>> Civil Engineering
For each of the following problems, answer the following questions. (You do not need to actually solve the problems.)
(i) What control volume would you use to solve the problem?
(ii) Are conditions or concentrations in the problem changing with time?
(iii) Is the problem steady state or non-steady state, and why?
(iv) Is the chemical being produced or destroyed by chem-ical reaction within the control volume, or not?
(v) Is the chemical conser-vative or nonconservative, and why?
(a) An accident has resulted in the release of a pollutant inside a chemical manufacturing plant. The spill released the pollutant into a lake near the chemical plant. The lake flows into a small stream. How long would it take the pollutant, which is inert, to reach a safe level in the lake and in the stream leaving the lake?
(b) Carbon dioxide (CO2) emissions from fossil-fuel burning are mixed throughout the atmosphere. Assume that these emissions are mixed immediately throughout the entire atmosphere, and that CO2 does not degrade chemically. If the total emission rate of carbon dioxide and the volume of the atmosphere is known, what would be the rate of increase of atmospheric carbon dioxide levels in ppm yr-1?
(c) An air freshener emits perfume into a room at a constant rate. The perfume is mixed throughout the room and diluted by the room ventilation flow, which brings fresh air into the room at a flow rate Q. What is the resulting concentration of perfume in the room? (Note that the first-order decay rate constant of the perfume in the room?(Note that the first order decay rate constant of the perfume is very slow relative to the amount of time it takes to mix fresh air through the room.)