Finite element analysis for co-current and counter-current parallel flow three-fluid heat exchanger

Purpose To study the thermal performance of both co-current and counter-current parallel flow heat exchangers. The hot stream is assumed to flow in the middle of two cold streams and exchange heat with them. Design/methodology/approach The dimensionless governing equations are derived based on the conservation of energy principle and solved using FEM based on subdomain collocation method and Galerkin's method. The results show that the subdomain collocation method is more accurate than the Galerkin's method, as observed when the results obtained are compared with the analytical results for the classical two-fluid heat exchangers. Findings The results are presented in terms of effectiveness and number of transfer units (Ntu) for different values of the governing parameters. The governing parameters are the Ntu, the heat capacity ratios, the overall heat transfer coefficient ratio, and the inlet temperatures parameter. The results show that the effectiveness of the three-fluid heat exchanger is always higher than that of classical two-fluid flow heat exchanger for fixed values of the governing parameters. The results also show that for fixed values of the governing parameters, the effectiveness of the counter-current is higher than the co-current parallel flow three-fluid heat exchangers. Research limitations/implications One-dimensional governing equations are derived based on the conservation of energy principle. The ranges of the governing parameters are: Ntu (0:5), the heat capacity ratios (0:1,000), the overall heat transfer coefficient ratio (0:2), and the inlet temperatures parameter (0:1). Practical implications Both co-current and counter-current parallel flow heat exchangers are used in the thermal engineering applications. The design and performance analysis of these heat exchangers are of practical importance. Originality/value This paper provides the details of the performance analysis of co-current and counter-current parallel flow heat exchangers, which can be used in thermal design.