A cooling pond may be a good choice if ample room for such a pond is available
and land costs are low at a given location. The slow process most often requires a
very large pond surface, perhaps several acres, for proper heat transfer to occur.
Also, if they are located in a rural area and if the quality of the water being cooled is
fairly good, such man-made ponds can offer recreational uses in addition to serving
to lower the water temperature. An important note regarding cooling ponds is that
this method of lowering the water temperature is most likely to limit evaporative
losses of water vs. a cooling tower.
However, if the needed land area for a pond is not available and/or the slow
cooling of the water is unacceptable, a cooling tower will be the design choice.
Cooling towers are classified as natural or mechanical draft, as well as wet or dry
types.
2 Cool Ponds
2.1 Mechanism of Heat Dissipation (Cooling)
A cooling pond permits a sufficient buildup of the process water so that the needed
heat exchange may occur between the water and the surrounding environment. The
warmed water entering the pond will lose and gain heat as it passes through the pond
by the combined mechanisms of conduction, convection, radiation, and evaporation.
Numerous factors affect the rates of these various mechanisms as well as the overall
rate of heat transfer. If the heat inputs are equal to heat outputs, the pond will be at an
equilibrium condition, and the surface temperature of the pond will be at some
constant value.
The heat exchange between the pond and the surrounding environment will be
governed by the temperature difference between the atmosphere and the pond
surface, the surface area of the pond, meteorological conditions such as rain or
sun, wind speed, humidity, geographical location, and so forth. Obviously these
conditions will vary depending upon both time of day as well as time of year.
The various heat inputs and outputs have been identified and presented in typical
ranges [1]. Expressed in both Kcal/day-m
2 and Btu/day-ft
2 , these values are as
follows.
Inputs
1. q s ¼ short-wave solar radiation
Range of q s from 1085–7588 Kcal/day-m
2 or 400–2800 Btu/day-ft
2
2. q a ¼ long-wave solar radiation
Range of q a from 6504–8672 Kcal/day-m
2 or 2400–3200 Btu/day-ft
2
5 Cooling and Reuse of Thermal Discharges
199
and land costs are low at a given location. The slow process most often requires a
very large pond surface, perhaps several acres, for proper heat transfer to occur.
Also, if they are located in a rural area and if the quality of the water being cooled is
fairly good, such man-made ponds can offer recreational uses in addition to serving
to lower the water temperature. An important note regarding cooling ponds is that
this method of lowering the water temperature is most likely to limit evaporative
losses of water vs. a cooling tower.
However, if the needed land area for a pond is not available and/or the slow
cooling of the water is unacceptable, a cooling tower will be the design choice.
Cooling towers are classified as natural or mechanical draft, as well as wet or dry
types.
2 Cool Ponds
2.1 Mechanism of Heat Dissipation (Cooling)
A cooling pond permits a sufficient buildup of the process water so that the needed
heat exchange may occur between the water and the surrounding environment. The
warmed water entering the pond will lose and gain heat as it passes through the pond
by the combined mechanisms of conduction, convection, radiation, and evaporation.
Numerous factors affect the rates of these various mechanisms as well as the overall
rate of heat transfer. If the heat inputs are equal to heat outputs, the pond will be at an
equilibrium condition, and the surface temperature of the pond will be at some
constant value.
The heat exchange between the pond and the surrounding environment will be
governed by the temperature difference between the atmosphere and the pond
surface, the surface area of the pond, meteorological conditions such as rain or
sun, wind speed, humidity, geographical location, and so forth. Obviously these
conditions will vary depending upon both time of day as well as time of year.
The various heat inputs and outputs have been identified and presented in typical
ranges [1]. Expressed in both Kcal/day-m
2 and Btu/day-ft
2 , these values are as
follows.
Inputs
1. q s ¼ short-wave solar radiation
Range of q s from 1085–7588 Kcal/day-m
2 or 400–2800 Btu/day-ft
2
2. q a ¼ long-wave solar radiation
Range of q a from 6504–8672 Kcal/day-m
2 or 2400–3200 Btu/day-ft
2
5 Cooling and Reuse of Thermal Discharges
199