The refrigerant is a key issue to achieve energy saving and system performance improvement in refrigerators. The technology development of zeotropic mixture in refrigerators was summarized including Linde-Hampson refrigeration cycle, auto-cascade refrigeration cycle to accomplish -40°C and lower temperature. On the other hand, the application of zeotropic mixture in dual-temperature refrigerators was also investigated. In addition, this paper reviewed the choose of mixture component and composition optimization, two-phase flow and heat transfer, system configuration, composition shift and changing concentration attribute. These studies with unique features eventually extend the research methods regarding zeotropic mixture in refrigeration field. Based on the future trend of refrigerant, the application of hydrocarbons in refrigerators was described and the key development trends were proposed. This review aims to promote the use of zeotropic mixture refrigerant in refrigerators, which can bring technology innovation and industrial upgrading of refrigerator industry.

Refrigerator as the main storage place of family food, is an indispensable home appliance in daily life. With the unceasing development of refrigerator industry, many refrigerator preservation technologies have appeared to achieve a better preservation effect. Nowadays, the existing refrigerator preservation technologies mainly conclude traditional preservation technologies, such as precise temperature control, partition storage and gas control, new preservation technologies, such as electric field, magnetic field, light and plasma, and enterprise-specific refrigerator preservation technologies. Through literature collection and market research, this review summarizes the existing refrigerator preservation technologies and combines with the development trend of contemporary intelligent preservation technologies. The purpose is to provide direction or reference for the research and development of modern household refrigerator preservation technology and consumers' purchase choice.

Numerical models were established for refrigerators under free and embedded conditions. The airflow and heat dissipation in the compressor compartment were simulated. Then the reliability of the models was validated by experiments. The simulation results showed that, compared with the free state, the airflow resistance of the built-in refrigerator increased between the compressor compartment and the outside. The main flow direction switched from “side in side out” into “bottom in bottom out”. The total air volume dropped by 28.6%, the short circuit air volume increased by 32.2%, which raised the inlet air temperature. Hence, the condenser surface average temperature increased by 13.9℃, and the average temperature on the top of the compressor increased by 27.6℃. In the embedded state, the heat dissipation of the condenser deteriorated, which increased the compressor pressure ratio and eventually led to the power consumption of the refrigerator increasing by 13.66%. This paper can provide theoretical guidance for the optimization of heat dissipation performance of the embedded refrigerator.

Refrigerator doors may frequently suffer opening and closing process for the commonly used frost-free refrigerator. The uniformity of temperature in each compartment of refrigerator will be destroyed during the door opening and closing process, resulting in the damage of food storage quality. The purpose of this study is to develop a simulation method for the door opening and closing process of a frost-free refrigerator, and to analyze the temperature variation in each compartment of a typical frost-free refrigerator under the condition of door opening and closing. In the method of CFD dynamic grid, a whole door opening and closing process is divided into three sub-process, including the sub-process of door opening, the sub-process of door opening maintaining, and the sub-process of door closing. The total thermal loss is calculated through monitoring the average temperature of refrigerator and the average mass flow rate of outlet air for each discrete time point. The thermal loss of the refrigeration compartment, the variable temperature compartment and the freezer compartment under the same door opening and closing conditions is calculated, and the results show that the large increase rate of temperature in each compartment occurs in the door opening process, and low increase rate of temperature of temperature in each compartment occurs in the door closing process. The thermal loss in the freezer compartment is larger than that in the variable temperature compartment or in the refrigeration compartment, meaning that the temperature non-uniformity in the freezer compartment is the worst.

The air volume uniformity and temperature uniformity are key factors which affect the energy efficiency. To analysis the top-mounted force-aired refrigerator with centrifugal fan, numerical simulation and experimental vertification are used and an optimal design of air volume uniformity has been worked out. Firstly, a guide structure should be added near the outlet of the fan to change the direction of air-out. Secondly, the area of air outlet should be modified to enhance the air uniformity. Finally, the experimental verification shows that the temperature difference between left and right part of freezer can be reduced from 3℃ to 0.1℃ with the optimal design.

