Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

Abstract

Experimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel.

Optimization principles for convective heat transfer

“…4(a) to effectively enhance the heat-transfer performance. This design agree qualitatively with the experimental data [41], where the impeller is eccentrically located and the local heat-transfer coefficient at the boundary near the impeller is larger than the other boundaries.…”

“…Stirring is a typical example where convection is introduced to boost heat transfer by constantly change the temperature profile and fluid velocity field in the stirrer. Delaplace [10], Karcz [11], Schafer [12], Cudak [41], Cho [42] and Yapici [43] analyzed the influences of configurations, rotating velocity, frequency, eccentrically located impeller on the heat-transfer coefficient, and then optimize the above parameters to obtain a better fluid flow pattern with a relative higher heat-transfer coefficient. As we know, the flow pattern determines the convective heat-transfer performance for a given fluid and certain boundary conditions, however in most cases the best flow pattern is unknown before optimization.…”

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.…”

Liquid‐Solid Mass Transfer Behavior of a Stirred‐Tank Reactor with a Fixed Bed at Its Bottom

“…Considering the drawbacks of slurry reactors, such as catalyst attrition due to collision of the particles with themselves or with the rotating impeller, the low rate of mass transfer between the particles and the solution due to the low slip velocity 1 which tend to reduce the reactor productivity, the possible overflow of catalyst particles outside the reactor in case of continuous operation, erosion of the impeller blades 2, and the labor involved in separating the final product from the catalyst particle, other modes of fixing the catalyst inside the reactor were suggested. The liquid‐solid mass and heat transfer behaviors of the walls of a rectangular and cylindrical agitated vessel where the solid catalyst can be fixed was studied by different authors 3–10. The disadvantages of using the agitated vessel wall as a catalyst support is the limited area of the vessel wall and hence the low reactor productivity.…”