Heat Transfer 1970/5. [antikvár]

POOL BOILING HEAT TRANSFER FROM A VIBRATING SURFACEW. F. Calus and Peter Rice Loughborough University of Technology, EnglandAbstractThe effect of vibration on the heat transfer rate in" the pool boiling of water was investigated using a horizontal 0.0315 cm diameter nickel-aluminium wire vibrated in a vertical plane. The frequency of vibration was varied from 0-124 Hz, the amplitude from 0-0. 2032 cm, and the heat flux from 0-7. 25x 105 W/m2t. The experim-ental data from both the stationary and the vibrating surfaces are correlated by a modification of the Rohsenow pool boiling equation. It has been found that the Rohsenow constant dependent on the type of solid/liquid combination assumes one value for the high flux boiling and another different value for lower flux boiling processes.IntroductionThe effect of vibration on heat transfer rates to fluids is of practical interest. The cases of natural and forced convection have been covered by a relatively large number of investigations, but the case of nucleate boiling still remains to be explored. The investigations, at present to hand, are listed in Table 1. It appears that the main variables affecting heat flux are frequency and amplitude of vibration, the amplitude to diameter ratio and the temperature difference. In most of the investigations in Table 1 frequency and amplitude of vibration were of the same order of magnitude but the amplitude to diameter ratio differed widely from investigator to investigator. The conclusions of various authors with respect to the effect of vibration on heat flux seem to be inconsistent. Kovalenko /l/reports a decrease in the heat flux, Price and Parker /2/ no effect, McQuiston and Parker /3/ a small improvement in heat flux at higher values of the flux, Bergles /4/ some improvement at lower values and none at higher values of heat flux. Nangia and Chon /5/ used much higher values of a/d than all the other investigators and report an increase in the heat flux of up to 200% in the lower 11 region and a negligible increase at the higher 41 values.The object of this work is (a) to confirm the data of reference /5/, (b) to extend the range of the operating variables, particularly of the values of the a/d ratio at the lower end, and (c) to attempt, with the aid of reasonably firm experimental evidence gained, to correlate these data.Method and ApparatusThe test surface was a 0. 0315 cm dia nickel aluminium wire 15. 3 cm long of which the 8. 9 cm midlength was used for heat transfer measurements. The wire was mounted horizontally under slight tension in a stainless steel yoke and vibrated in a vertical plane. 0. 0063 cm dia tappings were soldered to the test wire and to a junction attached to the vertical legs of the yoke 1. 5 cm above the test wire.B 1.1