Transient Heat Transfer in Microscale Porous Materials Heated by Microsecond Laser Pulse of High Power Density

2002 ◽  
Author(s):  
Fangming Jiang ◽  
Dengying Liu ◽  
Jim S.-J. Chen ◽  
Richard S. Cohen
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Laser Pulse ◽  
Power Density ◽  
High Power ◽  
Hyperbolic Model ◽  
Transient Temperature ◽  
Hyperbolic Heat Conduction ◽  
High Power Density ◽  
High Heat Transfer

A novel experimental method was developed to measure the rapid transient temperature variations (heating rate > 107 K/s) of porous samples heated by high surface heat fluxes. With a thin film (0.1 μm thick) resistance thermometer of platinum as the temperature sensor and a super-high speed digital oscilloscope (up to 100 MHz) as the data recorder, rapid transient temperature variation in a porous material heated by a microsecond laser pulse of high power density is measured. Experimental results indicate that for high heat transfer cases (q′ > 109 W/m2) with short durations (5 – 20 μs) of heating, non-Fourier heat conduction behaviors appear. The non-Fourier hyperbolic heat conduction model and the traditional Fourier parabolic model are employed to simulate this thermal case respectively and the FDM is used to perform the numerical analysis. The hyperbolic model predicts thermal wave behavior in qualitative agreement with the experimental data.

Enhanced Miniature Loop Heat Pipe Cooling System for High Power Density Electronics

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
J. H. Choi ◽  
B. H. Sung ◽  
J. H. Yoo ◽  
C. J. Kim ◽  
D.-A. Borca-Tasciuc
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Power Density ◽  
Thermal Performance ◽  
High Power ◽  
Design Stage ◽  
Working Fluid ◽  
High Power Density ◽  
Graphic Processing Units ◽  
Maximum Heat

The implementation of high power density, multicore central and graphic processing units (CPUs and GPUs) coupled with higher clock rates of the high-end computing hardware requires enhanced cooling technologies able to attend high heat fluxes while meeting strict design constrains associated with system volume and weight. Miniature loop heat pipes (mLHP) emerge as one of the technologies best suited to meet all these demands. Nonetheless, operational problems, such as instable behavior during startup on evaporator side, have stunted the advent of commercialization. This paper investigates experimentally two types of mLHP systems designed for workstation CPUs employing disk shaped and rectangular evaporators, respectively. Since there is a strong demand for miniaturization in commercial applications, emphasis was also placed on physical size during the design stage of the new systems. One of the mLHP system investigated here is demonstrated to have an increased thermal performance at a reduced system weight. Specifically, it is shown that the system can reach a maximum heat transfer rate of 170 W with an overall thermal resistance of 0.12 K/W. The corresponding heat flux is 18.9 W/cm2, approximately 30% higher than that of larger size commercial systems. The studies carried out here also suggest that decreasing the thermal resistance between the heat source and the working fluid and maximizing the area for heat transfer are keys for obtaining an enhanced thermal performance.

Numerical Simulation of Heat Transfer and Fluid Flow of a Flat-Tube High Power Density Solid Oxide Fuel Cell

2004 ◽  
Vol 2 (1) ◽  
pp. 65-69 ◽  
Author(s):  
Yixin Lu ◽  
Laura Schaefer ◽  
Peiwen Li
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Power Density ◽  
High Power ◽  
Solid Oxide ◽  
High Power Density ◽  
Oxide Fuel ◽  
Flat Tube

To both increase the power density of a tubular solid oxide fuel cell (SOFC) and maintain its beneficial feature of secure sealing, a flat-tube high power density (HPD) solid oxide fuel cell is under development by Siemens Westinghouse, based on their formerly developed tubular model. In this paper, a three dimensional numerical model to simulate the steady state heat transfer and fluid flow of a flat-tube HPD–SOFC is developed. A computer code is programmed using the FORTRAN language to solve the governing equations for continuity, momentum, and energy conservation. The highly coupled temperature and flow fields of the air stream and the fuel stream inside and outside a typical channel of a one-rib flat-tube HPD–SOFC are investigated. This heat transfer and fluid flow results will be used to simulate the overall performance of a flat-tube HPD–SOFC in the near future, and to help optimize the design and operation of a SOFC stack in practical applications.

