Modeling and Testing a Cold Plate

2006 ◽  
Author(s):  
Bryan R. Wilcox ◽  
Donald W. Mueller ◽  
Hosni I. Abu-Mulaweh
Keyword(s):  
Numerical Model ◽  
Thermal Resistance ◽  
Cover Plate ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Flow Rate ◽  
Cold Plate ◽  
Maximum Temperature Difference ◽  
Total Thermal Resistance

The objectives of this work were to build and test a liquidcooled cold plate, and then to develop a numerical model to describe the thermal characteristics of the cold plate. An important parameter of interest was the total thermal resistance of the cold plate which is defined as the maximum temperature difference divided by the net heat flow rate. A cold plate was constructed by machining nine parallel, rectangular channels into an aluminum base (1.65 cm × 7.6 cm × 40 cm) upon which an aluminum cover plate was then welded. Twelve thermocouples were used to measure the temperature of the plate (surface and fin tip) and the circulating fluid at the inlet, outlet, and mid-plane. The working fluid was a 50/50 ethylene glycol-water mixture. Three heater blocks were mounted to the cold plate, and the assembly was insulated so that heat loss to the surroundings was minimized. Four runs were performed with flow rates ranging from 56 g/s to 95 g/s, and after steady-state conditions were reached the temperatures were recorded. Using these temperature measurements, the total thermal resistance was calculated. The thermal resistance of the cold plate was also calculated using a one-dimensional numerical model; agreement between the experimental measurements and model predictions is good. The methods described and results presented in this paper are useful to applied thermal engineers.

Study on Influences Mold Shape Imposes on Bread Heating Distribution

2013 ◽  
Vol 395-396 ◽  
pp. 925-929
Author(s):  
Ze Hua Chen ◽  
Shao Bo Gao ◽  
Shang Xin Yang ◽  
Hai Yang Zhang
Keyword(s):  
Theoretical Model ◽  
Numerical Model ◽  
Great Influence ◽  
Maximum Temperature ◽  
Maximum Temperature Difference ◽  
Distribution Uniformity ◽  
Boundary Curvature ◽  
3D Numerical Model ◽  
Bread Production ◽  
Better Than

A 3D numerical model for heating distribution of bread mold in the oven is presented in this study. In the process of bread production, heat effect is influenced by the shape of the mold. Being consistent with the results of calculation, the shape of the mold imposes great influence on the heating distribution uniformity and maximum temperature difference. Because of even boundary curvature, circular mold behaves better than elliptical and rectangular mold. By utilizing the introduced theoretical model, we are able to get the spatial heating distribution of all kinds of mold. And taking three kinds of mold as example, we illustrate that the more uneven the boundary curvature is, the less uniform the heating distribution will be.

Experimental Investigation on the Minichannel Cold Plate for High Temperature Uniformity Based on a Compact Thermal Model

2013 ◽  
Author(s):  
Xiaobing Luo ◽  
Zhangming Mao
Keyword(s):  
High Temperature ◽  
Working Conditions ◽  
Thermal Model ◽  
Maximum Temperature ◽  
Large Temperature ◽  
Heat Sources ◽  
Cold Plate ◽  
Temperature Uniformity ◽  
Maximum Temperature Difference ◽  
Maximum Value

A compact thermal model for multiple heat sources mounted on minichannel cold plate to achieve high temperature uniformity was presented in the authors’ previous work. In this paper, based on this compact thermal model, a fractal tree-like minichannel cold plate was designed and fabricated to obtain high temperature uniformity, and its thermal performance was tested under different working conditions by experiments. The comparison reveals that the measured temperatures are close to the ones predicted by the compact thermal model. The cold plate designed based on the compact thermal model can help multiple heat sources achieve high temperature uniformity, and the maximum temperature difference among the heat sources is 1.3 °C. Moreover, a straight minichannel cold plate was designed and tested under the same conditions. The measured results show that there exists relatively large temperature gap among the heat sources, and the maximum value is 6.7°C, which is much higher than 1.3 °C in the fractal tree-like minichannel. Therefore, the fractal tree-like microchannel or minichannel cold plate has an advantage over the straight one in obtaining temperature uniformity for multiple heat sources.

