Consolidated method to predicting pressure drop and heat transfer coefficient for both subcooled and saturated flow boiling in micro-channel heat sinks

2012 ◽  
Vol 55 (13-14) ◽  
pp. 3720-3731 ◽  
Author(s):  
Sung-Min Kim ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Micro Channel ◽  
Saturated Flow

Microchannel Size Effects on Two-Phase Local Heat Transfer and Pressure Drop in Silicon Microchannel Heat Sinks With a Dielectric Fluid

2007 ◽  
Author(s):  
Tannaz Harirchian ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
The Heat Transfer Coefficient

Two-phase heat transfer in microchannels can support very high heat fluxes for use in high-performance electronics-cooling applications. However, the effects of microchannel cross-sectional dimensions on the heat transfer coefficient and pressure drop have not been investigated extensively. In the present work, experiments are conducted to investigate the local flow boiling heat transfer in microchannel heat sinks. The effect of channel size on the heat transfer coefficient and pressure drop is studied for mass fluxes ranging from 250 to 1600 kg/m2s. The test sections consist of parallel microchannels with nominal widths of 100, 250, 400, 700, and 1000 μm, all with a depth of 400 μm, cut into 12.7 mm × 12.7 mm silicon substrates. Twenty-five microheaters embedded in the substrate allow local control of the imposed heat flux, while twenty-five temperature microsensors integrated into the back of the substrates enable local measurements of temperature. The dielectric fluid Fluorinert FC-77 is used as the working fluid. The results of this study serve to quantify the effectiveness of microchannel heat transport while simultaneously assessing the pressure drop trade-offs.

Flow Boiling Heat Transfer in a Silicon Microchannel Heat Sink Using Liquid Crystal Thermography

2008 ◽  
Author(s):  
Ayman Megahed ◽  
Ibrahim Hassan ◽  
Tariq Ahmad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Microchannel Heat Sink

The present study focuses on the experimental investigation of boiling heat transfer characteristics and pressure drop in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 295 μm, width of 254 μm, and a length of 16 mm. Un-encapsulated Thermochromic liquid Crystals (TLC) are used in the present work to enable nonintrusive and high spatial resolution temperature measurements. This measuring technique is used to provide accurate full and local surface-temperature and heat transfer coefficient measurements. Experiments are carried out for mass velocities ranging between 290 to 457 kg/m2.s and heat fluxes from 6.04 to 13.06 W/cm2 using FC-72 as the working fluid. Experimental results show that the pressure drop increases as the exit quality and the flow rate increase. High values of heat transfer coefficient can be obtained at low exit quality (xe < 0.2). However, the heat transfer coefficient decreases sharply and remains almost constant as the quality increases for an exit quality higher than 0.2.

Optimization Under Uncertainty of Manifold Microchannel Heat Sinks

2012 ◽  
Author(s):  
Suchismita Sarangi ◽  
Karthik K. Bodla ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Sinks ◽  
Optimization Under Uncertainty ◽  
Microchannel Heat Sink ◽  
Probabilistic Optimization ◽  
Manifold Microchannel

Conventional microchannel heat sinks provide good heat dissipation capability but are associated with high pressure drop and corresponding pumping power. The use of a manifold system that distributes the flow into the microchannels through multiple, alternating inlet and outlet pairs is investigated here. This manifold arrangement greatly reduces the pressure drop incurred due to the smaller flow paths, while simultaneously increasing the heat transfer coefficient by tripping the thermal boundary layers. A three-dimensional numerical model is developed and validated, to study the effect of various geometric parameters on the performance of the manifold microchannel heat sink. Apart from a deterministic analysis, a probabilistic optimization study is also performed. In the presence of uncertainties in the geometric and operating parameters of the system, this probabilistic optimization approach yields an optimal design that is also robust and reliable. Uncertainty-based optimization also yields auxiliary information regarding local and global sensitivities and helps identify the input parameters to which outputs are most sensitive. This information can be used to design improved experiments targeted at the most sensitive inputs. Optimization under uncertainty also provides a quantitative estimate of the allowable uncertainty in input parameters for an acceptable uncertainty in the relevant output parameters. The optimal geometric design parameters with uncertainties that maximize heat transfer coefficient while minimizing pressure drop for fixed input conditions are identified for a manifold microchannel heat sink. A comparison between the deterministic and probabilistic optimization results is also presented.

