Types of systems in thermodynamics
Thermodynamics is a branch of physics that deals with heat and temperature, and their relation to energy, work, radiation, and the properties of matter. The principles of thermodynamics apply everywhere in our daily lives, from refrigeration and air conditioning systems to the engines in cars. To understand thermodynamics, one must first understand the different types of systems involved in the study. A system in thermodynamics refers to the part of the universe that is being studied, while everything outside the system is its surroundings.
Overview of thermodynamic systems
In thermodynamics, a system is defined by a certain quantity of matter or a region in space under observation. A system can be classified in three main ways based on the exchange of energy and mass between the system and its surroundings: isolated system, closed system, and open system.
Isolated system
An isolated system is one where neither mass nor energy is allowed to cross the boundary. It is completely insulated from its surroundings. Think of it as a completely sealed and insulated flask where no heat can flow out or in, and no matter can be added or removed. This system is an idealization, as no perfect isolated systems exist, but it is a useful model for understanding fundamental thermodynamics principles.
Example: A thermos bottle or an idealized solar system.
Closed system
A closed system is a type where the system can exchange energy (as heat or work), but not mass, with its surroundings. This means that the amount of material inside the system remains the same, but the system can get hotter or colder depending on external conditions. A common example of a closed system is a pot with a lid. Heat can be transferred in and out of the pot, but no steam escapes when the lid is secured.
Example: A pressure cooker during cooking.
Open system
An open system is one where both energy and mass can be exchanged with the surroundings. It is the most common type of system found in nature. Most living organisms as well as many engineered systems are open systems. In an open system, matter can be transferred into or out of the system, and energy can be added or lost from the system.
Example: Boiling water in an uncovered pot.
System boundary and environment
The boundary of a thermodynamic system is important because it defines the boundaries of the system. The boundary can be real or imaginary and movable or fixed. The surroundings are everything that lies outside the boundary, and the interactions between the system and its surroundings are the basis of thermodynamics studies. Each type of system has its own unique boundary properties, which determine the direction of energy flow.
Examples in daily life
To better understand thermodynamic systems, let's look at some more real-life examples:
1. Refrigerator
A refrigerator is a great example of a closed system. The boundaries of a refrigerator allow heat to transfer out of the system, keeping the inside cool, but the mass inside (e.g. food, drinks) remains stationary unless it is manually added or removed.
2. Automobile engine
The engine of a car works as an open system. Fuel is added and burned, resulting in the production of heat energy that moves the car. The engine accepts the input of air and fuel, and it emits heat and exhaust gases.
3. Thermos Flask
A thermos flask is designed to maintain the temperature of its contents over time, without any transfer of heat or matter, making it a perfect example of an isolated system, although not a perfect one, as some heat transfer may occur over an extended period of time.
Thermodynamic processes
Thermodynamics also studies the processes systems go through that involve changes in temperature, energy, and matter. These include:
Isothermal process
An isothermal process is one in which the temperature of the system remains constant. In such a process, if the system is in an open state, it can exchange mass with the environment, but the changes in temperature, pressure, volume correspond to the equation:
P1 * V1 = P2 * V2
Adiabatic process
Adiabatic processes occur without any heat exchange between the system and its surroundings. Such processes are important in closed systems and can be expressed as follows:
PV^𝛾 = constant
Conclusion
In summary, understanding the types of thermodynamic systems is paramount in the study of thermodynamics. Isolated, closed, and open systems each have their own unique characteristics and applications in the real world. Understanding the differences can help in understanding how systems interact with their environment, undergo changes, and perform work. Thermodynamics is not just a theoretical concept but a practical aspect of many industries and natural phenomena.