Effect of Conjugate Heat Transfer on MEMS-Based Thermal Shear Stress Sensor

2005 ◽  
Author(s):  
Jianghui Chao ◽  
Wei Shyy ◽  
Siddharth S. Thakur ◽  
Mark Sheplak ◽  
Renwei Mei
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Conjugate Heat Transfer ◽  
Stress Measurement ◽  
State Of The Art ◽  
Technical Conference ◽  
Flow Structures ◽  
Thermal Conductivity Ratio ◽  
Electronic Systems ◽  
Physical Mechanisms

The effect of conjugate heat transfer resulting from a Micro-electromechanical Systems (MEMS)-based thermal shear stress is investigated. Due to the length scale disparity and large solid-fluid thermal conductivity ratio, a two-level computation is used to examine the relevant physical mechanisms and their influences on wall shear stress. The substantial variations in transport properties between the fluid and solid phases and their interplay in regard to heat transfer and near-wall fluid flow structures are investigated. It is demonstrated that for the state-of-the-art sensor design, the buoyancy effect can noticeably affect the accuracy of the shear stress measurement.   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.

scholarly journals A finite element analysis on combined convection and conduction in a channel with a thick walled cavity

2014 ◽  
Vol 24 (8) ◽  
pp. 1888-1905 ◽  
Author(s):  
M.M. Rahman ◽  
Hakan Oztop ◽  
S. Mekhilef ◽  
R. Saidur ◽  
A. Chamkha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Mixed Convection ◽  
Conjugate Heat Transfer ◽  
Transfer Problem ◽  
Thick Wall ◽  
Thermal Conductivity Ratio ◽  
Element Analysis ◽  
Content Type ◽  
Combined Convection

Purpose – The purpose of this paper is to examine the effects of thick wall parameters of a cavity on combined convection in a channel. In other words, conjugate heat transfer is solved. Design/methodology/approach – Galerkin weighted residual finite element method is used to solve the governing equations of mixed convection. Findings – The streamlines, isotherms, local and average Nusselt numbers are obtained and presented for different parameters. It is found heat transfer is an increasing function of dimensionless thermal conductivity ratio. Originality/value – The literature does not have mixed convection and conjugate heat transfer problem in a channel with thick walled cavity.

Conjugate heat transfer in porous triangular enclosures with thick bottom wall

2009 ◽  
Vol 19 (5) ◽  
pp. 650-664 ◽  
Author(s):  
Yasin Varol ◽  
Hakan F. Oztop ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Conjugate Heat Transfer ◽  
Bottom Wall ◽  
Thick Wall ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Governing Equations ◽  
Content Type

PurposeThe purpose of this paper is to study the conjugate heat transfer via natural convection and conduction in a triangular enclosure filled with a porous medium.Design/methodology/approachDarcy flow model was used to write governing equations with Boussinesq approximation. The transformed governing equations are solved numerically using a finite difference technique. It is assumed that the enclosure consists of a conducting bottom wall of finite thickness, an adiabatic (insulated) vertical wall and a cooled inclined wall.FindingsFlow patterns, temperature and heat transfer were presented at different dimensionless thickness of the bottom wall, h, from 0.05 to 0.3, different thermal conductivity ratio between solid material and fluid, k, from 0.44 to 283 and Rayleigh numbers, Ra, from 100 to 1000. It is found that both thermal conductivity ratio and thickness of the bottom wall can be used as control parameters for heat transport and flow field.Originality/valueIt is believed that this is the first paper on conduction‐natural convection in porous media filled triangular enclosures with thick wall. In the last years, most of the researchers focused on regular geometries such as rectangular or square cavity bounded by thick wall.

scholarly journals Mixed convection in a channel partially filled with metal foam blocks

2020 ◽  
Vol 330 ◽  
pp. 01044
Author(s):  
Syrine Khadhrawi ◽  
Fakhreddine Segni Oueslati ◽  
Rachid Bennacer
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Metal Foam ◽  
Control Volume ◽  
Velocity Fields ◽  
Flow Structures ◽  
Thermal Conductivity Ratio ◽  
Control Parameters ◽  
Energy Equations ◽  
Control Volume Approach

The present work is a numerical simulation of the mixed convection of an incompressible fluid in a horizontal channel under sun radiation partially filled with metal foam blocks. The Darcy-Brinkman model is adopted. The control volume approach is used to solve the motion and energy equations governing mixed convection. The study focuses on the effect of certain control parameters such as the Rayleigh number (Ra), the thermal conductivity ratio and the porosity on the flow structure and heat transfer. Indeed, the results for flow structures and temperature distribution are presented in the form of velocity fields with streamtraces and isotherms, while the average Nusselt number (Nu) is used to quantify heat transfer.

