Heat transfer and pressure drop characteristics of microchannel cold plate in commercial CPU-package cooling system

The purpose of this paper is to investigate the cooling performance of cold plate coupled CPU package (CPcCPU) with multi-layered microchannel cold plate designs. First, the Z-type, U-type, and I-type inlet/outlet manifolds are compared. The I-type manifold performs best with the lowest thermal resistance and flow resistance. Then the I-type CPcCPUs with different microchannel layer numbers (MCLN) are modeled and compared. The pressure drop of CPcCPU is greatly reduced when MCLN increases. But CPcCPU with bigger MCLN doesn't always achieve a higher maximum power of CPU (MPCPU). The I-type-5L performs better with a balance of cooling performance and material cost, which has a pressure drop decrease ratio of 89.5 % and an MPCPU increase ratio of 22.9 % compared with I-type-1L when the water flow rate is 0.3825 L·min^-1. Then, a modified stepped multi-layered microchannel CPcCPU I-type-9L-CUT1 is proposed, in which the ineffective microchannels are removed. I-type-9L-CUT1 performs better than I-type-5L, and it achieves a higher MPCPU of 278.48 W and a lower pumping power of 3.337 mW. Further, the thermal conductivity of thermal interface material TIM2 is improved from 5 W·m^-1K^-1 to 86 W·m^-1K^-1 for I-type-9L-CUT1, and MPCPU is improved by 58.2 W. The CPcCPU with the best performance is I-type-9L-CUT1 with indium as TIM2 material, which has the highest MPCPU of 336.7 W and the lowest thermal resistance of 0.1727 K·W^-1 while the pressure drop is only 523.5 Pa. It also achieves the highest chip area-averaged heat flux of 206.5 W·cm^-2.