This project belongs to the field of light industry, with disciplines such as refrigeration and low-temperature engineering, and serves special equipment and similar equipment for the household appliance industry. It mainly conducts research and development of small refrigeration units based on the natural refrigerant carbon dioxide to provide high-quality refrigeration equipment for refrigerated food and beverages. Refrigeration makes human life better. Refrigeration devices provide people with comfortable life and safe food. At the same time, they also face global environmental and energy problems. There are hundreds of millions of refrigeration devices such as refrigerators, air conditioners, freezers, etc. around the world. Their refrigerants cause damage to the atmospheric ozone layer and greenhouse gas emissions, and also consume a large amount of electricity. The energy conservation and emission reduction of refrigeration equipment has attracted increasing attention from the international community and the refrigeration industry. Using CO2 already existing in nature as an environmentally friendly refrigerant has become a broad consensus in the refrigeration field and a global technical trend.
The cycle mode, high and low pressure conditions, refrigeration equipment and control of CO2 refrigeration units are very different from traditional systems. Used in freezers, it faces technical problems such as high operating pressure of transcritical refrigeration cycle systems (about 100bar, 5-6 times that of HCFC refrigerant systems), complex heat exchange and throttling processes, relatively high energy consumption, and highly compact structural requirements. In response to these problems, this project pioneered a CO2 small integrated refrigeration system, carried out systematic research from aspects such as system structure optimization design, safety design, performance optimization, electrical control system design and mechanical manufacturing process, and successfully applied it to beverage freezers. The main innovation results are as follows:
(1) Creatively proposed to adopt a natural refrigerant CO2 modular integrated refrigeration unit system structure, which is placed at the bottom of the freezer in a drawer manner; the modular unit has a compact structure and small size, which reduces material consumption and extends product life by more than 5 years; When the unit fails, it can be replaced with a new refrigeration module within 3 minutes, which solves the problem of rapid replacement of the refrigeration device without affecting the refrigeration performance in the freezer.
(2) The integrated optimization design of the CO2 refrigeration system and the electrical control system was realized for the first time; the structural optimization design, safety design and electrical control system design methods for the high-pressure CO2 transcritical cycle refrigeration system were established; and the mechanical manufacturing process method was successfully solved.
(3) For the first time, the influence of multiple parameters such as optimal exhaust pressure, evaporation temperature, regenerative performance, capillary throttling, refrigerant charge volume, circulating air volume, and air duct structure on the cooling capacity and performance of the CO2 integrated freezer system was systematically studied and mastered for the first time. It has made a breakthrough in proposing the use of variable diameter heat exchange tubes, and implemented targeted enhanced heat exchange and energy-saving measures through research on the heat transfer characteristics of the supercritical region on the refrigerant side of the heat exchanger and research on the throttling characteristics of the capillary transcritical region. Effectively improve the system COP.
(4) For the first time in China, the optimization of system operating parameters in a high temperature and high humidity environment (ambient temperature 40.6℃, humidity 75%) was achieved, successfully solving the problem of uneven temperature distribution in the cabinet. The performance of the CO2 freezer product developed is superior to the national, industry standards and the U.S. Coca-Cola Company Standards. The COP is 17% higher than that of similar products in the world and is 5% more energy-saving than traditional freezers.
It has obtained more than 20 national patents (including 4 invention patents), published more than 10 papers, and has been cited more than 60 times by others.
This project has reached the international leading level through third-party testing, novelty search and scientific and technological achievement appraisal. This technology fills the domestic gap. The developed products use natural environmentally friendly refrigerants to replace traditional HFC refrigerants, which can reduce direct greenhouse gas emissions by 99%, promote the advancement of CO2 refrigeration technology, and occupy an advantageous position in international market competition. Scientific and technological achievements have been industrialized in Haier Group and have been on the market since 2008, and their products have been sold to well-known international companies such as Coca-Cola. More than 7 years of market testing have proved that the developed products have stable performance and safe and reliable operation. The cumulative sales of the product are 80,000 units, an increased output value of 450 million yuan, an added profit of 81.2 million yuan, an added tax of 28.06 million yuan, and a generated foreign exchange of 21.8 million US dollars.