This study proposes a novel multi-porous heat exchanger (MPHEX) as a passive, sustainable alternative to variable refrigerant flow (VRF) air conditioning systems, addressing the growing environmental burden of cooling demand. Through high-fidelity Lattice Boltzmann Method simulations of coupled heat and fluid transport, the MPHEX design is optimized to minimize exergy destruction. A case study for Tunisian conditions demonstrates that permeability optimization, when combined with solar-assisted preheating, reduces total exergy destruction by over 60% and increases the coefficient of performance (COP) by up to 20%, all while eliminating active mechanical regulation. The numerical results confirm strong experimental feasibility, positioning the MPHEX as a scalable, low-energy, and low-maintenance cooling solution for sun-rich regions.

The goal of this work is to provide an overview of the thermal and dynamic behaviors of a solar heat exchanger filled with two porous mediums, DPHEX, aimed at improving efficiency of solar air-conditioner. The flow within the porous region is modeled by Brinkman-Forchheimer-extended Darcy model. The mathematical model of energy transport is based on the local thermal equilibrium assumption. Simulations are achieved via a single relaxation time thermal Lattice Boltzmann Method (LBM) using two distribution functions to handle the fluid velocity and temperature. The obtained numerical results show that using two porous mediums improve the flow velocity and lead to better heat transfer and increase system’s Coefficient of Performance (COP) by up to 20% compared to conventional systems. Furthermore, the integration of solar energy reduces the compressor workload, resulting in up to 33% less refrigerant use anda20–33% reduction in CO₂ emissions, highlighting the system’s potential as a sustainable and environmentally friendly alternative to traditional cooling technologies.This dual-layered exchanger architecture offers a promising path toward next-generation, low-carbon cooling systems.

This study proposes a novel multi-porous heat exchanger (MPHEX) as a passive, sustainable alternative to variable refrigerant flow (VRF) air conditioning systems, addressing the growing environmental burden of cooling demand. Through high-fidelity Lattice Boltzmann Method simulations of coupled heat and fluid transport, the MPHEX design is optimized to minimize exergy destruction. A case study for Tunisian conditions demonstrates that permeability optimization, when combined with solar-assisted preheating, reduces total exergy destruction by over 60% and increases the coefficient of performance (COP) by up to 20%, all while eliminating active mechanical regulation. The numerical results confirm strong experimental feasibility, positioning the MPHEX as a scalable, low-energy, and low-maintenance cooling solution for sun-rich regions.