Effect of Non-Ideal Mixing on Heat Transfer of non-Newtonian Liquids in a Mechanically Agitated Vessel
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Triveni Billa
Abstract
Effect of non-ideal mixing on heat transfer phenomena is studied in an anchor agitated vessel processed with viscous Newtonian and non-Newtonian fluids. Influence of critical variables such as rotational speed and properties of the fluid on heat transfer coefficient and heat transfer area has been investigated. Based on the flow pattern generated by an anchor agitator, a multi parameter model for quantifying the extent of non-ideality is developed and the parameters of the model, fraction of well mixed zone and the exchange flow rate are evaluated on the basis of tracer response data. Heat transfer experiments are also conducted under unsteady state conditions using same agitated vessel under similar operating conditions using Castor oil, Castor oil methyl esters (CME) and carboxy methyl cellulose (CMC 0.5 %, 1 %), soap solution as process fluids. Based on the results obtained from this analysis, a commercial scale reactor of a capacity of 20 Kl for saponification of hydrogenated castor oil has been designed using different scaleup rules. Power per unit volume found to give desirable results as it gives acceptable values for heat transfer coefficient and power consumption. Equal power per unit volume gives good mixing and high heat transfer coefficient with slightly higher power consumption and the error involved in heat transfer area calculation is small giving optimum cost of the experimental unit.
Nomenclature
- a:
Constant;
- A:
Heat transfer area, m2;
- B:
Equipment characteristic constant (for anchor 71.5);
- cp:
Specific heat of process fluid, J/kg °C;
- Cp:
Specific heat of service fluid, J/kg °C;
- CT1:
Tracer concentration in well mixed zone;
- CT2:
Tracer concentrations in dead zone;
- Dt:
Tank diameter, m;
- Di:
Impeller diameter, m;
- Di1:
Impeller diameter in lab scale unit, m;
- Di2:
Impeller diameter in commercial scale unit, m;
- g:
Acceleration due to gravity, m/s2;
- h:
Individual heat transfer coefficient, W/m2 °C;
- H:
Liquid level, m;
- k:
Thermal conductivity, W/m °C;
- Ks:
Shear rate constant;
- K:
Fluid consistency index, kg/m (s)2-n;
- M:
Process fluid mass, kg;
- n:
Flow behavior index;
- N:
Impeller speed, s−1;
- N1:
Impeller speed at lab scale, s−1;
- N2:
Impeller speed at commercial scale, s−1;
- P:
Power, W;
- Q:
Rate of heat transfer, J;
- Re:
Reynolds number, NDI2ρ/μapp;
- t:
Time, s;
- T:
Process fluid temperature, °C;
- ΔTln
Log-mean temperature difference, °C;
- U:
Overall heat transfer coefficient, W/m2 °C;
- U non-ideal:
Heat transfer coefficient calculated under non-ideal mixing conditions, W/m2 °C;
- V:
Volume of the reactant, m3;
- Vd:
Dead zone volume, m3;
- Vm:
Well-mixed zone volume, m3;
- W:
Service fluid mass flow rate in kg/s;
- Greek letters:
- α:
Fraction of well mixed volume;
- ρl:
Liquid density, kg/m3;
- ν:
Exchange flow rate between well mixed zone and dead zone;
- μapp:
Apparent viscosity of non-Newtonian fluid, kg/m-s;
- γavg:
Average shear rate, s−1;
- θ1, θ2:
Service fluid inlet and outlet temperatures °C;
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- Effect of Non-Ideal Mixing on Heat Transfer of non-Newtonian Liquids in a Mechanically Agitated Vessel
Artikel in diesem Heft
- Editorial
- To the Distinguished Contribution of Professor Gulsen Dogu and Professor Timur Dogu to Chemical Reaction Engineering
- Special Issue Articles
- Structural Property Improvements of Bentonite with Sulfuric Acid Activation and a Test in Catalytic Wet Peroxide Oxidation of Phenol
- Effect of Surface Area and Micropore Volume of Activated Carbons from Coal by KOH, NaOH and ZnCl2 Treatments on Methane Adsorption
- Using Volatile Organic Compounds in Waste Streams as Fuel
- Catalytic Decomposition of Ammonia for Hydrogen Production over Carbon Nanofiber Supported Fe and Mo Catalysts in a Microwave Heated Reactor
- Ethylene Hydrogenation in Pellets with Different Pore Structures, Measured in a One-Sided Single-Pellet Reactor
- Catalytic Performances of Bi-Metallic Ni-Co Catalysts in Acetic Acid Steam Reforming Reaction: Effect of Mg Incorporation
- PdIn Catalysts in a Continuous Fixed Bed Reactor for the Nitrate Removal from Groundwater
- Chemical Cross-Linking of 6FDA-6FPA Polyimides for Gas Permeation Membranes
- Revisiting Electrochemical Techniques to Characterize the Solid-State Diffusion Mechanism in Lithium-Ion Batteries
- Short Communications
- Effect of Non-Ideal Mixing on Heat Transfer of non-Newtonian Liquids in a Mechanically Agitated Vessel
