Closed Systems and Heat Transfer: Master Heat Transfer Mechanisms

Question 1

Which material has the highest thermal conductivity?

Accepted Answer

Copper

Answer

Aluminum

Answer

Stainless steel

Answer

Rubber

Question 2

A blackbody is characterized by its ability to:

Accepted Answer

Absorb and emit all incident radiation

Answer

Reflect all incident radiation

Answer

Transmit all incident radiation

Answer

Have a low specific heat capacity

Question 3

In a counterflow heat exchanger, the fluid streams enter the exchanger at opposite ends and flow in what direction relative to each other?

Accepted Answer

Opposite directions

Answer

The same direction

Answer

Perpendicular directions

Answer

Parallel directions

Question 4

The Nusselt number is a dimensionless parameter used to quantify:

Accepted Answer

Convective heat transfer

Answer

Conduction heat transfer

Answer

Radiation heat transfer

Answer

Phase change heat transfer

Question 5

Which of the following is not a recognized mode of heat transfer?

Accepted Answer

Friction

Answer

Conduction

Answer

Convection

Answer

Radiation

Question 6

According to the first law of thermodynamics, for a closed system undergoing a process, the change in its internal energy (dU) is:

Accepted Answer

Equal to the difference between the heat transfer (dQ) into the system and the work done (dW) by the system

Answer

Equal to the sum of the heat transfer (dQ) into the system and the work done (dW) by the system

Answer

Independent of heat transfer and work

Answer

Always zero

Question 7

Radiation heat transfer is attributed to:

Accepted Answer

Electromagnetic waves

Answer

Collisions between particles

Answer

Movement of fluid

Answer

Temperature variations

Question 8

The efficiency (η) of a heat engine is commonly defined as the ratio of:

Accepted Answer

Work output to heat input

Answer

Heat input to work output

Answer

Change in internal energy to heat input

Answer

Change in internal energy to heat output

Question 9

Which of the following is NOT a mode of heat transfer in engineering systems?

Accepted Answer

Evaporation

Answer

Conduction

Answer

Convection

Answer

Radiation

Question 10

In conduction heat transfer, heat flows from higher to lower temperature regions primarily through:

Accepted Answer

Direct contact

Answer

Mass motion

Answer

Electromagnetic waves

Answer

Pressure gradients

Question 11

Radiation heat transfer occurs through the emission and absorption of:

Accepted Answer

Electromagnetic waves

Answer

Fluid motion

Answer

Direct contact

Answer

Pressure gradients

Question 12

In a closed system undergoing an adiabatic process, the heat transfer is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Equal to the work done

Question 13

Which of the following is a defining characteristic of closed systems in thermodynamics?

Accepted Answer

No mass can enter or leave the system

Answer

The system is always in thermal equilibrium

Answer

The system is adiabatic

Answer

The system is isothermal

Question 14

Which dimensionless group is commonly used to characterize forced convection in fluid flow?

Accepted Answer

Reynolds number

Answer

Nusselt number

Answer

Prandtl number

Answer

Grashof number

Question 15

Define the heat transfer mechanism that occurs due to differences in temperature and density.

Accepted Answer

Convection

Answer

Conduction

Answer

Radiation

Answer

Evaporation

Question 16

In a vacuum, which heat transfer mechanism is the most dominant?

Accepted Answer

Radiation

Answer

Conduction

Answer

Convection

Answer

Diffusion

Question 17

According to the First Law of Thermodynamics, which statement accurately describes a closed system?

Accepted Answer

Energy transfer (in/out) is possible, but mass transfer is not.

Answer

Energy transfer out is possible, but not in.

Answer

Mass transfer (in/out) is possible, but energy transfer is not.

Question 18

What is the SI unit for thermal conductivity?

Accepted Answer

Watts per meter Kelvin

Answer

Degrees Celsius per meter

Answer

Calories per gram

Answer

Joules per second

Question 19

What is the primary purpose of the Stefan-Boltzmann constant?

Accepted Answer

Calculating radiative heat transfer

Answer

Calculating convective heat transfer

Answer

Calculating the speed of sound

Answer

Calculating conductive heat transfer

Question 20

Which of the following is NOT a recognized mode of heat transfer?

Accepted Answer

Advection

Answer

Convection

Answer

Radiation

Answer

Conduction

Question 21

What is the main purpose of thermal insulation?

Accepted Answer

To minimize heat flow

Answer

To increase heat flow

Answer

To store thermal energy

Answer

To generate thermal energy

Question 22

Which material is considered a good conductor of heat?

Accepted Answer

Copper

Answer

Air

Answer

Rubber

Answer

Wood