Phase change material-based heat exchangers with variable fin geometries for HVAC energy savings

Sharma, Rahul Kumar, Saikia, Pranaynil, Rakshit, Dibakar and Ugalde-Loo, Carlos E. ORCID: https://orcid.org/0000-0001-6361-4454 2026. Phase change material-based heat exchangers with variable fin geometries for HVAC energy savings. Applied Thermal Engineering 309 (Part 1) , 133617. 10.1016/j.applthermaleng.2026.133617

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Abstract

Fresh-air ventilation mandated for indoor air quality adds substantial cooling burden to heating, ventilation and air conditioning (HVAC) systems in hot, rapidly urbanising regions. This paper presents the numerical evaluation of a phase change material (PCM)-air heat exchanger (PAHX) retrofitted to an HVAC system of an office space to pre-cool fresh air. Octadecane was adopted as the PCM (melting point 27.97 °C), which is regenerated overnight by 24 °C return air. Further, the effect of fin number and aspect ratio on the PCM side and the propagation of the resulting outlet-air temperatures is analysed through a complete vapour-compression energy balance. Six fin configurations and an unfinned case were simulated for ambient temperatures of Delhi's composite climate for April to September. Fin geometry strongly influenced performance: the best-performing configuration (Case 6, three 50 mm × 2 mm fins per 15° sector) reduced the outlet air temperature by up to 6.78 °C (4.42 °C on average over the 8 h cycle in June), shortened complete PCM melting by up to 43%, reduced the sensible ventilation load by 14.08% and achieved sensible HVAC energy savings of 2.32–8.09% across the six months, compared with 1.97–6.73% for the unfinned design. A full charge–regeneration cycle showed that 95% of the latent capacity is recovered within 7 h using return air. Because the reported savings are based on the sensible ventilation load only, whole-system savings including dehumidification will be lower, particularly in the humid monsoon months. The results highlight the potential of PCM-based heat exchanger retrofits for sustainable building cooling in composite climates and for reducing HVAC energy consumption, supporting climate targets and fostering energy-efficient urban growth.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Engineering
Additional Information:	RRS policy applied
Publisher:	Elsevier
ISSN:	1359-4311
Date of First Compliant Deposit:	27 October 2026
Date of Acceptance:	10 October 2026
Last Modified:	27 Oct 2026 14:45
URI:	https://orca.cardiff.ac.uk/id/eprint/190455

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