What is the logarithmic mean of r1 and r2 ?

A. (r1 – r2)/ln(r1/r2)
B. (r1 – r2)/ln(r2/r1)
C. (r2 – r1)/ln(r1/r2)
D. (r1 – r2)/-ln(r1/r2)

Multiple effect evaporators ar used to___________________?

A. Increase the steam economy & decrease the capacity
B. Increase the steam economy & the capacity
C. Decrease the steam economy & the capacity
D. Decrease the steam economy & increase the capacity

In a forward feed multiple effect evaporator unit__________________?

A. Viscosity of liquid is highest in first effect
B. Transfer from effect to effect is done by pumps
C. No pump is required to withdraw the product from the last effect
D. None of these

For evaporation of viscous solution in a multiple effect evaporator, the preferred feeding scheme is _________________?

A. Forward
B. Backward
C. Parallel
D. None of these

Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?

A. 35.5
B. 43.75
C. 81.25
D. 48.25

Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately ?

A. 32
B. 37
C. 45
D. 50

Corrosiveness of steam condensate is due to the presence of________________?

A. CO2
B. Dissolved O2
C. Both A. & B.
D. Neither A. nor B.

In sub-cooled boiling ?

A. Temperature of the heating surface is less than the boiling point of the liquid
B. Temperature of the heating surface is more than the boiling point of the liquid
C. Bubbles from heating surface are absorbed by the mass of the liquid
D. Very large vapour space is necessary

Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?

A. Convection becomes important
B. Conduction becomes important
C. Radiation becomes important
D. Sub-cooled boiling occurs

The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?

A. Heat flux
B. Nusselt number
C. Prandtl number
D. Schmidt number