A solar updraft tower is a large chimney which ventilates heated air from the area surrounding it. This air has been subject to heating from the sun during the daytime, and is maintained above ambient temperature during darkness by thermal storage. Assume that the pressure at the base of the tower is 100 kPa and the pressure at the top is 95 kPa. Assume that the air entering the base of the tower starts at 30 degrees C and is warmed 20 degrees C (at constant pressure) before rising in the chimney. Assume that all vertical motion in this device is isentropic, with constant specific heat. In analyzing this system, we'll agree to ignore any explicit mention of kinetic energy variations.
a) Draw a T-s diagram of the cycle described here, with labels for the base and top of the chimney, for the air entering the heated area, and for the location at the height of the top of the chimney for which the heat rejection has occurred.
b) Determine the thermal efficiency of this device, assuming an idealized analysis as described above. As implied above, you may ignore any possible explicit mention of any kinetic energy effects.