Characteristics of the Dimensionless Temperature in Tubes With Axial Wall Heat Conduction

2017 ◽  
Author(s):  
Mei Lin ◽  
Shi-cong Li ◽  
Xue-fang Xu ◽  
Qiu-wang Wang
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Peclet Number ◽  
Circular Tube ◽  
Working Fluid ◽  
Dimensionless Temperature ◽  
Uniform Heat Flux ◽  
Wall Surface ◽  
Péclet Number ◽  
Inner Diameter

Characteristics of the dimensionless temperature, θ, are performed to investigate in laminar circular tube flow by numerical simulation with the presence of axial heat conduction. A uniform heat flux is imposed on outside wall surface. The smallest inner diameter of circular tube is only 200 μm. The heat transfer and flow can be described by traditional Navier-Stokes and energy equations. The results shows that θ is identical under the condition of different specified heat flux on the outside wall surface at the same Peclet number. Furthermore, the dimensionless temperature at the tube entrance θ(0) is independent on wall thickness, tube material, working fluid and boundary condition. Hence, the dimensionless temperature at the tube entrance θ(0) is only a function of Peclet number and the corresponding correlation of θ(0) in circular tube is obtained from numerical results and validated by other available cases. Moreover, the correlation of θ(0) is also applied with different cross-sectional shapes of heated solid surface when inner diameter of fluid region is not less than 2.0 mm.

Modeling temperature rise in multi-track reciprocating frictional sliding

2021 ◽  
pp. 135065012098823
Author(s):  
Thierry A Blanchet
Keyword(s):  
Temperature Rise ◽  
Peclet Number ◽  
Maximum Temperature ◽  
Uniform Heat Flux ◽  
Heat Accumulation ◽  
Stroke Length ◽  
Péclet Number ◽  
Maximum Temperature Rise ◽  
Rectangular Patch ◽  
Accumulation Effect

As in various manufacturing processes, in sliding tests with scanning motions to extend the sliding distance over fresh countersurface, temperature rise during any pass is bolstered by heating during prior passes over neighboring tracks, providing a “heat accumulation effect” with persisting temperature rises contributing to an overall temperature rise of the current pass. Conduction modeling is developed for surface temperature rise as a function of numerous inputs: power and size of heat source; speed and stroke length, and track increment of scanning motion; and countersurface thermal properties. Analysis focused on mid-stroke location for passes of a square uniform heat flux sufficiently far into the rectangular patch being scanned from the first pass at its edge that steady heat accumulation effect response is adopted, focusing on maximum temperature rise experienced across the pass' track. The model is non-dimensionalized to broaden the applicability of the output of its runs. Focusing on practical “high” scanning speeds, represented non-dimensionally by Peclet number (in excess of 40), applicability is further broadened by multiplying non-dimensional maximum temperature rise by the square root of Peclet number as model output. Additionally, investigating model runs at various non-dimensional speed (Peclet number) and reciprocation period values, it appears these do not act as independent inputs, but instead with their product (non-dimensional stroke length) as a single independent input. Modified maximum temperature rise output appears to be a function of only two inputs, increasing with decreasing non-dimensional values of stroke length and scanning increment, with outputs of models runs summarized compactly in a simple chart.

Numerical study of the flow of R1270‐based nanorefrigerants in a circular tube subject to uniform heat flux

2018 ◽  
Vol 13 (12) ◽  
pp. 1693-1698 ◽  
Author(s):  
Mohammed Zohud ◽  
Ahmed Ouadha ◽  
Redouane Benzeguir
Keyword(s):  
Heat Flux ◽  
Circular Tube ◽  
Numerical Study ◽  
Uniform Heat Flux ◽  
Uniform Heat

Experimental and Numerical Investigation on Natural Convection in Horizontal Channels Partially Filled With Aluminium Foam and Heated From Below

2016 ◽  
Author(s):  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini ◽  
Alessandra Diana
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Wall Temperature ◽  
Aluminum Foam ◽  
Rectangular Channel ◽  
Lower Surface ◽  
Heated Wall ◽  
Working Fluid ◽  
Bottom Plate ◽  
Uniform Heat Flux

Natural convection in horizontal rectangular channel without or with aluminum foam is experimentally and numerically investigated. In the case with aluminum foam the channel is partially filled. In both cases, the bottom wall of the channel is heated at a uniform heat flux and the upper wall is unheated and it is not thermally insulated to the external ambient. The experiments are performed with working fluid air. Different values of wall heat flux at lower surface are considered in order to obtain some Grashof numbers and different heated wall temperature distributions. Two different aluminum foams are considered in the experimental investigation, one from “M-pore”, with 10 and 30 pore per inch (PPI), and the other one from “ERG”, with 10, 20 and 40 PPI. The numerical simulation is carried out by a simplified two-dimensional model. It is found that the heat transfer is better when the channel is partially filled and the emissivity is low, whereas the heated wall temperature values are higher when the channel is partially filled and the heated bottom plate has high emissivity. The investigation is achieved also by flow visualization which is carried out to identify the main flow shape and development and the transition region along the channel. The visualization of results, both experimental and numerical, grants the description of secondary motions in the channel.

