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此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 eagle 回复

eagle — Sun, 20 Apr 2008 21:19:49 +0800

i forget carnot engine liao... no time to read up now also... :(

此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 WoAiMeiMei 回复

WoAiMeiMei — Sun, 20 Apr 2008 19:50:53 +0800

woot! part b = 1831.4915 W

i just did...

405 - 334.2 = 1.2118

1 - ans = efficiency

388 / efficiency = 1831W

此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 WoAiMeiMei 回复

WoAiMeiMei — Sun, 20 Apr 2008 19:48:17 +0800

28 part a:

i used e= w/q(h) to give q(h)....

so the answer is like 2219.49 W

trying to do part b

此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 justinfoo 回复

justinfoo — Sun, 20 Apr 2008 00:54:03 +0800

If I'm not wrong,

P28

You need to find the entropy, S

Let Sb = entropy of saturated water at 132 + 273 = 405K and Sa = entropy of saturated steam at 405K

Look for values of both entropy from steam tables....

Then use : Qh = Th(Sb - Sa) and Qc = Tc(Sb - Sa)

此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 WoAiMeiMei 回复

WoAiMeiMei — Fri, 18 Apr 2008 21:51:49 +0800

help? :x

此讨论主题刚由 Physics - Entropy, 2nd law of thermodynamics 于 WoAiMeiMei 回复

WoAiMeiMei — Thu, 17 Apr 2008 20:35:18 +0800

ahh im having problems with these 2 remaining questions

SOLVED : P8 (mistake with scale)
P28

Notes:

P32 (Part b) - how do i do this? hint is given below
How are pressure and volume are related in an adiabatic expansion? Can you determine the type of gas from the value of gamma γ? How much heat is involved in an adiabatic process? In which process, A to B or C to D, is heat absorbed? Lost? Can you get the temperature change in terms of the product of pressure and volume? How is efficiency related to the heat gained and heat lost?

*expired notes*

P8 - The line is not linear.
i tried formula delta s = cm ln (Tf / Ti)
which is 125 = c x 0.376 x ln (390 / 300)
Correction: it should be 125 = c x 0.376 x ln (390 / 315)

P28 - W=Qh-QL, Qh/Th=QL/TL and P=W/t.... what do i do? t=1? i did it and it gives me 388 W again. would both answers a and b be the same?