The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by (A) Painting the surface black (B) Painting the surface white (with aluminium paint) (C) Giving the surface a mirror finish (D) Roughening the surface

The heat transfer by radiation from a mild steel surface is to be

reduced by reducing the emissivity of the surface. This can be best achieved

by

(A) Painting the surface black

(B) Painting the surface white (with aluminium paint)

(C) Giving the surface a mirror finish

(D) Roughening the surface

by

1 Answer

Answer :

(B) Painting the surface white (with aluminium paint)

by

Related questions

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

Tar is a better fuel than furnace oil, because of its (A) Higher calorific value (B) Lower sulphur content (C) Higher emissivity (0.8-0.9) resulting in higher radiation heat transfer rate (D) Both (A) and (B)

Description : Tar is a better fuel than furnace oil, because of its (A) Higher calorific value (B) Lower sulphur content (C) Higher emissivity (0.8-0.9) resulting in higher radiation heat transfer rate (D) Both (A) and (B)

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

Calculate the rate of heat transfer by radiation from an unlagged steam pipe, 50 mm o.d. at 393K to air at 293K emissivity e = 0.9.

Description : Calculate the rate of heat transfer by radiation from an unlagged steam pipe, 50 mm o.d. at 393K to air at 293K emissivity e = 0.9.

Last Answer : Rate of heat transfer by radiation Assume length of pipe = 1 m

A __________ surface has the maximum thermal emissivity out of the following. (A) Black & smooth (B) Black & rough (C) White & smooth (D) White & rough

Description : A __________ surface has the maximum thermal emissivity out of the following. (A) Black & smooth (B) Black & rough (C) White & smooth (D) White & rough

Last Answer : (B) Black & rough

While painting with Aluminium paint, a little quantity of ………..shall be added to the paint while doing the first coat to distinguish it from the second coat a) little blue paint* b) lamp black c) red paint d) green paint

Description : While painting with Aluminium paint, a little quantity of ………..shall be added to the paint while doing the first coat to distinguish it from the second coat a) little blue paint* b) lamp black c) red paint d) green paint

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A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun? (A) Yellow paint (B) White paint (C) Black paint (D) Grey paint

Description : A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun? (A) Yellow paint (B) White paint (C) Black paint (D) Grey paint

Last Answer : (C) Black paint

In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) (A) α = 1; ε ≠ 1 (B) α ≠ 1, ε = 1 (C) α ≠ 1, ε ≠ 1 (D) α = 1; ε = 1

Description : In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) (A) α = 1; ε ≠ 1 (B) α ≠ 1, ε = 1 (C) α ≠ 1, ε ≠ 1 (D) α = 1; ε = 1

Last Answer : (D) α = 1; ε = 1

Best paint finish when painting a bathroom?

Description : Best paint finish when painting a bathroom?

Last Answer : When you are painting a bathroom you need to use a water resistant paint finish. There are many different brands, but as long as you get a water resistant finish you will not have problems with your bathroom paint.

Heat transfer rate to the charge/stock in a furnace does not depend upon the (A) Type of fuels viz. solid, liquid or gaseous (B) Flue gas temperature (C) Emissivity of refractory walls (D) Initial temperature of the charged stock

Description : Heat transfer rate to the charge/stock in a furnace does not depend upon the (A) Type of fuels viz. solid, liquid or gaseous (B) Flue gas temperature (C) Emissivity of refractory walls (D) Initial temperature of the charged stock

Last Answer : (A) Type of fuels viz. solid, liquid or gaseous

Heat transfer rate to the stock/charge in the furnace does not depend upon the(A) Emissivity of the refractory walls(B) Size of the furnace(C) Use of waste heat recovery equipments(D) Thickness of the stock

Description : Heat transfer rate to the stock/charge in the furnace does not depend upon the (A) Emissivity of the refractory walls (B) Size of the furnace (C) Use of waste heat recovery equipments (D) Thickness of the stock

Last Answer : (C) Use of waste heat recovery equipments

Oxyacetylene reducing flame is used while carrying out welding on (A) Alloy steel (B) Grey cast iron (C) Mild steel (D) High carbon steel

Description : Oxyacetylene reducing flame is used while carrying out welding on (A) Alloy steel (B) Grey cast iron (C) Mild steel (D) High carbon steel

Last Answer : (C) Mild steel

Oxyacetylene reducing flame is used while carrying out welding on (A) Alloy steel (B) Grey cast iron (C) Mild steel (D) High carbon steel

Description : Oxyacetylene reducing flame is used while carrying out welding on (A) Alloy steel (B) Grey cast iron (C) Mild steel (D) High carbon steel

