analysis of heat transfer and flow characteristics. Reported results showed high values of the overall heat transfer coefficient and slight increase in the pressure drop. The results of microjet heat exchanger were compared with the results of commercially available compact plate heat exchanger.

Recuperator with microjet technology as a proposal for heat recovery from low-temperature sources

Science.gov (United States)

Wajs, Jan; Mikielewicz, Dariusz; Fornalik-Wajs, Elżbieta; Bajor, Michał

2015-12-01

A tendency to increase the importance of so-called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative production of heat and electricity. For such systems the crucial points are connected with the heat exchangers, which should be small in size but be able to transfer high heat fluxes. In presented paper the prototype microjet heat exchanger dedicated for heat recovery systems is introduced. Its novel construction is described together with the systematical experimental analysis of heat transfer and flow characteristics. Reported results showed high values of the overall heat transfer coefficient and slight increase in the pressure drop. The results of microjet heat exchanger were compared with the results of commercially available compact plate heat exchanger.

On board short-time high temperature heat treatment of ballast water: a field trial under operational conditions.

Science.gov (United States)

Quilez-Badia, Gemma; McCollin, Tracy; Josefsen, Kjell D; Vourdachas, Anthony; Gill, Margaret E; Mesbahi, Ehsan; Frid, Chris L J

2008-01-01

A ballast water short-time high temperature heat treatment technique was applied on board a car-carrier during a voyage from Egypt to Belgium. Ballast water from three tanks was subjected for a few seconds to temperatures ranging from 55 degrees C to 80 degrees C. The water was heated using the vessel's heat exchanger steam and a second heat exchanger was used to pre-heat and cool down the water. The treatment was effective at causing mortality of bacteria, phytoplankton and zooplankton. The International Maritime Organization (IMO) standard was not agreed before this study was carried out, but comparing our results gives a broad indication that the IMO standard would have been met in some of the tests for the zooplankton, in all the tests for the phytoplankton; and probably on most occasions for the bacteria. Passing the water through the pump increased the kill rate but increasing the temperature above 55 degrees C did not improve the heat treatment's efficacy.

Simulation and optimization study on a solar space heating system combined with a low temperature ASHP for single family rural residential houses in Beijing

DEFF Research Database (Denmark)

Deng, Jie; Tian, Zhiyong; Fan, Jianhua

2016-01-01

A pilot project of the solar water heating system combined with a low temperature air source heat pump (ASHP) unit was established in 2014 in a detached residential house in the rural region of Beijing, in order to investigate the system application prospect for single family houses via system...... optimization design and economic analysis. The established system was comprised of the glass heat-pipe based evacuated tube solar collectors with a gross area of 18.8 m2 and an ASHP with a stated heating power of 8 kW for the space heating of a single family rural house of 81.4 m2. The dynamic thermal...... with good building insulation were undertaken to figure out the system economical efficiency in the rural regions of Beijing. The results show that the payback periods of the solar space heating system combined with the ASHP with the collector areas 15.04-22.56 m2 are 17.3-22.4 years for the established...

Analysis of the temperature and pore water pressure field in the TED heating experiment

International Nuclear Information System (INIS)

Garitte, B.; Vaunat, J.; Gens, A.; Conil, N.; Armand, G

2012-01-01

, convection may be neglected because of the low permeability of the medium. Moreover, considering that the soil remains saturated throughout the experiment and that changes in porosity are minor (because of the high rigidity of the medium's skeleton), couplings from the hydro- and mechanical component to the thermal problem are likely to be very weak. On the basis of these assumptions, the thermal conduction problem can thus be resolved independently. In the first part of the paper, a methodology set up to determine the thermal conductivity of the medium on the basis of this assumption is described and applied to find the best fitting thermal conductivity value to reproduce the measured thermal field. In addition, the applied thermal load triggers a Hydro-Mechanical response of the rock as both, the rock skeleton and the water in the rock pores expand when heated. Thus, the hydro- and the mechanical response are tightly coupled. The second part of the paper is dedicated to the discussion of this response on the basis of theoretical considerations. 3D THM computations run with Code B right are used to analyse the rock response. We show the importance of reproducing correctly the presence of draining entities like the nearby GED gallery and some of the instrumentation boreholes before calibrating the parameters influencing the HM response. Water permeability and thermal expansion of both, rock skeleton and solid grain were identified as most influential parameters. Rock stiffness and its anisotropy are shown to have a secondary but non negligible influence. The temperature measurements are reproduced satisfactorily by the simulation. The overall good reproduction of the temperature field suggests that the effect of several heat sources is additive and was made possible. A clear correlation between temperature and pore water pressure evolution is observed from the first heating step. When temperature increases at sensor location, the pore water is compressed as a consequence of

Thermal Interface Evaluation of Heat Transfer from a Pumped Loop to Titanium-Water Thermosyphons

Science.gov (United States)

Jaworske, Donald A.; Sanzi, James L.; Gibson, Marc A.; Sechkar, Edward A.

2009-01-01

Titanium-water thermosyphons are being considered for use in the heat rejection system for lunar outpost fission surface power. Key to their use is heat transfer between a closed loop heat source and the heat pipe evaporators. This work describes laboratory testing of several interfaces that were evaluated for their thermal performance characteristics, in the temperature range of 350 to 400 K, utilizing a water closed loop heat source and multiple thermosyphon evaporator geometries. A gas gap calorimeter was used to measure heat flow at steady state. Thermocouples in the closed loop heat source and on the evaporator were used to measure thermal conductance. The interfaces were in two generic categories, those immersed in the water closed loop heat source and those clamped to the water closed loop heat source with differing thermal conductive agents. In general, immersed evaporators showed better overall performance than their clamped counterparts. Selected clamped evaporator geometries offered promise.