At present, in the research and development and design of large-volume inter-cooled refrigerators, due to the technical limitations of thin-wall technology and traditional structures, there is a lack of methods to further increase the volume ratio of refrigerators. To solve this problem, based on a prototype machine, a new structure of horizontal evaporator and its supporting air duct was designed. The CFD simulation of the horizontal evaporator refrigerator is carried out, and the evolution law of the internal flow field characteristics of the horizontal evaporator air duct and the cabinet is analyzed. It is found that at the same speed of the fan, the air volume at the left and right sides of the refrigerator with a horizontal evaporator is more even than that of a refrigerator with a vertical evaporator, and the total air volume is equivalent. The performance test verifies that the tested flow field characteristics and transient temperature state are consistent with the simulation. The performance test verifies that the tested flow field characteristics and transient temperature state are consistent with the simulation. Under the premise of the same surface temperature of the evaporator, the temperature of the refrigerating compartment drops quickly and the cooling capacity is sufficient.

The flow process of an air duct of a small volume three-door refrigerator was numerically simulated by using the finite element method. The flow field characteristics and air volume distribution were analyzed. The reliability of the simulation model is verified by comparing the experimental results with the simulation results of the prototype. Based on the analysis of the simulation results of the prototype, the air duct structure was optimized, and the total simulated air volume was 35.94 m³/h, 18.03% higher than that of the prototype, basically meeting the requirements of the air volume after updating the product. At the same time, according to the standardization requirements, the diameter of the air duct of the volume refrigerator was simulated and explored. By comparing the simulated air volume of several groups of air duct with different diameters, the maximum air volume was finally determined when the diameter of the air duct of the refrigerator was 90 mm, and the maximum air volume was 37.46 m³/h.

Supermarket freezing cabinet have been rapidly developed due to the advantages of frost-free inside the box, large available space, and clean sanitation. However, the development is limited by the large power consumption of defrosting on the evaporator surface. Defrosting, especially in winter, is a very important topic for supermarket freezing cabinet. The application of hot gas bypass defrosting method reduces the power consumption of traditional electric heater defrosting, but there are also problems such as low suction temperature of compressor and long defrosting time in low temperature environment. In order to solve the above defrosting problems, the original hot gas bypass defrosting pipeline of air-cooled frost-free vertical freezing display cabinet in supermarket is reformed, and a new heat storage defrosting system is proposed. The heat exchanger with phase change heat storage is added to store the condensing heat during the operation of the system, and the heat is released in the process of hot gas bypass defrost to improve the suction temperature of the compressor. By testing the defrost performance of the modified system and the original system in different ambient temperatures, the following conclusions are drawn: in winter temperature, the defrost time of the modified system is shortened to 5% of the original system, and the defrost power consumption is reduced to 5.6% of the original system, which can solve the problem of low defrost efficiency of the original system in winter.

With the development of environmental protection and energy conservation and emission reduction technology, the energy saving of supermarket freezing cabinet has been widely concerned. Phase change storage technology can realize the transfer of energy space and time, and it has certain energy saving value when applied to evaporator of supermarket freezing cabinet. The NaCl solution with suitable phase change temperature and latent heat was chosen as phase change cooling material, and the amount of the material was determined by the calculation of heat load. The temperature fluctuation, power and power consumption of the cooling cabinet are compared in different working conditions, so as to analyze the energy saving and economy of the system. The results show that the temperature rise of the supermarket freezing cabinet with the addition of the storage material can be delayed up to 42.17% at the ambient temperature of 25℃ and 0℃, and the energy consumption can be saved up to 4.87%.

According to we finely adjust the suction valve of a type of light commercial compressor and design two kinds of suction valve. The input power, cooling capacity, coefficient of performance (COP) were obtained and analyzed, and verified by the test. The results show that the waist adjustment of the suction valve causes slight changes on the stiffness, which affects the closing angle of the suction valve in the process of movement. The suction valve with higher stiffness can be closed more timely, and the closing angle is 2.68° earlier, which reduces the back flow of the suction side, helps to increase the cooling capacity of the compressor, but causes the increase of the total input power. Finally, the COP of the suction valve with lower stiffness is higher, with an increase of about 0.005. The research conclusions provide ideas and basis for the further efficiency improvement of the compressor and the reliability design of the compressor valve.