scholarly journals Experimental Set up of Two Closed Loop Pulsating Heat Pipe (CLPHP) with Water base Fluids

2019 ◽  
Vol 8 (12S) ◽  
pp. 715-719
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Dissipation ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Water Mixture ◽  
Working Fluids ◽  
Pure Fluids ◽  
Acetone Water

Heat pipes are deliberated to be effective heat dissipation devices compared to other types of heat sinks due to their high effective thermal conductivity. Because of the flexibility in the design and layout of heat pipe turns along the heat source, pulsating heat pipes have gained popularity. One of the parameters that have the mainimpact on the presentation of CLPHP is the thermo physical properties of the working fluid. The properties of the working fluid affect the temperature difference between the evaporator and the condenser which in turn affect the thermal resistance of the CLPHP. In this connection, the influence of different working fluids is experimentally investigated on a two loop CLPHP, varying the evaporator heat flux. Pure fluids, viz., water, acetone, benzene and binary mixture, viz., Acetone-water and Benzene-water are utilized on working fluids. The heat input considered at the evaporator is 32W, 48W and 60W. The filling ratio is kept as 50 %. The results show that among the working fluids considered for the study, acetone exhibits least thermal resistance among the pure fluids at all heat fluxes considered in the analysis, while Acetone-water mixture has exhibited least thermal resistance among the water based mixtures.

scholarly journals Mathematical apparatus for determination of homogenous scalar medium thermal resistance

Vestnik MGSU ◽  
2019 ◽  
pp. 1037-1045
Author(s):  
Tatiana A. Musorina, ◽  
Michail R. Petritchenko ◽  
Daria D. Zaborova
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Resistance ◽  
Heat Conducting ◽  
Heat Flow Rate ◽  
Conductivity Equation ◽  
Total Thermal Resistance ◽  
Active Resistance ◽  
One Dimensional

Introduction: the article suggests a method for determining a thermal resistance of small and large-sized areas (one-dimensional and multidimensional problems) of wall enclosure. The subject of the study is the thermal resistance of homogeneous scalar medium (homogeneous wall enclosure). The aim is the determination of thermal resistance of a wall structure for areas of arbitrary dimension (by the coordinates xi, where 1 ≤ i ≤ d and d is the area dimension) filled with a scalar (homogeneous and isotropic) heat-conducting medium. Materials and methods: the article used the following physical laws: Fourier law (the value of the heat flow when transferring heat through thermal conductivity) and continuity condition for the heat flow rate leading to the thermal conductivity equation. Results: this method extends the standard definition of thermal resistance. The research proved that the active thermal resistance does not increase with increasing of the area dimension (for example, when switching from a thin shell or plate to a rectangle with length and width of the same order of magnitude). That is the sense of geometric inclusion, i.e., increase of the dimension of an area filled with a homogeneous isotropic medium. Evident expressions are obtained for the determination of active, reactive, and total thermal resistance. It is proved that the total resistance is higher than the active resistance since the reactive resistance is positive, and the wall possesses an ability to suppress the temperature fluctuations and accumulate/give up the heat. Conclusions: the appearance of an additional wall dimension (comparable length-to-thickness ratio) does not increase its active resistance. In the general case, the total thermal resistance exceeds the active thermal resistance no more than four times. Geometric inclusions must be considered in the calculation of wall enclosures that are variant from one-dimensional bodies.

Experimental Investigation of a Cost Effective Skived Microchannel Cold Plate for Mass Production

2015 ◽  
Author(s):  
Mark E. Steinke ◽  
Vinod Kamath
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Cost Effective ◽  
Thin Layers ◽  
Warm Water ◽  
Working Fluid ◽  
Manufacturing Cost ◽  
Cold Plate ◽  
Ambient Temperatures ◽  
And Performance

