Question

21.3 A restaurant seats 150 people and allows smoking. Estimate
the required ventilation rate (make-up air only) for this restaurant.
The restaurant changes hands and the new owner decides
to switch to nonsmoking. What is the new flow rate of make-up
air required? Assume that the guidelines call for 12.5 cfmpp for
smoking, and 7.5 cfmpp for nonsmoking.
21.4 If the estimated system pressure drop is 3.5 inches of water for
the restaurant of Problem 21.3, estimate the weekly monetary
savings realized by this restaurant due to switching to nonsmoking.
Base your estimate on the reduced airflow volume
alone (not counting air conditioning costs). Assume the restaurant
operates from 9:00AM to 11:00 PM, 7 days a week, and that
electricity costs 10 cents/kWh.

Answer 1

Ans) Number of people = 150

For smoking person ,rate = 12.5 cfmpp

For 150 person , rate = 12.5 x 150 = 1875 cfm

Ans) For non smoking person, rate = 7.5 cfm

Operating time of restaurant = 14 hrs

Ventilation of smoking = 1875 cfm

Ventilation for non smoking =7.5 x 150 = 1125 cfm

Savings per day if switched to non smoking = 750 cfm  

Saving per week = 750 x 7 = 5250 cfm

Power saved per week(P)= gQH

= 0.00237 x 32.2 x 5250 x (3.5/12)

= 116.85 W

Energy saved = 116.85 x 3600

= 420.68 kWh

Amount saved per week = 420.68 x 10 = 4206.8 cents

= 42.068 $ per week