Approximate formulas of number of transfer unit of U shaped fintube heat exchangers

Abstract:

To obtain the formulas of number of transfer unit (NTU) of U shaped fintube heat exchangers, a U shaped fintube heat exchanger is taked as research object. Approximate NTU formulas of number of transfer unit are derived by establishing heat transfer model of U shaped fintube when the trend of two flows in fintube heat exchanger is counter and parallel, respectively. Subsequently, the heat transfer coefficients of fintube are compared and analyzed by effectivenessnumber of transfer unit method (εNTU method) and logarithm mean temperature difference method (LMTD method) when inlet water temperature is from 45 ℃ to 60 ℃ and water flow rate is from 30 kg／h to 110 kg／h. The results show that, the difference of the heat transfer coefficients respectively calculated by εNTU method and LMTD method is so small that these NTU formulas are valid