Experimental study of agitator geometry and speed on heat transfer coefficients for both Newtonian and time dependent Po
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ORIGINAL
Experimental study of agitator geometry and speed on heat transfer coefficients for both Newtonian and time dependent Power law fluids S. K. Ansar Ali 1 Received: 15 June 2019 / Accepted: 10 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Experimental studies on heat transfer coefficients were carried out of Newtonian and time dependent power law fluids in mechanically agitated vessel. Three different Non-Newtonian fluids containing 0.5%(n = 0.973), 1%(n = 0.851), 2%(n = 0.793) CMC (Carboxy Methylcellulose) and water were studied in the coil and 1, 2 and 4 percentages (n = 0.698) NonNewtonian solutions of CMC in the test vessel. In this section of investigation we are focusing on heat transfer from wall to agitated vessel. In order to find results, the entire experimental data were discussed for jacketed vessel in three different impeller diameter and different speeds. It has been observed that a Modified Wilson plot is most appropriate for finding individual heat transfer coefficients. Data of 1, 2 and 4% CMC, for three impeller diameters, has been correlated and the overall heat transfer coefficient have been approximated with standard deviation 8.03%. Keywords Agitated vessel . Agitator geometry . Agitator speed . Heat transfer coefficients . Aqueous solutions . Modified Wilson plot Nomenclature Aj surface area of the jacketed vessel wall available for heat transfer, cm2 b1, b2, b3, c1 constants CMC Carboxy Methylcellulose Da agitator diameter, cm DT diameter of the agitated vessel H Height if the fluid level hj heat transfer coefficient for jacketed vessel wall to fluid, Kcal/hr. m2 0C K’ consistency index, gm. sec n’-2/cm k thermal conductivity n flow behavior index N speed (rpm) Qj heat transfer rate from the jacketed vessel surface, Kcal/min t time, sec T bulk temperature of the vessel fluid, 0C Tji inlet fluid temperature in the jacket, 0C * S. K. Ansar Ali [email protected] 1
Department of Mechanical Engineering, MIET, 250005 Meerut, India
Ti Ts Uj NNu NNuj N”Rea N’’pr Yj
inlet temperature surface temperature jacket overall heat transfer coefficient, Kcal/hr. m2 Nusselt number, h D/k Nusselt number, hj DT/k Reynolds number Prandtl number Resistance of the jacket side
Greek symbols µ Viscosity, gm. /cm sec µab shear or apparent viscosity at bulk temperature µaw shear or apparent viscosity at the wall temperature µd differential viscosity, gm. /cm sec ρ Density, gm. /cm3 c Specific heat, Cal/gm0C p Ψ, Ø Constants in equations (5), (9) Subscripts j jacket c coil i inner, inlet o outlet, outer
Heat Mass Transfer
1 Introduction In mechanically agitated vessel the agitators or impellers are classified as proximity and non-proximity agitators. When the blades of agitator move close to the test vessel surface they are called non-proximity agitators and when the impeller blades rotate with specified gap from the surface of the vessel they are called the proximity agitators. The non-proximity impellers are generally used for medium viscous fluids. They are generally
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