Heat Transfer Principles and Equations

<p>Thermal resistance of the wall (D)</p> Signup and view all the answers

<p>Thermal conductivity of the wall material (A)</p> Signup and view all the answers

<p>$U = rac{1}{R_t} = rac{1}{rac{1}{h_h} + rac{x_1}{k_1} + rac{x_2}{k_2} + rac{1}{h_c}}$ (C)</p> Signup and view all the answers

<p>$Q = rac{A \Delta T}{R_t}$ (B)</p> Signup and view all the answers

<p>$R = rac{\ln(r_2/r_1)}{2\pi kL}$ (C)</p> Signup and view all the answers

<p>$Q = rac{t_2 - t_1}{R}$ (A)</p> Signup and view all the answers

<p>$R_T = rac{x_1}{k_1} + rac{x_2}{k_2} + rac{x_3}{k_3}$ (B)</p> Signup and view all the answers

<p>$Q = rac{A(t_1 - t_4)}{rac{x_1}{k_1} + rac{x_2}{k_2} + rac{x_3}{k_3} + rac{1}{h_o} + rac{1}{h_i}}$ (D)</p> Signup and view all the answers

<p>Heat transfer rate through the third layer. (A)</p> Signup and view all the answers

<p>$Q = h_o A (t_o - t_1)$ (C)</p> Signup and view all the answers

<p>Thermal conductivity of the second layer (B)</p> Signup and view all the answers

<p>Q1 = (t2 - t1) / [ln(r2/r1)] * 2πk1L (A)</p> Signup and view all the answers

<p>The thermal conductivity of the nth layer (D)</p> Signup and view all the answers

<p>Q = Q1 + Q2 (C)</p> Signup and view all the answers

<p>It indicates the thermal resistance of the first layer (A)</p> Signup and view all the answers

<p>Q = hiAi(ti -t1) (D)</p> Signup and view all the answers

<p>mC/W (B)</p> Signup and view all the answers

<p>$U_i = rac{Q A_i}{\Delta t}$ (B)</p> Signup and view all the answers

<p>The natural logarithm of the ratio of the outer radius to the inner radius (A)</p> Signup and view all the answers

<p>Refrigerator (B)</p> Signup and view all the answers

<p>Overall conductance of the heat exchanger (C)</p> Signup and view all the answers

<p>Counterflow (B)</p> Signup and view all the answers

<p>To calculate the average temperature difference between the hot and cold fluids in a heat exchanger. (A)</p> Signup and view all the answers

<p>Counterflow (B)</p> Signup and view all the answers

<p>The maximum temperature difference between the hot and cold fluids. (C)</p> Signup and view all the answers

<p>They flow at an angle to each other. (A)</p> Signup and view all the answers

<p>The temperature of the cold fluid remains constant throughout the exchange process. (B)</p> Signup and view all the answers

<p>The temperature difference between the hot and cold fluids remains constant throughout the exchange process. (C)</p> Signup and view all the answers

<p>Constant temperature heat exchanger. (B)</p> Signup and view all the answers

<p>The temperature of the hot fluid decreases as the cold fluid gains heat from it. (A)</p> Signup and view all the answers

<p>A hot fluid flows through a device and its temperature decreases as it gives heat to a cold fluid, both of which are moving. (D)</p> Signup and view all the answers

<p>The heat transferred by radiation between two surfaces (C)</p> Signup and view all the answers

<p>Absorbs all radiation without reflection (D)</p> Signup and view all the answers

<p>Transmissivity (B)</p> Signup and view all the answers

<p>Density of the material (B)</p> Signup and view all the answers

<p>The balance of energy absorbed, reflected, and transmitted (A)</p> Signup and view all the answers

<p>It depends on the material properties and absolute temperature. (B)</p> Signup and view all the answers

<p>Reynolds Number (D)</p> Signup and view all the answers

<p>The ratio of total emissive power to absorptivity is a constant at all temperatures. (C)</p> Signup and view all the answers

