(Inst. or False) Flow work (v) is the work done on a closed system by a paddle wheel or a piston.
The correct answer and explanation is :
The statement is True.
Flow work (v) refers to the energy required to push a fluid into or out of a system, and it is often associated with mechanical devices like a paddle wheel or a piston. In thermodynamics, when a fluid flows through a control volume (such as a pipe or a pump), the flow work represents the energy needed to move the fluid into the system and maintain flow.
Here’s an explanation of why this is true:
1. Definition of Flow Work:
Flow work is the work needed to push a fluid into or out of a system boundary. The term is used when dealing with open systems (control volumes) where mass enters and exits the system. It’s the energy required to overcome the pressure at the inlet of the system to get the fluid to flow.
2. Work Done by Mechanical Devices:
In thermodynamics, systems can be closed or open. A closed system does not exchange mass with its surroundings, but an open system allows mass to enter or leave. When a fluid is moved into or out of such an open system, a device like a piston or a paddle wheel can be used. The work done by the piston or the paddle wheel (which could be mechanical or electrical work) aids in transferring fluid across the system boundary.
3. Flow Work in the Context of Thermodynamics:
The flow work (W_{flow}) can be mathematically expressed as:
[
W_{flow} = P \cdot v
]
Where:
- (P) is the pressure of the fluid.
- (v) is the specific volume of the fluid.
This equation shows that the work required to move the fluid into a system depends on the pressure exerted by the fluid and its volume. In practice, mechanical devices such as pistons or paddle wheels are used to apply the required force to move the fluid, thus performing the necessary flow work.
In conclusion, flow work is the energy required to move a fluid in and out of a system, and mechanical devices such as paddle wheels or pistons are often used to do this work, making the statement true.