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**Question 1:**

A gas is contained in a 0.8 m³ rigid tank. The gas receives a paddle work of 5.25 W for 30 minutes. At the initial state, the density of the gas is 1.80 kg/m³. Determine the change in specific internal energy in kJ/kg.

**Question 2:**

1.8 kg/s of steam expands in a turbine, producing 560 kW of power output. The steam enters at a velocity of 12 m/s and exits at 60 m/s. The reduction of specific enthalpy is 435 kJ/kg. Determine the heat flow per second when the inlet of the turbine is located 900 mm above the outlet.

Answer :

Final answer:

The change in specific internal energy of the gas is approximately 3.6458 kJ/kg.

Explanation:

To calculate the change in specific internal energy, we need to use the equation: Δu = W/m.

Given:

  • Volume of the tank (V) = 0.8 m³
  • Work done on the gas (W) = 5.25 W
  • Time (t) = 30 minutes = 30 × 60 seconds = 1800 seconds
  • Density of the gas (ρ) = 1.80 kg/m³

First, we need to calculate the mass of the gas using the formula: m = ρV.

Substituting the given values, we have:

m = 1.80 kg/m³ × 0.8 m³ = 1.44 kg

Next, we can calculate the change in specific internal energy using the formula: Δu = W/m.

Substituting the given values, we have:

Δu = 5.25 W / 1.44 kg = 3.6458 kJ/kg

Therefore, the change in specific internal energy of the gas is approximately 3.6458 kJ/kg.

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