Heat transfer experiments

Salt, K. J., and Wintle, C. A., Design and operation of a transistorized bridge-type detector for burnout in boiling heat transfer experiments, AEEW-R.330, H.M. Stationery Office, London (1964). 

Using the properties of water Li and Cheng (2004) computed from the classical kinetics of nucleation the homogeneous nucleation temperature and the critical nu-cleation radius ra. The values are 7s,b = 303.7 °C and r nt = 3.5 nm. However, the nucleation temperatures of water in heat transfer experiments in micro-channels carried out by Qu and Mudawar (2002), and Hetsroni et al. (2002b, 2003, 2005) were considerably less that the homogeneous nucleation temperature of 7s,b = 303.7 °C. The nucleation temperature of a liquid may be considerably decreased because of the following effects dissolved gas in liquid, existence of corners in a micro-channel, surface roughness. 

Potentiostatic measurements are analogous to heat-transfer experiments in which the wall temperature is controlled, whereas galvanostatic measurements are similar in character to those in which the heat flux is controlled. However, whereas heat transfer may be measured readily with a uniform flux generated at the surface, there is no assurance that a known current applied to an extended electrode will yield a uniform current distribution over the surface, unless the surface is divided into electrically insulated segments and identical current densities are imposed externally on these... 

The use of the term evaporation coefficient comes about from mass and heat transfer experiments without combustion—that is, evaporation, as generally... 

The effective radial diffusivity D is normally different from the axial dilfusivity. It is often safe to neglect the radial variation of species concentration due to the relatively fast radial mixing. The effective conductivity k has to be determined from heat-transfer experiments preferably with the actual bed and fluids. This coefficient can be... 

To investigate the behaviour of the present reactor, a series of steady state and dynamic experiments were performed, consisting of reactor start-up, step changes in feed composition and ramp changes in feed and jacket temperature. Heat transfer experiments without reaction were also performed. Some of the results are compared with model simulations, using, whenever possible, a priori values of model parameters. 

Subbarao and Basu (1986), Basu and Nag (1987) and Basu (1990) derived the expression of cluster residence time lc on the heat transfer surface based on Subbarao s (1986) cluster model, although the model is not widely accepted. Lu et ai (1990) and Zhang et al. (1987) have also obtained empirical correlations independently for predicting cluster residence time based on their heat transfer experiments. However, because of the lack of available and reliable information about the residence time of clusters at the surface and the fraction of the clusters in solids suspension, a significant discrepancy between the results predicted by the different approaches mentioned earlier has been observed. Besides, it should be pointed out that the major shortcoming in the earlier models is that they all take no account of the heat transfer surface length. 

The use of the term evaporation coefficient comes about from mass and heat transfer experiments without combustion—i.e., evaporation, as generally used in spray-drying and humidification. Basically, the evaporation coefficient p is defined by the following expression, which has been verified experimentally ... 

Garimella and Bandhauer [32] conducted heat transfer experiments using the same test sections that were used for the pressure drop experiments of Garimella et al. [24, 25, 27, 28] described above. The high heat transfer coefficients and low mass flow rates in microchannels necessitate modifications to the test facility and test procedures described above. For the small zlx required in the test section, the heat duties at the mass fluxes of interest are relatively small. Calculating this heat duty from the test section inlet and outlet quality measurements would result in considerable... 

For the hydrocarbon--CO2 systems studied here, at pressures above the critical pressure (7.383 MPa) and above the critical temperature (304.21 K) of C02 the isobaric x,T coexistence plots of liquid and vapor phases form simple closed loops. The minimum occurs at the lower consolute point or the Lower Critical Solution Temperature (LCST). Since pressure is usually uniform in the vicinity of a heat transfer surface, such diagrams serve to display the equilibrium states possible in a heat transfer experiment. 

In our heat transfer experiments, bulk fluid conditions were chosen to be just below the phase coexistence curve on either side of the lower consolute point. Thus, on heating at constant pressure, either evaporation of a liquid or condensation (retrograde) of a vapor took place once a small excess of test section surface temperature over bulk fluid temperature occurred. To be specific, the retrograde condensation region of the vapor--liquid phase coexistence curve of Figure 1 is the region of positive slope to the right of the LCST. 

Thus Dunlap and Rushton [105] found in heat transfer experiments in bunched vertical pipes, that the differences between cooling and heating had to be taken consideration with Vis ... 

Similar results have also been recently reported in flow boiling heat transfer experiments on multi-micro-channel systems, as in the case of Agostini et al. [20, 21] who tested refrigerants R-134a and R-236fa in a 67 parallel micro-channel evaporator (rectangular channels, 0.223 mm wide,... 

From their heat transfer experiments on R-113, Lazarek and Black [1] proposed the following non-dimensional correlation for the flow boiling Nusselt number Nui = oD/kl) ... 

D. E. Jung, M. McLinden, R. Rademacher, and D. Didion, Horizontal Flow Boiling Heat Transfer Experiments With a Mixture of R22/R114, Int. J. Heat Mass Transfer (32) 131,1989. 

Z. Wang, P. T. Ireland, and T. V. Jones, An Advanced Method of Processing Liquid Crystal Video Signals from Transient Heat Transfer Experiments, ASME J. of Turbomachinery, 117, pp. 184-188, 1995. 

Promotion of Dropwise Condensation. Preliminary heat transfer experiments, using distilled water as feed, gave values of over-all heat transfer coefficient around 1000 B.t.u./sq. ft hr. ° F. and analysis indicated that the jacket condensate film provided the main resistance to heat transfer, due to filmwise condensation of the jacket steam. Following reports by Garrett (4) of successful tests using drop-wise condensation promoters, it was decided to use oleic acid for this purpose in the present experiments. The resulting improvement in jacketside coefficients enabled over-all heat transfer coefficients in excess of 5000 B.t.u./sq. ft hr ° F. to be achieved. 

