International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In the paper, geometry parameters of a longitudinally-finned vertical shell-and-tube latent thermal energy storage (LTES), which uses paraffin as the phase change material (PCM) and water as the heat transfer fluid (HTF) have been optimized with the objective of maximizing its storage capacity, i.e. the amount of stored and released thermal energy. Three objectives were set: maximization of stored thermal energy in 8 h, maximization of released thermal energy in 12 h and a combination of the two, in which each objective was given equal significance. There geometry parameters were optimized; fin number, fin width and tube diameter. Optimization has been performed using response surface methodology and Box-Behnken approach. Responses have been obtained numerically, through an experimentally validated modeling procedure and solver scheme. The responses for each objective were fitted with a regression polynomial function and the fitness quality was evaluated through a coefficient R2. Optimization procedure offers different optimum values of analyzed parameters for each objective and provides guidance for choosing the favorable values of LTES geometry parameters in order to enhance LTES thermal performance.

The study reports on a series of numerical simulations conducted to assess how tube diameter affects charging (melting) and discharging (solidification) performance in a shell-and-tube latent thermal energy storage (LTES) with longitudinal fins. In the investigated LTES, water flows through the tubes and serves as the heat transfer fluid (HTF), while paraffin is used as the phase change material (PCM) and fills the shell side. Employing an experimentally validated mathematical model and numerical procedure, LTES charging and discharging performances were investigated for three tube diameters: 28/24, 38/34 and 48/44 mm. LTES performance for different tube diameters was assessed by comparing melting and solidification times, as well as stored and released thermal energies in 8, 9 and 10 h of charging and 12, 13 and 14 h of discharging for each configuration. Results show that larger tube diameters accelerate melting and solidification processes due to increased conductive surface area, but also decrease LTES energy storing capacity as the amount of the PCM reduces as a result of increased tube diameter. The results indicate that tube diameter greatly influences LTES thermal performance and must be chosen carefully for the LTES to be effective.