Thermodynamic Relations | Mechanical Engineering SSC JE (Technical) PDF Download

THERMODYNAMIC RELATIONS EQUILIBRIUM AND STABILITY

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

where
g is Gibbs function

  •  Maxwell's equations

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)
Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Joule-Thompson Effect

When a gas is throttled then first its temperature increase (heating) as the pressure decrease but after a particular pressure, temperature decrease (cooling) as pressure decrease. At different initial temperature different such pressure exist.

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

  •  The curve connecting all transition point is inversion curve.
  • The Joule-Thompson Coefficient is:

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

  • For ideal gas μj = 0 i.e. in throttling process temperature of ideal gas remains constant.
  • If initial temperature and pressure are within inversion curve, i.e. below maximum inversion temperature, cooling happens.
  • Except Hydrogen and Helium the maximum inversion temperature of all the other gases is more than atmospheric temperature so cooling occurs in throttling of those gases.
  • For Hydrogen and Helium maximum inversion temperature is below atmospheric temperature so heating occurs after throttling.
  • For cooling of Hydrogen and Helium after throttling, they should initially be cooled below their maximum inversion temperature.
  • There is no change in Temperature when an ideal gas is made to under go a Joule-Thompson expansion

Clausius-Clapeyron equation

  • Clausis-Clayperon equation is a way of characterizing a discontinuous phase transition between two phases of matter of a single constituent.
  • On a P-T diagram, the line separating two phases is known as the coexistence curve.

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

where dp/dT is the slope of the tangent to the co-existence curve at any point, l is the specific latent heat, T is the temperature and V is the specific volume change and S stands for specific entropy.

where,

Sf = entropy of the final phase

Si = entropy of the initial phase

Vf = volume of the final phase

Vi = volume of the initial phase

Triple Point

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Thermodynamic Relations | Mechanical Engineering SSC JE (Technical)

Phase diagram for water and any other substance on p–T coordinates.

  •  Slope of sublimation curve at the triple point is greater than that of the vaporization curve.

i.e. (dy/dx)sublimation > (dy/dx)vaporization

  • Gibbs phase rule for non reactive system

Degree of freedom:

f = c – p + 2
c — no. of components
p — no. of phases

The document Thermodynamic Relations | Mechanical Engineering SSC JE (Technical) is a part of the Mechanical Engineering Course Mechanical Engineering SSC JE (Technical).
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FAQs on Thermodynamic Relations - Mechanical Engineering SSC JE (Technical)

1. What are the four laws of thermodynamics?
Ans. The four laws of thermodynamics are as follows: 1. Zeroth Law of Thermodynamics: If two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. 2. First Law of Thermodynamics: Energy cannot be created or destroyed; it can only be transferred or converted from one form to another. 3. Second Law of Thermodynamics: The entropy of an isolated system always increases over time. 4. Third Law of Thermodynamics: As the temperature approaches absolute zero, the entropy of a system approaches a minimum value.
2. What is the significance of thermodynamic relations in mechanical engineering?
Ans. Thermodynamic relations play a crucial role in mechanical engineering as they provide a mathematical framework to analyze and understand the behavior of thermodynamic systems. These relations allow engineers to determine various properties of fluids and materials, such as temperature, pressure, entropy, and specific heats, under different conditions. By utilizing thermodynamic relations, engineers can design efficient and reliable systems, optimize energy usage, and make informed decisions on process control and equipment selection.
3. How can thermodynamic relations be applied to solve practical engineering problems?
Ans. Thermodynamic relations can be applied to solve practical engineering problems by using them to derive equations and relationships between various thermodynamic properties. These equations can then be utilized to analyze and predict the behavior of systems in real-world scenarios. For example, thermodynamic relations can be used to determine the efficiency of a heat engine, calculate the work done during a thermodynamic process, or estimate the heat transfer rate in a heat exchanger. By applying thermodynamic relations, engineers can optimize system performance, identify potential issues, and ensure the efficient utilization of energy resources.
4. What are some common applications of thermodynamic relations in mechanical engineering?
Ans. Some common applications of thermodynamic relations in mechanical engineering include: - Analysis and design of heat exchangers: Thermodynamic relations can be used to calculate the heat transfer rate, effectiveness, and overall efficiency of heat exchangers, which are widely used in various industries for heat recovery and temperature control. - Power plant engineering: Thermodynamic relations are essential in analyzing and designing power plants, including steam power plants, gas turbine power plants, and combined cycle power plants. These relations help engineers determine the efficiency and performance characteristics of these systems. - Refrigeration and air conditioning systems: Thermodynamic relations are used to analyze and optimize the performance of refrigeration and air conditioning systems, including determining the coefficient of performance and assessing the energy efficiency of these systems. - Combustion analysis: Thermodynamic relations are applied to analyze the combustion process in internal combustion engines, gas turbines, and boilers. They help determine the efficiency, specific fuel consumption, and emissions characteristics of these systems. - Fluid flow analysis: Thermodynamic relations are utilized to analyze and predict the behavior of fluids in pipes, nozzles, and turbines. They assist in determining pressure drop, flow rate, and efficiency of fluid flow systems.
5. How can thermodynamic relations be used to optimize energy usage in mechanical systems?
Ans. Thermodynamic relations can be used to optimize energy usage in mechanical systems by providing insights into the efficiency and performance characteristics of these systems. By utilizing thermodynamic relations, engineers can identify areas of energy loss, quantify the impact of different parameters on system performance, and make informed design decisions to minimize energy consumption. For example, in a power plant, thermodynamic relations can help engineers optimize the boiler and turbine design to maximize the conversion of fuel energy into electricity. By analyzing the thermodynamic properties and applying relations such as the Rankine cycle, engineers can identify opportunities for improving the efficiency of the system, such as increasing the steam temperature and pressure or reducing the condenser pressure. Similarly, in refrigeration and air conditioning systems, thermodynamic relations can be used to optimize the design of components such as compressors, condensers, and evaporators to achieve the desired cooling effect with minimal energy input. Overall, by utilizing thermodynamic relations, engineers can make informed decisions to optimize energy usage, reduce environmental impact, and improve the overall efficiency of mechanical systems.
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