Thomas F. Irvine

A GENERALIZED BLASIUS EQUATION FOR POWER LAW FLUIDS

Making use of a generalized turbulent velocity distribution for power law fluids, a Blasius type equation was derived which explicitly relates the friction factor to a generalized Reynolds number in fully developed pipe flow. Comparison of the equation with experimental data shows an agreement of approximately ± 8% A modification of the equation to account for geometry appears to allow its application to non-circular duct flow.

HEAT TRANSFER FROM A HORIZONTAL BUBBLING SURFACE TO AN OVERLYING WATER POOL

Abstract An experimenl was performed to study the effects of bubbling from a circular, horizontal, fiat plate on the heat transfer to an overlying water pool. The plate had drilled orifices through which nitrogen was injected into an overlying pool of water at atmospheric pressure. For “deep” pools, the heat transfer coefficient was found to increase only about 20% over a range of superficial gas velocities from 0.6 to 8.5cm/s, A turbulent heat transfer model developed by Konsetov was found to agree well with the data from this experiment. This model and the experimental data suggest that under certain conditions the heat transfer coefficient is similar for both horizontal and vertical surfaces. These conditions are, that the bubbles only contribute to the stirring action in the pool and only when the bubbling pool is considered “deep”. When the pool height fell below 60% of its diameter, the heat transfer coefficient decreased almost linearly with pool height. This suggests that there occurs a reduction ...

A comparative capillary tube viscometer to measure the viscous properties of newtonian and power-law fluids

Abstract A capillary tube viscometer is described that dispenses with direct pressure measurements by comparing capillary tube flow rates of a fluid whose viscous properties are unknown and a standard Newtonian fluid. Since only flow rate measurements are needed, the experimental technique involves only time and mass measurements and knowledge of the geometry of the capillary tubes. Using this instrument, the viscous properties were measured for distilled water and glycerol as examples of Newtonian fluids and for several polymer solutions as examples of power-law fluids. For distilled water, the measured viscosity agreed with the best value available in the literature within 0.55%.

Film Boiling Heat Transfer to Large Superheats From a Horizontal Flat Surface

A recent investigation reported steady-state measurements of film boiling heat transfer from a flat horizontal circular surface to an overlying pool of water at saturation and atmospheric pressure. Measurements were made from near the Minimum Film Boiling (MFB) point to a superheat of approximately 570 K. These data substantiate that the Berenson model is applicable at temperatures larger than previously observed, as long as a correction is applied to account for the effect of thermal radiation to the overall heat transfer. The objective of this work is to show quantitatively the validity of the Berenson film boiling model at surface superheats well above the MFB to approximately 600 K.

The effect of surface gas injection on film boiling heat transfer

A database was developed for heat transfer from a horizontal plate with film boiling and gas jetting occurring simultaneously, in a pool of water maintained at its saturation temperature. The effect of passing nitrogen through established film boiling is to increase the heat transfer from that surface. At the highest measured superficial gas velocity, approxiamately 8.5 cm/s, and for a constant surface temperature, the heat transfer increases by a factor of two over the heat transfer with no enhancement by gas flux. Further, as the superficial gas velocity approaches zero, the data approach the stable film boiling asymptote

A computational analysis of natural convection in a vertical channel with a modified power law non-Newtonian fluid

An implicit finite difference method was applied to analyze laminar natural convection in a vertical channel with a modified power law fluid. This fluid model was chosen because it describes the viscous properties of a pseudoplastic fluid over the entire shear rate range likely to be found in natural convection flows since it covers the shear rate range from Newtonian through transition to simple power law behavior. In addition, a dimensionless similarity parameter is identified which specifies in which of the three regions a particular system is operating. The results for the average channel velocity and average Nusselt number in the asymptotic Newtonian and power law regions are compared with numerical data in the literature. Also, graphical results are presented for the velocity and temperature fields and entrance lengths. The results of average channel velocity and Nusselt number are given in the three regions including developing and fully developed flows. As an example, a pseudoplastic fluid (carboxymethyl cellulose) was chosen to compare the different results of average channel velocity and Nusselt number between a modified power law fluid and the conventional power law model. The results show, depending upon the operating conditions, that if the correct model is not used, gross errors can result.