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.Management Sciences
Category: Chemical Heat Transfer
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _____________________?
A. 1200 W/m2.K
B. 894 W/m2.K
C. 333 W/m2.K
D. 287 W/m2.K
With increase in temperature, the thermal conductivity of steel___________________?
A. Increases
B. Decreases
C. Remains unchanged
D. Increases exponentially
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?
A. Increase
B. Decrease
C. Remain unchanged
D. Either increase or decrease; depends on the coolant flow rate
Pick out the wrong statement ?
A. The controlling resistance in case of heating of air by condensing steam is in the air fil
B. The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature
C. In case of a 1 – 2 shell and tube heat exchanger, the LMTD correction factor value increases
sharply, when a temperature cross occurs
D. Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature
Prandtl number is the ratio of________________?
A. Mass diffusivity to thermal diffusivity
B. Momentum diffusivity to thermal diffusivity
C. Thermal diffusivity to mass diffusivity
D. Thermal diffusivity to momentum diffusivity
Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
A. Corrosiveness & fouling characteristics
B. Pressure
C. Viscosity
D. Density
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
Vent pipes are provided in a condenser to ________________?
A. Remove non-condensable gases
B. Purge the condenser
C. Facilitate easy cleaning of tubes
D. None of these
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
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