Energy Analysis And Experimental Study Of Multi Temperatures Plane Net Belt Quick-Freezers

At present, plane mesh belt quick-freezers used to frozen food usually set the evaporation temperature at -38～-42 ℃. By analyzing the investment and operation cost, it’s found that there is a shortcoming that the quick-freezers are generally low efficiency. It is not only because of the design of the air distribution which related to the wind speed field and temperature field, but also because of the design of the evaporation temperature which is irrational. Quick-freezers designed at one evaporation temperature can’t adapt to temperature changes during food freezing process, COP of the refrigeration system is low.Therefore, according to the characteristics of the food freezing process, the subject uses different evaporation temperatures during pre-cooling, crystal and deep cold three stages to design multi temperatures plane net belt quick-freezer, to improve the heat transfer temperature difference. The subject also includes energy analysis and experimental research of the quick-freezer. The main conclusions are as follows:1. For the rice dumping used in the experiments, with the initial temperature at 15℃and the terminal freezing temperature at -18℃, the pre-cooling load in frozen goods cold load ratio is 25.64%,Crystal period of load accounts for 65.10%, deep cold period of load accounts for 9.26%.2. In the environment of the pre-cooling temperature at -10℃, the cold wind speed at 4 m/s, deep cold temperature at -30℃, deep cold wind speed at 4 m/s, crystallization wind speed at 4.5 m/s, pre-cooling time is 500s or so (about 8 minutes), deep cold time is 200s or so (about 3 minutes), crystallization time changes from 1400s to 1100s (20 minutes up and down), with the crystallization temperature changing (-19℃,-22℃ and -25℃).3. When the crystallization wind speed is 3m/s, energy consumption of unit quality frozen goods is low, and reduces with the crystallization temperature rising, but crystallization time is long. When the crystallization wind speed is 4.5m/s and the crystallization temperature is at -22℃ or -25℃, crystallization time can be less than 20 min. When the crystallization wind speed is 4.5m/s and the crystallization temperature is at -22℃ or -19℃, energy consumption of unit quality frozen goods is low. When the crystallization wind speed is 6 m/s, although crystallization time is short, energy consumption of unit quality frozen goods is high because the high power consumption of fan.4. Using a single evaporation temperature -32℃, while the wind speed is 4m/s, energy consumption of unit quality rice dumping is calculated, and the valve is 137.4kJ/kg. In the multi temperatures environment of the pre-cooling temperature at -10℃, the cold wind speed at 4 m/s, deep cold temperature at-30℃, deep cold wind speed at 4 m/s, crystallization wind speed at 4.5 m/s, when the crystallization temperature is -19℃,-22℃and -25℃ respectively, energy consumption of unit quality rice dumping is 98.72 kJ/kg,101.12 kJ/kg,103.63 kJ/kg respectively. The calculation results show that the multi temperatures quick-freezer is energy saving than a quick-freezer only with a single evaporation temperature.