• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.477-482
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• 2011

In the present study, the performance characteristics of the heat pump chiller under heating conditions were experimentally investigated. Capacity, input power and COP under overload, frost and defrost conditions were obtained. The experimental data for the heat pump chiller were measured using the air-enthalpy calorimeter and the constant temperature water bath. At overload condition, the heating capacity and COP increase about 25.7% and 19.1%, respectively. The variations of the evaporator, the compressor outlet and the condenser temperature were obtained under frost and defrost conditions. The frost and defrost period of the heat exchanger decreases about 36.0~56.1%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1175-1182
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• 2004

Installations of vertical boreholes for the ground source heat pump system are expensive to install. One way to reduce the initial cost is to increase the specific heat extraction rate of borehole system. However, as the specific heat extraction rate increases the temperature of borehole fluid decreases with the resultant lower Coefficient Of Performance in Heating(COPH) of heat pump system. The purpose of this study is to provide the basic informations about the performance of heat pump system with the specific heat extraction rate and soil thermal properties such as thermal conductivity and temperature. It is shown that the specific heat extraction rate is the most important parameter for the ground source heat pump system. To obtain the reasonable COPH value (COPH > 3) the heat extraction rate should be about 25 W/m or less. Accurate measurements of soil thermal properties are also very important to design the system properly. The effects of borehole thermal resistances are also examined in this study.

• Journal of the Korean Solar Energy Society
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• v.33 no.6
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• pp.85-91
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• 2013

It is essential to reduce the amount of fossil fuel because facing with the natural problem such as a global warming. To achieve this goal, many of interests in the use of renewable energy is growing. Especially, as one of these renewable energy systems, a solar air heater invention has been conducted for enhancing the efficiency of solar air heater. According to this trend, scale-down sized experiment apparatus was constructed and performed for searching a proper fin and confirming the heat transfer performance by fin shape on constant heat condition to enhance efficiency of solar air heater. In this experiment, heat gain, convection heat transfer coefficient, number of transfer units, Nusselt number, Reynold's number, friction factor, performance factor were investigated in order to evaluate the thermal characteristics based on the real data obtained. By comparison with the each fin performance, a zigzag shape keeping a right angle to the plate had the highest value among them.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.338-344
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• 2008

The improvement of energy conservation is mandatory to decrease consumption of fossil fuels and to minimize negative impacts on the environment which originates from large cooling and heating demand. The absorption heat pump technology has a large potential for energy-saving in this respect. Absorption heat pump is a means to upgrade waste heat without the addition of extra thermal energy. The higher performance of absorber is of great importance for absorption heat pump cycle. In this study, in order to improve the performance of absorber, the absorber of tangential feed of a liquid phase with spiral tube has been investigated using methanol-glycerine as a working fluid. The spiral tube and tangential feeding generate the turbulence into the liquid flow while increasing the mass and heat transfer coefficients. The simultaneous heat and mass transfer were found to take place in a liquid turbulent film in the absorber with the spiral tube during the process of gas absorption. By calculating mass and heat transfer coefficients by measurement of the concentration and the temperature of each position in the absorber, the entrance was found to be more effective in enhancing mass and heat transfer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.5
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• pp.269-276
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• 2015

Single-effect $CH_3OH-LiI-ZnBr_2$ and $C_2H_5OH-LiI$ absorption heat pumps are simulated to evaluate feasibility as heating device. These systems are predicted to give higher heating COPs in wide operating ranges compared to conventional systems. Among the two systems, the $C_2H_5OH-LiI$ system is found to be more advantageous for operating in extremely cold weather due to the large solubility of Lil in $C_2H_5OH$.

