• 한국소음진동공학회논문집
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• 제19권10호
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• pp.1012-1020
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• 2009

This research is focused on the experimental study of the noise induced by two-phase refrigerant flow in the evaporator. The two-phase flow in the evaporator has various flow patterns. The effects of two-phase flow pattern's characteristics on the noise of the evaporator are investigated experimentally. The experimental data shows that the generated noise is mainly related to the layout of the pipe and the certain two-phase flow patterns such as the churn and slug flow. Based on these results, we removed the unnecessary vertical pipe and changed the pipe diameter of the evaporator - inlet into small one in order to avoid the intermittent flow condition. The noise level of newly-designed inlet-pipe of the evaporator was measured experimentally by refrigerant-supplying equipment and compared with that of conventional one.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1059-1067
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• 2006

In order to develop a compact evaporator, experiments that show characteristics of evaporating heat transfer and pressure drop in the helically coiled minichannel were performed in our previous research. This study was focused on the performance analysis of helically coiled heat exchangers with circular minichannels with an inner diameter=1.0 mm. The working fluid was R-22, and the properties of R-22 were estimated using the REFPROP program. Numerical simulation was performed to compare results with the experimental results of the helically coiled heat exchanger. As the heat transfer rate and pressure drop were calculated at the micro segment of the branch channels, the performance of the evaporator was evaluated. The following conclusions were obtained through the numerical simulations of the helically coiled heat exchanger. It showed good performance when the flow rate of each branch channels was suitable to heat load of air-side. The numerical simulation value agreed with experimental results within ${\pm}15%$. In this study, a numerical simulation program was developed to estimate the performance of a helically coiled evaporator. And, an optimum helically coiled minichannels evaporator was designed.

• 설비공학논문집
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• 제6권3호
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• pp.175-181
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• 1994

This paper deals with the correlation of absorption rate in absorber and evaporation rate in evaporator. The evaporator consists of a copper tube of 10mm dia, and 600mm long and chilled water flowing through the tube is fed by the chilled water circulator. The flowrate of LiBr-water solution in the absorber plays a significant role in determining the magnitude of the heat transfer rate from chilled water to refrigerant There exists a flowrate of solution which has a maximum value of heat transfer. It is interesting to note that the absorption rate of absorber increases with increasing the heat transfer rate of the evaporator. Also, absorption rate increases with evaportation rate, and the ratio(the former/the other) depends on the inlet temperature of LiBr-water solution in the absorber. The heating capacity in the absorber is higher than the refrigerating capacity in the evaporator.

• 한국지열·수열에너지학회논문집
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• 제8권2호
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• pp.48-54
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• 2012

To analyze the cooling performance of fin-tube evaporator in the refrigerator truck using R744 according to frost growth, the analytical model of evaporator was developed under frost and non-frost conditions. The performance of fin-tube evaporator was investigated with frost thickness and indoor temperature. Besides, the performance of evaporator under frost condition was compared to that under non-frost condition. As a result, area of air passage and system performance were decreased as the frost thickness increased. The cooling capacity was reduced by 10%, 20%, 30% when the frost thickness was 0.7 mm, 1.1 mm, and 1.6 mm respectively. At these conditions, the block ratio was 31%, 48%, and 71%. In addition, the outlet quality of refrigerant was not over 1 when the frost thickness was 1.6 mm in spite of high indoor air temperature.

• 한국기계가공학회지
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• 제18권6호
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• pp.39-44
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• 2019

The evaporator is a key driver of an air conditioning system's efficiency. In this study, we study methods of maximizing the efficiency of a Massey Ferguson (MF) evaporator by measuring how the cooling performance of different shapes vary with temperature. We varied the tube insertion depth as well as the shape of the evaporator's header and tube. When we compare header shapes of "D", "Ellipse", and "Quadrangle" types, we find that the elliptical header creates the smallest pressure loss and the highest temperature difference. Between tube shapes of "Rectangular", "Projection", and "Circular" types, the "Projection" type tube creates the most temperature difference. We also investigated the depth of tube insertion in the header and find that tube insertion of 5 - 10 mm is feasible; we selected the depths of 5, 7, and 10 mm since they corresponded to approximately 30%, 50%, and 70% of the total width of the header. The tube insertion test demonstrated that a tube insertion depth of 7 mm creates the least pressure loss and the highest temperature difference. In conclusion, the optimal evaporator design uses an "Ellipse" type header, "Projection" type tube, and a tube insertion depth between 30 and 50% of the header width.

