Numerical analysis of a medium scale latent energy storage unit for district heating systems

Abstract

The present paper describes the application of computational fluid-dynamics (CFD) to the design and characterization of a medium scale energy storage unit for district heating systems. The shell-and-tube LHTES unit contains a technical grade paraffin (RT100) and uses water as heat transfer fluid (HTF). The system has been designed to transfer heat from the primary to the secondary heat district heating networks. After an initial description of the LHTES unit and a wide literature overview on the subject, the paper discusses the need for thermal enhancement to improve the thermal conductivity of the phase change material (PCM). A solution based on a paraffin-graphite composite with a 15% graphite volume fraction has been found to be well performing in this particular application. Several operating scenarios characterized by heat requests ranging between 130kW and 400kW have been explored and the main outputs presented as function of Re and St numbers. The time-wise variations of other significant quantities such as liquid fraction, sensible and latent energy content, HFT outlet temperature and heat fluxes have been also presented and discussed. A final discussion on the possible system configurations shows that in comparison to traditional water storage systems for district heating, LHTES systems provide, depending on the chose alternative, higher energy storage densities.

Nano-enhanced phase change materials for improved building performance

“…Colella et al [104] numerically investigated the use of a paraffin-graphite composite with a 15% graphite volume fraction to enhance a shell-and-tube energy storage unit with water as the heat transfer fluid for district heating systems. Compared to traditional water storage systems for district heating, the energy storage unit with the nano-enhanced PCM can provide higher energy storage densities.…”

Complete Analysis of the Impact of Distributed Heat Accumulators on the Efficiency of the District Heating Networks

“…TES as an element of district heating network located near power station with CHP or supplied by renewable energy source can increase efficiency of the running of DH [11,12,13,14,15]. The influence of distributed heat storages TES type on parameters of operation of DH networks until now has not been analyzed.…”

Second Law Optimization of a PCM Based Latent Heat Thermal Energy Storage System with Tree Shaped Fins

“…A wide range of techniques have been proposed to enhance thermal performance of PCMs. Among the others, the use of PCMgraphite composites [3][4][5], encapsulation [6], and dispersion of nanoparticles [7][8][9]. However, most of the investigations concerns the use of extended surfaces (fins) to improve the performance of shell-and-tube LHTES units [10][11][12][13][14], since this configuration is closer to real PCM heat exchanger applications.…”