Prediction of dryout and post-dryout heat transfer at high pressures using a one-dimensional three-fluid model

Abstract

A set of closure relations, in the context of a one-dimensional three-fluid model, is presented for the prediction of dryout and post-dryout heat transfer at high pressure ( P/ P cr>0.3) conditions. It is shown that the traditional models based on low pressure data for interfacial friction, droplet size and the transition criteria for onset of annular flow cannot be readily extended to high pressure situations. The proposed new relations are validated by comparing with literature data in the pressure range of 30–200 bar, mass flux range of 500–3000 kg m −2 s −1 and tube inner diameters in the range of 10–25 mm. Good agreement is obtained for the dry out quality and the tube wall temperature in the post-dry out region except for cases of low mass flux at high pressures. The predictions show that at high pressure, high mass flux conditions, annular flow may prevail for low gas phase volume fraction, the droplet and the liquid film volume fractions being an order of magnitude higher than those encountered in typical air–water experiments.