Critical Heat Flux for Convective Boiling in Mini-Tube due to Power Transient

2017 ◽  
Author(s):  
Makoto Shibahara ◽  
Katsuya Fukuda ◽  
Qiusheng Liu ◽  
Koichi Hata
Keyword(s):  
Heat Flux ◽  
Flow Velocity ◽  
Critical Heat Flux ◽  
Heat Generation ◽  
Heated Surface ◽  
Generation Rate ◽  
Experimental Result ◽  
Transient Condition ◽  
Heat Generation Rate ◽  
Convective Boiling

Critical heat flux (CHF) of convective boiling in a mini-tube due to power transient was measured. A platinum tube with an inner diameter of 1.0 mm was heated exponentially by a direct current power supply as Joule heating. The heated length of the platinum tube was 40.9 mm. The platinum tube was mounted vertically in the water-loop apparatus which consisted of a circulating pump, a pre-heater, a flow mater, a pressurizer, a cooler and a test section. The deionized water was pressurized by the pressurizer up to approximately 800 kPa to measure CHFs at the high subcooling. The upward flow velocity in the platinum tube was ranged from 5 to 11 m/s. The inlet subcooling was ranged from 92 to 117 K. The heat generation rate was controlled with exponential functions. The e-folding time of the heat generation rate was ranged from 30 ms to 18 s. As an experimental result, it was found that the CHFs increased with increasing the flow velocity and the inlet subcooling. The CHF also increased with decreasing the e-folding time of the heat generation rate. Since the heat generation rate of the platinum tube increased rapidly under the power transient condition, it was considered that the heat flux of the platinum tube increased until the vapor blanket covered the heated surface of the platinum tube.

scholarly journals A Simplified Calculation Method of Heat Source Model for Induction Heating

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2938 ◽  
Author(s):  
Hongbao Dong ◽  
Yao Zhao ◽  
Hua Yuan ◽  
Xiaocai Hu ◽  
Zhen Yang
Keyword(s):  
Heat Flux ◽  
Temperature Field ◽  
Heat Source ◽  
Heat Generation ◽  
Induction Heating ◽  
Generation Rate ◽  
Heat Generation Rate ◽  
Line Heating ◽  
Computation Efficiency ◽  
Computation Process

Line heating is used in forming the complex curve plates of ships, and this process is becoming integrated into automated tools. Induction heating equipment has become commonly used in automatic line heating. When applying automated equipment, it is necessary to calculate the relationship between the heating parameters and the temperature field. Numerical methods are primarily used to accomplish the calculations for induction heating. This computation process requires repeated iterations to obtain a stable heat generation rate. Once the heat generation rate changes significantly, a recalculation takes place. Due to the relative position of the coil and plate changes during heating, the grid needs to be frequently re-divided during computation, which dramatically increases the total computation time. In this paper, through an analysis of the computation process for induction heating, the root node that restricts the computation efficiency in the conventional electromagnetic-thermal computation process was found. A method that uses a Gaussian function to represent the heat flux was proposed to replace the electromagnetic computation. The heat flux is the input for calculating the temperature field, thus avoiding the calculation of the electromagnetic analysis during induction heating. Besides, an equivalence relationship for multi-coil was proposed in this paper. By comparing the results of the experiment and the numerical method, the proposed heat source model’s effectiveness was verified.

Heat generation rate measurement in a Li-ion cell at large C-rates through temperature and heat flux measurements

2015 ◽  
Vol 285 ◽  
pp. 266-273 ◽  
Author(s):  
S.J. Drake ◽  
M. Martin ◽  
D.A. Wetz ◽  
J.K. Ostanek ◽  
S.P. Miller ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Generation ◽  
Generation Rate ◽  
Rate Measurement ◽  
Heat Generation Rate ◽  
Flux Measurements ◽  
Li Ion

Critical Heat Flux During Natural Convective Boiling in Vertical Rectangular Channels Submerged in Saturated Liquid