Last Answer : Option C

Which of the following materials may prove unsuitable for handling acetic acid (glacial & anhydrous) at 40°C? (A) Silicone rubber, teflon, porcelain and wood (B) Nickel, monel, stainless steel and graphite (C) Aluminium, copper, high silicon iron (D) Brass, cast iron, mild steel and tin

Description : Which of the following materials may prove unsuitable for handling acetic acid (glacial & anhydrous) at 40°C? (A) Silicone rubber, teflon, porcelain and wood (B) Nickel, monel, stainless steel and graphite (C) Aluminium, copper, high silicon iron (D) Brass, cast iron, mild steel and tin

Last Answer : (D) Brass, cast iron, mild steel and tin

The preferred material of construction for storage tanks for 98% sulphuric acid is (A) Aluminium (B) Lead (C) Stainless steel 316 (D) Mild steel

Description : The preferred material of construction for storage tanks for 98% sulphuric acid is (A) Aluminium (B) Lead (C) Stainless steel 316 (D) Mild steel

Last Answer : (B) Lead

Acetaldehyde is produced by hydration of acetylene in a sulphuric acid solution of mercuric sulphate. Hydration tower is made of (A) Rubber lined mild steel (B) Lead lined mild steel (C) Aluminium (D) Cast iron

Description : Acetaldehyde is produced by hydration of acetylene in a sulphuric acid solution of mercuric sulphate. Hydration tower is made of (A) Rubber lined mild steel (B) Lead lined mild steel (C) Aluminium (D) Cast iron

Last Answer : (A) Rubber lined mild steel

H2SO4 (< 50% concentration) is corrosive to (A) Aluminium, mild steel, stainless steel, concrete & tin (B) Copper, cast iron & high silicon iron (14% Si) (C) Rubber (butyl and hard), silicone rubber & Teflon (D) Glass, graphite, porcelain & stoneware

Description : H2SO4 (< 50% concentration) is corrosive to (A) Aluminium, mild steel, stainless steel, concrete & tin (B) Copper, cast iron & high silicon iron (14% Si) (C) Rubber (butyl and hard), silicone rubber & Teflon (D) Glass, graphite, porcelain & stoneware

Last Answer : (A) Aluminium, mild steel, stainless steel, concrete & tin

100% H2SO4 at 30°C can't be stored in a vessel made/lined with (A) Cast iron and high silicon iron (B) Mild steel and stainless steel (C) Aluminium, tin and rubber (D) Teflon, glass and porcelain

Description : 100% H2SO4 at 30°C can't be stored in a vessel made/lined with (A) Cast iron and high silicon iron (B) Mild steel and stainless steel (C) Aluminium, tin and rubber (D) Teflon, glass and porcelain

Last Answer : (C) Aluminium, tin and rubber

Which of the following material of construction may be recommended by a chemical engineer for handling a gaseous chlorine (dry or wet) stream in a fluid flow system? (A) High silicon iron, silicon rubber, Kel-F and Teflon (B) Mild steel and stainless steel (C) Cast iron, tin and aluminium (D) Copper, nickel and Monel

Description : Which of the following material of construction may be recommended by a chemical engineer for handling a gaseous chlorine (dry or wet) stream in a fluid flow system? (A) High silicon iron, silicon rubber ... Mild steel and stainless steel (C) Cast iron, tin and aluminium (D) Copper, nickel and Monel

Last Answer : (A) High silicon iron, silicon rubber, Kel-F and Teflon

Solute atoms which cause yield point phenomenon in mild steel are/is (A) Aluminium (B) Boron (C) Carbon (D) Nitrogen

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Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by (A) Keeping the heat transfer surface clean (B) Enhancing the fluid pumping rate (C) Increasing the tube length (D) None of these

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Last Answer : (A) Keeping the heat transfer surface clean

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

Fuel economy in furnaces can be achieved by (A) Using oxygen enriched combustion air (B) Preheating the combustion air (C) Reducing the heat loss through furnace openings & doors (D) All (A), (B) and (C

Description : Fuel economy in furnaces can be achieved by (A) Using oxygen enriched combustion air (B) Preheating the combustion air (C) Reducing the heat loss through furnace openings & doors (D) All (A), (B) and (C

Last Answer : (D) All (A), (B) and (C

What is the meaning of the different symbols and abbreviations found on the documents that they use (such as surface finish to be achieved linear and geometric tolerances electronic components weld s?

Description : What is the meaning of the different symbols and abbreviations found on the documents that they use (such as surface finish to be achieved linear and geometric tolerances electronic components weld s?

