Standards for firewalls may be based on their thermal response to a prescribed radiant heat flux. consider a 0.25-m-thick concrete wall (rho= 2300 kg/m3, c= 880 j/kg·k, k= 1.4 w/m·k), which is at an initial temperature of ti= 25°c and irradiated at one surface by lamps that provide a uniform heat flux of qs′′= 0.85·104 w/m2. the absorptivity of the surface to the irradiation is αs= 1.0. if building code requirements dictate that the temperatures of the irradiated and back surfaces must not exceed 325°c and 25°c, respectively, after 30 min of heating, will the requirements b

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)?