Design and Optimization of Multiple Microchannel Heat Transfer Systems

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Jingru Zhang ◽  
Po Ting Lin ◽  
Yogesh Jaluria
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Optimization Problems ◽  
Numerical Models ◽  
Heat Removal ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Channel Height ◽  
Physical Constraints ◽  
Design And Optimization

In this paper, two different configurations of multiple microchannel heat sinks, with fluid flow, are investigated for heat removal: straight and U-shaped channel designs. Numerical models are utilized to study the multiphysics behavior in the microchannels and these are validated by comparisons with experimental results. The main focus of this work is on the design and optimization of these systems and to outline the methodology that may be used for other similar thermal systems. Three responses, including thermal resistance, pressure drop, and maximum temperature, are parametrically modeled with respect to various design variables and operating conditions such as dimensions of the channels, total number of channels, and flow rate. Multi-objective optimization problems, which minimize the thermal resistance and the pressure drop simultaneously, are formulated and studied. Physical constraints in terms of channel height, maximum temperature, and pressure are further investigated. The Pareto frontiers are studied and the trade-off behavior between the thermal resistance and the pressure drop are discussed. Characteristic results are presented and discussed.

Designs of Multiple Microchannel Heat Transfer Systems

2011 ◽  
Author(s):  
Jingru Zhang ◽  
Po Ting Lin ◽  
Yogesh Jaluria
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Optimization Problems ◽  
Numerical Models ◽  
Electronic Cooling ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Channel Height ◽  
Physical Constraints ◽  
Temperature And Pressure

In this paper, two different configurations of multiple microchannel heat sinks with fluid flow are investigated for electronic cooling: straight and U-shaped channel designs. Numerical models are utilized to study the multiphysics behavior in the microchannels and validated by comparisons with experimental results. Three responses, including thermal resistance, pressure drop, and maximum temperature, are parametrically modeled with respect to various variables such as dimensions of the channels, total number of channels, and flow rate. Multi-objective optimization problems, which minimize the thermal resistance and the pressure drop simultaneously, are formulated and studied. Physical constraints in terms of channel height, maximum temperature, and pressure are further investigated. The Pareto frontiers are studied and the trade-off behavior between the thermal resistance and the pressure drop are discussed.

scholarly journals Thermal Resistance and Pressure Drop Minimization for a Micro-gap Heat Sink with Internal Micro-fins by Parametric Optimization of Operating Conditions

CFD Letters ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 100-112
Author(s):  
Shugata Ahmed ◽  
Erwin Sulaeman ◽  
Ahmad Faris Ismail ◽  
Muhammad Hasibul Hasan ◽  
Zahir Hanouf
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Void Fraction ◽  
Heat Sink ◽  
Operating Conditions ◽  
Superior Performance ◽  
Pumping Power ◽  
Two Phase ◽  
Total Thermal Resistance

In recent years, researchers are investigating several potential applications of two-phase flow in micro-gap heat sinks; electronic cooling is one of them. Further, internal micro-fins are used to enhance the heat transfer rate. However, the pressure drop penalty due to small gap height and fin surfaces is a major concern. Hence, minimization of thermal resistance and pressure drop is required. In this paper, effects of operating conditions, e.g., wall heat flux, pumping power, and inlet void fraction, on total thermal resistance and pressure drop in a micro-gap heat sink with internal micro-fins of rectangular and triangular profiles have been investigated by numerical analysis for the R-134a coolant. Furthermore, optimization of these parameters has been carried out by response surface methodology. Simulation results show that rectangular micro-fins show superior performance compared to triangular fins in reducing thermal resistance. Finally, for an optimum condition (7.1202×10-5 W pumping power, 1.2×107 Wm-2 heat flux, and 0.03 inlet void fraction), thermal resistance and pressure drop are reduced by 56.3% and 87.2%, respectively.

Transient Performance of Heat Pipes Using Nanofluids

2020 ◽  
Author(s):  
Mahboobe Mahdavi ◽  
Amir Faghri
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Response Time ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Volume Concentration ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Vapor Flow ◽  
Transient Performance

Abstract In the present works, a comprehensive transient numerical model was developed to evaluate the effect of nanofluid on the transient performance of heat pipes. The numerical model solves for compressible vapor flow, the liquid flow in the wick region, and the energy equations in the vapor, wick and wall. The distinctive feature of the model is that it can uniquely determine the heat pipe operating pressure based on the physical and operating conditions of the system. Three nanoparticle types were considered: Al2O3, CuO, and TiO2. The effects of the concentration of nanoparticles (5%, 10%, 20% and 40%) were investigated on the heat pipe response time, thermal resistance, and pressure drop under various operating conditions. The results showed that the use of nanofluid decreased the response time of the heat pipe by the maximum of 27%. It was also discovered that the thermal resistance decreased significantly with an increase in the volume concentration. A maximum reduction of 84%, 82% and 78% in thermal resistance was obtained for Al2O3, CuO, and TiO2, respectively. In addition, the effect of nanoparticles on the liquid pressure drop highly depends on the nanoparticle type and volume concentration.

