14. Energy Balance for a Swimming Pool

Swimming pools use solar collectors or natural gas heaters to maintain comfortable temperatures that are desired, i.e. between 20 C to 30 C. UV stabilized transparent plastic or bubble type covers are used during night to minimize losses due to evaporation heat transfer and convection heat transfer from pool water’s surface. Since water in a pool has a very large thermal mass, water’s temperature changes slowly. Therefore in the present analysis, steady-state heat transfer conditions will be analyzed. Also monthly averaged solar radiation absorbed by water, relative humidity of air, latent heat of evaporation and diffusion coefficient of water in air will be used. Conduction heat transfer from pool walls to earth will be neglected, since this mode of heat transfer is less than 2% as compared to major heat transfer mechanisms, such as incident solar radiation, evaporation from surface of pool water, convection losses from surface of pool water and infrared radiation losses from surface of pool water. With above assumptions, net heat loss from surface of pool water in a month can be estimated using Equation 14-1.