scholarly journals Measurement of heat flux and heat transfer coefficient during continuous cryogen spray cooling for laser dermatologic surgery

2001 ◽  
Vol 7 (6) ◽  
pp. 1013-1021 ◽  
Author(s):  
G. Aguilar ◽  
W. Verkruysse ◽  
B. Majaron ◽  
L.O. Svaasand ◽  
E.J. Lavernia ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Spray Cooling ◽  
Dermatologic Surgery ◽  
Cryogen Spray Cooling

Development of a General Dynamic Pressure Based Single-Phase Spray Cooling Heat Transfer Correlation

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Bahman Abbasi ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Dynamic Pressure ◽  
Local Heat ◽  
Spray Cooling ◽  
Maximum Deviation ◽  
Transfer Coefficients

One of the main challenges of spray cooling technology is the prediction of local and average heat transfer coefficients on the heater surface. It is hypothesized that the local heat transfer coefficient can be predicted from the local normal pressure produced by the spray. In this study, hollow cone, full cone, and flat fan sprays, operated at three standoff distances, five spray pressures, and two nozzle orientations, were used to identify the relation between the impingement pressure and the heat transfer coefficient in the single-phase regime. PF-5060, PAO-2, and PSF-3 were used as test fluids, resulting in Prandtl number variation between 12 and 76. A microheater array operated at constant temperature was used to measure the local heat flux. A separate test rig was used to make impingement pressure measurements for the same geometry and spray pressure. The heat flux data were then compared with the corresponding impingement pressure data to develop a pressure-based correlation for spray cooling heat transfer. The maximum deviation between the experimental data and prediction was within ±25%.

Application of Inverse Heat Conduction Method and Method of Lines in Spray Cooling of Heated Surface

2016 ◽  
Author(s):  
Ramin Soujoudi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Conduction ◽  
Transfer Coefficient ◽  
Heated Surface ◽  
Method Of Lines ◽  
Spray Cooling ◽  
Approximation Technique ◽  
Inverse Heat Conduction

This paper investigates application of Method of Lines (MOL) and Inverse Heat Conduction techniques in spray cooling process. A flat face of a heated cylinder is cooled by using a nozzle spray and using room temperature water as a cooling fluid. The numerical analysis is done using MOL to estimate exposed surface temperature, surface heat flux, and convection heat transfer coefficient [3],[4]. Since there is no exact solution to verify the approximation result, for the verification purpose and accuracy of the result, the numerical result from this study is compared to other approximation results with experimental research done by Chen-Lee and Qiao-Chandra [1]. The results illustrate that disparity between the outcome of MOL and the one generated by Chen and Lee’s raw data is very insignificant throughout the whole time domain. This discrepancy between these two estimated results proves that MOL is a very reliable approximation technique compared to other finite element methods which require a finer mesh size and significant amount of calculations[2],[5]. However, comparing the results obtained through MOL with Qiao and Chandra shows that the difference between the estimated heat transfer coefficient and estimated heat flux converges rapidly for the short times of 0 < t < 60, but as the time passes, the MOL approximation results diverge slowly until it reaches its maximum value at ninety seconds, and the variance remains almost constant for the rest of the time period.

Effects of Liquid Heat Dissipation on Heat Transfer Coefficient in Spray Cooling

2005 ◽  
Author(s):  
Shu-Ye Lei ◽  
Qiu-Min Lu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Strong Dependence ◽  
Spray Cooling ◽  
Complex Nature ◽  
Inlet Temperature ◽  
Transfer Model

The effects of the heat flux and liquid temperatures during spray cooling heat transfer were experimentally studied for non-boiling water spray cooling. The experiments show that the heat flux strongly affects the heat transfer coefficient, especially for high temperature sprays or low heat fluxes. A key effect is the heat dissipation from the liquid to the environment. The heat dissipation increases with the spray inlet temperature or the heat flux. To explain the strong dependence of the heat transfer on the heat dissipation in single phase, a spray cooling heat transfer model was suggested which includes the heat dissipation. Experimental measurements of the radial spray droplet temperature profile showed the complex nature of the heat dissipation.

