Thermodynamics: First Law Applied to Flow Processes
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Questions and Answers

What is the fundamental principle that all processes in the universe comply with?

  • First law of thermodynamics
  • Second law of thermodynamics
  • Both first and second laws of thermodynamics (correct)
  • None of the above

    • What is the maximum amount of heat that an electric heater can produce if it consumes 1 kW of electricity?

  • Exactly 1 kW (correct)
  • More than 1 kW
  • Depends on the efficiency of the heater
  • Less than 1 kW

    • What is the type of flow where the rate of fluid flow through a machine or apparatus is constant?

  • Unsteady flow
  • Steady flow (correct)
  • Turbulent flow
  • Laminar flow

    • What is the purpose of the Steady Flow Energy Equation (SFEE)?

    <p>To relate the energy changes between the inlet and outlet of a control volume</p> Signup and view all the answers

    What is the term for the energy transferred due to the movement of a fluid in and out of a control volume?

    <p>Flow work</p> Signup and view all the answers

    What is the equation that represents the Steady Flow Energy Equation (SFEE)?

    <p>All of the above</p> Signup and view all the answers

    What is the assumption made in the analysis of the Steady Flow Energy Equation (SFEE)?

    <p>All of the above</p> Signup and view all the answers

    What is the term for the energy per unit mass of a fluid?

    <p>Specific enthalpy</p> Signup and view all the answers

    What is the formula for the specific kinetic energy of a fluid?

    <p>V²/2</p> Signup and view all the answers

    What is the force that moves the mass in and out of a control volume?

    <p>Piston force</p> Signup and view all the answers

    What does the First Law of Thermodynamics state about energy?

    <p>Energy can be converted from one form to another.</p> Signup and view all the answers

    What is the mathematical statement of the First Law of Thermodynamics?

    <p>dU = dQ - dW</p> Signup and view all the answers

    What is the corollary to the First Law of Thermodynamics?

    <p>There exists a property of closed system.</p> Signup and view all the answers

    What is the total energy of a system?

    <p>Internal energy, kinetic energy, potential energy, and others.</p> Signup and view all the answers

    What is a Perpetual Motion Machine of First Kind (PMM1)?

    <p>A machine that produces useful work without any source.</p> Signup and view all the answers

    Why is a Perpetual Motion Machine of First Kind (PMM1) impossible?

    <p>It violates the First Law of Thermodynamics.</p> Signup and view all the answers

    What is the cyclic integral of heat added equal to?

    <p>Integral of work done.</p> Signup and view all the answers

    What is the equation that represents the First Law of Thermodynamics?

    <p>()dQ - dW) = 0</p> Signup and view all the answers

    What is the SFEE equation for the throttle valve?

    <p>h1 + KE1 + PE1 = h2 + KE2 + PE2 + E</p> Signup and view all the answers

    What happens to energy in an isolated system?

    <p>Energy is constant.</p> Signup and view all the answers

    What is the purpose of a boiler?

    <p>To generate steam by heating water</p> Signup and view all the answers

    What is the SFEE equation for the condenser?

    <p>m (h1 - h2) = Q</p> Signup and view all the answers

    What is the property of a closed system that is changed by the difference between heat supplied and work done?

    <p>Internal energy.</p> Signup and view all the answers

    What is the purpose of a pump?

    <p>To increase the pressure of the fluid</p> Signup and view all the answers

    What is the term for the work done by the fluid as it enters or leaves a system?

    <p>Flow work</p> Signup and view all the answers

    What is the equation for the total work done during a steady flow process?

    <p>W_total = W_flow + W_shaft + W_internal</p> Signup and view all the answers

    What is the term for the heat transfer between the system and the surroundings?

    <p>External heat transfer</p> Signup and view all the answers

    What is the equation for the external heat transfer?

    <p>Q_external = m × cp × (T2 - T1)</p> Signup and view all the answers

    What is the term for the heat transfer due to frictional losses or other internal energy changes within the system?

    <p>Internal heat transfer</p> Signup and view all the answers

    What is the equation for the total heat transfer during a steady flow process?

    <p>Q_total = Q_external + Q_internal</p> Signup and view all the answers

    What is the unit of pressure in the equation W = F × L = pA × L?

