Numerical Investigation of Heat Transfer Enhancement in a Microchannel With Offset Micro Pin-Fins

2010 ◽  
Author(s):  
Haleh Shafeie ◽  
Omid Abouali ◽  
Khosrow Jafarpour
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Removal Rate ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
Navier Stokes ◽  
Liquid Region ◽  
Noticeable Effect ◽  
Pin Fins

This paper presents a numerical study of laminar forced convection in microchannels network heat sinks with fabricated offset pin-fins. A 3-dimensional mathematical model, for conjugate heat transfer in both solid and liquid is presented. For this aim the Navier-Stokes and energy equations for the liquid region and the energy equation for the solid region are solved simultaneously and the pressure drop together heat transfer characteristics of a single-phase microchannel heat sink were investigated. A typical microchannel was selected and it was shown that using offset pin-fins has a noticeable effect and heat removal rate can be increased using this technique. However the pressure drop is also highly increasing which leads to a low coefficient of performance for microchannel with this type of micro-structure.

Numerical Investigation of Single Phase Heat Transfer Enhancement in a Microchannel With Grooved Surfaces

2008 ◽  
Author(s):  
Nemat Baghernezhad ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Single Phase ◽  
Transfer Problem ◽  
Removal Rate ◽  
Heat Removal ◽  
Transfer Characteristic ◽  
Outlet Temperature ◽  
Noticeable Effect

This paper presents an investigation for two types of the grooves (rectangular and arc shapes) fabricated in the microchannel surfaces which leads to enhancement in single phase cooling. The pressure drop and heat transfer characteristic of the single phase microchannel heat sink were investigated numerically for laminar flow. For this purpose the conjugate heat transfer problem involving simultaneous determination of the temperature field in both solid and liquid regions was solved numerically. The heat sink includes an array of rectangular microchannels with grooved surface structures in the side walls and floor of the channel. The effect of these grooves on the pressure drop, outlet temperature of cooling fluid and the heat transfer rate were analyzed. The result showed that using a microchannel with grooved surfaces has a noticeable effect and heat removal rate can be increased using this technique. Also the grooves with the arc shapes have a better performance compared with a rectangular shape groove.

Numerical Investigation of Heat Transfer Enhancement in Heat Sinks With Elongated Hexagonal Fins

2011 ◽  
Author(s):  
Zahra Kheirandish ◽  
Haleh Shafeie ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Numerical Study ◽  
Heat Removal ◽  
Heat Sinks ◽  
Navier Stokes ◽  
Liquid Region ◽  
3 Dimensional ◽  
Solid Region ◽  
Energy Equations

A numerical study was performed for the laminar forced convection of water over a bank of staggered micro fins with cross section of the elongated hexagon. A 3-dimensional mathematical model, for conjugate heat transfer in both solid and liquid is developed. For this aim the Navier-Stokes and energy equations for the liquid region and the energy equation for the solid region are solved simultaneously and the pressure drop as well as the heat transfer characteristics was investigated. The length and width of the studied heat sinks are one centimeter and different heights in the range of 200–500 micrometer were examined for the fluid media. The heat removal of the finned heat sink is compared with an optimum simple mirochannel heat sink. The comparison which is presented at equal pumping powers depicts the enhancement of the heat removal for some specific sizes of the finned heat sink.

Numerical Study of Forced Convection of Nanofluids in a Microchannel Heat Sink

2008 ◽  
Author(s):  
Parisa Vaziee ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Volume Fraction ◽  
Numerical Study ◽  
Heat Removal ◽  
Al2o3 Nanoparticles ◽  
Microchannel Heat Sink ◽  
Particle Volume ◽  
Volume Fractions

Effectiveness of the microchannel heat sink cooled by nanofluids with various particle volume fractions is investigated numerically using the latest theoretical models for conductivity and viscosity of the nanofluids. Both laminar and turbulent flows are considered in this research. The model of conductivity used in this research accounts for the fundamental role of Brownian motion of the nanoparticles which is in good agreement with the experimental data. The changes in viscosity of the nanofluid due to temperature variation are considered also. Final results are compared with the experimental measurements for heat transfer coefficient and pressure drop in microchannel. Enhancement in heat transfer is achieved for laminar flow with increasing of volume fraction of Al2O3 nanoparticles. But for turbulent flow an enhancement of heat removal was not seen and using higher volume fractions of nanoparticles increases the maximum substrate temperature. Pressure drop is increased with using nanofluids because of the augmentation in the viscosity and this increase is more noticeable in higher Reynolds numbers.

Influence of Rib Turbulators on Pin-Fin Heat Transfer in the Trailing Region of Gas Turbine Vane: A Numerical Study

2006 ◽  
Author(s):  
N. Kulasekharan ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Flux Boundary Condition ◽  
Pin Fin ◽  
Pin Fins ◽  
Rib Turbulators

A numerical investigation is carried out for estimating the influence of rib turbulators on heat transfer and pressure drop of staggered non-uniform pin-fin arrays of different shapes, in a simulated cambered vane trailing region. Pin-fins of square, circular and the diamond shapes, each of two sizes (d) were chosen. The ratio of span-wise pitch to longitudinal pitch is 1.06 and that to the pin size are 4.25 and 3.03, for all pin shapes. A constant heat flux boundary condition is assumed over the coolant channel walls, rib surfaces and circumferential faces of the pin-fins. Reynolds number is varied (20,000<ReD<40,000) by changing the coolant outlet to inlet pressure ratio. Pin end-wall and pin surface averaged heat transfer coefficients and Nusselt numbers are estimated and detailed contours of heat transfer coefficient on both the pressure and suction surfaces are presented. Whilst there is an enhancement in heat transfer and pressure drop with ribs for all the pin shapes, diamond pins have shown the highest enhancement values for both ribbed and non-ribbed configuration.

