Recent questions in Heat Transfer

A body is placed inside a perfectly black enclosure and is allowed to reach thermal equilibrium. According to the Kirchhoff's identity, which one of the following is equa...

Which one of the following ratios does Grashof number represent?buoyancy force to inertia forcebuoyancy force to viscous forceviscous force to capillary forceviscous forc...

In a double pipe cocurrent heat exchanger, operating at steady state, oil (specific heat capacity $=2100 \mathrm{~J} \mathrm{~kg}^{-1}{ }^{\circ} \mathrm{C}^{-1}$ ) enter...

A pipe with outer diameter of $0.02 \text{ m},$ carries hot water. The temperature at the outer surface of the pipe is $70^{\circ} \mathrm{C}$. This pipe is covered with ...

​​​​Which of the following statements regarding multiple effect evaporators is/are TRUE?The pressure of the effect with fresh steam is the lowest for both forward feed an...

​​​​A hot plate is placed in contact with a cold plate of a different thermal conductivity as shown in the figure. The initial temperature (at time $t=0$ ) of the hot pla...

An adiabatic pump of efficiency $40 \%$ is used to increase the water pressure from $200 \: \mathrm{kPa}$ to $600 \: \mathrm{kPa}$ . The flow rate of water is $600 \mathr...

Water flowing at $70 \mathrm{~kg} / \mathrm{min}$ is heated from $25^{\circ} \mathrm{C}$ to $65^{\circ} \mathrm{C}$ in a counter-flow double pipe heat exchanger using hot...

Consider laminar flow of water over a wide flat plate maintained at a uniform temperature of $50^{\circ} \: \mathrm{C}$ as shown in the figure. The freestream velocity an...

An electrical wire of $2 \: \mathrm{mm}$ diameter and $5 \: \mathrm{m}$ length is insulated with a plastic layer of thickness $2 \: m\mathrm{m }$ and thermal conductivity...

If the Prandtl number $\operatorname{Pr}=0.01$, which of the following statements is/are correct?The momentum diffusivity is much larger than the thermal diffusivity.The ...

The opposite faces of a metal slab of thickness $5 \mathrm{~cm}$ and thermal conductivity $400 \mathrm{~W} \mathrm{~m}^{-1}{ }^{\circ} \mathrm{C}^{-1}$ are maintained at ...

​​​​​​The temperatures of two large parallel plates of equal emissivity are $900 \mathrm{~K}$ and $300 \mathrm{~K}$. A reflection radiation shield of low emissivity and n...

​​​​​Hot oil at $110{ }^{\circ} \mathrm{C}$ heats water from $30^{\circ} \mathrm{C}$ to $70{ }^{\circ} \mathrm{C}$ in a counter-current double-pipe heat exchanger. The fl...

​​​​​A solid slab of thickness $H_{1}$ is initially at a uniform temperature $T_{0}$. At time $t=0$, the temperature of the top surface at $y=H_{1}$ is increased to $T_{1...

Heat is available at a rate of $2 \mathrm{~kW}$ from a thermal reservoir at $400 \mathrm{~K}$. A two-stage process harnesses this heat to produce power. Stages $1$ and $2...

Match the quantities in Group $1$ with their units in Group $2$ listed in the table below.$$\begin{array}{|l|l|} \hline \qquad \qquad \qquad \textbf{Group 1} & \textbf{Gr...

A slab of thickness $L$, as shown in the figure below, has cross-sectional area $A$ and constant thermal conductivity $k. T_1$ and $T_2$ are the temperatures at $x=0$ and...

An isothermal jacketed continous stirred tank reactor (CSTR) operating at $150^{\circ} \mathrm{C}$ is shown in the figure below. The cold feed entering the system at $30^...

Given that $E$ (in W. $\mathrm{m}^{-2}$ ) is the total hemispherical emissive power of a surface maintained at a certain temperature, which of the following statements is...

Which of the following statements is/are $\text{CORRECT}$? Bond number includes surface tension. Jakob number includes latent heat. Prandtl number includes liquid-vapor d...

A fluid is flowing steadily under laminar conditions over a thin rectangular plate at temperature $T_s$ as shown in the figure below. The velocity and temperature of the ...

A perfectly insulated, concentric tube countercurrent heat exchanger is used to cool lubricating oil using water as a coolant (see figure below). Oil enters the outer ann...

A perfectly insulated double pipe heat exchanger is operating at steady state. Saturated steam enters the inner pipe at $100^{\circ}C$ and leaves as saturated water at $1...

Consider a bare long copper wire of $1$ $\text{mm}$ diameter. Its surface temperature is $T_{s}$ and the ambient temperature is $T_{a}\:(T_{s} T_{a})$. The wire is to be...

Two large parallel planar walls are maintained at $1000\:K$ and $500\:K$. Parallel radiation shields are to be installed between the two walls. Assume that the emissiviti...

Saturated steam condenses on a vertical plate maintained at a constant wall temperature. If $x$ is the vertical distance from the top edge of the plate, then the local he...

A cylindrical fin of diameter $24$ $\text{mm}$ is attached horizontally to a vertical planar wall. The heat transfer rate from the tin to the surrounding ar is $60\%$ of ...

A single-effect evaporator with a heat transfer area of $70\:m^{2}$ concentrates a salt solution using steam. The salt solution feed rate and temperature are $10000\:kg\:...

Heat transfer coefficient for a vapor condensing as a film on a vertical surface is given byDittus-Boelter equationNusselt theoryChilton-Colburn analogySieder-Tate equati...

In a double-pipe heat exchanger of $10 \: m$ length, a hot fluid flows in the annulus and a cold fluid flows in the inner pipe. The temperature profiles of the hot $(T_h)...

For a shell-and-tube heat exchanger, the clean overall heat transfer coefficient is calculated as $\text{250 W m$^{-2}$ K}^{-1}$ for a specific process condition. It is e...

A straight fin of uniform circular cross section and adiabatic tip has an aspect ratio (length/diameter) of $4$. If the Biot number (based on the radius of the fin as the...

A double-effect evaporator is used to concentrate a solution. Steam is sent to the first effect at $110\:^{\circ} C$ and the boiling point of the solution in the second e...

Consider a solid slab of thickness $2L$ and uniform cross section $A$. The volumetric rate of heat generation within the slab is $\dot{g} \: (W \: m^{-3})$. The slab lose...

A hollow cylinder of equal length and inner diameter (i.e., $L=D$) is sealed at both ends with flat plate, as shown in the figure. Its inner surfaces, $A_1$, $A_2$, and $...

A fluid is heated from $40^{\circ}C$ to $60^{\circ} C$ in a countercurrent, double pipe heat exchanger. Hot fluid enters at $100^{\circ}C$ and exits at $70^{\circ}C$. The...

Consider an infinitely long rectangular fin exposed to a surrounding fluid at a constant temperature $T_a=27^{\circ}C$.The steady state one dimensional energy balance on ...