Critical Heat Flux Measurement and Model for Refrigerant-123 Under Stabilized Flow Conditions in Microchannels

2006 ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Flux Measurement ◽  
Absolute Error ◽  
Cross Sectional ◽  
Boiling Process ◽  
Parallel Microchannels

The present work is aimed toward understanding the effect of flow boiling stability on critical heat flux (CHF) with Refrigerant-123 (R-123) in microchannel passages. Experimental data and theoretical model to predict the CHF are the focus of this work. The experimental test section has six parallel microchannels with each having a cross sectional area of 1054 × 157 μm2. The effect of flow instabilities in microchannels is investigated using flow restrictors at the inlet of each microchannel to stabilize the flow boiling process and avoid the backflow phenomena. This technique resulted in successfully stabilizing the flow boiling process as seen through a high-speed camera. The present CHF result is found to correlate to mean absolute error (MAE) of 24.1% with a macroscale empirical equation by Katto [13]. A theoretical analysis of flow boiling phenomena revealed that the ratio of evaporation momentum to surface tension forces is an important parameter. For the first time, a theoretical CHF model is proposed using these underlying forces to represent CHF mechanism in microchannels, and its correlation agrees with the experimental data with MAE of 2.5%.

Experimental Study and Model on Critical Heat Flux of Refrigerant-123 and Water in Microchannels

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Flow Instabilities ◽  
Cross Sectional ◽  
Rectangular Channels ◽  
Boiling Process ◽  
Parallel Microchannels ◽  
Surface Tension Forces

The present work is aimed toward understanding the effect of flow boiling stability on critical heat flux (CHF) with Refrigerant 123 (R-123) and water in microchannel passages. Experimental data and theoretical model to predict the CHF are the focus of this work. The experimental test section has six parallel microchannels, with each having a cross-sectional area of 1054×157μm2. The effect of flow instabilities in microchannels is investigated using flow restrictors at the inlet of each microchannel to stabilize the flow boiling process and avoid the backflow phenomena. This technique resulted in successfully stabilizing the flow boiling process. The present experimental CHF results are found to correlate best with existing correlations to overall mean absolute errors (MAEs) of 33.9% and 14.3% with R-123 and water, respectively, when using a macroscale rectangular equation by Katto (1981, “General Features of CHF of Forced Convection Boiling in Uniformly Heated Rectangular Channels,” Int. J. Heat Mass Transfer, 24, pp. 1413–1419). A theoretical analysis of flow boiling phenomena revealed that the ratio of evaporation momentum to surface tension forces is an important parameter. A theoretical CHF model is proposed using these underlying forces to represent CHF mechanism in microchannels, and its correlation agrees with the experimental data with MAE of 2.5%.

Effect of Cross-Sectional Perturbation on Critical Heat Flux Criteria in Microchannels

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Mark J. Miner ◽  
Patrick E. Phelan
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Phase Velocity ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Channel Diameter ◽  
Cross Sectional ◽  
Growing Body ◽  
Circular Microchannel ◽  
Expanding Channel

A variety of predictive correlations for critical heat flux (CHF) are examined in light of the growing body of work exploring enhanced flow boiling CHF via cross-sectional expansion. The analysis considers the effect of a small perturbation of the diameter of a circular microchannel on the predictions made by the selected criteria, and seeks to demonstrate an optimum rate of expansion. It is demonstrated that a nonzero diameter expansion necessarily improves performance under several criteria for critical heat flux, and an optimum expansion rate exists for many of these criteria. CHF relations are seen to follow a few distinct types, and those relations which contemplate effects which may directly influence CHF, such as pressure and phase velocity, tend to better reflect the experimentally demonstrated effect of the expanding channel diameter on CHF. Experimental data are examined from several investigators, including the authors' group, and the validity of both the criteria and the analysis is compared to the data.