The model discussed here uses the effective transport concept, this time to formulate the fiux of heat or mass in the radial direction. This flux is superposed on the transport by overall convection, which is of the plug flow type. Since the effective diffusivity is mainly determined by the flow characteristics, packed beds are not isotropic for effective diffusion, so that the radial component is different from the axial mentioned in Sec. 11.6.b. Experimental results concerning D are shown in Fig. 11.7.a-l [61, 62,63]. For practical purposes Pe may be considered to lie between 8 and 10. When the effective conductivity, X , is determined from heat transfer experiments in packed beds, it is observed that X decreases strongly in the vicinity of the wall. It is as if a supplementary resistance is experienced near the wall, which is probably due to variations in the packing density and flow velocity. Two alternatives are possible either use a mean X or consider X to be constant in the central core and introduce a new coefficient accounting for the heat transfer near the wall, a , defined by ... 

The heat transfer experiments conducted at Oak Ridge differed from the HTTR system in that the water used at, Oak Ridge was cycled in an open system whereby oxygen and nitrogen of the air were readily dissolved. It is expected that any gaSes in the MTR process water will be practically completely removed by the flash evaporation process, and therefore the corrosion rates may be even less than those determined by the experiments conducted at ORNL,... 

Liquid Crystal Technique for Measuring Temperature, Fig. 3 Example of a heat transfer experiment between hot wall and cold fluid. Left observing the wall temperature distribution with a thin layer of TLCs. Right observing the temperature distribution in the fluid with TLC tracers... 

Yao, S.C., Choi, K.J. 1987, Heat Transfer Experiments of Mono-dispersed Vertically Impacting Sprays. International Journal of Mult hase Flow 13,639-648. 

Standard temperature measurement in heat transfer experiments is still done using thermocouples. Thermocouple wires have diameters down to 12.7 (im. For shielded thermocouples, the smallest diameters available are in the region of 100 pm. The drawbacks are conduction losses through the thermocouple wire and flow disturbance. These errors are obviously more pronounced in microfluidic flows. 

The wall temperature for film boiling definitely decreased from the inlet to the exit of the tube. This is opposite to the trend of wall temperatures as seen with single-phase heat-transfer experiments. 

The effects on fuel element temperatures of gross pressure and flow changes wlU be Investigated In a series of transient heat transfer experiments ... 

The above discussion implies that the correlation equations derived for NubeSherwood number for estimating g.panicies-... 

A streamlined shape with airfoil cross section is to be used to absorb ammonia from a flowing air stream (velocity of 4.5 m/sec) on its wetted surface. No mass transfer data exist for this given shape. However, heat transfer experiments with the same shape and air velocity show the heat transfer coefficient to be 52.2 W/m °K. 

Rohde, M., Peelers, J.W.R., PucciareUi, A., Kiss, A., Rao, Y.F., Onder, E.N., Miihlbauer, P., Batta, A., Hartig, M., Chatoorgoon, V., Thiele, R., Chang, D., Tavoularis, S., Novog, D., McClure, D., Gradecka, M., Takase, K., 2015. A blind, numerical benchmark study on supercritical water heat transfer experiments in a 7-rod bundle. In The 7th International Symposium on Supercritical Water-Cooled Reactors lSSCWR-7, March 15—18 paper 2044, Helsinki, Einland. 

Chen, Y., Yang, C., Zhao, M., Bi, K., Du, K., 2014. Forced convective heat transfer experiment of supercritical water in different diameter of tubes. Journal of Energy and Power Engineering 8, 1495—1504. 

All heat transfer experiments have been carried out with the boundary condition of constemt heat flux q at the interface of the particles. In this case the average Nusselt number of the non uniform system is given by ... 

Figure 22a, Wall heat transfer coefficient w obtained by Wunschmann and Schlunder (64) from transient heat transfer experiments at room temperature and various gas (air) pressures. Glass, d = 3,1 mm.

Heat transfer experiments and material research studies have been carried out at Kyushu University, IAEA, the University of Tokyo and elsewhere. Comparison of heat transfer coefficients predicted by different correlations is shown in Fig. 1.60. Accuracy above 500°C is important for the calculation of MCST. Calculated MCSTs with different correlations are compared in Table 1.16 [122]. The largest difference is 44°C. Current heat transfer correlations were developed based on experiments using smooth circular tubes. Experiments on fuel bundle geometry are necessary. The effect of grid spacers on the heat transfer correlation should be included in the prediction of MCST. The correlation of downward flow is necessary for the design. Downward flow is adopted in the low temperature region below the pseudo-critical temperature. 

K. Ezato, M. Akiba, et al., Research and Development of a Super Fast Reactor (8) Heat Transfer Experiments Around a Simulated Fuel Rod with Superoitical Pressure Water, Proc. 16th PBNC, Aomori, Japan, October 13-18, 2008, P16P1240 (2008)... 

To potentially replace the need for large scale experiments to develop fuel btmdles in future R D work, the three-dimensional CFD code ACE-3D, developed by IAEA based on the two-fluid model for BWR conditions, was modified to handle supercritical pressure fluid in the fuel bundle geometries. The heat transfer experiments by Kyushu University with HCFC22 and by JAEA with water were analyzed for its validation [31-36]. Also the three-dimensional model of this code for the fuel btmdles was combined with the one-dimensional model for future applications to plant system analyses. 

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