Last Answer : Need answer

is usually used for brush rockers (a) Mild steel (b) Copper (c) Aluminium (d) Cast-iron

Description : is usually used for brush rockers (a) Mild steel (b) Copper (c) Aluminium (d) Cast-iron

Last Answer : (d) Cast-iron

What refers to the rate of thermal radiation emitter per unit area of a body?  A. Thermal conductivity  B. Absorptivity  C. Emissivity  D. Emissive power

Description : What refers to the rate of thermal radiation emitter per unit area of a body?  A. Thermal conductivity  B. Absorptivity  C. Emissivity  D. Emissive power

Last Answer : Emissive power

Radiation heat transfer rates does not depend upon the (A) Type of absorbing surface (B) Distance between the heat source and the object receiving the heat (C) Surface area and temperature of the heat source (D) None of these

Description : Radiation heat transfer rates does not depend upon the (A) Type of absorbing surface (B) Distance between the heat source and the object receiving the heat (C) Surface area and temperature of the heat source (D) None of these

Last Answer : (D) None of these

Which of the following has the least carbon percentage? (A) Low carbon steel (B) Mild steel (C) Wrought iron (D) White cast iron

Description : Which of the following has the least carbon percentage? (A) Low carbon steel (B) Mild steel (C) Wrought iron (D) White cast iron

Last Answer : (C) Wrought iron

Bush bearings are made of (A) Mild steel (B) Phosphorous bronze (C) White metal alloys (D) None of these

Description : Bush bearings are made of (A) Mild steel (B) Phosphorous bronze (C) White metal alloys (D) None of these

Last Answer : (B) Phosphorous bronze

Maximum heat transfer rate is achieved in __________ flow. (A) Co-current (B) Counter-current (C) Turbulent (D) Laminar

Description : Maximum heat transfer rate is achieved in __________ flow. (A) Co-current (B) Counter-current (C) Turbulent (D) Laminar

Last Answer : (C) Turbulen

Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace

Description : Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature? (A) Calorific value of the fuel (B) Flame temperature achieved (C) Speed of combustion of fuel (D) Heat transfer rate to the stock in the furnace

Last Answer : (A) Calorific value of the fuel

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2 . The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10 -8 W/m2 .K4 )(A) 1000(B) 727(C) 800(D) 1200

Description : The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2 . The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10 -8 W/m2 .K4 ) (A) 1000 (B) 727 (C) 800 (D) 1200

Last Answer : (A) 1000

Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be (A) 0.35 (B) 0.45 (C) 0.55 (D) 0.85

Description : Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be (A) 0.35 (B) 0.45 (C) 0.55 (D) 0.85

Last Answer : (B) 0.45

Pick out the wrong statement. (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment (B) The emissivity of a surface increases with increase in surface roughness (C) The emissivity of a polished surface is quite low (D) The emissivity of a non-metallic surface decreases with increase in the temperature

Description : Pick out the wrong statement. (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment (B) The emissivity of a surface increases with increase in surface roughness ... quite low (D) The emissivity of a non-metallic surface decreases with increase in the temperature

Last Answer : (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment

The heating capacity of muffle furnace depends on the (A) Surface area & emissivity of the stock (B) Properties of the muffle wall (temperature, area, and emissivity) (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : The heating capacity of muffle furnace depends on the (A) Surface area & emissivity of the stock (B) Properties of the muffle wall (temperature, area, and emissivity) (C) Both (A) & (B) (D) Neither (A) nor (B)

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

The heating capacity of continuous reheating furnace depends upon the (A) Hearth area and furnace temperature (B) Emissivity of the stock (C) Ratio of wall surface to stock surface (D) All (A), (B) and (C)

Description : The heating capacity of continuous reheating furnace depends upon the (A) Hearth area and furnace temperature (B) Emissivity of the stock (C) Ratio of wall surface to stock surface (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Name the paint used in A.T. Welding painting? (i) Black Paint (ii) Bituminous black IS:9862-1981.* (iii) Any type of black paint (iv) None of the above

Description : Name the paint used in A.T. Welding painting? (i) Black Paint (ii) Bituminous black IS:9862-1981.* (iii) Any type of black paint (iv) None of the above

Last Answer : (ii) Bituminous black IS:9862-1981.*

While painting with red oxide paint, a little quantity of ………..shall be added to the paint while doing the first coat to distinguish it from the second coat a) little blue paint b) lamp black* c) red paint d) green paint

Description : While painting with red oxide paint, a little quantity of ………..shall be added to the paint while doing the first coat to distinguish it from the second coat a) little blue paint b) lamp black* c) red paint d) green paint

