Exam Lesson Name: Basics of Earth Science Exam number: 703800RR
Exam Guidelines
Exam Instructions
Question 4 of 20 :
le
Select the best answer for the question.
4. AlAn is a pure substance that can't be broken down into simpler substances by chemical
or physical means.
Ice
m
pe
eo
O A. mineral
OB. chemical
C. atom
D. element
Mark for review (Will be highlighted on the review page)

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)