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Heat Pump (heat + pump)

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Selected Abstracts

Evaluating MT3DMS for Heat Transport Simulation of Closed Geothermal Systems

GROUND WATER, Issue 5 2010
Jozsef Hecht-Méndez
Owing to the mathematical similarities between heat and mass transport, the multi-species transport model MT3DMS should be able to simulate heat transport if the effects of buoyancy and changes in viscosity are small. Although in several studies solute models have been successfully applied to simulate heat transport, these studies failed to provide any rigorous test of this approach. In the current study, we carefully evaluate simulations of a single borehole ground source heat pump (GSHP) system in three scenarios: a pure conduction situation, an intermediate case, and a convection-dominated case. Two evaluation approaches are employed: first, MT3DMS heat transport results are compared with analytical solutions. Second, simulations by MT3DMS, which is finite difference, are compared with those by the finite element code FEFLOW and the finite difference code SEAWAT. Both FEFLOW and SEAWAT are designed to simulate heat flow. For each comparison, the computed results are examined based on residual errors. MT3DMS and the analytical solutions compare satisfactorily. MT3DMS and SEAWAT results show very good agreement for all cases. MT3DMS and FEFLOW two-dimensional (2D) and three-dimensional (3D) results show good to very good agreement, except that in 3D there is somewhat deteriorated agreement close to the heat source where the difference in numerical methods is thought to influence the solution. The results suggest that MT3DMS can be successfully applied to simulate GSHP systems, and likely other systems with similar temperature ranges and gradients in saturated porous media. [source]

Exergetic performance assessment of a pilot-scale heat pump belt conveyor dryer

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010
Zafer Erbay
Abstract In this study, olive leaves were dried in a pilot-scale heat pump (HP) belt conveyor dryer as a thin layer. Drying experiments were carried out at the drying air temperature range of 45,55°C with the drying air velocity range of 0.5,1.5,m,s,1. The performance of the system and the process was evaluated using exergy analysis method. The exergy loss and flow diagram (the so-called Grassmann diagram) of the dryer system was presented to give quantitative information regarding the proportion of the exergy input that is dissipated in the various system components. Effects of the drying air temperature and the velocity on the performance of the drying process were discussed. The actual coefficient of performance values were obtained to be 2.37 for the HP unit and 2.31 for the overall system, respectively. The most important component of the system for improving the efficiency was determined to be the compressor. Exergetic efficiencies of the drying of olive leaves were in the range of 67.45,81.95%. It was obtained that they increased as the drying air temperature decreased and the drying air velocity increased. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Modeling an industrial energy system: Perspectives on regional heat cooperation

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2008
S. Klugman
Abstract Through energy efficiency measures, it is possible to reduce heat surplus in the pulp and paper industry. Yet pulp and paper mills situated in countries with a heat demand for residential and commercial buildings for the major part of the year are potential heat suppliers. However, striving to utilize the heat within the mills for efficient energy use could conflict with the delivery of excess heat to a district heating system. As part of a project to optimize a regional energy system, a sulfate pulp mill situated in central Sweden is analyzed, focusing on providing heat and electricity to the mill and its surrounding energy systems. An energy system optimization method based on mixed integer linear programming is used for studying energy system measures on an aggregated level. An extended system, where the mill is integrated in a regional heat market (HM), is evaluated in parallel with the present system. The use of either hot sewage or a heat pump for heat deliveries is analyzed along with process integration measures. The benefits of adding a condensing unit to the back-pressure steam turbine are also investigated. The results show that the use of hot sewage or a heat pump for heat deliveries is beneficial only in combination with extended heat deliveries to an HM. Process integration measures are beneficial and even increase the benefit of selling more heat for district heating. Adding a condensing turbine unit is most beneficial in combination with extended heat deliveries and process integration. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Dynamic operation plan of a combined fuel cell cogeneration, solar module, and geo-thermal heat pump system using Genetic Algorithm