Flow Boiling of R134a in Circular Microtubes—Part II: Study of Critical Heat Flux Condition

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Saptarshi Basu ◽  
Sidy Ndao ◽  
Gregory J. Michna ◽  
Yoav Peles ◽  
Michael K. Jensen
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Heat Flux ◽  
Flow Pattern ◽  
Flow Regime ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Absolute Error ◽  
Two Phase

A detailed experimental study was carried out on the critical heat flux (CHF) condition for flow boiling of R134a in single circular microtubes. The test sections had inner diameters (ID) of 0.50 mm, 0.96 mm, and 1.60 mm. Experiments were conducted over a large range of mass flux, inlet subcooling, saturation pressure, and vapor quality. CHF occurred under saturated conditions at high qualities and increased with increasing mass fluxes, tube diameters, and inlet subcoolings. CHF generally, but not always, decreases with increasing saturation pressures and vapor qualities. The experimental data were mapped to the flow pattern maps developed by Hasan [2005, “Two-Phase Flow Regime Transitions in Microchannels: A Comparative Experimental Study,” Nanoscale Microscale Thermophys. Eng., 9, pp. 165–182] and Revellin and Thome [2007, “A New Type of Diabatic Flow Pattern Map for Boiling Heat Transfer in Microchannels,” J. Micromech. Microeng., 17, pp. 788–796]. Based on these maps, CHF mainly occurred in the annular flow regime in the larger tubes. The flow pattern for the 0.50 mm ID tube was not conclusively identified. Four correlations—the Bowring correlation, the Katto-Ohno correlation, the Thome correlation, and the Zhang correlation—were used to predict the experimental data. The correlations predicted the correct experimental trend, but the mean absolute error (MAE) was high (>15%) A new correlation was developed to fit the experimental data with a MAE of 10%.

Experimental Study on Saturated Flow Boiling Critical Heat Flux in Microchannels

2006 ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Quantitative Information ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Saturated Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Cartridge Heater

The saturated flow boiling critical heat flux in microchannels is investigated using water as the working fluid. The experimental test section has six parallel microchannels with each having a cross sectional area of 1054 × 157 micrometers. The mass flow rate, inlet temperature of the working fluids, and the electric current supplied to the resistive cartridge heater are controlled to provide quantitative information near the CHF condition in microchannels. The trends in present CHF with mass flux and quality are similar to those obtained by Qu and Mudawar [1] and earlier investigators.

scholarly journals A Study of Critical Heat Flux During Flow Boiling in Microchannel Heat Sinks

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Tailian Chen ◽  
Suresh V. Garimella
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Rate ◽  
Heat Input ◽  
Heat Sink ◽  
Flow Boiling ◽  
Strong Dependence ◽  
Heat Fluxes ◽  
Abrupt Decrease ◽  
Parallel Microchannels

The cooling capacity of two-phase transport in microchannels is limited by the occurrence of critical heat flux (CHF). Due to the nature of the phenomenon, it is challenging to obtain reliable CHF data without causing damage to the device under test. In this work, the critical heat fluxes for flow boiling of FC-77 in a silicon thermal test die containing 60 parallel microchannels were measured at five total flow rates through the microchannels in the range of 20–80 ml/min. CHF is caused by dryout at the wall near the exit of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The bubbles pushed back into the inlet plenum agglomerate; the resulting flow blockage is a likely cause for the occurrence of CHF which is marked by an abrupt increase in wall temperature near the exit and an abrupt decrease in pressure drop across the microchannels. A database of 49 data points obtained from five experiments in four independent studies with water, R-113, and FC-77 as coolants was compiled and analyzed. It is found that the CHF has a strong dependence on the coolant, the flow rate, and the area upon which the heat flux definition is based. However, at a given flow rate, the critical heat input (total heat transfer rate to the coolant when CHF occurs) depends only on the coolant and has minimal dependence on the details of the microchannel heat sink (channel size, number of channels, substrate material, and base area). The critical heat input for flow boiling in multiple parallel microchannels follows a well-defined trend with the product of mass flow rate and latent heat of vaporization. A power-law correlation is proposed which offers a simple, yet accurate method for predicting the CHF. The thermodynamic exit quality at CHF is also analyzed and discussed to provide insights into the CHF phenomenon in a heat sink containing multiple parallel microchannels.

