Studies on Convective Cooling of Cryogenic Fluids Towards Superconducting Applications

Abstract

To understand the cooling aspect through natural convection in a cryogenic fluid interacting with a constant heat source, numerical simulations are carried out in a parallelepiped enclosure. The 3D form of N-S equations is solved to obtain the detailed flow features through path line profiles, isotherm contours and velocity vectors. The effect of heater aspect ratio (x/L) on the rate of heat transfer is studied in terms of the average Nusselt number (Nuave). The results indicate that effective heat transfer enhancement occurs for a small heater length, resulting in an efficient cooling. Increasing the heater length will favor heat transfer through conduction over convection. The maximum temperature difference across the fluid and the velocity magnitude are found to decrease with heater length. 3D and 2D results are in agreement for short heater lengths, but vary for higher heater lengths, presumably due to the essential effect of the heater width. Further analysis on different types of coolant reveals a constant correlation between Nuave and the Rayleigh number (Ra), with Nuave ~ Ra 0.374 . Benchmark validation for natural convection in a square enclosure is found to be satisfactory against the reported results.

Study of buoyancy driven heat transport in silicone oils and in liquid nitrogen in view of cooling applications

“…Towards this, buoyancy driven flow in an enclosed cavity [25] forms a good test case for the present validation. This particular benchmark analysis was successfully investigated in our earlier studies in a 2D geometry [18].…”

“…Prior to the present work, we have recently studied numerically the convective flow induced by a heater immersed in a 10 cst silicone oil [18]. It was shown that the characteristics of the flow depend on the length of the heater and that longer heaters lead to lower average Nusselt numbers thereby extending the predictions of [13] to the geometry of an immersed heater.…”