Based on the experimental research on a stainless steel freezer, the necessary optimization on the refrigeration system, control system and auxiliary components are investigated for the cabinet switching compressor from fix speed to variable speed, including VSD compressor model selection, capillary and charge amount matching, defrost control and auxiliary component energy consumption optimization. Also, the energy consumption tests were carried out to verify the influence of the optimization. The test result shows that well matched variable speed compressor and optimized cooling system could reduce the energy consumption 23%. If plus optimization of control system and auxiliary components, the energy consumption could be reduced 37%.

DC power supply and utilization system integrates photovoltaic, energy storage, DC power distribution and flexible load, which is a research hotspot in the construction and electric power industry. As DC has no zero crossing, once DC arc is generated, it will be difficult to extinguish by it self, resulting in a high risk of fire, which requires effective identification and reliable protection of DC fault arc. Gives an overview of the research status of DC fault arc in photovoltaic, electric energy storage, electric vehicle, aircraft, ship and extra/ultra high voltage transmission, summarizes the detection methods of fault arc in typical scenarios, and analyzes the applicability of building DC power supply and utilization system. Combined with the real scene of the GREE PV future DC community, the test platform of fault arc is built for actual measurement. The simulation model of a single electric appliance and the built-in special algorithm for fault arc detection are proposed. The research direction of arc detection technology in building DC power supply and utilization system is pointed out, it can provide support for the establishment of fault arc test specification and the research of detection technology of building DC power supply and utilization system.

Since dish-washing machines were introduced into China since 1980's, the market penetration rate of dishwashers has been low. However, in recent years, the usage rate of dish-washing machines has been on the rise. Under the impact of the epidemic, they are getting more and more attentions. Studies the development background of China in recent decades to explore the impact of social development on the demand for dishwashers. It analyzes the relevant factors such as important national policies, education development and changes in the role of women, and looks into the development potential of dishwashers in the future by taking ten years as an era and combining with the developing trends of society. At the same time, during the epidemic period, log file analysis, one-to-one in-depth interview, focus group and other research methods were used to study user characteristics and excavate requirements for dishwashers from the perspective of real users, so as to provide reference for product iteration of dishwashers.

The square washing area in dishwashers with round coverage formed by common spray results in always insufficient washing at the four corners. Based on intensive study and analysis several specific mathematical curves, there proposes a variety of spray running track solutions with specific transmission mechanism design which can achieve high-coverage even full-coverage for square area. Furthermore, the generation theory and approving result are introduced and discussed in detail, thus having good guidance for innovative design of the dishwasher sprays.

In recent years, fruits and vegetables have been exposed to safety problems such as excessive pesticide residues and unqualified quality, so that the purification and cleaning effect of household fruit and vegetable purification and cleaning machine has attracted much attention. A household fruit and vegetable purification and cleaning machine with a volume of 6 L is used to carry out experimental research on surface dirt cleaning, sterilization and degradation of pesticide residues under three operation modes of "ultrasonic technology", "water hydroxyl technology" and "water hydroxyl ultrasonic composite technology". The results show that the effect of the household fruit and vegetable cleaning machine under the "composite technology" is the best, the sterilization rate is more than 90%, and the degradation rate of dichlorvos, dimethoate, ligulon and other pesticides is more than 90%; the cleaning ability of vegetable leaves and non vegetable leaves (grapes, etc.) is obvious, and the self-cleaning ability and the cleaning effect of crayfish are also very significant.

By analyzing the current situation, advantages and disadvantages of desalting rate of "head cup water" of large flux reverse osmosis water purifier in the market, and combining the actual use situation, a new technical scheme to improve the desalting rate of "head cup water" is proposed from the user experience, so as to realize zero aging water. This scheme can effectively improve the desalting rate of "head cup water", it has a certain effect on prolonging the life of RO membrane of reverse osmosis water purifier with low cost. According to the actual use of intermittent water by users, through the application of this technology, the whole process of pure water effluent from reverse osmosis water purifier can meet the standard, the desalination rate is more than 85%.

