• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.618-622
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• 2007

In the present study, the cooling and heating operation characteristics of a multi-heat pump have been experimentally investigated for the number of the indoor units(A, B, C) and the operating conditions. The heat pump was controlled by an inverter scroll compressor. The performance of the heat pump was measured by the multi-calorimeter of an air enthalpy method. Cooling and heating capacities and COPs were obtained at the cooling and heating temperature conditions and the setting temperatures of an indoor unit. With increasing the operation frequency of the compressor, the cooling and heating capacities of the heat pump increased linearly. The operation frequency region of the compressor was different as the combination of the indoor unit and the cooling/ heating condition.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.99-102
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• 2008

The growth of domestic energy demand is rapidly increased for the industrialization and the improvement of the living standards. It is also recognised that the importance of the use of environmentally friendly energy and high efficient equipment. Ground Source heat pumps(GSHP) using earth as heat source or sink are outstanding environmentally friendly energy systems which have high thermal efficiency when compared to conventional heating and cooling system. So government employs a policy and increase investment for expanding renewable energy market volume. Especially is established a system for obligatory usage of renewable energy to achieve 5% renewable energy diffusion rate by 2011. And the market demand for the ground source heat pump is rapidly growing due to its strong advantages. However domestic situation usually have been depended on the import of ground source heat pumps. In this paper, the results of development of a ground source heat pump using refrigerant R410A are reported.

• 설비공학논문집
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• 제15권7호
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• pp.586-594
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• 2003

The performance of the condenser installed in the air-conditioning plant room of a high-rise building was studied numerically. The effect of the draft direction on the performance of an air-conditioner was analyzed. The on-coil temperature of the condenser was investigated by varying the arrangement and location o( the condenser in the air-conditioning plant room. The performance of an air-conditioner was also evaluated by using COP (coefficient of performance) and CGPI (condenser group performance indicator). The condenser in an air-conditioning plant room should be arranged in such a manner that the fan of the condenser is facing the outside of the building to exhaust the hot air directly, The model by which the condenser is located at the lower-left end of an air-conditioning plant room can prevent the hot air from reentering, and allow indrafting of fresh air. When the direction of draft is to the frontal face of the building, the performance of the condenser above 30th floor is degraded.

• 설비공학논문집
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• 제18권3호
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• pp.211-217
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• 2006

The three-dimensional numerical analysis has been carried out to figure out the effect of the thermoelectric element thickness on the thermal performance of the thermo-electric micro-cooler. The small-size and column-type thermoelectric cooler is considered. It is known that tellurium compounds currently have the highest cooling performance around the room temperature. Thus, in the present study, $Bi_{2}Te_{3}$ and $Sb_{2}Te_{3}$ are selected as the n- and p-type thermoelectric materials, respectively. The thermoelectric leg considered is less than $20{\mu}m$ thick. The thickness of the leg may affect the thermal and electrical transport through the interfaces between the leg and metal conductors. The effect of the thermoelectric element thickness on the thermal performance of the cooler has been investigated with parameters such as the temperature difference, the current, and the cooling power.

• 설비공학논문집
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• 제21권1호
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• pp.55-62
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• 2009

Relatively low cycle performance of a conventional $CO_2$ system is partly due to significant increase in friction loss in the expansion process, since the pressure drop across the expansion device is considerably large compared to a conventional refrigeration cycle. To recover friction loss and increase refrigeration effect by providing isentropic expansion, a rotary vane type expander has been designed. Performance of the designed expander has been investigated by numerical simulation. With the pressure condition of 9 MPa/4.5 MPa and inlet temperature of $35^{\circ}C$, volumetric, isentropic, and mechanical efficiencies of the expander are calculated to be 58.1%, 101.1%, and 78.8%, respectively, resulting in total expander efficiency of 46.3%. With this expander, COP of a $CO_2$ refrigeration cycle is estimated to be improved by about 14%.