Conjugate Heat Transfer in Single-Phase Wavy Microchannel

2016 ◽  
Author(s):  
Nishant Tiwari ◽  
Manoj Kumar Moharana ◽  
Sunil Kumar Sarangi
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Flow Rate ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Solid Substrate ◽  
Channel Cross Section ◽  
Thermal Conductivity Ratio ◽  
Substrate Thickness

A three-dimensional numerical study has been carried out to understand the effect of axial wall conduction in a conjugate heat transfer situation in a wavy wall square cross section microchannel engraved on solid substrate whose thickness varying between 1.2–3.6 mm. The bottom of the substrate (1.8 × 30 mm2) is subjected to constant wall heat flux while remaining faces exposed to ambient are assumed to be adiabatic. The vertical parallel walls are considered wavy such that the channel cross section at any axial location will be a square (0.6 × 0.6 mm2) and length of the channel is 30 mm. Wavelength (λ) and amplitude (A) of the wavy channel wall are 12 mm and 0.2 mm respectively. Simulations has been carried out for substrate thickness to channel depth ratio (δsf ∼ 1–5), substrate wall to fluid thermal conductivity ratio (ksf ∼ 0.34–646) and flow rate (Re ∼ 100 to 500). The results show that with increase in flow rate (Re), the hydrodynamic and thermal boundary layers are thinned due to wavy passage and they shifted from the centerline towards the peak which improves the local heat transfer coefficient at the solid-fluid interface. It is also found that after attaining maximum Nuavg at optimum ksf, the slope goes downward with increasing ksf for all set of δsf and flow rate (Re) considered in this study.

Role of Random Roughness on Thermal Performance of Micro-Fins

2005 ◽  
Author(s):  
M. Bahrami ◽  
M. M. Yovanovich ◽  
J. R. Culham
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Technical Conference ◽  
Electronic Systems ◽  
Cross Sectional ◽  
Random Roughness ◽  
Surface Areas ◽  
Isotropic Distribution ◽  
Developed Surface

Heat transfer in rough circular cylinder microfins is studied and a novel analytical model is developed. Surface roughness is assumed to posses a Gaussian isotropic distribution. It is shown that, as a result of roughness, both cross-sectional and surface areas are increased. As a result, an enhancement is observed in the heat transfer rate and thus the thermal performance of microfins. The present model can be implemented to analyze other geometries such as rectangular and tapered microfins.   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.

scholarly journals Effect of Al2O3/water nanofluid on Conjugate Free Convection in a Baffle Attached Square Enclosure

Mechanika ◽  
2020 ◽  
Vol 26 (2) ◽  
pp. 126-133
Author(s):  
Thansekhar M.Rathinam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Rayleigh Number ◽  
Free Convection ◽  
Conjugate Heat Transfer ◽  
Volume Fraction ◽  
Numerical Study ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Square Enclosure

A numerical study of conjugate free convection heat transfer of Al2O3/water nanofluid inside a differentially heated square enclosure with a baffle attached to its hot wall has been carried out. A detailed parametric study has been carried out to analyze the effect of Rayleigh number (104 < Ra < 106), length, thickness and position of baffle, conductivity ratio and volume fraction of the nanoparticle (0<<0.2) on heat transfer. The thermal conductivity ratio of the baffle plays a major role on the conjugate heat transfer inside the enclosure. Higher the baffle length better is the effectiveness of the baffle. The average Nusselt number is found to be an increasing function of both thermal conductivity ratio and volume fraction of the nanofluid. The minimum enhancement of conjugate heat transfer is 30% when Al2O3/water nanofluid of 0.1 volume fraction is used for the entire range of Rayleigh number considered.

scholarly journals Numerical Simulation of Entropy Generation of Conjugate Heat Transfer in A Porous Cavity with Finite Walls and Localized Heat Source

2021 ◽  
Vol 84 (2) ◽  
pp. 116-151
Author(s):  
Ahmed Kadhim Hussein ◽  
Muhaiman Alawi Mahdi ◽  
Obai Younis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Heat Source ◽  
Entropy Production ◽  
Conjugate Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Conductivity Ratio ◽  
Porous Cavity

