탑차용 냉동시스템에서 증발기의 서리성장에 따른 성능 특성 연구

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냉동시스템, 증발기, 서리, 성능계수
Refrigeration systems such as a general refrigerator, commercial refrigerator, and industrial refrigerator etc. became the necessities of life. The movable commercial refrigerating system is called ‘refrigerator truck’, and it keeps the fresh foods during the transport. Recently the food service industry has been developed due to the improved quality of life. The demands of package service have been increased for frozen foods from on and off line, so the refrigerator truck demands increased. In addition, the groceries are also increased the demand for centralization and localization. For this reason, a study on the refrigeration performance of refrigerator trucks is needed to maintain the high efficiency and reliability of the food transportation for long distance. However, the research is insufficient for the performance of refrigerating system in commercial refrigerator truck.
In the refrigeration system, when the surface temperature of cooling coil gets below the dew point temperature and it contacts with vapor of humidity, the porous frost gets to form on the coil during the operation. As the frost growth increase, the rate of air flow through the evaporator decreases leading to a large pressure drop accompanied by a sudden drop in heat exchanger performance. Also, frost in the low temperature condition is developed with the operating time, so it has an effect on the heat exchanger of efficiency degradation owing to heat resistance of frost. Therefore, it is in need to examine that the performance degradation caused by frost growth in the refrigerator truck. However, only few studies have reported on refrigeration performance considering frost growth.
Most of the theoretical models have been verified using a domestic refrigerator. However, simulation model of a refrigerator truck hasn't been developed so far. A simulation model is useful to study the performance degradation due to frost growth under different operating conditions for vehicle-mounted units. In this study, an analytical model of a refrigeration system was developed for the R404A refrigerator truck. Besides, the experimental test was carried out in order to verify the developed analytical model. To analyze the performance of refrigerator tuck in the psychrometric chamber, which were compared to the simulation results using the EES(Engineering equation solver) program for refrigeration system of refrigerator truck.
As a result, frost thickness was increased with the rise of the indoor air temperature and the compressor rotating speed, but increasing amount of frost was insignificant difference with outdoor air temperature. Furthermore, the optimal refrigeration capacity was decreased by 30% when operating time passed about three hours under basic conditions. In this case of simulation, we predicted the blocking ratio with operating condition to compare the experiment results. The lower indoor temperature, the COP decrement increased with the increasing of blocking ratio, whereas the higher indoor temperature, the decrement of refrigeration capacity increased with frost growth. The variation of indoor temperature, performance curve shows similar trends and a decreasing rate with blocking ratio. The decreasing rate in refrigeration capacity under a high temperature condition was steeper than that under a low outdoor temperature condition with blocking ratio. The refrigeration system of performance is sensitive reaction to high outdoor temperature condition at condenser. In addition, the variation of outdoor air velocity, the system performance was not greatly increased above 4 m/s because a sufficient amount of heat transfers from the refrigerant to air at the condenser. The maximum of the system COP was shown at the compressor speed of 1500 rpm for non-frost and frost condition, simultaneously. The performance under frost condition was more sensitive to the operating condition compared to that under non-frost condition.
Through this study, the performance data and optimal control method of system performance in refrigeration system can be provided and it will contribute to developing high efficiency refrigerator system in the movable truck.
Alternative Title
Study on the Performance of Refrigerating system in a Refrigerator Truck with Frost Growth
Alternative Author(s)
Kim Sanghun
조선대학교 대학원
일반대학원 기계공학과
Awarded Date
Table Of Contents

Contents ⅰ
List of Figures ⅳ
List of Tables ⅵ
Nomenclature ⅶ

제 1 장 서 론 1
제 1 절 연구 배경 1
제 2 절 국내·외 연구 동향 5
제 3 절 연구목적 8

제 2 장 실험장치 및 방법 10
제 1 절 실험장치의 구조 10
제 2 절 실험장치의 제원 및 데이터 해석 15
1. 온도측정 15
2. 압력측정 17
3. 인버터 18
4. 압축기 소비동력 측정 20
5. 냉매의 질량유량 측정 21
6. 온·습도 sampler 23
7. 냉동용량의 계산 25
8. 풍량측정장치 26
9. 자료 수집 및 처리 프로그램 31
제 3 절 실험조건 및 방법 33

제 3 장 탑차용 냉동사이클 모델링 35
제 1 절 압축기 모델링 38
제 2 절 열교환기 모델링 39
1. 냉매측 열전달 상관식 41
2. 공기측 열전달 상관식 44
3. 서리층 모델링 47
제 3 절 팽창장치 모델링 50
제 4 절 해석 조건 51

제 4 장 결과 및 고찰 52
제 1 절 기본조건에서의 검증실험 결과 및 고찰 52
1. 냉매충전량에 따른 성능 고찰 52
2. EEV 개도 변화에 따른 성능 고찰 54
제 2 절 착상조건에서의 성능변화 결과 및 고찰 56
1. 기본조건에서 운전시간에 따른 서리성장과 성능 고찰 56
2. 실내온도 변화에 따른 차단비와 성능 고찰 59
3. 실외온도 변화에 따른 차단비와 성능 고찰 61
4. 압축기 회전속도 변화에 따른 차단비와 성능 고찰 63
제 3 절 무착상 조건 성능과의 비교 해석 및 고찰 65
1. 실내온도 변화에 따른 성능 고찰 66
2. 실외온도 변화에 따른 성능 고찰 68
3. 실외 풍속 변화에 따른 성능 고찰 70
4. 압축기 회전수 변화에 따른 성능 고찰 72

제 5 장 결 론 74

조선대학교 대학원
김상훈. (2013). 탑차용 냉동시스템에서 증발기의 서리성장에 따른 성능 특성 연구.
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General Graduate School > 3. Theses(Master)
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