Recent questions and answers in Heat Transfer

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GATE2020-ME-2: 50
The spectral distribution of radiation from a black body at $T_1=3000 \: K$ has a maximum at wavelength $\lambda_{\text{max}}$. The body cools down to a temperature $T_2$ ... the original wavelength $\lambda_{\text{max}}$, then the temperature $T_2$ is _________ $K$ (round off to nearest integer)

go_editor asked in Heat Transfer Sep 18, 2020

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GATE2020-ME-1: 11
Match the following ... $P-3,\:Q-3,\:R-1\:,S-3$ $P-4,\:Q-3,\:R-2\:,S-1$

go_editor asked in Heat Transfer Feb 19, 2020

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GATE2020-ME-1: 25
In a concentric tube counter-flow heat exchanger, hot oil enters at $102^{\circ}C$ and leaves at $65^{\circ}C$. Cold water enters at $25^{\circ}C$ and leaves at $42^{\circ}C$. The log mean temperature difference $(LMTD)$ is ________ $^{\circ}C$ (round off to one decimal place).

go_editor asked in Heat Transfer Feb 19, 2020

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GATE2020-ME-1: 34
A small metal bead $(\text{radius}\: 0.5\: mm)$, initially at $100^{\circ}C$ , when placed in a stream of fluid at $20^{\circ}C$ , attains a temperature of $28^{\circ}C$ in $4.35$ ... heat transfer coefficient $(in\:W/m^{2}.K)$ between the metal bead and the fluid stream is $283.3$ $299.8$ $149.9$ $449.7$

go_editor asked in Heat Transfer Feb 19, 2020

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GATE2018-1-47
A plane slab of thickness $L$ and thermal conductivity $k$ is heated heated with a fluid on one side $(P)$, and the other side $(Q)$ is maintained at a constant temperature, $T_Q$ of $25^{\circ}C$ ... The steady state temperature, $T_P$ (in $^{\circ}$C) of the side which is exposed to the fluid is _____ (correct to two decimal places)

GG answered in Heat Transfer Apr 26, 2019

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GATE2019 ME-2: 10
Sphere $1$ with a diameter of $0.1$ m is completely enclosed by another sphere $2$ of diameter $0.4$m. The view factor $F_{12}$ is $0.0625$ $0.25$ $0.5$ $1.0$

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-2: 11
One-dimensional steady state heat conduction takes places through a solid whose cross-sectional area varies linearly in the direction of heat transfer. Assume there is no heat generation in the solid and the thermal conductivity of the material is constant and independent of temperature. The temperature distribution in the solid is Linear Quadratic Logarithmic Exponential

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-2: 24
A thin vertical flat plate of height $L$, and infinite width perpendicular to the plane of the figure, is losing heat to the surroundings by natural convection. The temperatures of the plate and the surroundings by natural convection. The temperatures of the plate and the ... plate is $h_1$ and that for the second plate is $h_2$, the value of the ratio $h_1/h_2$ is ____________

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-2: 46
Hot and cold fluids enter a parallel flow double tube heat exchanger at $100^{\circ}C$ and $15^{\circ} C$, respectively. The heat capacity rates of hot and cold fluids are $C_h=2000 \: W/K$ and $C_c =1200 \: W/K$, respectively. If the outlet ... $45^{\circ} C$, the log mean temperature difference (LMTD) of the heat exchanger is __________ $K$ (round off to two decimal places).

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-1: 11
A slender rod of length $L$, diameter $d$ $(L > >d)$ and thermal conductivity $k_1$ is joined with another rod of identical dimensions, but of thermal conductivity $k_2$, to form a composite cylindrical rod of length $2L$. The heat transfer in radial direction and ... composite rod is $k_1+k_2 \\$ $\sqrt{k_1k_2} \\$ $\dfrac{k_1k_2}{k_1+k_2} \\$ $\dfrac{2k_1k_2}{k_1+k_2}$

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-1: 21
A solid cube of side $1$ m is kept at a room temperature of $32^{\circ} C$. The coefficient of linear thermal expansion of the cube material is $1 \times 10^{-5} / ^{\circ}C$ and the bulk modulus is $200$ GPa. If the cube is constrained all around and heated uniformly to $42^{\circ}C$, then the magnitude of volumetric (mean) stress (in MPa) included due to heating is _______

Arjun asked in Heat Transfer Feb 9, 2019

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GATE2019 ME-1: 47
Three slabs are joined together as shown in the figure. There is no thermal contact resistance at the interfaces. The center slab experiences a non-uniform internal heat generation with an average value equal to $10000 \: Wm^{-3}$, while the left and right slabs have no ... $T_1$ is measured to be $100^{\circ} C$, the right extreme face temperature $T_2$ is ______$^{\circ} C$.

