For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

- a)increases
- b)decreases
- c)remains constant
- d)passes through a maxima

Correct answer is option 'D'. Can you explain this answer?

Rohit Vidhate answered • 3 weeks ago

D) passes through a maxima

Kk Vi asked • 2 hours ago

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, *N*_{Pr} = Prandtl number)

- a)
*N*_{Pr} - b)
*N*_{Pr}^{1/3} - c)
*N*_{Pr}^{-1} - d)
*N*_{Pr}^{-1/3}

Correct answer is option 'B'. Can you explain this answer?

In how many categories heat exchangers are classified on the basis of mechanical design of heat exchanger surface?

- a)2
- b)4
- c)1
- d)3

Correct answer is option 'D'. Can you explain this answer?

Shiv Mangal answered • Apr 10, 2020

Answer is B

compact heat exchanger also a part of this

compact heat exchanger also a part of this

Karan Gohil asked • 7 hours ago

The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)_{R} and the co-efficient of performance as a heat pump (COP)_{HP} are

- a)(COP)
_{R}= (COP)_{HP}= 0.6 - b)(COP)
_{R}= 2.5; (COP)_{HP}= 1.5 - c)(COP)
_{R}= 1.5; (COP)_{HP}= 2.5 - d)(COP)
_{R}= (COP)_{HP}= 2.5

Correct answer is option 'C'. Can you explain this answer?

Based upon the nature of heat exchange process, the heat exchangers are classified into how many categories

- a)1
- b)2
- c)3
- d)4

Correct answer is option 'C'. Can you explain this answer?

Shiv Mangal answered • Apr 10, 2020

In reality there are two types direct and indirect contact

indirect have two parts recuperate and regenerator

indirect have two parts recuperate and regenerator

What will be the surface area of the basin for a flow of 2*106 litre per day having a surface loading rate 10,000 litre/day/m^{2}?

- a)100
- b)200
- c)300
- d)400

Correct answer is option 'B'. Can you explain this answer?

SHUBHAM RANJAN answered • Apr 01, 2020

Explanation: Surface area of basin= flow of water/surface loading rate = 2000000/10000=200m^{2}.

Sandeep Agrawal asked • 21 hours ago

Pick out the wrong statement.

- a)Orifice baffles are never used in a shell and tube heat exchanger.
- b)Pressure drop on the shell side of a heat exchanger depends upon tube pitch also.
- c)In a horizontal tube evaporator, surface blanketing by air is avoided.
- d)Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers.

Correct answer is option 'A'. Can you explain this answer?

Binary mixture of 100 kmol/hr enters into a flash drum has equimolar composition. The distillate obtained is 60 kmol/hr and the enthalpy of distillate, residue and feed are 500 KJ/kmol, 200 KJ/kmol and 400 KJ/kmol. Find the bottom flow rate in kmol/hr.

- a)10
- b)20
- c)30
- d)40

Correct answer is option 'C'. Can you explain this answer?

POOJA RAMESH answered • Apr 01, 2020

Explanation: -W/D = HD-HF/HW-HF

Where, HD, HW,HF are enthalpy of distillate, residue and feed.

-W/60 = -0.5

W= 30

Where, HD, HW,HF are enthalpy of distillate, residue and feed.

-W/60 = -0.5

W= 30

Which of the following is an example of forced convection?

- a)Chilling effect of cold wind on a warm body
- b)Flow of water in condenser tubes
- c)Cooling of billets in the atmosphere
- d)Heat exchange on cold and warm pipes

Correct answer is option 'B'. Can you explain this answer?

SHUBHAM CHOUDHARY answered • Feb 02, 2020

In forced convection the flow of fluid is caused by a pump, fan or by atmospheric winds.

What is the molecular weight of ammonia?

- a)31
- b)53
- c)29
- d)39

Correct answer is option 'C'. Can you explain this answer?

AMAN SAHAY answered • Feb 02, 2020

Formula of Sulphur-dioxide is SO _{2}.

Anshul Rasyotra asked • yesterday

200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, *N*_{c} = 0.5 x 10^{-3} kg/m^{2}.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m^{2}/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)

- a)0.5
- b)0.05
- c)0.1
- d)0.15

Correct answer is option 'C'. Can you explain this answer?

