Q.1
Heat transfer co-efficient (h1) for liquids increases with
Q.2
A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?
Q.3
Choose the correct equation.
Q.4
Pick out the wrong statement.
Q.5
The most conducive surface for dropwise condensation to occur is the __________ surface.
Q.6
Natural convection is characterised by
Q.7
Absorptivity and refletivity of a perfect black body are respectively
Q.8
Reason for operating an evaporator in multiple effect is to secure
Q.9
In the equation Q = UAΔt; Δt is
Q.10
The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the
Q.11
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?
Q.12
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are
Q.13
Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the
Q.14
Stefan-Boltzman law applies to __________ body.
Q.15
Agitated film evaporator is suitable for concentrating __________ liquids.
Q.16
Baffle spacing
Q.17
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)
Q.18
If Prandtl number is greater than the Schmidt number, then the
Q.19
Pick out the wrong statement.
Q.20
The actual temperature drop across the heating surface in an evaporator depends on the
Q.21
Kg of liquid evaporated per hour in an evaporator is defined as its
Q.22
In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is
Q.23
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place
Q.24
In an extended surface heat exchanger, fluid having lower co-efficient
Q.25
Which of the following has maximum thermal conductivity?
Q.26
Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force.
Q.27
Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
Q.28
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe?
Q.29
The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by
Q.30
Boiling point elevation of a solution of NaOH
Q.31
Mechanical recompression evaporation is used in the production of
Q.32
At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical?
Q.33
For specified tube outside diameter, higher BWG means higher
Q.34
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
Q.35
Which of the following has the minimum thermal conductivity?
Q.36
A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time
Q.37
Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is
Q.38
Pick out the correct statement.
Q.39
Value of Prandtl number for water ranges from
Q.40
The Grashoff number is defined as the ratio of the
Q.41
A __________ surface has the maximum thermal emissivity out of the following.
Q.42
Rate of heat transfer by vaporisation from pools of water is affected by the
Q.43
The value of Stefan-Boltazman constant in SI unit is
Q.44
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always
Q.45
In counter flow compared to parallel flow,
Q.46
In case of a supercooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is
Q.47
Heat transfer occurs by natural convection because change in temperature causes difference in
Q.48
1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.
Q.49
A process stream of dilute aqueous solution flowing at the rate of10 Kg.s⁻¹ is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s⁻¹. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is
Q.50
Which of the following has maximum thermal conductivity at the same temperature?
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