Validation of Twin-Screw Polymer Extruder Modeling

2002 ◽  
Author(s):  
Yogesh Jaluria
Keyword(s):  
Numerical Modeling ◽  
Numerical Models ◽  
Polymeric Materials ◽  
Operating Conditions ◽  
Design Parameters ◽  
Design And Optimization ◽  
Single Screw Extruder ◽  
Twin Screw ◽  
Accuracy Of Results ◽  
Mathematical And Numerical Modeling

The mathematical and numerical modeling of twin-screw polymer extruders is examined with respect to accuracy of results and validity of the simulation. A numerical model is developed incorporating the translation region, which is similar to a single-screw extruder channel, and the intermeshing, or nip, region. The numerical modeling is carried out for steady and time-dependent operation, considering various polymeric materials like polyethylene and corn meal. A range of design parameters and operating conditions are considered. The results are evaluated in terms of the expected physical behavior of the system and compared with experimental results available in the literature to determine the accuracy of the predictions. In many cases, only qualitative comparisons are possible since the operating conditions and design parameters are not explicitly known. However, the basic trends are as expected and good quantitative comparisons with experimental data is used to validate the model. Validated numerical models can extend the domain of relevant inputs for process design and optimization.

scholarly journals Performance Analysis of a Multiple Micro-Jet Impingements Cooling Model

2016 ◽  
Vol 15 (2) ◽  
pp. 58
Author(s):  
A. Husain ◽  
N.A. Al-Azri ◽  
A. Samad ◽  
K.Y. Kim
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Temperature Rise ◽  
Reynolds Numbers ◽  
Coefficient Of Performance ◽  
Maximum Temperature ◽  
Temperature Uniformity ◽  
Pumping Power ◽  
Flow Rates ◽  
Maximum Temperature Rise

The present study investigates the thermal performance of a multiple micro-jet impingements model for electronics cooling. The fluid flow and heat transport characteristics were investigated for steady incompressible laminar flow by solving three-dimensional (3D) Navier-Stokes equations. Several parallel and staggered micro-jet configurations (ie. inline 2 Å~ 2, 3 Å~ 3 and 4 Å~ 4 jets, and staggered five-jet and 13-jet arrays with the jet diameter to the channel height ratios from 0.25–0.5) were analyzed at various flow rates for the maximum temperature rise, pressure drop, heat-transfer coefficient, thermal resistance, and pumping power characteristics. The parametric investigation was carried out based on the number of jets and the jet diameters at various mass flow rates and jet Reynolds numbers. Temperature uniformity and coefficient of performance were evaluated to find out the trade-off among the various designs investigated in the present study. The maximum temperature rise and the pressure drop decreased with an increase in the number of jets except in the case of staggered five-jet array. A higher temperature uniformity was observed at higher flow rates with a decrease in the coefficient of performance. The performance parameters, such as thermal resistance and pumping power, showed a conflicting nature with respect to design variables (viz. jet diameter to stand-off ratio and interjet spacing or number of jets) at various Reynolds numbers within the laminar regime. 

Experimental Investigation of Liquid Cooling Through Shallow Copperclad Cavities With Etched Pin-Fin Arrays

2018 ◽  
Author(s):  
Yin Lam ◽  
Nicole Okamoto ◽  
Younes Shabany ◽  
Sang-Joon John Lee
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Surface Area ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Removal ◽  
Heat Sinks ◽  
Liquid Cooling ◽  
Pin Fin ◽  
Pin Fin Arrays

Heat removal is an increasing engineering challenge for higher-density packaging of circuit components. Microchannel heat sinks with liquid cooling have been investigated to take advantage of high surface-to-volume ratio and higher heat capacity of liquids relative to gases. This study experimentally investigated heat removal by liquid cooling through shallow copperclad cavities with staggered pin-fin arrays. Cavities with pin-fins were fabricated by chemical etching of a copperclad layer (nominally 105 μm thick) on a printed-circuit substrate (FR-4). The overall etched cavity was 30 mm wide, 40 mm long, and 0.1 mm deep. The pins were 1.1 mm in diameter and were distributed in a staggered arrangement. The cavity was sealed with a second copperclad substrate using an elastomer gasket. This assembly was then connected to a syringe pump delivery system. Deionized water was used as the working fluid, with volumetric flow rate up to 1.5 mL/min. The heat sink was subjected to a uniform heat flux of 5 W on the underside. Performance of the heat sink was evaluated in terms of pressure drop and the convection thermal resistance. Pressure drop across the heat sinks was less than 10 kPa, dominated by wall surface area rather than the small surface area contributed by cylindrical pins. At low flow rate, caloric thermal resistance dominated the overall thermal resistance of the heat sink. When compared to a microchannel without pins, the pin-fin microchannel reduced convective thermal resistance of the heat sink by approximately a factor of 4.

