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Q6. An insulated, vertical piston-cylinder device initially contains 10 kg of water, 6 kg of which is in the vapor phase. Initially the pressure is 200 kPa Inside the cylinder. A linear spring is connected to the piston therefore the pressure changes linearly with volume (P=m. V + b). Super heated steam at 0.5 MPa and constant temperature is allowed to enter the cylinder from a supply line until all the liquid in the cylinder has just vaporized and the pressure and volume in the cylinder have both doubled. For this problem you must use property tables (from the textbook). Determine the specific enthalpy (in kJ/kg) of the steam entering the cylinder.
Q8. A heat pump with refrigerant-134a (R-134a) as the working fluid is used to keep a space at 25 °C by absorbing heat from geothermal water that enters the evaporator at Tiwater - 63 °C at a rate of 0.063 kg/s and leaves at Towater - 41 °C. The specific heat of liquid water is 4.18 kJ/(kg-K). Refrigerant enters the evaporator at TR-134a - 10 °C with a quality of x - 13 % and leaves at the same pressure as saturated R-134a vapor at the same temperature. The compressor consumes 1.5 kW of power. For this problem you must use property tables (from the textbook). Determine the rate of heat (in kW) supplied to the space.