Heat pipe integration in vapour compression refrigeration: Refrigerant-side enhancement, air-side heat recovery, and electronics thermal management

The rapid global increase in cooling demand—especially in hot and humid regions—is intensifying pressure on electrical grids and accelerating the need for higher-efficiency vapour compression refrigeration systems (VCRS). This review evaluates heat pipe (HP) integration in VCRS using a three-pathway framework: (i) refrigerant-side enhancement, (ii) air-side heat recovery and latent-load management via heat pipe heat exchangers (HPHEs), and (iii) thermal management of electronic controllers. Particular emphasis is placed on a closed-loop HP configuration that couples the suction and liquid lines, achieving passive liquid subcooling and suction superheating without fluid mixing. Reported benefits include increased coefficient of performance (COP), reduced refrigerant charge, improved compressor reliability, and the potential elimination or downsizing of auxiliary components such as accumulators and reheaters. On the air side, HPHEs enable effective sensible and latent heat recovery in humidity-sensitive applications. In contrast, HP-based heat sinks and vapour chambers stabilise inverter and controller temperatures under transient electrical and thermal loads. Across all pathways, the review synthesises recent progress in HP geometries, working fluids—including nanofluids—fill ratios, orientation effects, and hybrid HP–VCRS architectures. It compares experimental, numerical, and field findings across applications such as food preservation, buildings, and data centres. The review concludes by identifying priority research gaps—including standardised test protocols, long-duration reliability assessment across multiple climates, multi-objective system-level optimisation, and scalable integration pathways—and presents a roadmap to accelerate industrial adoption of HP-integrated VCRS.