Flow and heat analysis of liquid nitrogen cooling structure by CFD method

High-power devices for low-temperature applications require a liquid-cooled chamber structure with high cooling efficiency. The Computational Fluid Dynamics (CFD) method was used to simulate the flow and heat transfer process of the cavity structure, the microchannel structure, and the pin-fins structure under the condition of the liquid nitrogen-nitrogen two-phase flow as the refrigerant. The results show that the pin-fins structure has the best heat exchange effect among the three above structures. The circular pin-fins structure is easy to develop a branch in the direction of 45°, and the square pin-fins structure is conducive to the uniform flow velocity in the vertical direction. Compared with the parallel pin-fins structure, the flow velocity distribution in the circular and square pin-fins is more uniform when the pin-fins are staggered. Comparing the convective heat transfer coefficients in different liquid cooling chambers with pin-fin structures, under the same other parameters, the staggered arrangement is better than the parallel arrangement, and the square pin-fin is better than the circular pin-fin. The structure with the best heat transfer effect is the staggered 2 mm square pin-fin structure, and the convective heat transfer coefficient is 4223 W/(m²·K), which is 125.83% higher than cavity structure. The above structure is manufactured for physical verification. The temperature of the cold head under the 107.6 W heating power corresponds well with the simulation result under the same condition.