164 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1939 



(^ /^o 



r 



{ 



-^ so 



^ SO 



O S /O /S ^0 2S so 3S 40 



FiQUKE 3. — Temperature of hot water drawn at 4 : 00 p. m. from simple uncovered 30- 

 gallon tank in July ; temperature readings were taken of each gallon as drawn. 



Enclosed rmdtiple-tank solofr water heater. — An improvement of 

 the exposed tank heater is seen in plate 2, figure 2. From several 

 tanks enclosed in an insulated, glass-covered box, a large supply of 

 water above 120° F. can be obtained in the afternoon. This system 

 might be used for general domestic hot water if the clothes could be 

 washed in the late afternoon when the water is hottest. During the 

 night the water cools off so rapidly that morning temperatures are too 

 low for clothes washing, though it yet might serve for all the other 

 needs. The sunshine falling in the box space between the tanks and 

 on each side indirectly furnishes extra heat for the tanks by convection 

 of hot air. Although the daytime thermal efficiency of the glass- 

 covered tank heaters is high, the large losses at night make the 24-hour 

 efficiency less than for pipe absorbers with insulated storage tanks. 



Temperatures over 130° F. are obtainable in the late afternoon, but 

 the morning temperature cannot be expected to exceed 110°, which is 

 too cold for washing clothes. This system (pi. 3, fig. 2) has, however, 

 the advantage of simplicity, high daytime efficiency, and self-storage, 

 and is nonfreezing in most of the agricultural areas of California. 



