Numerical investigation on performance improvement of latent heat exchanger with sextant helical baffles

Abstract

• Numerical investigation on a novel latent heat exchanger with sextant helical baffles was implemented. • Helix angle exhibits an opposite effect on the thermal performance and comprehensive performance of shell side. • The thermal conductivity and pr number of the HTF are important factors affecting the shell-side heat transfer feature. • Internal-external fin structure shows a large impact on the melting process of PCM. • Nano-additives have a remarkable influence on the thermal conductivity and latent heat of Nano-PCMs. Latent heat thermal energy storage is a promising technology, which is becoming more and more widespread in industrial fields. A novel latent heat exchanger with sextant helical baffles is thus investigated numerically in this paper. The different helix angles (10°, 20°, 30°, 40°) of sextant helical baffle are employed to explore the shell-side thermal and comprehensive performances in latent heat exchanger. The geometric parameters of internal-external fins, including the height, thickness and shape, are studied to improve the melting rate of phase change material (PCM). Water, fuel oil JP-4, ethylene glycol and hydraulic oil are chosen as heat transfer fluids (HTFs). Nano-PCMs with various volume concentrations of TiO 2 (2%, 4% and 6%) are used to study the discharging characteristic of latent heat exchanger. The results indicate that shell-side heat transfer and integrated behaviors need to be considered comprehensively for the choice of helix angle. The longitudinal-shaped fin with 7.5 mm height and 1 mm thickness is studied as the optimal scheme. Smaller Pr number and larger thermal conductivity are applied to HTF to further enhance the heat transfer between HTF and PCM. Furthermore, the selection of Nano-PCM needs to comprehensively consider the requirements of thermal conductivity and phase change latent heat in practical application.