• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.505-510
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• 2007

Greenhouses should be heated during nights and co Id days in order to fit growth conditions in greenhouses. Ground source heat pump(GSHP) or geothermal heat pump system(GHPs) is recognized to be outstanding heating and cooling system. Horizontal GSHP system is typically less expensive than vertical GSHP system but requires wide ground area to bury ground heat exchanger (GHE). In this study, a horizontal GSHP system with thermal storage tank was installed in greenhouse and investigated as performance characteristics. In the daytime, heating load of greenhouse is very small or needless because solar radiation increases inner air temperature. The results of study showed that the heating coefficient of performance of the heat pump($COP_h$) was 2.9 and the overall heating coefficient of performance of the system($COP_{sys}$) was 2.4. Heating energy cost was saved 76% using the horizontal GSHP system with thermal storage tank.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.431-439
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• 2001

Recently, multi-room type heat pump system has aroused much attention, because it can achieve much reduction of installation cost and space as well as energy saving in companion with the single room type heat pump system. In the present study, performance characteristics of a 3 room type inverter driven heat pump system, which is widely spread in Japanese market, are measured.. In the single room operation, performances of a heat pump system such s the difference of compressor outlet and inlet pressures and the mass flowrate may increase with the increase of cooling capacity so that COP of the system decrease with the increase of cooling capacity. However, in the 2 room operation, mass flowrate and COP of the total system increase markedly as compared with the single room operation.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2310-2315
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• 2008

In this paper, study on performance analysis of bubble pump on the domestic solar water heater system is presented. Device of this experiment is consisted of bubble pump, solar collector and heat exchanger. At the mean time, this system have attached temperature sensors and pressure sensors at bubble pump. In addition, the flow meter was installed at outlet of heat exchanger. And then result of experimental study, average value of the heat exchange amount in heat exchanger was about 7.9kcal/hr, the maximum value of the heat amount in water tank($0.4m^3$) was 489.7kcal/hr and the maximum value of the mass flow rate in bubble pump was about $0.5{\ell}/min$.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.9 no.2
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• pp.1-7
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• 2013

Most researches done on heat pumps have been on heat pumps for refrigeration, cooling and heating. There is therefore the need for more research on hot water heat pumps, especially for high temperature. Even though the cascade heat pump cycle has a great potential more efficient hot water generation even at low evaporating temperatures, it has been researched least for this purpose. In this study, the heating performance of a variable speed cascade heat pump was investigated by varying operating conditions. For the same heating capacity values, it was found that increasing the low stage compressor speed was more suitable for enhancing the performance of the system to get a higher temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.303-314
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• 1998

In this study, the performance of a multi-stage condensation heat pump was examined. Computer simulation programs were developed for 1-stage, 2-stage, and 3-stage heat pumps and R11, R123, R141b were tested as working fluids. The results showed that coefficients of performance(COPs) of an optimized 3-stage condensation heat pump are 25∼40% higher than those of a conventional 1-stage heat pump. The increase in COP, however, differed among the fluids tested. The improvement in COP largely stems from the decrease in average LMTD values in the condensers of the multi-stage system. For the 3-stage condensation heat pumps, optimized UA values of three condensers were determined to be 30∼40% of the UA value of the total condenser regardless of the working fluid. When the amount of cooling water entering into the intermediate and high-stage subcoolers is roughly 10% of the total condenser cooling water respectively, the optimum performance was achieved for the 3-stage condensation heat pump.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.364-369
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• 2007

A system heat pump provides the benefits of comfort, energy conservation and easy maintenance. Recently, the system heat pump has been employed in small and medium-sized buildings. However, the performance data and control algorithm for system heat pump are limited in literature due to complicated system parameters and operating conditions. In the present study, the performance of a system heat pump with two indoor unit is measured by varying indoor loads, EEV opening, and compressor speed. In addition, the integral optimum regulator which includes MIMO control algorithm is proposed. The capacity modulation and optimum capacity for each indoor unit can be adjusted by utilizing the EEVs opening and compressor speed. The proposed scheme shows appropriate control performance at test conditions.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.80-92
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• 1998

A third-order simulation model of a Vuilleumier{VM) heat pump has been developed. This model takes into account the major losses such as the heat conduction losses through regenerators and displacers, the pumping losses and the wall-to-gas heat transfer losses in active volumes, in addition to the heat exchanger and regenerator losses. The working volume was divided into 12 control volumes and the conservation equations of mass and energy were applied to each control volume. Pressure drops were considered in regenerators only. Thermodynamic behavior of the working gas in a VM heat pump was investigated and effects of the major losses and operating conditions on the performance of a VM heat pump were shown.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.2
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• pp.155-164
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• 1998

A multi-type heat pump controls the mass flow rate of the working fluid to cope with variable heat loads when it is under dynamic load condition. This paper describes the exergy analysis associated with the dynamic response of heat pump. First, a basic heat pump cycle is examined at steady state to show the general trends of exergy changes in each process of the cycle. Entropy generation issue in the exchangers is discussed to optimize the heat pump cycle. Second, the performance of the inverter-driven heat pump is compared to that of the conventional one when the heat load is variable. Third, the exergy destruction rate associated with the ON/OFF operations of the heat pump is calculated by simulating the thermodynamic states of the condenser and the evaporator. The inefficiency of the ON/OFF operation during the transient period is quantitatively revealed by the exergy analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.59-66
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• 2003

The purpose of this study is to analyze the characteristics (COP) of the heat pump system for various operating conditions with the use of seawater heat source and exhaust energy. To accomplish the goal, first of all, the computer simulation for heat pump system is carried out. The heat pump system model is made of a waste heat recovery system and a vapor compression refrigeration system, and the working fluid is R-22. The model calculated the change of COP with the variation of temperature and flow rate. The COP and the plate heat exchanger (PHE) area of the heat pump system are considered moderately high in the condensation temperature of $25^{\circ}^C$ and the evaporation temperature of $2^{\circ}^C$ in indoor culture system. The simulation results will be used effectively for the design and the performance prediction of heat pump system using unused energy in a land base aquaculture system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.1
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• pp.71-81
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• 2005

The main objective of the present study is to investigate the performance characteristics of a ground-source heat pump(GSHP) system with a 130 m vertical and 62 mm nominal diameter U-tube ground heat exchanger. In order to evaluate the performance analysis, the ground-source heat pump connected to a test room with $90\;m^2$ floor area in the Korea Institute of Construction $Technology(37^{\circ}39'N,\;126^{\circ}48'E)$ was designed and constructed. This ground-source heat pump system mainly consisted of ground heat exchanger, indoor heat pumps and measuring devices. The cooling and heating loads of the test room were 5.5 and 7.2 kW at design conditions, respectively. The experimental results were obtained from July 2, 2003 to July 1, 2004. The cooling and heating performance coefficients of the system were determined from the measured data. The average cooling and heating COPs for the system were obtained to be 4.90 and 3.96, respectively. The temperature variations in ground and the ground heat exchanger pipe surface at different depths were also measured.