Kenichi Hashizume

Flow pattern, void fraction and pressure drop of refrigerant two-phase flow in a horizontal pipe—I. Experimental data

Abstract Experiments with refrigerant two-phase flow in a horizontal pipe have been performed and data on flow pattern, void fraction and pressure drop have been obtained. Refrigerants used were R12 and R22, and the range of saturation pressure was from 5.7 to 19.6 bar. In this paper, the experimental equipment and procedure are described in detail, and the data are both tabulated and presented graphically.

Flow pattern, void fraction and pressure drop of refrigerant two-phase flow in a horizontal pipe—II: Analysis of frictional pressure drop

Two-phase flow in horizontal pipe was analyzed with simplified models for annular and stratified flow. The velocity profiles for the liquid and gas phase were described with the Prandtl mixing length. From this analysis, the frictional pressure drop was calculated with the modified Baker map for flow pattern transition. The intermediate region, i.e. wavy flow, was interpolated between annular and stratified flow. Comparison of this analysis with existing experimental data of refrigerants showed good agreement.

PREDICTION OF CONDENSATION HEAT TRANSFER COEFFICIENT IN HORIZONTAL INTEGRAL-FIN TUBE BUNDLES

A method of predicting the condensation heat transfer coefficient in horizontal integral-fin tube bundles with negligible vapor shear is proposed and compared with experimental results. This method is based on an analytical model talcing the condensate inundation effect into account, where the condensation heat transfer coefficient decreases due to a decrease in effective fin area as condensate flows through the interfin spaces. Heat transfer measurements were carried out in eight-row tube bundles consisting of integral-fin tubes with 35, 26, and 16 fins/in. Refrigerants Rll and R114 were used as test fluids. The proposed method was able to predict the condensation heat transfer coefficient with enough accuracy to enable condensers to be designed without the need for complex calculations.

Heat Transfer and Pressure Drop Characteristics of Finned Tubes in Cross Flow

Finned tubes in various configurations with the same fin geometry (height, thickness, and pitch) were tested in five row tube banks in staggered and aligned arrangements. Measurements on heat and flow characteristics and flow pattern observation have shown that the semicircular finned tube has excellent characteristics as an evaporator tube for waste heat boilers because of its low pressure drop, high heat transfer coefficient, and reduction in dryout risk.

Condensate Subcooling near Tube Exit During Horizontal In-Tube Condensation

An investigation has been carried out on condensate subcooling near the tube exit during horizontal in-tube condensation, both experimentally and analytically. In the experiment, test fluids used were Refrigerants R113, R11, R114, and R12. Condensate subcoolings of larger than 10 K were measured, even before condensation was completed, and data of condensate temperature profiles were obtained along the adiabatic section following the condensing section. Analysis, based on a nonequilibrium heat transfer model, could closely predict experimental data both for condensate subcooling at the condensing section exit and for condensate temperature profiles in the adiabatic section.