Question

A 1.5 kg of wet steam at a pressure of 5 bar (hf = 640 kJ/kg, hfg = 2109 kJ/kg) dryness 0.95 is blown into 70 liters of water 12°C (h = 50.4 kJ/kg). Find the final enthalpy of the mixture.

Options:
Option 1: 74.80 kJ/kg
Option 2: 84.80 kJ/kg
Option 3: 94.80 kJ/kg
Option 4: 104.80 kJ/kg

Answer 1

To find the final enthalpy of the mixture, calculate the mass of water and steam in the mixture, then use the formula Enthalpy of mixture = (Mass of steam x Enthalpy of steam) + (Mass of water x Enthalpy of water). The final enthalpy of the mixture is 4470.48 kJ/kg.

Step-by-step explanation:

To find the final enthalpy of the mixture, we need to calculate the mass of water and steam in the mixture. We can start by finding the mass of the steam using the formula:

Mass of steam = Dryness x Mass of wet steam

Mass of steam = 0.95 x 1.5 kg = 1.425 kg

Next, we can calculate the mass of water using the formula:

Mass of water = Volume of water x Density of water

Mass of water = 70 liters x 1000 g/liter = 70000 g = 70 kg

Now, we can find the enthalpy of the mixture using the formula:

Enthalpy of mixture = (Mass of steam x Enthalpy of steam) + (Mass of water x Enthalpy of water)

Enthalpy of mixture = (1.425 kg x (hf + hfg)) + (70 kg x h)

Enthalpy of mixture = (1.425 kg x (640 + 2109)) + (70 kg x 50.4)

Enthalpy of mixture = 942.48 kJ + 3528 kJ = 4470.48 kJ

Therefore, the final enthalpy of the mixture is 4470.48 kJ/kg.