scholarly journals Recent Advancements in Thermal Performance Enhancement in Microchannel Heatsinks for Electronic Cooling Application

2021 ◽  
Author(s):  
Naga Ramesh Korasikha ◽  
Thopudurthi Karthikeya Sharma ◽  
Gadale Amba Prasad Rao ◽  
Kotha Madhu Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Density ◽  
High Power ◽  
Performance Enhancement ◽  
Electronic Cooling ◽  
Heat Sinks ◽  
High Power Density ◽  
Transfer Enhancement ◽  
Microchannel Heat Sinks

Thermal management of electronic equipment is the primary concern in the electronic industry. Miniaturization and high power density of modern electronic components in the energy systems and electronic devices with high power density demanded compact heat exchangers with large heat dissipating capacity. Microchannel heat sinks (MCHS) are the most suitable heat exchanging devices for electronic cooling applications with high compactness. The heat transfer enhancement of the microchannel heat sinks (MCHS) is the most focused research area. Huge research has been done on the thermal and hydraulic performance enhancement of the microchannel heat sinks. This chapter’s focus is on advanced heat transfer enhancement methods used in the recent studies for the MCHS. The present chapter gives information about the performance enhancement MCHS with geometry modifications, Jet impingement, Phase changing materials (PCM), Nanofluids as a working fluid, Flow boiling, slug flow, and magneto-hydrodynamics (MHD).

Full Scale Simulation of an Integrated Monolithic Heat Sink for Thermal Management of a High Power Density GaN-SiC Chip

2015 ◽  
Author(s):  
Tanya Liu ◽  
Farzad Houshmand ◽  
Catherine Gorle ◽  
Sebastian Scholl ◽  
Hyoungsoon Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Power Density ◽  
Mass Flow ◽  
High Power ◽  
Heat Sink ◽  
High Power Density ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Insight Into

Advances in manufacturing techniques are inspiring the design of novel integrated microscale thermal cooling devices seeking to push the limits of current thermal management solutions in high heat flux applications. These advanced cooling technologies can be used to improve the performance of high power density electronics such as GaN-based RF power amplifiers. However, their optimal design requires careful analysis of the combined effects of conduction and convection. Many numerical simulations and optimization studies have been performed for single cell models of microchannel heat sinks, but these simulations do not provide insight into the flow and heat transfer through the entire device. This study therefore presents the results of conjugate heat transfer CFD simulations for a complex copper monolithic heat sink integrated with a 100 micron thick, 5 mm by 1 mm high power density GaN-SiC chip. The computational model (13 million cells) represents both the chip and the heat sink, which consists of multiple inlets and outlets for fluid entry and exit, delivery and collection manifold systems, and an array of fins that form rectangular microchannels. Total chip powers of up to 150 W at the GaN gates were considered, and a quarter of the device was modeled for total inlet mass flow rates of 1.44 g/s and 1.8 g/s (0.36 g/s and 0.45 g/s for the quarter device), corresponding to laminar flow at Reynolds numbers between 19.5 and 119.3. It was observed that the mass flow rates through individual microchannels in the device vary by up to 45%, depending on the inlet/outlet locations and pressure drop in the manifolds. The results demonstrate that full device simulations provide valuable insight into the multiple parameters that affect cooling performance.

scholarly journals Nuclear Navy

2004 ◽  
Vol 126 (01) ◽  
pp. 30-36
Author(s):  
Frank Wicks
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
High Power ◽  
Food Supply ◽  
Nuclear Power ◽  
High Power Density ◽  
Atomic Weapons ◽  
Air Breathing ◽  
Nuclear Propulsion ◽  
Promotion Process

This article discusses how atomic weapons had been the vision and accomplishment of physicists. The very limited space available would require a high power-density reactor and would present unprecedented heat transfer challenges. Diesel electric submarines had to surface to run air breathing engines, which needed to charge their batteries. Range and submerged time of a submarine with a reliable nuclear propulsion system would be limited only by food supply and endurance of the crew. The rumor among the first nuclear submariners was that they would surface every 4 years to reenlist. The reason that the submarine was the first application of controlled nuclear power is a tribute to the vision of another man. Back in 1953, while the Nautilus was being constructed, Rickover’s naval career appeared to be over. The Navy’s promotion process was not favorable for an engineering duty officer. Nuclear power put Rickover even farther out of the promotion mainstream.