Arjun asked in Heat Transfer Feb 9, 2019

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GATE ME 2012 | Question: 52
Air enters an adiabatic nozzle at $300$ kPa, $500$ K with a velocity of $10$ m/s. It leaves the nozzle at $100$ kPa with a velocity of $180$ m/s. The inlet area is $80 cm^2$. The specific heat of air $C_p$ is $1008$ J/kg.K. The exit temperature of the air is $516$ K $532$ K $484$ K $468$ K

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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GATE ME 2012 | Question: 53
Air enters an adiabatic nozzle at $300$ kPa, $500$ K with a velocity of $10$ m/s. It leaves the nozzle at $100$ kPa with a velocity of $180$ m/s. The inlet area is $80 \: cm^2$. The specific heat of air $C_p$ is $1008$ J/kg.K. The exit area of the nozzle in $cm^4$ is $90.1$ $56.3$ $4.4$ $12.9$

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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GATE ME 2012 | Question: 42
A solid steel cube constrained on all six faces is heated so that the temperature rises uniformly by $\Delta T$. If the thermal coefficient of the material is $\alpha$, Young's modulus is $E$ and the Poisson's ratio is $\upsilon$, the thermal stress developed in the cube due to ... $-\dfrac{\alpha (\Delta T) E}{3 (1-2 \upsilon)}$

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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GATE ME 2012 | Question: 41
Water $(C_p=4.18 \: kJ/kg.K)$ at $80^{\circ} C$ enters a counterflow heat exchanger with a mass flow rate of $0.5 \: kg/s$. Air ($C_p=1 \: kJ/kg.K$) enters at $30^{\circ} C$ with a mass flow rate of $2.09 \: kg/s$. If the effectiveness of heat exchanger is $0.8$, the LMTD (in $^{\circ} C$) is $40$ $20$ $10$ $5$

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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GATE ME 2012 | Question: 18
Which one of the following configurations has the highest fin effectiveness? Thin, closely spaced fins Thin, widely spaced fins Thick, widely spaced fins Thick, closely spaced fins

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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GATE ME 2012 | Question: 4
During $\textit{normalizing} $ process of steel, the specimen is heated between the upper and lower critical temperature and cooled in still air above the upper critical temperature and cooled in furnace above the upper critical temperature and cooled in still air between the upper and lower critical temperature and cooled in furnace

Andrijana3306 asked in Heat Transfer Mar 20, 2018

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ISRO2009-9
The radiative heat transfer rate per unit area $(W/m2)$ between two plane parallel grey surfaces (emissivity $0.9$) maintained at $400 \: \text{K}$ and $300 \: \text{K}$ is (Stefan Bottzman constant $\sigma=5.67 \times 10^{-6} \;W/m^2K^4)$ $1020$ $464$ $812$ $567$

m2n037 asked in Heat Transfer Mar 6, 2018

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ISRO2009-4
The relation ${p^{V}}^{\gamma}=$ constant, where $\gamma$ is the ratio of the specific heats of ideal gas, is applicable to Any adiabatic process Only reversible adiabatic process Only irreversible adiabatic process Only isothermal process

m2n037 asked in Heat Transfer Mar 6, 2018

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GATE2018-2-54
Steam in the condenser of a thermal power plant is to be condensed at a temperature of $30^{\circ}C$ with cooling water which enters the tubes of the condenser at $14^{\circ}C$ and exists at $22^{\circ}C$ ... coefficient is $2000 \: W/m^2 \: K$. The heat transfer (in $MW$) to the condenser is _________ (correct to two decimal places).

Arjun asked in Heat Transfer Feb 17, 2018

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GATE2018-2-41
A $0.2 \:m$ thick infinite black plate having a thermal conductivity of $3.96 \: W/m-K$ is exposed to two infinite black surfaces at $300 \: K$ and $400 \: K$ as shown in the figure. At steady state, the surface temperature of the plate facing the ... $1-D$ heat conduction, the magnitude of the heat flux through the place (in $W/m^2$) is ___________ (correct to two decimal places)

Arjun asked in Heat Transfer Feb 17, 2018

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GATE2018-2-9
The peak wavelength of radiation emitted by a black body at a temperature of $2000 \: K$ is $1.45 \: \mu m$. If the peak wavelength of emitted radiation changes to $2.90 \: \mu m$, then the temperature (in $K$) of the black body is $500$ $1000$ $4000$ $8000$

Arjun asked in Heat Transfer Feb 17, 2018

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GATE2018-1-10
Which one of the following statements is correct for a superheated vapour? Its pressure is less than the saturation pressure at a given temperature Its temperature is less than the saturation temperature at a given pressure Its volume is less than the ... the saturated vapour at a given temperature Its enthalpy is less than the enthalpy of the saturated vapour at a given pressure

Arjun asked in Heat Transfer Feb 17, 2018

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GATE2016-3-52
Two optically flat plates of glass are kept at a small angle $\theta$ as shown in the figure. Monochromatic light is incident vertically. If the wavelength of light used to get a fringe spacing of $1$ $mm$ is $450$ $nm$, the wavelength of light (in $nm$) to get a fringe spacing of $1.5$ $mm$ is _________

Amit answered in Heat Transfer Apr 30, 2017

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GATE2017 ME-2: 46
In a counter-flow heat exchanger, water is heated at the rate of $1.5 \: kg/s$ from $40^{\circ}$ C to $80^{\circ} \: C$ by an oil entering at $120^{\circ}$ C and leaving at $60 ^{\circ}$ C. The specific heats of water and oil are $4.2 \: kJ/kg.K$ and ... transfer coefficient is $400 W/m^{2}.K$. The required heat transfer surface area (in $m^{2}$) is $0.104$ $0.022$ $10.4$ $21.84$

