# Are flow work and work done during isobaric expansion similar?

• Mohankpvk
In summary: I took the equation in the photograph from "The fundamentals of thermodynamics" by Moran et. al. I have marked the flow work and the kinetic energy terms.My doubt is that if work done in moving the fluid will be stored as kinetic energy of the fluid then why K.E. and flow work are considered as two different terms?The flow work represents the work required to push the fluid into and out of the control volume. This contributes to the changes in kinetic energy (as well as to other forms of energy included in the equation). Kinetic energy is not the only form of energy contained in the equation. There is also internal energy (of the fluid) and potential energy. In this open system form of the
Mohankpvk
In case of isobaric expansion, the system expands at constant pressure(the external pressure i.e. the resistance is constant.).In case of flow work, the fluid trying to exit the control volume, pushes against the pressure at the exit of the control volume or when entering the control volume, the surrounding pushes the fluid against the pressure at the inlet.Are these similar?

Mohankpvk said:
In case of isobaric expansion, the system expands at constant pressure(the external pressure i.e. the resistance is constant.).In case of flow work, the fluid trying to exit the control volume, pushes against the pressure at the exit of the control volume or when entering the control volume, the surrounding pushes the fluid against the pressure at the inlet.Are these similar?
I don't see the analogy, since, in the open system case, the inlet and outlet pressures are not necessarily the same.

Mohankpvk
Chestermiller said:
I don't see the analogy, since, in the open system case, the inlet and outlet pressures are not necessarily the same.
Ok.I just have another doubt. As per work energy principle, the energy spent in moving an object is stored as kinetic energy.Flow work is done to make the fluid move.In Bernouli's equation, why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered seperately?

Mohankpvk said:
Ok.I just have another doubt. As per work energy principle, the energy spent in moving an object is stored as kinetic energy.Flow work is done to make the fluid move.In Bernouli's equation, why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered seperately?
I don't understand what your asking. Can you write down an equation and identify the specific terms you are referring to?

Chestermiller said:
I don't understand what your asking. Can you write down an equation and identify the specific terms you are referring to?
I took the equation in the photograph from "The fundamentals of thermodynamics" by Moran et. al. I have marked the flow work and the kinetic energy terms.My doubt is that if work done in moving the fluid will be stored as kinetic energy of the fluid then why K.E. and flow work are considered as two different terms?

#### Attachments

• IMG_20180615_224618.jpg
39.3 KB · Views: 357
The flow work represents the work required to push the fluid into and out of the control volume. This contributes to the changes in kinetic energy (as well as to other forms of energy included in the equation). Kinetic energy is not the only form of energy contained in the equation. There is also internal energy (of the fluid) and potential energy. In this open system form of the first law of thermodynamics, the next step is to lump the pv terms together with the internal energy entering and exiting to obtain the enthalpy of the flowing fluid entering and leaving.

## 1. Are flow work and work done during isobaric expansion the same thing?

No, flow work and work done during isobaric expansion are not the same thing. Flow work is the work required to move a fluid from one point to another, while work done during isobaric expansion is the work done by a gas when it expands at a constant pressure.

## 2. How are flow work and work done during isobaric expansion different?

Flow work and work done during isobaric expansion are different in terms of their definitions and applications. Flow work is often associated with fluid mechanics, while work done during isobaric expansion is a concept used in thermodynamics.

## 3. Is the formula for calculating flow work the same as the formula for work done during isobaric expansion?

No, the formulas for calculating flow work and work done during isobaric expansion are different. Flow work is calculated using the equation W = PV, while work done during isobaric expansion is calculated using the equation W = PΔV.

## 4. Can flow work and work done during isobaric expansion be equal in certain situations?

Yes, flow work and work done during isobaric expansion can be equal in certain situations. This can happen when the fluid being moved is also undergoing an isobaric expansion, or when the pressure remains constant during the fluid's movement.

## 5. How are flow work and work done during isobaric expansion related?

Flow work and work done during isobaric expansion are related in that they both involve the movement or expansion of a fluid. However, they are distinct concepts with different applications and calculations.

• Mechanics
Replies
4
Views
870
• Thermodynamics
Replies
81
Views
3K
• Mechanics
Replies
9
Views
1K
• Thermodynamics
Replies
8
Views
696
• Mechanics
Replies
8
Views
4K
• Mechanics
Replies
1
Views
938
• Mechanics
Replies
14
Views
5K
• Mechanics
Replies
21
Views
18K
• Mechanics
Replies
15
Views
2K
• Mechanics
Replies
4
Views
4K