Across-flow air-to-water heat exchanger (both fluids unmixed) with an effectiveness of 0.65 is used to heat water (cp 4180 j/kg. k) with hot air (c 1010 j/kg. k). water enters the heat exchanger at 20°c at a rate of 4 kg/s, while air enters at 100 c at a rate of 9 kg/s. if the overall heat transfer coefficient based on the water side is 260 w/m2.k, determine the heat transfer surface area of the heat exchanger.

Asimple speed reducer is composed of 2 spur gears. the pinion gear has a pitch diameter of 0.75" and 36 teeth while the driven gear has a pitch diameter of 4.0" and 192 teeth. a)-what is the diametral pitch of each gear? b)-if an electric motor rotating ccw at 3000 rpm is coupled to the pinion, what is the rotational speed of the driven gear? c)-if the torque delivered to the pinion is 1 n-m, what is the torque on the driven gear? d)-what is the power transmitted by the gear train?