A polytropic process is any thermodynamic process that can be expressed by the following equation: pVn = constant. Definition and characteristics of Polytropic Process. Thermal Engineering

## Polytropic Process

**A polytropic process is any thermodynamic process that can be expressed by the following equation:**

**pV ^{n} = constant**

The **polytropic process** can describe gas expansion and compression which** include heat transfer**. The exponent **n** is known as the **polytropic index **and it may take on any value from 0 to ∞, depending on the particular process.

There are some **special cases of n**, which corresponds to particular processes:

- the case
*n =*p= constant**0**,*,*corresponds to an**isobaric (constant-pressure) process**. - the case
*n =*pV = constant**1**,*,*corresponds to an**isothermal (constant-temperature) process**. - the case
*n =**,*pV^{}= constant*,*corresponds to an**isentropic (constant-entropy) process**. - the case
*n**➝**∞***isochoric (constant-volume) process**.

- the case
**1 <**, in this process heat and work flows go in opposite directions, This process occurs, for example, in vapor compression refrigeration during compression*n <* - the case
**<**, in this process heat and work flows go in the same direction, This process occurs, for example, in an internal combustion engine (e.g. Otto cycle), in which there are heat loses through the cylinder walls during gas expansion (power stroke).*n <**∞*

For a** polytropic process** between two states:

**p_{1}V_{1}^{n} = p_{2}V_{2}^{n}**

We hope, this article, **Polytropic Process**, helps you. If so, **give us a like** in the sidebar. Main purpose of this website is to help the public to learn some interesting and important information about thermal engineering.