Reflectivity is defined as

- a)Fraction of total energy transmitted by the body
- b)Fraction of energy reflected by the body
- c)Fraction of total energy absorbed by the body
- d)Fraction of total energy absorbed and radiated by the body

Correct answer is option 'B'. Can you explain this answer?

UJJWAL PRIYADARSHI answered • Feb 02, 2020

It is total energy reflected by the body. Its value depends upon the nature of the surface of the body, its temperature and wavelength of incident radiations.

Radiant energy with an intensity of 800 W/m^{2} strikes a flat plate normally. The absorptivity is thrice the reflectivity and twice the transmissivity. Determine the rate of reflection

- a)518.20 W/m
^{2} - b)418.20 W/m
^{2} - c)318.20 W/m
^{2} - d)218.20 W/m
^{2}

Correct answer is option 'D'. Can you explain this answer?

MANAN PATHAK answered • Feb 02, 2020

Rate of reflection = pQ_{0 }= 218.20 W/m^{2}.

The value of reflectivity depends upon

(i) Body temperature

(ii) Wavelength of reflected radiation

(iii) Nature of surface of body

Identify the correct statement

(i) Body temperature

(ii) Wavelength of reflected radiation

(iii) Nature of surface of body

Identify the correct statement

- a)1 and 2
- b)2 and 3
- c)2 only
- d)1 and 3

Correct answer is option 'D'. Can you explain this answer?

VIVEK KUMAR answered • Feb 02, 2020

It should be wavelength of incident radiation. It is the fraction of total energy reflected by the body.

A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its face receives radiant energy from a heat source at the rate of 2 W. If heat transfer coefficient on both surfaces of the plate is stated to be 87.5 W/m 2 K, workout the energy lost by reflection

- a)0.8 W
- b)0.3 W
- c)0.9 W
- d)0.10 W

Correct answer is option 'C'. Can you explain this answer?

SUDHANSHU KUMAR answered • Feb 02, 2020

Heat loss by convection from both sides of the plates = 2 h A d t = 1.1 W. Energy lost by reflection = 2.0 – 1.1 = 0.9 W.

Which one is true for opaque body?

- a)Transmissivity is zero
- b)Reflectivity is zero
- c)Absorptivity is zero
- d)Reflectivity is unity

Correct answer is option 'A'. Can you explain this answer?

SHUBHAM RAJNISH answered • Feb 02, 2020

For opaque body, sum of absorptivity and reflectivity is unity.

A body that reflects all the incident thermal radiations is called a

- a)Opaque body
- b)Gases
- c)Black body
- d)Specular body

Correct answer is option 'D'. Can you explain this answer?

NIKHILESH SHARMA answered • Feb 02, 2020

In this case reflection is regular. For such bodies reflectivity is unity and transmissivity is equal to zero.

For a grey surface

- a)Reflectivity equals emissivity
- b)Emissivity equals transmissivity
- c)Absorptivity equals reflectivity
- d)Emissivity is constant

Correct answer is option 'D'. Can you explain this answer?

PURNESH KUMRAWAT answered • Feb 02, 2020

Emissivity is constant only for grey surfaces because grey surface radiates much more than any of the other surface.

What is the absorptivity of gray body?

- a)Below unity
- b)Unity
- c)2
- d)2.5

Correct answer is option 'A'. Can you explain this answer?

NISHANT BHARDWAJ answered • Feb 02, 2020

Gray body absorbs a certain fixed percentage of impinging radiations.

Electromagnetic waves strikes a hot body maintained at 900 degree Celsius which has a reflectivity of 0.66 and a transmissivity of 0.022. Let the absorbed flux be 60 W/m^{2}. Determine the rate of incident flux

- a)168.67 W/m
^{2} - b)178.67 W/m
^{2} - c)188.67 W/m
^{2} - d)198.67 W/m
^{2}

Correct answer is option 'C'. Can you explain this answer?

AMAN GUPTA answered • Feb 02, 2020

Absorptivity + Reflectivity + Transmissivity = 1. So, incident flux = 60/0.318 = 188.67 W/m^{2}.

