Numerical and Experimental Investigation of Heat Transfer Enhancement Using Heat Pipes for Electronic Cooling

2018 ◽  
Author(s):  
Ning Zhang ◽  
Pankaj R. Chandra ◽  
Ryan Robledo ◽  
Sree Harsha Balijepalli
Keyword(s):  
Heat Transfer ◽  
Heat Pipes ◽  
Copper Plate ◽  
Heat Sinks ◽  
Modern World ◽  
Processing Unit ◽  
Maximum Heat ◽  
Central Processing ◽  
Load Combination ◽  
Maximum Heat Transfer

Computers are crucial to nearly every endeavor in the modern world. Some computers, particularly those used in military applications, are required to endure extreme conditions with limited maintenance and few parts. Units such as these will hereafter be referred to as “rugged computers.” This series of experiments aims to produce improvements to rugged computers currently in service. Using heat pipes and finned heat sinks on an enclosed box, a computer’s Central Processing Unit (CPU) is able to reject heat without suffering contamination from unforgiving environments. A modular prototype was designed to allow for three distinct cases; a case with no heat pipes and fins, a cast with heat-pipes mounted internally with exterior fins and a case with heat-pipes extended externally with exterior fins. Each case was tested at three different heat loads, with a copper plate heated by a silicone heat strip simulating the heat load generated by a CPU. Each case/load combination was run many times to check for repeatability. The aim of this research is to discover the ideal case for maximum heat transfer from the CPU to the external environment. In addition to the experiments, numerical simulation of these modular prototypes with different designs of heat pipes were conducted in this research. Creating an accurate model for computer simulations will provide validation for the experiments and will prove useful in testing cases not represented by the modular prototype. The flow and heat transfer simulations were conducted using Autodesk CFD. The aim here is to create a model that accurately reflects the experimentally-verified results from the modular prototype’s cases and loads, thereby providing a base from whence further designs can branch off and be simulated with a fair degree of accuracy.

Two Different Types of Axially-Grooved Heat Pipes and Thermal Performance Comparison

2007 ◽  
Author(s):  
Yong Chi ◽  
Yong Tang ◽  
Le-Lun Jiang ◽  
Zhen-Ping Wan ◽  
Min-Qiang Pan
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Performance Comparison ◽  
Maximum Heat ◽  
Horizontal Orientation ◽  
Maximum Heat Transfer ◽  
Inclination Angles ◽  
The One

Heat pipes have been widely applied to the cooling of microelectronics chips at present. In this paper, to conduct a comparative study on heat pipe performance with different groove structures, two types of axially-grooved heat pipe were manufactured by spinning and secondary broaching respectively. The heat pipe A formed by spinning has homogeneous 55 U-shaped grooves on the inner wall. The grooves with depth of 220μm, width of 200μm and groove angle of 15° are smooth. While the inner wall of the heat pipe B fabricated by secondary broaching is scored and the grooves are heterogeneous. The comparison of heat transfer performance and start-up of two heat pipes are analyzed and investigated under different orientations and heat loads. Experimental results show that the heat pipe formed by spinning has a stronger level of heat transfer capabilities than heat pipe formed by secondary broaching. The maximum heat transfer rate for the heat pipe formed by spinning is almost 70Watts, while the one for the heat pipe fabricated by secondary broaching is only 20Watts. The minimum thermal resistance of the heat pipe A and B was 0.020°C/W and 0.068°C/W respectively. At positive inclination angles in gravity-assisted condition, the thermal performance of both two heat pipe have not obvious difference with at horizontal orientation. But at negative inclination angles in anti-gravity condition, the gravity will play an important role on grooved heat pipes.

