Experimental Investigation of the Heat Transfer Performance of a Hybrid Cooling Fin Thermosyphon

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Christina A. Pappas ◽  
Donald A. Jordan ◽  
Pamela M. Norris
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Hybrid Cooling ◽  
Evaporator Section ◽  
Fill Volume

The effect of fill volume on the heat transfer performance of a hybrid cooling fin thermosyphon, characterized by an airfoil cross-sectional shape and a slot-shaped cavity, is investigated. The performance was examined at three fill volumes, expressed as a percentage of the evaporator section: 0%, 60%, and 240%. These were chosen to represent three distinct regimes: unfilled, filled, and overfilled evaporator sections, respectively. The cross section of this copper–water thermosyphon has a NACA0010 shape with a chord length of 63.5 mm and an aspect ratio (ratio of the length of the evaporator section to the cavity width) of 1.109. The evaporator length comprises 8.3% of the total thermosyphon length. The air-cooled condenser section was placed in a uniform air flow in the test section of an open return wind tunnel. The rate of heat transfer, or performance, was measured as a function of fill volume and evaporator temperature. The heat transfer performance increased by 100–170% by adding 0.86 ml of working fluid (de-ionized water), i.e., when the fill volume increased from 0% to 60%, which illustrates the improvement of a cooling fin's heat transfer rate by converting it to a hybrid cooling fin thermosyphon. Of the fill volumes investigated, the thermosyphon achieves a maximum heat transfer rate and highest average surface temperature at the 60% fill volume. Overfilling the evaporator section at 240% fill results in a slight decrease in performance from the 60% fill volume. The results of this study demonstrate the feasibility of hybridizing a cooling fin to act both as a cooling fin and a thermosyphon.

Reducing Crossflow Effects in Arrays of Impinging Jets

2017 ◽  
Author(s):  
Nicholas R. Arens ◽  
Mitchell P. Morem ◽  
Jeffrey Doom ◽  
Gregory J. Michna
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Cfd Modeling ◽  
Working Fluid ◽  
Transfer Performance ◽  
Simulation Data ◽  
Jet Array

With increasing heat fluxes in microelectronics, thermal management of these devices will soon no longer be attainable through current methods. One thermal management technology that could be integrated into the design of microelectronics is jet impingement cooling. Past research has primarily focused on evenly spaced, equal-sized, circular or slot jets perpendicular to the surface. A significant problem associated with this technology, especially as the surface to be cooled increases in size, is crossflow. This is the interaction of the transverse flow from the spent inner jet fluid with the jets closer to the outer edge of the surface. In an attempt to attenuate the crossflow effects, the heat transfer performance of jet arrays with non-uniform jet diameter and jet spacing were investigated. The testing apparatus housed a 3D-printed jet array nozzle that could be easily exchanged to accommodate many tests. The use of advanced manufacturing techniques allows for array geometries that may have previously been difficult to create. The impingement surface was a circular, polished, oxygen-free copper surface with a diameter of 25.4 mm. Heat transfer rates nearing 400 W could be delivered to the surface, for a heat flux of more than 75 W/cm2. The working fluid was single phase water, and the heat transfer rate was measured for each jet array over a range of flow rates. Experimental data was compared to simulation data obtained through CFD analysis. CFD modeling was used to predict the most promising geometries, which were then validated through experiment. Out of the nozzles tested, it was determined that the nozzle with larger diameters toward the edge of the surface attained the highest heat transfer rate of h = 38,822 W/m2-K. The nozzle with closer jet spacing at the outside of the array was found to have the highest experimental Nusselt number with NuD = 88.8. It was determined that angled confining walls do not have a definitive association with improved heat transfer. The simulation data was found to predict the heat transfer performance of the various geometries with an average percent difference in heat transfer coefficient of 11%.

Heat Transfer in Serpentine Flow Passages With Rotation

1994 ◽  
Vol 116 (1) ◽  
pp. 133-140 ◽  
Author(s):  
S. Mochizuki ◽  
J. Takamura ◽  
S. Yamawaki ◽  
Wen-Jei Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Performance ◽  
Flow Passage ◽  
Rotation Numbers ◽  
Straight Flow

Heat transfer characteristics of a three-pass serpentine flow passage with rotation are experimentally studied. The walls of the square flow passage are plated with thin stainless-steel foils through which electrical current is applied to generate heat. The local heat transfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both stationary and rotating cases. The throughflow Reynolds, Rayleigh (centrifugal type), and rotation numbers are varied. It is revealed that three-dimensional flow structures cause the heat transfer rate at the bends to be substantially higher than at the straight flow passages. This mechanism is revealed by means of a flow visualization experiment for a nonrotating case. Along the first straight flow passage, the heat transfer rate is increased on the trailing surface but is reduced on the leading surface, due to the action of secondary streams induced by the Coriolis force. At low Reynolds numbers, the local heat transfer performance is primarily a function of buoyancy force. In the higher Reynolds number range, however, the circumferentially averaged Nusselt number is only a weak function of the Rayleigh and rotation numbers.

