Chemical Engineering · all questions

Heat Transfer
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Q1

200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, N_c = 0.5 × 10^-3 kg/m².s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m²/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)

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Q2

It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/(kgK). The rate at which the heat has to be supplied in (kJ/min) to the evaporator is

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Q3

Fqra cold viscous feed, backward feed gives __________ than forward feed.

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Q4

In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head.

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Q5

Terminal point temperature differences between fluids in case of a heat exchanger is termed as

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Q6

For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is

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Q7

Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam.

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Q8

Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in °K)

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Q9

A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of

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Q10

The film co-efficient between condensing vapour and metal wall increases with

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Q11

The main function of baffles provided in a shell and tube heat exchanger is to

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Q12

The maximum heat transfer co-efficient from steam heating will be attained when the steam is

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Q13

The rate of emission of radiation by a body does not depend upon the

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Q14

In a multiple effect evaporator, the effect of boiling point elevation is to

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Q15

Which of the following is concerned with both heat and mass transfer?

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Q16

The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.

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Q17

(N_Gr × N_Pr) is called the __________ number.

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Q18

h.D/K is called the __________ number.

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Q19

A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to

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Q20

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m². The approximate surface temperature (K) is
(Stefan-Boltzman constant = 5.67 × 10^-8 W/m².K⁴)

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