Experimental Investigation on Heat Transfer Characteristics of Microcapsule Phase Change Material Suspension in Array Jet Impingement

A closed-loop experimental system is established to investigate the heat transfer characteristics of microcapsule phase change material (MEPCM) suspension in an array jet impingement. Eicosane with a melting peak at 40.8°C is used as the capsule core of the MEPCM particle. Five kinds of array-hole nozzles with the same hole cross-sectional area are employed to analyze the influence of critical parameters, including the nozzle hole number, hole spacing, impinging distance, and jet temperature. It shows that a 5% suspension may improve the heat transfer coefficient of the array jet by up to 23.5% compared with water. The heat transfer of an array jet is obviously stronger than that of a single jet, but too much hole number is not conducive because of the entrainment interference between adjacent jets. A larger hole spacing or smaller impinging distance may weaken the cross-flow accumulation on the impinged surface, thus enhancing the heat transfer capability. The heat transfer coefficient of the array jet presents a secondary peak value at the end of the jet-core region. The latent heat absorption of the capsule core results in superior heat transfer of the suspension compared to that of water only in a specific range of jet temperatures, the optimum of which is approximately 10°C lower relative to the peak melting temperature. In addition, the melt completion time of a single MEPCM particle and the critical flow rate of the suspension are predicted theoretically.