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Advanced Building Physics, A.Y. 2015/16 Prof. L. Pagliano Mid‐course Exam 2015/11/25: Exercises Surname....................................Name.…..............................Personal number (Matricola)................................. Exercise 1 A heat pump heats a building during the winter. It can be schematized as a Carnot machine that works between the reservoir of the external air at T ext=‐10°C and the reservoir of the internal air maintained at Tint= 22°C. The machine must provide a heat flow H=0.64 kW for each degree of temperature difference between the indoor and outdoor environment. Calculate: 1.1 the electric power absorbed by the heat pump; 1.2 the coefficient of performance of the heat pump. If we use the same machine in summer to cool down the building while keeping the same internal temperature Tint= 22°C, find out: 1.3 the maximum external temperature at which the machine can work, absorbing the same electric power (previously calculated) and considering the same . Exercise 2 In a summer day, a space is to be maintained at 25,5°C and 50% relative humidity through an air conditioning system with recirculation (the external air is before mixed with room air and then cooled, dehumidified and post‐heated). The total cooling load (energy in the form of heat to be removed from the space per unit time to maintain comfort) is 35 kW of which 70% is sensible heat. The external air has a temperature TE= 35°C, a relative humidity φE equal to 55% and a mass flow rate equal to 1891,5 kgd.a./h. The inlet temperature is TI= 14,5°C. Drawing the process on the psychrometric diagram attached, define: 2.1 the sensible heat ratio; 2.2 the inlet air flow rate and relative humidity; 2.3 the heat removed during the cooling and dehumidification.