Submerged Jet Impingement Boiling on a Polished Silicon Surface

2011 ◽  
Author(s):  
Preeti Mani ◽  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Silicon Surface ◽  
High Speed ◽  
Jet Impingement ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Submerged Jet ◽  
Jet Impingement Boiling

Submerged jet impingement boiling has the potential to enhance pool boiling heat transfer rates. In most practical situations, the surface could consist of multiple heat sources that dissipate heat at different rates resulting in a surface heat flux that is non-uniform. This paper discusses the effect of submerged jet impingement on the wall temperature characteristics and heat transfer for a non-uniform heat flux. A mini-jet is caused to impinge on a polished silicon surface from a nozzle having an inner diameter of 1.16 mm. A 25.4 mm diameter thin-film circular serpentine heater, deposited on the bottom of the silicon wafer, is used to heat the surface. Deionized degassed water is used as the working fluid and the jet and pool are subcooled by 20°C. Voltage drop between sensors leads drawn from the serpentine heater are used to identify boiling events. Heater surface temperatures are determined using infrared thermography. High-speed movies of the boiling front are recorded and used to interpret the surface temperature contours. Local heat transfer coefficients indicate significant enhancement upto radial locations of 2.6 jet diameters for a Reynolds number of 2580 and upto 6 jet diameters for a Reynolds number of 5161.

Numerical and Experimental Analysis of Twisted Tape Insert in Circular Tube

2019 ◽  
Author(s):  
V. S. Chandratre ◽  
A. A. Keste ◽  
N. K. Sane
Keyword(s):  
Heat Flux ◽  
Experimental Analysis ◽  
Test Section ◽  
Circular Tube ◽  
Uniform Heat Flux ◽  
Internal Diameter ◽  
Twisted Tape ◽  
Outer Diameter ◽  
Nusselt Numbers ◽  
Area Of Concern

Abstract Energy is a major area of concern for many industrial and engineering applications. For the development of energy efficient heat exchangers, heat transfer enhancement by passive inserts have growing research potential. The present study gives the numerical and experimental analysis of twisted tape insert in a circular tube for the range of Reynolds number between 5000 to 15000 with heat flux variation from 500W/m2 to 1.5 kW/m2 with air as working medium. A circular tube of 52.5 mm internal diameter, 60 mm outer diameter and 1000 mm length is used as test section with uniform heat flux. Twisted tape used is of Aluminum material having a pitch of 100 mm. Outside surface temperatures are measured at different locations on test section. Two ‘T’ type thermocouples are used to measure air temperature at inlet and outlet of test section. From numerical and experimental analysis it is observed that the Nusselt number increases for twisted tape as compared to smooth bare tube by 2.2–3.1 times. Again the Nusselt numbers obtained for smooth tube is compared with Dittus-Boelter and Gnielinski correlation and it is observed that the error is within acceptable limit of 10% variation. An error of 10% variation is observed in friction factor obtained by experimental analysis and Blasius and Petukov correlations.

Time Estimate for the Incipient Surface Melting of Regular-Shaped Metals Receiving Uniform Heat Flux Inside a Metal Melting Furnace

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Marcelo D. Marucho ◽  
Antonio Campo ◽  
N. Ben Cheikh
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Melting Furnace ◽  
Continuous Heating ◽  
Uniform Heat Flux ◽  
Large Plate ◽  
Time Solution ◽  
Uniform Heat ◽  
Metal Melting ◽  
Long Cylinder

This article addresses the continuous heating of regular-shaped metals (large plate, long cylinder, and sphere) at ambient temperature placed in a metal melting furnace. Under the assumption of temperature-independent thermophysical properties of the metal, the heat conduction problem entails to unsteady one-dimensional (1D) heat conduction with a boundary condition of uniform heat flux. Based on the exact, analytic spatiotemporal temperature distributions for the regular-shaped metals, the objective of this study is to construct simple predictive formulas so that engineers can estimate the incipient melting of these metals when heated continually. The time at which melting at the metal surface is initiated, tmelt, corresponds to setting the surface temperature, Tsur, equal to the melting temperature, Tmelt. The analysis will be done under the premises of two asymptotic solutions: one a “large-time” solution and the other a “short-time” solution. A collection of six formulas of simple form for predicting the melting time, tmelt, will be developed for those regular-shaped metals (large plate, long cylinder, and sphere).

Peclet Number Behaviour on the 1-D Heat Conduction-Convection Problem With a Control Volume Capacitance Method

Materials ◽  
2003 ◽  
Author(s):  
N. J. Rodri´guez ◽  
K. Davey ◽  
P. M. V. Castillo
Keyword(s):  
Heat Conduction ◽  
Peclet Number ◽  
Control Volume ◽  
Research Attention ◽  
Péclet Number ◽  
Moving Grids ◽  
Numerical Tests ◽  
Capacitance Method ◽  
Convection Problem ◽  
And Performance

Modelling of solidification with transport of mass is of paramount importance for the heat transfer community. Phase change problems have received considerable research attention over the last two decades. Numerical methods for fixed and moving grids have been developed with increasing accuracy and performance, although fundamental aspects still elude modeling such as numerical oscillations. The discovery of Control Volume Capacitance Methods (CVCM) is an attempt to eliminate the need to use classical Petrov-Galerkin and Bubnov-Galerkin formulations. The theory underpinning CVCM methods is presented. A novel modified CVCM is presented which is transformable into a FEM that is similar to that used to model heat-conduction. The method is applied to the 1-D semi-infinite problem, where mesh is spatially fixed whilst mass is transported, in order to investigate the Peclet number behavior. Numerical tests are compared against analytical solutions; the approach is shown to be accurate, stable and computationally competitive.

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