• 대한설비공학회지:설비저널
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• 제31권3호
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• pp.53-58
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• 2002

대부분의 가정용 냉난방겸용 공기조화기(히트펌프)는 실외온도가 $5^{\circ}C$ 이하이고, 습도가 높은 저온고습조건에서 난방운전을 하면 열교환기 표변에 서리가 발생하고, 이로 인해 시스템의 성능이 떨어지게 된다. 이를 방지하기 위하여 어느 일정 조건이나 시간이 되면 히트펌프는 제상운전을 하게 되는데, 보통의 가정용 히트펌프의 경우 난방운전도중에 사이클을 냉방운전으로 전환하여 실외 열교환기의 온도를 높여 줌으로써 제상을 하는 방식 (Cycle reversing method)을 사용하고 있다. 이 방식은 부가적인 제상회로플 구성하 거나 히터를 첨가하는 등의 재료비 증가 없이 제상을 수행한다는 장점이 있으나, 시스템의 에너지 효율 측면에서 불리할 뿐만 아니라, 소비자의 입장에서 보면 제상운전이 진행되는동안에 따뜻한 바람이 공급되지 않아 쾌적한 공조를 제공받지 못한다는 단점이 있다. 본 자료에서는 먼저 제상방석에 관하여 그 종류와 특정을 알아보고, 최근에 진행되고 있는 착상 지연기술 중 어큐물레이터 내에 히터를 설치하는 방식(Viung C. Mei, et al., 2002, ASHRAE TRANSSACTIONS, V 108, Pt. 1)에 대하여 소개하고자 한다.

• 설비공학논문집
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• 제15권3호
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• pp.196-202
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• 2003

Two dimensional modeling was carried out to find the safety distance between the defrost heater and the plastic inner wall of domestic refrigerator Estimation was processed for the three cases; the estimation of plastic wall temperature (1) without any protection, (2) with an aluminum foil attached on a wall, and (3) with an aluminum shield installed between heater and wall. The former two cases are found to be dangerous during defrosting process, because the temperatures of inner wall reach above 80'C , which is the upper temperature limit of the wall material. The case with an aluminum shield is considered to be safe by maintaining the temperature of the wall in the range of 6$0^{\circ}C$ during defrosting process.

• 설비공학논문집
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• 제23권1호
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• pp.38-46
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• 2011

The hybrid defrost process combined with hot-gas bypass defrost and electric heater defrost was experimentally evaluated about its defrost performance in the fin-tube evaporators of household refrigerators. Also the hybrid defrost process was compared with only electric heater defrost process. The defrost efficiency of the hybrid defrost process was shown two times higher than electric heater defrost process. The defrost time of the hybrid defrost process was shorten about 10%~50% than electric heater defrost process. Thermal shock after defrost process was decreased about 50% for the case of the hybrid defrost. It was found that energy consumption ratio of defrost process was reduced up to 7.4% compared with 22.4% of electric heater defrost at the condition of $25^{\circ}C$ ambient temperature.

• 설비공학논문집
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• 제10권6호
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• pp.649-657
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• 1998

In this study, the effects of the various conditions of frosting and defrosting on the behavior of defrosting in a fin-tube heat exchanger have been examined experimentally. The electric heater is used for defrosting in a fin-tube heat exchanger It is shown that there are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after the completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering the degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of the frost irrespective of the frosting condition. The defrosting behavior is affected by the frosting density as well as the frost accumulation, which vary with the experimental operating conditions during the frosting period. The heat loss to the surrounding air decreases, and the melting and defrosting efficiencies show high values with decreasing heat input.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.529-534
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• 2003

Comprehensive study on the system, including blower and ducts, of HVAC device of a vehicle has been carried out for improvements of noise characteristics. The parameters of design improvements are concerned with geometric informations such as the shape of ducts and presence of a windshield window. Test results show that noise level increasing the following order: HV (HD) < V (D) < BH ${\sim}$ BHV (BHD) < B (B, H, V, D denote for blower, heater unit, vent duct, defrost duct, respectively). The effects of windshield glass on the noise level in the case of defrost mode are pronounced and the effects of the geometry of ducts on the overall HVAC noise prove to be not small.