Introduction:
To make the steam dry saturated, we need to supply heat at constant pressure. In this scenario, we are given one kilogram of steam at a pressure of 2 bar with a dryness fraction of 0.8. We need to calculate the amount of heat that needs to be supplied to make the steam dry saturated.

Understanding the problem:
To solve this problem, we need to understand the concept of dryness fraction. Dryness fraction is the ratio of the mass of dry steam to the total mass of steam. It represents the quality of steam, where 0 indicates completely wet steam and 1 indicates completely dry saturated steam.

Calculating the mass:
The given steam has a dryness fraction of 0.8, which means 80% of the steam is in the vapor phase and 20% is in the liquid phase. Therefore, the mass of dry steam (md) is calculated as follows:

md = dryness fraction * total mass of steam
md = 0.8 * 1 kg
md = 0.8 kg

Calculating the mass of liquid:
The mass of liquid (ml) can be calculated as the difference between the total mass of steam and the mass of dry steam:

ml = total mass of steam - mass of dry steam
ml = 1 kg - 0.8 kg
ml = 0.2 kg

Determining the heat required:
To convert the wet steam to dry saturated steam, we need to supply heat to evaporate the liquid phase. The heat required is given by:

Q = ml * Lv

Where Lv is the latent heat of vaporization.

Conclusion:
In this problem, we were given one kilogram of steam at 2 bar pressure with a dryness fraction of 0.8. By calculating the mass of dry steam and the mass of liquid, we determined that the mass of dry steam is 0.8 kg and the mass of liquid is 0.2 kg. To make the steam dry saturated, we need to supply heat equal to the mass of liquid multiplied by the latent heat of vaporization.