Heat transfer through a solid material due to temperature gradient is known as:
A. Conduction
B. Convection
C. Radiation
D. Advection
(Answer: A)
The primary mode of heat transfer in fluids is:
A. Convection
B. Conduction
C. Radiation
D. Diffusion
(Answer: A)
The heat transfer process that involves the emission and absorption of electromagnetic waves is:
A. Radiation
B. Convection
C. Conduction
D. Diffusion
(Answer: A)
In which type of heat transfer is a fluid moved to transfer heat from one place to another?
A. Convection
B. Conduction
C. Radiation
D. Conduction and Radiation
(Answer: A)
The thermal conductivity of a material is a measure of:
A. Its ability to conduct heat
B. Its ability to convect heat
C. Its ability to radiate heat
D. Its ability to insulate heat
(Answer: A)
In aerospace systems, which heat transfer method is primarily used for cooling spacecraft?
A. Convection
B. Conduction
C. Radiation
D. Convection and Radiation
(Answer: C)
The Nusselt number is a dimensionless parameter that characterizes:
A. Convective heat transfer
B. Conductive heat transfer
C. Radiative heat transfer
D. Thermal conductivity
(Answer: A)
The Fourier’s law of heat conduction states that the heat flux is proportional to:
A. The temperature gradient
B. The fluid velocity
C. The thermal radiation
D. The surface area
(Answer: A)
Which of the following is NOT a factor affecting heat transfer by convection?
A. Fluid velocity
B. Surface area
C. Fluid properties
D. Temperature difference
(Answer: B)
In a vacuum, the dominant mode of heat transfer is:
A. Radiation
B. Conduction
C. Convection
D. Conduction and Convection
(Answer: A)
The Stefan-Boltzmann law describes:
A. The power radiated per unit area of a black body
B. The rate of heat conduction through a material
C. The convective heat transfer coefficient
D. The heat exchange in a fluid
(Answer: A)
In a spacecraft, thermal control systems often use:
A. Radiators and heat pipes
B. Convection fans and heat sinks
C. Insulation and thermal blankets
D. Only conductive materials
(Answer: A)
The heat transfer coefficient in convection depends on:
A. Fluid velocity and properties
B. Temperature difference only
C. Material conductivity
D. Radiation properties
(Answer: A)
The Prandtl number is used in convection heat transfer to characterize:
A. The relative importance of momentum diffusivity to thermal diffusivity
B. The thermal conductivity of a material
C. The radiative heat transfer
D. The surface emissivity
(Answer: A)
In which scenario is conduction the primary mode of heat transfer?
A. In solid rocket motor casings
B. In the cooling of spacecraft using radiators
C. In heat exchangers involving fluids
D. In re-entry heat shields
(Answer: A)
Radiative heat transfer is most significant when:
A. The distance between objects is large
B. The objects are in contact
C. The fluid is moving rapidly
D. The temperature difference is small
(Answer: A)
The effectiveness of a heat shield is primarily based on:
A. Its ability to radiate heat away
B. Its thermal conductivity
C. Its convective heat transfer coefficient
D. Its thickness
(Answer: A)
In a convective heat transfer process, the boundary layer refers to:
A. The region where temperature changes significantly
B. The solid material conducting heat
C. The radiative heat flux
D. The fluid velocity profile
(Answer: A)
The term “thermal diffusivity” refers to:
A. The rate at which a material conducts heat relative to its capacity to store heat
B. The ability of a material to radiate heat
C. The convective heat transfer coefficient
D. The thickness of thermal insulation
(Answer: A)
Which type of heat transfer is typically used in spacecraft thermal control systems to maintain temperature stability?
A. Radiation
B. Conduction
C. Convection
D. Convection and Conduction
(Answer: A)
The concept of “view factor” in radiation heat transfer is used to describe:
A. The proportion of radiation leaving a surface that strikes another surface
B. The temperature gradient in a solid
C. The convective heat transfer coefficient
D. The emissivity of a material
(Answer: A)
The thermal resistance in a conduction scenario is calculated as:
A. Thickness divided by thermal conductivity
B. Heat flux divided by temperature difference
C. Convective heat transfer coefficient divided by surface area
D. Radiation heat flux divided by emissivity
(Answer: A)
In heat transfer through a composite material, the overall thermal resistance is determined by:
A. The sum of the resistances of each layer
B. The average of the thermal conductivities
C. The thickness of the composite material
D. The emissivity of each layer
(Answer: A)
The effect of fluid velocity on convective heat transfer is best described by:
A. Increasing fluid velocity enhances heat transfer due to reduced thermal boundary layer thickness
B. Decreasing fluid velocity increases the convective heat transfer coefficient
C. Fluid velocity has no impact on convective heat transfer
D. Higher velocity decreases the heat transfer rate
(Answer: A)
The emissivity of a material is:
A. A measure of its ability to emit thermal radiation
B. A measure of its thermal conductivity
C. The rate of convective heat transfer
D. The thickness of the insulating material
(Answer: A)
The concept of “heat pipe” is used to:
A. Efficiently transfer heat using phase change in a closed system
B. Increase the surface area for convective heat transfer
C. Enhance radiative heat transfer
D. Decrease conductive heat transfer
(Answer: A)
The thermal boundary layer in convection is characterized by:
A. A region where the temperature gradient is significant
B. The convective heat transfer coefficient
C. The emissivity of the fluid
D. The thickness of the solid material
