The three main types of condensers used in general refrigeration systems are:
All of these serve the industrial refrigeration field as well. In comparison to the air-conditioning industry, however, a lower percentage of air-cooled condensers and a higher percentage of evaporative condensers are operating in industrial refrigeration plants. In industrial refrigeration practice, it is common to connect the evaporative condensers in parallel—a concept not normally used in air conditioning.
The three types of condensers are shown schematically in Fig. 7.1a, 7.1b, and 7.1c. The air-cooled condenser in Fig. 7.1a condenses refrigerant vapor by rejecting heat to ambient air blown over the finned condenser coil with the aid of a fan, usually a propeller type.
Most all water-cooled condensers (Fig. 7.1b) condense refrigerant in the shell and on the outside of tubes through which water passes. The condenser cooling water picks up heat in passing through the condenser and this warm water is cooled by circulating through a cooling tower (Section 7.6). While the shell-and-tube construction predominates for water-cooled condensers, plate-type condensers, sister of the plate-type evaporator explained in Sec. 6.31, are now appearing. The evaporative condenser of Fig. 7.1c might be considered a cooling tower, with the condenser tubes washed by the water spray. Ultimately, the heat rejected from the refrigeration plant is discharged to ambient air, except where the condenser is cooled by water from a well, lake, or stream.
This chapter first explores the condensing process outside and inside tubes. Next, the overall performance of water-cooled condensers and the translation of performance to noncatalog ratings is examined. An explanation of the performance of cooling towers, the constant companions of water-cooled condensers, is given. Because of their prevalence in industrial refrigeration plants, the emphasis of this chapter is on the performance, selection, application, and operation of evaporative condensers.