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Theoretical and Experimental Investigation of the Wetted Air Dehumidification by Supersonic Separator

Majidi, Davood | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53204 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Farhadi, Fathollah
  7. Abstract:
  8. Supersonic separators (3Ss) are used in gas separation processes such as dehumidification of humid air thanks to their high performance and good pressure recovery. Moreover, 3Ss because of their simple mechanical construction and absence of any environmental impact are preferred to other dehydration methods of natural gas, such as adsorption, cooling, and membrane. Also using the 3Ss for relatively large facilities with considerable investment is more than evident. In the first phase of present study, 2-D simulation is performed to investigate the effect of operational and thermo-physical parameters on shockwave position in a specially conceived wet air 3S. Moreover, the effect of cyclonic part and wet outlet geometry are studied by proposing four cases. Increasing the length of the cyclonic part from 5 to 15 cm has positive and negative effects on the performance of 3S and the pressure recovery coefficient, respectively. The optimum length is between 10 and 15 cm. To show negative effects of wasted air from the wet outlet, its flow has been increased from 3.6 to 8.1% of inlet flow. Better performance of 3S is obtained by reducing the flow disturbances around the wet outlet and moving the shockwave towards the outlet. In the second phase of present study, the effects of the swirl generator (SG) on shockwave’s position and pressure drop, have been examined by 3-D simulation and validated by the Arina’s study. An increment of the blades number, height and end angle, lead to shockwave’s displacement toward the nozzle outlet. The maximum increment of the shockwave’s displacement which is due to increasing blade’s end angle from 15° to 30°, is about 47%. For this case, the pressure drop share of the SG is about 45% of total pressure drop. Moreover, residence time of particles is increased about 51%. As a general finding, increasing the swirl intensity, provides longer residence time to separate adequately the liquid from the gas; however, an increment of energy loss is not desirable for the high-pressure process at downstream of the 3S. In the third phase of present study, experimental investigation on the hydrodynamic behavior of air as working fluid and dehumidification performance of 3S have been accomplished. The effect of the operational parameters on shockwave’s position are examined. The outcomes show that by increasing the pressure level of 3S, the deviation between numerical and experimental results decreases. Relative error for low pressure level is about 20%; while it is less than 10% at higher pressure. The effect of the operational parameters and humidity of inlet air on the dehumidification performance of 3S have been investigated by proposing a new simplified method for predicting condensation phenomenon. Results show that by increasing inlet pressure and decreasing inlet temperature, dehumidification performance of 3S is improved. The improvement of performance for 3S with proposed geometry is about 5% for 2 bar increase of inlet pressure and 15% for 10 K decrease of inlet temperature. Moreover, with 0.05 % increase in the molar percent of water vapor in the inlet air, the performance of 3S is enhanced about 10%. In addition, decreasing the outlet pressure under specified operating conditions has no effect on performance of 3S and only it could compensate the undesirable displacement of shockwave due to decreasing the inlet pressure
  9. Keywords:
  10. Supersonic Separation ; Dehumidification ; Shock Waves Position ; Wet Outlet Geometry ; Swirl Generator Geometry ; Simplified Condensation Method

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