Mr Khan

HES 2330 Thermodynamics 1 Semester 1 – 2013 ASSIGNMENT 2 Due Date: 29 May 2013, 5.00 PM Dropbox: Mailbox 83 (HES2330/HES4330) – Level 8, ATC Building 1. A container filled with 45 kg of liquid water at 95oC is placed in a 90-m3 room that is initially at 12oC. The thermal equilibrium is established after a while as a result of heat transfer between the water and the air in the room. Using constant specific heats, determine (a) the final equilibrium temperature, (b) the amount of heat transfer between the water and the air in the room, and (c) the entropy generation. Assume the room is well sealed and heavily insulated. 2. An ideal Otto cycle has a compression ratio of 9.2 and uses air as the working fluid. At the beginning of the compression process, air is at 98 kPa and 27oC. The pressure is doubled during the constant-volume heat-addition process. Accounting for the variation of specific heats with temperature, determine (a) the amount of heat transferred to the air, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle. 3. A gas turbine power plant uses solar energy as the source of heat addition (see Figure for detailed setup and operating data). Modelling the cycle as a Brayton cycle and assuming no pressure drops in the heat exchanger or interconnecting piping, determine: (a) the thermal efficiency; (b) the air mass flow rate, in kg/s, for a net power output of 500kW.

4. Steam is the working fluid in an ideal reheat Rankine cycle. Steam enters the first-stage turbine at 8.0 MPa, 480oC, and expands to 0.7 MPa. It is then reheated to 440oC before entering the secondstage turbine, where it expands to the condenser pressure of 0.008 MPa. The net power output is 100 MW. Determine (a) the thermal efficiency of the cycle, (b) the mass flow rate of steam, in kg/h, (c) the rate of heat transfer out from the condensing steam as it passes through the condenser, in MW. Discuss the effects of reheat on the vapor power cycle.

NOTE:
Do the problems in a systematic way. Include the units in the calculations. State any assumptions.