Two-phase Flow In Horizontal Channel Research Articles

Experimental Investigation on Two-Phase Flow in Horizontal Channel with Vortex Generator

Vortex generator can be used to enhance heat transfer as it is capable of providing better mixing. Vortex generator is easy to manufacture and install in heat transfer units without much additional cost. Present work is planned to investigate the effect of vortex generators on local heat transfer coefficient, critical heat flux (CHF) and pressure drop to ensure design and safety of heat transfer units with vortex generators. Experiments are carried out for three values of pitch 22, 32 and 41 mm and an angle of attack of 45° of vortex generators with horizontal configuration in a smooth tube of diameter 11.9 mm, length 1,000 mm and 0.4 mm wall thickness with R-123 as the working fluid. The effect of mass flux (175–681 kg/m2s) and heat flux (7.9 − 221.7 kW/m2) are studied. Both horizontal and vertical-oriented configurations of the vortex generator are tested. Local wall temperature measurement is carried out with Infrared thermography. Comparing results with plain tube shows the heat transfer coefficient and CHF enhancement. Horizontal orientation (HO) of the vortex generator gives better results than the vertical orientation (VO). Heat transfer coefficient, CHF and pressure drop penalty increase with a decrease in the pitch of the vortex generator.

Effect of heaving motion on two-phase flow in horizontal channel: Flow and heat transfer characteristics

Experiments were carried out to investigate the effects of vibration frequency (0Hz~8Hz) and amplitude (0 mm~8 mm) on gas-liquid two-phase flow characteristics in a channel under heaving motion. The magnitude of instantaneous frictional pressure drop under heaving motion increases with the increasing vibration parameters. A 3-D numerical simulation on heat transfer characteristics at various working conditions with a constant applied wall heat flux was performed using the CLSVOF (Coupled Level Set and Volume of Fluid) model combined with dynamic mesh and UDF (User Defined Function) in Fluent. The results show that the heaving motion has a favorable effect on heat transfer coefficient. The fluid temperature reaches its maximum value is about 0.1s–0.2s later than the wall temperature. According to the field synergy analysis, there exists a most appropriate combination of vibration parameters. It was also found that, similar to the temperature variation, the maximum field synergy number occurs approximately when the channel moves from the highest point of heaving motion to the equilibrium position.

E222 沸騰水平二相流におけるボイド率変動挙動 : 離散気泡モデルによる数値シミュレーション(熱伝達III)

Two-phase flow is a complex system due to the existence of the gas-liquid interfaces. The structure of these interface are spatio-temporally deformable, because break-up, coalescence and expansion of bubbles are always encountered while flowing downstream. Boiling two-phase flow is all the more complex phenomena due to the combined effect of the void propagation and the phase change. This paper describes numerical investigation on the boiling two-phase flow in horizontal channel conducted by using the discrete bubble model. The void propagation as well as the combined effect with the phase change was well simulated so that the potential of the present model was demonstrated.