Chemical Heat Transfer

Evaporator tubes are generally_____________________?

A. Horizontal
B. Vertical
C. Inclined
D. Random

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In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid?

A. Equal to
B. More than
C. Less than
D. Either more or less than (depending upon the fluid)

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Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?

A. Grashoff
B. Reynolds
C. Both ‘a’ & ‘b’
D. Prandtl & Grashoff

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Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________?

A. Existence of thermal boundary layer
B. Temperature gradient produced due to density difference
C. Buoyancy of the bubbles produced at active nucleation site
D. None of these

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Reason for operating an evaporator in multiple effects is to secure ___________________?

A. Increased steam economy
B. Decreased steam consumption
C. Both A. and B.
D. Increased capacity

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All analogy equations connecting friction factor and heat transfer co-efficient apply only to ___________________?

A. Wall or skin friction
B. Form friction
C. Both A. and B.
D. Turbulent flow

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Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?

A. U1 – U2
B. 1/U1 – 1/U2
C. 1/U2 – 1/U1
D. U2 – U1

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For a laminar flow of fluid in a circular tube, ‘h1’ is the convective heat transfer co-efficient at velocity ‘V1’. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is________________?

A. 1.26 h1
B. 0.794 h1
C. 0.574 h1
D. 1.741 h1

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A graph between _____________ is called Wilson plot?

A. (1/U) Vs. (1/v0.8)
B. (1/v0.8) Vs. U
C. v0.8 Vs . U
D. (1/U) Vs. (1/V)

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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

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