Experimental investigations of charging/melting cycles of paraffin in a novel shell and tube with longitudinal fins based heat storage design solution for domestic and industrial applications

Abstract

Due to vulnerability of solar energy based technologies to weather fluctuations and variations in solar thermal irradiance, thermal energy storage (TES) systems with their high thermal storage capacity offer a sustainable solution. In this article, experimental investigations are conducted to identify thermal performance of latent heat storage (LHS) unit in connection with flat plate solar collector during charging cycles. LHS unit is comprised of novel geometrical configuration based shell-andtube heat exchanger with longitudinal fins, paraffin as thermal storage material and water as heat transfer fluid (HTF). In order to overcome the effect of low thermal conductivity of paraffin, the effective surface area and overall thermal conductivity for heat transfer is significantly improved by employing longitudinal fins. Moreover, the vertical orientation of longitudinal fins supports natural convection, which can assure rapid charging of paraffin in LHS unit. In experimental tests, the focus is on probing the heat transfer mechanism and temperature distribution in entire novel LHS unit, the influence of inlet temperature and volume flow rate of HTF on phase transition rate and mean power. Experimental results revealed that natural convection significantly influences the phase transition rate. Therefore, enthalpy gradient is noticed between paraffin at top, central and bottom positions in LHS unit. Likewise, the phase transition rate and mean power of LHS unit is significantly increased by a fraction of 50.08% and 69.71% as the inlet temperature of HTF is increased from 52 o C to 67 o C, respectively. Similarly, it is concluded that volume flow rate of HTF has a relatively moderate influence on thermal performance; however the influence declines with an increase in inlet temperature of HTF. Due to significant enhancement in thermal performance, the novel geometrically configured LHS unit can accumulate about 14.36 MJ of thermal energy in as less as 3 hours. Furthermore, a broad range of domestic and commercial energy demands can be fulfilled by simply assembling several LHS units in parallel sequence.

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

“…To conduct charging cycles, the water supply is directed to pass through serpentine copper tubing in the solar collector, where steady radiant thermal energy from solar simulators is absorbed by the water. The technical specifications and operation details of the solar simulators based solar collector system is discussed comprehensively in [22,41], as presented in Table 1. The high temperature water at the solar collector outlet is directed to pass through the LHS tank, where heat transfer occurs between high temperature water in the tubes and paraffin in the shell container.…”

“…However, the literature lacks thermal evaluation of shell-and-tube heat exchangers with multi-tube passes and longitudinal fins with relatively higher thermal storage capacity to support integration into practical applications. Therefore, a novel geometrical configuration of a shell-and-tube heat exchanger with multi-tube passes and longitudinal fins was previously designed and optimised in [21], developed and experimentally examined for charging and discharging cycles in [22,23]. The experimental evaluations were focused on vertical and radial temperature distributions, and melting and solidification rates of paraffin in the proposed design solution.…”

“…Thermal performance evaluations of proposed novel LHS system are based on experimental data acquired from twenty-eight charging and discharging cycles, which is symbolic and unprecedented contribution to literature. The above-mentioned thermal performance evaluations have not been considered or published in our earlier articles [21][22][23]. Moreover, this article is focused on developing empirical correlations for charging and discharging effectiveness, which will empower to evaluate the design characterisation and employability of this novel LHS system in practical applications.…”

Heat transfer evaluation of metal oxides based nano-PCMs for latent heat storage system application

“…It was noticed that the optimised design under increasing inlet temperature from 50-70 o C significantly improved the phase transition rate and total enthalpy by 68.8% and 18.06%, respectively. Later on, the proposed novel design was experimented for series of charging and discharging cycles with connection to solar collector [14][15][16]. It was reported that the proposed design was capable of charging 14.35 MJ in 3 h and discharging 13.63 MJ in 1.5 h. Also, the mean charging and discharging powers were augmented by 69.71% and 36.05% with increasing temperature gradient.…”

“…This article aims to conduct a comprehensive numerical analyses on fourteen commercial metal-oxides based nano-PCM samples with three volume concentrations to evaluate their thermo-economic performance in shell and tube heat exchanger, which are neither considered in [13][14][15]28] nor reported in previous literature. Numerical model for nano-PCM include the effects of thermo-physical properties of base material and metal-oxides, nanoparticles size and volume concentrations, and operating temperature.…”