    <p>Pa</p> Signup and view all the answers

    What is the primary function of a nozzle?

    <p>To increase the velocity of a fluid at the expense of pressure</p> Signup and view all the answers

    What is the equation for the work output of a turbine?

    <p>W = (m × (h1 - h2)) + (V1² - V2²) / 2 + (Z1 - Z2)</p> Signup and view all the answers

    What is the purpose of the SFEE in compressor design?

    <p>To design and optimize compressor performance, ensuring efficient compression and minimal energy losses</p> Signup and view all the answers

    What is the equation for the work input required to compress a fluid in a compressor?

    <p>W = (m × (h2 - h1)) + (V2² - V1²) / 2 + (Z2 - Z1)</p> Signup and view all the answers

    What is the primary function of a heat exchanger?

    <p>To transfer heat energy from one fluid to another</p> Signup and view all the answers

    What is the purpose of the SFEE in turbine design?

    <p>To determine the work output of a turbine</p> Signup and view all the answers

    What is the function of a throttle valve?

    <p>To restrict fluid flow, reducing pressure and temperature</p> Signup and view all the answers

    What is the equation for the work output of a turbine in terms of turbine efficiency?

    <p>?_t = (W / (m × (h1 - h2))) × 100</p> Signup and view all the answers

    What is the equation for the compressor efficiency?

    <p>?_c = (W / (m × (h2 - h1))) × 100</p> Signup and view all the answers

    Study Notes

    First Law of Thermodynamics

    • The first law states that energy is neither created nor destroyed, but can be converted from one form to another.
    • The total energy of the universe is a constant.

    Corollaries to the First Law

    • There exists a property of a closed system called internal energy (U), which changes by the difference between heat supplied and work done.
    • For an isolated system, energy is constant, and neither heat nor work interactions occur.
    • It is impossible to create a perpetual motion machine of the first kind, which would produce useful work without any energy input.

    Steady Flow Energy Equation (SFEE)

    • The SFEE is a fundamental equation that relates the energy changes between the inlet and outlet of a control volume.
    • The SFEE accounts for energy losses due to heat transfer, friction, and other interactions.
    • The SFEE is written as: m (h1 + KE1 + PE1) = m (h2 + KE2 + PE2) + E

    Applications of SFEE

    Nozzles

    • SFEE helps understand the relationship between inlet and outlet conditions.
    • The equation reduces to: h1 + KE1 = h2 + KE2, showing a conversion of thermal energy to kinetic energy.

    Diffusers

    • SFEE helps understand the relationship between inlet and outlet conditions.
    • The equation reduces to: h1 + KE1 = h2 + KE2, showing a conversion of kinetic energy to thermal energy.

    Turbines

    • SFEE helps design and optimize turbine performance.
    • The equation is used to determine the work output (W) of a turbine.

    Compressors

    • SFEE is essential for designing and optimizing compressor performance.
    • The equation is used to determine the work input (W) required to compress a fluid.

    Heat Exchangers

    • SFEE helps analyze the heat transfer process.
    • The equation is: m1 (h1 - h2) = m2 (h3 - h4)

    Throttle Valve

    • SFEE applies to the throttle valve, showing a conversion of thermal energy to kinetic energy.

    Boiler

    • SFEE helps analyze the energy transfer in a boiler.
    • The equation is: m (h2 - h1) = Q

    Condenser

    • SFEE applies to the condenser, showing a conversion of thermal energy to kinetic energy.

    Pump

    • SFEE helps analyze the energy transfer in a pump.
    • The equation is: h1 + p1/ρg + V1²/2g + z1 = h2 + p2/ρg + V2²/2g + z2

    Work Done During Steady Flow Processes

    • Work done during steady flow processes can be categorized into three types: flow work, shaft work, and internal work.
    • The total work done is the sum of these three types of work.

    Heat Transfer During Steady Flow Processes

    • Heat transfer can be categorized into two types: external heat transfer and internal heat transfer.
    • The total heat transfer is the sum of external and internal heat transfer.

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    Description

    This quiz covers the application of the First Law of Thermodynamics to flow processes, including the concept of internal energy and the equation dU = dQ - dW. Test your understanding of the first law equation and its corollaries.

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