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) Greater than that for un-insulated steam pipe (B) Less than that of the un-insulated steam pipe (C) Equal to that of the un-insulated steam pipe (D) Less than the steam pipe with 5 cms insulation

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) Greater than that for un-insulated steam pipe

(B) Less than that of the un-insulated steam pipe

(C) Equal to that of the un-insulated steam pipe

(D) Less than the steam pipe with 5 cms insulation


by

1 Answer

Answer :

(B) Less than that of the un-insulated steam pipe

by

Related questions

The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2 .K. At steady state, the temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Description : The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the ... temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Last Answer : (D) 48.7

. 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-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Description : . 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 ... from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

Last Answer : (A) 165.4

What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Last Answer : (A) 2

A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Description : A thin, flat & square plate measuring 2 m 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will ... heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Last Answer : (B) 100

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) 25°C (B) 30°C (C) 35°C (D) 40°C

Description : 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) 25°C (B) 30°C (C) 35°C (D) 40°C

Last Answer : (C) 35°C

Which of the following situations can be approximated to a steady state heat transfer system? (A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at 35°C (B) 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C (C) Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C (D) A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Description : Which of the following situations can be approximated to a steady state heat transfer system? (A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at ... flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Last Answer : (B) 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C

One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is (A) 100 (B) 900 (C) 9000 (D) 10000

Description : One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is (A) 100 (B) 900 (C) 9000 (D) 10000

Last Answer : (D) 10000

A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Description : A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Last Answer : (B) 0.025

Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the (A) Higher condensing film co-efficient is desired (B) Condensate is corrosive in nature (C) Lower pressure drop through the exchanger is desired (D) Temperature of the incoming vapor is very high Answer: Option B

Description : Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat ... drop through the exchanger is desired (D) Temperature of the incoming vapor is very high

Last Answer : (B) Supersaturated

Three materials A, B and C of equal thickness 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. (A) 40 (B) 95 (C) 70 (D) 50

Description : Three materials A, B and C of equal thickness 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 ... C will be at a temperature of __________ °C. (A) 40 (B) 95 (C) 70 (D) 50

Last Answer : (C) 70

A steam carrying pipeline is insulated with two layers of insulating materials with the inferior insulation material forming the inner part. If the two insulating layers are interchanged, the heat conducted will (A) Increase (B) Decrease (C) Remain unaffected (D) May increase or decrease; depends on the thickness of each layer

Description : A steam carrying pipeline is insulated with two layers of insulating materials with the inferior insulation material forming the inner part. If the two insulating layers are interchanged, the heat conducted ... ) Remain unaffected (D) May increase or decrease; depends on the thickness of each layer

Last Answer : Option C

Pick out the wrong statement. (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient (B) In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles (C) S.I. unit of fouling factor is Watt/m2 .°K (D) Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Description : Pick out the wrong statement. (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient (B) In a shell and tube heat exchanger ... surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Last Answer : (C) S.I. unit of fouling factor is Watt/m2 .°K

Overall heat transfer co-efficient for cooling of hydrocarbons by water is about (A) 50 -100 Kcal/hr.m2 .°C (B) 50 -100 W/m2 .°K (C) 50 -100 BTU/hr. ft. 2°F (D) 1000 - 1500 BTU/hr. ft. 2°F

Description : Overall heat transfer co-efficient for cooling of hydrocarbons by water is about (A) 50 -100 Kcal/hr.m2 .°C (B) 50 -100 W/m2 .°K (C) 50 -100 BTU/hr. ft. 2°F (D) 1000 - 1500 BTU/hr. ft. 2°F

Last Answer : (C) 50 -100 BTU/hr. ft. 2°F

Pick out the wrong statement. (A) The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonian fluids is (D/4L). ∆p (B) In the equation, T. gc = k. (du/dy) n the value of 'n' for pseudoplastic and Dilatant fluid are < 1 and >1 respectively (C) Shear stress for Newtonian fluid is proportional to the rate of shear in the direction perpendicular to motion (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

Description : Pick out the wrong statement. (A) The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonian fluids is (D/4L). ∆p (B) In the equation, T. gc = k. ... to motion (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

Last Answer : (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

A steam pipe is intended to be insulated with two layers of insulating materials of different thermal conductivities. For minimum heat transfer to take place (A) The better insulation material should be put just next to pipe (i.e., inside) (B) The better insulating material should be put outside (C) Either of the insulating material could be put on either side (D) Steam temperature is considered before deciding as to which insulating material is to be put inside (i.e., just next to the pipe)

Description : A steam pipe is intended to be insulated with two layers of insulating materials of different thermal conductivities. For minimum heat transfer to take place (A) The better insulation material should be put just ... to which insulating material is to be put inside (i.e., just next to the pipe)

Last Answer : (A) The better insulation material should be put just next to pipe (i.e., inside)

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?(A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Description : 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 ... wall temperature in degree centigrade? (A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Last Answer : (C) 81.25

