Thermodynamics: First Law Applied to Flow Processes

Questions and Answers

What is the mathematical statement of the first law of thermodynamics?

dQ = dW

What is the corollary to the first law of thermodynamics that states that there exists a property of a closed system?

Corollary 1

What is the term for the total energy of a system that includes internal energy, kinetic energy, potential energy, and more?

Total energy

What is a hypothetical machine that violates the first law of thermodynamics by creating energy?

Perpetual Motion Machine of First Kind Signup and view all the answers

What is the characteristic of a system where heat and work interactions are absent?

Isolated System Signup and view all the answers

What is the significance of the equation dU = dQ - dW?

It shows that energy can be transferred from one form to another Signup and view all the answers

What is the fundamental principle stated by the first law of thermodynamics?

Energy is neither created nor destroyed Signup and view all the answers

What is the result of the cyclic integral of heat added and the integral of work done during a thermodynamic cycle?

dQ - dW = 0 Signup and view all the answers

What is the consequence of the first law of thermodynamics for the universe as a whole?

The total energy of the universe is constant Signup and view all the answers

What is the name of the machine that violates the first law of thermodynamics by producing useful work without any source?

Perpetual Motion Machine of First Kind Signup and view all the answers

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

Both the first and second laws of thermodynamics Signup and view all the answers

What is the consequence of an electric heater that consumes 1KW of electricity?

It can produce less than 1KW of heat Signup and view all the answers

What type of flow is characterized by a constant rate of fluid flow through a machine or apparatus?

Steady flow Signup and view all the answers

What is the assumption made in the system analysis of the steady flow energy equation?

The mass flow rate remains constant Signup and view all the answers

What is the term for the energy associated with the motion of a fluid?

Kinetic energy Signup and view all the answers

What is the equation that relates the energy changes between the inlet and outlet of a control volume?

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

What is the term for the energy required to move a fluid in and out of a control volume?

Flow work Signup and view all the answers

What is the formula for work done by a piston in moving a unit mass of fluid?

Work done = Force × Displacement Signup and view all the answers

What is the consequence of an open system with no variation of flow of mass or energy with time?

Steady flow Signup and view all the answers

What is the term for the energy lost due to heat transfer, friction, etc.?

Energy loss Signup and view all the answers

What is the unit of pressure in the flow work or flow energy equation?

Pa Signup and view all the answers

What is the purpose of a nozzle in a fluid flow system?

To convert thermal energy to kinetic energy Signup and view all the answers

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

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

What is the purpose of a compressor in a fluid flow system?

To increase the pressure of a fluid while decreasing its velocity Signup and view all the answers

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

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

What is the purpose of a heat exchanger in a fluid flow system?

To transfer heat energy from one fluid to another Signup and view all the answers

What is the equation for the heat transfer process in a heat exchanger?

m1 (h1 - h2) = m2 (h3 - h4) Signup and view all the answers

What is the purpose of a throttle valve in a fluid flow system?

To restrict fluid flow, reducing pressure and temperature Signup and view all the answers

What is the unit of flow work or flow energy?

J/kg Signup and view all the answers

What is the application of the steady flow energy equation in nozzles?

To analyze the relationship between the inlet and outlet conditions Signup and view all the answers

What does the SFEE apply to in the case of a throttle valve?

The conversion of thermal energy to kinetic energy Signup and view all the answers

What is the purpose of a boiler in a steam power plant?

To generate steam by heating water Signup and view all the answers

What is the purpose of a condenser in a steam power plant?

To condense steam back into liquid water Signup and view all the answers

What is the SFEE equation for a pump?

h_1 + rac{p_1}{?g} + rac{V_1^2}{2g} + z_1 = h_2 + rac{p_2}{?g} + rac{V_2^2}{2g} + z_2 Signup and view all the answers

What is the purpose of the SFEE in a pump?

All of the above Signup and view all the answers

What is the equation for flow work during steady flow processes?

W_flow = p_1V_1 - p_2V_2 Signup and view all the answers

What is the equation for external heat transfer during steady flow processes?

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

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

W_total = W_flow + W_shaft + W_internal Signup and view all the answers

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

Q_total = Q_external + Q_internal Signup and view all the answers

What is the purpose of the SFEE in a boiler?

To determine the energy added to the fluid by the boiler 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 thermodynamic cycles and internal energy. It explores the relationships between heat, work, and energy.