An air compressor takes in air at standard conditions (use 14.7 psia and 70°f) at a negligible velocity. the air is discharged at 115 psia and 125°f with a den- sity of 0.5 lbm/ft 3. the mass fl ow rate out of the 0.5 ft2 discharge pipe is 12 lbm/s. if the compressor input horsepower is 800, find the magnitude and direction (in words) of the heat transfer to/from the compressor in units of btu/s. assume a steady flow. draw a control surface for the calculation.

On a average work day more than work place firs are reorted

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]

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)?