An air standard cycle with constant specific heats is executed in a closed system with 0.003 kg of air and consists of the follo
wing three processes:
1-2 - V= Constant heat addition from 95 kPa and 17 Deg Celcius to 380 kPa
2-3 - Isentropic expansion to 95 kPa
3-1 - P= Constant heat rejection to initial state
a) Show cycle on P-v and T-s diagrams
b) Calculate net work per cycle in kJ
c) Determine thermal efficiency
1-2 - V= Constant heat addition from 95 kPa and 17 Deg Celcius to 380 kPa
2-3 - Isentropic expansion to 95 kPa
3-1 - P= Constant heat rejection to initial state
a) Show cycle on P-v and T-s diagrams
b) Calculate net work per cycle in kJ
c) Determine thermal efficiency
1 answer:
Answer:
a) Please see attached copy below
b) 0.39KJ
c) 20.9‰
Explanation:
The three process of an air-standard cycle are described.
Assumptions
1. The air-standard assumptions are applicable.
2. Kinetic and potential energy negligible.
3. Air in an ideal gas with a constant specific heats.
Properties:
The properties of air are gotten from the steam table.
b) T₁=290K ⇒ u₁=206.91 kj/kg, h₁=290.16 kj/kg.
P₂V₂/T₂=P₁V₁/T₁⇒ T₂=P₂T₁/P₁ = 380/95(290K)= 1160K
T₃=T₂(P₃/P₂)⁽k₋1⁾/k =(1160K)(95/380)⁽⁰°⁴/₁.₄⁾ =780.6K
Qin=m(u₂₋u₁)=mCv(T₂-T₁)
=0.003kg×(0.718kj/kg.k)(1160-290)K= 1.87KJ
Qout=m(h₃₋h₁)=mCp(T₃₋T₁)
=0.003KG×(1.005kj/kg.k(780.6-290)K= 1.48KJ
Wnet, out= Qin-Qout = (1.87-1.48)KJ =0.39KJ
c)ηth= Wnet/W₍in₎ =0.39KJ/1.87KJ = 20.9‰
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Answer:
I am writing a Python program. Here is the function letterCount. This function takes two string arguments text and letter and return count of all occurrences of a letter in the text.
def letterCount(text, letter):
count = 0 # to count occurrences of letter in the text string
for char in text: # loop moves through each character in the text
if letter == char: # if given letter matches with the value in char
count += 1 # keeps counting occurrence of a letter in text
return count # returns how many times a letter occurred in text
Explanation:
In order to see if this function works you can check by calling this function and passing a text and a letter as following:
print(letterCount('apples are tasty','a'))
Output:
3
Now lets see how this function works using the above text and letter values.
text = apples are tasty
letter = a
So the function has to compute the occurrences of 'a' in the given text 'apples are tasty'.
The loop has a variable char that moves through each character given in the text (from a of apples to y of tasty) so it is used as an index variable.
char checks each character of the text string for the occurrence of letter a.
The if condition checks if the char is positioned at a character which matches the given letter i.e. a. If it is true e.g if char is at character a of apple so the if condition evaluates to true.
When the if condition evaluates to true this means one occurrence is found and this count variable counts this occurrence. So count increments every time the occurrence of letter a is found in apples are tasty text.
The loop breaks when every character in text is traversed and finally the count variable returns all of the occurrences of that letter (a) in the given text (apples are tasty). As a occurs 3 times in text so 3 is returned in output.
The screen shot of program along with output is attached.
