Vol.:(0123456789) 1 3 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-020-09864-9 Numerical study of melting and solidifcation in a wavy double‑pipe latent heat thermal energy storage system Amin Shahsavar 1  · Hafz Muhammad Ali 2  · Roohollah Babaei Mahani 3,4  · Pouyan Talebizadehsardari 5,6 Received: 25 March 2020 / Accepted: 18 May 2020 © Akadémiai Kiadó, Budapest, Hungary 2020 Abstract The objective of this paper is to develop the infuences of channel waviness on the performance of a latent heat storage system during phase change mechanism. The heat exchanger is a vertically oriented double pipe where the heat transfers to/from the PCM in the annulus by moving the water in the inner tube. Various wavelengths, as well as wave amplitudes, are examined at various fuid Re and water temperatures (T in ) to fnd the efects of channel waviness on diferent aspects of melting/solidifcation time, pressure drop, pumping power and exchanged heat rate. Increasing Re, T in and amplitude of wavy wall improves the system performance during melting and solidifcation mechanisms. Besides, it is found that there is an optimum dimensionless wavelength of 0.2 for achieving the minimum melting and solidifcation times as a result of maximum heat exchanged between the water and PCM. Furthermore, the waviness has an almost negligible efect on the pumping power which is reduced for the dimensionless wavelengths higher than 2.0. In the best scenario, the required time to melt and solidify the PCM reduces by almost 28.6% and 57.63%, respectively, using wavy channels compared with the smooth wall case. Keywords Latent energy storage system · Double-pipe heat exchanger · Wavy channel · Melting · Solidifcation · Liquid fraction List of symbols a w /m Wave amplitude A m Mushy zone constant C p /J kg −1 K −1 Specifc heat transfer coefcient g/m s −2 Gravity k /W m −1 K −1 Thermal conductivity L w /m Wave-length L f /J kg −1 Latent heat of fusion m/kg PCM mass P/Pa Pressure t m /s Melting/solidifcation time T/K Temperature T i /K Inlet temperature T m /K Melting temperature T e /K End temperature  V /m s −1 Velocity /m s −1 Velocity in x-direction v/m s −1 Velocity in y-direction Greek symbols /K −1 Expansion coefcient  Liquid fraction /kg m −1 s −1 Viscosity /kg m −3 PCM density ΔH /J kg −1 PCM latent heat * Pouyan Talebizadehsardari ptsardari@tdtu.edu.vn Roohollah Babaei Mahani roohollahbabaeimahani@duytan.edu.vn 1 Department of Mechanical Engineering, Kermanshah University of Technology, Kermanshah, Iran 2 Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Kingdom of Saudi Arabia 3 Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam 4 Faculty of Civil Engineering, Duy Tan University, Da Nang 550000, Vietnam 5 Metamaterials for Mechanical, Biomechanical and Multiphysical Applications Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam 6 Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam