scholarly journals Maximum Temperature and Relaxation Time in Wet Surface Grinding for a General Heat Flux Profile

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
J. L. González-Santander
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Relaxation Time ◽  
Surface Grinding ◽  
Maximum Temperature ◽  
Fast Method ◽  
Workpiece Surface ◽  
Friction Zone ◽  
Flux Profile ◽  
Wet Surface

We solve the boundary-value problem of the heat transfer modeling in wet surface grinding, considering a constant heat transfer coefficient over the workpiece surface and a general heat flux profile within the friction zone between wheel and workpiece. We particularize this general solution to the most common heat flux profiles reported in the literature, that is, constant, linear, parabolic, and triangular. For these cases, we propose a fast method for the numerical computation of maximum temperature, in order to avoid the thermal damage of the workpiece. Also, we provide a very efficient method for the numerical evaluation of the transient regime duration (relaxation time).

scholarly journals Maximum Temperature in Dry Surface Grinding for High Peclet Number and Arbitrary Heat Flux Profile

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
J. L. González-Santander
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Linear Regression ◽  
Peclet Number ◽  
Surface Grinding ◽  
Linear Case ◽  
Maximum Temperature ◽  
Péclet Number ◽  
Asymptotic Expressions ◽  
Flux Profile

Regarding heat transfer in dry surface grinding, simple asymptotic expressions of the maximum temperature for large Peclet numbers are derived. For this purpose, we consider the most common heat flux profiles reported in the literature, such as constant, linear, triangular, and parabolic. In the constant case, we provide a refinement of the expression given in the literature. In the linear case, we derive the same expression found in the literature, being the latter fitted by using a linear regression. The expressions for the triangular and parabolic cases are novel.

scholarly journals A Theorem for Finding Maximum Temperature in Wet Grinding

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
J. L. González-Santander ◽  
G. Martín
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Field ◽  
Integral Form ◽  
Stationary Regime ◽  
Time Dependent ◽  
Maximum Temperature ◽  
Theoretical Computation ◽  
Constant Heat ◽  
Workpiece Surface

We consider the solutions found in the literature for heat transfer in surface grinding, assuming a constant heat transfer coefficient for the coolant acting on the workpiece surface and a constant or linear heat flux profiles entering into the workpiece. From the integral form of the time-dependent temperature field reached in the workpiece, assuming the previous conditions, we prove that the maximum temperature always occurs in the stationary regime on the workpiece surface within the contact zone between the wheel and the workpiece. This result assures a very rapid method for the theoretical computation of the maximum temperature.

scholarly journals Efficient Series Expansions of the Temperature Field in Dry Surface Grinding for Usual Heat Flux Profiles

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Juan Luis González-Santander
Keyword(s):  
Heat Flux ◽  
Temperature Field ◽  
Numerical Evaluation ◽  
Numerical Procedure ◽  
Constant Heat Flux ◽  
Surface Grinding ◽  
Maximum Temperature ◽  
Series Expansions ◽  
Constant Heat ◽  
Flux Profile

In the framework of Jaeger’s model for heat transfer in dry surface grinding, series expansions for calculating the temperature field, assuming constant, linear, triangular, and parabolic heat flux profiles entering into the workpiece, are derived. The numerical evaluation of these series is considerably faster than the numerical integration of Jaeger’s formula and as accurate as the latter. Also, considering a constant heat flux profile, a numerical procedure is proposed for the computation of the maximum temperature as a function of the Peclet number and the depth below the surface. This numerical procedure has been used to evaluate the accuracy of Takazawa’s approximation.

