Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on?
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is
__________ paint has the minimum absorption co-efficient.
__________ paint has the minimum absorption co-efficient.
Which of the following has maximum thermal conductivity?
Which of the following has maximum thermal conductivity?
In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface.
In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface.
Heat transfer by natural convection is enhanced in system with
Heat transfer by natural convection is enhanced in system with
Which of the following has the minimum thermal conductivity?
Which of the following has the minimum thermal conductivity?
In a gas-liquid shell and tube heat exchanger, the
In a gas-liquid shell and tube heat exchanger, the
The number of kg vaporised per kg of steam fed to the evaporator is defined as
The number of kg vaporised per kg of steam fed to the evaporator is defined as
Boiling point elevation of a solution of NaOH
Boiling point elevation of a solution of NaOH
Steam economy in case of a triple effect evaporator will be
Steam economy in case of a triple effect evaporator will be
Which of the following has the highest thermal conductivity?
Which of the following has the highest thermal conductivity?
The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by
The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by
If Prandtl number is greater than the Schmidt number, then the
If Prandtl number is greater than the Schmidt number, then the
Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force.
Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force.
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient
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
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
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
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
For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
Which of the following has the lowest overall heat transfer co-efficient?
Which of the following has the lowest overall heat transfer co-efficient?
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because
Pick out the wrong statement.
Pick out the wrong statement.
Dropwise condensation of steam on cooling surface is promoted
Dropwise condensation of steam on cooling surface is promoted
Heat transfer occurs by natural convection because change in temperature causes difference in
Heat transfer occurs by natural convection because change in temperature causes difference in
The Grashoff number is defined as the ratio of the
The Grashoff number is defined as the ratio of the
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
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
In Fourier's law, the proportionality constant is called the
In Fourier's law, the proportionality constant is called the
If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
Crystallisation of solids from a homogeneous solution is a/an __________ process.
Crystallisation of solids from a homogeneous solution is a/an __________ process.
Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume that
Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume that
Which area is used in case of heat flow by conduction through a cylinder?
Which area is used in case of heat flow by conduction through a cylinder?
Which is the most suitable for the concentration of foamy & frothy liquors?
Which is the most suitable for the concentration of foamy & frothy liquors?
As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the
As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is
The value of Stefan-Boltazman constant in SI unit is
The value of Stefan-Boltazman constant in SI unit is
The purpose of providing a 'catchall' in the vapor line of an evaporator is to
The purpose of providing a 'catchall' in the vapor line of an evaporator is to
For specified tube outside diameter, higher BWG means higher
For specified tube outside diameter, higher BWG means higher
In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
In an extended surface heat exchanger, fluid having lower co-efficient
In an extended surface heat exchanger, fluid having lower co-efficient
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
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
A __________ surface has the maximum thermal emissivity out of the following.
A __________ surface has the maximum thermal emissivity out of the following.
Kg of liquid evaporated per hour in an evaporator is defined as its
Kg of liquid evaporated per hour in an evaporator is defined as its
Presence of a non-condensing gas in a condensing vapour
Presence of a non-condensing gas in a condensing vapour
In case of evaporators, liquid entrainment results primarily due to
In case of evaporators, liquid entrainment results primarily due to
Pick out the wrong statement.
Pick out the wrong statement.
Pick out the wrong statement.
Pick out the wrong statement.
Circulation pump is located below the evaporater to
Circulation pump is located below the evaporater to
Dropwise condensation occurs on __________ surfaces.
Dropwise condensation occurs on __________ surfaces.
Reason for operating an evaporator in multiple effect is to secure
Reason for operating an evaporator in multiple effect is to secure
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
With increase in temperature, the thermal conductivity of most liquids
With increase in temperature, the thermal conductivity of most liquids
Nucleate boiling is promoted
Nucleate boiling is promoted
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is
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.
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.
Black liquor generated during paper manufacture is concentrated in a
Black liquor generated during paper manufacture is concentrated in a
__________ equation relates the thermal conductivity of a solid to its temperature.
__________ equation relates the thermal conductivity of a solid to its temperature.
Rate of heat transfer by vaporisation from pools of water is affected by the
Rate of heat transfer by vaporisation from pools of water is affected by the
'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a
'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a
Pick out the wrong statement.
Pick out the wrong statement.
1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.
1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.
In counter flow compared to parallel flow,
In counter flow compared to parallel flow,
Low thermal conductivity of heat insulating materials is due to its
Low thermal conductivity of heat insulating materials is due to its
__________ heat exchanger is used for chilling oil to be dewaxed.
__________ heat exchanger is used for chilling oil to be dewaxed.
Reynold's analogy states that (where, St = Stanton number f = friction factor)
Reynold's analogy states that (where, St = Stanton number f = friction factor)
Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.
Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.
Multipass heat exchangers are used
Multipass heat exchangers are used
Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity?
Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity?
In a shell and tube heat exchanger, the shell side fluid velocity can not be changed by changing the
In a shell and tube heat exchanger, the shell side fluid velocity can not be changed by changing the
The actual temperature drop across the heating surface in an evaporator depends on the
The actual temperature drop across the heating surface in an evaporator depends on the
Mechanical recompression evaporation is used in the production of
Mechanical recompression evaporation is used in the production of
In sub-cooled boiling,
In sub-cooled boiling,
Steam traps are provided in steam carrying pipelines to
Steam traps are provided in steam carrying pipelines to
A black body when hot, emits heat radiation of __________ wavelengths.
A black body when hot, emits heat radiation of __________ wavelengths.
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about
The absorptivity of a body is equal to its emissivity
The absorptivity of a body is equal to its emissivity
Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.
Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.
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
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
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
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
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe )
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe )
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe?
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe?
The Stefan-Boltzman constant depends on the
The Stefan-Boltzman constant depends on the
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because
Which of the following has maximum thermal conductivity at the same temperature?
Which of the following has maximum thermal conductivity at the same temperature?
Value of Prandtl number for water ranges from
Value of Prandtl number for water ranges from
In the equation Q = UAΔt; Δt is
In the equation Q = UAΔt; Δt is
With increase in temperature, the thermal conductivity of fresh lubricating oil
With increase in temperature, the thermal conductivity of fresh lubricating oil
Pick out the correct statement.
Pick out the correct statement.
Thermal conductivity of a conducting solid material depends upon its
Thermal conductivity of a conducting solid material depends upon its
Kirchoff's law is applicable to
Kirchoff's law is applicable to
Pick out the correct statement.
Pick out the correct statement.
For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone.
For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone.
A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires
A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires
Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.
Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.
In SI units, thermal conductivity is expressed in
In SI units, thermal conductivity is expressed in
A hot body will radiate heat most rapidly, if its surface is
A hot body will radiate heat most rapidly, if its surface is
Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)
Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)
A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
