Question

Homework 2 Problem 1: A piston-cylinder device initially contains 0.35-kg steam at 3.5 MPa, superheated by 7.4 C. Now the stream loses heat to the surroundings and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 200C. Determine (a) the final pressure and the quality (if mixture), (b) the boundary work, (c) the amount of heat transfer when the piston first hits the stops, (d) and the total heat transfer. (e) plot process diagram in P-v diagram Problem 2: Steam at 75 kPa and 8 percent quality is contained in a spring-loaded piston-cylinder device, with an initial volume of 2 m3. Stream is now heated until its volume is 5 m3 and its pressure is 225 kPa (a) Determine the state of stream, pressure and temperature, as well as quality if mixture. (b) Determine the heat transferred to and the work produced by the stream during the process. (c) plot process diagram in P-v diagram Problem 3: Steam enters an adiabatic turbine at 15 MPa and 525 C and leaves at 10 kPa with a quality of 0.65. Neglecting the changes in kinetic and potential energies, (a) determine the mass flow rate required for a power output of 6.5 MW. (b) determine the state of stream at inlet and outlet. (c) plot process diagram in P-v diagram Problem 4: In steam power plants, open feed water heaters are frequently utilized to heat the feed water by mixing it with steam bled off the turbine at some intermediate stage. Consider an open feed water heater that operates at a pressure of 1000 kPa Feedwater at 50C and 1000 kPa is to be heated wither superheated steam at 200C and 1000 kPa. In an ideal feedwater heater, the mixture leaves the heater as saturated liquid at the feedwater pressure. Determine the ratio of mass flow rates of the feedwater and the superheated vapor for this case P 1000kPa Problem 5: Refrigerant 134a enters a compressor with a mass flow rate of 5 kg/s and a negligible velocity The refrigerant enters the compressor as a saturated vapor at 10C and leaves the compressor at 1400 kPa with an enthalpy of 281.39 kj/kg and a velocity of 50 m/s. The rate of work done on the refriderant is measured to be 132.4 kW. If the elevation change between the compressor inlet and exit is negligible, determine the rate of heat transfer associated with this process, in kw

Answer 1

ア= 3.5 MPa Tsat@35MPa o oleam ushem Properties oj otearn shen The ziston derauls The perties lop ao 2256 v2 = 0.001235 rm21kg At fmal state 0.001235ooou5+3 C0/26053) χ37 0.0006t. =1554.9 KPR tmaL Pressure ,

Arno Lent heat transfer Uten free尸iston farst hits ha stop -201 3