Estimated vapor quality and thermodynamic equilibrium vapor quality assuming isentropic/isenthalpic expansion at different axial locations for the cases without and with maximum inlet vortex at í µí± í µí±í µí± =925 kPa, í µí± í µí±í µí± =36.0 °C, and í µí± í µí±í µí±¢í µí±¡ =680 kPa The estimated fluid densities at the nozzle outlet for the cases without and with maximum vortex are 625 kg/m 3 and 367 kg/m 3 , respectively. Although the total mass flow rate through the nozzle with maximum vortex (12.6 g/s) is much lower than that without vortex (15.7 g/s), the fluid average axial velocity at the outlet with maximum vortex (22.3 m/s) is much higher than that without vortex (16.3 m/s) due to the much lower fluid density at the outlet. For inlet conditions of í µí± í µí±í µí± =925 kPa and í µí± í µí±í µí± =36.0 °C and outlet pressure of 680 kPa, the isentropic nozzle outflow velocity V isentropic,out is 30.2 m/s. The isentropic efficiency of a nozzle is defined as follows:
Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism which requires no change to the physical dimensions of the nozzle geometry. The control is achieved by adjustable nozzle inlet vortex. This novel control mechanism can potentially provide flow control with less sacrifice of nozzle efficiency, which is...
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... the vapor quality at locations in the downstream can be computed. Figure 8 shows the vapor quality in the divergent part at different axial locations relative to the nozzle throat estimated with the above 1D model using the measured pressure and mass flow rate data for the cases without and with maximum inlet vortex at í µí± í µí±í µí± =925 kPa, í µí± í µí±í µí± =36.0 °C (approximately 0.5 °C subcooling), and í µí± í µí±í µí±¢í µí±¡ =680 kPa. The thermodynamic equilibrium vapor quality assuming isentropic/isenthalpic expansion at each location is also displayed. ...
To investigate the influence of the change of tip clearance size on the control effect of the endwall suction, the effects of endwall suction on the aerodynamic performance of the axial compressor cascade were studied numerically. Three tip clearance sizes of 0.5% h, 1.0% h, and 2.0% h (h is the blade height) were mainly considered. The results sho...
The adoption of highly efficient vapour-compression heating, ventilation, air conditioning and refrigeration (HVAC&R) systems is compulsory to achieve a low-carbon society. Expansion work recovery using a two-phase ejector is widely recognized as one of the most promising measures to improve the energy efficiency of HVAC&R units. This holds true for all operation conditions provided that an effective capacity control technique is implemented. In this work a thorough critical review on the current status of the presently available capacity control strategies for two-phase ejectors was carried out. In addition, their pros and cons as well as the comparison of their performance were reported. It was concluded that two-phase ejectors can be properly capacity controlled in large- and medium-scale vapour-compression units. However, a suitable capacity control mechanism for small-scale vapour-compression solutions still requires a major breakthrough and is being intensively discussed among experts in the field.