An experimental and numerical investigation to enhance heat transfer in porous heat exchangers for waste heat recovery system

The energy from an IC engine's exhaust gas can be used to operate a vapour absorption refrigeration system, which cools the interior of the vehicle. An exhaust gas-powered porous heat exchanger can be used in place of a generator in vapour absorption refrigeration systems. In this study, a double pipe counter flow heat exchanger with and without porous materials (wire screens) is analyzed numerically to maximise heat transfer from hot air to cold fluid with a minimum of pressure drop using the Ansys Fluent tool. Wire screens are used in this heat exchanger due to their higher surface area density. In order to assess their effects on the heat exchanger's effectiveness, the number transfer unit, and the pressure drop under steady-state conditions, tests are conducted. The impacts of the wire screens presence are investigated for both water and aqua ammonia as cold fluids, as well as for varying hot air mass flow rates. Furthermore, the numerical estimations of heat transfer from hot air to cold water are validated by experimental data. Compared to a heat exchanger without porous material, the effectiveness of a porous heat exchanger increases from 0.17 to 0.33. The numerical investigation outcomes and the experimental validation are quite comparable.