In this research, the entropy production of the conjugate heat transfer in a tilted porous cavity in respect to heat source and solid walls locations has been studied numerically. Three different cases of the cavity with finite walls thickness and heat source locations are considered in the present study. For both cases one and two, the cavity considered has a vertical finite walls thickness, while the cavity with the horizontal finite walls thickness is considered for case three. For cases one and two, the left sidewall of the cavity is exposed to heat source, whereas the rest of this wall as well as the right sidewall are adiabatic. The upper and lower cavity walls are adiabatic. For case three, the lower wall is exposed to a localized heat source, while the rest of it is assumed adiabatic. The upper wall is cold, whereas the left and right sidewalls are adiabatic. The flow and thermal fields properties along with the entropy production are computed for the modified Rayleigh number (150 ? Ram ? 1000), thermal conductivity ratio (1 ? Kr ? 10), heat source length (0.2 ? B ? 0.6), aspect ratio (0.5 ? AR ? 2) and walls thickness (0.1 ? D1 ? 0.2 and 0.1 ? D2 ? 0.2) respectively. The results show that, the maximum values of the entropy generated from fluid friction develop close to the cavity wall-fluid interfacial, while the maximum values of the entropy generated from heat transfer develop nearby the heat source region. The average Bejan number (Beav) is higher than (0.5) for cases one and two. While for case three, it was found to be less than (0.5). Also, the results show that as the modified Rayleigh number, thermal conductivity ratio, heat source length and aspect ratio increased, the fluid flow intensity in the cavity increased. While, it decreased when the walls thickness increased. From the results, it is concluded that case three gives a higher heat transfer enhancement. The obtained results are compared against another published results and a good agreement is found between them.

Analysis of Pulse Heating on a Fluid-Cooled Surface for Fluid Shear Stress

2002 ◽  
Author(s):  
Kevin D. Cole
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Fluid Shear Stress ◽  
Pulse Heating ◽  
Stress Measurement ◽  
Sensitivity Study ◽  
Transfer Model ◽  
Fluid Shear ◽  
Conduction Model ◽  
Rapid Temperature

This paper is a report of an improved heat transfer model for rapid temperature variations caused by pulse heating of fluid-cooled surfaces, with application to fluid shear-stress measurement. The key improvement is the use of a fully-transient treatment of the heat transfer in the fluid flow as part of a combined convection-conduction model. Surface-temperature results are presented for several fluid/solid combinations for a two-dimensional heater located on the fluid-solid interface. A sensitivity study suggests that pulse heating may be better than steady heating for measurement of fluid shear stress, and that measurements downstream of the heater may also be important.

scholarly journals Conjugate Heat Transfer Analysis of PCM Suspensions in a Circular Tube under External Cooling Convection: Wall Conduction Effects

2020 ◽  
Vol 10 (6) ◽  
pp. 2034 ◽  
Author(s):  
C. J. Ho ◽  
Z.C. Wang ◽  
R.H. Chen ◽  
Chi-Ming Lai
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Conjugate Heat Transfer ◽  
Circular Tube ◽  
Liquid Fraction ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Thermal Conductivity Ratio ◽  
Average Temperature ◽  
External Cooling

In this paper, a numerical method is used to investigate the conjugate heat transfer of a phase change material (PCM) suspension in a circular tube under external cooling convection. The following parameters and ranges were considered: dimensionless tube wall thickness, t w (0–0.5); wall-to-fluid thermal conductivity ratio, k w f * (0.1–10); volumetric fraction of PCM particles, c v (0.1); Biot number, B i o (1); Stefan number, Ste (0.1); and Peclet number, Pe (1000). The results show that the wall thermal conductivity considerably affects the outer/inner wall temperature of the tube, the average temperature of the working fluid, and the volumetric liquid fraction of PCM particles. Thus, wall conduction effects must be properly accounted for to model heat transfer in a PCM suspension in tube flow.

Effect of Conjugate Heat Transfer on MEMS-Based Thermal Shear Stress Sensor

2005 ◽  
Vol 48 (3) ◽  
pp. 197-217 ◽  
Author(s):  
Jianghui Chao ◽  
Wei Shyy ◽  
Siddharth S. Thakur ◽  
Mark Sheplak ◽  
Renwei Mei
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Conjugate Heat Transfer ◽  
Stress Sensor ◽  
Shear Stress Sensor
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