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In liquid-cooled large drives, controlling air temperature and maintaining air circulation is very important to the lifetime and functions of electrical and electronic components in power cell cabinet. In application, air/water heat exchangers and associated fans are employed to cool the air and force it through the cells. A computational fluid dynamics (CFD) analysis is performed to predict the air circulation in cell cabinet. The results are applied in air baffle arrangement to obtain an ideal air flow distribution. A fundamental analysis is conducted for heat exchanger and its thermal performance defined. It is found that the air supply temperature from heat exchanger is almost independent of air flow rate and altitude within application range. A thermal model is developed to simulate air temperatures into and out of cell cabinet heat exchanger for evaluating its cooling capacity. Flow and heat-run tests are performed for a cell cabinet. The testing results prove that the simulation models are accurate, and the developed air-cooling system can satisfy cooling requirement. A parametric study is complemented with the simulation models to guide cooling management regarding variations in operational and environmental conditions.

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As the state-of-the-art technology for energy saving, variable-frequency drives (VFDs) can be applied in nuclear power plant to drive recirculation pumps for coolant flow control. Due to requirement of high reliability, such as in nuclear industry, air natural convection cooling plays an important role in and while brings out a great challenge to thermal management for electronic unit. With an application of single board computer module in control system, another cooling challenge comes from heat flux increase caused from smaller footprint, since all of components, such as processor, chipset, memory and power supply etc., are built into one board. In the paper, cooling technologies for the single board computer module are investigated and developed, focusing on natural air heat convection from heat sink to ambient and heat conduction from board to heat sink. Based on thermal analysis associated with mechanical consideration, one heat sink is used to cool multiple components on the board. Two TIMs (thermal interface materials) and one heat spreader are employed for heat conduction from CPU and chipset to heat sink, respectively. Extrusion heat sink is selected with a comprehensive consideration of cost and thermal performance. A numerical simulation model is developed and validated against testing results. With the verified model, effects of fin arrangement on heat sink performance are analyzed. A study is conducted for optimization of base plate and fin thickness, and accordingly a heat sink is developed for the present application. Environmental conditions, such as temperature, altitude, and humidity etc., are analyzed to investigate their influence on cooling performance of natural air convection.