• 대한기계학회논문집B
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• 제25권6호
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• pp.860-867
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• 2001

In this study, condensation heat transfer experiments were conducted with plate and shell heat exchangers(P&SHE) using R-22. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-22 in a vertical P&SHE. Two vertical counter flow channels were formed in the P&SHE by three plates of geometry with a corrugated trapezoid shape of a chevron angle of 45°. Downflow of the condensing R-22 in one channel releases heat to the cold upflow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-22 on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficients are significantly higher. A rise in the refrigerant mass flux causes an increase in the h(sub)r. Also, a rise in the average heat flux causes an increase in the h(sub)r. Finally, at a higher system pressure the h(sub)r is found to be slightly lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.

• 설비공학논문집
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• 제15권10호
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• pp.852-859
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• 2003

R407C is considered as an alternative refrigerant of R22 for air conditioners. An experiment was carried out to investigate the characteristics of the evaporation heat transfer and pressure drop for refrigerant R407C flowing in a fin-and-tube heat exchanger used for commercial air-conditioning unit. The experimental data were useful in analyze the effects of the temperature glide and superheat for R407C. Test were conducted at the conditions of inlet refrigerant evaporation temperature of 7$^{\circ}C$, inlet air relative humidity of 50%, and refrigerant mass fluxes varying from 150 to 250 kg/m$^2$s. Representative results show that the heat exchanger performance for R407C evaporation is significantly affected by the change of the flow pattern from two-phase to super-heated vapor flow.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3546-3552
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• 2009

본 연구에서는 천정 설치형 공조기 적용을 위해 연구가 활발히 진행되고 있는 알루미늄 평행류 증발기 해석 프로그램을 개발하여 190mm*650mm*25mm(W*H*D) 크기의 열교환기를 해석하였다. R410A냉매의 분배비가 일정하고 상하로 유동하는 2, 3 패스의 경우와 3 패스이고 분배비율(1:1:1, 1:2:2)을 달리할 때, 열교환 성능을 예측하였다. 계산 결과, 2 패스가 3 패스보다 국소 전열량이 30% 정도 높았지만, 건도에 따른 열전달계수는 25% 낮았으며, 3 패스의 경우, 분배비 1:1:1 보다 1:2:2가 냉매 압력손실이 높게 나타났다. 본 해석에서는 패스당 냉매가 균일하게 분포하는 것으로 가정하였으므로, 패스별로 불균일하게 유동되는 실제의 경우보다 열교환성능을 과대 예측하는 것으로 판단된다.

• 신재생에너지
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• 제7권4호
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• pp.30-36
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• 2011

The objective of this study is to investigate the effects of the refrigerant charge amount on the performance of a water-to-water ground source heat pump with a variation of compressor speed and the secondary fluid flow rate. The water-to-water ground source heat pump was tested by varying refrigerant charge amount from -40% to 20% of full charge. Compressor speed was changed from 30 Hz to 75 Hz and the secondary fluid flow rate was adjusted from 6 LPM to 14 LPM. For all test conditions, EWTs of an indoor heat exchanger and an outdoor heat exchanger were maintained at standard conditions of ISO 13256-2. The slope of the COP with the variation of charge amount is much steeper at undercharged conditions than that at overcharged conditions. For all compressor speed, the variation of the system performance according to charge amounts showed the similar trends. However, the optimum charge amount of the system increased a little with an increment of compressor speed. When the secondary fluid flow rate decreased, the system was optimized at higher refrigerant charge amount conditions.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.143.1-143.1
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• 2011

The objective of this study is to investigate the effects of the refrigerant charge amount on the performance of a water-to-water ground source heat pump with a variation of compressor speed and the secondary fluid flow rate. The water-to-water ground source heat pump was tested by varying refrigerant charge amount from -40% to 20% of full charge. Compressor speed was changed from 30 Hz to 75 Hz, and the secondary fluid flow rate was adjusted from 6 LPM to 14 LPM. For all test conditions, EWT of an indoor heat exchanger and an outdoor heat exchanger were maintained at standard conditions of ISO 13256-2. The slope of the COP with the variation of charge amount is much steeper at undercharged conditions than that at overcharged conditions. For all compressor speed, the variation of the system performance according to charge amounts showed the similar trends. However, the optimum charge amount of the system increased a little with an increment of compressor speed. When the secondary fluid flow rate decreased, the system optimized at higher refrigerant charge amount conditions.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.433-438
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• 2005

