Comparison of direct expansion and indirect schemes in cold storage refrigeration system

In the cold storage (especially 0 degrees above the high temperature storage) refrigeration system, usually there are two kinds of programs can achieve the temperature of the cold storage requirements. A is the refrigerant directly transported into the refrigerator refrigerant cooling fan, through direct expansion to cold storage cooling direct expansion refrigeration system; another is the unit adopts the low temperature first preparing - 5 degrees of low temperature glycol solution, and then through the pump delivery into the refrigerator of ethylene glycol cooler to reduce the temperature of the cold storage of indirect refrigeration system. These two systems can meet the requirements of the cold storage temperature, but what are the advantages and disadvantages between the two programs? This article from the following eight main aspects to illustrate:

First, the system configuration

Direct expansion refrigeration system: the use of condensing units + refrigerant cooler + refrigerant pipeline

Ethylene glycol indirect refrigeration system: low temperature ethylene glycol unit + ethylene glycol cold air fan + circulation pump + ethylene glycol pipeline

Two, the factory commissioning and testing

Direct expansion refrigeration system: condensing unit is not a complete refrigeration system, it is not easy to debug and test in the project, so it can only be debugged and detected in the field.

Ethylene glycol indirect refrigeration system: low temperature ethylene glycol unit is a complete refrigeration system, with ex factory commissioning and testing conditions, 100 percent factory commissioning and testing.

Three, the flow of media in the pipeline

Direct expansion refrigeration system: fluid in the pipeline as refrigerant, pipeline pressure requirements 2.5MPA.

Ethylene glycol indirect refrigeration system: fluid in the pipeline for ethylene glycol solution, pipeline pressure requirements 1.0MPA.

Four, the cold wind machine in addition to frost

Direct expansion refrigeration system: electric heating in addition to frost or water in addition to cream. Refrigerant evaporation temperature is low, the amount and the number of frost is more, the amount of dry product. Depletion of energy.

Ethylene glycol indirect refrigeration system: air de cream in the library. The average temperature of ethylene glycol is high, the amount and frequency of the cream is small, and the amount of the product is small. Do not consume defrosting power, but the use of the cold energy in cold storage temperature maintaining cream.

Five, operating expenses

Direct expansion refrigeration system: low refrigeration electricity, frequent start of high electricity, high cost of removal. Comprehensive operating cost is high.

Ethylene glycol indirect refrigeration system: high refrigeration and electricity, frequent start of electricity, in addition to the cost of 0. Comprehensive operating cost low.

Six, government regulation

Direct expansion refrigeration system: government regulation

Ethylene glycol indirect refrigeration system: the need to government departments for the record

Seven, other aspects

Direct expansion refrigeration system: high construction requirements, high return oil, low reliability, short life, high maintenance cost, high maintenance cost.

Ethylene glycol indirect refrigeration system: construction requirements are low, easy to return oil, high reliability. Long service life, simple maintenance and low maintenance cost.

Eight, cost

The direct expansion refrigeration system is slightly lower than the indirect refrigeration system of ethylene glycol.

To sum up, in the high temperature library, using ethylene glycol indirect refrigeration system is a good scheme. The greater the project, the more the number of cold storage, the more obvious advantages of ethylene glycol indirect refrigeration system. The smaller the item, the less the number of cold storage, the more dominant direct expansion system.

Special note:

In many colleagues believe that the system of ethylene glycol refrigeration unit evaporation temperature than the direct expansion of the refrigeration system, and the ethylene glycol system as there is a circulating pump, ethylene glycol system, how can the direct expansion of the system energy? We need to note here is that we calculate the operating costs are calculated in accordance with the rectification project, running costs include three aspects of the cost of cooling and frequent start-up costs + in addition to the cost of frost. There is no doubt that the first direct expansion of the refrigeration costs low, but the second frequent start-up costs and third in addition to the cost of frost, a direct expansion of the system is high, and a lot higher, resulting in higher overall operating costs. The above analysis results have been verified in a number of projects.

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