Phase change in multi-tube heat exchangers

Abstract

a b s t r a c tIn this paper, melting of a phase change material (PCM) in a multi-tube heat exchanger (MTHX) is investigated. Water, as the heat transfer fluid (HTF), flows through the inner tube/tubes and the outer one while RT35 as the PCM fills the middle. The aim of this study is to investigate the effect of number of inner tubes as a geometrical parameter during charging process. Also consequences of increasing operational parameters including the HTF mass flow rate and inlet temperature are studied. In order to understand the effects of the proposed configurations, a comparison between double pipe and simple MTHX is carried out. Results show that as the inlet temperature increases melting process accelerates and complete melting time reduces, whereas, similar mass flow rate increase doesn't reduce the melting time to such an extent. By increasing the number of inner tubes from 1 to 4 in the shell side of the MTHX, melt region enlarges and its including vortices strengthens which leads to a dominated convective heat transfer and thus a higher melting rate. This increase in number of tubes leads to 29% reduction in melting time.

Experimental Investigation of Sinusoidal Tube in Triplex-Tube Heat Exchanger during Charging and Discharging Processes Using Phase Change Materials

“…To find the thermal resistance of the heat exchanger, RHTF, Equation (14) can be used. (14) In this equation, α is the convection heat transfer coefficient and Nu is Nusselt number. Considering the laminar or turbulent fluid flow in the tube, Equations (15) or (16) (16) Here, Re is the Reynolds number, Pr Prandtl number, f the friction factor, and µ the fluid viscosity.…”

“…They showed that application of multi-tubes inside the shell would improve the heat transfer rate in the charge and discharge process. Esapour et al [14] examined the behavior of PCMs in multi-tube heat exchangers. In this study, water flows as a working fluid through the inner and outer tube/tubes, and the middle tube was filled with a phase change material of RT35.…”

Numerical investigation of dynamic melting process in a thermal energy storage system using U-tube heat exchanger

“…26 Therefore, it is necessary to conduct a detailed parametric study on the HTF flow rate for the U-tube system. The heat flux, average temperature, and liquid fraction of PCM under different HTF flow rates are shown in Figures 9 and 10.…”

Numerical Simulation of an Aluminum Container including a Phase Change Material for Cooling Energy Storage

“…They also compared the numerical results, which were obtained using the FEMLAB solver, with experimental ones. Esapuor et al [22] implemented the enthalpy method to perform 3D simulations of a PCM in multi-tube heat exchanger units. Allouche et al [23] developed and validated a computational fluid-dynamic (CFD) model for the numerical simulation of a PCM slurry in a horizontal tank.…”