Thermodynamics: Unsteady Flow (Charging) Process

In summary, the conversation is about determining the temperature at point two when the valve is closed. The person asking for help does not have enough information and is asking for assistance. The other person suggests finding u_2 through interpolation and clarifies the mass of saturated mixture and quality. They also mention that T_2 may be larger than the saturated temperature and offer to send slides for reference.
  • #1
afpskierx
6
0
Please see the attached photo.

I am not sure how to proceed. I do not know Mi or M2, nor do I have enough information to determine the temperature at point two (when the valve is closed). Any help getting me going along will be much appreciated. :)
 

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  • #2
Hi afpskierx,

Have you find the [itex]u_2[/itex] by doing interpolation? I got the answer for [itex]u_2[/itex] = 3047.35 kJ/kg

At state 1, I don't quite understand with the question which stated that that mass of saturated mixture of water is 12kg.

So, I assume the quality, x = mass of vapour / total mass. You will get 7.2kg for your mass of vapour.

At state 2 (which is the [itex]P_2[/itex] = 400kPa and [itex]T_2[/itex] = 450 C) I assume it SUPERHEATED VAPOUR seems the [itex]T_2[/itex] larger than saturated temperature.

I just can help for what I wrote above. Otherwise, I'll try come out for the full solution later.
 
  • #3
What did you use to look up u2? The only thing we know about it is that its quality is one (it is a saturated vapor).
 
  • #4
can you PM me your e-mail address? I'll send to you slides for your reference. Thanks :)
 
  • #5


Thank you for sharing this content on thermodynamics. The process shown in the attached photo is an unsteady flow charging process, which involves the transfer of heat and mass into a closed system. In this process, the valve is initially open, allowing a mass flow rate Mi to enter the system at a temperature T1. As the valve closes, the system undergoes a transient period where the temperature and pressure change until the valve is fully closed and the system reaches a steady state.

To analyze this process, we would need to know the initial and final mass of the system (M1 and M2), as well as the specific heat and other properties of the fluid being charged. Without this information, it is difficult to determine the temperature at point two when the valve is closed. However, we can make some general observations about this process.

First, as the mass enters the system, it will transfer heat to the system, increasing its internal energy and temperature. As the valve closes, the mass flow rate decreases and the system begins to reach a steady state where the heat transfer is balanced by the work done on the system. This results in a decrease in temperature until the valve is fully closed and the system reaches its final temperature.

Second, the final temperature and pressure of the system will depend on the properties of the fluid being charged and the initial and final mass of the system. For example, if the fluid has a high specific heat, it will require more heat transfer to reach a certain temperature, resulting in a slower decrease in temperature during the transient period.

In summary, the unsteady flow charging process shown in the photo is a complex thermodynamic process that requires more information to fully analyze. However, we can make some general observations about how the system will behave based on the principles of thermodynamics. I would recommend gathering more information about the system and the properties of the fluid to accurately analyze this process.
 

1. What is a charging process in thermodynamics?

A charging process in thermodynamics refers to the transfer of energy into a system, typically in the form of heat or work, resulting in an increase in the internal energy of the system. This can occur in various systems, such as a gas turbine engine or a refrigeration cycle, and is an essential concept in understanding the behavior of thermodynamic systems.

2. How is the charging process different from the steady flow process?

The main difference between the charging process and the steady flow process is the time frame in which they occur. In a steady flow process, the system remains in a constant state while energy is continuously transferred in or out, whereas the charging process involves a change in the state of the system over time due to the energy transfer.

3. What is the first law of thermodynamics and how does it apply to unsteady flow processes?

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another. In unsteady flow processes, this law applies by accounting for the energy transfer into or out of the system, as well as any changes in the internal energy of the system due to work or heat transfer.

4. Can the charging process occur in an isolated system?

No, the charging process cannot occur in an isolated system. This is because an isolated system does not exchange energy with its surroundings, so there can be no net energy transfer into or out of the system. The charging process requires an energy transfer to occur, which is not possible in an isolated system.

5. How is the charging process quantified in thermodynamics?

The charging process is quantified by the change in internal energy of the system, which is equal to the sum of the heat transfer into the system and the work done on the system. This change in internal energy is commonly represented by the symbol ΔU and is measured in Joules (J) in the SI unit system.

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