Thanks breizh for the nomograph of heat loss from tanks (insulated or not) to ambient air.
1. In the example of 17000 gallon tank, total heat transfer coefficient (no insulation) is 250 kW / (1025 ft2 ×220 oF) = 18.5 kcal/(hm2oC) for still air. This is higher (that is more conservative) compared to previous posts, probably incorporating some safety factor.
2. Wind increases heat losses by a factor up to 3.3, for velocities up to 56 km/h, also depending on surface temperature (the latter considered for the case of still air). Actually wind substantially lowers surface temperature, which may explain why mentioned factor gets so low (even lower than wind velocity =0) at strong wind combined with high surface temperatures: temperature difference (between surface and ambient) is much smaller now compared to still air.
Other interpretation welcomed.
Edited by kkala, 20 January 2013 - 03:26 PM.