Studies on horizontal in-tube condensation flow and heat transfer in different gravity conditions are reviewed, with focus concentrated on the case of small scale tube, for low flow rate of ammonia, which is a routine practice in space applications. Gravity influence on in-tube condensation in partial gravity conditions are discussed in detail. Condensate film on the inner perimeter in horizontal in-tube condensation leads to the differences of its flow configuration from forced boiling and adiabatic two-phase gas-liquid flow, which enhances the effects of surface tension and increases the value of the critical Bond number with regards to the transition to wavy and stratified flow regimes. Thus, the influence of gravity on flow and heat transfer in horizontal in-tube condensation with small scale tube and low flow rate will be weakened, even be come negligible. It was found that the measured frictional pressure drops in these cases are close to the predictions given by smooth annular flow model, which are smaller than the predictions by empirical correlations based on the experimental data of two-phase gas-liquid flow at conventional conditions. Better predictions are obtained only by using a method based on a coupling of the void fraction with the interfacial shear rate. 更多还原
; 彭浩
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