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2007
Shin'ya Obara
Abstract A chromosome model that simulates the operation patterns of an energy system was introduced into a simple Genetic Algorithm, and a method of dynamic optimization was developed. This paper analyses the operation planning of an energy system that uses in combination a solar power module, proton-exchange membrane fuel cell cogeneration (PEMFC-CGS) with methanol steam reforming, a geo-thermal heat pump, heat storage and battery, commercial power, and a kerosene boiler. The hours of operation of each energy device and the rate of the energy output were calculated by having introduced the analysis program developed by this study. Three objective functions: (a) minimization of operation cost; (b) minimization of the error of demand-and-supply balance; and (c) minimization of the amount of greenhouse gas discharge were given to the optimization analysis of the system. Furthermore, the characteristics of the system operation planning under each objective function are described. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Exergetic performance assessment of a ground-source heat pump drying system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2007
Ebru Hancioglu Kuzgunkaya
Abstract In evaluating the efficiency of heat pump (HP) systems, the most commonly used measure is the energy (or first law) efficiency, which is modified to a coefficient of performance (COP) for HP systems. However, for indicating the possibilities for thermodynamic improvement, energy analysis is inadequate and exergy analysis is needed. This study presents an exergetic assessment of a ground-source (or geothermal) HP (GSHP) drying system. This system was designed, constructed and tested in the Solar Energy Institute of Ege University, Izmir, Turkey. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. COP values for the GSHP unit and overall GSHP drying system are found to range between 1.63,2.88 and 1.45,2.65, respectively, while corresponding exergy efficiency values on a product/fuel basis are found to be 21.1 and 15.5% at a dead state temperature of 27°C, respectively. Specific moisture extraction rate (SMER) on the system basis is obtained to be 0.122 kg kW,1 h,1. For drying systems, the so-called specific moisture exergetic rate (SMExR), which is defined as the ratio of the moisture removed in kg to the exergy input in kW h, is also proposed by the authors. The SMExR of the whole GSHP drying system is found to be 5.11 kg kW,1 h,1. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Experimental investigation of an adsorptive thermal energy storage

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2007
B. Dawoud
Abstract A zeolite-water adsorption module, which has been originally constructed for an adsorption heat pump, has been experimentally investigated as an adsorptive thermal energy storage unit. The adsorber/desorber heat exchanger contains 13.2 kg of zeolite 13X and is connected to an evaporator/condenser heat exchanger via a butterfly valve. The flow rate of the heat transfer fluid in the adsorber/desorber unit has been changed between 0.5 and 2.0 l min,1, the inlet temperature to the evaporator between 10 and 40°C. It turned out that the higher the flow rate inside the adsorber/desorber unit the faster and more effective is the discharge of heat. However, at lower flow rates higher discharge temperatures are obtained. Storage capacities of 2.7 and 3.1 kWh have been measured at the evaporator inlet temperatures of 10 and 40°C, respectively, corresponding to thermal energy storage densities of 80 and 92 kWh m,3 based on the volume of the adsorber unit. The measured maximum power density increases from 144 to 165 kWh m,3 as the flow rate in the adsorber increases from 0.5 to 2 l min,1. An internal insulation in form of a radiation shield around the adsorber heat exchanger is recommended to reduce the thermal losses of the adsorptive storage. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Operating schedule of a combined energy network system with fuel cell

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2006
S. ObaraArticle first published online: 16 MAY 200
Abstract The chromosome model showing system operation pattern is applied to GA (genetic algorithm), and the method of optimization operation planning of energy system is developed. The optimization method of this operation planning was applied to the compound system of methanol-steam-reforming-type fuel cell, geothermal heat pump and the electrolysis tank of water. The operation planning was performed for the energy system using the energy demand pattern of the individual residence of Sapporo city. From analysis results, the amount of outputs of a solar module and the relation of the operation cost of the system, which are changed by the weather were clarified. The representation day in February of the ratio of the operation cost in case of (0% of output rates) the rainy weather to the time of fine weather (100% of output rates) is 1.12. And the representation day in July is 1.71. Furthermore, the optimal capacity of accumulation of electricity and thermal storage was estimated, and they are 308 and 23 MJ, respectively. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Re-circulating heat pump assisted continuous bed drying and energy analysis

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2005
Phani K. Adapa
Abstract Specialty crops such as ginseng, herbs and echinacea need to be dried at low temperatures (30,35°C) for product quality optimization. A drying system that is both energy efficient and preserves product quality is desired. A re-circulating heat pump continuous bed dryer system was designed, constructed and field-tested for this purpose. The heat pump dryer system was experimentally evaluated using several potential herbal and medicinal crops such as alfalfa, catnip, wormwood, red clover, portulaca, dandelion and ginseng. These crops were dried either in chopped, sliced or whole form, depending on the part of the plant (aerial or root). The specific moisture extraction rates (SMER) obtained for various crops were in the range of 0.06,0.61 kg kWh,1. It took 5 days and 190 kWh of energy to reduce the average moisture content of ginseng roots below 10% (wb), while commercial dryers currently in use would take on an average 14 days and 244 kWh of energy at comparable loading rates. The re-circulating nature of the heat pump dryer made it 22% more energy efficient and resulted in 65% reduced drying time compared to conventional dryers incorporating electric coil heaters. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Experimental investigation of the performance of a solar-assisted ground-source heat pump system for greenhouse heating

