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).
Spray Cooling of IGBT Devices
The popularity and increased usage of insulated gate bipolar transistors (IGBTs) in power control systems have made the problem of cooling them a subject of considerable interest in recent years. In this investigation, a heat flux of 825 W/cm 2 at the die was achieved when air-water spray cooling was used to cool IGBTs at high current levels. The junction temperature of the device was measured accurately through voltage-to-temperature characterization. Results from other cooling technologies and other spray cooling experiments were reviewed. A discussion of electrical power losses in IGBTs, due to switching and conduction, is included in this paper. Experiments were conducted on 19 IGBTs, using data collection and software control of the test set. Three types of cooling were explored in this investigation: single-phase convection with water, spray cording with air-water and spray cooling with steam-water. The results of these experiments show clear advantages of air-water spray cooling IGBTs over other cooling technologies. The applications of spray cooling IGBTs are discussed in open (fixed) and closed (mobile) systems. Current and heat flux levels achieved during this investigation could not have been done using ordinary cooling methods. The techniques used in this investigation clearly demonstrate trio superior cooling performance of air-water spray cooling over traditional cooling methods.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.