Section A
Q1.
(a)
The cone and plate viscometer is used frequently to characterize the fluids. It consists of a flat plate and a rotating cone with a very obtuse angle (the angle between the cone surface and the plate is 0.5 degree). The apex of the cone just touches the plate surface and the liquid to be tested fills the narrow gap formed by the cone and the plate. For a particular fluid, the following data are obtained : | Speed of the cone (r.p.m.) | 10 | 20 | 30 | 40 | 50 | 60 |
|---|---|---|---|---|---|---|
| Apparent viscosity, η (Pa-s) | 0.121 | 0.139 | 0.153 | 0.159 | 0.172 | 0.178 | What kind of non-Newtonian fluid is this?
(b) A wall 2 cm thick is to be constructed from a material that has an average thermal conductivity of 1.3 W/m-°C. The wall is to be insulated with a material having an average thermal conductivity of 0.038 W/m-°C, so that the heat loss per square metre will not exceed 1830 W. Consider that the inner surface temperature is 1300 °C and the outer surface of insulation is exposed to environment at 30 °C (assume heat transfer coefficient of 10 W/m^2-°C). Calculate the thickness of insulation required.
(c)
What are the basic conditions necessary for application of Fenske equation to estimate the number of ideal trays required for separation in a distillation column?
A binary mixture of benzene and toluene having 40% benzene is to be separated at a rate of 20 tons/hour into a top product containing 95% benzene and a bottom product with 4% of it. Determine the number of ideal trays using Fenske equation, given that the relative volatility of benzene in the mixture is 2.5.
(d) Explain briefly the difference among a fan, a blower and a compressor.
(e) Briefly describe the working principle of a cooling tower.