Cooling Performances of Perforated-Finned Heat Sinks

2016 ◽  
Author(s):  
Mohammad Reza Shaeri ◽  
Bradley Richard ◽  
Richard Bonner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Cooling System ◽  
Thermal Characteristics ◽  
Heat Sinks ◽  
Pumping Power ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Cooling performances of perforated-finned heat sinks (PFHS) are investigated in the laminar forced convection heat transfer mode, through detailed experiments. Perforations like windows with square cross sections are placed on the lateral surfaces of the fins. Cooling performances are evaluated due to changes in both porosities and perforation sizes. Thermal characteristics are reported based on pumping power, in order to provide more practical insight about performances of PFHSs in real applications. It is found that at a constant perforation size, there is an optimum porosity that results in the largest heat transfer coefficient. For a fixed porosity, increasing the number of perforations (reducing the perforation size) results in an enhancement of heat transfer rate due to repeated interruption of the thermal boundary layer. The opposite trend is observed for PFHSs with larger perforation sizes. This indicates that there is an optimum perforation size and distance between perforations in order to achieve the maximum heat transfer coefficients at a constant porosity. Also, a PFHS results in a smaller temperature non-uniformity across the heat sink base, as well as a more rapid reduction in temperature non-uniformity on the heat sink base by increasing pumping power. In addition, the advantage of a PFHS to reduce the overall weight of the cooling system is incorporated into thermal characteristics of the heat sinks, and demonstrated by the mass specific heat transfer coefficient.

An Apparatus to Measure the Maximum Heat Transfer Rate in Heat Pipes

1987 ◽  
Vol 109 (4) ◽  
pp. 1023-1025
Author(s):  
J. H. Ambrose ◽  
L. C. Chow ◽  
J. E. Beam
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Maximum Heat ◽  
Maximum Heat Transfer

A Novel Quick Qmax Test Method and Experimental Investigation of Heat Pipes

2005 ◽  
Author(s):  
Yao-Chen Chan ◽  
Wei-Keng Lin
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Adiabatic Temperature ◽  
Test Method ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Dry Out

In traditional heat pipe performance test, to keep an adiabatic temperature at a constant value, the evaporator wall temperature would be slowly increased when the thermal power was step input to the evaporator of the heat pipe. The maximum heat transfer rate (Qmax) was then defined that when the evaporator wall temperature rapidly increased at a certain amount of power input to the heat pipe. However, it is not easy to distinguish this sharp increased curve and sometimes result in the wrong Qmax data. In addition, it took too long for waiting the evaporator temperature approach to a steady state, thus this process could not use be for the fully check Qmax of the heat pipe. In this paper, we propose a novel quick test method to predict the maximum heat dissipation of the heat pipes namely Dynamic-Temperature-Tracing (D.T.T). The concept of the D.T.T was when we tracing the evaporator and the adiabatic wall temperature, these two temperature curves should be the same trend before the dry-out phenomena was occurred. Theoretically, when the dry-out start to occur in the heat pipe, the adiabatic temperature profile was no longer kept the same temperature profile as that of the evaporator. Hence, the maximum heat dissipate ability of the heat pipe was then easy to obtained at this measuring adiabatic temperature. The data were also compared with those obtained from the traditional standard method at the same equivalent evaporator length, condenser length and adiabatic temperature. In this experiments, sinter powder and groove heat pipes with diameter 6mm 8mm and 200mm length were selected as the capillary wick structure. Comparing with traditional method results, the errors of maximum heat transfer rate are less than 15%. The results also shown D.T.T. method is much fast and reliable compare with the traditional test method.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

Heat output and maximum heat transfer of heat pipes with continuous corrugated wicks

1986 ◽  
Vol 50 (1) ◽  
pp. 46-53 ◽  
Author(s):  
B. A. Afanas'ev ◽  
E. P. Vinogradova ◽  
G. F. Smirnov
Keyword(s):  
Heat Transfer ◽  
Heat Pipes ◽  
Heat Output ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat Transfer in a Rotating Rib-Roughened Wedge-Shaped U-Duct

