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At present, in the field of large-scale central air-conditioning commonly used screw water-cooled chillers, with the gradual improvement of energy-saving requirements, the unit more and more use of flooded evaporator heat exchanger with high heat transfer coefficient. Since the flooded evaporator is boiling heat transfer outside the tube, its heat transfer performance is superior, which can effectively increase the evaporation temperature, reduce the heat transfer temperature difference, thereby improving the energy efficiency ratio of the unit. However, there are also some technical problems in the full-liquid unit, which makes the failure rate higher and the cost higher than the dry unit. The oil return of the full-liquid system is more difficult than that of the dry system, and the control of the unit is more complex, which makes some plants with weaker technical capabilities.
With the increasingly urgent demand for energy saving and low carbon, more and more heat exchange equipment with waste heat and waste heat recovery is widely used. Refrigeration and air-conditioning industry is the focus of energy-saving areas, refrigeration, air-conditioning equipment for the condensation heat heat recovery for the preparation of domestic hot water or process hot water, is currently widely used as an energy-saving way. Large refrigeration and air-conditioning hosts often use shell and tube heat exchangers as their condensers. This form of refrigeration host needs to design and transform the condenser when heat recovery of condensation heat. Generally, there are two heat recovery methods: partial heat recovery and total heat recovery. Partial heat recovery is to recover only one.
1. Working principle and structure of dry, flooded and falling film evaporators: 1.1 and dry evaporators The refrigerant of the dry evaporator passes through the heat exchange tube, and the cold water runs outside the high-efficiency heat exchange tube. The heat exchange efficiency of the heat exchanger is relatively low, and its heat exchange coefficient is only about 2 times that of the light tube, but its advantages are easy to return oil and easy to control, the refrigerant charge is about 1/2-1/3 of the full liquid unit charge. 1.2. Filled-liquid evaporator The operation mode of the flooded evaporator and the dry evaporator is just the opposite. The cold water passes in the heat exchange tube, and the refrigerant is completely
1. Calculation Method of Heat Exchange Area of Air Condenser Cooling Capacity Compressor Motor Power/200~250 = Condenser Heat Exchange Surface e.g. (3SS1-1500 Compressor) CT = 40 ℃:CE =-25 ℃ Compressor Refrigeration Capacity = 12527W Compressor Motor Power 11250W = 23777/230 = Air Condenser Heat Exchange Area 103 m2 2, Water Condenser Heat Exchange Area to Air Condenser Ratio = Estimated 1: 18(103/18)= 6m2 Evaporator Area According to Compressor Refrigeration Capacity (Evaporation Temperature ℃×Δt Relative Humidity Recuperation Coefficient Look-up Table).
1, cold storage evaporator surface frosting is too thick, too much dust, so that the heat transfer effect decreased caused by cold storage temperature drops slowly an important reason is the evaporator heat transfer efficiency is low, this is mainly due to the evaporator surface frost layer is too thick or caused by too much dust. Because the surface temperature of the evaporator of the cold storage is mostly lower than 0 ℃, and the humidity of the warehouse is relatively high, the moisture in the air is easy to frost on the surface of the evaporator and cause icing, which affects the heat transfer effect of the evaporator. In order to prevent the surface frost layer of the evaporator from being too thick, it is necessary to defrost the surface of the evaporator regularly. Introduce two simple defrosting methods: ① stop defrosting. That is, stop the compressor and open the library.
The most widely used refrigerant in the domestic refrigeration industry is still R22. However, due to its destruction of the ozone layer and high greenhouse effect, China has determined that its use will be eliminated before 2030 according to the relevant international agreement. Therefore, more and more refrigerated refrigeration equipment is using R22's replacement R404a, although R404A and R22 have similar refrigeration performance, but in actual use, there are still many differences between the two to be noted. Refrigerant R404a instead of R22 need to consider the following issues. 1. The biggest problem of using R404A instead of R22 is lubricating oil, which must be matched
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