Performance analysis of an HVAC system retrofitted with nano-enhanced phase change material-based heat exchanger

Incorporation of fresh air into a building through Heating, Ventilation, and Air conditioning (HVAC) systems improves indoor air quality; however, this poses a challenge as it increases the cooling load and increases the energy demand of the building. In the present study, an existing office in New Delhi, India, which is located in the composite climate zone, is analyzed for different factors contributing to cooling load. Further, a concentric tube type, phase change material (PCM) based heat exchanger is numerically modelled to reduce the energy consumption of a conventional HVAC system. The integration aims to extract the thermal energy from fresh air, ultimately reducing overall energy consumption. The PCM used is octadecane due to its proximity to human comfort range. The modified system reduced the cooling load due to higher temperature fresh air by 7.27 % and achieved an energy savings of 3.28 % over a conventional HVAC unit. The reduction in the fresh air cooling load and energy saving is further enhanced by the addition of CuO nanoparticles in PCM stored in the annulus of the heat exchanger. In addition, internal longitudinal fins are incorporated into the internal tube of the heat exchanger. It is found that with 24 internal fins and 1 % CuO nanoparticle, the cooling load and energy consumption can be reduced by 23.25 % and 7.81 %, respectively. The study offers policymakers sustainable and energy-efficient alternatives for HVAC systems, presenting viable solutions to diminish energy demand and contribute to the fight against climate change.