Performance Comparison of Microchannel Heat Sink Using Boron-Based Ceramic Materials

2021 ◽  
Vol 1163 ◽  
pp. 73-88
Author(s):  
Md Tanbir Sarowar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Sink ◽  
Electronic Devices ◽  
Ceramic Materials ◽  
Substrate Material ◽  
Heat Sinks ◽  
Maximum Temperature ◽  
Microchannel Heat Sink ◽  
Small Surface

Microchannel heat sink plays a vital role in removing a considerable amount of heat flux from a small surface area from different electronic devices. In recent times, the rapid development of electronic devices requires the improvement of these heat sinks to a greater extent. In this aspect, the selection of appropriate substrate materials of the heat sinks is of vital importance. In this paper, three boron-based ultra-high temperature ceramic materials (ZrB2, TiB2, and HfB2) are compared as a substrate material for the microchannel heat sink using a numerical approach. The fluid flow and heat transfer are analyzed using the finite volume method. The results showed that the maximum temperature of the heat source didn’t exceed 355K at 3.6MWm-2 for any material. The results also indicated HfB2 and TiB2 to be more useful as a substrate material than ZrB2. By applying 3.6 MWm-2 heat flux at the source, the maximum obtained surface heat transfer coefficient was 175.2 KWm-2K-1 in a heat sink having substrate material HfB2.

Numerical Investigation of a Confined Laminar Jet Impingement Cooling of Heat Sources Using Nanofluids

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Orkodip Mookherjee ◽  
Shantanu Pramanik ◽  
Uttam Kumar Kar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Base Fluid ◽  
Strong Dependence ◽  
Jet Impingement ◽  
Effective Density ◽  
Eckert Number ◽  
Maximum Temperature ◽  
Pumping Power

Abstract The thermal and fluid dynamic behavior of a confined two-dimensional steady laminar nanofluid jet impinging on a horizontal plate embedded with five discrete heating elements subjected to a constant surface heat flux has been studied for a range of Reynolds number (Re) from 100 to 400 with Prandtl number, Pr = 6.96, of the base fluid. Variation of inlet Reynolds number produces a significant change of the flow and heat transfer characteristics in the domain. Increasing the nanoparticle concentration (ϕ) from 0% to 4% exhibits discernible change in equivalent Re and Pr caused by the modification of dynamic viscosity, effective density, thermal conductivity, and specific heat of the base fluid. Considerable improvement in heat transfer from the heaters is observed as the maximum temperature of the impingement wall is diminished from 0.95 to 0.55 by increasing Re from 100 to 400; however, the result of increasing ϕ on cooling of the heaters is less appreciable. Self-similar behavior has been depicted by cross-stream variation of temperature and streamwise heat flux in the developed region along the impingement wall up to Re = 300 for ϕ=0% to 4%. But the spread of the respective quantities shows strong dependence on ϕ at Re = 300 with sudden attenuation in magnitude in the developed region of flow. Substantial influence of Re is evident on Eckert number and pumping power. Eckert number decreases, whereas pumping power increases with an increase in Re, and the respective variations exhibit correspondence with power fit correlations.

Measurements of Sheath Temperature Profiles in Bruce LVRF Bundles Under Post-Dryout Heat Transfer Conditions in Freon

2006 ◽  
Author(s):  
Y. Guo ◽  
D. E. Bullock ◽  
I. L. Pioro ◽  
J. Martin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Uranium ◽  
Outer Ring ◽  
Maximum Temperature ◽  
Experimental Program ◽  
Uniform Heat Flux ◽  
Flow Conditions ◽  
Channel Power ◽  
Ring Element

An experimental program has been completed to study the behaviour of sheath wall temperatures in the Bruce Power Station Low Void Reactivity Fuel (shortened hereafter to Bruce LVRF) bundles under post-dryout (PDO) heat-transfer conditions. The experiment was conducted with an electrically heated simulator of a string of nine Bruce LVRF bundles, installed in the MR-3 Freon heat transfer loop at the Chalk River Laboratories (CRL), Atomic Energy of Canada Limited (AECL). The loop used Freon R-134a as a coolant to simulate typical flow conditions in CANDU® nuclear power stations. The simulator had an axially uniform heat flux profile. Two radial heat flux profiles were tested: a fresh Bruce LVRF profile and a fresh natural uranium (NU) profile. For a given set of flow conditions, the channel power was set above the critical power to achieve dryout, while heater-element wall temperatures were recorded at various overpower levels using sliding thermocouples. The maximum experimental overpower achieved was 64%. For the conditions tested, the results showed that initial dryout occurred at an inner-ring element at low flows and an outer-ring element facing internal subchannels at high flows. Dry-patches (regions of dryout) spread with increasing channel power; maximum wall temperatures were observed at the downstream end of the simulator, and immediately upstream of the mid-bundle spacer plane. In general, maximum wall temperatures were observed at the outer-ring elements facing the internal subchannels. The maximum water-equivalent temperature obtained in the test, at an overpower level of 64%, was significantly below the acceptable maximum temperature, indicating that the integrity of the Bruce LVRF will be maintained at PDO conditions. Therefore, the Bruce LVRF exhibits good PDO heat transfer performance.

