Optimization design of a novel closed-loop spray cooling system
Due to the superiority of spray cooling system in removing high waste heat flux generated by the electronics, a novel spray cooling system combined with ejective condenser is proposed and its work procedure is introduced. Most previous relevant studies are only focus on the influences of parameters on the spray cooling performance. In the present paper, a multi-objective optimization function on the overall system is provided through the analysis of fluid flow and heat transfer characteristics, and the Particle Swarm Optimization (PSO) is applied to solve this problem. The optimized results of the total mass, the total pump power consumption and the heat surface temperature are obtained at different heat power. The optimal system structure parameters of the sprayer, the ejective condenser, the radiator are obtained. The work conditions of the sprayer mass flow and the heat surface temperature are also got under the performance of minimum power consumption, minimum system mass and the lowest heat source temperature at heat source power 500 W (heat flux 500 W/cm2).
Review of aerospace-oriented spray cooling technology
Abstract Motivated by the concept of energy-optimized air/space vehicles, the design of more-electric and all-electric vehicles has become increasingly popular. With the advance of micro-electro-mechanical systems, on-board electronic/electrical devices become more integrated and miniaturized. It means that these highly-advanced devices should rely on a high heat-flux dissipation method to maintain an effective and safe operation. Spray cooling, universally recognized as the next-generation cooling scheme, has been extensively utilized in the thermal protection of the ground-based electric/electronic equipment. In contrast, the aerospace-oriented spray cooling (AOSC) application is extremely rare. It can be attributed to the fact that the research into the space/air-oriented spray cooling technologies is still in its infancy, which leads to a lack in the knowledge of alternations of flow patterns and heat transfer behaviors caused by the complicated space or high-altitude space. This paper presents a comprehensive review of the up-to-date published articles on AOSC and divides these published articles into four categories: 1) investigation into the effect of gravity on the cooling performance; 2) investigation into the effect of environmental pressure on the cooling performance; 3) study of the effect of acceleration and vibration on the cooling performance; 4) investigation of the aerospace spray cooling system. Additionally, comments, perspectives, and orientations are provided, in which several promising contributions are highlighted. This paper aims to promote the practical application of the AOSC system which could facilitate the development of the energy-optimized green air/space vehicle.
Local Heat-transfer Coefficient in Spray Cooling of Hot Surface
The local heat transfer in spray cooling is theoretically and experimentally studied. The theoretical expression of the heat-transfer coefficient is presented. The distribution characteristics of spray, i.e., the number flux and the size and velocity distributions of the droplets at a given location are combined with the single droplet characteristics upon impingement onto hot surface, i.e., the droplet heat-transfer coefficient, he bottom radius changing with time and the retention time of the drop at the surface. On the basis of expression, the local heat-transfer coefficient is evaluated at various locations in a full-cone spray, the distribution characteristics of which are known. Experiments on the spray-cooling rate of hot surface of a small metal specimen indicate both the fundamental validity and the limitation of the theory.