The main types of surface milk coolers were tested using water at 95°F. instead of milk The coolers were tested: (a) for cooling efficiency at the nominal rated flow and a range of cooling-water flows; (b) for allowable flow at 3:1 cooling-water and cooling to within 3° F. of the cooling-water; (c) for the allowable flow (lb./hr. per square foot of cooling surface) for a range of cooling-water flows; (d) for the cooling-water pressures for various rates of flow.

The results showed that no cooler reached the required efficiency at a cooling-water ratio of 3:1 or less, the temperature difference at the bottom of the cooler varying from 3·3 to 7° F. for normal coolers.

The allowable flow per square foot of cooling surface varied from 33·8 to 114 lb./hr. when cooling to 3° F. difference with 3:1 water. The corrugated plate design had higher allowable capacity at low rates of flow of cooling·water than the tubular designs. Atmospheric cooling was small.