HW4-535-F19-text.pdf - ME 535 HW PROBLEM SET 4 F2019 1 A 100 L hot water tank has water at 25oC 200 kPa and it is now heated to become 80oC at a

# HW4-535-F19-text.pdf - ME 535 HW PROBLEM SET 4 F2019 1 A...

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ME 535 HW PROBLEM SET 4, F2019 1 A 100 L hot water tank has water at 25 o C, 200 kPa and it is now heated to become 80 o C at a constant pressure. Find the exergy increase of the water and the total exergy destruction if the heat source is: a) Electricity and b) A heat pump with COP of 2.75 drawing in heat from the ambient. 2 An energy recovery heat exchanger isused to heat water at 15C, 0.4 MPa to saturated vapor. The enrgy comes from 2 kg/s air flow at 800 K which leaves at 360 K both at 1 MPa. Find the changes in exergy of the flows and the overall 2 nd law efficiency of the heat exchanger. Use T o = 15C. 3 A heat engine operating with an evironment at 298 K produces 5 kW of power output with a first law efficiency of 50%. It has a second law efficiency of 80% and T L = 310 K. Find all the energy and exergy transfers in and out. 4 A concentrated solar power plant heats molten salt to 550 C so a counterflow

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