In a 3x3m square flat horizontal solar collector the outside of the glass cover of the collector is at 40 c and the ambient air is at 10 c with wind parallel to the surface of the collector at velocity of 10m/s. find: a. the rate of heat loss by convection from the glass b. the friction coefficient, cf on the glass c. if the wind dies down find the rate of heat transfer from the glass assuming its outside temperature remains the same.

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)?