Onboard Device Encapsulation With Two-Phase Cooling

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
S. J. Young ◽  
D. Janssen ◽  
E. A. Wenzel ◽  
B. M. Shadakofsky ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Integrated Circuit ◽  
Flow Boiling ◽  
Heat Removal ◽  
Coolant Flow ◽  
Coefficient Of Performance ◽  
Processing Unit ◽  
Two Phase ◽  
Central Processing

Onboard liquid cooling of electronic devices is demonstrated with liquid delivered externally to the point of heat removal through a conformal encapsulation. The encapsulation creates a flat microgap above the integrated circuit (IC) and delivers a uniform inlet coolant flow over the device. The coolant is Novec™ 7200, and the electronics are simulated with a resistance heater on a 1:1 scale. Thermal performance is demonstrated at power densities of ∼1 kW/cm3 in the microgap. Parameters investigated are pressure drop, average device temperature, heat transfer coefficient, and coefficient of performance (COP). Nusselt numbers for gap sizes of 0.25, 0.5, and 0.75 mm are reduced to a dimensionless correlation. With low coolant inlet subcooling, two-phase heat transfer is seen at all mass flows. Device temperatures reach 95 °C for power dissipation of 50–80 W (0.67–1.08 kW/cm3) depending on coolant flow for a gap of 0.5 mm. Coefficients of performance of ∼100 to 70,000 are determined via measured pressure drop and demonstrate a low pumping penalty at the device level within the range of power and coolant flow considered. The encapsulation with microgap flow boiling provides a means for use of higher power central processing unit and graphics processing unit devices and thereby enables higher computing performance, for example, in embedded airborne computers.

Numerical Investigation of Heat Transfer Enhancement in a Microchannel With Grooved Surfaces

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
O. Abouali ◽  
N. Baghernezhad
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Numerical Investigation ◽  
Wall Thickness ◽  
Single Phase ◽  
Removal Rate ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
Thickness Effect ◽  
Maximum Heat

This paper presents a numerical investigation for two types of grooves (rectangular and arc shapes) fabricated in the microchannel surfaces, which leads to enhancement in single-phase cooling. The pressure drop and heat transfer characteristics of the single-phase microchannel heat sink were investigated numerically for laminar flow. For this purpose, the conjugate heat transfer problem involving simultaneous determination of temperature fields in both solid and liquid regions was solved numerically. The numerical model was validated with comparison to experimental data, in which good agreement was seen. A simple microchannel with available experimental data was selected, and it was shown that using grooved surfaces on this microchannel has a noticeable effect and heat removal rate can be increased using this technique. The results depict that the arc grooves have a higher heat removal flux compared with rectangular grooves but the latter have a higher coefficient of performance for the case in which grooves are made in the floor and both side walls. Also, it was shown that a grooved microchannel with higher wall thickness and lower mass flow rate of cooling water has a higher heat removal flux and coefficient of performance compared with a simple microchannel with minimum wall thickness. Effect of various sizes and distances of the floor grooves was determined, and the cases for maximum heat removal rate and coefficient of performance for both rectangular and arc grooves were obtained.

Comparison of the Effect of Embedded Grooves on the Heat Removal and Pressure Drop in Microchannel Heat Sinks

2011 ◽  
Author(s):  
Farnaz Faily ◽  
Haleh Shafeie ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Heat Removal ◽  
Heat Sinks ◽  
Coefficient Of Performance ◽  
Maximum Heat ◽  
Different Types ◽  
Microchannel Heat Sinks ◽  
Fin Thickness

This paper presents a numerical study for the single phase heat transfer of water in the heat sinks with different types of the grooved microchannels. The cross section of the grooves is either rectangular or arced shape. The grooves are embedded vertically in the side walls of the microchannel but for the floor, different orientation angles of the grooves in the range of 0–60° are investigated. As well, for the grooves on the floor of the channel, the chevron-shape is another pattern which has bee studied. A 3-D computational model is developed for each of the studied cases and the conjugate heat transfer in both solid and liquid is investigated. The governing equations are solved numerically to determine the pressure drop and heat transfer through the heat sink. The results of the heat removal and coefficient of performance (COP) for different types of the grooved microchannel heat sinks are compared to each other as well with those for a simple microchannel heat sink with minimum fin thickness. The comparison shows that the case with minimum vertical fin thickness and arc grooves aligned in 60° on the floor has the maximum heat removal and COP among the studied cases.

scholarly journals Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4417
Author(s):  
Tingting Xu ◽  
Hongxia Zhao ◽  
Miao Wang ◽  
Jianhui Qi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Optimal Structure ◽  
Original Structure ◽  
Brayton Cycle ◽  
Compact Structure ◽  
Spiral Angle

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

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