Mass transfer in a jet device

Abstract

The process of mass transfer in a jet device has been investigated by the evaporation of water. Methods of calculating the interface formed by gas bubbles and measuring the mass-transfer coefficient have been developed. The experimental and calculated mass-transfer coefficients have been compared.Problems on the use of jet devices for initiation of mass-transfer processes were investigated at the Polotsk State University over the course of several years.To this point, jet devices have been used in the chemical industry mainly as blowers and ejectors [1]. The possibilities of using these devices for other purposes, e.g., in aeration systems or for effecting of a mass transfer between different media, are scantily known. The prospects of using jet devices in chemical engineering stem from their advantages over other analogous devices: the absence of rotating and rubbing parts and their simple design. Jet devices can operate in any flow of a substance (gas, liquid), which allows them to be used for initiation of biotechnological processes and intensification of mass transfer. With jet devices, the interface in a liquid layer can be increased without recourse to special contact devices. The use of jet devices also makes it possible to solve the problem of energy conservation, which is of great practical importance at present.It is agreed that the main characteristic of a mass-transfer process [2] is the ejection coefficient(1)The Mach number is used as the main criterion at large Reynolds numbers [2]:In the case where a gas is ejected by a jet of a liquid, friction forces arise on the surface of interaction of the liquid with the gas in the process of flow out of the liquid from a nozzle and a turbulence is formed in the liquid flow. In this case, the turbulence of the liquid flowing out from the nozzle (with a velocity of w liq + 15 m/sec) is characterized, as in aeromechanics, by the velocity of sound propagating in the liquid medium. This hydrodynamic criterion is described in detail in [3]. It was established experimentally that the quality of this ejection depends on the ratio between the diameters of the nozzle and the mixing chamber. In the case where cylindrical nozzles and air pits are used, the optimum ratio between their diameters is 0.22-0.23. The regularities of the mass transfer in a jet device were experimentally investigated on a laboratory test bed (Fig. 1).A laboratory jet device comprises a glass cylinder 1 clamped in a metal mandrel. An air pit 2, into which air is ejected by a water flow, is inserted into the cylinder. The pit serves to supply a low-moisture air for initiation of mass-transfer processes in an aerator. The water circulating around a closed path enters nozzle 8. The water pressure is determined by manometer 3. The ejected-air flow rate is measured by rotameter 6. Air enters the jet device through union 4. Continuous circulation of water in the system is provided by a centrifugal pump 5. The mixture of air with water vapor passes through union 7 to the atmosphere. The function of th...

Study on improving liquid carrying performance of annular jet pump gas well with static mixer

“…The degree of mixing between the working fluid and the sucked fluid has a significant impact on the performance of the jet pump 17 . The liquid‐gas jet mixes violently with the gas phase, forming a large contact area between the gas and liquid phases, which facilitates interphase mass transfer 18,19 . Therefore, improving the gas‐liquid mixing capacity of the annular jet pump has a positive impact on improving the performance of the gas‐driven jet pump.…”