Transient Heat Transfer During Cryogenic Chilldown

Abstract

Cryogenic fluids have found many practical applications in today’s world, from cooling superconducting magnets to fueling launch vehicles. In many of these applications the cryogenic fluid is initially introduced into piping systems that are in excess of 150 degrees Kelvin higher than the fluid. This leads to voracious evaporation of the fluid and significant pressure fluctuations, which is accompanied by thermal contraction of system components. This process is known as chilldown, and although it was first investigated more than 4 decades ago, very little data are available on the momentum and energy transport during this transient process. Consequently, the development of predictive models for the pressure drop and heat transfer coefficient has been hampered. In order to address this deficiency, an experimental facility has been constructed that enables the flow structure to be observed while temperatures and pressures at various locations are measured. This study focuses on the inverse numerical procedure used to extract the transient heat transfer coefficient information from the data collected; this information is then used to evaluate the performance of various correlations for heat transfer coefficient in the flow boiling regime. The method developed utilizes flow structure information and temperature measurements, in conjunction with numerical computations for the temperature field within the tube wall, to calculate the heat transfer coefficient. This approach allows the transition point between the film boiling regime and the nucleate boiling regime to be determined, and it also elucidates the variation of the heat transfer coefficient along the circumference of a horizontal tube, with the heat transfer on upper portion being significantly smaller than that at the bottom.

Cryogenic Chilldown Model for Stratified Flow Inside a Pipe

“…A new film boiling heat transfer coefficient for cryogenic chilldown has been developed using first principles and incorporating the stratified flow structure. The new film boiling coefficient is also successfully implemented by Jackson et al [36]. The existing nucleate boiling heat transfer correlations may not work well for cryogenic conditions.…”

Development of Methods for Heat Transfer Enhancement During Nitrogen Boiling to Ensure Stabilization of HTS Devices

“…Study [172] focuses on the inverse numerical procedure to extract the transient HTC information from collected data; this information is then used for evaluation of various correlations for the HTC in the flow boiling regime. The method developed in [172] utilizes flow structure information and temperature measurements in conjunction with numerical computations for the temperature field within the tube wall to calculate the HTC.…”

“…Study [172] focuses on the inverse numerical procedure to extract the transient HTC information from collected data; this information is then used for evaluation of various correlations for the HTC in the flow boiling regime. The method developed in [172] utilizes flow structure information and temperature measurements in conjunction with numerical computations for the temperature field within the tube wall to calculate the HTC. This approach enables determination of the transition point between the film boiling regime and the nucleate boiling regime and elucidates the variation of the HTC along the circumference of a horizontal tube, the heat transfer on the upper portion being significantly smaller than that at the bottom.…”

Development of Cryo Probe for Medical Application

“…Cryoablation is done with a long flexible metal tube called cryoprobe [3] . Aim is to achieve a temperature of -80 to -100°C at the tip of probe.…”