A liquid cold plate that utilizes skived microchannels has been developed to gain the benefits of direct liquid cooling, but minimize the expensive cost of such cold plates. The construction, application, and experimental results of the skived cold plate will be presented. Skiving is a mechanical process that cuts thin layers of material. It is an established process for making air cooled heat sinks. In this application, the fin field is skived and placed inside a housing that allows for liquid flow through the resulting fins. The design boundary conditions and parameters will be described and performance per cost metric will be presented and used to evaluate future optimization possibilities. The objective of the present work was to minimize the thermal resistance while maintaining a low manufacturing cost. The design goal was to produce a cold plate that had sufficient thermal performance and the ability to be mass produced at a reasonable cost. The resulting cold plate would also need to support warm water cooling of microprocessors. Warm water is a working fluid that has not been chilled below ambient temperatures. Therefore, the water temperature could be up to 45 degrees Celsius. The cold plate had a thermal resistance less than 0.3 °Ccm2/W. The pressure drop was minimized to lower the required pumping power and was less than 6 kPa at 1.0 liter per minute. Using a skiving process, it is possible to develop a cold plate that delivers good thermal performance and maintains a low production cost.

Heat Recovery With Oscillating Heat Pipes

2013 ◽  
Author(s):  
Charles R. McCullough ◽  
Scott M. Thompson ◽  
Heejin Cho
Keyword(s):  
Thermal Conductivity ◽  
Temperature Difference ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Heat Pipes ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Two Phase ◽  
Maximum Temperature Difference

Waste-heat recovery applied in HVAC air systems is of interest to increase the energy efficiency of residential, commercial and industrial buildings. In this study, the feasibility of using tubular-shaped oscillating heat pipes (OHPs), which are two-phase heat transfer devices with ultra-high thermal conductivity, for heat exchange between counter-flowing air streams (i.e., outdoor and exhaust air flows) was investigated. For a prescribed volumetric flow rate of air and duct geometry, four different OHP Heat Exchangers (OHP-HEs) were sized via the ε-NTU method for the task of sub-cooling intake air 5.5 °C (10 °F). The OHP-HE tubes were assumed to have a static thermal conductivity of 50,000 W/m·K and only operate upon a minimum temperature difference in order to simulate their inherent heat transport capability and start-up behavior. Using acetone as the working fluid, it was found that for a maximum temperature difference of 7°C or more, the OHP-HE can operate and provide for an effectiveness of 0.36. Pressure drop analysis indicates the presented OHP-HE design configurations provide for a minimum of 5 kPa. The current work provides a necessary step for quantifying and designing the OHP for waste heat recovery in AC systems.

Research on Thermal Resistance of Micro Heat Pipe with Sintered Wick

2013 ◽  
Vol 589-590 ◽  
pp. 552-558
Author(s):  
Xi Bing Li ◽  
Xun Wang ◽  
Yun Shi Ma ◽  
Zhong Liang Cao
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Performance ◽  
Total Thermal Resistance ◽  
Vapor Cavity ◽  
Micro Heat Pipe

As a highly efficient heat dissipation unit, a micro heat pipe is widely used in high heat flux microelectronic chips, and its thermal resistance is crucial to heat transfer capacity. Through analyses of the structure and heat transfer performance of a circular heat pipe with sintered wick, the theoretical model of total thermal resistance was established on heat transfer theory, and then simplified, finally a testing platform was set up to test for total thermal resistance performance. The testing results show that when the micro heat pipe is in optimal heat transfer state, its total thermal resistance conform well with that from the theoretical model, and its actual thermal resistance is much lower than that of the rod made of the material with perfect thermal conductivity and of the same geometric size. With the increment of heat transfer capability, the total thermal resistance of a micro heat pipe with sintered wick decreases first, then increases and reaches the minimum when it is in the optimal heat transfer state. The greater total thermal resistance in low heat transfer performance is mainly caused by too much working fluid accumulating in evaporator and the lower velocity in vapor cavity, and the greater total thermal resistance in high heat transfer performance is mainly due to the working fluid drying up in condenser. Total thermal resistance is related to many factors, such as thermal conductivity of tube-shell material, wall thickness, wick thickness, copper powders grain size and porosity, the lengths of condenser and evaporator, and the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with sintered wick should be reasonably designed according to the specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements.

scholarly journals Integration of a Multiple-Condenser Loop Heat Pipe in a Compact Air-Cooled Heat Sink