Let 220 W/m^{2} of radiant energy is absorbed by a convex surface, 90 W/m^{2} is reflected and 40 W/m^{2} is transmitted through it. What is the value of absorptivity?

- a)0.72
- b)0.62
- c)0.52
- d)0.42

Correct answer is option 'B'. Can you explain this answer?

VED PRAKASH answered • Feb 02, 2020

It is the ratio of incident energy flow to that of absorbed radiations. Absorptivity = 220/(220 + 90 + 40) = 0.62.

The absorptivity of a surface depends upon

(i) Direction of reflected radiation

(ii) Temperature of the surface

(iii) Composition

Identify the correct statements

(i) Direction of reflected radiation

(ii) Temperature of the surface

(iii) Composition

Identify the correct statements

- a)1, 2 and 3
- b)1 and 3
- c)2 only
- d)2 and 3

Correct answer is option 'D'. Can you explain this answer?

KARAN SINGH answered • Feb 02, 2020

It depend upon the direction of incident radiation. Absorptivity is the fraction of total energy absorbed by the body.

Christine Joy asked • 3 days ago

Estimate the feed rate, if the composition of the more volatile component in the feed is 50% and the residue is 10% and the equilibrium relation is given by y*= 1.975x. Also the rate of residue is 60 mol/hr.

- a)213 mol/hr
- b)313 mol/hr
- c)413 mol/hr
- d)513 mol/hr

Correct answer is option 'B'. Can you explain this answer?

Absorptivity of a body is equal to its emissivity

- a)Under thermal equilibrium conditions
- b)For a polished surface
- c)At one particular temperature
- d)At shorter wavelengths

Correct answer is option 'A'. Can you explain this answer?

ABHISHEK KUMAR answered • Feb 02, 2020

In most case absorptivity of a body is equal to its emissivity under thermal equilibrium conditions.

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m^{2}. The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of absorption

- a)449.12 W/m
^{2} - b)349.12 W/m
^{2} - c)249.12 W/m
^{2} - d)149.12 W/m
^{2}

Correct answer is option 'B'. Can you explain this answer?

RAJAN KUMAR answered • Feb 02, 2020

Rate of absorption = (0.5455) (640) = 349.12 W/m^{2}.

Which quantity can be neglected for gases?

- a)Transmissivity
- b)Reflectivity
- c)Absorptivity
- d)None can be neglected

Correct answer is option 'B'. Can you explain this answer?

JATIN S answered • Feb 02, 2020

Gases are known to reflect very little of the radiation incident on their surface.

For laminar film condensation on a vertical plate, the gravitational acceleration g is replaced by

Where, α is the inclination angle with the horizontal

- a)4 g sin α
- b)3 g sin α
- c)2 g sin α
- d)g sin α

Correct answer is option 'D'. Can you explain this answer?

DEVANSH MUDGAL answered • Feb 01, 2020

It is replaced by sin α.

A plate condenser of dimensions l * b has been designed to be kept with side l in the vertical position. However due to oversight during erection and installation, it was fixed with side b vertical. How would this affect the heat transfer? Assume laminar conditions and same thermos-physical properties and take b = l/2

- a)The condenser should be installed with shorter side horizontal
- b)The condenser should be installed with longer side horizontal
- c)The condenser should be installed with longer side vertical
- d)The condenser should be installed with shorter side vertical

Correct answer is option 'D'. Can you explain this answer?

ROHIT UPADHYAY answered • Feb 01, 2020

h _{1} = 0.943 [k ^{3} p ^{2} g h _{f g}/δ l (t _{sat }– t _{s})] ^{0.25}, h_{2} = 0.943 [k ^{3} p ^{2} g h _{f g}/δ b (t _{sat }– t _{s})] ^{0.25}. So, h _{1}/h _{2 }= 0.8409.

For laminar film condensation on a vertical plate, the mass flow rate of the condensate per unit depth of the film at any position x is given by

- a)p g δ
^{3}/ 3 - b)p g δ
^{3}/ 3 σ - c)p g δ
^{2}/ 3 σ - d)p g δ
^{2}/ 3

Correct answer is option 'B'. Can you explain this answer?