scholarly journals Influence of the Refrigerant Charge on the Heat Transfer Performance for a Closed-Loop Spray Cooling System

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7588
Author(s):  
Nianyong Zhou ◽  
Hao Feng ◽  
Yixing Guo ◽  
Wenbo Liu ◽  
Haoping Peng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Cooling System ◽  
Temperature Drop ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Cooling Process

With the rapid increase of heat flux and demand for miniaturization of electronic equipment, the traditional heat conduction and convective heat transfer methods could not meet the needs. Therefore, the spray cooling experiment was carried out to obtain the basic heat transfer and cooling process. In this experiment, the spray cooling system was set up to investigate the influence of refrigerant charge on heat transfer performance in steady-state, dynamic heating, and dissipating processes. In a steady-state, the heat transfer coefficient increased with the rise of the refrigerant charge. In the dynamic dissipating process, both heat flux and heat transfer coefficient decreased rapidly after the critical heat flux, and the surface temperature drop point of each refrigerant charge was presented. The optimum refrigerant charge was provided considering the cooling parameters and the system operating performance. When the refrigerant operating pressure was 0.5 MPa, the spray cooling process presented with the higher heat flux, heat transfer coefficient, and cooling efficiency in this experiment. Meanwhile, the suitable surface temperature drop point and more gentle heat flux curves in the nucleate boiling region were obtained. The research results will contribute to the spray cooling system design, which should be operated before departure from the nucleate boiling point for avoiding cooling failure.

Pressure-Based Prediction of Single Phase Spray Cooling Heat Transfer Coefficient for Low Prandtl Number Liquids

2010 ◽  
Author(s):  
Bahman Abbasi ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Prandtl Number ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Local Heat ◽  
Spray Cooling ◽  
Maximum Deviation ◽  
Transfer Coefficients

One of the main challenges of spray cooling technology is the prediction of local and average heat transfer coefficients on the heater surface. It is hypothesized that the local heat transfer coefficient can be predicted from the local normal pressure produced by the spray. In this study, hollow cone, full cone, and flat fan sprays operated at three standoff distances, five spray pressures, and two nozzle orientations were used to identify the relation between impingement pressure and heat transfer coefficient in the single phase regime. PF-5060, PAO-2, and PSF-3 were used as test fluids, resulting in Prandtl number variation between 12 to 75. A micro-heater array operated at constant temperature was used to measure the local heat flux. A separate test rig was used to make impingement pressure measurements for the same geometry and spray pressure. The heat flux data were then compared with the corresponding impingement pressure data to develop a pressure-based correlation for spray cooling heat transfer. The maximum deviation between the experimental data and prediction was within ±25%.

scholarly journals Experimental Determination of the Heat Transfer Coefficient of Real Cooled Geometry Using Linear Regression Method

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 180
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Linear Regression ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
External Surface ◽  
Internal Surface ◽  
Regression Method ◽  
Thermal Transient

The scope of this work was to develop a technique based on the regression method and apply it on a real cooled geometry for measuring its internal heat transfer distribution. The proposed methodology is based upon an already available literature approach. For implementation of the methodology, the geometry is initially heated to a known steady temperature, followed by thermal transient, induced by injection of ambient air to its internal cooling system. During the thermal transient, external surface temperature of the geometry is recorded with the help of infrared camera. Then, a numerical procedure based upon a series of transient finite element analyses of the geometry is applied by using the obtained experimental data. The total test duration is divided into time steps, during which the heat flux on the internal surface is iteratively updated to target the measured external surface temperature. The final procured heat flux and internal surface temperature data of each time step is used to find the convective heat transfer coefficient via linear regression. This methodology is successfully implemented on three geometries: a circular duct, a blade with U-bend internal channel, and a cooled high pressure vane of real engine, with the help of a test rig developed at the University of Florence, Italy. The results are compared with the ones retrieved with similar approach available in the open literature, and the pros and cons of both methodologies are discussed in detail for each geometry.

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