Amirkabir Journal of Mechanical Engineering

Amirkabir Journal of Mechanical Engineering

Using Bidirectional Flow to Improve Thermal Efficiency of Plate Heat Exchangers Containing Phase Change Materials

Document Type : Research Article

Authors
Mostafa Rahimi
Pouriya Salimi
Mechanical Engineering Department, University of Mohaghegh Ardabili, Ardabil, Iran
10.22060/mej.2025.24683.7896
Abstract
Thermal efficiency of a flat heat exchanger containing phase change material (PCM) was investigated numerically at the present study with the aim of improving its performance. A new idea was proposed based on which air flow through the passages embedded between the chambers containing PCM, modified as reciprocating or bidirectional flow. Three different values of 0.5, 1 and 1.5 m were assumed for the heat exchanger length, and each case was investigated in two flow modes, one-directional usual flow and bidirectional proposed flow mode. Three Reynolds numbers of 5000, 10000 and 15000 were examined based on the average air flow velocity and the hydraulic diameter of the air passage. For Re = 10000 by conducting a transient numerical analysis using Fluent software, it was found that the heat transfer rate to the air flow decreases sharply from 280 W at the beginning of the freezing process to less than 80 W at the final stages. Heat transfer drop was improved when using the bidirectional flow concept for all examined exchanger lengths and Reynolds numbers. As a result, the time required for complete solidification was reduced by about 14, 19 and 22% for three exchanger lengths, respectively. According to these results, the positive effect of bidirectional flow on the efficiency of the exchanger was greater for lower air velocities and larger lengths of the heat exchanger.
Keywords
Phase Change Materials
Heat/Cold Storage
Air Heat Exchanger
Bidirectional Flow
Convective Heat Transfer
Subjects
 
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Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 7
October 2025
Pages 921-938