An Explicit Design Method for Heat Exchanger Based on Logarithmic Mean Temperature Difference (Lmtd) Method

This work presents a heat exchanger design method characterized by explicit temperature solution (ETS) for working medium. Such method is derived for both parallel-flow and counter-flow pattern based on the traditional LMTD method. As the temperature distribution is given in an explicit form related to the mixing temperature, the heat transfer performance of heat exchanger can be solved without iterations, improving the efficiency of heat exchanger design. A dimensionless expression is proposed for the ETS method. The defined dimensionless excess temperature is simply written as a function of a newly defined number of heat transfer units (NTU), which reveals the essential relation between heat transfer process and the mixing temperature. Considering the practical engineering application, the influence of variable physical property is discussed. The temperature distributions of the reference temperature method and the integral method (whole length) are compared with the accurate distribution of the adaptive-grid method (segmented). Results indicate that the temperature distribution obtained by the integral method highly coincides with the accurate one, showing a relative error of only 1.4 %. The proposed ETS method with integral physical property treatment is an efficient and accurate way for heat exchanger design