Heat transfer measuring

Ghajar AJ, Kim J-Y, Malhotra K, Trimble S (2004) Systematic heat transfer measurements for air-water two-phase flow in horizontal and slightly upward inclined pipe. In Proceedings of the 10th BrazUian Congress of Thermal Sciences and Engineering - ABCM, Rio de Janeiro, 29 Nov-3 Dec 2004... 

ShaJSc113 as indicated by the thin solid line. This 0.67 power of Re agrees with the result of a turbulent heat transfer measurement on a rotating sphere [40], Since the flow induced by a rotating sphere is also characterized by an outflowing radial jet at the equator caused by the collosion of two opposing flow boundary layers on the sphere, the 0.67 power dependence on Re is clearly related to the radial flow stream away from the equator. 

Ackeskog et al. (1993) made the first heat transfer measurements in a scale model of a pressurized bubbling bed combustor. These results shed light on the influence of particle size, density and pressure levels on the fundamental mechanism of heat transfer, e.g., the increased importance of the gas convective component with increased pressure. 

Fig. 17. Least squares fits of the radial temperature profile in KATAPAK-M. Reprinted from Chemical Engineering Science, Vol. 54, von Scala et al., Heat Transfer Measurements and Simulation of KATAPAK-M Catalyst Supports, pp. 1375-1381, Copyright (1999), with permission from Elsevier.

Use of Fine Unheated Wires for Heat Transfer Measurements in the Shock Tube , GAL CIT Hypersonic Research Memorandum No. 55, (June I960) 16) Dunkle s Syllabus (1960-... 

Gau.C., Yih, K.A., and Aung, W.. Reversed Flow Structure and Heat Transfer Measurements for Buoyancy-Assisted Convection in a Heated Vertical Duct . J. Heat Transfer. Vol. 114. pp. 928-935. 1992. 

Citakoglu. E. and Rose, J.W., Dropwise Condensation Some Factors Influencing the Validity of Heat Transfer Measurements." Int. J. Heat Mass Transfer, Vol. 11, p. 523,... 

The carbon dioxide leading tube was configured in such a way, that the thickness of the condensate film at the outside of this tube does not influence the heat transfer measurements, regardless of the angle of inclination. For that purpose the tube has been finned on the outside. The geometry of those fins as well as the distances between them have been chosen in such a way, that the temperature differences on the outer wall along the tube never exceed 0.5°C, regardless of the inclination of the tube. 

Tan, R., Monlat, Mareux, H., and Couturier, S. About the Effect of Experimental Set-up Characteristics on the Validity of Heat Transfer Measurements in Circulating Fluidized Bed Mock-ups, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 384-389. Somerset, Pennsylvania (1993). 

In order to try to clarify the different types of mechanism involving either redox cycles and/or acid-base properties, a study of the surface chemistry of single, doped and mixed oxides is of much interest. The calorimetric technique, by allowing heat transfer measurements, can provide very informative data on the thermodynamics of solid-gas interactions and for the study of the surface and reactivity of these metal oxides. 

A. J. Ghajar and L. M. Tam. Heat Transfer Measurements and Correlations in the Transi lion Region for a Circular Tube with Three Different Inlet Configurations. Experimenial Thermal and Fluid Science, Vol. 8 (1994),... 

Because pressure drop measurements are much faster and cheaper than mass transfer or heat transfer measurements, it is tempting to try to relate the Sherwood and Nusselt numbers to the friction factor. A relation that has proved successful for smooth circular tubes is obtained from a plausible assumption that is known as the film layer model. The assumption is that for turbulent flow the lateral velocity, temperature, and concentration gradients are located in thin films at the wall of the channel the thickness of the films is indicated with 8/, 87, and 8., respectively. According to the film model, the lateral velocity gradient at the channel surface equals (m)/8/, the lateral temperature gradient equals (T/, - rj/87 and the lateral concentration gradient equals (c. /, - C , )/8,.. From these assumptions, and the theoretical knowledge that 8//8r Pr and 8//8e Sc (for... 

Agostini, B. Watel, B., Bontemps, A. and Thonon. B., Ejfect of geometrical and thermophysical parameters on heat transfer measurements in small diameter channels. GRETh Grenoble. Internal report 2003. (Unpublished). 

Development of additional models for pressure drop in noncircular channels, and for heat transfer coefficients and transition criteria based on nondimensional parameters is underway. This integrated approach using flow visualization, pressure drop and heat transfer measurements, and analytical modeling, is yielding a comprehensive understanding of condensation in microchannels. 

Two methods have proved themselves in the reproduction of heat transfer measurements. One starts from empirical correlations for the pure substances. These correlations normally contain dimensionless numbers, that now have to be formed with the properties of the binary mixture. The reduction in heat transfer because of inhibited bubble growth caused by diffusion is taken into account by the introduction of an extra term. This type of equation has been presented by... 

Boiling heat transfer test loop (Heat transfer measurements and... 

Heat transfer measurements in a stirred tank with a self-sucking hollow stirrer can be represented in the same pi-space, because here due to the Q(Fr) relationship (see Fig. 4.32), the gas throughput for a given stirrer geometry is not an independent variable, but is coupled with the stirrer speed. 

