310 Final Exam.docx

What is the main function of a heat pump in summer?

Pumps heat from inside to outside.

What is the main function of a heat pump in winter?

Pumps heat from outside to inside, extracting heat from the air.

What is the formula for NET work in a heat pump?

W_NET = Q_h - Q_c.

What does the compressor do in a heat pump system?

Compresses refrigerant to raise its temperature and pressure.

What is the purpose of a reversing valve in a heat pump?

Directs refrigerant flow to indoor or outdoor unit depending on heating or cooling mode.

What occurs during the evaporation stage of the refrigeration cycle?

Refrigerant absorbs heat and turns into gas.

What is one advantage of a water-cooled chiller?

Greater efficiency and temperature stability.

What is a disadvantage of air-cooled chillers?

Lower efficiency and affected by ambient air conditions.

What occurs when resistive heat is generated?

An electric current passes through a conductor and encounters resistance, converting electrical energy into heat.

What are the two main types of compressors?

Positive displacement and dynamic compressors.

What is unique about a hydrogen-oxygen fuel cell?

Converts chemical energy from hydrogen and oxygen into electricity with water as the only byproduct.

What does Faraday’s Law state?

Voltage induced in a loop is directly proportional to the change in time of the magnetic flux.

What is the key component of a generator that moves to induce current?

Rotor.

What is one major difference between AC and DC motors?

AC motors use alternating current, while DC motors use direct current.

What is the principle behind the working of turbines?

Convert kinetic energy from moving fluid into mechanical energy.

What is the main ecological advantage of using fuel cells?

They produce no pollution, only water as a byproduct.

What is E_p in photovoltaic cells related to?

Photon energy, which is calculated using E_p = hc/λ.

What role do expansion valves play in heat pump systems?

Control refrigerant flow and reduce its temperature and pressure.

What is the efficiency of condensing boilers compared to older models?

Condensing boilers can achieve efficiencies of 90% or higher, while older models may be as low as 70%.

What is the Betz limit in wind turbine technology?

16/27, which indicates the theoretical maximum power that can be extracted from wind.