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Experimental study of agitator geometry and speed on heat transfer coefficients for both Newtonian and time dependent Power law fluids

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) Non-Newtonian 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 \(\pm\)8.03%.

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Abbreviations

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

Ti :

inlet temperature

Ts :

surface temperature

Uj :

jacket overall heat transfer coefficient, Kcal/hr. m2

NNu :

Nusselt number, h D/k

NNuj :

Nusselt number, hj DT/k

N”Rea :

Reynolds number

N’’pr :

Prandtl number

Yj :

Resistance of the jacket side

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 p :

Specific heat, Cal/gm0C

Ψ, Ø:

Constants in equations (5), (9)

j:

jacket

c:

coil

i:

inner, inlet

o:

outlet, outer

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Correspondence to S. K. Ansar Ali.

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Ansar Ali, S.K. Experimental study of agitator geometry and speed on heat transfer coefficients for both Newtonian and time dependent Power law fluids. Heat Mass Transfer 56, 3167–3175 (2020). https://doi.org/10.1007/s00231-020-02881-2

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Keywords

  • Agitated vessel
  • Agitator geometry
  • Agitator speed
  • Heat transfer coefficients
  • Aqueous solutions
  • Modified Wilson plot