Experimental Investigation on Melting Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry Under Stirring

As avionics advance, heat dissipation becomes more challenging. Microencapsulated phase change material slurry (MPCMS), with its latent heat transfer properties, offers a potential solution. However, the low thermal conductivity of microencapsulated phase change material (MPCM) limits heat transfer rates, and most studies focus on improving conductivity, with little attention given to convective enhancement. This study prepared MPCMS with an MPCM mass fraction (Wm) of 10% and 20%, investigating melting heat transfer under mechanical stirring at 0–800 RPM and heat fluxes of 8.5–17.0 kW/m2. Stirring significantly alters MPCMS heat transfer behavior. As rotational speed increases, both wall-to-slurry and internal temperature differences decrease. Stirring extends the time at which the heating wall temperature (Tw) stays below a threshold. For example, at Wm = 10% MPCM and 8.50 kW/m2, increasing speed from 0 to 800 RPM raises the holding time below 70 °C by 169.6%. The effect of MPCM mass fraction on heat transfer under stirring is complex: at 0 RPM, 0% > 10% > 20%; at 400 RPM, 10% > 0% > 20%; and at 800 RPM, 10% > 20% > 0%. This is because as Wm increases, the latent heat and volume expansion coefficients of MPCMS rise, promoting heat transfer, while viscosity and thermal conductivity decrease, hindering it. At 0 RPM, the net effect is negative even at Wm = 10%. Stirring enhances internal convection and significantly improves heat transfer. At 400 RPM, heat transfer is positive at Wm = 10% but still negative at Wm = 20%. At 800 RPM, both Wm levels show positive effects, with slightly better performance at Wm = 10%. In addition, at the same heat flux, higher speeds maintain Tw below a threshold longer. Overall, stirring improves MPCMS cooling performance, offering an effective means of convective enhancement for avionics thermal management.