Chapter 7, Problem 7.17CU

Consider an ideal Brayton cycle of air where the pressure ratio ñ across the compressor is equal to 5 and the air temperature at the turbine inlet is 900 °C. If the pressure and temperature of the air ambient are equal to 1 bar and 40 °C, respectively a) Determine the pressure, temperature and specific volume in the different states of the cycle. b) Calculate the work per unit mass developed by the turbine. e) Determine the work per unit mass required by the compressor. d) Calculate the net work per unit mass developed by the gas turbine. e) Determine the thermal efficiency of the cycle.

The temperature at the beginning of a compression process of an air standard Otto cycle with acompression ratio of 8 is 300 K, the pressure is 1 bar and the cylinder volume is 560 cm3. Themaximum temperature during the cycle is 2000 K. Determine a) the temperature, pressure andvolume at the end of each process of the cycle, tabulating your answers, b) the thermal efficiencyof the cycle, and c) the mean effective pressure, in Bar. Take γ = 1.4, and cv = 718 J/kg/K

7.42. Jets of high-speed steam are used in spray cleaning. Steam at 15.0 bar with 150°C of superheat is fed to a well-insulated valve at a rate of 1.00 kg/s. As the steam passes through the valve, its pressure drops to 1.0 bar. The outlet stream may be totally vapor or a mixture of vapor and liquid. Kinetic and potential energy changes may be neglected. (a) Draw and label a flowchart, assuming that both liquid and vapor emerge from the valve. (b) Write an energy balance and use it to determine the total rate of flow of enthalpy in the outlet stream (Hout = mH¡ + m,Ĥv). Then determine whether the outlet stream is in fact a mixture of liquid and vapor or whether it is pure vapor. Explain your reasoning. Problems 393 (c) What is the temperature of the outlet stream? (d) Assuming that your answers to Parts (b) and (c) are correct and that the pipes at the inlet and outlet of the valve have the same inner diameter, would AĖk across the valve be positive, negative, or zero? Explain your…