What happens during the phase change of condensation?
A Solid turns to gas
B Solid turns to liquid
C Liquid turns to gas
D Gas turns to liquid
During condensation, a gas turns into a liquid as it loses heat. This process releases latent heat, which is absorbed by the surrounding environment. It occurs when the gas cools down and its molecules slow down, forming a liquid.
What is the primary factor affecting the rate of transient heat transfer?
A Time
B Material thickness
C Thermal resistance
D Fluid viscosity
Transient heat transfer refers to the time-dependent process where the temperature of a material changes. The rate of transient heat transfer is primarily affected by time, as heat spreads through a material over time until thermal equilibrium is reached.
Which of the following is most commonly associated with phase change heat transfer?
A Specific heat
B Latent heat
C Thermal conductivity
D Heat flux
Phase change heat transfer, such as during boiling or condensation, involves the absorption or release of latent heat. This energy is required to change the state of a substance without changing its temperature.
What is the effect of increasing the temperature of a boiling liquid on heat transfer?
A Reduces efficiency
B No effect
C Increases heat transfer
D Decreases heat transfer
Increasing the temperature of a boiling liquid increases the rate of heat transfer because a higher temperature difference between the liquid and the heating surface promotes faster heat transfer and more efficient boiling.
Which of the following is an example of transient heat transfer?
A Cooling of a hot object
B Boiling of water
C Steady-state conduction
D Heat loss through insulation
Transient heat transfer occurs when the temperature of an object changes over time, such as when a hot object cools down. The heat transfer process continues until the object reaches thermal equilibrium with its surroundings.
In condensation, what happens to the latent heat of vaporization?
A It is absorbed by the material
B It is released into the surroundings
C It increases the temperature
D It decreases the temperature
During condensation, the latent heat of vaporization is released as the gas turns into a liquid. This heat is transferred to the surroundings, which is why condensation typically occurs when the surrounding temperature is cooler.
What occurs during the phase change from liquid to vapor?
A Heat is released
B No heat change
C Temperature decreases
D Heat is absorbed
During the phase change from liquid to vapor (boiling or evaporation), heat is absorbed. This energy is used to break the intermolecular bonds in the liquid, allowing it to change into vapor without a change in temperature.
Which of the following processes involves heat transfer due to the change in temperature over time?
A Condensation
B Latent heat
C Transient heat transfer
D Steady-state heat transfer
Transient heat transfer involves the time-dependent changes in temperature. This type of heat transfer occurs when an object or system is not in thermal equilibrium, and temperature variations change with time until equilibrium is achieved.
What happens to the temperature of a substance during a phase change?
A It remains constant
B It fluctuates
C It increases
D It decreases
During a phase change, such as melting, boiling, or condensation, the temperature of the substance remains constant. The energy supplied or removed is used to change the phase, not to increase or decrease the temperature.
What is the role of thermal conductivity during phase change heat transfer?
A Increases heat flow
B Has no effect
C Affects heat transfer rate
D Decreases phase change time
Thermal conductivity affects the rate at which heat is transferred during phase changes. Materials with high thermal conductivity transfer heat more efficiently, speeding up the phase change process and improving heat transfer.
Which heat transfer process occurs during evaporation?
A Conduction
B Convection
C Radiation
D Latent heat transfer
Evaporation involves latent heat transfer, where heat is absorbed by the liquid to convert it into vapor. This energy is absorbed without a change in temperature until all the liquid has turned into vapor.
What is the effect of a high thermal resistance on transient heat transfer?
A Increases temperature gradient
B Decreases heat transfer
C No effect
D Increases heat transfer
High thermal resistance impedes heat flow, making it more difficult for heat to transfer through a material. In transient heat transfer, materials with high resistance slow down the rate at which heat spreads over time.
How does the temperature gradient affect the rate of transient heat transfer?
A No effect
B Decreases rate
C Increases rate
D Affects phase change
A higher temperature gradient drives heat transfer. In transient heat transfer, a larger temperature difference between the system and its surroundings results in a faster rate of heat transfer until thermal equilibrium is reached.
Which of the following occurs during the cooling process of a hot object?
A Transient heat transfer
B Evaporation
C Phase change
D Condensation
During the cooling process of a hot object, transient heat transfer occurs as the object loses heat over time. This process continues until the object reaches the ambient temperature of its surroundings.
What is the main energy source involved in phase change heat transfer?
A Sensible heat
B Thermal radiation
C Latent heat
D Convection
Phase change heat transfer involves latent heat, which is the energy required for a substance to change its phase (e.g., from liquid to vapor) without changing its temperature. This energy is absorbed or released during the phase change.