ADARSH KUSHWAHA answered • Feb 01, 2020

Mass flow rate = mean flow velocity * flow area * density.

Ahmed Adel asked • 3 days ago

Radiant energy with an intensity of 800 W/m^{2} strikes a flat plate normally. The absorptivity is thrice the reflectivity and twice the transmissivity. Determine the rate of transmission

- a)155.47 W/m
^{2} - b)145.47 W/m
^{2} - c)135.47 W/m
^{2} - d)125.47 W/m
^{2}

Correct answer is option 'B'. Can you explain this answer?

Which of the following is a wrong statement in the context of convective heat transfer coefficient in laminar film condensation?The heat transfer coefficient varies as

- a)– ¼ power of acceleration due to gravity
- b)½ power of density of liquid
- c)¼ power of enthalpy of evaporation
- d)– ½ power of dynamic viscosity

Correct answer is option 'A'. Can you explain this answer?

PRINCE RAJ answered • Feb 01, 2020

h = 0.943 [k ^{3} p ^{2} g h _{f g}/δ l (t _{sat }– t _{s})] ^{0.25}. Further the heat transfer coefficient varies as ¼ power of acceleration due to gravity.

Mark the wrong statement with respect to laminar flow condensation on a vertical plate

- a)The rate of condensation heat transfer is maximum at the upper edge of the plate and progressively decreases as the lower edge is approached
- b)The average heat transfer coefficient is two third of the local heat transfer coefficient at the lower edge of the plate
- c)At a definite point on the heat transfer, the film coefficient is directly proportional to thermal conductivity and inversely proportional to thickness of film at the point
- d)The film thickness increases as the fourth root of the distance down the upper edge

Correct answer is option 'B'. Can you explain this answer?

MAYANK GUHA answered • Feb 01, 2020

The average heat transfer coefficient is 4/3 of the local heat transfer coefficient at the lower edge of the plate.

For laminar film condensation on a vertical plate, the film thickness is given by

- a)[4 k δ (t
_{sat}– t_{s}) x/p^{2}g h_{f g}]^{ 0.25} - b)[4 k δ (t
_{sat}– t_{s}) x/p^{2}g h_{f g}]^{ 0.5} - c)[4 k δ (t
_{sat}– t_{s}) x/p^{2}g h_{f g}]^{ } - d)[4 k δ (t
_{sat}– t_{s}) x/p^{2}g h_{f g}]^{ 1.5}

Correct answer is option 'A'. Can you explain this answer?

MEHAK THAKUR answered • Feb 01, 2020

The film thickness increases as the fourth root of the distance down the surface.

The critical Reynolds number for transition from laminar to turbulent film condensation is

- a)2000
- b)1900
- c)1800
- d)1700

Correct answer is option 'C'. Can you explain this answer?

SANGEETA BALDEV answered • Feb 01, 2020

This should be 1800 for perfect transition from laminar to turbulent film condensation.

Giridharan Ts asked • 5 days ago

A radiator in a domestic heating system operates at a surface temperature of 60 degree Celsius. Calculate the heat flux at the surface of the radiator if it behaves as a black body

- a)697.2 W/m
^{2} - b)786.9 W/m
^{2} - c)324.7 W/m
^{2} - d)592.1 W/m
^{2}

Correct answer is option 'A'. Can you explain this answer?

Ayush Kaushik asked • 6 days ago

Hot water (0.01 m^{3} /min) enters the tube side of a counter current shell and tube heat exchanger at 80ï¿½C and leaves at 50ï¿½C. Cold oil (0.05 m^{3}/min) of density 800 kg/m^{3} and specific heat of 2 kJ/kg.K enters at 20ï¿½C. The log mean temperature difference in ï¿½C is approximately

- a)32
- b)37
- c)45
- d)50

Correct answer is option 'A'. Can you explain this answer?

Radha Ganji asked • 2 weeks ago

Overall efficiency of the distillation column is

- a)the ratio of number of ideal plates to actual plates.
- b)the ratio of number of actual plates to ideal plates.
- c)same as the Murphree efficiency.
- d)always more than the point efficiency.

Correct answer is option 'A'. Can you explain this answer?

