Exercise 1 (max. 5 p) Study the dynamic behavior of an empty, windowless storage room with heavy and light- weight structures. The width of the room is 4 m, length 5 m and height 3 m. The room is adjacent to outdoor air from all directions and is initially at a steady-state temperature of T = To = 21C. The U-value of the walls, floor and roof is 0.35 W/mK. The air-change rate is 0.5 1/h. A sudden heat wave elevates the outdoor temperature from 21C to 30C. Calculate the room temperature after 24 hours (starting from 21C with no cooling and starting from 30C, when the room is exposed to constant cooling power of 400 W) for the following cases: a) Heavy structures, concrete (c=800 J/kgK, p=2300 kg/m), active thickness 8 cm b) Lightweight structures, board (cp= 2400 J/kgK, p= 500 kg/m), active thickness 2 cm Apply the one-time-constant model in both cases. Exercise 2 (max. 5 p) An office room is at steady-state temperature of T = T = To = 28C. A cooling power of 1000 W is supplied into the room. What is the temperature of the air and the walls after 2 hours in cases a) and b)? a) The cooling power is totally convective. b) The cooling power is shared evenly with a convective (50%) and a radiative (50%) component. Solve the problem using the two-time-constant model and Euler's discretization method. The width, length and height of the room are 4 m, 5 m and 3 m, respectively. There is a 3 m window (U = 1.8 W/Km) installed on the external wall of the room. The U-value of the walls is 0.25 W/Km. The convective heat transfer coefficient is 3 W/mK. The air- change rate is 0.5 1/h. The active heat capacity of the outer walls is 5888 kJ/K. Choose the time step so that there will not be any oscillation in the solution. All the structures can be assumed to be adjacent to the outdoor air