(Answer: A)
In aerospace applications, thermal insulation is used to:
A. Minimize heat transfer to sensitive components
B. Enhance convective heat transfer
C. Improve radiative heat exchange
D. Facilitate heat conduction
(Answer: A)
The term “blackbody” in radiation heat transfer refers to:
A. An idealized surface that absorbs and emits all incident radiation perfectly
B. A material with low thermal conductivity
C. A surface that only conducts heat
D. A material that reflects all incident radiation
(Answer: A)
The Biot number is a dimensionless number used to characterize:
A. The ratio of conductive heat resistance within a body to convective heat resistance at its surface
B. The effectiveness of radiative heat transfer
C. The convective heat transfer coefficient
D. The thermal conductivity of a material
(Answer: A)
In a thermal system, the term “heat flux” refers to:
A. The rate of heat transfer per unit area
B. The total heat transferred through a system
C. The temperature difference across a material
D. The thickness of thermal insulation
(Answer: A)
The purpose of a heat exchanger in aerospace applications is to:
A. Transfer heat between fluids or from fluids to solids efficiently
B. Conduct heat through solid materials
C. Radiate heat away from sensitive components
D. Enhance thermal insulation
(Answer: A)
In re-entry vehicle design, heat shields are primarily used to:
A. Protect against intense thermal radiation during atmospheric entry
B. Enhance convective heat transfer
C. Increase thermal conductivity
D. Reduce radiative heat exchange
(Answer: A)
The Reynolds number is used in convection heat transfer to characterize:
A. The flow regime of the fluid
B. The thermal conductivity of a material
C. The emissivity of a surface
D. The rate of radiative heat transfer
(Answer: A)
The term “thermal conductivity” measures:
A. How well a material conducts heat
B. How well a material insulates against heat
C. The rate of convective heat transfer
D. The emissivity of a surface
(Answer: A)
In aerospace thermal management, radiative cooling is used to:
A. Dissipate heat into space effectively
B. Transfer heat between fluids
C. Conduct heat through structural components
D. Increase convective heat transfer
(Answer: A)
The concept of “thermal capacitance” in a material is:
A. Its ability to store heat
B. Its ability to conduct heat
C. Its rate of radiative heat emission
D. Its convective heat transfer coefficient
(Answer: A)
The heat transfer coefficient in convection is influenced by:
A. Fluid velocity, viscosity, and thermal conductivity
B. The emissivity of the surface
C. The thickness of the material
D. The surface area of the material
(Answer: A)
In a spacecraft, thermal control systems use thermal blankets primarily for:
A. Insulating sensitive components from extreme temperatures
B. Enhancing convective heat transfer
C. Increasing radiative heat transfer
D. Conducting heat away from sensitive areas
(Answer: A)
The term “radiative heat transfer” refers to:
A. Heat transfer through electromagnetic waves
B. Heat transfer through fluid motion
C. Heat transfer through direct contact
D. Heat transfer through material conduction
(Answer: A)
The term “thermal resistance” is used to describe:
A. The opposition to heat transfer through a material
B. The ability of a material to store heat
C. The convective heat transfer rate
D. The rate of radiative heat emission
(Answer: A)
The emissivity of a perfect blackbody is:
A. 1
B. 0
C. 0.5
D. 2
(Answer: A)
The primary purpose of a heat pipe in aerospace applications is:
A. To transfer heat efficiently using phase change mechanisms
B. To increase thermal resistance
C. To enhance convective heat transfer
D. To radiate heat away from sensitive components
(Answer: A)
In a heat exchanger, the effectiveness of heat transfer is influenced by:
A. The design and flow arrangement of the exchanger
B. The emissivity of the heat exchanger surface
C. The thickness of the heat shield
D. The thermal conductivity of the insulating material
(Answer: A)
The term “thermal boundary layer” in convection refers to:
A. The layer of fluid near a solid surface where temperature gradients are significant
B. The layer of material conducting heat
C. The layer of radiation emitted from a surface
D. The thickness of thermal insulation
(Answer: A)
The main objective of thermal insulation in aerospace systems is to:
A. Prevent heat transfer to or from sensitive components
B. Enhance the convective heat transfer coefficient
C. Increase thermal radiation to the surroundings
D. Decrease thermal conductivity
(Answer: A)
In convective heat transfer, the Rayleigh number is used to characterize:
A. The flow regime of natural convection
B. The rate of heat conduction
C. The emissivity of a surface
D. The effectiveness of radiative cooling
(Answer: A)
The role of a thermal blanket in a spacecraft is primarily to:
A. Protect the spacecraft from extreme temperatures by reducing heat transfer
B. Enhance convective heat transfer within the spacecraft
C. Increase the emissivity of the spacecraft surface
D. Conduct heat efficiently to external radiators
(Answer: A)
The term “heat sink” refers to:
A. A device or material that absorbs and dissipates heat from a system
B. A material that conducts heat to other parts of a system
C. A method of radiative heat transfer
D. A method of convective heat transfer
(Answer: A)
In the context of heat shields, the primary design consideration is to:
A. Minimize the heat transfer into the spacecraft during atmospheric re-entry
B. Maximize convective heat transfer
C. Enhance radiative heat transfer away from the spacecraft
D. Increase the thermal conductivity of the shield material
(Answer: A)