Question

A closed, rigid, 0.6 m³ tank is filled with 7 kg of water. The initial pressure is p=20 bar. The water is cooled until the pressure is p=4 bar. Determine the initial quality, x, and the heat transfer, in kJ

Answer 1

To determine the initial quality, x, and the heat transfer in kJ, we will need to use the formula Q = m [ (h1-hf) + x(hfg)] and solve for x and Q using the given values.

Step-by-step explanation:

To determine the initial quality, x, and the heat transfer in kJ, we will need to use the formula:

Q = m [ (h1-hf) + x(hfg)]

Where:

• Q is the heat transfer
• m is the mass of the water
• h1 is the initial enthalpy
• hf is the enthalpy at the final pressure
• x is the initial quality
• hfg is the enthalpy of vaporization

We can then solve for x and Q using the given values:

Q = 7 kg [ (h1 - hf) + x(2258 kJ/kg) ]

20,000 kJ = 7 kg [ (2782 kJ/kg - hf) + x(2258 kJ/kg) ]

From here, you can solve for x. Once x is found, you can substitute it back into the equation to find Q.