Thermodynamic performance of a novel shell-and-tube heat exchanger incorporating paraffin as thermal storage solution for domestic and commercial applications.

Abstract

This article is focused to evaluate thermal performance of commercial grade paraffin in a novel shell-and-tube heat exchanger with multi-tube passes and longitudinal fins as latent heat storage (LHS) system. Thermal performance assessments of latent heat storage system are conducted with respects to charging/discharging power, accumulative thermal energy storage/retrieval, thermal efficiencies and effectiveness, heat transfer characterisation and nature of melt front propagation. The average charging and discharging powers are significantly enhanced by 75.53% and 27.04% with an increase in temperature gradient between paraffin and inlet water from 52 oC – 62 oC and 15 oC – 5 oC, respectively. Likewise, the maximum charging and discharging powers are augmented from 2.15 kW – 2.63 kW and 5.18 – 10.37 kW with an increase in flow rate from 1.5 – 3 l/min, respectively. Furthermore, the average effectiveness, Nu-Ra and heat transfer coefficient are significantly improved with an increase in temperature gradient and moderately reduced with upgrading volume flow rate. The range of Rayleigh numbers for charging cycles have indicated turbulent nature of melt front movement and supportive behaviour of longitudinal fins orientations towards natural convection. Empirical correlations for average effectiveness and Nu-Ra are developed from experimental results to facilitate design estimation for employment of proposed LHS systems in domestic and commercial applications. These empirical correlations, to evaluate feasibility and employability of LHS systems in practical applications such as domestic hot water supply and space heating to maintain control room temperature, have been successfully implemented in real operating conditions.