Condensation Mechanism And Condition Analysis Of Multi-effect Condensed Refrigeration Units

With the development and wide application of the refrigerating technology, energy consumption and security issue of refrigeration equipment has attracted increasingly great attention from environmentalists and the general public. Proposal on promoting China's low-carbon economy has been classified as first proposal of NPC and CPPCC in 2010. Low-carbon economy is strongly supported. Nothing but energy-saving, high-efficiency and green environmental protection refrigeration equipment can seek develops and win the market in the low-carbon economy.Research on refrigeration unit was carried out in this thesis. Existing refrigeration unit has many problems in practical applications, high energy consumption and high failure rate, especially. Hence multi-effect condensed refrigeration unit combining air-cooled, water-cooled and transpiration-cooled in one was designed.Innovation and operating principle of multi-effect condensed refrigeration unit were analyzed. It became the most idea equipment for the refrigeration unit of low consumption, simple and compact structure, easy installation, low material consumption and low-cost.Condensation mechanism of multi-effect condensed refrigeration unit is quite complex. As viewed from thermodynamics, heat and mass transfer process that takes place in the multi-effect condensed refrigeration unit was analyzed. Meanwhile, wind directions, air volume, distribution of water currents and water spray volume had effects on mass transfer and heat transfer properties.The experimental apparatus of the refrigeration unit were built up. Hot tinning process copper-constantan thermocouples with high sensibility and naked probe were used to measure the multi-dot temperature in the experiment. Based on demarcating thermocouple and polynomial regression analysis, the results indicated that consistency and goodness of fit of hot tinning method of copper-constantan thermocouples were both very good. The measuring precision was within±0.05℃at-35-100℃. Copper-constantan thermocouples were suitable for quick and accurate temperature acquisition.3D temperature field for condenser of refrigeration unit was studied based on MATLAB. It was convenient to observe any section of 3D temperature field for condenser by means of contour slice function. Meanwhile, the temperature distribution of exterior and interior for condenser visualizing analysis became realizable. Comparative analyses of 3D temperature field transients for condenser of wind cooling combination and multi-effect condensed refrigeration unit demonstrated that, condensation effect of multi-effect condensed refrigeration unit was remarkable superior to air-cooled unit and refrigerating efficiency of refrigeration unit was notably raised.A ten-ton fresh-preserved store house was used as experimental monitoring subject. The relative humidity range was 60-98% RH and temperature range was 0-3℃in the fresh-preserved store house. Energy-saving experiments and safety and efficiency experimental researches of multi-effect condensed refrigeration unit were conducted under ambient temperature 36℃or so and relative humidity 55-87%. Major experimental results were showed as the followings:1. Per temperature fall time of multi-effect condensed refrigeration unit was only 0.38h. Electricity consumption saving of the multi-effect condensed refrigeration unit reached 46% over than air-cooled unit.2. In high temperature applications, the problems of high discharge temperature and excessive exhausting gas pressure in wind cooling combination compressor were removed by using multi-effect condensed refrigeration unit. Meanwhile,28.79℃compressor discharge temperature dropped,900 KPa exhaust pressure of compressor lowered, machine wear reduced, and remarkable energy-saving effect was obtained in multi-effect condensed refrigeration unit.3. High temperature structures of compressor were cooled by means of water flow in multi-effect condensed refrigeration unit. cylinder head temperature and crust of oil level temperature were 48.14℃,36.45℃respectively in the work of the compressor.34.14℃of cylinder head temperature and 20.23℃of crust of oil level temperature reduced than air-cooled unit. Multi-effect condensed refrigeration unit reduced compressor's working temperature and avoided effectively equipment damage due to compressor overheating. As a result, it offered protection for the safe operation of unit.