A Computational Study of Strongly Heated Internal Hydrogen Flow Under Non-Uniform Heat Flux

2018 ◽  
Author(s):  
Yu Ji ◽  
Jun Sun ◽  
Lei Shi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Computational Study ◽  
Uniform Heat Flux ◽  
High Heat Flux ◽  
Hydrogen Flow ◽  
Flow Acceleration ◽  
Internal Hydrogen ◽  
High Dependency ◽  
Flux Profile

Nuclear thermal propulsion (NTP) systems is regarded as a promising technology for human space exploration in the near future due to its large thrust and high specific impulse. Hydrogen serves as both the system coolant and engine propellant here. Convective heat transfer to hydrogen flow is a complicated process accompanying large properties variation of hydrogen due to high heat flux. In this paper, the strongly heated internal hydrogen flow is investigated numerically. According to the previous work, it has been found that the standard k-ε model with the assistance of enhanced wall treatment shows the excellent agreement with the experimental data. Based on this validated approach, the effects of heat flux profile on flow and heat transfer characteristics are evaluated. Results show high dependency of the thermal hydraulics characteristics such as wall temperature distribution and heat transfer coefficient on the heat flux profile imposed at the tube wall. Besides, the results suggest that the flow acceleration to a flat velocity profile contributes to the heat transfer deterioration, while the distorted velocity to “M-shape” is considered to be more often related to the recovery of turbulence production and subsequent heat transfer.

Development of Empirical Equations for Irradiance Profile of a Standard Parabolic Trough Collector Using Monte Carlo Ray Tracing Technique

2013 ◽  
Vol 860-863 ◽  
pp. 180-190 ◽  
Author(s):  
Majedul Islam ◽  
M. A. Karim ◽  
Suvash C. Saha ◽  
Sarah Miller ◽  
Prasad K. D. V. Yarlagadda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Monte Carlo ◽  
Conjugate Heat Transfer ◽  
Large Range ◽  
Published Data ◽  
Empirical Equations ◽  
Parabolic Trough ◽  
Test Conditions ◽  
Flux Profile

This article explains a technique in which equations are developed to produce the irradiance profile around the receiver of LS2 collector using a vigorouslyverified MCRT model. A large range of test conditions including daily normal insolation, selective coatings and glass envelop conditions were chosen from the published data by Dudley et al. [1] for the job. The R2value is excellent that varies between 0.9857 and 0.9999. Therefore, these equations can be used confidently to produce boundary heat flux profile of the collector at normal incident for conjugate heat transfer analyses of the receiver.

On Heat Transfer Measurements in Diesel Engines Using Fast-Response Coaxial Thermocouples

1989 ◽  
Vol 111 (3) ◽  
pp. 458-465 ◽  
Author(s):  
D. N. Assanis ◽  
E. Badillo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Diesel Engines ◽  
Fast Response ◽  
Rate Of Change ◽  
Thin Film Thickness ◽  
Flux Profile ◽  
Surface Thermocouple ◽  
Engine Components ◽  
Thermocouple Junction

Finite element models of fast-response CO-AX thermocouples typically used for heat transfer measurements in diesel engines have been developed. Due to the small differences in thermal properties between the thermoelements and the iron engine components, CO-AX thermocouples are capable of measuring transient temperatures of iron components within an accuracy of 98 percent. However, these relatively small errors in temperature measurement result in as high as 25 percent errors in peak surface heat flux calculations. This implies that heat flux results depend not only on the temperature of the surface thermocouple junction, but are also sensitive to its time rate of change. Increasing the thin film thickness can significantly alter the heat flux profile deduced from surface junction temperatures.

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