2017 ◽  
Author(s):  
Liang Ding ◽  
Shuqing Tian ◽  
Hongwu Deng
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Copper Plate ◽  
Enhancement Effect ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Pressure Drops ◽  
Maximum Heat Transfer ◽  
Rotation Numbers ◽  
First Pass

Heat transfer in a rotating two-pass trapezium-shaped channel, with staggered 90-deg ribs on both leading and trailing surfaces is experimentally investigated. The hydraulic diameter of the first and second pass is 24.5 mm and 16.9 mm, respectively. The inlet Reynolds number and rotational speed range from 10000 to 50000 and zero to 1000 rpm, respectively, which results in the inlet rotation number varying from zero to 1.0. The heated copper plate technique is employed to measure the regional averaged heater transfer coefficients. Pressure drops are measured by newly designed rotating pressure measurements module. Both ribbed cases and smooth cases are compared to present rib enhancement effect. For non-rotating result, the results show that the trailing surface presents much higher heat transfer than other cases due to the special wedge-shaped geometry. The ribbed wedge-shaped achieves enhanced regional heat transfer performances than the smooth case at all locations. Compared with the non-rotating results in the first pass, heat transfer on both trailing and leading surfaces is enhanced except for the position near the turn region, but weakened on outer surface in stream-wise direction. And at high rotation numbers, the highest maximum heat transfer on railing surface happens at a location of approximately X/D = 10. In the first pass, rotation always enhances heat transfer on the trailing surface as rotation number increases and the rotation-to-stationary Nusselt number ratio reaches to 2.0 at the rotation number of 0.5. The leading and outer surfaces both have a critical rotation number located at Roc = 0.05.

Enhanced Heat Transfer in Radial Heat Sinks for LED Lamps

2018 ◽  
Author(s):  
Fernando Cano-Banda ◽  
Ana Gallardo-Gutierrez ◽  
Jesus Garcia-Gonzalez ◽  
Abel Hernandez-Guerrero ◽  
Luis Luviano-Ortiz
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Heat Sinks ◽  
Output Analysis ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Longitudinal Orientation ◽  
Radial Heat

A radial design of a passive heat sink for cooling LED illumination devices is analyzed numerically in order to identify the geometric shape that promotes better heat dissipation rates. Natural convection with the surrounding is considered during the operation of the heat sink. Due to the fact that natural convection is the main mechanism of heat transfer, the shape of the heat sink has a high influence in the heat dissipated. An analysis of the influence of different parameters of a heat sink is conducted in the presented study. The radial heat sink under analysis consists in a flat disc with rectangular fins on it, and the fins are distributed with a radial longitudinal orientation in a circular row arrangement. The number of rows can vary but there is a constant relation of two times the number of fins between the number of fins in an inner row and the next outer row. In order to find a correct configuration to improve the dissipation of heat, parameters like the number of fins, the length of the fins and the separation between fins are studied. The average Nusselt number and thermal resistance for each geometric configuration are compared. The output analysis provides the best shape for a maximum heat transfer.

Flow Boiling in a Heat Sink Embedded With Hexagonally Linked Minichannels

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Shubhankar Chakraborty ◽  
Omprakash Sahu ◽  
Prasanta Kr. Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Vapor Quality ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
The Heat Transfer Coefficient

The thermal hydraulic performance of a miniature heat sink during flow boiling of distilled water is presented in this article. The unique design of the heat sink contains a number of microchannels of 1 mm × 1 mm cross section arranged in a regular hexagonal array. The design facilitates repeated division and joining of individual streams from different microchannels and thereby can enhance heat transfer. Individual slug bubble experiences a typical route of break up, coalescence, and growth. The randomness of these processes enhances the transport of heat. With the increase of vapor quality the heat transfer coefficient increases, reaches the maximum value, and then drops. The maximum heat transfer coefficient occurs at an exit vapor quality much higher than that observed in conventional parallel microchannel heat sinks. Repeated redistribution of the coolant in the interlinked channels and the restricted growth of the slug bubbles may be responsible for this trend.

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