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2005
Onder Ozgener
Abstract The main objective of the present study is to investigate the performance characteristics of a solar-assisted ground-source heat pump system (SAGSHPS) for greenhouse heating with a 50 m vertical 1¼ in nominal diameter U-bend ground heat exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22°C, 1226 degree days heating, base: 18°C), Turkey. Based upon the measurements made in the heating mode, the heat extraction rate from the soil is found to be, on average, 54.08 Wm,1 of bore depth, while the required borehole length in meter per kW of heating capacity is obtained as 12.57. The entering water temperature to the unit ranges from 8.2 to 16.2°C, with an average value of 9.1°C. The greenhouse air is at a maximum day temperature of 25°C and night temperature of 14°C with a relative humidity of 40%. The heating coefficient of performance of the heat pump (COPHP) is about 2.13 at the end of a cloudy day, while it is about 2.84 at the end of sunny day and fluctuates between these values in other times. The COP values for the whole system are also obtained to be 5,15% lower than COPHP. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Energy conservation conflicts in district heating systems

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2003
Björn Rolfsman
Abstract In Sweden, district heating of buildings is in common use. This paper deals with the district heating tariff. Many economists argue that the tariff should be based on short-range marginal costs, but in practice this never occurs. Traditionally instead, the prices are set so they are lower than the alternatives. A case study is presented dealing with a residential building in Navestad, Norrköping. For this building, the life-cycle cost with extra wall insulation and the introduction of a heat pump has been calculated. A comparison of two perspectives, the present tariff and a tariff-based short-range marginal cost, is done. It is shown that there is a conflict between the two perspectives. For the tariff based on short-range marginal cost, neither extra insulation nor an introduction of a heat pump is profitable. However, with the present tariff, a bivalent system with a heat pump and district heating is profitable. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Modelling of an ethanol-water distillation column assisted by an external heat pump

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2002
S. B. M. Oliveira
Abstract This paper presents a simulation of an ethanol,water distillation column assisted by a vapour-compression heat pump. The heat pump is of the external type, i.e., it uses a working fluid (refrigerant) different from that of the column. A simulation model was developed and four different working fluids were studied: R-11 and R-114 and, as substitutes, the column own fluids, water and ethanol. Results from the simulation model have shown that considerable reduction in energy consumption can be achieved with the installation of a heat pump. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Analysis of heat transfer characteristics of an unsaturated soil bed: a simplified numerical method

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2001
Gopal B. Reddy
Abstract This paper is a continuation of a study reported in this Journal in February 1999. The paper presents a summary of the two-dimensional macroscopic continuity, momentum and energy equations in a cylindrical co-ordinate system that describe heat and mass transfer through unsaturated soil. The hydrodynamic laws governing flow of water through unsaturated soil are also presented. The explicit numerical procedure and the method to solve the equations are described. Characteristics of the corresponding computer program are also discussed. The results obtained with the current cylindrical governing equations are compared with the previously reported results based upon the Cartesian system of equations. It is observed that the results obtained with cylindrical formulations are in closer agreement with the experimental results. The effects of various heat transfer processes as well as the motion of fluids on heat transfer in a clay bed coupled to a heat pump are discussed. Heat diffusion into the soil by conduction is shown to be predominant through the early stage of heating, while the liquid water motion contributes to heat transfer during the intermediate times and the gas motion is shown to become significant during the last stages of drying. The contribution of the convective transport increases with the temperature and becomes equal to the contribution by conduction at moderately high temperatures. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Thermal performance of a packed bed reactor for a high-temperature chemical heat pump

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2001
Yukitaka Kato
Abstract The thermal performance of a chemical heat pump that uses the reaction system of calcium oxide/lead oxide/carbon dioxide, which is developed for utilization of high-temperature heat above 800°C, is studied experimentally. The thermal performance of a packed-bed reactor of a calcium oxide/carbon dioxide reaction system, which stores and transforms a high-temperature heat source in the heat pump operation, is examined under various heat pump operation conditions. The energy analysis based on the experiment shows that it is possible to utilize high-temperature heat with this heat pump. This heat pump can store heat above 850°C and then transform it into a heat above 900°C under an approximate atmospheric pressure. An applied system that combines the heat pump and a high-temperature process is proposed for high-efficiency heat utilization. The scale of the heat pump in the combined system is estimated from the experimental results. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Neural networks,a new approach to model vapour-compression heat pumps

