Some special requirements for the refrigeration process of the quick-freezing device In order to adapt to the characteristics of the quick-freezing of the quick-freezing device, the following requirements should be paid attention to during the design and installation of the refrigeration process:
(l) Pay attention to the pre-cooling section before quick freezing, and the food should be fully cooled before entering the quick-freezing machine. Full pre-cooling is an important part of the quick-freezing machine's hourly production capacity to meet design requirements. The area of ​​the evaporator should be matched with the area of ​​the evaporator in the cooling tank. The water flow of the evaporator in the pre-cooling tank is not large. The empirical value of the heat exchange load per unit area is calculated according to the heat exchange rate of 2 (XX) watts per square. The refrigeration system should be a self-contained system that cannot be connected in series with the refrigeration or freezing system to prevent the cold water tank heat load from impacting the low temperature system.
(2) When selecting the refrigeration unit and the condenser, it is not allowed to see only the evaporation temperature of the quick freezing device below 40 °C. The Chinese food cold-cut chain conference praised the cold wear chain supporting equipment exhibition, the public opinion rate was greatly reduced, and the condenser was selected too small, resulting in long-term negative pressure during the production season, the system attracted air. High pressure is extraordinary. There should be some room for the condenser to be compatible with the heavy load during the initial operation of the quick-freezer.
(3) A 45 °C evaporative refrigeration system of the quick-freezing device should be set up separately, and should not be combined with the quick-freezing and cold storage refrigeration lines. Since the evaporation temperature between the quick freezing is at 3 ° C, the refrigeration is a 28 ° C. It has a large distance from the evaporation temperature and pressure of the quick freezing device. After freezing in the quick freezing zone, the evaporation pressure can be as high as 0.2 to 0 in the initial stage of cooling. SMpa, a large amount of high-pressure gas in the quick freezing room will seriously flush the normal negative pressure refrigeration system of the quick-freezing device, causing the temperature of the quick-freezing device to rise rapidly and the output is greatly reduced.
(4) Preventing the freezing operation of the refrigeration system of the quick-freezing device The liquid pump cavitation is prone to occur: The following measures should be taken:
A. Increase the liquid level head between the normal liquid level in the circulating barrel and the pump center line. It is recommended that the platform height of the barrel be increased from 2. 2 meters to 2. 4 meters in the general cold storage to about 2. 8 meters. Be sure to ensure the normal liquid level in the barrel, do not work for a long time and low liquid level. Vertical circulation drums should be installed, and horizontal drum pumps should not be installed.
B. To do the thermal insulation project of the circulating barrel and the pump liquid supply pipeline, the thickness must be above the cm cm, pay special attention to the pump suction and heat preservation to prevent the liquid from evaporating in the tube to generate gas.
C. Pumping the human tube should enlarge the diameter of the pipe as much as possible, and the diameter should be rounded in the vicinity of the population to reduce the flow resistance. Select the mesh of the ammonia pump filter and do the cleaning work regularly.
D. Try to use the shield liquid pump. Because the open gear ammonia pump works under negative pressure, the shaft seal is easy to attract air. Attention should be paid to increasing the flow rate and head when selecting the type.
E. Install the exhaust pipe at the pump inlet end. If the cavitation phenomenon occurs during the empty pump operation, remove the gas in the pump in time. In addition, attention should be paid to installing a differential pressure relay at the inlet and outlet of the pump. When the pump does not get liquid, it can alarm and stop the pump in time.
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