| Gas-liquid separator is of importance and widely-used in the thermodynamic cycle since it is always requisite.Among the different types of gas-liquid separators,T junction is much simpler,compacter,more integrated and cheaper compared with other separators.What's more,the effectiveness of the T junction has already been proved.Therefore,it is a promising separating device.In the paper,gas-liquid two-phase separation in the T junction is regarded as the study object,which is aimed at understanding and establishing the phase-separation theory and numerical model in the T junction,making the T junction phase-separation efficiency clear,and studying the influence of the T junction parameters on the phase-separation efficiency.Thus,the investigation and analysis of the T junction phase-separation for the organic working fluid are unfolded based on the numerical study and experimental exploration.Because of the significant influence of the inlet flow pattern on the T junction phase-separation,this paper firstly conducts a numerical simulation of a specific flow pattern----annular two-phase flow which always takes place in the straight pipe before T junction.The entrainment and deposition process of the droplets in annular flow is considered in the CFD model of the annular flow.Secondly,the numerical model of the annular two-phase flow separation for the organic working fluid in the run-type T junction is established in this paper.The numerical simulation is conducted,in which the Eulerian model is applied to describe the gas-liquid two-phase flow and the interfacial drag is taken into account.Thereafter,the experimental investigation of the phase-separation performance in the vertical impact T junction which is used as a gas-liquid separator is conducted.The working fluids that are studied in the experiment are R134 a and R245 fa.The high-speed camera is employed to shoot the flow pattern in the upper outlet of the vertical impact T junction in order to obtain the transition line of the flow pattern from mist flow to churn flow.In the meanwhile,the influence of the inlet quality and inlet mass flow rate of the T junction on the outlet parameters,vapor separation efficiency and liquid separation efficiency are studied and analyzed.At last,the attempt of building the phase-separation theory and mathematical model of the vertical impact T junction for the organic working fluid is put forward in this paper.The main conclusions of the whole paper are presented below:(1)The numerical model of the annular flow in the pipe could well predict the flow pattern of the annular flow and the variation trends of the parameters along with inlet parameters.(2)The simulation of the phase-separation of the annular flow in the run-type T junction is capable of prediction for the side-arm take-offs in the range of theLF between 0.2 and 0.6.(3)For the phase-separation of the run-type T junction,the difference of the working fluid and the change of the saturated temperatures have a little effect on the side-arm take-offs.However,the inlet mass flow rate of the T junction has a significant effect on it.(4)It is found in the experiment that the upper outlet of the vertical impact T junction is in mist flow when the inlet quality and inlet mass flow rate are relatively small.Instead,the upper outlet of the T junction changes into churn flow from mist flow when the inlet quality and inlet mass flow rate increase to some degree.Basically,the liquid separation efficiency of the T junction decreases with the rise of the inlet quality.And the liquid separation efficiency becomes lower with the increase of the inlet mass flow rate.The flow pattern of the upper outlet is critical to the liquid separation efficiency.It is proved that the liquid separation efficiency is almost up to 90% when the upper outlet is in mist flow. |
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