Q. A piston-cylinder device initially contains 60L of water at30 o C and 300 kPa

Question

Q. A piston-cylinder device initially contains 60L of water at30oC and 300 kPa (State 1). Heat is added to the waterat constant pressure untill its temperature reaches300oC (State 2). a) Determine the mass of water, in kg b) What is the temperature at State 2? in oC Please answer as soon as possible. Thank you ~ Q. A piston-cylinder device initially contains 60L of water at30oC and 300 kPa (State 1). Heat is added to the waterat constant pressure untill its temperature reaches300oC (State 2). a) Determine the mass of water, in kg b) What is the temperature at State 2? in oC Please answer as soon as possible. Thank you ~

Explanation / Answer

Answer: a) State 1 is at 30C and 300kpa. Saturation temperature at 300kpais 133.5C so we know that state 1 is liquid water (similarlysaturation pressure at 30C is 4.25kpa which is much less that 300kpa.), or more specifically it is a compressed liquid. Density of a compressed liquid which is incompressible (ie. water)is approximately equal to the saturation density of the liquid.This just means that when you compress a liquid such as water thedensity does not change by a noticeable amount. (note: This resultcan also be extended to include enthalpy. A compressed liquidundergoes no noticable volume change so h of a compressed liquid isapproximately the same as h for the corresponding saturatedliquid). Anyways, back to the problem, density is approximately 995.6 kg/m3.So: (995.6 kg/m3)*(1 m3/1000 L)*60L = 59.7kg    

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