On the Accuracy of Beam-Averaged Interferometric Heat Transfer Measurements

2002 ◽  
Vol 124 (5) ◽  
pp. 978-982 ◽  
Author(s):  
D. Naylor
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Laser Interferometry ◽  
Fringe Field ◽  
Fluid Temperature ◽  
Object Beam ◽  
Ideal Gases

Laser interferometry can be used in a three dimensional temperature field to measure the average fluid temperature and heat transfer rate, integrated over the length of an experimental model. However, such measurements are inherently approximate when the surface temperature varies in the direction of the test/object beam. In this study an analysis is performed to determine the accuracy of beam-averaged heat transfer rate measurements made in ideal gases. Two analysis methods are considered. The first method is based on extrapolation of the near-wall temperature field to obtain the surface gradient. In the second method, the temperature gradient at the surface is obtained directly from the gradient of the fringe field. The results show that the intrinsic error in the measurements depends strongly upon the form and magnitude of the temperature variation in the light beam direction. Although the error in the measured heat transfer rate is shown to be small for many commonly encountered conditions, it can be greater than ten percent in extreme cases.

An Analysis of Beam-Averaged Interferometric Heat Transfer Measurements

2001 ◽  
Author(s):  
D. Naylor
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Temperature Variation ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Laser Interferometry ◽  
Beam Direction ◽  
Object Beam ◽  
Average Temperature ◽  
Ideal Gases

Abstract Laser interferometry can be used to measure the average temperature field in a fluid, integrated over the length of an experimental model. However, such measurements are inherently approximate when there is a temperature variation in the direction of the test/object beam. The present study examines the accuracy of beam-averaged interferometric measurements made in ideal gases. An analysis is performed to determine the accuracy of both beam-averaged temperature and heat transfer rate measurements. The heat transfer results are obtained for simulated measurements of forced convection from a plate with a power function temperature variation in the beam direction. The results show that the error in the beam-averaged temperature field is less small, even for the most adverse temperature distribution in the light beam direction. However, it was found that the error in the beam-averaged heat transfer rate can be greater than ten percent for some conditions.

A Numerical Study of Three-Dimensional Natural Convective Heat Transfer From a Plate With a “Wavy” Surface

2001 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Matt Garrett
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Surface Waves ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Wavy Surface ◽  
Surface Waviness ◽  
Dimensionless Amplitude ◽  
The Mean

Abstract Natural convective heat transfer from a wide isothermal plate which has a “wavy” surface, i.e., has a surface which periodically rises and falls, has been numerically studied. The surface waves run parallel to the direction of flow over the surface and have a relatively small amplitude. Two types of wavy surface have been considered here — saw-tooth and sinusoidal. Surfaces of the type considered are approximate models of situations that occur in certain window covering applications, for example, and are also sometimes used to try to enhance the heat transfer rate from the surface. The flow has been assumed to be laminar. Because the surface waves are parallel to the direction of flow, the flow over the surface will be three-dimensional. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. The governing equations have been written in dimensionless form, the height of the surface being used as the characteristic length scale and the temperature difference between the surface temperature and the temperature of the fluid far from the plate being used as the characteristic temperature. The dimensionless equations have been solved using a finite-element method. Although the flow is three-dimensional because the surface waves are all assumed to have the same shape, the flow over each surface thus being the same, and it was only necessary to solve for the flow over one of the surface waves. The solution has the following parameters: the Grashof number based on the height, the Prandtl number, the dimensionless amplitude of the surface waviness, the dimensionless pitch of the surface waviness, and the form of the surface waviness (saw-tooth or sinusoidal). Results have been obtained for a Prandtl number of 0.7 for Grashof numbers up to 106. The effects of Grashof number, dimensionless amplitude and dimensionless pitch on the mean heat transfer rate have been studied. It is convenient to introduce two mean heat transfer rates, one based on the total surface area and the other based on the projected frontal area of the surface. A comparison of the values of these quantities gives a measure of the effectiveness of the surface waviness in increasing the mean heat transfer rate. The results show that while surface waviness increases the heat transfer rate based on the frontal area, the modifications of the flow produced by the surface waves are such that the increase in heat transfer rate is less than the increase in surface area.

Finite Element Analysis about the Influence that High-Speed Motorized Spindle Spindle System Material has on its Temperature Field

2013 ◽  
Vol 712-715 ◽  
pp. 1209-1212 ◽  
Author(s):  
Ke Zhang ◽  
Xiang Nan Ma ◽  
Li Xiu Zhang ◽  
Wen Da Yu ◽  
Yu Hou Wu
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Temperature Field ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
High Speed ◽  
Ceramic Materials ◽  
Motorized Spindle ◽  
Element Analysis ◽  
Finite Element Software

The article has analyzed the changes of temperature of different materials of the spindle, and considered 170SD30 Ceramic Motorized Spindle and the same model Metal Motorized Spindle as the research objects, analyzed the inside heat source and heat transfer mechanism of the high-speed motorized spindle; used finite element software to set up the model of the motorized spindle, and did simulation and analysis. Verified by simulation, heat transfer rate of ceramic materials is slower than the metallic materials, in actual operation of the process, due to different materials have different heat transfer rate, so the temperature distribution of the different materials of motorized spindle are different. This conclusion provides the basis to solve motorized spindle temperature field distribution.

