Thermodynamics for Mechanical Engineering

In thermodynamics, thermodynamic work is the quantity of energy transferred from one system to another. It is a generalization of the concept of mechanical work in mechanics. In the SI system of measurement, work is measured in joules (symbol - J). The rate at which work is performed is power.

According to the classical sign convention, heat transfer to a system and work done by a system are positive; heat transfer from a system and work done on a system are negative.

A Path function is a function whose value depends on the path followed by the thermodynamic process irrespective of the initial and final states of the process.

Throughout the entire reversible process, the system is in thermodynamic equilibrium with its surroundings. ... In an ideal thermodynamic reversible process, the energy from work performed by or on the system would be maximized, and that from heat would be zero.Let's understand with this lecture,the various PdV works associated with different thermodynamic reversible processes.

A polytropic process is a thermodynamic process that obeys the relation:

PV^n = C

where P is the pressure, V is volume, n is the polytropic index, and C is a constant. The polytropic process equation can describe multiple expansion and compression processes which include heat transfer.

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, and thermal radiation.

The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.

Enthalpy is a thermodynamic property of a system. It is the sum of the internal energy added to the product of the pressure and volume of the system. It reflects the capacity to do non-mechanical work and the capacity to release heat.

Enthalpy is denoted as H; specific enthalpy denoted as h.

The mass flow rate is the mass of a liquid substance passing per unit time. In other words, Mass flow rate is defined as the rate of movement of liquid mass through a unit area. The mass flow is directly depended on the density, velocity of the liquid and area of cross-section. It is the movement of mass per unit time.

SFEE (Steady Flow Energy Equation) is an equation that describes the total engergy flows of an open system. It is assumed that the mass flow through the system is constant (this is why it is called 'Steady Flow Energy'). The SFEE is used to analyze a fluid flow across a piping system with the consideration of losses.

In this lecture we shall understand the derivation of SFEE (Steady Flow Energy Equation).

A throttling process is defined as a process in which there is no change in enthalpy from state one to state two, h1 = h2; no work is done, W = 0; and the process is adiabatic, Q = 0. ... An example of a throttling process is an ideal gas flowing through a valve in mid position.

A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact.

The First Law of Thermodynamics states that energy cannot be created or destroyed; the total quantity of energy in the universe stays the same. The Second Law of Thermodynamics is about the quality of energy. It states that as energy is transferred or transformed, more and more of it is wasted.

The second law of thermodynamics essentially gives the "DIRECTION" of heat transfer.....

The Kelvin–Planck statement (or the Heat Engine Statement) of the second law of thermodynamics states that it is impossible to devise a cyclically operating heat engine, the effect of which is to absorb energy in the form of heat from a single thermal reservoir and to deliver an equivalent amount of work.

Clausius Statement from the second law of thermodynamics states that: “It is impossible to design a device which works on a cycle and produce no other effect other than heat transfer from a cold body to a hot body.” That is, heat transfer can only occur spontaneously in the direction of temperature decrease.

The Carnot cycle is a theoretical ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s.

An ideal reversible closed thermodynamic cycle in which the working substance goes through the four successive operations of isothermal expansion to a desired point, adiabatic expansion to a desired point, isothermal compression, and adiabatic compression back to its initial state.

Unlike the Carnot heat engine, the Carnot refrigeration cycle undergoes a process with opposite direction which is referred as reverse carnot cycle(since it under goes path opposite to that of carnot cycle and hence the name reverse carnot cycle.

A thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.

In statistical mechanics, entropy is an extensive property of a thermodynamic system. It is closely related to the number Ω of microscopic configurations that are consistent with the macroscopic quantities that characterize the system.

The Clausius theorem is a mathematical explanation of the second law of thermodynamics. It was developed by Rudolf Clausius who intended to explain the relationship between the heat flow in a system and the entropy of the system and its surroundings. Clausius developed this in his efforts to explain entropy and define it quantitatively. In more direct terms, the theorem gives us a way to determine if a cyclical process is reversible or irreversible. The Clausius theorem provides a quantitative formula for understanding the second law.

Please find the attachment to collect the "FULL" notes of this course.

So this here is the last lecture of the course. I hope you understood everything.

All the very BEST !!