4. Air purgers .
The air penetrates into the refrigeration unit system on the low-pressure side when operating at boiling pressure lower than atmospheric one and during repair and maintenance works performance. The air builds up in a condenser and a steam part of linear receiver. The air entrained into the condenser leads to the following negative developments:
3.1. General industrial pumps.
Centrifugal overhung pumps are mainly used for circulation of water (for condenser cooling) and intermediate cooling medium. Domestic and foreign companies offer a wide range of such pumps with a flow rate from 5 to 400 m3/h and a head from 5 to 125 m. The external view of pumping assembly of the given type is presented in fig. 3.1. Continue reading
2.1 Bubbling oil separators.
Ammonia vapours in bubbling oil separators come from the compressor into the inner pipe, which outlet is 125…150 mm below the fluid level in the apparatus. When the refrigerant vapour passes through the liquid refrigerant layer, not only oil drops are gathered but oil vapour becomes condensed as well. Continue reading
1.1. Linear receivers.
Linear receivers are designed for collecting the liquid refrigerant received in the process of vapour condensation in a condenser, and for providing the required and stable liquid flow supplied to a regulating valve. Continue reading
In addition to main elements (a compressor and heat exchangers) the refrigeration unit scheme also includes the ancillary equipment: linear, protective, circulating and drain receivers, liquid separators, oil separators, refrigerant and cooling medium circulation pumps, air purgers and others.
Heat exchangers considerably identify RM weight-size and energy parameters. Heat exchangers weight amounts to 50-70% on average in a total weight of ammonia refrigerating machines (APMs) equipment.
The technical-and-economic indexes of refrigerating machine operation are substantially determined by compressor unit performance indexes.
A compressor unit comprises the following:
The choice of a refrigerating machine cycle particularly depends on the required temperature of the flow to be cooled (the temperature maintenance in a cooling chamber) and on the ambient temperature. A type of compressor and heat exchangers, a working substance and a plant scheme itself have a substantial influence on the cycle.
The ammonia (NH3) is the most advanced among natural substances, which are used as working media in refrigeration units, and known under designation R717. Below we shall consider positive and negative properties of the ammonia using as a refrigerant in comparison with freons.
A large variety of working substances, which can be used in refrigeration, as well as a variety of their thermodynamic and operational properties, shows that one substance having only positive qualities and properties is rather hard to find.