A piston-cylinder device initially contains 2 kg of refrigerant-134a at 100 kPa and 20°C. Heat is now transferred to the refrigerant from a source at 150°C, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 120 kPa. Heat transfer continues until the temperature reaches 80°C. Assume the surroundings to be at 25°C and 100 kPa. R-134a 100 kPa 20°C Q 150°C Problem 08.048.c - Exergy Destroyed by Piston Device with Refrigerant Determine the exergy destroyed. (You must provide an answer before moving on to the next part.) The exergy destroyed is [ kJ.

3 A 40-L electrical radiator containing heating oil is placed in a 50-m³ room. Both the room and the oil in the radiator are initially at 10°C. The radiator with a rating of 2.4 kW is now turned on. At the same time, heat is lost from the room at an average rate of 0.35 kJ/s. After some time, the average temperature is measured to be 20°C for the air in the room, and 50°C for the oil in the radiator. Taking the density and the specific heat of the oil to be 950 kg/m3 and 2.2 kJ/kg-°C, respectively, determine how long the heater is kept on. Assume the room is well sealed so that there are no air leaks. The gas constant of air is R = 0.287 kPa-m³/kg-K (Table A-1). Also, c = 0.718 kJ/kg-K for air at room temperature (Table A-2). Oil properties are given to be p = 950 kg/m³ and Cp = 2.2 kJ/kg.°C. 3 10°C Room Radiator The heater is kept on for Q min. 4

5-62 Refrigerant-134a is throttled from the saturated liquid state at 700 kPa to a pressure of 160 kPa. Determine the tem- perature drop during this process and the final specific vol- ume of the refrigerant. Answers: 42.3°C, 0.0345 m³/kg P₁ = 700 kPa sat. liquid R-134a P₂ = 160 kPa FIGURE P5-62

Air in a closed-piston cylinder is initially at 100 kPa and 27°C. It is then compressed until the pressure reaches 2 MPa in a polytropic process with n = 1.3. Determine how much boundary work in kJ/kg must be supplied into the system to make this process possible. Round your answer to the nearest whole number.

A piston–cylinder device contains 5 kg of steam at 1008C with a quality of 50 percent. This steam undergoes two processes as follows: 1-2 Heat is transferred to the steam in a reversible manner while the temperature is held constant until the steam exists as a saturated vapor. 2-3 The steam expands in an adiabatic, reversible process until the pressure is 15 kPa. (a) Sketch these processes with respect to the saturation lines on a single T-s diagram. (b) Determine the heat transferred to the steam in process 1-2, in kJ. (c) Determine the work done by the steam in process 2-3, in kJ.