At present, the research on the refrigerator door mainly focuses on the improvement of the strength and deformation of the door, and the door has a relatively large dimension in the thickness direction. The thickness and material of the door body are different, and the correlation between the door body strength and the strength of the door body is also less researched. Aiming at such problems, taking the existing refrigerator door body as the research object, the refrigerator door body with different material panels is thinned according to the same amplitude, and the change of the deformation amount is studied. Through simulation comparison and analysis, after the door body is thinned to the same thickness, the deformation of the color panel door body and the glass door body. And it was verified through experiments that the deformation of the color panel door body is obviously smaller than that of the glass door body, which is in line with the simulation results, which further verifies the feasibility of replacing the door panel with color panels.

The refrigerator liner is mainly made of HIPS at present. During the production and use of the refrigerator, the liner cracking will occur which will adversely affect the sales and use of the refrigerator. To the refrigerator liner, it is generally believed that there are two main types of refrigerator liner cracking, one is mechanical stress cracking caused by excessive mechanical stress, and the other is chemical stress cracking caused by the increase of internal stress, the stress is mainly caused by chemical medium corrosion, especially when the refrigerator liner under both stress of mechanical and chemical effect. By analyzing the effects of stress and chemical corrosion on the high-gloss and low-gloss HIPS extruded sheets of different formulations, and proposes ideas for the improvement of the inner tank.

The carrier frequency of air conditioning PFC (Power Factor Correction) technology is generally 35~40 kHz, the energy storage inductance is large. To improve the competitiveness of the product, the ultrahigh frequency PFC (UHF PFC) control technology is proposed, and the carrier frequency to 100 kHz, energy storage inductance is greatly reduced. UHF PFC control technology can improve bus voltage and power factor by double loop control of voltage loop and current loop, improves CPU execution efficiency through algorithm optimization to realize simultaneous control of dual motor and UHF PFC. UHF PFC technology reduces THD value of harmonic component in current through duty cycle feedforward technology, then reduce harmonic pollution and improve quality factor. The experimental results show that the scheme can not only meet the technical requirements of air conditioning, but also improve the cost performance of products, and meet the reliability verification.

The remote control and other low-power devices use the internal low-speed oscillator as the sub-clock. When the chip sleeps, only the internal low-speed oscillator can run, and the accuracy of the internal oscillator of the chip is very low. If the timing function is set on the remote control, the timing accuracy also low, affects the user's use, therefore, proposed a method of using the internal high-speed oscillator to calibrate the internal low-speed oscillator, to improve timing accuracy.

Sweeping function is an important function of air conditioning to ensure the comfort of users. However, if the sweeping parts are stuck by objects in the process of sweeping, it will easily lead to equipment failure, if people's fingers are accidentally stuck, it will cause human injury. Therefore, the photoelectric switch is often used as a safety detection and protection device to judge whether the detection operation is in place or prevent the hand from being pinched. In the prior art, there is a problem of false detection when using the photoelectric switch to prevent the hand from being pinched. Analyzes the existing problems and give an effective solution and optimization scheme.

At present, environmental sensing sensors widely used in air conditioners are mainly infrared sensors and cameras. Such optical devices cannot effectively protect privacy, which makes users have a repulsive mentality. And the cameras are greatly affected by light and cannot work around the clock. So they are not the best choice of environmental sensing sensors. Unlike these sensors, millimeter wave benefitting from the physical characteristics of electromagnetic wave, which can achieve high-precision distance, angle, speed measurement, as well as target identification and tracking, can almost work in the dark, strong light, haze, rain and snow and other bad weather without problem of privacy leakage, it is a very suitable choice of environmental sensor. The application of 60 GHz millimeter-wave radar on air conditioner proves its high data reliability and can be further studied.

The chassis components for air conditioning are composed of chassis and footing. The connection and processing methods include spot welding, tox riveting and rivet connection. However, spot welding and tox processing methods will have hidden danger of desoldering and riveting, and riveting process can directly see the riveting effect, and there is no hidden danger of missing riveting and riveting. Now, two kinds of riveting technology, swing roller riveting and hot riveting, are deeply studied. The tensile strength and shear strength of the samples after riveting were tested. The difference of shear strength between the two was not significant, while the tensile strength of hot riveting was significantly better than that of rotary riveting. Through the metallographic (OM) analysis of the two rivets, it is found that there is no phase transformation in the microstructure of the rotary riveting, while the transformation of ferrite to sorbite occurs in the microstructure of hot riveting rivets, and the mechanical properties are improved. In addition, this paper also discusses that swing roller riveting will cause uneven height of rivet head and even head of hot riveting, which will have a certain impact on tensile strength.

