Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by
Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by
Use of transverse baffles in a shell and tube heat exchanger is done to increase the
Use of transverse baffles in a shell and tube heat exchanger is done to increase the
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
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
Grashhoff number is given by
Grashhoff number is given by
Radiation energy is emitted by all the substances, which are above
Radiation energy is emitted by all the substances, which are above
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is
The main purpose of providing fins on heat transfer surface is to increase the
The main purpose of providing fins on heat transfer surface is to increase the
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
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
Unsteady state heat conduction occurs, when
Unsteady state heat conduction occurs, when
The sum of reflectivity and absorptivity for an opaque body is equal to
The sum of reflectivity and absorptivity for an opaque body is equal to
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)
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)
Finned tube heat exchangers
Finned tube heat exchangers
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?
Fouling factor
Fouling factor
Nusselt number is the ratio of the
Nusselt number is the ratio of the
Which of the following is the most widely used heat insulating material for pipelines carrying steam?
Which of the following is the most widely used heat insulating material for pipelines carrying steam?
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
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
Dropwise condensation is promoted on a/an __________ surface.
Dropwise condensation is promoted on a/an __________ surface.
Which type of heat exchanger is preferred for heavy heat loads?
Which type of heat exchanger is preferred for heavy heat loads?
If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
Calburn analogy is applicable for the value of Prandtl number from
Calburn analogy is applicable for the value of Prandtl number from
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recomended is
In a shell and tube heat exchanger, floating head is used for
In a shell and tube heat exchanger, floating head is used for
Boiling point elevation of an ideal solution
Boiling point elevation of an ideal solution
Prandtl number for most of dry gases is about
Prandtl number for most of dry gases is about
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?
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?
What is the steam economy in case of a single effect evaporator system?
What is the steam economy in case of a single effect evaporator system?
For an ideal black body
For an ideal black body
The statement that "maximum wavelength of radiation is inversly proportional to the temperature" is __________ law.
The statement that "maximum wavelength of radiation is inversly proportional to the temperature" is __________ law.
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid?
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid?
LMTD for counterflow and prallel flow heat exchanger will be the same, when the
LMTD for counterflow and prallel flow heat exchanger will be the same, when the
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature)
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature)
The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.
The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.
The unit of heat transfer co-efficient in SI unit is
The unit of heat transfer co-efficient in SI unit is
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
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
In Biot number, the characteristic length used is the ratio of the __________ of the solid.
In Biot number, the characteristic length used is the ratio of the __________ of the solid.
The driving potential for the crystal growth during crystallisation is the __________ of the solution.
The driving potential for the crystal growth during crystallisation is the __________ of the solution.
The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is
The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger?
Film condensation is promoted on a/an __________ surface.
Film condensation is promoted on a/an __________ surface.
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
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
In forced circulation, the heating element is injected
In forced circulation, the heating element is injected
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface tempeature follows __________ law.
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface tempeature follows __________ law.
The actual temperature drop across the heating surface of an evaporator depends on the
The actual temperature drop across the heating surface of an evaporator depends on the
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
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
In pipe flow, heat is transferred from hot wall to the liquid by
In pipe flow, heat is transferred from hot wall to the liquid by
In SI units, fouling factor is expressed in
In SI units, fouling factor is expressed in
Which of the following has the minimum absorptivity?
Which of the following has the minimum absorptivity?
Log mean temperature difference (LMTD) cannot be used, if
Log mean temperature difference (LMTD) cannot be used, if
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is
Multiple effect evaporation accounts for
Multiple effect evaporation accounts for
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
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
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature)
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature)
In a cooling tower, water becomes cool by
In a cooling tower, water becomes cool by
Prandtl and Reynolds analogy are same, when Prandtl number is
Prandtl and Reynolds analogy are same, when Prandtl number is
The purpose of floating head in a heat exchanger is to
The purpose of floating head in a heat exchanger is to
Evaporator tubes are generally
Evaporator tubes are generally
Multiple effect evaporation is generally recommended, when the
Multiple effect evaporation is generally recommended, when the
In a single effect evaporator, the economy is
In a single effect evaporator, the economy is
All analogy equations connecting friction factor and heat transfer co-efficient apply only to
All analogy equations connecting friction factor and heat transfer co-efficient apply only to
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
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
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively)
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively)
Harmonic mean temperature difference is given by
Harmonic mean temperature difference is given by
In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid
In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid
Boiling of milk in an open vessel is an example of __________ boiling.
Boiling of milk in an open vessel is an example of __________ boiling.
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.
Baffles are provided in heat exchangers to increase the
Baffles are provided in heat exchangers to increase the
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is
Heat exchanger tubes are never made of
Heat exchanger tubes are never made of
__________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side.
__________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side.
Which of the following is not used as a medium for high temperature heating?
Which of the following is not used as a medium for high temperature heating?
What is the geometric mean of two heat transfer areas A₁ and A₂ ?
What is the geometric mean of two heat transfer areas A₁ and A₂ ?
Air is best heated with steam in a heat exchanger of
Air is best heated with steam in a heat exchanger of
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
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
Which of the following is directly concerned with the heat transfer?
Which of the following is directly concerned with the heat transfer?
In a shell and tube heat exchanger, square pitch compared to triangular pitch
In a shell and tube heat exchanger, square pitch compared to triangular pitch
In a backward feed multiple effect evaporator
In a backward feed multiple effect evaporator
Pick out the wrong statement.
Pick out the wrong statement.
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
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
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
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
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
Graetz number is given by
Graetz number is given by
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m²°C.
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m²°C.
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
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
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)
Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)
Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.
Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.
For what value of Prandtl number, St = f/2?
For what value of Prandtl number, St = f/2?
The purpose of providing expansion bellows in the shell of tubular exchanger is to
The purpose of providing expansion bellows in the shell of tubular exchanger is to
Pick out the wrong statement.
Pick out the wrong statement.
For what value of Prandtl number, the Col-burn analogy is valid?
For what value of Prandtl number, the Col-burn analogy is valid?
Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low
Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?
Among liquids, water has a comparatively high value of thermal conductivity, due to its
Among liquids, water has a comparatively high value of thermal conductivity, due to its
What is the emissivity of a black body?
What is the emissivity of a black body?
The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in lminar zone is related as
The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in lminar zone is related as
Evaporation by thermocompression results in the
Evaporation by thermocompression results in the
In the free convection regime of pool boiling, the heat flux is proportional to
In the free convection regime of pool boiling, the heat flux is proportional to
Stefen's block body radiation law can also be derived from __________ law.
Stefen's block body radiation law can also be derived from __________ law.