Shafi Shaik asked • 2 weeks ago

Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m^{2} and the solvent flow, rate is 400 moles of S/m^{2}. hr. The equilibrium data is represented by Y = 3X^{2} , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is

- a)25%
- b)50%
- c)70%
- d)90%

Correct answer is option 'B'. Can you explain this answer?

Radha Ganji asked • 2 weeks ago

Air initially at 101. 3 kPa and 40^{o}C and with a relative humidity of 50%, is cooled at constant pressure to 30^{o}C. The cooled air has a

- a)higher dew point.
- b)higher absolute (specific) humidity.
- c)higher relative humidity
- d)higher wet bulb temperature.

Correct answer is option 'C'. Can you explain this answer?

Sanidhya Chandola asked • 3 weeks ago

Suspended solid present in the waste water generated in blast furnace gas cooling and cleaning plant is removed by

- a)biological oxygen pond.
- b)radial settling tank (thickener) using coagulant (lime & ferrous sulphate).
- c)lagoons.
- d)filtration.

Correct answer is option 'B'. Can you explain this answer?

Manish Swaraj asked • 3 weeks ago

Relative humidity is the ratio of the

- a)partial pressure of the vapour to the vapour pressure of the liquid at room temperature.
- b)partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
- c)actual humidity to saturation humidity.
- d)none of these

Correct answer is option 'B'. Can you explain this answer?

Radha Ganji asked • 4 weeks ago

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s^{-1} is to be heated. Steam condensate at 95ï¿½C 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)counter flow with process stream on shell side.
- b)counter flow with process stream on tube side.
- c)parallel flow with process stream on shell side.
- d)parallel flow with process stream on tube side.

Correct answer is option 'A'. Can you explain this answer?

Krish Jat asked • 4 weeks ago

Sneha Jain asked • Apr 09, 2020

The average quantity of water (in lpcd) required for domestic purposes according to IS code is ________

- a)100
- b)120
- c)d) required for domestic purposes according to IS code is ________a) 100b) 120
- d)required for domestic purposes according to IS code is ________a) 100b) 120c) 70d) 135

Correct answer is option 'D'. Can you explain this answer?

ANKUSH RAJ asked • Mar 14, 2020

Consider an ideal vapour-liquid binary mixture, find the total pressure if the vapour pressure of A is 260 mmHg and the vapour pressure of B is 520 mmHg and the composition of A in mole fraction is 0.55.

- a)177 mmHg
- b)277 mmHg
- c)377 mmHg
- d)477 mmHg

Correct answer is option 'C'. Can you explain this answer?

CHAMELI DEVI asked • Mar 12, 2020

An oil cooler in a high performance engine has an outside surface area 0.12 m^{2} and a surface temperature of 65 degree Celsius. At any intermediate time air moves over the surface of the cooler at a temperature of 30 degree Celsius and gives rise to a surface coefficient equal to 45.4 W/ m 2 K. Find out the heat transfer rate?

- a)238.43 W
- b)190.68 W
- c)543.67 W
- d)675.98 W

Correct answer is option 'B'. Can you explain this answer?

SARITA DEVI asked • Feb 22, 2020

Water (specific heat = 4 k J/kg K) enters a cross flow exchanger (both fluids unmixed) at 15 degree Celsius and flows at the rate of 7.5 kg/s. It cools air (C _{P }= 1 k J/kg K) flowing at the rate of 10 kg/s from an inlet temperature of 120 degree Celsius. For an overall heat transfer coefficient of 780 k J/m^{2} hr degree and the surface area is 240 m^{2}, determine the NTU

- a)4.2
- b)5.2
- c)6.2
- d)7.2

Correct answer is option 'B'. Can you explain this answer?

MAMTA DEVI asked • Feb 21, 2020

In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1mm into the surface of the titanium slab is 0.25kg/m^{3} and at 3mm the concentration is 0.68kg/m^{3}. The rate at which the carbon is entering into its surface is 1.27*10-9kg/m^{2}.s. calculate the value of diffusion coefficient of carbon.

- a)5.91*10
^{-12} - b)5.91*10
^{-10} - c)5.91*10
^{-11} - d)5.91*10
^{-13}

Correct answer is option 'A'. Can you explain this answer?

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