Role of extended fins and graphene nano-platelets in coupled thermal enhancement of latent heat storage system

Abstract

To bring modernisation in low carbon economy, the latent heat storage (LHS) systems are crucial for sustainable future of smart energy generation and management systems for renewable sources. This article provides in-depth numerical analyses of 3-dimensional computational models incorporating coupled thermal enhancement techniques for identifying optimal solution to guarantee higher charging rate, higher total enthalpy and better thermal distribution of LHS system. Paraffin is selected as phase change material (PCM), graphene nano-platelets (GNP) as nano-additives and longitudinal, circular and wire-wound fins as extended surfaces in vertical shell-and-tube configurations. Based on numerical analyses, the extended surfaces have registered better thermal distributions and charging rates as compared to nano-PCMs. The geometrical orientation of extended surfaces and volume concentration of nano-additives have significant influence on melt front movement, natural convection and heat transfer performance. The peak values of heat fluxes are significantly increased from 2.25 kW/m 2 for paraffin without thermal enhancement to 35.86, 47.23 and 88.13 kW/m 2 for nano-PCM with 1% GNP in circular, longitudinal and wire-wound fins configurations. Hence, the charging duration for capturing 11.09 MJ is significantly reduced to mere 1.02 h for wire-wound fins configuration as compared to 23.5 h for paraffin without thermal enhancement. Likewise, the charging rate of wire-wound fins configuration is 20.95%, 35.96% and 89.94% higher than circular fins, longitudinal fins and nano-PCMs without extended surfaces, respectively. Moreover, the increase in volume concentration from 1% to 5% has adverse implications on accumulative enthalpy, natural convection and charging rate. Therefore, the novel design of coupled enhancement with wire-wound fins configuration and nano-PCM with 1% GNP are established as optimum solution for potential wide-ranging practical utilisations of LHS system.

Performance Evaluation of Coupled Thermal Enhancement through Novel Wire-Wound Fins Design and Graphene Nano-Platelets in Shell-and-Tube Latent Heat Storage System

“…In order to acquire optimal performance enhancement in a shell-and-tube-based LHS system, the coupled enhancement through extended fins and nano-additives are introduced and investigated in three-dimensional computational domains. The physical models of coupled enhancements include longitudinal, radial and wire-wound fins with nano-PCMs in shell-and-tube configuration, as illustrated in figure number 1 in [38]. The motive behind transient simulations of coupled enhancement in three-dimensional computational domains is to propose an optimal combination that can guarantee the retrieval of higher enthalpy capacity at higher discharging rate, better thermal distribution in the shell container and higher heat transfer performance.…”

“…As illustrated in figure number 1 in [38], the physical models of shell-and-tube with multiple passes and tubes with longitudinal, radial and wire-wound fins conform to geometrical constrains and symmetries. To reduce the computational cost and time, the computational domain for each extended fin scenario is chosen by adhering to geometrical symmetries of tube passes in the shell container.…”

“…The finite volume method (FVM) is implemented to discretise the mass, momentum and energy equations for coupled enhancement scenarios in three-dimensional computational domains, as illustrated in Figure 1 in [38]. A pressure-based sequential algorithm is chosen for simulating the transient discharging cycle.…”

“…The liquid fractions for each scenario are matched and the grid-resolution independency with mesh sizes of 5.35 × 10 7 , 3.70 × 10 7 , 2.35 × 10 7 and 8.08 × 10 7 are established, respectively. Likewise, the time-stepping for all scenarios with their respective grid-resolutions are investigated with three different time steps of 0.1, 0.5 and 1 s. The liquid fractions response to the varied time-stepping are uniform, and hence, the time step of 1 s is chosen for reliable numerical results at lower computational cost [38].…”

“…In addition, the comparative analyses are conducted by simulating the discharging cycles for fourteen varied scenarios including base PCM and nano-PCMs in a shell-and-tube with a standard plain tube and a tube with longitudinal, radial and wire-wound fin configurations. In our previous publication [38], the influence of coupled enhancement on charging cycles of LHS systems were discussed. Whereas this article is focused on understanding and investigating the impact of coupled enhancement on discharging cycles of LHS systems, which has not been reported in the literature.…”