Asingle-cylinder four-stroke-cycle spark- ignition engine has a bsfc of 0.4 kg/kw-hr and a volumetric efficiency of 78% at a speed of 45 rps. the bore is 6 cm and the stroke is 8.5 cm. what is the fuel flow rate, fuel-air ratio, and brake torque if the brake power output is 6 kw with ambient conditions of 100 kpa and 22°c?

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.