• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.647-650
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• 2002

A thermoacoustic refrigerator, using a resonant standing acoustic wave, has been built. It employs a loudspeaker to sustain a standing wave in a resonance tube. The stack of plates is 0.075mm-thick plastic sheet(Mylar), spirally wound to make a 40mm-diameter assembly 80mm long. and two heat exchanger are installed. The refrigerant is Helium gas. The description of thermoacoustic refrigerator are presented. The directly measured performance of the resonator. Tc/Th ( temperature ratio ) and $COP/COP_{c}$, (normalized by carnot's COP ) are plotted versus the thermal load Q applied to the cold end, for various speaker power.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.630-633
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• 2008

Geothermal heat pump systems use the earth as a heat source in heating mode and a heat sink in cooling mode. These systems can be used for heating or cooling systems in farm facilities such as greenhouses for protected horticulture, cattle sheds, mushroom house and etc. A horizontal type means that a geothermal heat exchanger is laid in the trench buried in 1.2 to 1.8 m depth. Because a horizontal type has advantages of low installation, operation and maintenance costs compared to a vertical type, it is easy to be adopted to agriculture. In this study, to heat and cool farm facilities and obtain basic data for practical application of horizontal geothermal heat pump system in agriculture, a horizontal geothermal heat pump system of 10 RT was installed in greenhouse. Heating and cooling performance of this system was estimated. The horizontal geothermal heat pump used in this study had heating COP of 4.57 at soil temperature of $14^{\circ}C$ with depth of 1.75m and heating COP of 3.75 at soil temperature of $7^{\circ}C$ with the same depth. The cooling COP was 2.7 at ground temperature at 1.75m depth of $25.5^{\circ}C$ and 2.0 at the temperature of $33.5^{\circ}C$.

• 대한기계학회논문집
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• 제19권8호
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• pp.2012-2021
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• 1995

An experimental study was performed for the analysis of dynamic characteristics of refrigeration system by controlling the evaporator superheat. Experimental data have been taken utilizing two different devices, thermostatic expansion valve(T.E.V.) and electronic expansion valve(E.E.V.), for the control of the evaporator superheat. The ranges of parameters, such as superheat, mass flow rate of refrigerant and inlet temperature of evaporator were 5-30.deg. C 90-170 kg/h and 10-25.deg. C, respectively. The data taken from the T.E.v.and E.E.v.were discussed with the control of the superheat, pressure drop, refrigerating capacity, compression work, evaporating temperature, condensing temperature and COP affecting performance characteristics of refrigeration system. In case of the refrigerant flow control with T.E..V., the superheat and pressure drop of the evaporator varied periodically, but the control with E.E.V., the parameters were very stable. In E.E.v.control, refrigerating capacity, compression work and evaporating temperature were decreased with increasing superheat, and the highest COP was obtained in the range of superheat from 5.deg. C to 15.deg. C.

• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.35-41
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• 2015

This study was conducted to develop a heat pump system to utilize waste heat within the greenhouse during the daytime in winter season. The system runs at 8 am to 6 pm for the heat storage operation, and from 6 pm to 8 am of the next day for the heat radiant work. In the case of the heat storage operation, the average solar radiation was $168.3W/m^2$ with $16.3^{\circ}C$ outside temperature. The $COP_s$ of the system shows 4.59 in this operation mode. When the temperature goes up to $18.6^{\circ}C$, the system $COP_s$ reached at 5.10. On the other hand, the $COP_h$ of the system in heat radiation mode shows 2.63. In this case, the inside of the greenhouse temperature was reaches at $24.7^{\circ}C$ when the outside temperature was $12.9^{\circ}C$.

• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.1-10
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• 2013

Simulation study of a solar hybrid heat pump using R744 and R22 for residential applications was carried out according to heat pump operating temperature, outdoor temperature and solar radiation. As a result, when the heat pump operating temperature increases from $40^{\circ}C$ to $48^{\circ}C$, the COP of a R744 and R22 heat pump system decrease from 2.15 to 1.7 and from 3.09 to 2.69, respectively. Besides, as the outdoor temperature rises from $3^{\circ}C$ to $11^{\circ}C$, the COP of R744 and R22 heat pump system increase from 1.73 to 2.12 and from 2.73 to 3.02. When the solar radiation increases from 10 to 20 $MJ/m^2$, the collector operating time and collector efficiency of R744 heat pump increase 10.3 times and 50.7%, respectively. The performance of R744 solar hybird heat pump is more sensitive to operation condition compared to that of R22. Besides, the solar heating system is more effective to the R744 heat pump system.

