Experimental heat transfer

Figure 5.47 shows a plot of the ratio of the experimental heat transfer coefficient obtained by Bao et al. (2000) divided by the predicted values of Chen (1966) and Gungor and Winterton (1986) for heat transfer to saturated flow boiling in tubes versus liquid Reynolds number. It can be seen that both methods provide reasonable predictions for Rcls > 500, but that both overpredict the heat transfer coefficient at lower values of Rols- For comparison it was assumed that the boiling term of these correlations is zero. 

Figure 2.28 Experimental heat transfer results for saturated nucleate boiling of sodium from nickel disks at average pressure of 65 mm Hg. (From Marto and Rohsenow, 1966. Copyright 1966 by American Society of Mechanical Engineers, New York. Reprinted with permission.)... 

Pure mercury does not easily wet steels and certain other structural alloys, thus it is an unwetted case. It causes the direct transition from liquid phase to film boiling heat transfer. The phenomenon has also, on occasion, been observed with alkali metals (Noyes and Lurie, 1966 Avksentyuk and Mamontova, 1973). Figure 2.42 shows experimental heat transfer results for pool boiling of pure mercury on... 

Figure 2.42 Experimental heat transfer results lor pool boiling of pure mercury on the outside of an unwetted horizontal cylindrical heater at 1 atm.

ORNL small-break LOCA tests Experimental investigation of heat transfer and reflood analysis was made under conditions similar to those expected in a small-break LOCA. These tests were performed in a large, high-pressure, electrically heated test loop of the ORNL Thermal Hydraulic Test Facility. The analysis utilized a heat transfer model that accounts for forced convection and thermal radiation to steam. The results consist of a high-pressure, high-temperature database of experimental heat transfer coefficients and local fluid conditions. 

Cimini, R. J., and Chen, J. C., Experimental Measurement of Radiant Transmission Through Packed and Fluidized Media, Experimental Heat Transfer, 1 45— 56 (1987)... 

Graphical presentation of data assists in determining the form of the function of a single variable (or two variables). The response y versus the independent variable x can be plotted and the resulting form of the model evaluated visually. Figure 2.4 shows experimental heat transfer data plotted on log-log coordinates. The plot... 

Smirnov, N.N., V. F. Nikitin, J. Klammer, R. Klemens, P. Wolanski, and J. C. Legros. 1997. Turbulent combustion of air-dispersed mixtures Experimental and theoretical modeling. Experimental Heat Transfer, Fluid Mechanics Thermodynamics 4 2517-24. 

Figure 3.6 Experimental heat transfer coefficients in fluidized bed freezing. From Vazquez and Calvelo (1983a), by permission of the Institute of Food Technologists, USA.

Wambsganss MW, et al. Vaporization in compact heat exchangers. Proceedings of the Experimental Heat Transfer, Fluid Mechanics and Thermodynamics Conference, Brussels, 1997. 

Hence, in experimental heat transfer, the number of variables to be studied is significantly reduced. The Nusselt number or heat transfer coefficient is correlated to only two dimensionless numbers. 

Thus, in order to correlate experimental heat transfer results for a particular geometrical situation, only the four dimensionless variables Nu, Re, Gr, and Pr need to be used. This conclusion can be reached in other ways, it bein demonstrated in the next chapter by using the governing differential equations and considering the conditions under which dynamic similarity will exist. 

Oosthuizen. PH.. Mixed Convective Heat Transfer From Inclined Circular Cylinders , Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics 1989, Proc. First World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Dubrovnik, Yugoslavia, Sept. 1988, pp. 200-207. 

Fig. 25. Comparison of experimental heat transfer coefficients with model, Eq. (7) (Bai et al, 1991).

Today contractors and licensors use sophisticated computerized mathematical models which take into account the many variables involved in the physical, chemical, geometrical and mechanical properties of the system. ICI, for example, was one of the first to develop a very versatile and effective model of the primary reformer. The program REFORM [361], [430], [439] can simulate all major types of reformers (see below) top-fired, side-fired, terraced-wall, concentric round configurations, the exchanger reformers (GHR, for example), and so on. The program is based on reaction kinetics, correlations with experimental heat transfer data, pressure drop functions, advanced furnace calculation methods, and a kinetic model of carbon formation [419],... 

Peng, X.F., Peterson, G.P. and Wang, B.X., Frictional Flow Characteristics of Water Flowing Through Micro-Channels, Experimental Heat Transfer, 1994, 7, 249-264. 

Badran B., Gerner F., Ramada R, Henderson T., Baker K., (1997), Experimental results for low - temperature silicon micromashined micro heat pipe arrays using water and methanol as working fluids, Experimental Heat Transfer, 10,253 - 272... 

Among the first studies on flow boiling heat transfer in a single channel was the one by Lazarek and Black [1] who reported experimental heat transfer eoeffieients for flow boiling of R-113 in a vertical tube with an inner diameter of 3.1 mm (Fig. 2). Their heat transfer coefficients had a strong dependeney on the applied heat flux, but were essentially independent of vapor quality. Similar results were obtained by Tran et al. [13] and Bao et al. 

Figure 2. Experimental heat transfer coefficients from Ref [1] for R-113 in a 3.1 mm tube.

H.U. Kang, S.H. Kim and J.M. Oh, Estimation of thermal Conductivity of nanofluid using experimental effective particle volume, Experimental Heat Transfer, 19, 181-191 (2006). 

Hsu, P.-F., and J. R. Howell. 1992. Measurements of thermal conductivity and optical properties of porous partially stabilized zirconia. Experimental Heat Transfer 5 219. 

Eddy Diffusivity Models. The mean velocity data described in the previous section provide the bases for evaluating the eddy diffusivity for momentum (eddy viscosity) in heat transfer analyses of turbulent boundary layers. These analyses also require values of the turbulent Prandtl number for use with the eddy viscosity to define the eddy diffusivity of heat. The turbulent Prandtl number is usually treated as a constant that is determined from comparisons of predicted results with experimental heat transfer data. 

R. J. Moffat and W. M. Kays, The Turbulent Boundary Layer on a Porous Plate Experimental Heat Transfer With Uniform Blowing and Suction, Stanford Univ. Dept. Mech. Eng. Rep. HMT-1, Stanford University, Stanford, CA, 1967. 

R. A. Pabisz Jr. and A. E. Bergles, Using Pressure Drop to Predict the Critical Heat Flux in Multiple Tube, Subcooled Boiling Systems, Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, vol. 2, pp. 851-858, Edizioni ETS, Pisa, Italy, 1997. 

A. Cavallini, B. Bella, A. Longo, and L. Rossetto, Experimental Heat Transfer Coefficients During Condensation of Halogenated Refrigerants on Enhanced Tubes, J. Enhanced Heat Transfer, 2, pp. 115-125,1995. 

Y. Zvirin, G. F. Hewitt, and D. B. R. Kenning, Boiling on Free Falling Spheres, Drag and Heat Transfer Coefficients, Experimental Heat Transfer (3) 185-214,1990. 

A. Miyra, A. Marroquin, and H. Auracher, Critical Heat Flux and Minimum Heat Flux of Film Boiling of Mixtures in Forced Convection Boiling, in Proc. 4th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Brussels, Belgium, vol. 2, pp. 873-880,1997. 

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