Q.1
Which of the following is directly concerned with the heat transfer?
Q.2
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
Q.3
A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is
Q.4
Multiple effect evaporation accounts for
Q.5
All analogy equations connecting friction factor and heat transfer co-efficient apply only to
Q.6
In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is
Q.7
The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is
Q.8
The statement that "maximum wavelength of radiation is inversly proportional to the temperature" is __________ law.
Q.9
Log mean temperature difference (LMTD) cannot be used, if
Q.10
Evaporator tubes are generally
Q.11
Boiling of milk in an open vessel is an example of __________ boiling.
Q.12
Harmonic mean temperature difference is given by
Q.13
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 co-efficient is 3k/l. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?
Q.14
For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy
Q.15
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.
Q.16
Boiling point elevation for a strong and concentrated solution is found by Duhring's rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
Q.17
The purpose of providing expansion bellows in the shell of tubular exchanger is to
Q.18
Nusselt number is the ratio of the
Q.19
If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is
Q.20
Multiple effect evaporation is generally recommended, when the
Q.21
Pick out the wrong statement.
Q.22
The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is __________ compared to the same size pipes without fins.
Q.23
Heat transfer by radiation between two bodies at T₁ & T₂ and in an ambient temperature of Ta°C depends on
Q.24
Which of the following is correct?
Q.25
The type of liquor circulation system to be ' employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid.
Q.26
Pick out the wrong statement.
Q.27
Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around __________ BTU.
Q.28
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid?
Q.29
Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for
Q.30
Temperature profile in steady state heat transfer is
Q.31
The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m⁻².°C-1. The rate of heat loss from the outer surface in W.m-2is
Q.32
In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid
Q.33
Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is
Q.34
Baffles in the shell side of a shell and tube heat exchanger
Q.35
Double pipe heat exchangers are used
Q.36
Loss of heat from untagged steam pipe to the ambient air is by
Q.37
Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8 . Prn, is not valid, if the value of
Q.38
LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counterflow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.
Q.39
When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is
Q.40
With increase in temperature, the thermal conductivity of non-metallic amorphous solids
Q.41
The unit of heat transfer co-efficient is
Q.42
If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length
Q.43
Multiple effect evaporators ar used to
Q.44
Pick out the wrong statement.
Q.45
View factor is important in heat transfer by
Q.46
Thermal diffusivity is the most important in heat transfer by
Q.47
Three material A, B and C of equal thick-nes and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of __________ °C.
Q.48
Overall heat transfer co-efficient of a particular tube is U₁. If the same tube with some dirt deposited on either side has coefficient U₂, then
Q.49
A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an
Q.50
In evaporators, lowering the feed temperature
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