ε-NTU relationships in parallel-series arrangements: Application to plate and tubular heat exchangers

Abstract

The ε-NTU method has advantages over other methods because it does not require assumption of an outlet temperature to determine the duty of a heat exchanger. In this work, the ε-NTU method was used to obtain a general algebraic expression of the effectiveness of PHEs in the N-Pa pass-1 pass configuration as a function of the heat capacity ratio (C*) and the number of transfer units (NTU). This expression is valid for PHEs with a high number of plates (N-p > 40). In addition, 1 pass-1 pass and 2 pass-1 pass PHEs were numerically analyzed to obtain an algebraic expression of the effectiveness of PHEs with a low number of thermal plates (N-P < 40) as a function of C*, NTU and the number of plates. Finally, the expression obtained for N-pa pass-1 pass PHEs with a high number of plates was generalized for use in any heat exchanger with series-parallel configurations, such as series-parallel arrangements of double-pipe or shell-and-tube heat exchangers.