Research Papers

Study on the Liquid Refrigerant Defrosting System and the Defrosting Rule

[+] Author and Article Information
Meng Wang

Refrigeration Engineering Research Center of
Ministry of Education of
People's Republic of China,
Tianjin University of Commerce,
Tianjin 300134, China
e-mail: wangmeng155@126.com

Runqing Zang

Refrigeration Engineering Research Center of
Ministry of Education of
People's Republic of China,
Tianjin University of Commerce,
Tianjin 300134, China
e-mail: zrqing@tjcu.edu.cn

Hai Feng

Refrigeration Engineering Research Center of
Ministry of Education of People's
Republic of China,
Tianjin University of Commerce,
Tianjin 300134, China

Chaoqun Yu, He Wang, Chenxu Zhang

Refrigeration Engineering Research Center of
Ministry of Education of
People's Republic of China,
Tianjin University of Commerce,
Tianjin 300134, China

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received December 27, 2017; final manuscript received May 10, 2018; published online June 25, 2018. Assoc. Editor: Wei Li.

J. Thermal Sci. Eng. Appl 10(5), 051023 (Jun 25, 2018) (7 pages) Paper No: TSEA-17-1507; doi: 10.1115/1.4040284 History: Received December 27, 2017; Revised May 10, 2018

The liquid refrigerant defrosting (LRD) is a defrosting method which leads the liquid refrigerant in the high-pressure reservoir to the frosting evaporator. The refrigeration process is continuous during the defrosting period, which increases the defrosting frequency. Compared with the traditional defrosting method, no large fin spacing should be left to reduce the defrosting frequency. The system can recover all the defrosting cooling capacity to improve the subcooling, so that the indoor air temperature fluctuations are avoided. In order to explore the effect and the rule of the LRD, the defrosting experiments were carried out in different frosting mass under the condition of the cold storage temperature of −20 °C. The defrosting time, temperature rise value, cooling capacity, and compressor power consumption value were calculated at the different frosting mass. Interpolation and applying the curve fitting equation helps to obtain remaining values. The relative humidity was calculated by the frosting mathematical model. Finally, the relationship between the coefficient of performance (COP) and the defrosting cycle (the sum of the defrosting time and the frosting time) was obtained. The experiments and theoretical research showed that the fluctuating value of cold storage temperature was about 5 °C and the defrosting time was about 30 min during the defrosting process. In the case of the relative humidity of 70%, 80%, 90%, the optimum defrosting cycle of the experiment was 16.4, 10.9, 7.5 h and the frosting mass was 2.66, 2.90, 3.22 kg, and the maximum COP was 1.51, 1.48, 1.45.

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Fig. 1

The principle of the LRD system

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Fig. 2

The physical drawings of the LRD system: (a) duplex air cooler and (b) solenoid valve group and pipeline connection

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Fig. 3

The program flow diagram of the defrosting model

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Fig. 4

The program flow diagram of the defrosting COP

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Fig. 5

The relationship between the defrosting time and the frosting mass

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Fig. 6

The relationship between the cold storage temperature increase and the frosting mass

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Fig. 7

The relationship between the cooling capacity and the frosting mass

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Fig. 8

The relationship between the compressor power and the frosting mass

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Fig. 9

The relationship between the frosting mass and the time

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Fig. 10

The relationship between COP and the defrosting cycle



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