Abstract
This study experimentally investigates the effect of different values of wall heat flux intensity on the melting of RT44HC Phase Change Material (PCM) in a rectangular test cell. A new novel experimental test rig to provide accurate data for the validation of numerical models of phase change was developed. The designed and constructed test rig consists of a horizontal rectangular cross-section test cell formed from polycarbonate sheet with copper plates and mica heaters to provide controlled uniform wall heat flux. Experiments were performed for three constant uniform wall heat flux values (q″wall = 675, 960 and 1295 W/m2) applied to both left and right sides of the test cell. An imaging technique was used to visualize and record the movement of the solid-liquid interface using a Canon EOS DSLR Camera. The results obtained show a strong correlation between the magnitude of wall heat flux which drives the convective heat transfer and melt fraction development in the PCM. The results also show that increasing the input power from 675 W/m2 to 960 W/m2 to 1295 W/m2 reduces the total time for the melting process by 26.3% and 42.10% respectively. The raw data set comprised of measured temperatures and observation of melt fraction development provide a useful data set for validation of numerical models aiming to simulate the melting process in a rectangular cross-section test cell.
Highlights
Latent heat thermal energy storage (LHTES) has a wide range of potential engineering applications and has recently gained considerable attention for space heating and cooling due to environmental concerns and the rising cost of fossil fuels
In the early stage of heating and the initial Phase Change Materials (PCMs) melting phase (
Natural convection becomes dominant and the heat transfer coefficient from the heated surface to the PCM increases meaning that the power input is transferred from the wall to the PCM for a smaller temperature difference, the rate of increase of local wall surface temperature slows down (Quasi-Steady Convection Phase (III))
Summary
Latent heat thermal energy storage (LHTES) has a wide range of potential engineering applications and has recently gained considerable attention for space heating and cooling due to environmental concerns and the rising cost of fossil fuels. Several recent studies have focused on vertical/horizontal rectangular enclosures with imposed boundary conditions (BC) of a) constant wall temperature (CWT), and (b) constant wall heat flux (CWF) [7] and [8] This is due to their common occurrence in a range of potential applications, including waste heat recovery systems, solar thermal systems and cooling systems for electronic devices. Wang Y et al [9] performed an experimental investigation of the PCM melt process in the vicinity of a uniform temperature heated vertical wall in a rectangular enclosure From the experiments, it was clear from the variation of Nusselt number with the time that three different heat transfer regimes occurred during the melt process. Kamkari B et al [13] investigated experimentally the heat transfer process and melting behaviour during the solid-liquid phase change of lauric acid (Pr = 100) in a rectangular enclosure at different inclination angles (0°,45°,90°). The overall objectives of the proposed study were to (1) visually observe and record the movement of the solid-liquid interface with time, (2) measure the temperature distribution within the PCM with high accuracy and resolution, and (3) to develop an experimental data set (temperature distribution and location of solidliquid interface) suitable for validation of future simulation work on natural convection inside LHTES of similar geometric design
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