2013 ◽  
Author(s):  
H. Arthur Kariya ◽  
Daniel F. Hanks ◽  
Wayne L. Staats ◽  
Nicholas A. Roche ◽  
Martin Cleary ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Sink ◽  
High Performance ◽  
Ambient Air ◽  
Optimal Operation ◽  
Working Fluid ◽  
Air Cooling ◽  
Loop Heat Pipe ◽  
Total Thermal Resistance

We present the characterization of a compact, high performance air-cooled heat sink with an integrated loop heat pipe. In this configuration, heat enters the heat sink at the evaporator base and is transferred within the heat pipe by the latent heat of vaporization of a working fluid. From the condensers, the heat is transferred to the ambient air by an integrated fan. Multiple condensers are used to increase the surface area available for air-cooling, and to ensure the equal and optimal operation of the individual condensers, an additional wick is incorporated into the condensers. We demonstrated with this design (10.2 cm × 10.2 cm × 9 cm), a total thermal resistance of less than 0.1 °C/W while dissipating a heat load of 500 W from a source at 75 °C. Furthermore, constant thermal resistance was observed in the upright as well as sideways orientations. This prototype is a proof-of-concept demonstration of a high performance and efficient air-cooled heat sink design that can be readily integrated for various electronics packaging and data center applications.

scholarly journals Pulsed Heat Transfer for Thermal Maximum Power Point Tracking

2013 ◽  
Author(s):  
Ian Salmon McKay ◽  
Evelyn N. Wang
Keyword(s):  
Heat Transfer ◽  
Energy Harvesting ◽  
Thermal Resistance ◽  
Thermal Energy ◽  
Heat Sink ◽  
Waste Heat ◽  
Heat Engine ◽  
Total Power ◽  
Maximum Temperature ◽  
Total Thermal Resistance

This paper presents a new method for enhancing thermal energy harvesting via pulsed heat transfer. By acting as a variable thermal resistance that theoretically generates no entropy, a pulsed thermal connection allows calibration of the effective thermal resistance of an energy harvesting system. By adjusting the frequency and duty cycle of the pulsed heat transfer, the method allows an energy harvester to be continuously optimized for a variable incident heat flux. In this paper, the analysis of a generalized model shows how the pulse strategy theoretically allows any heat engine-heat sink pair to work at the same power and efficiency as a 1:1 thermal resistance-matched engine-heat sink pair of equal or greater total thermal resistance. Experiments with a mechanical thermal switch validate this model, and show how the pulse strategy can improve the efficiency of a system with equal engine and heat sink thermal resistances by over 80% with no increase in the hot-side maximum temperature, although at reduced total power. At a 1:2 engine-sink resistance ratio, the improvement can simultaneously exceed 60% in power and 15% in efficiency. The thermal pulse strategy could be implemented to improve of a variety of systems that convert thermal energy, from waste heat harvesters to the radioisotope power systems on many spacecraft.

Investigation on Operating Processes for a New Solar Cooling Cogeneration Plant

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
R. Shankar ◽  
T. Srinivas
Keyword(s):  
Power Generation ◽  
Thermal Efficiency ◽  
Power Efficiency ◽  
Climatic Conditions ◽  
Coefficient Of Performance ◽  
Maximum Temperature ◽  
Specific Power ◽  
Working Fluid ◽  
Water Mixture ◽  
Cogeneration Plant

Some commercial units and industries need more amount of cooling than the power such as cold storage, shopping complex, etc. In this work, a new cooling cogeneration cycle (Srinivas cycle) has been proposed and solved to generate more cooling with adequate power generation from single source of heat at hot climatic conditions with ammonia–water mixture as a working fluid. The operational processes conditions for the proposed cooling cogeneration plant are different compared to the power-only (Kalina cycle system) system and cooling-only (vapor absorption refrigeration) system. This work focused to generate the optimum working conditions by parametric analysis from thermodynamic point of view. An increase in cycle maximum temperature is only supporting the power generation but not the cooling output. Cooling output is also 15 times more than power generation. So, it has been recommended to operate the integrated plant with low temperature heat recovery. The resulted cycle thermal efficiency, plant thermal efficiency, specific power, specific cooling, cycle power efficiency, cycle coefficient of performance (COP), and solar collector's specific area are 27%, 10%, 15 kW, 220 kW, 1.8%, 0.25, and 10 m2/kW, respectively.

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