1982 ◽  
Vol 104 (2) ◽  
pp. 300-303 ◽  
Author(s):  
M. Monde ◽  
H. Kusuda ◽  
H. Uehara
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Atmospheric Pressure ◽  
Heated Surface ◽  
Saturated Liquid ◽  
Convective Boiling ◽  
Flux Data ◽  
Rectangular Channels ◽  
Generalized Correlation

An experimental study of the critical heat flux has been carried out for natural convective boiling at atmospheric pressure in vertical rectangular channels. Experiments in four kinds of test liquids (water, ethanol, freon 113, and benzene) have been made for the ratio l/s less than 120, in which l is the length of the heated surface and s is the width of the channels. A generalized correlation for the critical heat-flux data in the four test liquids is evolved.

scholarly journals Predicting Critical Heat Flux With Multiphase CFD: 4 Years in the Making

2017 ◽  
Author(s):  
Emilio Baglietto ◽  
Etienne Demarly ◽  
Ravikishore Kommajosyula
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Heated Surface ◽  
Force Balance ◽  
Modeling Framework ◽  
Lift Off ◽  
Limiting Condition

Advancement in the experimental techniques have brought new insights into the microscale boiling phenomena, and provide the base for a new physical interpretation of flow boiling heat transfer. A new modeling framework in Computational Fluid Dynamics has been assembled at MIT, and aims at introducing all necessary mechanisms, and explicitly tracks: (1) the size and dynamics of the bubbles on the surface; (2) the amount of microlayer and dry area under each bubble; (3) the amount of surface area influenced by sliding bubbles; (4) the quenching of the boiling surface following a bubble departure and (5) the statistical bubble interaction on the surface. The preliminary assessment of the new framework is used to further extend the portability of the model through an improved formulation of the force balance models for bubble departure and lift-off. Starting from this improved representation at the wall, the work concentrates on the bubble dynamics and dry spot quantification on the heated surface, which governs the Critical Heat Flux (CHF) limit. A new proposition is brought forward, where Critical Heat Flux is a natural limiting condition for the heat flux partitioning on the boiling surface. The first principle based CHF is qualitatively demonstrated, and has the potential to deliver a radically new simulation technique to support the design of advanced heat transfer systems.

A novel heat generation acquisition method of cylindrical battery based on core and surface temperature measurements

2021 ◽  
pp. 1-17
Author(s):  
Xiaoli Yu ◽  
Qichao Wu ◽  
Rui Huang ◽  
Xiaoping Chen
Keyword(s):  
Surface Temperature ◽  
Heat Generation ◽  
Discharge Rate ◽  
Total Heat ◽  
Temperature Measurements ◽  
Generation Rate ◽  
Air Cooling ◽  
Heat Generation Rate ◽  
Environmental Chamber ◽  
Average Heat

Abstract Heat generation measurements of the lithium-ion battery are crucial for the design of the battery thermal management system. Most previous work uses the accelerating rate calorimeter (ARC) to test heat generation of batteries. However, utilizing ARC can only obtain heat generation of the battery operating under the adiabatic condition, deviating from common operation scenarios with heat dissipation. Besides, using ARC is difficult to measure heat generation of the high-rate operating battery because the battery temperature easily exceeds the maximum safety limit. To address these problems, we propose a novel method to obtain heat generation of cylindrical battery based on core and surface temperature measurements and select the 21700 cylindrical battery as the research object. Based on the method, total heat generation at 1C discharge rate under the natural convection air cooling condition in the environmental chamber is about 3.2 kJ, and the average heat generation rate is about 0.9 W. While these two results measured by ARC are about 2.2 kJ and 0.6 W. This gap also reflects that different battery temperature histories have significant impacts on heat generation. In addition, using our approach, total heat generation at 2C discharge rate measured in the environmental chamber is about 5.0 kJ, with the average heat generation rate being about 2.8 W. Heat generation results obtained by our method are approximate to the actual battery operation and have advantages in future applications.

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