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-2: 47
A metal ball of diameter $60$ mm is initially at $220^{\circ}$ C. The ball is suddenly cooled by an air jet of $20^{\circ}$ C. The heat transfer coefficient is $200 W/m^{2}.K$ ... $^{\circ} C$) after $90$ seconds will be approximately $141$ $163$ $189$ $210$

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-2: 19
The emissive power of a blackbody is $P$. If its absolute temperature is doubled, the emissive power becomes $2 P$ $4 P$ $8 P$ $16 P$

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-2: 18
The heat loss from a fin is $6$ W. The effectiveness and efficiency of the fin are $3$ and $0.75$, respectively. The heat loss (in W) from the fin, keeping the entire fin surface at base temperature, is _______.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-2: 10
A steel bar is held by two fixed supports as shown in the figure and is subjected to an increase of temperature $\Delta T=100^{\circ}C$. If the coefficient of thermal expansion and Young's modulus of elasticity of steel are $11 \times 10^{-6}/^{\circ} C$ and $200$ GPa, respectively, the magnitude of thermal stress (in MPa) induced in the bar is _______

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-1: 38
Heat is generated uniformly in a long solid cylindrical rod (diameter$=10$ mm) at the rate of $4 \times 10^{7} W/m^{3}$. The thermal conductivity of the rod material is $25 W/m.K$. Under steady state conditions, the temperature difference between the centre and the surface of the rod is ______ $^{\circ} C$.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-1: 37
Two black surfaces, AB and BC, of lengths $5$ m and $6$ m, respectively, are oriented as shown. Both surfaces extend infinitely into the third dimension. Given that view factor $F_{12}=0.5, T_{1}=800 K, T_{2}=600 K, T_{\text{surrounding}}=300 K$ and Stefan- ... $2$ to the surrounding environment is _______ kW.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-1: 12
A heat pump absorbs $10$kW of heat from outside environment at $250$ K while absorbing $15$ kW of work. It delivers the heat to a room that must be kept warm at $300$ K. The Coefficient of Performance (COP) of the heat pump is ________.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-1: 11
The molar specific heat at constant volume of an ideal gas is equal to $2.5$ times the universal gas constant ($8.314$ J/mol.K). When the temperature increases by $100$K, the change in molar specific enthalpy is __________ J/mol.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2017 ME-1: 10
Saturated steam at $100^{\circ} C$ condenses on the outside of a tube. Cold fluid enters the tube at $20^{\circ} C$ and exits at $50^{\circ} C$. The value of the Log mean Temperature Difference (LMTD) is ________ $^{\circ}$ C.

Arjun asked in Heat Transfer Feb 27, 2017

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GATE2016-3-43
A cylindrical steel rod, $0.01 \: m$ in diameter and $0.2 \: m$ in length is first heated to $750^ \circ C$ and then immersed in a water bath at $100^ \circ C$. The heat transfer coefficient is $250 \: W/m^2-K$. The density, specific heat and thermal ... $k=43 \: W/m-K$, respectively. The time required for the rod to reach $300^ \circ C$ is ________ seconds.

Arjun asked in Heat Transfer Feb 24, 2017

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GATE2016-3-42
Two large parallel plates having a gap of $10 \: mm$ in between them are maintained at temperatures $T_1 = 1000 \: K$ and $T_2 = 400 \: K$. Given emissivity values, $\epsilon _1 = 0.5$, $\epsilon _2=0.25$ and Stefan-Boltzmann constant $\sigma =5.67 \times 10^{−8} \: W/m^2-K^4$, the heat transfer between the plates (in $kW/m^2$) is __________

Arjun asked in Heat Transfer Feb 24, 2017

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GATE2016-3-18
For a heat exchanger, $\triangle T_{\text{max}}$ is the maximum temperature difference and $\triangle T_{\text{min}}$ is the minimum temperature difference between the two fluids. LMTD is the log mean temperature difference. $C_{\text{min}}$ and $C_{\text{max}}$ are the minimum ... $C_{\text{max}} \triangle T_{\text{max}}$ $C_{\text{max}} \triangle T_{\text{min}}$

Arjun asked in Heat Transfer Feb 24, 2017

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GATE2016-3-17
The INCORRECT statement about the characteristics of critical point of a pure substance is that there is no constant temperature vaporization process it has point of inflection with zero slope the ice directly converts from solid phase to vapor phase saturated liquid and saturated vapor states are identical

Arjun asked in Heat Transfer Feb 24, 2017

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GATE2016-3-15
Steady one-dimensional heat conduction takes place across the faces $1$ and $3$ of a composite slab consisting of slabs $A$ and $B$ in perfect contact as shown in the figure, where $k_A$ , $k_B$ denote the respective thermal conductivities. Using the data as given in the figure, the interface temperature $T_2$ (in $^\circ C$) is __________

Arjun asked in Heat Transfer Feb 24, 2017

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