Air is used as the working fluid in a simple ideal Brayton cycle that has a pressure ratio of 12, a compressor inlet temperature of 300 K, and a turbine inlet temperature of 1000 K. Determine the required mass flow rate of air for a net power output of 70 MW, assuming both the compressor and the turbine have an isentropic efficiency of (a) 100 percent and (b) 85 percent. Assume constant specific heats at room temperature.

37 q 1

An ideal gas initially at Pi , Vi , and Ti is taken through a cycle as shown in Figure. (a) Find the network done on the gas per cycle for 1.00 mol of gas initially at 0°C. (b) What is the net energy added by heat to the gas per cycle?

ASAP

Practical steam engines utilize 450C steam, which is later exhausted at 270C. (a) What is the maximum efficiency that such a heat engine can have? (b) Since 270C steam is still quite hot, a second steam engine is sometimes operated using the exhaust of the first. What is the maximum efficiency of the second engine if its exhaust has a temperature of 150C? (c) What is the overall efficiency of the two engines? (d) Show that this is the same efficiency as a single Carnot engine operating between 450C and 150C. Explicitly show how you follow the steps in the Problem-Solving Strategies for Thermodynamics.

A 4.00 L sample of a diatomic ideal gas with specific heat ratio 1.40, confined to a cylinder, is carried through a closed cycle. The gas is initially at 1.00 atm and at 300 K. First, its pressure is tripled under constant volume. Then, it expands adiabatically to its original pressure. Finally, the gas is compressed isobarically to its original volume. (d) Find the temperature at the end of the cycle. K   (e) What was the net work done on the gas for this cycle?J

Suppose an ideal (Carnot) heat pump could be constructed. (a) Using the equation |Qc| |Qh| = Tc Th obtain an expression for the coefficient of performance for such a heat pump in terms of Th and Tc. (COP)ho,C =     (b) Would such a heat pump work better if the difference in the operating temperatures were greater or were smaller?   (c) Compute the coefficient of performance for such a heat pump if the cold reservoir is 51.0°C and indoor temperature is 64.6°C.