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2001
H. Bechtler
Abstract The aim of this paper is to model the steady-state performance of a vapour-compression liquid heat pump with the use of neural networks. The model uses a generalized radial basis function (GRBF) neural network. Its input vector consists only of parameters that are easily measurable, i.e. the chilled water outlet temperature from the evaporator, the cooling water inlet temperature to the condenser and the evaporator capacity. The model then predicts relevant performance parameters of the heat pump, especially the coefficient of performance (COP). Models are developed for three different refrigerants, namely LPG, R22 and R290. It is found that not every model achieves the same accuracy. Predicted COP values, when LPG or R22 are used as refrigerant, are usually accurate to within 2 per cent, whereas many predictions for R290 deviate more than ±10 per cent. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Application of a chemical heat pump to a cogeneration system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2001
Yukitaka Kato
Abstract The feasibility of a proposed system that combines a magnesium oxide/water chemical heat pump and a diesel engine as a cogeneration system is discussed based on experimental results. The combined system is intended to utilize the waste heat discharge from the engine by means of the chemical heat pump and to level the heat supply load of the engine, allowing enhanced energy utilization. The thermal performance of the chemical heat pump in the cogeneration system is estimated based on the results of a packed-bed experiment. The estimation indicates that by storing the waste heat from the engine during low demand periods, the cogeneration system can produce more than several times the standard thermal output of the diesel engine during peak demand periods. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Energy Conservation in Urban Areas

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2008
Hideharu Sugihara Member
Abstract This article outlines the energy conservation measures in the civilian sector from a few different viewpoint regarding energy conservation in cities. First, the energy consumption trends in the business and residential sectors are discussed, focusing the importance of energy conservation measures in applications such as home heating, water heating and specific power demand. Second, as a measure to reduce energy demand itself, energy conservation by way of applying heat insulating materials to buildings and changing the life style of residents is considered. And from the viewpoint of improving the energy system efficiency, additionally discussed here are the measures to improve the efficiency of each energy equipment such as air-conditioners and co-generation equipment, and the characteristics of District heating and cooling systems such as the local energy infrastructures. Lastly, from the knowledge obtained through model analyses by the authors, a scheme is recommended that would be one of the most efficient city-energy schemes where the energy systems including heat pumps, co-generators or equipment using solar power are utilized for their best-suited applications for business and residential customers. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Coupling of thermoelectric modules with a photovoltaic panel for air pre-heating and pre-cooling application; an annual simulation

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2008
Nolwenn Le Pierrès
Abstract Thermoelectric (TE) modules are possible reversible pre-cooling and pre-heating devices for ventilation air in buildings. In this study, the opportunity of direct coupling of TE modules with photovoltaic (PV) cells is considered. This coupling is evaluated through a numerical simulation depending on the meteorological conditions of Chambéry, Alpine region in France, and on the cooling or heating use of the TE modules, through annual energy and exergy efficiencies. For the considered conditions, TE module performances are of the same order as the ones of the vapour compression heat pumps, with a TE coefficient of performance higher than 2 for low values of input DC current. The PV,TE coupling efficiency varies between 0.096 and 0.23 over the year, with an average value of 0.157. Evolutions of the exergy effectiveness of PV and TE elements follow the same trends as the corresponding energy efficiencies but with steeper variations for the coupling exergy yield that varies between 0.004 and 0.014, with an annual average value of 0.010. The direct PV,TE coupling does not seem to be a sustainable option for the summer cooling purpose particularly. A case study with indirect coupling under a warm climate is considered and shows that the use of TE devices could be efficient in housing to ensure summer thermal comfort, but the corresponding necessary PV area would induce a high investment. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Geothermal energy utilization in Turkey

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2001
G. G. Gunerhan
Abstract This paper investigates the status of geothermal development in Turkey as of the end of 1999. Turkey is one of the countries with significant potential in geothermal energy. Resource assessments have been made many times by the Mineral Research and Exploration Directorate (MTA) of Turkey. The main uses of geothermal energy are mostly moderate- and low-temperature applications such as space heating and domestic hot water supply, greenhouse heating, swimming and balneology, industrial processes, heat pumps and electricity generation. The data accumulated since 1962 show that the estimated geothermal power and direct use potential are about 4500 MWe and 31 500 MWt, respectively. The direct use capacity in thermal applications is in total 640 MWt representing only 2 per cent of its total potential. Since 1990, space heating and greenhouse developments have exhibited a significant progress. The total area of greenhouses heated by geothermal energy reached up to about 31 ha with a heating capacity of 69.61 MWt. A geothermal power plant with a capacity of 20.4 MWe and a CO2 factory with a capacity of 40000 ton yr,1 have been operated in the Denizli-Kizildere field since 1984 and 1986, respectively. Ground source heat pumps have been used in residential buildings for heating and cooling for approximately 2 years. Present applications have shown that geothermal energy in Turkey is clean and much cheaper compared to the other energy sources like fossil fuels and therefore is a promising alternative. As the projects are recognized by the public, the progress will continue. Copyright © 2001 John Wiley & Sons, Ltd. [source]