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The effect of doping distilled water with MgSO4 on the boiling flow regime and heat transfer on a vertical surface at low pressures was experimentally determined. The experiments were performed in a sealed 20 mm x 20 mm square cross section, 300 mm long vertical pipe. Two opposing walls were made of copper and the other two walls were made of polycarbonate for flow visualization. The tube was filled to 100 mm and heat was applied at the lower end of one copper wall and cooled at the upper end. The boiling dynamics on the heated copper vertical wall and the resulting two phase flow was visualized using a high speed camera for pure distilled water and 0.1 M, 0.2 M and 0.4 M concentrations of MgSO4. The presence of MgSO4 significantly changed the boiling dynamics, with a suppression of bubble coalescence and a promotion of nucleate boiling. The two phase flow exiting the heated section changed from slug to bubbly with the addition of the MgSO4. There was a significant increase in the heat transfer coefficient with the addition of the MgSO4. [ABSTRACT FROM AUTHOR]

A two-phase capillary evaporator has been enhanced using Electrohydrodynamic (EHD) forces. The evaporator was experimentally investigated under dc applied electric field operating modes as well as without an applied electric field. The results without the applied EHD forces show that the induced flow increases with increasing applied heat loads until a dry out condition is reached. The applied dc voltage electric field provides flow enhancements as high as 200%. A slight polarity effect was observed. [ABSTRACT FROM AUTHOR]

The distributions of the mass transfer coefficient in horizontal 90 deg bends were meas-ured under a range of two phase annular flow conditions. A dissolving wall technique at a high Schmidt number (Sc = 1280) is used for the measurements. The maximum mass transfer occurred on the centerline of the bend outer wall at an angle of approxi-mately 50 deg from the bend inlet under all tested conditions. The area of maximum mass transfer rate was found to span approximately 30 deg in the circumferential direc-tion. A second region of enhanced mass transfer occurred on the latter part of the bend with a local maximum occurring slightly off the bend centerline in some cases. Chang-ing the air and water superficial velocities (Jv = 22-30mls, JL = 0.17-0.41 m/s) showed that the air velocity had a larger effect on the mass transfer rates than the water veloc-ity; however, the effect of the water velocity on the mass transfer was not insignificant. [ABSTRACT FROM AUTHOR]

An investigation was performed to examine the effect that the pore size in a porous plate had on the heat transfer between a heated finned surface and a saturated porous plate at different gap distances between the surfaces. Experiments were performed for a porous plate with a nominal pore size of 50 μm and the results were compared with previous results for a pore size of 200 μm (Schertzer et al., 2006, "The Effect of Gap Distance on the Heat Transfer Performance Between a Finned Surface and a Saturated Porous Plate," Int. J. Heat. Mass Transfer, 4, pp. 4200-4208). The plate with the smaller pore size performed better at small and intermediate gaps but not at large gaps. The maximum heat transfer coefficient was similar for both plates when compared in terms of the ratio between the gap distance and the pore size. However, the temperature distributions on the heated foil and their evolution with heat flux were dissimilar when compared in terms of the gap distance or the gap to pore ratio, suggesting that the boiling dynamics within the gap does not scale with either parameters. [ABSTRACT FROM AUTHOR]