• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.10-20
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• 2004

Experiments have been conducted in order to make comparisons of characteristics of a R410a cycle with a R22 cycle in terms of cooling capacity and coefficient of performance (COP). The parameters examined in the present work include air flow rate, indoor and outdoor air temperatures, and indoor relative humidity. These two refrigeration cycles constructed for this study share all components except compressor, accumulator, oil separator, and piping. The measurements were made using a psychrometric calorimeter. The experimental results show that the R410A cycle has several advantages for indoor units while the R22 cycle yields better performance for outdoor units.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.82-87
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• 2007

In the present study, the simulation on the annual performance evaluation of a renewable energy systems with fuel cell driven compound source hybrid heat pump systems is applied to the heating and cooling of large community building. The large community building has the economical advantage to apply heat pump cooling and heating systems the long period operation. If air and ground source hybrid heat pump systems are combined, COP of the system can be increased largely. Fuel cell driven compound source hybrid heat pump system can reduced the fuel cost as well as thermal storage tank sharply.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1999년도 동계 학술대회 논문집
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• pp.211-218
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• 1999

The ambient air is commonly used as low-temperature heat sources for heat pump operation. However, the coefficient of performance (COP) of the air -water heat pump is decreased with the ambient air temperature drop. In this study to solve this problem , the AVACTHE(Automatic Variable Area Capillary Type Heat Exchanger) with 3 levels of heat exchange area(0, 1495.4, 1794.5$\textrm{cm}^2$) was installed in the refrigerant circuit of the heat pump. The AVACTHE effect on the performance of heat pump was tested with the ambient air temperature variation. The high level COP of the heat pump could be achieved by the AVACTHE installation when below -5$^{\circ}C$ of the ambient air temperature.

• 설비공학논문집
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• 제9권4호
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• pp.462-471
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• 1997

The water-to-air heat pump system requires relatively lower energy consumption and less installation space. The heat exchangers used for this system are the finned-tube type for the indoor unit and the double-tube type for the outdoor unit. Mathematical models for this system are developed and programmed in computer. Experimental data from various conditions are obtained and compared with calculated values from the computer simulation program. Differences of cooling capacity and COP are 1.25% and 0.47%, and those of heating capacity and COP are 0.51% and 0.13%, respectively. Simulation results are in good agreement with test results. Therefore, the developed program is effectively used for the design and the performance prediction of water-to-air heat pump system.

• 설비공학논문집
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• 제15권3호
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• pp.166-176
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• 2003

Experiments have been conducted in order to make comparisons of a alternative refrigerant (R-410A) cycle characteristic with an existing refrigerant (R-22) cycle characteristic in terms of cooling capacity and coefficient of performance (COP). The parameters examined in the present work include air flow rate, indoor/outdoor air temperatures, and indoor relative humidity. These two refrigeration cycles share all components except compressor, accumulator, oil separator, and piping connecting them. The measurements were made using an air-enthalpy calorimeter. The experimental results show that the R-410A cycle has many advantages over indoor conditions while the R-22 cycle has better performance over outdoor conditions.

• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.252-262
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• 2007

In this paper, we suggest fuzzy control with feedforward compensator of superheat to progress both energy saving and coefficient of performance(COP) in a variable speed refrigeration system. The capacity and superheat are controlled simultaneously and independently by an inverter and an electronic expansion valve respectively for saving energy and improving COP in the system. By adopting the fuzzy control. the controller design for the capacity and superheat is possible without depending on a dynamic model of the system. Moreover, the feedforward compensator of the superheat can eliminate influence of the interfering loop between capacity and superheat. Some experiments are conducted to design the appropriate fuzzy controller by an iteration manner. The results show that the proposed fuzzy controller with the compensator can establish good control performances for the complicated refrigeration system with inherent strong non-linearity.

• 한국지열·수열에너지학회논문집
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• 제19권4호
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• pp.8-17
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• 2023

The air temperature is gradually increasing owing to global warming, especially in summer, therefore, the performance of an air source heat pump (ASHP) is expected to be decreased. Accordingly, the performance gap between the ASHP and ground source heat pump (GSHP) should be increased, however, the quantitative comparison has not been yet investigated. In this study, impact of global warming on the performance of the ASHP and GSHP is investigated based on the climate data for 1930, 1980, and 2030. The coefficient of performance (COP) as well as annual power consumption of the ASHP and GSHP are compared and analyzed. In the case of COP, the COP of GSHP hardly changes over the years owing to the constant ground temperature, while that of ASHP decreases by 3.7% for cooling and increases by 0.71% for heating. In the case of annual power consumption, the cooling and heating power consumption of GSHP increases by 12.69% and decreases by 15.58%, respectively, over the year owing to the changes in heating and cooling loads. As for the ASHP, the cooling and heating power consumption increases by 16.64% and decreases by 17.8%, respectively. For a more accurate comparison, power consumption ratio is introduced and shows that total annual power consumption of the GSHP to ASHP decreased from 68% in 1930 to 65% in 2030. Therefore, as global warming accelerates, the effect of reducing power consumption by using GSHP compared to ASHP is expected to be increasing.

• 설비공학논문집
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• 제11권3호
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• pp.422-430
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• 1999

This paper concerns the study of a two-stage absorption heat pump cycle to utilize treated sewage. This two-stage cycle consists of coupling double-effect with parallel or series flow type and single effect cycle so that the first stage absorber and condenser produces hot water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as absorber temperature on the coefficient of performance have been studied for two-stage absorption heat pump cycle. The working fluid is lithium bromide and water solution. The efficiency of the two-stage absorption heat pump cycle has been studied and simulation results show that higher coefficient of performance could be obtained for the first stage with parallel flow type. The optimum ratio of solution distribution can be shown by considering the COP, the crystallization of solution and the generator temperature.

• 동력기계공학회지
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• 제21권2호
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• pp.77-82
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• 2017

In the fishing boat, freshwater ice is loaded on the fishroom in advance and it is used for storage of fishes. However, it causes degradation of catches' freshness. Therefore, seawater ice machine on board is necessary for the fishing industry. In this study, seawater ice machine with drum type evaporator was manufactured, and the system was tested under various operating conditions having an influence on the COP and amount of ice produced. The main results are as follow : The COP of the system gets larger when the evaporation temperature and rotation speed of the drum in the evaporator increases. The most effective refrigerant is R22 and the value of the COP was 1.43 times higher than that of R404A. The amount of produced ice increases with respect to increment of the evaporation temperature, while that decreases with respect to increment of the evaporator drum rotation speed.

• 동력기계공학회지
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• 제21권3호
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• pp.45-50
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• 2017

This paper presents the Coefficient of performance(COP) and mass flow ratio of cascade refrigeration system with respect to refrigerants appling to high temperature cycle. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporating temperature, condensing temperature and internal heat exchanger effectiveness in high temperature cycle. The result of this study is as follows : The COP of cascade system increases with increasing degree of superheating and subcooling, compressor efficiency and internal heat exchanger effectiveness except increasing condensing temperature. The mass flow ratio of low and high temperature cycle increases with increasing evaporating temperature and condensing temperature, but decreases with increasing internal heat exchanger effectiveness, degree of superheating and subcooling. Also, the mass flow ratio has no correlation with compressor efficiency at high temperature cycle.