# Thermodynamics - First Law (T-fitting)

• kaeser1
In summary, the conversation is about a problem with determining the velocity of air at the outlet and the rate of change of flow energy across a T-fitting in a compressed air line. The air enters the fitting at 1.6 MPa and 40 deg C with a velocity of 50 m/s, and exits at 1.4 MPa and 36 deg C. The first law of thermodynamics is suggested as a method to solve the problem. The unknown variables and the importance of delta h are mentioned.
kaeser1
Hey guys, I am having a problem trying to figure out what this question is asking for:

The air flow in a compressed air line is divided into two equal streams by a T-fitting in the line. The compressed air enters the 2.5cm diameter fitting at 1.6 MPa and 40 deg C with a velocity of 50 m/s. Each outlet has the same diameter as the inlet and the air at these outlets have a pressure of 1.4 MPa and temperature of 36 deg C. Determine the velocity of the air at the outlet and the rate of change of flow energy across the T-fitting.

I was able to figure out the velocities at the outlets but did not understand the rate of change of flow energy. If somebody could help me out, it would be great.

The problem obviously says first law, I believe you did not use the first law to find the velocities yeah? So try applying the first law. What variables are unknown? What is delta h?

Hello,

It seems like the question is asking for the application of the First Law of Thermodynamics in the context of a T-fitting in a compressed air line. The First Law states that energy cannot be created or destroyed, only transferred or converted from one form to another. In this case, the compressed air is entering the T-fitting with a certain amount of energy and is being divided into two streams, each with a different pressure and temperature.

To calculate the rate of change of flow energy across the T-fitting, you will need to use the equation for the First Law of Thermodynamics:

ΔE = Q - W

Where ΔE is the change in energy, Q is the heat transferred, and W is the work done. In this case, we can assume that there is no heat transfer (Q=0) and the work done is negligible. Therefore, the change in energy (ΔE) is equal to the change in flow energy.

To calculate the change in flow energy, you will need to use the equation:

ΔE = ΔU + ΔKE + ΔPE

Where ΔU is the change in internal energy, ΔKE is the change in kinetic energy, and ΔPE is the change in potential energy.

Since there is no change in height, we can assume that ΔPE = 0. Also, since the air is an ideal gas, we can assume that there is no change in internal energy (ΔU = 0). Therefore, the change in flow energy is equal to the change in kinetic energy (ΔKE).

To calculate the change in kinetic energy, you will need to use the equation:

ΔKE = ½ m (Vf² - Vi²)

Where m is the mass of the air, Vf is the final velocity, and Vi is the initial velocity.

Using this equation, you can calculate the change in kinetic energy for each outlet, and then add them together to find the total change in flow energy. This will give you the rate of change of flow energy across the T-fitting.

I hope this helps clarify the question and how to approach it. Let me know if you have any further questions. Good luck!

## 1. What is the First Law of Thermodynamics?

The First Law of Thermodynamics is a fundamental principle in physics that states that energy cannot be created or destroyed, only transferred or converted from one form to another. In other words, the total energy of a closed system remains constant.

## 2. How does the First Law of Thermodynamics apply to T-fittings?

In a T-fitting, the First Law of Thermodynamics can be applied to the flow of fluids. The law states that the total energy of the fluid entering the T-fitting must equal the total energy of the fluid leaving the fitting. This allows for the conservation of energy in the system.

## 3. What is the significance of T-fittings in thermodynamics?

T-fittings are commonly used in thermodynamics experiments and systems to study the flow of fluids and the transfer of energy. They allow for the measurement of pressure, temperature, and flow rate in various parts of the system, which can help in understanding and analyzing the behavior of the system.

## 4. What are some practical applications of the First Law of Thermodynamics in T-fittings?

The First Law of Thermodynamics in T-fittings is used in various industrial and engineering applications, such as in heat exchangers, refrigeration systems, and power plants. It helps in designing and optimizing these systems to ensure efficient energy transfer and conservation.

## 5. Can the First Law of Thermodynamics be violated in T-fittings?

No, the First Law of Thermodynamics is a fundamental law of physics and cannot be violated. It applies to all thermodynamic systems, including T-fittings, and must be satisfied in all cases.

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