Experimental study of heat transfer in liquid-nitrogen cooling of the surface of superconducting YBa2Cu3O7 ceramic. 2. Burnout in nucleate boiling

1990 ◽  
Vol 59 (5) ◽  
pp. 1401-1404
Author(s):  
V. V. Baranets ◽  
Yu. A. Kirichenko ◽  
S. M. Kozlov ◽  
S. V. Nozdrin ◽  
K. V. Rusanov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Liquid Nitrogen ◽  
Nucleate Boiling ◽  
Liquid Nitrogen Cooling

An Experimental Study on Cryogenic Spray Quenching of a Circular Metal Disk II. Chilldown Efficiency and Effects of Coating and Flow Pulsing

2021 ◽  
Author(s):  
Jun Dong ◽  
Hao Wang ◽  
Samuel Darr ◽  
Jason Hartwig ◽  
Jacob Chung
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Liquid Nitrogen ◽  
Mass Flow ◽  
Flow Rate ◽  
Continuous Flow ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Teflon Coating ◽  
Bare Surface

Abstract This is the second part of a two-part series that presents the results of liquid nitrogen spray quenching of a Stainless Steel disc. The results of continuous-flow spray chilldown of a bare surface disc are summarized first that serves as the baseline information for evaluating the effects of disc surface coating and pulse flow. We found that for continuous-flow spray chilldown of a bare surface disc, the chilldown efficiency is mainly a function of the average mass flow rate with the trend of decreasing efficiency with increasing mass flow rate. Additional experiments were performed to evaluate the enhancement of cryogenic spray quenching by three techniques: 1. Using intermittent pulse sprays on SS bare surface, 2. Coating the SS surface with a layer of low thermal conductivity Teflon film, and 3. Spraying liquid nitrogen intermittently on the coated SS surface. In general, the results indicate that all three methods effectively produced higher spray thermal efficiencies and reduced liquid nitrogen mass consumption. However, it was also found that the Teflon coating was more effective than the flow pulsing due to that the Teflon coating induced a large surface temperature drop at the beginning of the chilldown that allowed the quenching to move quickly from poor heat transfer film boiling to efficient heat transfer transition and nucleate boiling regimes. This quick transition shortens the film boiling period, thus facilitates the switch to much higher heat transfer transition boiling and nucleate boiling periods earlier to complete the chilldown process faster.

Two-Phase Pipe Quenching Correlations for Liquid Nitrogen and Liquid Hydrogen

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
S. R. Darr ◽  
J. W. Hartwig ◽  
J. Dong ◽  
H. Wang ◽  
A. K. Majumdar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Nitrogen ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Liquid Hydrogen ◽  
Two Phase ◽  
Cryogenic Flow ◽  
Two Phase Heat Transfer

Recently, two-phase cryogenic flow boiling data in liquid nitrogen (LN2) and liquid hydrogen (LH2) were compared to the most popular two-phase correlations, as well as correlations used in two of the most widely used commercially available thermal/fluid design codes in Hartwig et al. (2016, “Assessment of Existing Two Phase Heat Transfer Coefficient and Critical Heat Flux on Cryogenic Flow Boiling Quenching Experiments,” Int. J. Heat Mass Transfer, 93, pp. 441–463). Results uncovered that the correlations performed poorly, with predictions significantly higher than the data. Disparity is primarily due to the fact that most two-phase correlations are based on room temperature fluids, and for the heating configuration, not the quenching configuration. The penalty for such poor predictive tools is higher margin, safety factor, and cost. Before control algorithms for cryogenic transfer systems can be implemented, it is first required to develop a set of low-error, fundamental two-phase heat transfer correlations that match available cryogenic data. This paper presents the background for developing a new set of quenching/chilldown correlations for cryogenic pipe flow on thin, shorter lines, including the results of an exhaustive literature review of 61 sources. New correlations are presented which are based on the consolidated database of 79,915 quenching points for a 1.27 cm diameter line, covering a wide range of inlet subcooling, mass flux, pressure, equilibrium quality, flow direction, and even gravity level. Functional forms are presented for LN2 and LH2 chilldown correlations, including film, transition, and nucleate boiling, critical heat flux, and the Leidenfrost point.

Experimental study of the effect of liquid nitrogen cooling on rock pore structure

2014 ◽  
Vol 21 ◽  
pp. 507-517 ◽  
Author(s):  
Chengzheng Cai ◽  
Gensheng Li ◽  
Zhongwei Huang ◽  
Zhonghou Shen ◽  
Shouceng Tian ◽  
...  
Keyword(s):  
Experimental Study ◽  
Pore Structure ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Cooling

Experimental Study of Nucleate Boiling Heat Transfer Using Enhanced Space-Confined Structures

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Xuehu Ma ◽  
Chunjian Yu ◽  
Zhong Lan ◽  
Donghui Wang ◽  
Tao Bai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Speed ◽  
Bubble Diameter ◽  
Nucleate Boiling ◽  
Large Area ◽  
Nucleation Sites ◽  
Nucleate Boiling Heat Transfer ◽  
Narrow Space ◽  
High Superheat

For narrow space boiling, it is difficult to release bubbles from the narrow space, especially on a large-area surface. To solve this problem, a new structure is designed in the present paper. An experimental study of pool boiling on the novel copper enhanced structure, with the separate ordinary confined spaces and the open channels between them, was conducted with water and ethanol. High-speed visualizations are performed to elucidate the bubble flow. The results show that the boiling performance of both water and ethanol can be enhanced effectively. The visualizations indicated that most active nucleation sites emerged in the confined channels and rarely appeared at the bare surfaces not covered by enhanced structures even at high superheat. The bubble diameter, the bubble departure frequency, and the numbers of nucleation sites are obtained using statistical methods. The results suggest that the magnitudes of bubble diameter of water are almost the same on the smooth and enhanced surfaces. The amount of nucleation sites on the enhanced surfaces is remarkably increased, indicating its key role in the boiling enhancement of water. The bubble departure frequency is increased on one of the enhanced surfaces while not increased on another, showing that it is also a significant factor for heat transfer enhancement under certain conditions. While for ethanol, all the three parameters are increased on the enhanced surfaces.

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