Maximum heat dissipation occurs from a steel wire (k = 0.5 W/m. k) of 15 mm diameter exposed to air (h = 20W/m2.k), when the insulation thickness is __________ mm. (A) 15 (B) 25 (C) 10 (D) 30

Description : Maximum heat dissipation occurs from a steel wire (k = 0.5 W/m. k) of 15 mm diameter exposed to air (h = 20W/m2.k), when the insulation thickness is __________ mm. (A) 15 (B) 25 (C) 10 (D) 30

Last Answer : (B) 25

A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Description : A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Last Answer : (A) 7

A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness __________ metre. (A) 0.01 (B) 0.1 (C) 0.25 (D) 0.5

Description : A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of ... and thickness __________ metre. (A) 0.01 (B) 0.1 (C) 0.25 (D) 0.5

Last Answer : (B) 0.1

For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would (A) Decrease(B) Increase(C) First decrease and then increase(D) First increase and then decrease

Description : For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would (A) Decrease (B) Increase (C) First decrease and then increase (D) First increase and then decrease

Last Answer : (D) First increase and then decrease

A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is __________ °C. (A) 6 (B) 12 (C) 18 (D) 24

Description : A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature ... difference across the layer A is __________ °C. (A) 6 (B) 12 (C) 18 (D) 24

Last Answer : (B) 12

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/µ) 0.8 (CP .µ/k) 0.4 . This is valid for the value of NRe equal to (A) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

Description : Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/µ) 0.8 (CP .µ/k) 0.4 . This is valid for the value of NRe equal to (A) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

Last Answer : (D) > 10000

Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity (C) In unsteady state heat conduction, heat flows in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Description : Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the ... in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Last Answer : (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is (A) Always less than h1 (B) Always between h1 and h2 (C) Always higher than h2 (D) Dependent on metal resistance

Description : If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is (A) Always less than h1 (B) Always between h1 and h2 (C) Always higher than h2 (D) Dependent on metal resistance

Last Answer : (B) Always between h1 and h2

The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year ofoperation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co￾efficient at this time is(A) 1200 W/m2.K(B) 894 W/m2.K(C) 333 W/m2.K(D) 287 W/m2.K

Description : The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2 .K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2 .K. The overall heat transfer co￾efficient ... 1200 W/m2 .K (B) 894 W/m2 .K (C) 333 W/m2 .K (D) 287 W/m2 .K

Last Answer : (C) 333 W/m2 .K

The co-efficient of discharge of an orificemeter is a function of (A) Reynolds number at the orifice (B) Ratio of orifice dia to pipe dia (C) Both (A) and (B) (D) None of the above parameters, and has a constant value of 0.61

Description : The co-efficient of discharge of an orificemeter is a function of (A) Reynolds number at the orifice (B) Ratio of orifice dia to pipe dia (C) Both (A) and (B) (D) None of the above parameters, and has a constant value of 0.61

Last Answer : (C) Both (A) and (B)

Pick out the wrong statement. (A) Reciprocal of the resistance to heat flow is called thermal conductance (B) Unit of thermal conductance is W/°K (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A (D) None of these

Description : Pick out the wrong statement. (A) Reciprocal of the resistance to heat flow is called thermal conductance (B) Unit of thermal conductance is W/°K (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A (D) None of these

Last Answer : (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A

reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity (C) Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Description : reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by ... Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Last Answer : Option C

Select the correct statement. (A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meter(B) A Venturimeter with a given gage difference discharges at a greater rate,when the flow is vertically downward through it, than when the flow is verticallyupward(C) For a given pressure difference, the discharge of gas is greater through aVenturimeter, when compressibility is taken into account, than when it isneglected(D) The overall pressure loss is the same in a given pipe line, whether aVenturimeter or a nozzle with the same throat dia is used

Description : Sele(A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meterct the correct statement. (B) A Venturimeter with a given gage difference discharges at a ... a given pipe line, whether a Venturimeter or a nozzle with the same throat dia is used

Last Answer : (A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meterct the correct statement

Select the correct statement. (A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meter(B) A Venturimeter with a given gage difference discharges at a greater rate,when the flow is vertically downward through it, than when the flow is verticallyupward(C) For a given pressure difference, the discharge of gas is greater through aVenturimeter, when compressibility is taken into account, than when it isneglected(D) The overall pressure loss is the same in a given pipe line, whether aVenturimeter or a nozzle with the same throat dia is used

Description : Select the correct statement. (A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meter (B) A Venturimeter with a given gage difference discharges at a ... a given pipe line, whether a Venturimeter or a nozzle with the same throat dia is used

Last Answer : (A) The discharge through a Venturimeter depends upon Δp only and isindependent of orientation of the meter

Which of the following parameters is not responsible for the heat loss from a hot steam carrying bare pipe surface located in a room without fans? (A) Emissivity of pipe surface (B) Diameter & length of the pipe (C) Temperature of hot pipe surface & that of air in the room (D) None of thes

Description : Which of the following parameters is not responsible for the heat loss from a hot steam carrying bare pipe surface located in a room without fans? (A) Emissivity of pipe surface (B) Diameter & length of the pipe (C) Temperature of hot pipe surface & that of air in the room (D) None of thes

