## 1 Introduction  
Some of the common household appliances are refrigerators, washing machines, clothes dryers, electric ovens, etc. [1]. Among the household appliances, the refrigerator is the most common one due to its indispensable nature and hence, is the most manufactured [1, 2]. Currently, there are over a billion domestic refrigerators worldwide [2]. The energy consumption of household appliances increases in proportion to its usage. Among these appliances, the refrigerator is one of the most energy-consuming devices [2]. It is estimated that more than 45% of the world food production would go waste if not for the refrigerators' cold storage and distribution [2]. Thus, improving their energy efficiency, efficient energy consumption, and prolonged life becomes imperative [1, 2]. There are different mechanisms to increase the efficiency of the refrigerator, namely, by improving the compressor performance, thermal isolation, heat exchanger design, implementation of optimum control in refrigerator operation [2], improvements in cabinets (such as insulation, improved gaskets), improvement in refrigeration systems (such as fan motors, high efficiency compressors), improved heat exchangers, advanced defrost mechanisms, etc. [1]. Environmental problems, such as global warming, have precipitated a large number of studies--on various factors--that affect the power consumption of a refrigerator to improve their efficiency [3]. On the evaluation of the efficiency and performance of refrigerators, [PERSON] and [PERSON] investigated the change in the performance of a refrigeration system using a Phase-change Material (PCM) cooling agent [4]. [PERSON] et al. investigated the change in the temperature of freezing and refrigeration chambers in a food storage refrigeration system according to its storage temperature and usage frequency in an empirical manner [5]. [PERSON] and [PERSON] mathematically studied the thermal effect of the fresh food compartment with a change in glass shelve locations in a domestic refrigerator. The moving variance and the finite difference approximation were used to analyze the thermal distribution and the temperature change rate, respectively, in their study. The results showed that the use of thermal maps to analyze the mean and variance of the temperature was an important tool to assess a good combination of shelf locations [6]. [PERSON] et al. experimentally studied the energy efficiency enhancement of a domestic refrigerator by replacing R134a with R436A without any mechanical alteration. The results showed that by replacing the R436A, the On time and energy consumption was reduced by 13% and 5.3%, respectively, for a day, and the optimum charge for R436A was reduced to 48% when compared to the charge of R134a [7]. [PERSON] and [PERSON] experimentally studied the energy and exergy analysis of a domestic refrigerator by comparing the hot-wall air-cooled (HWAC) and box type shell and tube water-cooled (BCTWC) condensers. The results showed that the coefficient of performance and the exergy efficiency of BCTWC was increased by 18-20% and 6.89-9.13%, respectively, when compared to the HWAC. In addition, the energy consumption of the BCTWC was reduced by 17% in comparison to HWAC [8]. [PERSON] et al. experimentally and numerically studied the temperature stratification of the fresh food and freezer compartments of the domestic refrigerator with bottom mount configuration. The results showed that the proposed design had a good distribution of airflow and hence, uniform temperature at the fresh food compartment. Furthermore, in comparison to the original design, the new design showed less ON stages for the compressor [9]. [PERSON] and [PERSON] conducted a comparison study between the computational fluid dynamics (CFD) and Artificial Neural Network (ANN) modeling of the air temperature fields inside the refrigerator cabins. The results showed that the ANN model produced a low absolute error of 0.8 K in comparison to 1 K of the CFD model.