• 한국지열·수열에너지학회논문집
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• 제11권2호
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• pp.1-6
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• 2015

The horizontal earth-to-air heat exchanger (HEAHES) thermal performance is excellent on cooling and heating season in hot arid regions was reported. But the HEAHES thermal performance results is difficult to find on intermediate season. This paper was performed full scaled experiment to investigate HEAHES thermal performance on intermediate season (Oct. 10th ~ 12th Nov. 12th). When the air entering to HEAHES is the lowest $2.3^{\circ}C$, outlet air temperature from HEAHES is $15.95^{\circ}C$ through PVC pipe that buried length 60m and depth 3m. When the air entering to HEAHES is the highest $24.8^{\circ}C$, outlet air temperature from HEAHES is $22.05^{\circ}C$. During intermediate season, the HEAHES COP is 2.71 in daytime and 6.53 in evening.

• 설비공학논문집
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• 제18권5호
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• pp.434-442
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• 2006

In a two-stage compression $CO_2$ transcritical cycle, application of a scroll expander-compressor unit has been considered in order to improve the cycle COP. For both expander and 1st stage compressor, scroll wrap profile which was originally designed for a R410A air-conditioning cycle mechanism was used with minor modifications: wrap height and involute end angle were adjusted for required displacement volume and built-in volume ratio. For pressure condition of 10 Mpa/3.5 MPa and expander inlet temperature of $35^{\circ}C$, 25% improvement in COP was obtained by using expander-compressor unit. As evaporator pressure increased, COP improvement was lowered mainly due to decreasing compressor peformance.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.46-51
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• 2006

In order to utilize the refrigerants condensation heat of condenser on the absorption chiller system, the solution cooling condenser(SCC) were proposed, which weak solution of absorber outlet use as a cooling water. As the UA of the solution cooling condenser increased, increasement of COP is about maximum 0.09 in occasion of single effect and is about maximum 0.08 in occasion of double effect series flow. In the case of heat exchanger efficiency is about 0.85, it's increments are 0.08 and 0.072, each. And solution cooling condenser is a more effective device in the single effect absorption system more than double effect system for the principle of operation. In order to increases the heat of solution cooling condenser, if reduce the flow rate of cooling water or the value of UA, it makes COP increase a little, but it brought COP decrease because of increasing the pressure of system.

• 한국지열·수열에너지학회논문집
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• 제18권4호
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• pp.22-32
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• 2022

To reduce energy consumption and CO₂ emission in building sector, a ground source heat pump system has been highly adopted due to its high efficient by many regulation. A certification system has been operated to distribute reliable and high-efficient heat pump units. In this study, the performance status of the recently certified ground source heat pump unit with components was investigated. All heat pump units certified from 2015 to 2020 were water to water heat pump types. Compared to the past, higher capacity systems over 400 kW have been certificed. The cooling COP of the heat pump unit based on certification criteria showed higher value than the heating COP. It is highly recommended to revise the certified criteria values considering operating conditions individually. Most of ground source heat pump units have employed scroll type compressors and plate type heat exchangers with HFC refrigerant.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제27권4호
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• pp.369-379
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• 2013

최근 대학에 진학하는 이공계 신입생들의 상당수가 정상적인 전공과목이수가 어려울 만큼 수학과목에 대한 기초수학능력이 심각한 수준으로 저하되어 기초수학능력 및 대학 수학과목의 성취도를 향상시키기 위한 다양한 방법을 모색하고 있다. 이와 관련하여, 2012학년도 M대학교 이공계열 신입생 666명을 연구 대상자로 선정하여 이공계 신입생의 모집전형별 고교내신등급, 대학 성취도와 대학수학 성취도 사이의 관계를 비교 분석하였다. 그 결과 다음과 같은 결론을 얻었다. 첫째, 고교내신등급이 상대적으로 좋은 수시모집 학생들보다 고교내신등급이 상대적으로 낮은 정시모집 학생들의 대학 1학년 성취도와 대학수학 성취도가 더 높게 나타났고 대학수학 성취도가 높은 학생들의 대학 1학년 성취도가 높았다. 둘째, 이공계열 전체 뿐만 아니라 각 모집전형별 이공계 신입생들의 대학 1학기 성적이 대학 2학기 성적에 매우 강한 영향을 준 것으로 나타났다. 셋째, 기초학력보충교육 통과자들과 미통과자들의 기초보충교육 성적과 대학 1학기와 대학수학 1의 성취도 사이의 상관계수가 대학 2학기와 대학수학 2의 성취도 사이의 상관계수보다 높게 나타나 기초보충학습이 2학기 성취도 보다 1학기 성취도에 더 긍정적인 영향을 주었다.