The minimum fresh air requirement of a residential building is specified to be 0.35 air changes per hour (ashrae, standard 62, 1989). that is, 35 percent of the entire air contained in a residence should be replaced by fresh outdoor air every hour. if the ventilation requirement of a 2.7-m-high, 200-m2 residence is to be met entirely by a fan, determine the flow capacity in l/min of the fan that needs to be installed. also determine the minimum diameter of the duct if the average air velocity is not to exceed 5.5 m/s.

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?