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).
Partially Confined FC-72 Spray-Cooling Performance: Effect of Dissolved Air
The objective of this paper was to investigate the heat transfer performance of a partially confined FC-72 spray with varying dissolved-air concentrations. An experimental test rig consisting of a spray chamber coupled to a fluid-delivery-loop system was used to obtain temperature, pressure, and critical heat flux data. A downward-facing nozzle within the spray chamber allowed the FC-72 fluid to be sprayed onto an upward-facing thick-film resistor heater. The heater was mounted onto a glass post, with a sump system to allow removal of excess fluid. Type-E thermocouples were embedded in the post to obtain temperature data. The parametric ranges for experimental testing were as follows: volume-percent concentration of dissolved air was 5 ≤ C m ≤ 18%, chamber pressure was 6.90 x 10 4% ≤ P ch ≤ 8.27 x 10 1 N/m 2 (10 ≤ P ch , ≤12 psia), liquid subcooling was 2≤ ΔT sc ≤ 12°C, and volumetric flow rate was 6.3 0.0 gph). Test data were obtained for comparison of critical heat flux with varying C while controlling the spray chamber pressure. The applicability of Henry's law to the current system was investigated, and air concentration measurements using Henry's law were compared with those obtained using a direct sample method. An empirical mathematical relationship allowing for determination of surface heat flux with varying flow rate was also developed. The relationship was obtained using test data at flow rates of V = 6.31, 8.41, and 10.5 cm 3 /s and was validated using experimental data obtained for flow rates of V = 7.36 and 9.46 cm 3 /s (7.0 and 9.0 gph).
CFD simulation of hydrodynamics and heat transfer in gas phase ethylene polymerization reactors
Abstract The hydrodynamics and temperature of a two-dimensional gas–solid fluidized bed of gas phase olefin polymerization reactor had been studied. A two-fluid Eularian Computational Fluid Dynamics (CFD) model with closure relationships according to the kinetic theory of granular flow has been applied in order to simulate the gas–solid flow. Fluidization regime and gas–solid flow pattern were investigated using three different drag models. Model predictions of bed pressure drop were compared with corresponding experimental data reported in the literature to validate the model. The predicted values were in reasonable agreement with the experimental data. The temperature behavior of fluidized bed with various drag models was investigated. The temperature gradient in the primary section of the bed was much larger than the gradient in other sections and the effect of all drag models on temperature gradient along the bed was approximately similar.