Air Exchange A large room has a volume of 2000 m3 The air in this room contains 0.25% by

Chapter 2, Problem 49

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Air Exchange A large room has a volume of 2000 m3 The air in this room contains 0.25% by volume of carbon dioxide (C02). Starting at 9:00 A.M. fresh air containing 0.04% by volume of C02 is circulated into the room at the rate of 400 m3 / min. Assume that the stale air leaves the room at the same rate as the incoming fresh air and that the stale air and fresh air mix immediately in the room. See FIGURE 2.7.12. (a) If v(t) denotes the volume of C02 in the room at time t, what is v(O)? Find v(t) for t > 0. What is the percentage of C02 in the air of the room at 9:05 A.M? (b) When does the air in the room contain 0.06% by volume of C02? (c) What should be the flow rate of the incoming fresh air if it is required to reduce the level of C02 in the room to 0.08% in 4 minutes? Fresh air -- --> inm3/min 2000m3 Stale - -- ... arr FIGURE 2.7.12 Air exchange in 49