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Thermal Actuators and Heat Transfer Modes Quiz

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Thermal Actuators and Heat Transfer Modes Quiz

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Questions and Answers

Which of the following modes of heat transfer does not require a material medium?

Conduction

Convection

Thermal energy movement

Radiation (correct)

What is the working equation for conduction?

$Q = dR_{th} \frac{T_1 - T_2}{\kappa A}$ (correct)

$Q = \frac{T_1 - T_2}{dR_{th}}$

$Q = \frac{dR_{th}}{T_1 - T_2}$

$Q = \frac{T_1 - T_2}{R_{th}}$

What material has the highest thermal conductivity?

Copper (correct)

Styrofoam

Silicon

None of the above

What is the qualitative behavior of a hot arm actuator based on the simplified lumped element model?

Energy conversion from thermal to mechanical mode Signup and view all the answers

What is the equation for convection heat transfer between a moving fluid and a surface at temperature T1 and T2?

$Q = hA(T1 - T2)$ Signup and view all the answers

For radiation, what is the equation for heat transfer from a perfect blackbody surface area at Ts to the surroundings at temperature T?

$Q = \epsilon\sigma A(T^4 - T_s^4)$ Signup and view all the answers

What is the equation for heat transfer due to convection from a surface at temperature Th to the surroundings at temperature T∞?

$Q_{conv} = hA(Th - T_\infty)$ Signup and view all the answers

What is the formula for the voltage drop across the hot arm (eh) in terms of input voltage (e), resistivity of the actuator material (ρ), and its geometry?

$eh = \frac{e \rho}{L / Ah + \rho (L / Ac)}$ Signup and view all the answers

What is the equation for thermal strain (ε) in the hot arm of a thermal actuator when heated from temperature T∞ to Th?

$\epsilon_h = \alpha T(Th - T_\infty)$ Signup and view all the answers

What is the additional piece of strain (ε extra) experienced by the hot arm due to being hooked to the cold arm?

$\epsilon_h = \alpha T(Th - T_\infty) + \epsilon_extra$ Signup and view all the answers

What is the formula for finding the temperature Th of the hot arm in terms of input voltage (e), resistivity of the actuator material (ρ), its geometry, and heat transfer coefficient (h)?

$Th = \frac{2hpAh}{e} + T_\infty$ Signup and view all the answers

In what mode does a small object completely surrounded by a large surface experience heat transfer?

Radiation Signup and view all the answers

What phenomenon induces bending moment in the cold arm of a thermal actuator?

Differential thermal expansion Signup and view all the answers

What physical concept does the equation $Q = hA(T1 - T2)$ represent?

Fourier's law of heat conduction Signup and view all the answers