Consider the heat engine in Problem 8.111. The exit temperature was given as 800 K, but what are the theoretical limits for this temperature? Find the lowest and highest temperatures, assuming the heat transfers are as given. For each case, give the first and second-law efficiencies.

Problem 8.111

Air flows into a heat engine at ambient conditions of 100 kPa, 300 K, as shown in Fig. P8.111. Energy is supplied as 1200 kJ per kilogram of air from a 1500 K source, and in some part of the process a heat transfer loss of 300 kJ/kg air occurs at 750 K. The air leaves the engine at 100 kPa, 800 K. Find the first- and second-law efficiencies.

Q80

1. A small air gun has 1 cm3 of air at 250 kPa, 27?C. The piston is a bullet of mass 20 g. What is the highest potential velocity with which the bullet can leave?

2. Consider the nozzle in Problem 7.154. What is the second-law efficiency for the nozzle?

Problem 7.154

A nozzle in a high-pressure liquid water sprayer has an area of 0.5 cm2. It receives water at 350 kPa, 20?C and the exit pressure is 100 kPa. Neglect the inlet kinetic energy and assume a nozzle isentropic efficiency of 85%. Find the ideal nozzle exit velocity and the actual nozzle mass flow rate.