Consider an ideal Brayton cycle operating on air. The inlet to the compressor is 300 K, 100 kPa. The compressor and turbine pressure ratios are 10. The maximum temperature in the system is 2000 K. Treat the air as an ideal gas with constant specific heats. a. What is the efficiency of this cycle? (Note: see derivation in section 10.1) b. What would the efficiency be for a Carnot cycle operating between the same temperature limits? c. You should have found that the efficiency of this cycle is less than the Carnot efficiency. So, there must be some irreversibility and entropy generation. For each of the four processes (compressor, heat addition, turbine, heat rejection), find the entropy generation per kg of air. For this analysis, assume the best-case scenario – heat is transferred to the high-T heat exchanger from a reservoir at 2000 K and heat is removed from the low-T heat exchanger to a reservoir at 300 K. d. If entropy is generated during this cycle, where does it go? e. What is the back-work ratio for this cycle? In other words, what is w /W turbine ? compressor f. It is difficult to create an isentropic compressor. For a Brayton cycle with the same parameters as above, what is the cycle efficiency if the compressor efficiency is 80%?
Consider an ideal Brayton cycle operating on air. The inlet to the compressor is 300 K, 100 kPa. The compressor and turbine pressure ratios are 10. The maximum temperature in the system is 2000 K. Treat the air as an ideal gas with constant specific heats. a. What is the efficiency of this cycle? (Note: see derivation in section 10.1) b. What would the efficiency be for a Carnot cycle operating between the same temperature limits? c. You should have found that the efficiency of this cycle is less than the Carnot efficiency. So, there must be some irreversibility and entropy generation. For each of the four processes (compressor, heat addition, turbine, heat rejection), find the entropy generation per kg of air. For this analysis, assume the best-case scenario – heat is transferred to the high-T heat exchanger from a reservoir at 2000 K and heat is removed from the low-T heat exchanger to a reservoir at 300 K. d. If entropy is generated during this cycle, where does it go? e. What is the back-work ratio for this cycle? In other words, what is w /W turbine ? compressor f. It is difficult to create an isentropic compressor. For a Brayton cycle with the same parameters as above, what is the cycle efficiency if the compressor efficiency is 80%?
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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Transcribed Image Text:Consider an ideal Brayton cycle operating on air. The inlet to the compressor is 300 K,
100 kPa. The compressor and turbine pressure ratios are 10. The maximum temperature
in the system is 2000 K. Treat the air as an ideal gas with constant specific heats.
a. What is the efficiency of this cycle? (Note: see derivation in section 10.1)
b. What would the efficiency be for a Carnot cycle operating between the same temperature
limits?
c. You should have found that the efficiency of this cycle is less than the Carnot efficiency. So,
there must be some irreversibility and entropy generation. For each of the four processes
(compressor, heat addition, turbine, heat rejection), find the entropy generation per kg of air. For
this analysis, assume the best-case scenario – heat is transferred to the high-T heat exchanger
from a reservoir at 2000 K and heat is removed from the low-T heat exchanger to a reservoir at
300 K.
d. If entropy is generated during this cycle, where does it go?
e. What is the back-work ratio for this cycle? In other words, what is w
/ w
?
turbine
compressor
f. It is difficult to create an isentropic compressor. For a Brayton cycle with the same parameters
as above, what is the cycle efficiency if the compressor efficiency is 80%?
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