Experimental Study on Flow Boiling of HFC134a in a Multi-Port Extruded Tube

2004 ◽  
Author(s):  
Ken Kuwahara ◽  
Shigeru Koyama ◽  
Kengo Kazari
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Large Diameter ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inlet Temperature

In the present study, the local heat transfer and pressure drop characteristics are investigated experimentally for the flow boiling of refrigerant HFC134a in a multi-port extruded tube of 1.06mm in hydraulic diameter. The test tube is 865mm in total length made of aluminum. The pressure drop is measured at an interval of 191 mm, and the local heat transfer coefficient is measured in every subsection of 75mm in effective heating length. Experimental ranges are as follows: the mass velocity of G = 100–700 kg/m2s, the inlet temperature of Tin = 5.9–11.4 °C and inlet pressure of about 0.5 MPa. The data of pressure drop are compared with a few previous correlations for small diameter tubes, and the correlations can predict the data relatively good agreement. The data of heat transfer coefficient is compared with the correlations of Yu et al. proposed for relatively large diameter tubes. It is found that there are some differences about two phase multiplier factor of convective heat transfer between the circular channel and rectangular channel.

scholarly journals Experimental and Simulation Study of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (4) ◽  
pp. 1255
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xiaohua Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Outlet Temperature ◽  
Transfer Performance ◽  
Micro Channel ◽  
Heat Transfer Capacity ◽  
The Heat Transfer Coefficient

This paper mainly studies the heat transfer performance of backplane micro-channel heat pipes by establishing a steady-state numerical model. Compared with the experimental data, the heat transfer characteristics under different structure parameters and operating parameters were studied, and the change of heat transfer coefficient inside the system, the air outlet temperature of the back plate and the influence of different environmental factors on the heat transfer performance of the system were analyzed. The results show that the overall error between simulation results and experimental data is less than 10%. In the range of the optimal filling rate (FR = 64.40%–73.60%), the outlet temperature at the lowest point and the highest point of the evaporation section is 22.46 °C and 19.60 °C, the temperature difference does not exceed 3 °C, and the distribution gradient in vertical height is small and the air outlet temperature is uniform. The heat transfer coefficient between the evaporator and the condenser is larger than the heat transfer coefficient under the conditions of low and high liquid charge rate. It increases gradually along the flow direction, and decreases gradually with the flow rate of the condenser. When the width of the flat tube of the evaporator increases from 20 mm to 28 mm, the internal pressure drop of the evaporator decreases by 45.83% and the heat exchange increases by 18.34%. When the number of evaporator slices increases from 16 to 24, the heat transfer increases first and then decreases, with an overall decrease of 2.86% and an increase of 87.67% in the internal pressure drop of the evaporator. The inclination angle of the corrugation changes from 30° to 60°, and the heat transfer capacity and pressure drop increase. After the inclination angle is greater than 60°, the heat transfer capacity and resistance decrease. The results are of great significance to system optimization design and engineering practical application.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2004 ◽  
Vol 126 (3) ◽  
pp. 288-300 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406×2.032mm2 cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Features unique to two-phase micro-channel flow were identified and employed to validate key assumptions of an annular flow boiling model that was previously developed to predict pressure drop and heat transfer in two-phase micro-channel heat sinks. This earlier model was modified based on new findings from the adiabatic two-phase flow study. The modified model shows good agreement with experimental data for water-cooled heat sinks.

Finned Metal Foam Heat Sinks for Electronics Cooling in Forced Convection

2002 ◽  
Vol 124 (3) ◽  
pp. 155-163 ◽  
Author(s):  
A. Bhattacharya ◽  
R. L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Metal Foam ◽  
Experimental Results ◽  
Heat Sinks ◽  
The Heat Transfer Coefficient

In this paper, we present recent experimental results on forced convective heat transfer in novel finned metal foam heat sinks. Experiments were conducted on aluminum foams of 90 percent porosity and pore size corresponding to 5 PPI (200 PPM) and 20 PPI (800 PPM) with one, two, four and six fins, where PPI (PPM) stands for pores per inch (pores per meter) and is a measure of the pore density of the porous medium. All of these heat sinks were fabricated in-house. The forced convection results show that heat transfer is significantly enhanced when fins are incorporated in metal foam. The heat transfer coefficient increases with increase in the number of fins until adding more fins retards heat transfer due to interference of thermal boundary layers. For the 20 PPI samples, this maximum was reached for four fins. For the 5 PPI heat sinks, the trends were found to be similar to those for the 20 PPI heat sinks. However, due to larger pore sizes, the pressure drop encountered is much lower at a particular air velocity. As a result, for a given pressure drop, the heat transfer coefficient is higher compared to the 20 PPI heat sink. For example, at a Δp of 105 Pa, the heat transfer coefficients were found to be 1169W/m2-K and 995W/m2-K for the 5 PPI and 20 PPI 4-finned heat sinks, respectively. The finned metal foam heat sinks outperform the longitudinal finned and normal metal foam heat sinks by a factor between 1.5 and 2, respectively. Finally, an analytical expression is formulated based on flow through an open channel and incorporating the effects of thermal dispersion and interfacial heat transfer between the solid and fluid phases of the porous medium. The agreement of the proposed relation with the experimental results is promising.

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