• 대한기계학회논문집B
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• 제37권3호
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• pp.205-212
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• 2013

본 연구는 평판 핀-튜브 증발기와 나선형 핀-튜브 증발기를 적용한 가정용 냉장고의 성능특성 비교를 통하여 기존에 사용하고 있는 핀-튜브 증발기를 나선형 핀-튜브 증발기로 대체할 수 있는 가능성을 고찰하는데 그 목적이 있다. 실험은 2단 15열의 평판 핀-튜브 증발기와 2단 15열에서 2단 11열까지 열 수를 단계적으로 감소시킨 3종류의 나선형 핀-튜브 증발기를 실제 냉장고에 적용하여 수행하였다. 핀-튜브 증발기의 열 수가 감소할수록 냉동시스템의 최적 냉매 충전량은 감소하였으며, 2단 13열과 2단 11열의 나선형 핀-튜브 증발기를 장착한 냉장고의 소비전력은 기존 2단 15열의 평판 핀-튜브 증발기를 적용한 냉장고 대비 각각 1.5%와 2.8% 감소하였다. 또한 내착상 실험결과 나선형 핀-튜브 증발기가 기존 평판 핀-튜브 증발기와 비교하여 같은 착상조건에서 3~7% 향상된 냉각능력을 보였다. 냉각속도 실험에서는 모든 증발기는 동등수준의 성능을 나타내었다.

• 한국산학기술학회논문지
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• 제20권7호
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• pp.353-362
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• 2019

그간 캐스케이드 냉동 시스템에 대해서 열역학적 해석은 다수 수행되었으나 증발기, 응축기, 인터쿨러 등 부품 해석을 통한 시스템 평가는 미진한 상태이다. 본 연구에서는 냉방 및 냉동 열교환기가 별도로 장착되어 있고 하부 사이클에 공랭식 응축기와 인터쿨러가 직렬로 연결되어 있는 캐스케이드 냉동 사이클에 대해 성능 해석을 수행하였다. 우선 증발기, 응축기, 인터쿨러 등 요소부품에 대해 모델링을 수행하고 R-410A를 사용하는 냉방 능력 8 kW, 냉동 능력 15 kW의 캐스케이드 냉동 사이클의 요소 부품의 - 상부 응축기, 하부 응축기, 냉방 증발기, 냉동 증발기, 인터쿨러, 압축기, 전자팽창변 - 설계를 수행하였다. 설계 사양에 대하여 외기 온도를 $26^{\circ}C$에서 $38^{\circ}C$로 변화시키며 해석을 수행한 결과 냉각 열량은 하부 증발기에서는 거의 일정하고 상부 증발기에서는 9% 감소, 인터쿨러에서는 63% 증가하였다. 한편 COP는 외기 온도의 증가에 따라 감소하였다. 인터쿨러가 작동하지 않는 사이클 대비 인터쿨러 사이클이 COP 측면에서 우위를 보였다. 또한 상부 응축기의 크기를 당초 설계치의 2배 증가시키면 하부 증발기 열량은 변함이 없는 반면 상부 증발기 열량은 4% 증가하였다. 한편 상부 응축기의 크기 증가에 따라 상부 사이클의 COP는 증가하는 반면 하부 사이클의 COP는 큰 변화가 없다. 또한 하부 응축기 크기를 2.8배 증가시키면 상하부 증발기의 열량 변화는 거의 없고 인터쿨러의 열량만이 8% 감소하였다. 아울러 하부 사이클의 COP는 응축기의 크기가 증가함에 따라 다소 증가하였으나 상부 사이클의 경우는 그 변화가 미미하였다.

• 설비공학논문집
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• 제24권10호
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• pp.711-717
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• 2012

A heat pump dryer for the frozen food needs to preheat the air to a certain temperature where condensation can efficiently occur. In this study, an analysis of a heat pump dryer performance with operating conditions, an analysis of supplying heat with internal and external evaporators and a warm-up experiment with the evaporators have been performed. The results showed that the external evaporator can significantly accelerate the warm-up time of the dryer, so that it can reduce power consumption greatly. The use of the external evaporator is more efficient for higher ambient temperature. In addition, it was found that COP decreases and the range of evaporating pressure for the evaporator becomes narrower as the condensing temperature of the condenser increases.

• 한국지열·수열에너지학회논문집
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• 제6권2호
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• pp.15-22
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• 2010

The natural refrigerants have used into HVAC equipments because the CFCs and HFCs have some environmental problems like high ODP and GWP. The carbon dioxide has small effect on the environmental problem but also good thermodynamics properties. In this study, the simulation study on the performance and characteristics of a $CO_2$ gascooler and evaporator using a fin-tube and microchannel heat exchanger has been conducted. Besides, the comparison of performance with operating condition was carried out in order to apply to the $CO_2$ heat pump system. As a result, the front sizes of a gascooler and evaporator using a microchannel were decreased by 63% and 58%, respectively, compared to those using a fin-tube. The performance of the fin-tube gascooler and evaporator were more responsive to the variation of operating conditions compared to that of microchannel. The pressure drop of a fin-tube heat exchanger was higher than that of a microchannel one.

• 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.