Pressure Drop and Heat Transfer Characteristics of Louvered Fin Heat Exchangers

2013 ◽  
Vol 465-466 ◽  
pp. 500-504 ◽  
Author(s):  
Shahrin Hisham Amirnordin ◽  
Hissein Didane Djamal ◽  
Mohd Norani Mansor ◽  
Amir Khalid ◽  
Md Seri Suzairin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Considerable Effect ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Louvered Fin

This paper presents the effect of the changes in fin geometry on pressure drop and heat transfer characteristics of louvered fin heat exchanger numerically. Three dimensional simulation using ANSYS Fluent have been conducted for six different configurations at Reynolds number ranging from 200 to 1000 based on louver pitch. The performance of this system has been evaluated by calculating pressure drop and heat transfer coefficient. The result shows that, the fin pitch and the louver pitch have a very considerable effect on pressure drop as well as heat transfer rate. It is observed that increasing the fin pitch will relatively result in an increase in heat transfer rate but at the same time, the pressure drop will decrease. On the other hand, low pressure drop and low heat transfer rate will be obtained when the louver pitch is increased. Final result shows a good agreement between experimental and numerical results of the louvered fin which is about 12%. This indicates the capability of louvered fin in enhancing the performance of heat exchangers.

Investigation of the effects of geometrical parameters, eccentricity and perforated fins on natural convection heat transfer in a finned horizontal annulus using three dimensional lattice Boltzmann flux solver

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahyar Ashouri ◽  
Mohammad Mehdi Zarei ◽  
Ali Moosavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Lattice Boltzmann ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Maximum Heat ◽  
Content Type ◽  
Dimensional Lattice ◽  
Fin Spacing

Purpose The purpose of this paper is to investigate the effects of geometrical parameters, eccentricity and perforated fins on natural convection heat transfer in a finned horizontal annulus using three-dimensional lattice Boltzmann flux solver. Design/methodology/approach Three-dimensional lattice Boltzmann flux solver is used in the present study for simulating conjugate heat transfer within an annulus. D3Q15 and D3Q7 models are used to solve the fluid flow and temperature field, respectively. The finite volume method is used to discretize mass, momentum and energy equations. The Chapman–Enskog expansion analysis is used to establish the connection between the lattice Boltzmann equation local solution and macroscopic fluxes. To improve the accuracy of the lattice Boltzmann method for curved boundaries, lattice Boltzmann equation local solution at each cell interface is considered to be independent of each other. Findings It is found that the maximum heat transfer rate occurs at low fin spacing especially by increasing the fin height and decreasing the internal-cylindrical distance. The effect of inner cylinder eccentricity is not much considerable (up to 5.2% enhancement) while the impact of fin eccentricity is more remarkable. Negative fin eccentricity further enhances the heat transfer rate compared to a positive fin eccentricity and the maximum heat transfer enhancement of 91.7% is obtained. The influence of using perforated fins is more considerable at low fin spacing although some heat transfer enhancements are observed at higher fin spacing. Originality/value The originality of this paper is to study three-dimensional natural convection in a finned-horizontal annulus using three-dimensional lattice Boltzmann flux solver, as well as to apply symmetry and periodic boundary conditions and to analyze the effect of eccentric annular fins (for the first time for air) and perforated annular fins (for the first time so far) on the heat transfer rate.

scholarly journals Three-dimensional transient mathematical model to predict the heat transfer rate of a heat pipe

2015 ◽  
Vol 7 (2) ◽  
pp. 168781401456781 ◽  
Author(s):  
S Boothaisong ◽  
S Rittidech ◽  
T Chompookham ◽  
M Thongmoon ◽  
Y Ding ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Pipe ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Three Dimensional

scholarly journals Laser interferometry - Report #HT-01-2017

2021 ◽  
Author(s):  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Light Beam ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Laser Interferometry ◽  
Local Heat ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Transfer Rates

An introduction is given to the optical setup and principle of operation of classical and holographic interferometers that are used for convective he at transfer measurements. The equations for the evaluation of the temperature field are derived and methods of analysis are discussed for both two-dimensional and three-dimensional temperature fields. Emphasis is given to techniques for measuring local heat transfer rates. For two-dimensional fields, a method is presented for measuring the surface temperature gradient directly from a finite (wedge) fringe interferogram. This “direct gradient method” is shown to be most useful for the measurement of low convective heat transfer rates. For three-dimensional fields, the equations for calculating the beam-averaged local heat flux are presented. The measurement of the fluid temperature averaged along the light beam is shown to be approximate. However, an analysis is presented showing that for most cases the error associated with temperature variations in the light beam direction is small. Digital image analysis of interferograms to obtain fringe spacings is also discussed briefly.

Wall Roughness Effect on Heat Transfer Rate of the Turbulent Gas-Solid Flow in Inclined Pipes

2014 ◽  
Author(s):  
Adel Ebadi ◽  
Zohreh Mansoori ◽  
Majid Saffar-Avval ◽  
Goodarz Ahmadi
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Nusselt Number ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Wall Region ◽  
Fluid Temperature ◽  
Wall Roughness ◽  
Mean Flow ◽  
Inclined Pipes

The effects of wall surface roughness on the rate of heat transfer and temperature profiles in turbulent gas-solid flows in pipes at different inclination angles were studied. The earlier developed computational model for 3D flows including the four-way interactions was extended and used in this study for evaluating the mean flow, turbulence intensity and thermal fields. Interaction of particles with the rough wall was included by introducing the available stochastic wall roughness models (shadow effect model) for the dispersed phase in the computational program. It was found that changes in the particle dispersion and particle concentration altered the Nusselt number and heat transfer rate in different regions of the pipe. The Nusselt number decreased in the lower part of the duct for horizontal and inclined pipes due to the reduction in the settling velocity. The surface roughness also altered the heat transfer coefficient in the periphery of the vertical riser. The simulation results showed that the fluid temperature was reduced in the pipe core and increased near the wall region for inclined pipes. On the other hand, particle temperature increased and flattened in the entire pipe cross section.

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