Performances of Silicon Micro-Flow-Passage Cold Plates From Single-Phase to Two-Phase With Water and HFE-7100 as Working Fluids

2007 ◽  
Author(s):  
Tao Tong ◽  
Je-Young Chang ◽  
Shankar Devasenathipathy ◽  
John Dirner ◽  
Suzana Prstic ◽  
...  
Keyword(s):  
Phase Change ◽  
Flow Boiling ◽  
Ambient Pressure ◽  
Heat Removal ◽  
Operating Conditions ◽  
Working Fluid ◽  
Channel Height ◽  
Two Phase ◽  
Working Fluids ◽  
Cold Plates

Two-phase (phase-change) microchannel (MC) system is a promising technology for achieving enhanced heat removal for highdensity electronics. Yet phase-change studies in MCs with hydraulic diameters on the order of several hundred micrometers or smaller have been inconclusive. Most of earlier studies involved one specific channel design and one type of working fluid. It is thus difficult to make fair comparisons across various experimental works toward recommending the best design option for real applications under specific operating conditions. In the current work, flow boiling experiments were conducted for MC cold plates with channel widths ranging from 61 μm to 330 μm and channel height ∼ 300 μm (hydraulic diameters from ∼ 100 μm to ∼ 337 μm) and a pin-fin array cold plate with fin size and inter-spacing ∼ 150 μm. Two working fluids, deionized water at sub-atmospheric pressure (∼ 25 kPa to 45 kPa) and HFE-7100 at ambient pressure, were tested respectively. High-speed visualization facilities were employed to help understand the rapid phase-change processes inside the flow passages. Pressure drop and heat transfer characteristics of the microchannel cold plates under various heat flux and flow rate conditions were recorded and analyzed as well as boiling fluctuations. Detailed visualization results will be presented in a separate paper [Tong et al., IMECE2007-42028].

Numerical Modeling of Reflux Solar Receivers

1993 ◽  
Vol 115 (2) ◽  
pp. 93-100 ◽  
Author(s):  
R. E. Hogan
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Energy Transfer ◽  
Thermal Resistance ◽  
Numerical Models ◽  
Control Volume ◽  
Operating Conditions ◽  
Working Fluid ◽  
Detailed Model ◽  
Finite Control

Using reflux solar receivers to collect solar energy for dish-Stirling electric power generation systems is presently being investigated by several organizations, including Sandia National Laboratories, Albuquerque, N. Mex. In support of this program, Sandia has developed two numerical models describing the thermal performance of pool-boiler and heat-pipe reflux receivers. Both models are applicable to axisymmetric geometries and they both consider the radiative and convective energy transfer within the receiver cavity, the conductive and convective energy transfer from the receiver housing, and the energy transfer to the receiver working fluid. The primary difference between the models is the level of detail in modeling the heat conduction through the receiver walls. The more detailed model uses a two-dimensional finite control volume method, whereas the simpler model uses a one-dimensional thermal resistance approach. The numerical modeling concepts presented are applicable to conventional tube-type solar receivers, as well as to reflux receivers. Good agreement between the two models is demonstrated by comparing the predicted and measured performance of a pool-boiler reflux receiver being tested at Sandia. For design operating conditions, the receiver thermal efficiencies agree within 1 percent and the average receiver cavity temperature within 1.3 percent. The thermal efficiency and receiver temperatures predicted by the simpler thermal resistance model agree well with experimental data from on-sun tests of the Sandia reflux pool-boiler receiver. An analysis of these comparisons identifies several plausible explanations for the differences between the predicted results and the experimental data.

Trends in the development of flexible thermal protection systems for modern aircraft

2020 ◽  
pp. 10-21
Author(s):  
V. G. Babashov ◽  
◽  
N. M. Varrik ◽  
Keyword(s):  
High Temperature ◽  
Thermal Protection ◽  
Heat Removal ◽  
Operating Conditions ◽  
Passive Protection ◽  
Thermal Protection Systems ◽  
Heat Protection ◽  
Protection Systems ◽  
Protected Surface ◽  
Flexible Panels

The emergence of new types of space and aviation technology necessitates the development of new types of thermal protection systems capable of operating at high temperature and long operating times. There are several types of thermal protection systems for different operating conditions: active thermal protection systems using forced supply of coolant to the protected surface, passive thermal protection systems using materials with low thermal conductivity without additional heat removal, high-temperature systems, which are simultaneously elements of the bearing structure and provide thermal protection, ablation materials. Heat protection systems in the form of rigid tiles and flexible panels, felt and mats are most common kind of heat protecting systems. This article examines the trends of development of flexible reusable heat protection systems intended for passive protection of aircraft structural structures from overheating.

Dynamic analysis of a helical gear reduction by experimental and numerical methods

2020 ◽  
Vol 68 (1) ◽  
pp. 48-58
Author(s):  
Chao Liu ◽  
Zongde Fang ◽  
Fang Guo ◽  
Long Xiang ◽  
Yabin Guan ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Fourth Order ◽  
Numerical Models ◽  
Helical Gear ◽  
Operating Conditions ◽  
Dynamic Responses ◽  
Lumped Mass ◽  
Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

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