<p>Energy emitted is proportional to the fourth power of the absolute temperature. (D)</p> Signup and view all the answers

<p>It only occurs in solids. (A)</p> Signup and view all the answers

<p>Dynamic viscosity multiplied by specific heat to thermal conductivity (C)</p> Signup and view all the answers

<p>Grashof Number (NGr) (A)</p> Signup and view all the answers

<p>h (B)</p> Signup and view all the answers

<p>To standardize and simplify heat transfer comparisons (D)</p> Signup and view all the answers

<p>NGr = (D³ρ²βΔT) / µ² (B)</p> Signup and view all the answers

The movement of heat from one body to another by conduction, convection, or radiation.

Heat transfer through molecular interaction in bodies in contact.

Heat transfer due to the mixing and motion of particles in a substance.

Calculates heat transfer through a plane wall: Q = (kA(t1 - t2))/x.

Multiple layers' heat transfer represented by Q = A Δt / R.

$h_h$ is the surface film conductance on the hot side, expressed in W/m²°C.

$h_c$ is the surface film conductance on the cold side, expressed in W/m²°C.

$U$ is the overall heat transfer coefficient, calculated using the formula $U = rac{1}{R_t}$.

$Q = U A \Delta T$ quantifies heat transfer in terms of overall conductance, area, and temperature difference.

$Q = \frac{\Delta T}{R_t}$ calculates heat loss using temperature difference and resistance.

Used for calculating heat transfer rate across layers: $Q = \frac{k A (t_{top} - t_{bottom})}{x}$.

Total thermal resistance for a composite wall: $R_T = \frac{x_1}{k_1} + \frac{x_2}{k_2} + \frac{x_3}{k_3}$.

Total heat transfer illustrated as $Q = \frac{A(t_{initial} - t_{final})}{R_T}$.

Heat transfer equation: $Q = h_o A (t_o - t_1)$.

A device that transfers heat between substances.

Constant heat flow through materials without change over time.

A measure of a material's ability to resist heat flow.

Q = U A Δt defines heat transfer based on area and temperature difference.

A pipe made up of multiple layers, each with different thermal properties.

Heat transfer through layer 1 of a composite pipe.

Heat transfer through layer 2 of a composite pipe.

The sum of heat transfers through all layers in a composite pipe (Q = Q1 + Q2).

Thermal resistance for layers, calculated using radii and conductivity.

Devices where a fluid at constant temperature transfers heat to a cooler fluid, which heats up.

Devices where a warmer fluid loses heat to a cooler fluid, causing the warmer fluid to cool down.

An example of a constant temperature heat exchanger where steam cools down and condenses.

An example of a variable temperature heat exchanger where water is heated by steam, increasing its temperature.

Graphs showing temperature changes of fluids; hot fluid slopes down, cold fluid is horizontal for variable exchangers.

Heat transfer through electromagnetic waves.

Describes radiation heat transfer using temperature to the fourth power.

An ideal body that absorbs all radiation without reflection.

The fraction of energy absorbed by a surface, related to reflectivity and transmissivity.

Ratio of dynamic viscosity times specific heat to thermal conductivity.

Ratio of total heat transfer to conductive heat transfer in convection.

Ratio of buoyancy forces to viscous forces in free convection.

A measure of a fluid's resistance to flow and deformation.

A measure of a material's ability to conduct heat.

A type of heat exchanger where fluids flow in the same direction and both change temperature.

Heat exchangers where fluids flow in opposite directions, maximizing efficiency.

In this type, one fluid flows at an angle to the other, such as in tube banks.

A formula used to find the average temperature difference between two fluids in a heat exchanger.

The difference in temperature between hot and cold fluids in a heat exchanger, influencing heat transfer efficiency.

Describes how substances emit radiation based on temperature and material properties.

In thermal equilibrium, total emissive power to absorptivity ratio remains constant.

Dimensionless number indicating flow regime influenced by viscosity, velocity, and length.

Dimensionless number that relates convective and conductive heat transfer.