Effect of three air supply modes on water evaporation process in limited space of frost-free refrigeratorEffet de trois modes d’alimentation en air sur le processus d’évaporation de l’eau dans l’espace limité d’un réfrigérateur à froid ventilé

https://doi.org/10.1016/j.ijrefrig.2020.09.012Get rights and content

Highlights

  • Air forced convection in frost-free refrigerator accelerates water evaporation.

  • The numerical results are in good agreement with experimental results.

  • The water evaporation rate during on cycle is 20 times of that during off cycle.

  • Effect of three air supply modes on water evaporation process were analyzed.

  • The water evaporation rate of annularly blowing air supply mode is the least.

Abstract

The air forced convection is utilized to cool foods in frost-free refrigerator, and it offers uniform temperature field and the fast cooling rate. But the air forced convection also accelerates the water evaporation from foods surface, which leads to foods dehydration. Numerical model of water evaporation process inside refrigerating compartment was validated by experimental results including the evaporated water mass, air temperature and relative humidity during compressor on /off cycle. The air supply modes have effects on velocity and temperature fields inside refrigerating compartment, and three air supply modes were compared: annularly blowing air (ABA) supply, upward blowing air (UBA) supply and forward blowing air (FBA) supply modes. The results show that the water evaporation rate during compressor-on cycle is 20 times of that during compressor-off cycle. The effect of air velocity on water evaporation process is greater than that of vapor partial pressure difference. The water evaporation rate for FBA supply mode is the largest due to its highest air velocity. The water evaporation rate of ABA supply mode is the least because of both its smaller air velocity and vapor partial pressure difference, and it is the best mode to decrease water loss.

Section snippets

Abbreviations

    ABA

    annularly blowing air supply mode

    UBA

    upward blowing air supply mode

    FBA

    forward blowing air supply mode

Experimental setup

The water evaporation process inside the refrigerating compartment during on/off cycle was studied on a three-temperature frost-free refrigerator with single-evaporator. The tested refrigerator has a total volume of 345 L, divided into 193 L of refrigerating compartment (RC), 35 L of variable-temperature compartment (VC) and 117 L of freezing compartment (FC). There are five RC layers in the experimental refrigerator, in which the first three layers from top to bottom contain 4, 2 and 1 air

Model establishment and numerical settings

A RC model based on COMSOL was developed to investigate the water evaporation process. The physical model mainly includes RC three-layer space, which was composed of walls, air supply ports, shelves and water pans, as shown in Fig. 1. Concurrently, proper simplifications of the physical model were made: some tiny RC structures were removed, such as chamfering and fillets, the outer edge of the water pan etc. For the numerical research, following assumptions were made to simplify the analysis:

  • )1(

Experimental results and model validation

The 24-h evaporated water mass of three RC layers was shown in Table 5. The results show that the evaporated water mass of R1 is the biggest with 37.5 g•24 h−1. And it is 9.5 g•24 h−1 and 12.2 g•24 h−1 higher than that of R2 and R3, respectively. The evaporated water mass of R2 is 28.0 g•24 h−1, slightly larger than that of R3.

Fig. 2 shows relative humidity and temperature curves of three RC layers during on/off cycle. During on cycle, the relative humidity of three layers decreases rapidly and

Conclusion

In this paper, the water evaporation process in a three-temperature frost-free refrigerator with single evaporator was investigated. And a RC model based on COMSOL was developed to study the water evaporation process caused by air forced convection. Then the effects of three air supply modes on the water evaporation rate of frost-free refrigerator were studied by numerical model. Detailed conclusion can be drawn as follows:

  • (1)

    During compressor-on cycle, the temperature of three layers decreased

Declaration of Competing Interest

I would like to declare that no conflict of interest exits in the submission of this manuscript, and manuscript is approved by all authors for publication.

Acknowledgments

The research is supported by the National Natural Science Foundation of China [No.51876154] and Major Science and technology innovation engineering projects of Shandong Province [No. 2019JZZY020813].

References (24)

Cited by (1)

  • Water evaporation rate correlation based on Dalton model of enclosed space in frost-free refrigerator

    2021, Case Studies in Thermal Engineering
    Citation Excerpt :

    Therefore, it is necessary to find the upper edge of the moisture boundary layer. The calculation is carried out by COMSOL model in previous studies [42], and then the coordinates of the points are input into the post-processing to obtain the vapor partial pressure at different heights at the center of the water plate surface. The frost-free refrigerator model consists of three RC layers, named as R1, R2 and R3 from top to bottom respectively.

View full text