Air flows through a combustion chamber held at 1145k and 101.3 kpa. oxygen diffuses through a 1.5 mm thick stagnant film of air to a flat carbon surface where it reacts instantaneously to form carbon monoxide. no reaction occurs in the gas film. the diffusivity of oxygen in the gas film is 1.30x10-4 m2 /s. what is the rate of oxygen diffusion to the surface?

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)?