On the Nature of Critical Heat Flux in Microchannels

2005 ◽  
Vol 127 (1) ◽  
pp. 101-107 ◽  
Author(s):  
A. E. Bergles ◽  
S. G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Flow Distribution ◽  
High Heat ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Clear Understanding ◽  
Wide Range ◽  
Parallel Microchannels

The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

Flow boiling in microgravity: Part 2 – Critical heat flux interfacial behavior, experimental data, and model

2015 ◽  
Vol 81 ◽  
pp. 721-736 ◽  
Author(s):  
Christopher Konishi ◽  
Hyoungsoon Lee ◽  
Issam Mudawar ◽  
Mohammad M. Hasan ◽  
Henry K. Nahra ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Interfacial Behavior

Flow Boiling in a Parallel Strip Fin Heat Sink With Nonuniform Heat Flux Conditions

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Kexian Ren ◽  
Ze Miao ◽  
Bo Yang ◽  
Tongzhi Yang ◽  
Weixing Yuan
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Thermal Load ◽  
High Speed ◽  
Flow Boiling ◽  
Uniform Heat Flux ◽  
High Speed Camera ◽  
Pressure Drops ◽  
Boiling Process ◽  
Parallel Strip

Abstract This study investigates the thermal performance of a parallel strip fin heat sink (PSFHS) under various heat flux conditions at a flowrate of 100 ml/min, including uniform heat flux and nonuniform heat flux. The heat sink consists of 150 fins with a width of 1 mm, a height of 5.5 mm, and a pitch of 1 mm and has a Z-type inlet/outlet arrangement. Nine separate heaters offer thermal load to the heat sink in order to provide a uniform or nonuniform heat flux. The flow boiling process is captured by a high-speed camera. The temperatures of the heaters have been measured under the uniform and nonuniform heat flux conditions. In addition, the pressure drops inside the heat sink are also obtained. A minichannel heat sink (MCHS) with the same channel dimensions and inlet/outlet configuration is tested too. A comparison between MCHS and PSFHS is discussed in detail, which helps to understand the flow boiling characteristic in PSFHS.

Prediction of critical heat flux in flow boiling process under the effect of different operating parameters

2020 ◽  
pp. 095765092096223
Author(s):  
Ehsan Abedini ◽  
Mohammad Behboudi ◽  
Arash Mohammadi Karachi ◽  
Reza Hamidi Jahromi ◽  
Kianoush DolatiAsl
Keyword(s):  
Heat Flux ◽  
Surface Roughness ◽  
Critical Heat Flux ◽  
Wall Temperature ◽  
Flow Boiling ◽  
Turbulence Models ◽  
Fluid Flows ◽  
Channel Length ◽  
Heated Wall ◽  
Boiling Process

In the present study numerical simulation of flow boiling process has been conducted for evaluation of critical heat flux conditions under the effect of different parameters (mass flux, heat flux, channel length and surface roughness). Comparison between the results of the present study and previous researches were done. The comparison shows a good agreement between the present study and previous researches. The three different turbulence models (k-epsilon, k-omega and Reynolds Stress) are considered for simulation of boiling heat transfer and CHF phenomenon. The highest accuracy of simulation is obtained by k-epsilon model. The results express that the wall temperature value of tube with adiabatic and heated boundary conditions for first and second half of the tube is lower than the wall temperature when the fluid flows only in the heated wall section. Reduction of velocity value also leads to reduction of maximum wall temperature value and CHF value. Decreasing Roughness value as an effective parameter leads to an increase in wall temperature. Maximum value of the wall temperature, after CHF point, also increases with increase in heat flux value. CHF depends on the surface roughness and rises with increasing roughness value.

Sign in / Sign up

Export Citation Format

Share Document