Sun Zhongning

IODINE REMOVAL EFFICIENCY IN NON-SUBMERGED AND SUBMERGED SELF-PRIMING VENTURI SCRUBBER

The objective of this conducted research is to study the iodine removal efficiency in a self-priming venturi scrubber for submerged and non-submerged operating conditions experimentally and theoretically. The alkaline solution is used as an absorbent, which is prepared by dissolving sodium hydroxide (NaOH) and sodium thiosulphate (Na2S2O3) in water to remove the gaseous iodine (I2) from the gas. Iodine removal efficiency is examined at various gas flow rates and inlet concentrations of iodine for submerged and non-submerged operating conditions. In the non-submerged venturi scrubber, only the droplets take part in iodine removal efficiency. However, in a submerged venturi scrubber condition, the iodine gas is absorbed from gas to droplets inside the venturi scrubber and from bubbles to surrounding liquid at the outlet of a venturi scrubber. Experimentally, it is observed that the iodine removal efficiency is greater in the submerged venturi scrubber as compare to a nonsubmerged venturi scrubber condition. The highest iodine removal efficiency of 0.99±0.001 has been achieved in a submerged self-priming venturi scrubber condition. A mathematical correlation is used to predict the theoretical iodine removal efficiency in submerged and non-submerged conditions, and it is compared against the experimental results. The Wilkinson et al. correlation is used to predict the bubble diameter theoretically whereas the Nukiyama and Tanasawa correlation is used for droplet diameter. The mass transfer coefficient for the gas phase is calculated from the Steinberger and Treybal correlation. The calculated results for a submerged venturi scrubber agree well with experimental results but underpredicts in the case of the nonsubmerged venturi scrubber.

Flow resistance characteristics of water in narrow annulus during heat exchange

Considering the special resistance characteristics of fluids flowing through ducts with small gaps, experiments are performed to investigate the resistance characteristics of single-phase water, which is forced to flow through vertical annuli. The gap sizes are 0.9, 1.4 and 2.4mm, respectively. The experiments are conducted under condition of 1 atm. The water in the annuli is heated by high temperature water reversely flowing through the inner tube and the outer annulus. The results show that the flow pattern begin to change from laminar to turbulent before Reynolds number approaches 2000, the flow resistance in annulus has little relations with the temperature difference and ways of being heated, but mainly depends on the ratio of mass flux to the width of annulus.

Numerical simulation and experiment investigating the performance of a capacitance sensor measuring the humidity of wet steam

The humidity of steam is an important parameter, but its exact measurement is difficult. The use of capacitance is a novel measurement method. On the basis of the theory of dielectric polarization and hydrodynamics and applying FLUENT UDF language, the coupling of the steam flow field and electric field within the capacitance sensor are investigated through numerical simulation. The standard k–e model, scalable wall function and SIMPLE (Semi-Implicit Method for Pressure Linked Equations) are used in the research. Additionally, steam humidity is measured according to capacitance in an experiment. The results show that the water molecule is polarized; polarized charge appears near the wall of the flow field; the radial velocity depends on whether there is an electric field within the capacitance sensor, with the dependence being greatest near the outermost board; and the electric field intensity near the electrode board is less when there is no flow field. The numerical simulation agrees with the results of the experiment. The capacitance does not depend on a change in steam flow, and the capacitance of the sensor increases linearly with humidity.