Used on commercial and larger systems, water-cooled condensers are classified as double-pipe, flooded atmospheric; bleeder shelland-tube, and shell-and-coil. In condensers of this type, the amount and temperature of the water determine the condensing temperature and pressure, and (indirectly) the power required for compression. In locations where water must be conserved or where water is restricted, it is usually necessary to install cooling towers or evaporative condensers. When adequate low-cost condensing water is available, water-cooled condensers are often desirable because of the lower condensing pressures and better head-pressure control.
Water (particularly from underground sources) may be much colder than daytime temperatures. If evaporative cooling towers are used, the condensing water can be cooled to a point closely approaching the ambient wet-bulb temperature, which allows the continuous recirculation of condensing water and reduces water consumption to a minimum. A water-cooled condensing unit is shown in Figure 8-3.
A pressure- or temperature-sensitive modulating water-control valve (such as shown in Figure 8-4) can be used to maintain condensing pressures within the desired range by increasing or decreasing the rate of water flow as necessary.