Last Answer : Option D

What is the unit of thermal conductivity? (A) Kcal/hr. m2 °C (B) Kcal/hr.m.°C (C) Kcal/hr.m (D) Kcal/hr. °C

Description : What is the unit of thermal conductivity? (A) Kcal/hr. m2 °C (B) Kcal/hr.m.°C (C) Kcal/hr.m (D) Kcal/hr. °C

Last Answer : (B) Kcal/hr.m.°C

Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Description : Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Last Answer : (B) Heat flux

In Joule's experiment, an insulated container contains 20 kg of waterinitially at 25°C. It is stirred by an agitator, which is made to turn by aslowly falling body weighing 40 kg through a height of 4 m. The process isrepeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglectingthe heat capacity of agitator, the temperature of water (in °C) is(A) 40.5(B) 34.4(C) 26.8(D) 25

Description : In Joule's experiment, an insulated container contains 20 kg of waterinitially 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 ... temperature of water (in °C) is (A) 40.5 (B) 34.4 (C) 26.8 (D) 25

Last Answer : (B) 34.4

The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. (A) Greater than (B) Lower than (C) Is same as (D) Half

Description : The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. (A) Greater than (B) Lower than (C) Is same as (D) Half

Last Answer : (B) Lower than

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Description : The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient ... pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Last Answer : (B) D-0.2

In sulphate pulp manufacture, the pressure and temperature in the digestor is (A) 10 atm., 800 °C (B) 10 atm., 170-180°C (C) 1 atm., 170 - 180°C (D) 1 atm., 800°C

Description : In sulphate pulp manufacture, the pressure and temperature in the digestor is (A) 10 atm., 800 °C (B) 10 atm., 170-180°C (C) 1 atm., 170 - 180°C (D) 1 atm., 800°C

Last Answer : (B) 10 atm., 170-180°C

Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. (A) No (B) The least (C) The largest (D) Lower

Description : Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. (A) No (B) The least (C) The largest (D) Lower

Last Answer : (C) The largest

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 (A) Vertical heat exchanger with steam on tube side (B) Vertical heat exchanger with steam on shell side (C) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

Description : 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 ... ) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

Last Answer : (B) Vertical heat exchanger with steam on shell side

. 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) Total heat transfer area of all the effects is -less than that in a single effect evaporator system (B) Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect (C) Boiling point elevation in a single effect system is much higher than that in any effect in a multi-effect system (D) Heat transfer co-efficient in a single effect is much lower than that in any effect in a multi-effect system

Description : . 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) Total heat transfer area of ... in a single effect is much lower than that in any effect in a multi-effect system

Last Answer : (B) Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect

Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s (D) The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Description : Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In ... layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Last Answer : (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s

Even though heat transfer co-efficient in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling. (A) Film (B) Nucleate (C) Transition (D) All modes of

Description : Even though heat transfer co-efficient in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling. (A) Film (B) Nucleate (C) Transition (D) All modes of

Last Answer : Option A

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) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Description : 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) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Last Answer : (B) 2K/h0

Should the house be insulated? 45 cm wall thickness

Description : The situation is that the wall thickness is 45 cm (ytong), we can not dismantle the insulated house. Thank you in advance for your help.

Last Answer : I supposedly don't need to insulate it anymore, its thermal insulation is so good, but if you don't have a problem doing it, I think you should do it. The good can be even better and will definitely pay off over the years. 

In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Description : In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Last Answer : (C) Thermal conductivity

Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Description : Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Last Answer : (A) Inversely with thermal conductivity

Utilizing the answer to the previous problem, estimate the overall or average increase in temperature ( ΔT) of the concrete roof from the energy absorbed from the sun during a12hour day. Assume that all of the radiation absorbed goes into heating the roof. The specific heat of concrete is about 900 J/kg, and the density is about 2,300 kg/m3 .  a. 7.9 °C  b. 8.9°C  c. 9.9°C  d. 10.9°C formula: ΔQ = m c ΔT

Description : Utilizing the answer to the previous problem, estimate the overall or average increase in temperature ( ΔT) of the concrete roof from the energy absorbed from the sun during a12hour day. Assume that all of the radiation absorbed goes into ... °C  b. 8.9°C  c. 9.9°C  d. 10.9°C formula: ΔQ = m c ΔT

Last Answer : 7.9 °C

Pick out the wrong statement: (A) Greater is the kinematic viscosity of the liquid, greater is the thickness of the boundary layer (B) Blowers develop a maximum pressure of 2 atmospheres (C) Friction losses in pipe fittings are generally expressed in terms of velocity heads (D) Fanning friction factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number

Description : Pick out the wrong statement: (A) Greater is the kinematic viscosity of the liquid, greater is the thickness of the boundary layer (B) Blowers develop a maximum pressure of 2 atmospheres ( ... factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number

Last Answer : (C) Friction losses in pipe fittings are generally expressed in terms of velocity heads