where is the length of heating period. This equation may also be used when the tank contents have cooled from tf to to and must be reheated to tf. If the contents cool during a time 8c, the temperature at the end of this cooling period is obtained from

Heating with External Coil from Initial Temperature for Specified Time The temperature of the dead-air space is obtained from

VdA^td - 0.5(tf - to)] = U2A2[0.5(tf - to) -1] + Q/8 h (11-43) The heat load is q = U,A1(td -1') + U2A2[0.5(tf - to) -1'] + Q/8h (11-44) The coil area is obtained from Eq. 11-39.

The safety factor used in the calculations is a matter of judgment based on confidence in the design. A value of 1.10 is normally not considered excessive. Typical design parameters are shown in Tables 11-1 and 11-2.

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