An AHX(Accumulator Heat eXchanger) consists of a commercial accumulator and an inner heat exchanger located inside of the accumulator. The AHX is used in multi air-conditioners to assure the liquid-phase refrigerant entering into the expansion device. This purpose is achieved by heat transfer between the refrigerant leaving the evaporator and the refrigerant leaving the condenser. In this study, the effects of AHX on the performance of a refrigeration system using H-22 were measured and the test results were analyzed. The operating characteristics of the refrigeration system with the installation of AHX were quite different from those without the installation of AHX. Therefore, it is required to find an optimum refrigerant charging amount and optimum operating conditions, when AHX is installed in the refrigeration system with an fixed area expansion device such as a capillary tube.

• 한국산학기술학회논문지
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• 제16권8호
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• pp.5045-5050
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• 2015

현대 주택이 고기밀 고단열로 건축되기 때문에 에너지 절감의 이점이 있는 반면 오염된 공기로 인한 많은 부작용이 발생하고 있다. 이런 부작용을 해결하기 위해 환기장치를 사용하여 실내 공기 환경을 개선하고 있다. 본 연구에서는 자동차용 에어컨의 열교환기로 사용되고 있는 평행류형 열교환기의 배기열 회수 환기장치로 적용 가능성을 알아보기 위해 냉매 충진량에 따른 열교환 효율 특성을 시험적으로 평가 하였다. 본 연구에서 사용된 히트 파이프는 환기장치에 적용이 가능하도록 분리형으로 제작되었다. 작동유체는 R22 냉매이고 유체의 충진량은 40~60(%vol.)로 10(%vol.) 단위로 충진 하였다. 환기량은 전면풍속을 기준으로 0.3~1.5m/s로 0.3 m/s 간격으로 바꿔 가며 측정하였다. 시험결과 최대 효율을 가지는 냉매 충진량이 환기량에 따라 다름을 알 수 있었고, 실험 결과 분석을 통하여 분리형 히트파이프의 환기량에 따른 최적 냉매 충진량을 찾을 수 있었다.

• 한국산학기술학회논문지
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• 제9권3호
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• pp.587-592
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• 2008

이산화탄소 냉매 시스템용 내부 열교환기의 성능을 조사하기 위하여 4종류의 내부 열교환기를 사용하여 냉방운전조건에서 실험을 수행하였다. 내부 열교환기의 길이, 관 개수, 운전조건, 형상 변화에 대한 영향이 연구되었다. 내부 열교환기 길이가 증가할수록 능력과 효율은 향상되었다. 압력강하는 고압측보다 저압측에서 더 크게 나타났다. 가스쿨러의 온도가 높아질수록 능력과 효율은 선형적으로 증가하였으며, 증발기의 운전조건은 과열도보다는 이상영역을 설정하면 효율증대 효과 측면에서 유리하였다. 마이크로 채널의 경우가 튜브보다 능력과 효율이 크게 우수하였지만 압력강하 측면에서는 크게 불리하였다.

• 설비공학논문집
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• 제17권12호
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• pp.1132-1138
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• 2005

Recently, production and use of freon substances are restrained due to depletion of ozone layer and global warming. In this aspect of environmental problems, the best solution is to use the natural refrigerant such as ammonia. Thus, this study is to find the optimal operating conditions by comparing the performance between the shell and tube type and shell and disk type heat exchangers using the ammonia refrigerant, and to verify the superiority of the shell and disk type heat exchanger that is not used in field of refrigeration and air conditioning. Finally, this study shows that the shell and disk type heat exchanger is applicable to the ammonia refrigeration system, and this system minimizes the refrigerant charge and installation space.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.477-480
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• 2007

Inlet fluid temperature of the BRE in the geothermal heat pump system depends on heat exchange rate between the refrigerant of the heat pump and the leaving fluid from the BRE. Because the outlet fluid temperature of the BHE varies with time, inlet fluid temperature has to vary with time. In this study, the module to calculate inlet fluid temperature is developed, which can consider the time-varying outlet fluid temperature and the heat exchange capacity of the heat pump. It is assumed that heat loss or gain of the leaving fluid from outlet to inlet of the BHE is negligible, except when the fluid contacts with the refrigerant of the heat pump. This module is combined with TOUGHREACT, a widely accepted three-dimensional numerical simulator for heat and water flow and geochemical reactions in geothermal systems and is applied to data analyses of the thermal response test.