Un colector solar aprovecha la radiación que le llega para calentar en 2 horas 20 litros de agua desde 20 a 50 oC. Sabiendo que el calor específico del agua es 1 cal/g·oC, halla la superficie de la placa si se sabe que le llegan 100 W/m2 y que el rendimiento es del 85%.

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]