Visual Observation of Circular Water Jet Impingement Boiling on Stationary Hot Steel Plate

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Sangho Sohn ◽  
Jaebum Park

The time-and space-resolved water jet impingement heat transfer on stationary hot steel plate was measured by a novel experimental technique that has a function of high-temperature heat flux gauge. The simultaneous visual observation was helpful to understand the complex heat transfer regimes occurring on a stationary hot steel plate cooled from 900°C by a circular water jet. The heat transfer regimes adjacent to a circular water jet impinging on a hot steel plate were known as to be classified into 5 distinct regimes; (I) single phase forced convection, (II) nucleate and transition boiling, (III) forced convection film boiling, (IV) agglomerated pools, (V) radiation and natural convection to surroundings. The observed images of water jet impingement boiling were well agreed with the measured cooling curve and boiling curve, so this study can provide the benchmark data for validating the 5 distinct regimes.

Author(s):  
Cuicui Liu ◽  
Zeyi Jiang ◽  
Xinxin Zhang ◽  
Qiang Ma ◽  
Yusheng Sun

Mathematical model combining theoretical analysis approach and differential numerical solving techniques has been set up to predict the free surface water jet impingement heat transfer. Heat transfer properties are obtained and validated by comparison with experiments. The characteristic of Nu-r/d distribution is discussed and the effect of nozzle diameter is analyzed. In addition, nozzle arrangements are studied for water jet equipment designation purpose. The results show that: Reynolds number is the dominate parameter in Nu-r/d distribution and area-averaged Nusselt number increases with increasing nozzle diameter. The best heat transfer effect appears when the aspect ratio of rectangular surface equals to 1. Fewer nozzles and bigger single impinged area could get larger Nusselt number under a given total water flow rate and given total impinged area. At a constant flow rate, larger nozzle diameter and smaller Reynolds number present a larger Nusselt number.


Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop

Abstract Nanoliquid impingement heat transfer with phase change material (PCM) installed radial system is considered. Study is performed by using finite element method for various values of Reynolds numbers (100 ≤ Re ≤ 300), height of PCM (0.25H ≤ hpcm = 0.7H ≤ 0.75H) and plate spacing (0.15H ≤ hpcm = 0.7H ≤ 0.40H). Different configurations with using water, nanoliquid and nanoliquid+PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM while best performance is achieved with nanoliquid and PCM installed configuration. At Re=100 and Re=300, heat transfer improvements of 26% and 25.5% are achieved with nanoliquid+PCM system as compared to water without PCM. Height of the PCM layer also influences the heat transfer dynamic behavior while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM height while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation.


2017 ◽  
Vol 30 (2) ◽  
pp. 586-594 ◽  
Author(s):  
Ying Zhou ◽  
Guiping Lin ◽  
Xueqin Bu ◽  
Lizhan Bai ◽  
Dongsheng Wen

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