Thermodynamics Concepts Quiz

Course Information

• Course title: 5ENT1129 Thermodynamics for Aerospace
• Lecturer: Dr. Burhan Saeed
• University: University of Hertfordshire (UH)

Lecture 1 - Introduction to Thermodynamics

• Thermodynamics derives from Greek words "therme" (heat) and "dynamis" (power)
• Thermodynamics is a study of energy and its transformations, encompassing various aspects of life and engineering systems.
• Two main approaches exist in thermodynamics: classical (macroscopic) and statistical (microscopic)
• Classical approach focuses on the average behaviour of a large group of particles, while the statistical approach investigates individual particle behaviour
• Terminology: system, surroundings, boundary
• A system can be classified as open, closed, or isolated.
• Open systems can exchange both mass and energy with their surroundings (e.g., human body, boiler).
• Closed systems can only exchange energy with the surroundings, not mass (e.g., pressure cooker, home heating system).
• Isolated systems can't exchange either mass or energy with their surroundings (e.g., the universe).

Systems with moving boundaries

• In systems with moving boundaries, the boundary itself can change size, impacting the calculations of the system.

Properties of systems

• System properties can be intensive (independent of mass like temperature, pressure, density) or extensive (dependent on mass such as total mass, total volume).
• Intensive properties are often expressed per unit mass.

Density and Specific Gravity

• Density (ρ): Mass per unit volume (kg/m³)
• Specific volume (v): Volume per unit mass (m³/kg)
• Specific gravity (SG): Ratio of density of a substance to density of water (dimensionless)
• Specific weight (γs): Weight per unit volume(N/m³)
• Relations between all the given quantities

State and Equilibrium

• Equilibrium state: Properties of a system have fixed values throughout.
• Equilibrium criteria: Thermal equilibrium (same temp throughout), Mechanical equilibrium (no pressure changes with time), Phase equilibrium (mass of each phase reaches equilibrium and stays there), Chemical equilibrium (chemical composition doesn't change).

Processes and Cycles

• Quasi-equilibrium process: System undergoes infinitesimal changes, remaining close to an equilibrium state.
• Process diagrams: Diagrams that graphically represent processes, helping to visualize work done.
• Isothermal processes: Constant temperature.
• Isobaric processes: Constant pressure.
• Isochoric processes: Constant volume.
• Cycles: Processes where the system returns to its initial state.

The first law of thermodynamics

• Energy conservation: Energy cannot be created or destroyed; it can only change form or location.
• ΔU = Q - W
• U: Internal energy of the system
• Q: Heat transferred into the system.
• W: Work done by the system.

Adiabatic processes

• A process in which no heat exchange with the surrounding takes place (q = 0).

Energy transfer and heat

• Heat is a form of energy transfer due to a temperature difference.
• Rate of heat transfer is dependent on temperature difference.

Energy transfer by work

• Work is a form of energy transfer associated with a force acting through a distance.
• Work is done when a force causes movement.
• Different types of work can be done, including shaft work, boundary work etc.

Different forms of energy

• Kinetic energy (KE): Energy of motion
• Potential energy (PE): Energy of position
• Internal energy: microscopic/molecular energy (U)

Steady and uniform processes

• Stationary flows: No accumulation of mass, energy, or other thermodynamic properties in the control volume.
• Steady conditions: Properties remain unchanged over time at every point within the control volume.
• Steady flow processes: Flows steadily through a control volume, fluid properties can change from point to point.

Reverse and Irreversible Process

• Reversible Processes: Process that can be reversed without leaving any trace on the surroundings.
• Irreversible processes: Processes that are not reversible.

Unit of Measure for Temperature

• Units: Kelvin (K)
• Relation to Celsius (°C) (°C=K−273.15)

Temperature Scales – Celsius and Fahrenheit

• Celsius scale (0 degrees is the freezing point of water, 100 degrees is the boiling point of water)
• Fahrenheit scale (32 degrees is the freezing point of water, 212 degrees is the boiling point of water)
• Conversion formulas between Celsius and Fahrenheit

Understanding the First Law of Thermodynamics

• Conservation of energy. The change in energy of a system is equal to the sum of the energy transferred to or from the system as heat and work
• AU = Q - W

Adiabatic processes

• No heat transfer occurs in adiabatic processes

The First Law of Thermodynamics– Examples

• In the absence of work interactions, the energy change of a system is equal to the net heat transfer.

Properties of Fluids

• Different states (solid, liquid, gaseous) of a pure substance with phase changes that occur between them.

Recap

• First law of thermodynamics
• Energy transfer in the form of heat and work
• Change in internal energy (ΔU) = Q – W, for a closed system.
• Generalisation to open systems involves rates of heat transfer to and from the system and shaft work.
• The steady flow energy equation, and the effect of mechanical devices: pumps, turbines, valves, and nozzles.

Various thermodynamic cycles

• Different types of cycles like Isothermal, Isobaric, Isochoric, Adiabatic, Isentropic, Isenthalpic cycles and their components along with the thermodynamic properties. (e.g., Rankine cycle, Diesel cycle, Ericson cycle etc.)

Heat Engine Processes

• Different cycles commonly encountered in real heat engines along with their components. (e.g., Carnot thermodynamic cycles, Rankine Cycle, Diesel, Otto, etc.)

Recap of Thermodynamic Processes

• Summary points of thermodynamic processes

Thermodynamics

• Key concepts of thermodynamics; Extensive, intensive and specific properties.

Thermodynamic Property Tables

• Extensive tabulations of thermodynamic property data for various substances (e.g., water/steam tables, ideal gas properties of air).
• Steam tables provide the saturation temperature and pressure values of a pure substance.
• Superheated water gives properties of superheated steam.

Enthalpy

• A combination of internal energy (U) and pressure-volume product (PV).
• Enthalpy is a thermodynamic property.
• Useful in steam turbine analysis: specific enthalpy (h) and total enthalpy (H)

Saturated Liquid and Vapour States

• Properties of saturated liquid and vapour substances.
• Tables are available for many substances.

Linear Interpolation

• Numerical technique to find intermediate values between existing data points in thermodynamic property tables

Heat Pump

• Working on principle similar to a refrigerator
• Purpose is to heat a system by transferring thermal energy from a cold reservoir to a hot reservoir.
• Examples, applications and basic components

Refrigeration Systems

• Working on a similar principle to a heat pump but with the goal of cooling rather than heating.
• Examples, applications, basic components

Entropy

• Thermodynamic property that quantifies the irreversibility associated with a system undergoing a process.
• Measure how random/disordered a system is. A system's tendency towards increased entropy.

The Second Law of Thermodynamics

• Thermodynamic processes are directional; they can occur spontaneously in a certain direction but not in the opposite direction.
• The total entropy of an isolated system can only increase over time or remain constant in ideal cases.
• Statements of Second Law.
• Relation between the first and second laws.

Specific Heat

• Molar Heat Capacity (intensive) of gases and fluids at constant pressure & constant volume, along with its derivation.

Ideal Gas – Equations of State

• Definition and nature of ideal gases
• Derivation of the equation of state, PV=nRT, which relates pressure(P), volume(V), number of moles(n) and absolute temperature(T)

The adiabatic process of an ideal gas

• PV^k = constant
• Derivation of the equation

Test your understanding of key thermodynamics concepts, including kinetic and potential energy, the laws of energy conservation, and different types of processes such as isothermal and isobaric. This quiz covers definitions, formulas, and practical applications related to energy in systems.