How Does the Steady Flow Energy Equation Account for Heat Transfer?

So the equation is essentially stating that the total energy on one side (left) is equal to the total energy on the other side (right), where total energy includes internal energy (U), kinetic energy (K), potential energy (P), and enthalpy (H). Thus, if heat is added (Qin), it will contribute to the total energy on the left side, while work output (Wout) will contribute to the total energy on the right side. The heat added (Qin) will become internal energy (U) in the system, as it is assumed that there is no heat transfer to the surroundings. Therefore, we do not need to include Q on both sides of the equation, as long as we account for the
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akip
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Right, I'm sure this is bread and butter to a lot of you but I have just been introduced to the SFEE.
mgz+0.5mC^2+H +Q = mgz + 0.5mC^2 +H+W

Where Q is the heat transfer, W is work done and H is enthalpy. Where is it assumed that the heat energy is in the energy balance? If heat is added where is this balanced out on the other side of the equation?
Does the heat become internal energy?

Basically I'm asking why we don't have Q on both sides?

Kip.
 
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  • #2
Here is a nicely worded explanation:

http://personalpages.manchester.ac.uk/staff/john.chinn/Thermo1/SFEE1.pdf
 
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  • #3
The Q in the equation is the NET heat transfer into the system (control volume). If you wish, you can represent it differently as Q = Qnet = Qin-Qout, and then rearrange so that Qin is on one side of the equation, and Qout is on the other.

Similarly, the W is the NET work output from the system (control volume) and can be represented as W = Wnet = Wout-Win.
 
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1. What is the Steady Flow Energy Equation?

The Steady Flow Energy Equation is a fundamental principle in thermodynamics that describes the conservation of energy in a fluid flow system. It states that the total energy of a fluid at any point in a system remains constant as long as there is no external work or heat transfer.

2. How is the Steady Flow Energy Equation derived?

The Steady Flow Energy Equation is derived from the First Law of Thermodynamics, which states that energy cannot be created or destroyed, only transferred or converted. By applying this law to a steady flow system, we can equate the total energy entering the system to the total energy exiting the system, thus deriving the Steady Flow Energy Equation.

3. What are the components of the Steady Flow Energy Equation?

The Steady Flow Energy Equation consists of four main components: kinetic energy, potential energy, internal energy, and flow work. These components represent the different forms of energy present in a fluid flow system and are used to calculate the total energy at any point in the system.

4. How is the Steady Flow Energy Equation used in practical applications?

The Steady Flow Energy Equation is used in a variety of practical applications, such as analyzing the performance of pumps, turbines, and compressors. It is also used in the design of heat exchangers and other energy conversion systems. By applying the equation, engineers can optimize the efficiency and performance of these systems.

5. What are the limitations of the Steady Flow Energy Equation?

While the Steady Flow Energy Equation is a useful tool for analyzing fluid flow systems, it does have some limitations. It assumes that the flow is steady, meaning that the properties of the fluid do not change over time. It also neglects any external heat transfer or work, which may not always be the case in real-world applications. Additionally, it does not account for changes in fluid density or any irreversibilities in the system.

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