Influence of Pattern Geometry of Hybrid Surfaces on Dropwise Condensation Heat Transfer and Droplet Dynamics

2018 ◽  
Author(s):  
Karim Egab ◽  
Saad K. Oudah ◽  
M. Alwazzan ◽  
Jamil Khan ◽  
Chen Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Significant Influence ◽  
Atmospheric Pressure ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Condensation Heat Transfer ◽  
Transfer Performance ◽  
Droplet Dynamics ◽  
Lower Performance

The scope of combining two wettability regions is to impact the droplet dynamic behaviors, manipulate the droplets’ mobility and enhance condensation heat transfer. Hydrophobic-hydrophilic hybrid patterns can promote the heat transfer, droplet-renewal frequency and enhance the droplets’ removal during condensation. With regard of condensation on hybrid surfaces, the geometry of the patterns has a significant influence on droplets departure frequency and heat transfer performance. Therefore, different patterns geometries (circle, ellipse, and diamond) have been developed on horizontal copper tubes at atmospheric pressure. All the patterns have the same size, and the same identical gap as well between the adjacent patterns. Results show that the diamond hybrid surface has the best performance compared with ellipse, circles hybrid surfaces at the same pattern area with same neighbor gap between two patterns and complete dropwise However, the circle and ellipse hybrid surfaces outperform lower performance compared to complete dropwise surface. The heat transfer rate for the diamond hybrid surface is 15% higher than complete dropwise surface when the gap is 0.5mm. This study clearly demonstrated the effect of pattern’s geometry regarding maximum condensation heat transfer rate and droplet departure frequency.

The Effect of Fill Volume on Heat Transfer From Air-Cooled Thermosyphons

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Christina A. Pappas ◽  
Paul M. De Cecchis ◽  
Donald A. Jordan ◽  
Pamela M. Norris
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Air Flow ◽  
Condenser Section ◽  
Evaporator Temperature ◽  
Evaporator Section ◽  
Fill Volume ◽  
Inner Diameter ◽  
Cooling Air Flow

The effect of fill volume on the heat transfer performance of a cylindrical thermosyphon with an aspect ratio (ratio of the length of the evaporator section to the inner diameter) of 2.33 immersed in a cooling air flow is investigated. The fill volume was systematically varied from 0% to 70.3% of the volume of the evaporator section in a copper-water thermosyphon having an inner diameter of 19 mm. The condenser section was immersed in a uniform air flow in the test section of an open return wind tunnel. The heat transfer rate was measured as a function of evaporator temperature and fill volume, and these results were characterized by three distinct regions. From 0% to roughly 16% fill volume (Region I), the low rate of heat transfer, which is insensitive to fill volume, suggests that dry out may be occurring. In Region II (extending to approximately 58% fill volume), the heat transfer rate increases approximately linearly with fill volume, and increasing evaporator temperature results in decreased rate of heat transfer. Finally, in Region III (from roughly 58–70.3%), the rate of heat transfer increases more rapidly, though still linearly, with fill volume, and increasing evaporator temperature results in increased rate of heat transfer. The thermosyphon rate of heat transfer is greatest at 70.3% fill volume for every evaporator temperature.

scholarly journals Analytical solution and process analysis of energy pile’s heat transfer rate

2020 ◽  
Vol 205 ◽  
pp. 05026
Author(s):  
Jun Yang ◽  
Zhenguo Yan ◽  
Zhengwei Zhang ◽  
Shu Zeng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Heat Transfer Process ◽  
Transfer Performance ◽  
Energy Pile ◽  
Energy Piles ◽  
The Difference ◽  
Surrounding Soil

With the ever-increasing energy demand and implications of climate change, the use of energy piles to absorb shallow geothermal energy to regulate room temperature of buildings is considered the best sustainable energy technology, especially in China, and the use of this technology is becoming increasingly popular. At present, studies generally uses the temperature field to analyze the heat transfer performance of the energy pile, which cannot represent the heat transfer rate distribution intuitively. In this study, we used mathematical models to provide an analytical solution to determine the heat transfer rate distribution between the energy pile and surrounding soil. Analysis of the heat transfer process of concrete piles in clay showed that the difference in thermal properties between the energy pile and the surrounding soil affected the whole heat transfer process, especially in the initial stage. The time required to reach the quasi-steady state mainly depended on the pile’s volume heat capacity, the thermal diffusivity of the pile and the surrounding soil. In engineering practice, to enhance the heat transfer performance of energy piles, the following measures can be taken: reduce the difference in thermal properties between the energy pile and surrounding soil and increase the distance between energy piles to improve the heat transfer conditions.