Refrigerator noise is one of the main performance indicators that users pay attention to during use. The sound power level evaluation method cannot accurately reflect the real noise fluctuation of the refrigerator. Inverter refrigerators have different sound power levels at different stages of the full refrigeration cycle. Using the method of sound pressure monitoring, study the noise change rule of the inverter refrigerator during the whole refrigeration cycle, obtain different noise spectrum distribution characteristics, analyze the causes of various types of noise, propose improvement and optimization plan and verify. By optimizing the speed control of the compressor, the whole cooling process a maximum noise reduction 1.8 dB(A). By optimizing the assembly structure of the damper and the air duct, the operation noise of the damper can be reduced by more than 2 dB(A). Through the sound pressure monitoring method, the noise fluctuation range during the full refrigeration cycle of the inverter refrigerator is evaluated, and the optimization direction of various noises is proposed. Proved by practice, some noise reduction schemes are applicable to different types of products.

In recent years, DOE has revised the standards and test methods of mobile air conditioning, which will be enforced from 2025. Compared with the original standard ASHARE 128-2001, this standard has great changes in the test method and energy efficiency requirements, which brings great changes to the research and development work and direction of portable air conditioning. Through the comparison of standards and the analysis of actual matching results, this paper analyzes the key characteristics of SACC and CEER of DOE standard portable air conditioning, which provides a certain reference for the development of DOE standard portable air conditioning.

Heat exchange capacity is the decisive factor of the energy efficiency of the air conditioner. Failure to clean in time will decrease heat exchange capacity and energy efficiency of the air conditioner. Based on this, the paper proposes a way for the auto-cleaning of the indoor and outdoor units of the air conditioner. The air conditioner achieve the function by the condense and frost of the indoor unit, four-way valve switch, fan of outdoor unit reverse, cleaning indoor unit, high temperature sterilization, frost of the outdoor unit, outdoor unit defrost and ventilation. By controlling the temperature of the inner plate, the surface of inner plate can be maintained above 56°C, effectively inactivating bacteria. Through the switch of four-way valve, the indoor and outdoor auto-cleaning processes are combined to shorten the function time and improve the user's experience. Finally, in order to ensure the effective and reliable operation of the product, the high-temperature and reliability were verified, and the result shows that the requirements were met under all working conditions. The paper provides a new way for the healthy function redization of air conditioner.

To ensure the stable operation of orbiting scroll was one of the core technical points in the design process of scroll compressor. In order to calculate the operation stability of the orbiting scroll more accurately, a certain type of scroll compressor was taken as the research object. According to the actual running state of the compressor, the force characteristics of the orbiting scroll were analyzed, and the mathematical model of the operation stability was deduced. So the complex problem of the operation stability of the orbiting scroll was transformed into the problem of solving the action point of the reacting force. Moreover, the linear relationship between support pressure and rotational speed was obtained through experiments, and the stability calculation model of the orbiting scroll was improved over the whole frequency range, and the theoretical criterion of the operation stability was put forward, which provides a theoretical reference for the design of the scroll compressor.

According to the requirements of the new version of GB/T 23137-2020 "Household and similar heat pump water heaters", a set of heat loss calibration system is designed. The system is mainly composed of calibration water tank, stirring pump, electric heating rod, power regulator, power meter, temperature protector, temperature measurement unit and data acquisition system. By testing and analyzing the thermal insulation performance, heat leakage and additional errors of the system, the test process is optimized and the accuracy of the water heater performance test is improved.

This disquisition is related to the aftersales data of multi-layer ceramic capacitors for air-condition, by means of the metallographic observation of the internal structure of MLCC. The main failure reason is that the mechanical stress causes the end electrode to crack. After checking the incoming, production transportation and other links, the results show that the main failure reason of MLCC is the excessive bending of PCB board in the process of installation and transportation, which leads to the failure of the capacitor under excessive mechanical stress. Therefore, the bending strength of the MLCC limit substrate of different materials, packages and capacitance values is obtained, which provides a corresponding numerical reference for the hardware design and improves the reliability design of the product.