Test 21 - Spring 2009 | Thermodynamics | MAE 251, Exams of Thermodynamics

Download Test 21 - Spring 2009 | Thermodynamics | MAE 251 and more Exams Thermodynamics in PDF only on Docsity! MAE251 Test 21 Spring 2009 Closed book – time: 50 min – grading: 10+10 1. An unspecified substance is compressed as shown (1-2), then cooled (2-3) by an incompressible liquid stream (A-B). Neglect stray heat exchanges, and kinetic and potential energy. Steady flow is assumed. Properties marked on the figure are considered known, as is the specific heat of the liquid. Analyze this system to obtain the relations giving the mass flow rate of coolant, the entropy production in the compressor and heat exchanger, and the isentropic efficiency of the compressor, in terms of known properties (identify clearly which properties are used to determine others). No numbers expected. 2. Air (ideal gas, cp = 1 kJ/kg.K and R = .287 kJ/kg.K) enters a turbine with a pressure of 1MPa and temperature 500oC, and exits at 100kPa and 180oC. Assume adiabatic operation, and neglect kinetic and potential energy effects. Calculate the isentropic efficiency. Conversion factors: 1 bar = 100 kPa 1 Btu = 778 lbf.ft 1 psi = 1 lbf/in2 gc = 32.2 lbm.ft/lbf.s2 K = oC + 273 oR = oF + 460