A well insulated piston-cylinder system contains 5 liter of saturated liquid water. The piston has a diameter and mass of 0.30 m and 15 kg respectively. The system is placed at an area where the atmospheric pressure is at 86 kPa. The water is stirred by a paddle wheel while a current of 10A flows for 45 min through a resistor placed in the water. (a) Determine the initial pressure of the water (b) Determine the initial mass of the water in the cylinder. (c) If one -half of the liquid is evaporated during this constant-pressure process and the paddle-wheel work amounts to 300 kJ, determine the voltage of the source. (d)Determine the final volume of the water

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Question: A well insulated piston-cylinder system contains 5 liter of saturated liquid water. The piston has a diameter and mass of 0.30 m and 15 kg respectively. The system is placed at an area where the atmospheric pressure is at 86 kPa. The water is stirred by a paddle wheel while a current of 10A flows for 45 min through a resistor placed in the water. (a) Determine the initial pressure of the water (b) Determine the initial mass of the water in the cylinder. (c) If one -half of the liquid is evaporated during this constant-pressure process and the paddle-wheel work amounts to 300 kJ, determine the voltage of the source. (d)Determine the final volume of the water.

Answer:

Given data: 

The initial volume , The atmospheric pressure and mass of the piston .

(a) Initial pressure




(b) From property table of water, specific volume of saturated water at 88.082 kPa is,

and therefore mass of the water is,



(c) Quality or dryness fraction (x) = 0.5 and from property table of water at    ,

Specific internal energy  

Here, work done on system   and according to the first law of the thermodynamics,



Thus, the required voltage (V) = 175.818 watt.

(d) Specific volume at x = 0.5 and P =88.802 kPa is,
and thus, final volume is,

 

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