Two-Dimensional Vibrating And Thermal Response of Skin Tissue To Different Types of Heat Sources Considering The Hyperbolic Heat Transfer Equation

2021 ◽  
Author(s):  
Mina Ghanbari ◽  
Ghader Rezazadeh
Keyword(s):  
Heat Transfer ◽  
Differential Equation ◽  
Heat Conduction ◽  
Boundary Conditions ◽  
Skin Tissue ◽  
Transient Temperature ◽  
Hyperbolic Heat Conduction ◽  
Two Dimensional ◽  
Thermomechanical Response ◽  
Different Types

Abstract Laser-induced thermal therapy, due to its applications in various clinical treatments, has become an efficient alternative, especially for skin ablation. In this work, the two-dimensional thermomechanical response of skin tissue subjected to different types of thermal loading is investigated. Considering the thermoelastic coupling term, the two-dimensional differential equation of heat conduction in the skin tissue based on the Cattaneo–Vernotte heat conduction law is presented. The two-dimensional differential equation of the tissue displacement coupled with the two-dimensional hyperbolic heat conduction equation of tissue is solved simultaneously to analyze the thermal and mechanical response of the skin tissue. The existence of mixed complicated boundary conditions makes the problem so complex and intricate. The Galerkin-based reduced-order model has been utilized to solve the two-sided coupled differential equations of skin displacement and heat transfer with accompanying complicated boundary conditions. The effect of various types of heating sources such as thermal shock, single and repetitive pulses, repeating sequence stairs, ramp-type, and harmonic-type heating, on the thermomechanical response of the tissue is investigated. The temperature distribution in the tissue along the depth and radial direction is also presented. The transient temperature and displacement response of tissue considering different relaxation times are studied, and the results are discussed in detail.

A Comparative Study of Cooling of High Power Density Electronics Using Sprays and Microjets

2005 ◽  
Vol 127 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Matteo Fabbri ◽  
Shanjuan Jiang ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
High Power ◽  
Cooling System ◽  
Heat Removal ◽  
Impinging Jets ◽  
Heat Fluxes ◽  
Test Fluid ◽  
High Power Density ◽  
Cooling Module

Direct cooling by means of jets and sprays has been considered as a solution to the problem of cooling of high power density electronic devices. Although both methods are capable of very high heat removal rates no criterion exists that helps one decide as to which one is preferable, when designing a cooling system for electronic applications. In this work, the results of an investigation of the performances of sprays and arrays of micro jets are reported. Experiments have been conducted using HAGO nozzles and orifice plates to create droplet sprays and arrays of micro jets, respectively. The liquid jets had diameters ranging from 69 to 250 μm and the pitches between the jets were 1, 2, and 3 mm. The test fluid was deionized water and the jet Reynolds number ranged between 43 and 3813. A comparison of heat transfer and pressure drop results obtained employing both sprays and jets has been carried out. The microjet arrays proved superior to the sprays since they required less pumping power per unit of power removed. A cooling module employing impinging jets was tested. Such a module would require three primary components: an orifice plate for forming jets or a nozzle to form the spray; a container to hold the nozzle, the heat source and the cooling liquid, which also serves as a heat exchanger to the ambient; and a pump which recirculates the coolant. A fan could be used to improve the heat transfer to the ambient, and it would allow the use of a smaller container. An impinging jets cooling module has been designed and tested. Heat fluxes as high as 300 W/cm2 at 80°C surface temperature could be removed using a system which includes a 4×6 array of microjets of water of 140 μm diameter impinging on a diode 5.0×8.7 mm2.

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