Local Heat Transfer Process for a Gas–Liquid System in a Wall Region of an Agitated Vessel Equipped with the System of CD6-RT Impellers

Abstract

The results of the experimental studies of local heat process for a gas–liquid system in the region of the cylindrical wall of an agitated vessel equipped with the system of CD 6–RT impellers are presented. A lower CD 6 impeller (Smith turbine) and upper RT impeller (Rushton turbine) were located on the common shaft in a baffled agitated vessel of inner diameter equal to 0.3 m. Liquid height in the agitated vessel was equal to 0.6 m. Newtonian liquids of different physical properties were used as a continuous phase. Air was dispersed in the liquid. Local heat transfer coefficients were measured using both thermal and electrochemical methods. In total, 2280 experimental points were obtained. Distributions of the heat transfer coefficients were described by means of eqs 12–17 and 18–23 as a function of the Re and Pr numbers, dimensionless axial coordinate z/H, and modified Fr g number, separately, for turbulent and transitional ranges of the fluid flow in the agitated vessel. Equations 12–17 and 18–23, concerning both coalescing and noncoalescing gas–liquid systems, have no equivalent in the open literature.

Experimental Modelling of Local Heat Transfer Process for a Gas-liquid System in an Agitated Vessel with the System of A 315 – RT ImpellersExperimental Modelling of Local Heat Transfer Process for a Gas-liquid System in an Agitated Vessel with the System of A 315 – RT Impellers

“…Distributions of the heat transfer coefficient on the side of the fluid in a jacketed, baffled agitated vessel strongly depend on the impeller type. This statement confirms the results of local heat transfer obtained for different single impellers, (for example, centrally located Rushton turbine 12,18,19,29 , six-bladed PBT 30,31 , Pfaudler 32,33 , HE 3 23,24 , CD 6 26,27 , four-bladed pitched paddle 19 or MR210 impeller 19 and off-centred propeller 20,33 , HE 3 20,34 , A 315 17 or Rushton turbine 17 ) as well as for two impellers on a common shaft 22,[35][36][37] .…”

“…The results of the mean heat transfer coefficient have been given in literature for different agitated liquids, for example: viscous fluids 7-10 , non-Newtonian fluids [10][11][12][13][14] and others [15][16] . The measurements of the local heat transfer coefficient have been also carried out for liquid [17][18][19][20][21] , gas-liquid [21][22][23][24][25][26] , solid-liquid 27 and gas-solid-liquid 28 systems.…”

“…However, knowledge of the values of heat transfer coefficients, mean for whole wall of the agitated vessel, is insufficient because, in this way, the regions of different intensity of heat transfer cannot be identified on the heat transfer surface area. For this reason, quantitative analysis of the distributions of heat transfer coefficient in a jacketed, baffled, agitated vessel equipped with two impellers on a common shaft was carried out by Karcz 25 and Bielka et al 22 Karcz 25 performed an experimental study of the distributions of heat transfer coefficient along the wall of the tall agitated vessel equipped with a dual Rushton turbine system. The measurements were performed in a vessel of inner diameter T = 0.3 m, filled with a liquid up to height H = 2T.…”

“…Bielka et al 22 developed experimental studies of the distributions of heat transfer coefficient on the cylindrical wall of the tall agitated vessel equipped with two high-speed impellers. The system with lower CD 6 impeller (Smith turbine) and upper Rushton turbine was used to agitate air-Newtonian liquid systems within the transitional and turbulent range of the fluid flow.…”

Numerical analysis of momentum transfer processes in a mechanically agitated air – biophase – liquid system

“…Reduced cavities formed behind the blades compared to those for the Rushton turbine (Bakker, 2000) can be mentioned as the main advantages of the CD 6 impeller. Literature survey on different applications of the turbine impeller with curved blades shows that experimental studies concerning power consumption and mass and heat transfer were carried out mainly by Bielka et al (2014); Frijlink (1987); Karcz and Kamińska-Borak (1997); Rielly et al (1992); Sensel et al (1993); Smith and Katsanevakis (1993); Van't Riet et al (1976); Warmoeskerken and Smith (1989); Zhengming et al (1991). Karcz and Kamińska-Brzoska (1994a,b) studied experimentally the influence of the geometrical parameters of the turbine with concave and convex blades on power consumption and heat transfer process in the liquid phase.…”