Isothermal vs Adiabatic Process: Difference and Comparison

Key Takeaways

1. The isothermal process is a thermodynamic process in which the temperature of a system remains constant.
2. An adiabatic process is a thermodynamic process in which no heat is transferred into or out of the system.
3. Isothermal processes are more efficient for some applications like heat exchanges because they maintain a constant temperature. In contrast, engines and compressors use the adiabatic process to maximize work output.

What is an Isothermal Process?

An isothermal process is a thermodynamic process in which the temperature of a system remains constant. This means that the system’s internal energy remains constant, and any heat added or removed from the system is perfectly balanced by the work done by or on the system.

The critical characteristic of an isothermal process is that as the volume of a gas increases, the pressure decreases, and vice versa. In contrast, the product of the volume and pressure remains constant.

During an isothermal process, the ideal gas law is used to describe the behavior of the gas. One practical application of an isothermal process is operating a heat exchanger. The process ensures the temperature remains constant, allowing for efficient heat transfer between two fluids.

What is an Adiabatic Process?

An adiabatic process is a thermodynamic process in which no heat is transferred into or out of the system. In other words, the system is thermally isolated from its surroundings. During an adiabatic process, the system’s internal energy change is solely due to work done or by the system.

The essential characteristic of the adiabatic process is the rapid change in temperature and pressure. When a gas is compressed adiabatically, its temperature and pressure increase.

Adiabatic processes are commonly encountered in various engineering applications, including the compression of gases in engines and compressors. For instance, in internal combustion engines, the compression stroke is adiabatic, resulting in a rapid temperature increase and enhancing efficiency.

Difference Between Isothermal and Adiabatic process

1. In an isothermal process, the temperature remains constant, and heat is added or removed to maintain a continuous pressure. In contrast, there is no heat transfer in an adiabatic process, resulting in rapid temperature changes.
2. In an isothermal process, work is done during the gas’s expansion or compression, but the gas’s total internal energy remains constant. In contrast, work is done in an adiabatic process and the gas’s internal energy changes due to temperature variations.
3. Isothermal processes are more efficient for some applications like heat exchanges because they maintain a constant temperature. In contrast, engines and compressors use the adiabatic process to maximize work output.
4. Isothermal processes are used in refrigeration, heat exchangers, and air conditioning systems where temperature control is crucial. In contrast, adiabatic processes are employed in internal combusting engines, compressors, and meteorology to explain the behavior of rising and sinking air masses in the atmosphere.
5. Isothermal processes are more reversible because they occur slowly and maintain constant pressure, while adiabatic processes can be less reversible due to rapid temperature changes.

Comparison Between Isothermal and Adiabatic Processes

Parameters	Isothermal Process	Adiabatic Process
Temperature	Remains constant as heat is added or removed	Rapid temperature changes as there is no heat transfer
Work done	During the expansion or compression of gas	The internal energy of the gas changes due to temperature variations
Efficiency	For some applications like heat exchanges	Used in engines and compressors to maximize work output
Use Cases	Used in refrigeration, heat exchangers, and air conditioning	Employed in internal combusting engines, compressors, and meteorology
Reversibility	They are more reversible as they maintain a constant pressure	Less reversible due to temperature changes

References

1. https://aapt.scitation.org/doi/pdf/10.1119/1.2344391
2. https://iopscience.iop.org/article/10.1086/313093/meta