A heat exchanger is located on the roof of a warehouse to heat the air in winter. It is a coil-shaped pipe into which water vapor enters at 0.1 MPa and 300 C and leaves with a quality of 30%. The warehouse has the following dimensions: 80m x 160m x 10m. The air must be heated from 5C to 22C. What must be the mass flow rate of the water to heat the air in less than half an hour? We want to cool the steam from the exchanger outlet and bring it up to 50 C. For this, a mixing chamber with water at 20 C is used, what will be the proportion of the mixture of steam? The exchanger is damaged and only liquid water can be used at the same pressure (inlet T. 1 C below saturation and outlet T. at 30C). How long does it take to heat the air with the same flow of water?