Q.1
Heat exchanger tubes are never made of
Q.2
If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
Q.3
In forced circulation, the heating element is injected
Q.4
The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m². The flux, when the element temperature is increased to 1000°C for the same furnace temperature is
Q.5
Pick out the wrong statement.
Q.6
Which of the following has the minimum absorptivity?
Q.7
The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m². The temperature of the inside wall is - 5°C. The outside wall temperature is
Q.8
The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as
Q.9
Radiation energy is emitted by all the substances, which are above
Q.10
The purpose of floating head in a heat exchanger is to
Q.11
Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the
Q.12
Grashhoff number is given by
Q.13
In a shell and tube heat exchanger, square pitch compared to triangular pitch
Q.14
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m²°C.
Q.15
LMTD for counterflow and prallel flow heat exchanger will be the same, when the
Q.16
For what value of Prandtl number, the Col-burn analogy is valid?
Q.17
Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.
Q.18
In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is
Q.19
Prandtl number for most of dry gases is about
Q.20
Which of the following is the most widely used heat insulating material for pipelines carrying steam?
Q.21
Air is best heated with steam in a heat exchanger of
Q.22
An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is
Q.23
In a shell and tube heat exchanger, floating head is used for
Q.24
What is the steam economy in case of a single effect evaporator system?
Q.25
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface)
Q.26
In pipe flow, heat is transferred from hot wall to the liquid by
Q.27
Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by
Q.28
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
Q.29
Fouling factor
Q.30
In SI units, fouling factor is expressed in
Q.31
Use of transverse baffles in a shell and tube heat exchanger is done to increase the
Q.32
Graetz number is given by
Q.33
The unit of heat transfer co-efficient in SI unit is
Q.34
The main purpose of providing fins on heat transfer surface is to increase the
Q.35
The actual temperature drop across the heating surface of an evaporator depends on the
Q.36
In Biot number, the characteristic length used is the ratio of the __________ of the solid.
Q.37
Finned tube heat exchangers
Q.38
For an ideal black body
Q.39
In a cooling tower, water becomes cool by
Q.40
Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. )
Q.41
Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately
Q.42
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
Q.43
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively)
Q.44
Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low
Q.45
In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms⁻². Neglecting the heat capacity of agitator, the temperature of water (in °C) is
Q.46
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is
Q.47
The sum of reflectivity and absorptivity for an opaque body is equal to
Q.48
Which of the following is not used as a medium for high temperature heating?
Q.49
Among liquids, water has a comparatively high value of thermal conductivity, due to its
Q.50
Evaporation by thermocompression results in the
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