Thermodynamics Overview Quiz

Questions and Answers

What does it mean for a system to be in thermodynamic equilibrium?

Pressure and temperature remain constant throughout the process. (correct)

The system can exchange energy but not matter with its surroundings.

Pressure and temperature vary throughout the system.

Energy is being created and destroyed within the system.

Which law describes the relationship between heat supplied to a system and work done by the system?

Law of Increasing Entropy

First Law of Thermodynamics (correct)

Second Law of Thermodynamics

Law of Conservation of Energy

In an ideal thermodynamic cycle, what is the relationship between the internal energy at the beginning and the end of the cycle?

The internal energy remains the same. (correct)

The internal energy cannot be determined.

The internal energy decreases.

The internal energy increases.

What does the symbol Σ Q represent in the context of thermodynamics?

Net heat supplied to the system Signup and view all the answers

Which of the following is the correct constant of proportionality between net heat and net work according to the first law of thermodynamics?

4.18 kJ = 1 kilocaloric Signup and view all the answers

What must occur for a system operating in a cycle to transfer heat from a cooler to a hotter body?

Work must be done on the system by the surroundings. Signup and view all the answers

According to the first corollary of the second law, what does it imply about the conversion of heat into work?

It's impossible to convert heat continuously and completely into work. Signup and view all the answers

What does the first law state about a heat engine that delivers units of heat to the cold reservoir while performing work?

The heat supplied from the hot reservoir should equal work plus heat delivered to the cold reservoir. Signup and view all the answers

Which statement represents a violation of the second law of thermodynamics?

A heat pump can operate without any work input. Signup and view all the answers

What is the implication of performing work on a system that is trying to transfer heat from a cold to a hot reservoir?

It is necessary to facilitate the transfer of heat against the natural flow. Signup and view all the answers

What is the kinetic energy at the inlet if the inlet velocity is 50 m/s?

1.25 kJ/kg Signup and view all the answers

What is the power developed by the turbine in the gas turbine unit?

4000 kW Signup and view all the answers

What is the specific enthalpy of the gases at the outlet of the turbine?

360 kJ/kg Signup and view all the answers

In thermodynamics, work is defined as energy that appears at the boundary when what occurs?

A force moves an object through a distance. Signup and view all the answers

If the inlet velocity of a gas is 60 m/s, what would be the kinetic energy at the inlet?

1.8 kJ/kg Signup and view all the answers

How is work related to pressure and area in thermodynamics?

Work = Pressure x Area x Distance Signup and view all the answers

What is the specific volume of the gases at the inlet in the example provided?

0.5 m³/kg Signup and view all the answers

A process in thermodynamics is called reversible if what condition is met?

The state point can be located at any instant on a diagram. Signup and view all the answers

What does the variable 'x' represent in the context of wet vapour?

Mass of dry vapour in 1kg of the mixture Signup and view all the answers

Which equation represents the relationship between heat transfer and changes in internal energy for a system?

Q = Ug - Uf + P(Vg - Vf) Signup and view all the answers

What does the specific enthalpy of vapourization, hfg, represent?

Energy required to change liquid to vapour at constant pressure Signup and view all the answers

How can the specific volume of wet vapour be approximated under practical conditions?

Using the formula V = xVg Signup and view all the answers

Which of the following correctly represents the specific enthalpy of wet vapour?

h = (1 - x)hf + xhg Signup and view all the answers

If the pressure of dry saturated vapour is increased, what effect does it generally have on the specific enthalpy of the vapour?

Increases the specific enthalpy Signup and view all the answers

What is the relationship between specific internal energy (U) and the dryness fraction (x) for wet vapour?

U = Uf + xUg Signup and view all the answers

When calculating the work done (W) in a system, which of the following equations is correct?

W = -PdV = -P(V2 - V1) Signup and view all the answers

What is the first step to determine the temperature of the steam in a rigid vessel?

Calculate the specific volume using $v = \frac{V}{m}$ Signup and view all the answers

How is the dry saturated temperature found when cooling the steam until the pressure is 11 bar?

By observing the pressure and temperature relationship Signup and view all the answers

What is the formula used to calculate the final dryness fraction of the steam after cooling?

Dryness fraction = $\frac{t - 175.4}{x (179.9 - 175.4)}$ Signup and view all the answers

In an Otto cycle, what does the 'swept volume' refer to?

The volume difference between $V_1$ and $V_2$ Signup and view all the answers

What happens to the steam's energy when the vessel is cooled to a pressure of 11 bar?

Heat is rejected from the steam Signup and view all the answers

What contributes to calculating the specific volume of steam?

Pressure and mass of the steam Signup and view all the answers

What does the equation $t - 175.4 = \frac{?y}{x (179.9 - 175.4)}$ represent in the context of the steam calculations?

The relationship between temperature and specific volume Signup and view all the answers

Which aspect of the Otto cycle makes it suitable for spark-ignition engines?

It features a reciprocating piston design Signup and view all the answers

Study Notes

Thermodynamic Equilibrium

A system is in thermodynamic equilibrium when pressure and temperature remain constant.
Properties like pressure and temperature must be uniform throughout the system.
Systems can be classified into open systems (fluid in a turbine) and closed systems (fluid in a cylinder).

First Law of Thermodynamics

Energy conservation principle: energy can neither be created nor destroyed.
In a thermodynamic cycle, the net heat supplied is proportional to the net work done: ΣQ ∝ ΣW.
Proportionality constant: 1 kilocaloric = 4.18 kJ.

Steady Flow Energy Equation

Commonly represented as ṁ(c₁ + h₁) + Q̇ + Ẇ = ṁ(c₂ + h₂).
Kinetic Energy (K.E) can be calculated from fluid velocities at the inlet and outlet.
Example calculations show input and output conditions, mass flow rates, and energy exchanges in a turbine.

Work and Heat

Work is defined as energy transfer when a force moves an object through distance: W = Fd = (PA)d.
Work is measured in Joules (J).
Heat appears at system boundaries due to temperature difference with surroundings.

Reversible Processes

A reversible process allows a system to return to its original state without changes in surroundings.
Heat cannot be continuously converted into work without work being done on the system (Clausius' Second Law).

Clausius' Statement of the Second Law

It’s impossible to create a system that operates in a cycle and transfers heat from a cooler body to a hotter body without work being done.

Specific Heat and Entropy

Specific enthalpies and internal energies are critical to heat and work transfer calculations.
Dryness fraction (x) indicates the mass of dry vapor in a mixture, while wetness fraction represents liquid mass.

Heat Transfer Equation

Q + W = U₂ - U₁ relates heat, work, and internal energy changes.
Enthalpy change from saturated liquid to saturated vapor is called specific enthalpy of vaporization (hfg).

Specific Volume and Properties of Wet Steam

Specific properties (volume, enthalpy, internal energy) depend on pressure and dryness fraction.
Practical formulas substitute for volumetric calculations and can gauge total heat transfer during state changes.

Otto Cycle

The Otto cycle serves as the ideal model for spark-ignition engines, based on air standard assumptions.

Assignments and Example Calculations

Example problems highlight the cooling processes, steam states in rigid vessels, and thermodynamic efficiency.
Calculations involve determining temperature, pressure, and evaluating changes in states and properties through various thermodynamic principles.

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Description

Test your knowledge on thermodynamic concepts including equilibrium, the first law of thermodynamics, and energy transfer in fluid systems. Explore topics like steady flow energy equations and the definitions of work and heat. Perfect for students studying thermodynamics in engineering or physical sciences.