Last Answer : b) lamp black*

For an ideal black body (A) Absorptivity = 1 (B) Reflectivity = 1 (C) Emissivity = 0 (D) Transmissivity = 1

Description : For an ideal black body (A) Absorptivity = 1 (B) Reflectivity = 1 (C) Emissivity = 0 (D) Transmissivity = 1

Last Answer : (A) Absorptivity = 1

While the total emissivity of a perfect black body is unity, the same for a real body is(A) 0(B) 1(C) > 1(D) Between 0 and 1

Description : While the total emissivity of a perfect black body is unity, the same for a real body is (A) 0 (B) 1 (C) > 1 (D) Between 0 and 1

Last Answer : (D) Between 0 and 1

What is the emissivity of a black body? (A) 0 (B) 1 (C) 0.5 (D) 0.90

Description : What is the emissivity of a black body? (A) 0 (B) 1 (C) 0.5 (D) 0.90

Last Answer : (B) 1

In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the (A) Rate of firing and emissivity of flame (B) Thermal conductivity of the charge & structural materials of furnace (C) Nature of process; whether batch, continuous or intermittent (D) All (A), (B) and (C)

Description : In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the (A) Rate of firing and emissivity of flame (B) Thermal conductivity of the charge & ... (C) Nature of process; whether batch, continuous or intermittent (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Pitch creosote mixture (PCM) as compared to furnace oil is a better fuel, because its (A) Emissivity factor is higher (B) Sulphur content is lower (C) Flue gas has lower dew point thereby facilitating more waste heat recovery (D) All (A), (B) and (C)

Description : Pitch creosote mixture (PCM) as compared to furnace oil is a better fuel, because its (A) Emissivity factor is higher (B) Sulphur content is lower (C) Flue gas has lower dew point thereby facilitating more waste heat recovery (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Which of the following options correctly explains the term heat budget? (1) It is a mode of transfer of heat through matter by molecular activity. (2) It is the balance between incoming and outgoing radiation. (3) It is the radiation from the earth in the form of long waves. (4) It is the amount of heat which the surface of earth receives from the sun.

Description : Which of the following options correctly explains the term heat budget? (1) It is a mode of transfer of heat through matter by molecular activity. (2) It is the balance between incoming and outgoing radiation. ... waves. (4) It is the amount of heat which the surface of earth receives from the sun.

Last Answer : (2) It is the balance between in-coming and outgoing radiation. Explanation: Incoming heat being absorbed by the Earth, and outgoing heat escaping the Earth in the form of radiation are both ... each passing year. This balance between incoming and outgoing heat is known as Earth's heat budget.

Which of the following options correctly explains the term heat budget? (1) It is a mode of transfer of heat through matter by molecular activity. (2) It is the balance between incoming and outgoing radiation (3) It is the radiation from the earth in the form of long waves. (4) It is the amount of heat which the surface of earth receives from the sun.

Description : Which of the following options correctly explains the term heat budget? (1) It is a mode of transfer of heat through matter by molecular activity. (2) It is the balance between incoming and outgoing radiation ... waves. (4) It is the amount of heat which the surface of earth receives from the sun.

Last Answer :  It is the balance between incoming and outgoing radiation

Higher fuel combustion efficiency cannot be achieved by (A) Preheating of fuel gases & combustion air (B) Reducing sulphur content in the fuel (C) Adopting proper fuel firing technique & fuel preparation (D) Supplying correct amount of combustion air

Description : Higher fuel combustion efficiency cannot be achieved by (A) Preheating of fuel gases & combustion air (B) Reducing sulphur content in the fuel (C) Adopting proper fuel firing technique & fuel preparation (D) Supplying correct amount of combustion air

Last Answer : (B) Reducing sulphur content in the fuel

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

The shovel of seed drill is made up of: A. Cast iron B. Mild steel C. White metal D. Carbon steel

Description : The shovel of seed drill is made up of: A. Cast iron B. Mild steel C. White metal D. Carbon steel

Last Answer : Carbon steel

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) t = 283 s (B) t = 356 s (C) t = 400 s (D) t = 800 s

Description : 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 ... = 283 s (B) t = 356 s (C) t = 400 s (D) t = 800 s

Last Answer : (D) t = 800 s

How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?

Description : How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?

Last Answer : A prerequisite to the hardening of steels is that martensite should be formed on cooling, but this can only be achieved if the rate of cooling is great enough to suppress the formation of pearlite or bainite and in plain carbon steels this can be achieved by quenching relatively small specimens