Heat Transfer Characteristic of Flat Trapezoid Grooved Micro Heat Pipes

2014 ◽  
Vol 609-610 ◽  
pp. 1526-1531 ◽  
Author(s):  
Yan Xia Yang ◽  
Xiao Dong Wang ◽  
Yi Luo ◽  
Liang Liang Zou
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Capillary Flow ◽  
Transfer Characteristic ◽  
Fluid Distribution ◽  
Working Fluid ◽  
Transfer Performance ◽  
Maximum Heat ◽  
Micro Heat Pipe

To study the heat transfer performance of micro heat pipe, theoretical analysis of flat plate micro heat pipe with trapezoid cross section are presented in this paper. A one-dimensional stationary mathematical model for micro heat pipe grooved capillary flow using finite volume method (FVM) was established. The micro heat pipe had vapor space connect with each other and the influences of shear stress between vapor and fluid in the working process were described in the model which made the model more precisely. The axial variation of working fluid distribution in the heat pipe, pressure difference between vapor and liquid, and velocity of vapor and liquid were analyzed. In addition, the maximum heat transport capacity of micro heat pipe was calculated. The simulation results showed good agreement with the experiment results, and it could predict the heat transfer performance accurately, which was useful to micro heat pipe structural design.

scholarly journals Effects of Coil Pitch Spacing on Heat Transfer Performance of Nanofluid Turbulent Flow through Helical Microtube Heat Exchanger

2019 ◽  
Vol 7 (4.14) ◽  
pp. 356
Author(s):  
A. H. Rasheed ◽  
H. Alias ◽  
S. D. Salman
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance ◽  
Ansys Fluent ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Momentum And Heat Transfer

This article provides Numerical simulation on forced convective heat transfer performance of Nanofluid flowing through copper helical microtube of inner diameter of 1.5 mm with different pitch using ANSYS-FLUENT 18.0. The simulation was performed for water, CuO/water, Al2O3/water Nanofluid with 1-2% volume concentration and different pitch of microtube (10, 14 and 18 mm) for turbulent flow regime of Reynolds number varied 5000 to 20000 and governing equations of mass, momentum and heat transfer were solved simultaneously, using the k-e two equations turbulence model. Based on the obtained results, regardless of the concentrations used, the nanofluids exhibited a higher transfer rate than water. This is mainly attributed to the nanoparticles that are in the used nanofluids. The friction factor and the heat transfer rate were enhanced considerably due to the shape and size of the tube, which in this case is a helical microtube. Moreover, the maximum heat transfer performance has been conducted by Al2O3/water Nanofluid with 2% volume concentration and microtube pitch of 18 mm.    

SIMULATION RESULTS FOR THE EFFECT OF FIN GEOMETRY ON THE PERFORMANCE OF A CONCENTRIC HEAT EXCHANGER

2014 ◽  
Vol 22 (04) ◽  
pp. 1450026 ◽  
Author(s):  
HONGGI CHO ◽  
TAEHUN KIM ◽  
JUNGHO KIM ◽  
CHANGSEON LEE ◽  
JAEYOUNG CHOI
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Working Fluid ◽  
Outer Diameter ◽  
Maximum Heat ◽  
Simulation Results ◽  
Fin Thickness

The present study is aimed to investigate the effect of fin geometry on the performance of a concentric heat exchanger with the commercial CFD software of Star CCM+. In general, the concentric heat exchanger consists of inner and outer tubes. The inner tube has a lot of serrated fins spirally manufactured on its surface in order to increase the heat transfer performance. A simplified simulation model has been applied to simulate the performance of the concentric heat exchanger in this study. Both inner and outer tubes have the same length of 60 mm. The inner diameter of outer tube is 17.05 mm. The outer diameter of inner tube before manufacturing fins is 11.5 mm. Water is used as a working fluid and the concentric heat exchanger has a counter-flow configuration. The simulation parameters were fin height, fin thickness and fin width. It was found that heat transfer rate increased by 3–4% as the fin height increased from 0.95 to 1.15 mm. However, pressure drop increased highly by 39–41%. The effectiveness, which could be evaluated by calculating the ratio of enhancement of heat transfer rate to that of pressure drop, was about 74% for the fin height of 1.15 mm. In case of fin height of 1.05 mm, the effectiveness was 88% due to the increase in pressure drop, about 15%, compared with the base fin height of 0.95 mm. Also, it was noted that the effectiveness was about 88% and 95% for the fin thickness of 0.5 and 0.4 mm, respectively, compared with the base fin thickness of 0.3 mm. In case of increasing the fin width from 0.8 to 1.2 mm, the heat transfer rates slightly increased by 1–2% and the pressures drops increased by 3–4%. Hence, the effectiveness was about 98% for the fin width of 1.2 mm. And the effectiveness for the fin width of 1.0 mm was 97%. Based on the simulation results, it was concluded that maximum heat transfer rate has been obtained when the fin height is 1.15 mm. However, pressure drop is considerably increased by 39–41%. Therefore, the fin height should be carefully determined according to the criteria of pressure drop.

Sign in / Sign up

Export Citation Format

Share Document