Refrigeration Manual - HVAC and Refrigeration Information Links

Figure No.20 shows parallel circuits in both water cooled condenser and the motor-compressor water jacket. Each water jacketcircuit is connected in series with one circuit of the split condenser. This type of water circuiting is used when a minimum ofwater pressure drop is required.In order to maintain water velocities at an acceptablelevel, parallel circuiting of the condenser may benecessary when high water flow is required.2. If a water circulating pump is used, install so that thecondenser is fed from the discharge side of the pump. Ifthe pump were on the discharge side of the condenser,the condenser would have a slight vacuum in the watersystem, and therefore the water would be much nearerits boiling point. A combination of a localized hot spot inthe condenser together with a localized velocity increasethat might reduce pressures even lower, could result intriggering a cavitation condition.Cavitation is basically a condition where a fluctuatingcombination of pressure and temperature can causeinstantaneous boiling or flashing of water into vapor, withthe subsequent collapse of the bubbles as the conditionsvary. This can result in very rapid erosion and destructionof the water tube. Maintaining a positive pressure in thecondenser will prevent this condition.3. If the condenser is installed more than 5 feet higherthan the outlet drain point of the condenser, a vacuumbreaker or open vent line should be provided to preventthe discharge line from creating a partial vacuumcondition in the condenser water system. An unventeddischarge connection with a high vertical drop couldresult in cavitation in a manner similar to a pump onthe outlet of the condenser.EVAPORATIVE CONDENSERSEvaporative condensers are frequently used wherelower condensing temperatures are desired than areobtainable with air cooled condensers, and where theavailable water supply may not be adequate for heavywater usage. The hot refrigerant vapor is piped througha spray chamber where it is cooled by evaporation of thewater coming in contact with the refrigerant tubing.Water which is exposed to air flow in a spray chamberwill evaporate rapidly. Latent heat required for theevaporating process is obtained by a reduction in sensibleheat and, therefore, a reduction in the temperature ofthe water remaining. An evaporative spray chambercan reduce the water temperature to a point closelyapproaching the wet bulb temperature of the air.Wet bulb temperature is a term used in air conditioning todescribe the lowest temperature that can be obtained bythe evaporating process. The term wet bulb temperatureis derived from the fact that a common mercury bulbthermometer exposed to the ambient air5-4© 1967 Emerson Climate Technologies, Inc.All rights reserved.