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Heat Exchangers The rate of heat transfer in a heat exchanger is Q Uo = AFDT lm, where A = any convenient reference area (m2) F = heat exchanger configuration correction factor (F = 1 if temperature change of one fluid is negligible) U = overall heat transfer coefficient based on area A and the log mean temperature difference [W/(m2·K)] ?T
environment temperature which is assumed fixed The convective heat transfer coefficient, )?=?( ,???? In reality, electrical resistance varies with temperature and is expressed as: = 0[1+ (???? 0)] (11) and t he heat balance from eqn (6 ) becomes: 2 [1+ (???? 0)]=2 [????????(???? 4 4)+ ??( ,???? )(???? )] (12) We note that the heat
insulated tip case by a corrected length defined as Corrected fin length L c is defined such that heat transfer from a fin of length L c with insulated tip is equal to heat transfer from the actual fin of length L with convection at the fin tip t the thickness of the rectangular fins D the diameter of the cylindrical fins
higher heat transfer coefficient The distance between two baffles is baffle spacing Multiple Passes Shell-and-tube heat exchangers can have multiple passes, such as 1-1, 1-2, 1-4, 1-6, and 1-8 exchangers, where the first number denotes the number of the shells and the second number denotes the number of passes