# An irreversible adiabatic cyclic process is possible

## What is thermodynamic process definition?

A thermodynamic process is defined as a change from one equilibrium macrostat to another macrostat. Knowledge of thermodynamic processes is of the utmost importance for engineers. Thermal engineering

### Reversible process

In thermodynamics, areversible process defined as a process by inducinginfinitesimal changes on a property of the systemvice versa without changing the system or the environment. During the reversible process, theentropy of the systemnot to and the system is in thermodynamic equilibrium with its surroundings.

### Irreversible process

In thermodynamics, airreversible process defined as a process that cannot be reversed, a process that cannot restore both the system and the environment to their original state.

During theirreversible process takes theentropy of the systemto .

### Cyclical process

A process that eventually returns a system to its original state is called acalled cyclic process . At the end of a cycle, all properties have the same value as at the beginning. For such a procedure, theFinal state is thesame as the initial state , So that thetotal internal energy Change must be zero.

It must be noted that after thesecond law of thermodynamics not all of the heat that is fed into a circuit can be converted into the same amount of work, but that a certain amountHeat emission must take place. Thethermal efficiency , ηth , a heat engine as the ratio of labor it does,W. , to the heat input at high temperature, QH .  ηth = W / Q -H .

### Isentropic process

Aisentropic process is athermodynamic process where theentropyof the fluid or gas remains constant. This means that theisentropic process a special case of oneadiabatic process is in which no heat or matter transfer takes place. It is areversible adiabatic process . Aisentropic process can also be referred to as a constant entropy process. In technology, such an idealized process is very useful for comparison with real processes.

PV diagram of an isentropic expansion of helium (3 → 4) in a gas turbine.

Aadiabatic process is a thermodynamic process in whichno heat transfer into or out of the system (Q = 0). The system can be used as abe viewed in perfect isolation . In an adiabatic process, energy is only transferred as work. The assumption that there is no heat transfer is very important because we can only use the adiabatic approximation incan use very fast processes . These rapid processes do not leave enough time for energy to be transferred as heat to or from the system.

Step into real devices (such as turbines, pumps, and compressors)Heat losses and losses in the combustion process. However, these losses are usually small compared to the total energy flow, and we can approximate some thermodynamic processes through the adiabatic process.

### Isothermal process

Aisothermal process is athermodynamic process where thetemperature of the systemremains constant (T = const). The heat transfer into or out of the system typically has to take place at such a slow speed that it is continuously adapted to the temperature of the storage tank through heat exchange. That remains in each of these statesthermal equilibrium receive.

For aideal gasand a polytropic process corresponds to the casen = 1 oneisotherms Process (constant temperature). In contrast to theadiabatic process , in whichn = κ and a system does not exchange heat with its surroundings (Q = 0; ∆T ≠ 0), the internal energy does not change in an isothermal process (due to ∆T = 0)) and therefore ∆U = 0 (for ideal gases) and Q ≠ 0. An adiabatic process is not necessarily an isothermal process, nor is an isothermal process necessarily adiabatic.

Boyle Mariotte Law. With a solid gas mass at constant temperature, the volume is inversely proportional to the pressure. Source: grc.nasa.gov NASA's copyright policy states that “NASA material is not copyrighted unless otherwise stated”.

### Isobaric process

Aisobaric process is a thermodynamic process in which theprint of the systemremains constant (p = const). The heat transfer in or out of the system works, but also changes the internal energy of the system.

Since the internal energy (dU) and the system volume (∆V) change, engineers often use theEnthalpy of the system, which is defined as follows:

H = U + pV

In many thermodynamic analyzes it is useful to use theEnthalpy instead of using internal energy. Especially in the case of thefirst law of thermodynamics .

Both very important thermodynamic cycles are based in technology (Brayton and Rankine cycle ) ontwo isobaric processes , so studying this process is critical for power plants.

With a solid gas mass at constant pressure, the volume is directly proportional to the Kelvin temperature. Source: grc.nasa.gov NASA's copyright policy states that “NASA material is not copyrighted unless otherwise stated”.

### Isochoric process

Aisochoric processis a thermodynamic process in which thevolume of the closed systemremains constant (V = const). It describes the behavior of gas in the container that cannot be deformed. Since the volume remains constant, the heat transfer in or out of the system does not work with p∆V, but only changes theinner energy (the temperature) of the system.

In the construction ofInternal combustion engines Isochoric processes are very important for their thermodynamic cycles (Otto and Diesel cycle), therefore the investigation of this process is of crucial importance for automotive engineering.

With a fixed gas mass at constant volume, the pressure is directly proportional to the Kelvin temperature.

### Polytropic process

Apolytropic process is a thermodynamic process that can be expressed by the following equation:

pVn = constant

Thepolytropic process can describe the gas expansion and compression thatinclude heat transfer . The exponentn is asPolytropic index known and can have any value from 0 to ∞ depending on the process.

Polytropic processes with different polytropic indices.

### Throttling process - isenthalpic process

AThrottling process is athermodynamic process where theEnthalpy of the gas or mediumremains constant (h = const) . Indeed it isThrottling process one ofisenthalpic processes . During the throttling processno work executed by or on the system (dW = 0), and usually findsno heat transfer ( adiabatic ) from or into the system (dQ = 0). On the other hand, the throttling process cannot be isentropic, but is abasically irreversible process . Features of the throttling process:

1. No transfer of work
2. No heat transfer
3. Irreversible process
4. Isenthalpic process

The dampening of the steam is also with theConservation of enthalpy connected . In this case aPressure reduction, however to aIncrease in steam quality .