General principles for the design and layout of walk-in cooler refrigeration systems (2)

5. Determination of cooling system cooling modes Decentralized cooling. The centralized system means that all the refrigeration equipment except the evaporator is installed in a central computer room. The cooling capacity of all cold rooms is uniformly supplied by the central computer room: while the decentralized system is equipped with a separate cold room for each cold room. Sets of refrigeration system, there are several sets of independent refrigeration systems corresponding to several cold rooms. The advantages of the centralized system are: the refrigeration capacity of the refrigerator can be less than the total cooling room load, and the refrigeration compressors can be adjusted to each other, saving equipment investment and operating costs; easy to manage, especially for manual operating systems. The disadvantage is that it increases the construction cost of the central computer room, and the refrigeration pipeline system is more complicated and the pipeline is longer. Distributed refrigeration generally uses a condensing compressor unit, and the unit and the air cooler are installed on a partition wall, so the pipeline is short and the installation is simple, which can save the civil construction investment of the central computer room. The disadvantage is: single room single set single supply. Therefore, the output and total output of a single refrigeration unit are much larger than that of a centralized refrigeration unit, which increases investment and energy consumption: once a unit fails, the refrigeration units cannot be adjusted to each other. The corresponding cold room cannot be cooled, so the walk-in cooler system has poor flexibility. Therefore, decentralized cooling is generally used for small walk-in coolers or walk-in coolers with a small number of cold rooms. It often uses a fluorine machine with a high degree of automation and a simple system, while large and medium-sized walk-in coolers generally use a centralized refrigeration system. Regardless of whether the centralized refrigeration system uses single-stage compression or two-stage compression, it is basically composed of main circuits such as compression circuit, condensing circuit, liquid supply circuit, evaporation (cooling) circuit, and cooling water circuit (air cooling does not exist), flushing The frost circuit and the auxiliary circuit of the ammonia system such as oil and air discharge are formed. Two-stage compression also needs to add an intermediate cooling circuit.

6. Determination of cold room cooling methods The available cold room cooling methods include: direct cooling and indirect cooling. Direct cooling refers to the use of refrigerant evaporation to directly cool the object to be cooled. Freezing processing and refrigeration generally use this method; and indirect cooling refers to the transfer of heat from the object to be cooled to the refrigerant through an intermediate medium. Classic example.

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