Problem Statement 8 kg of refrigerant R-134a with quality equal to 0.70 is contained in a...

Transcribed Image Text:

Problem Statement 8 kg of refrigerant R-134a with quality equal to 0.70 is contained in a piston cylinder device that is thermally insulated and has an embedded heating element, see figure below. Initially, the spring is not deformed but touching the piston, and the temperature of the refrigerant is T = 30C. The cross-sectional area of the piston is 0.4 m. The elastic constant for the spring is equal to k = 136.9 kN/m and the local atmospheric pressure is 100 kPa. Next, heat is applied in a controlled manner until the volume occupied by the refrigerant becomes equal to two times the original volume. Please answer the following questions. Note: To receive credit (or partial credit), in your solution you need to show a schematic of your system, with a boundary and energy interaction across the boundary, your assumptions, and a process sketch. Your equations need to be expressed in literal form first, with their corresponding subscripts when applicable, before starting any computation. Values retrieved from tables need to include units along with the table number used. R-134a Qin A. (35 points) Determine the heat that needs to be supplied to move the piston to the new volume, in kJ. In your solution you need to show a schematic of your system, with a boundary and energy interaction across the boundary, your assumptions, and a process sketch. B. (15 points) When the heat ceases to act, a leak develops, and R-134a starts escaping. Next, the leak is fixed; at that instant 2 kg of R-134a had escaped and the pressure of the refrigerant in the cylinder is such that the spring just ceases being deformed. Represent the processes on a P-v diagram (Pressure-specific volume). On the axes, include the values for pressure in kPa and specific volume in m/kg, for the process related to the heating (1-2) and then for when the refrigerant escapes (2-3). Problem Statement 8 kg of refrigerant R-134a with quality equal to 0.70 is contained in a piston cylinder device that is thermally insulated and has an embedded heating element, see figure below. Initially, the spring is not deformed but touching the piston, and the temperature of the refrigerant is T = 30C. The cross-sectional area of the piston is 0.4 m. The elastic constant for the spring is equal to k = 136.9 kN/m and the local atmospheric pressure is 100 kPa. Next, heat is applied in a controlled manner until the volume occupied by the refrigerant becomes equal to two times the original volume. Please answer the following questions. Note: To receive credit (or partial credit), in your solution you need to show a schematic of your system, with a boundary and energy interaction across the boundary, your assumptions, and a process sketch. Your equations need to be expressed in literal form first, with their corresponding subscripts when applicable, before starting any computation. Values retrieved from tables need to include units along with the table number used. R-134a Qin A. (35 points) Determine the heat that needs to be supplied to move the piston to the new volume, in kJ. In your solution you need to show a schematic of your system, with a boundary and energy interaction across the boundary, your assumptions, and a process sketch. B. (15 points) When the heat ceases to act, a leak develops, and R-134a starts escaping. Next, the leak is fixed; at that instant 2 kg of R-134a had escaped and the pressure of the refrigerant in the cylinder is such that the spring just ceases being deformed. Represent the processes on a P-v diagram (Pressure-specific volume). On the axes, include the values for pressure in kPa and specific volume in m/kg, for the process related to the heating (1-2) and then for when the refrigerant escapes (2-3).