ผศ.ดร.เด่นพงษ์ สุดภักดี
ภาควิชาวิศวกรรมเครื่องกล คณะวิศวกรรมศาสตร์ มหาวิทยาลัยขอนแก่น
[15]
Example
A piston-cylinder device contains 25 g of saturated water vapor that is maintained at a constant pressure of 300 kPa. A resistance heater within the cylinder is turned on and passes a current of 0.2 A for 5 min from a 120-V source. At the same time, a heat loss of 3.7 kJ occurs.
(a)show that for a closed system the boundary work Wb and the change in
internal energy DU in the first-law relation can be combined into one term, DH, for a
constant-pressure process.
(b)Determine the final temperature of the steam.
