Read the question, and then use the drop-down menus to complete the paragraph. What is Earth’s atmosphere made of? The most abundant gas in Earth’s atmosphere is , followed by , which is needed to burn wood and fuel. The third-most abundant gas is . The amount of in the atmosphere is very small, making up just 0.033% of the atmosphere, but it is very important because plants use it to make simple sugars. Another important gas is water vapor, which condenses around in the atmosphere to form clouds and then rain.

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)