| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === The CPU liquid cooling module normally consists of the pump, the water block, and the radiator equipped with an axial-flow fan for dissipating the thermal energy to its environment. Among these four components, water pump and cooling fan are the active parts, which need the external power input and are worn out frequently. It follows that the reliability becomes an obstacle in selecting the liquid cooling solution. To relieve this concern, this research proposes an innovative idea to extract flow energy from the cooling stream generated by the pump, and use it as the power source for the cooling fan. Hence, the reliability issue can be significantly lessened since this water-driven fan becomes a passive component.
In this work, numerical and experimental technologies are integrated to design and validate this water-driven cooling fan. Firstly, numerical visualization is utilized to identify the adverse flow patterns inside the water-driven motor of the 12cm-in-diamteter cooling fan for serving the foundation of improving design alternatives. Several essential parameters, such as the angle between inlet and outlet of the impinging stream, geometric shape, number, and arrangement of blades, and buffer gaps on the motor housing, are investigated systematically via the CFD tool. Also, The superior performance of water-driven motor is evaluated by its rotating speed, which can be determined by the zero-torque condition. As a result, the calculated rotating speed of the 5-blade design can be enhanced from 1,043 to 1,694 rpms for the best design, which has the buffer gaps on motor casing and the two-level arrangement on the blades.
Furthermore, three mockups representing the maximum, medium, and low rotating ranges are manufactured via CNC technique for checking the validity of CFD prediction. Consequently, it is found that CFD and test results are in the similar trend while a roughly 30% deference is observed. This deviation is contributed to the unconsidered drags from the bearing and other assembly issues. In summary, this work establishes a systematic evaluation scheme to design a water-driven fan for the CPU liquid cooling system. Also, this innovative fan design is constructed successful to generate a rotating speed at 912 rpm, which is within the operating range for the 12cm-in-diameter cooling fan on the market nowadays.
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