Figure 7.8 shows heat transfer measurements in the water/air system in a tank with a hollow stirrer [610/2] in comparison with heat transfer measurements in bubble columns. It emerged, that with additional stirring approximately double as much heat can be removed as in the bubble column alone. In addition h applies... 

M. Chirtoc. and J.F. Hemy, 3co hot wire method for micro-heat transfer measurements From anemometry to scaiming thermal microscopy (SThM), Europ. Phys. J., Special Topics, 153, 343-348 (2008). 

FIGURE 4.8 Comparison of local heat transfer measurements of Qureshi and Gebhart [222] with Eq. 4.34 for a uniform heat flux, vertical flat plate in water. 

Recent heat transfer measurements by Sparrow and Bahrami [256, 257] lie about a factor of 10 higher than those of Elenbaas near the lower end of the Ra range. Tsubouchi and Masuda [269] recommended that the heat transfer from square fins be calculated from their equations for circular fins using an equivalent diameter D = 1.23H. Their procedure for circular fins is outlined in the following section. 

Gebhart et al. [109, 111] have provided accurate heat transfer measurements spanning the mixed convection zone for extremely fine wires for Pr = 0.7, 6.3, and 63, and have also provided equations for the bounds of the mixed convection zone. 

A. M. Gaion and R. J. Goldstein, Velocity and Heat Transfer Measurements in Thermal Convection, Phys. Fluids (16/11) 1818-1925,1973. 

Local heat transfer measurements were carried out in the once-through system for the same aqueous polyacrylamide solutions used in the friction factor and viscosity measurements shown in Figs. 10.22 and 10.23 [37, 93]. These heat transfer studies involving a constant heat flux boundary condition required the measurement of the fluid inlet and outlet temperatures and the local wall temperature along the tube. These wall temperatures are presented in terms of a dimensionless wall temperature 0 in Fig. 10.27 for four selected concentrations. Here 0 is defined as... 

R. W. Allen and E. R. G. Eckert, Friction and Heat Transfer Measurements to TUrbulent Pipe Flow of Water (Pr = 7 and 8) at Uniform Wall Heat Flux, Trans. ASME (86) 301,1964. 

In general, the term liquid crystal is used to describe an intermediate phase between liquid and solid occurring in some organic compounds. The phase of liquid crystal can be divided into two mesophases smectic and nematic. Nematic liquid crystals can be further divided as chiral nematic or archiral nematic. In chiral nematic liquid crystals, sterol-related compounds are called cholesteric, and non-sterol-based compounds are termed chiral nematic. For heat transfer applications, encapsulated forms of chiral nematic [71] or the composite liquid crystal sheets of the cholesteric type [72] are commonly used. Recently, the application of micro-encapsulated liquid crystals has become more popular in heat transfer measurements because of the fast response and easy paintbrush or spray application to the test surface. 

Since the temperature on the test surface is determined from the reflection color on the liquid crystal surface, the color sensation for the reflected light from a liquid crystal surface becomes the essential element that affects the uncertainty in temperature or heat transfer measurements. Several parameters affect the color sensation the spectral characteristics of the incident light that illuminates the liquid crystal surface, the helical structure of the liquid crystal, the incidence and reflection angle of light, and the color capturing device [73]. 

Analogies have been widely used to study heat transfer. An analog system is often simpler to construct than a heat transfer test apparatus. In addition, analog systems can often be set up to avoid secondary effects (e.g., conduction) that tend to introduce errors in temperature and heat transfer measurements. 

Computer modeling of convection has had mixed success. Many convection problems, particularly those involving laminar flow, can readily be solved by special computer programs. However, in situations where turbulence and complex geometries are involved, computer analysis and modeling are still under development. Mass transfer analogies can play a key role in the study of convective heat transfer processes. Two mass transfer systems, the sublimation technique and the electrochemical technique, are of particular interest because of their convenience and advantages relative to direct heat transfer measurements. 

A comprehensive review of the naphthalene sublimation technique is given in Ref. 126. The naphthalene sublimation technique, commonly employed to measure convective transport phenomena, has several advantages over direct heat transfer measurement techniques. Tliese advantages are more detailed mass transfer distribution over the test piece (typically thousands of data measured points), avoidance of heat conduction and radiation loss, and better control on boundary conditions. 

K.-H. Platzer, C. Hirsch, D. E. Metzger, and S. Wittig, Computer-Based Areal Surface Temperature and Local Heat Transfer Measurements with Thermochromic Liquid Crystals (TLC), Experiments in Fluids, 13, pp. 26-32,1992. 

S. A. Hippensteele, L. M. Russell, and F. S. Stepke, Evaluation of a Method for Heat Transfer Measurements and Thermal Visualization Using a Composite of a Heater Element and Liquid Crystals, ASMEJ. of Heat Transfer, 105, pp. 184-189,1983. 

D. E. Metzger and D. E. Larson, Use of Melting Point Surface Coating for Local Convection Heat Transfer Measurements in Rectangular Channel Flows with 90° Hirns, ASME J. of Heat Transfer, 108, pp. 48-54,1986. 

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