• 설비공학논문집
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• 제9권1호
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• pp.82-91
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• 1997

R-410a and R-407c witch have the best potential among the substances being considered as R-22 alternatives were tested as "drop in" refrigerants against a set R-22 baseline tests for comparison. The performance evaluations were carried out in a psychrometric calorimeter test facility using the residential split-type air conditioner under the ARI rating conditions. Other than the use of different lubricant and a hand-operated expansion valve, one of the commercial systems was selected for the experiment. Performance characteristics were measured; compressor power, capacity, VCR, mass flow rate and COP. The tests showed that R-407c can be directly applied to the existing refrigeration system because of its similar vapor pressure and other thermopysical properties with those of R-22. However, it required change to the volume flow rate of compressor in order to achieve the similar performance with R-22 because of its relatively small VCR and capacity. Meanwhile, R-410a has too high a vapor pressure to be applied to the existing system and this feature results in relatively low COP of the system compared to that of R-22. But this could be improved by changing compressor design considering R-410a's relatively high VCR and capacity compared to those of R-22.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1267-1271
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• 2009

In the present study, performance characteristics on environment change of A/C applied fin-tube and PF heat exchangers were experimentally investigated. Capacity and COP changing an outlet air velocity, an indoor/outdoor temperature and a relative humidity were obtained. Air－enthalpy calorimeter was used. As the air velocity, indoor temperature and relative humidity increase, capacity and COP increase. PF A/C has smaller refrigerant weight than the fin-tube A/C. The performance of PF-2 A/C with the squarer fin was more excellent than that of PF-1 A/C with the triangler fin.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.521-529
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• 2012

Since the energy demand for refrigeration and air-conditioning has greatly increased all over the world, thermally activated refrigeration cycle has attracted much attention. This study carries out a performance analysis of a vapor compression cycle (VCC) driven by organic Rankine cycle (ORC) utilizing low-temperature heat source in the form of sensible heat. The ORC is assumed to produce minimum net work which is required to drive the VCC without generating an excess electricity. Effects of important system parameters such as turbine inlet pressure, condensing temperature, and evaporating temperature on the system variables such as mass flow ratio, net work production, and coefficient of performance (COP) are thoroughly investigated. The effect of choice of working fluid on COP is also considered. Results show that net work production and COP increase with increasing turbine inlet pressure or decreasing condensing temperature. Out of the five kinds of organic fluids considered $C_4H_{10}$ gives a relatively high COP in the range of low turbine inlet pressure.

• 대한화학회지
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• 제61권4호
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• pp.143-150
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• 2017

절연유에 높은 농도로 함유되어 있는 폴리염화바이페닐(PCB)을 처리하기 위해서 역류산화공정이 개발되었고 그 평가가 이루어졌다. 학산금속공업(주)로부터 구한 절연유 중의 PCBs의 함량은 1,512 ppm이었다. 역류산화공정은 산소의 흐름 속도와 반대되는 방향으로 자기 스스로 이동하는 자발적인 불꽃을 이용한다. 불꽃은 활성탄에 흡착되어 있는 PCBs를 제거함과 동시에 활성탄을 재생시킨다. 불꽃의 온도는 활성탄의 질량 손실과 역류산화공정 동안 배출되는 CO와 $CO_2$의 상대적인 비에 의해 결정하였고, 온도는 $650{\sim}850^{\circ}C$의 범위를 보였다. PCBs의 제거 효율은 무게비로 활성탄에 5%가 적재된 절연유를 1번의 역류산화공정을 거쳤을 때 99.99%이상을 나타내었다. 또한 60%의 절연유를 활성탄에 적재하여 3번의 연속적인 역류산화공정을 거쳤을 때 같은 제거 효율을 얻었다. 덧붙여서, 역류산화공정 동안 활성탄의 비표면적은 신탄의 수치와 비슷한 수준으로 회복되었다. 역류산화반응은 쉽고 경제적으로 절연유에 있는 고농도의 PCBs를 제거하는데 대단히 효과적이다는 것을 증명하였다.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.77-84
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• 2011

Korea and some other countries located in the northern hemisphere employ the air conditioner for the space cooling in the hot summer season and also some kinds of heaters for the space heating in the cold winter season. Especially in Korea, a great number of air conditioners of about 12,700,000 sets have been used these days. However, they are used for a short operation period of only 58 days a year, which results in the material and economic losses. To solve this problem and employ this system for the emergency shelter, a new conversion unit which could convert the existing air conditioner to a heat pump system for simultaneous heating and cooling was developed in this study, and the thermal performance was tested. The results indicated that the indoor air could be heated from $27^{\circ}C$ to $39^{\circ}C$ by the air conditioner converted to a heat pump system with the ambient temperature variation of $-10^{\circ}C{\sim}10^{\circ}C$, and cooled from $20^{\circ}C$ to $15^{\circ}C$ by the converted system with the ambient temperature variation of $20^{\circ}C{\sim}35^{\circ}C$. And also the heating COP increased from 3.3 to 5.3 in case of the heat exchange of the super cooling(HESC) circuit and from 3.0 to 4.0 in case of the By-pass with the ambient temperature variation of $-10^{\circ}C{\sim}10^{\circ}C$, respectively, whereas the cooling COP decreased from 3.1 to 2.1with the increase of the ambient temperature from $20^{\circ}C$ to $35^{\circ}C$.