The Oriented Spray Cooling System for Supplementing Cooling Lakes

Abstract

With ever-increasing ambient temperatures many electric power plants that employ cooling lakes to reject their waste heat into the environment are struggling to maintain reasonable turbine backpressures during the hot summer months when electric load demand is often the greatest. Some consider adding mechanical draft cooling towers (MDCT) to further cool the condenser circulating water (CCW) prior to entering the main condenser, but the additional auxiliary power required to drive MDCT fans often consume the additional generator output resulting from the lower backpressure. Spray ponds offer significant advantages over MDCT including superior simplicity and operability, lower power requirements, and lower capital and maintenance costs. The Oriented Spray Cooling System (OSCS) is an evolutionary spray pond design. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and spray upward, blocking the ambient air flow to the spray region as it travels down to the pond below, the OSCS nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, the water droplets drag air into the spray region while the warm air concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. During the late 1970’s the author developed a purely analytical model to predict the thermal performance of the OSCS which was successfully compared with the OSCS at the Columbia Generating Station (CGS) in the mid 1980’s. This paper describes how the OSCS may be employed to supplement the cooling capacity of an existing cooling lake to reduce the temperature of the CCW prior to entering a power plant, resulting in lower main condenser pressures and more net plant output.