Question: a glass roof panel of dimensions in an attic room...
A glass roof panel of dimensions in an attic room
transmits 82% of the incident visible sunlight which accounts for
about 41% of solar energy and is opaque infrared light on a sunny
day when the incident solar energy is 330 W/m^2 , a person with a
basal metabolic rate of 83W is working in the room on a computer
that is using 58W. Heat is lost at the rate of 38W through the
floor walls and ceiling as well as via ventilated air at
(i) draw a sketch of the attic room and identify the floor , walls and ceiling as a thermodynamic system boundary. Include the energy transfers across the system boundary on your sketch.
(ii) Use first law of thermodynamics to relate work supplied , heat transfers and energy associated with mass flow.
(iii) calculate the net ventilation rate required in litres/second, of the temperature is to remain constant in the room , assuming the air has a density of 1.2 kg/m^3 .