Numerical simulation on spray cooling with microencapsulated phase change material suspensions

The flow and heat transfer features of spray cooling with microencapsulated phase change material suspension (MPCS) are studied numerically. The movement of spray droplet, the flow and heat transfer of the liquid film, and the latent heat absorption in MPCS are described with discrete phase model (DPM), Lagrangian wall film (LWF) model, and equivalent heat capacity method, respectively. The results indicate that the latent heat absorbing of MPCS can substantially improve the heat transfer compared to water, up to 21.6 %. The contradictory effect of latent heat ability and large viscosity of MPCS on the heat transfer makes it having the best heat transfer at 5 % concentration. A reduction in the droplet diameter can improve the heat transfer due to the increased disturbance within the liquid film. The Nu decreases with the growth of spray height at a reduction rate of approximately 7.4 % when H/D ≤ 8, but the decline clearly slows down when H/D > 8 with a reduction of only about 1.0 %. It exists a critical flow value of Q = 7.5 g/s for the influence of spray cone angle on the heat transfer, the evaporation rate and turbulent disturbance in the liquid film is dominant, respectively, when Q ≤ 7.5 g/s and Q > 7.5 g/s. Compared to the water, Nu for MPCS shows a peak within the phase change temperature range, and the optimal inlet temperature is θ = −0.11, which is slightly beneath the melting peak temperature of the MPCS.