• 월간 기계설비
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• s.119
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• pp.71-83
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• 2000

점차 복잡해지고 있는 사회적 욕구를 만족시키기 위한 건물에서는 반드시 복잡한 설비가 요구되고 있고, 이러한 설비시스템 중에는 급수, 급탕 및 배수설비라고 하는 배관시스템이 없다면 기능유지에 막대한 지장을 초래할 것은 자명하다고 하겠다. 이러한 배관시스템에서는 항시 또는 일부 사용되어질 물이나 사용된 물이 흐르기 때문에 배관내부에 발생하는 스케일(scale)이나 슬라임(slime) 등은 피할 수 없는 사실인 것이다. 건축물 내에 설치된 각종 배관은 건물의 기능을 유지하고 보건위생과 직결되는 중요한 기능을 담당하고 있어 세척의 필요성이 매우 높음에도 불구하고 배관의 수명이 다할 때까지 거의 세척이 이루어지지 않고 사용되어 왔다. 이들 배관에 대한 세척은 배관의 수명연장과 관마찰 계수를 낮추어 급수의 수송동력을 절감할 수 있고, 난방관의 열전달 효과를 높여 에너지 절약 효과를 거두어 건물의 유지관리 비용 절감에 기여할 수 있음에도 적절한 세척공법이 개발되지 않고 있다. 이러한 관점에 맞추어 건물배관의 특성에 맞도록 고압 세척장치를 개발하고 이를 이용한 세척공법을 적용하고자 하였다. 즉, 배관 내에 압축공기를 주기적으로 분사하여 맥동현상이 일어나도록 하면서 기포를 발생시켜 기포가 관의 내벽에서 성장하여 파괴될 때 관내에 부착된 이물질을 제거할 수 있고, 또한 세척효과를 높이기 위하여 관의 벽면에 접촉하면서 배출되는 과정에서 이물질을 제거할 수 있도록 구조와 아울러 이들 장치를 이용한 세척방법의 적용성에 대해서 고찰하고자 한다.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.2
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• pp.7-12
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• 2016

This study have an objective to suggest basic data and measured result of heating performance on water-water type horizontal geothermal heat pump which is based on heating and cooling load calculation result of small residential house. The average temperature during measured periods is $9.4^{\circ}C$ on primary EWT and is $7.6^{\circ}C$ on primary LWT. The temperature difference shows $1.8^{\circ}C$ as average temperature. Because the average outdoor temperature of peak is lager than on December and than on January, the temperature difference between EWT and LWT is bigger that on January than that on December. The system COP is 3.62.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.1
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• pp.1-6
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• 2015

This study presents analysis of the experimental data meeting conditions of several applications in real time. The results of this experimental study are as follows: Respectively in cooling and heating performance, a refrigerant charge tank can take automatic control of variation of the refrigerant quantity by controling pressure and temperature of system and outlet water temperature. The COP shows 3.5 in cooling operation and 3.2 in heating operation. The refrigerant quantity increases 0.69 kJ/h. When the outdoor temperature decreases $1^{\circ}C$, Therefore if the temperature become lower from $25^{\circ}C$ to $-16^{\circ}C$, the refrigerant quantity increases about 9.5%. Compared to the normal state experiment results, the COP in automatic control of the refrigerant quantity rises roughly 10%.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.170.1-170.1
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• 2010

Performance of water-to-air heat pump using raw water has been analyzed under part load heating operation in March, 2010. The water source heat pump of 30 RT was installed for 24 hours cooling and heating ventilation, and the gravity inflow water from Daechung dam is used as the heat source. The daily averaged water and air temperatures are $5.7^{\circ}C$ and $9.9^{\circ}C$ respectively, and the heat pump is operated under part load condition for 7.5 hours in 24 hours. The daily averaged heat pump COP calculated with heat transferred from the brine water is 2.49 and the monthly averaged COP is 2.25 in March. Based on the database of the California Energy Commission, the monthly averaged COPs of air source heat pumps installed in U.S.A. are 1.97 in March and 2.03 in April. Therefore it is confirmed again that the performance of the heat pump using raw water is better than that of air source heat pumps.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.2
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• pp.187-197
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• 1996

A computer program for thermal design analysis has been developed to predict the operating characteristics and performance of an absorption heat pump to recover $30{\sim}40^{\circ}C$ of waste hot water. The effects of heat transfer area of the system components, temperature and mass flow rate of heat transfer medium, and solution circulation rate on the system performance are investigated in detail. The results obtained indicate that the COP is increased with a decrease in the temperature of driving steam and with an increase in the temperature of waste hot water while the COP is little affected by the variation of a hot water temperature. It is also found that the heating output is increased with an increase in the temperature of waste hot water and driving steam as well as with a decrease in the temperature of hot water. The simulation results are also compared with the experimental results for a periodic operation of the system and obtained a satisfactory agreement.