Thermodynamics - Finals

What is a heat engine?

• A device that converts thermal energy into mechanical work.

• A device that converts mechanical work into thermal energy.

•  A device that measures the temperature of a system.

• A device that controls the flow of heat in a system.

Which of the following statements best describes the operation of a heat engine?

• Heat is absorbed from a cold reservoir and converted entirely into mechanical work.

• Heat is absorbed from a hot reservoir and converted entirely into thermal energy.

• Heat is absorbed from a hot reservoir, part of it is converted into mechanical work, and the rest is rejected to a cold reservoir.

• Heat is absorbed from a cold reservoir and rejected to a hot reservoir without any work output.

What is a heat pump?

• A device that converts mechanical work into thermal energy.

• A device that measures the temperature of a system.

• A device that transfers heat from a cold reservoir to a hot reservoir by applying work.

• A device that transfers heat from a hot reservoir to a cold reservoir.

Which of the following best describes the operation of a heat pump?

• Heat is absorbed from a hot reservoir and rejected to a cold reservoir without any work input.

• Heat is absorbed from a cold reservoir and rejected to a hot reservoir without any work input.

• Mechanical work is input to transfer heat from a cold reservoir to a hot reservoir.

• A.     Mechanical work is input to transfer heat from a hot reservoir to a cold reservoir.

In a heat pump, what is the purpose of the refrigerant?

• To measure the temperature of the system.

• To provide mechanical work for heat transfer

• To absorb heat from the cold reservoir.

• To facilitate the transfer of heat between the hot and cold reservoirs

What is the coefficient of performance (COP) of a heat pump?

• The ratio of mechanical work input to heat transfer

• The ratio of heat transferred to the input work.

• The ratio of heat transferred to the temperature difference between the hot and cold reservoirs.

• The ratio of the temperature difference between the hot and cold reservoirs to the heat transferred

In the Brayton cycle, what is the working fluid typically used?

• Water.

• Steam.

• Air.

• Refrigerant.

Which of the following best describes the concept of entropy generation?

• The process of converting thermal energy into mechanical work.

• The increase in disorder or randomness within a system.

• The production of entropy due to irreversible processes.

• The transfer of heat from a high-temperature body to a low-temperature body.

What is the function of the compressor in the vapor compression refrigeration cycle?

• To heat the refrigerant.

• To cool the refrigerant.

• To increase the pressure of the refrigerant.

• To decrease the pressure of the refrigerant.

At the triple point of a pure substance, which of the following occurs?

• The substance transitions directly from solid to vapor.

• The substance transitions directly from liquid to vapor.

• The substance coexists in equilibrium as solid, liquid, and vapor.

• The substance reaches its highest temperature.