Water is used to cool condensers. One method is to cool condensers with water from the city water supply and then exhaust the water into the sewer after it has been used to cool the refrigerant. This method can be expensive and, in some instances, is not allowed by law. When there is a sewer problem, a limited sewer-treatment plant capacity, or drought, it is impractical to use this cooling method.
The use of recirculation to cool the water for reuse is more practical. However, in recirculation, the power required to pump the water to the cooling location is part of the expense of operating the unit.
There are three types of water-cooled condensers:
The double-tube type consists of two tubes, one inside the other (see Fig. 8-5). Water is piped through the inner tube. Refrigerant is piped through the tube that encloses the inner tube. The refrigerant flows in the opposite direction than the water (see Fig. 8-6).
This type of coaxial water-cooled condenser is designed for use with refrigeration and air-conditioning condensing units where space is limited. These condensers can be mounted vertically, horizontally, or at any angle.
They can be used with cooling towers also. They perform at peak heat of rejection with water pressure drop of not more than 5 psi, utilizing flow rates of 3 gallons per minute per ton.
The typical counterflow path shows the refrigerant going in a 105°F (41°C) and the water going in at 85°F (30°C) and leaving at 95°F (35°C) (see Fig. 8-7).
The counter-swirl design, shown in Fig. 8-6, gives a heat-transfer performance of superior quality.
The tube construction provides for excellent mechanical stability. The water-flow path is turbulent. This provides a scrubbing action that maintains cleaner surfaces. The construction method shown also has very high system pressure resistance.
The water-cooled condenser shown in Fig. 8-5 can be obtained in a number of combinations. Some of these combinations are listed in Table 8-1. Copper tubing is suggested for use with fresh water and with cooling towers. The use of cupronickel is suggested when salt water is used for cooling purposes.
Convolutions to the water tube result in a spinning, swirling water flow that inhibits the accumulation of deposits on the inside of the tube. This contributes to the antifouling characteristics in this type of condenser. Figure 8-8 shows the various types of construction for the condenser.
This type of condenser may be added as a booster to standard aircooled units. Figure 8-9 shows some of the variations in the configuration of this type of condenser:
Note the inputs for water and refrigerant. Using a cooling tower to furnish the water that contacts the outside tube can further cool the condenser. Also, a water tower can be used to cool the water sent through the inside tube for cooling purposes. This type of condenser is usable where refrigeration or air-conditioning requirements are 1/3 ton to 3 ton.
Placing a bare tube or a finned tube inside a steel shell makes the shelland-coil condenser (see Fig. 8-10). Water circulates through the coils. Refrigerant vapor is injected into the shell. The hot vapor contacts the cooler tubes and condenses. The condensed vapor drains from the coils and drops to the bottom of the tank or shell. From there it is recirculated through the refrigerated area by way of the evaporator. In most cases, placing chemicals into the water cleans the unit. The chemicals have a tendency to remove the deposits that build up on the tubing walls.