Thermodynamics - I am so frustrated!

Homework Statement

Water @ 100kPa and 127 C
Find final temp using:
a. water table
b. ideal-gas table
c. constant specific heat

Homework Equations

Cp = a + bT + cT^2 + dT^3
the constants are also listed in the table

The Attempt at a Solution

by using the superhead water table to find u1 at 2547.618 kJ/kg, I added the 700 kJ/kg and then interpilated to get a final temp of 568 C. This seems correct.

I don't see how one can use the ideal gas tables, and I am at a loss as how to use the constant specific heat to find the final temp. Please advise as how to compute! Thanks

Related Engineering and Comp Sci Homework Help News on Phys.org
(ugh...I may not be so much help after all, I seem to have forgotten a lot

but maybe it's helpful anyway...I'm pretty sure about the stuff I have below, it just doesn't agree with your answer for a, and I don't know why not)

let's see if the other methods agree with your answer for a)

let's try c)

a little of the ol'

Q = mCp(T2-T1)

we don't have the mass...but we don't need it either since q = Q/m

(they gave us the heat in kJ/kg)

q = Cp(T2-T1)

so, you have q, you can look up Cp from the tables...which makes me wonder if I'm really doing part b) hmm...probably, and for part c you have to calculate Cp using the a, b, c, d constants from another table? anyways: you know the initial temperature (T1)

be careful with your units...and you should have a nice looking answer

Last edited:
Well, I see then how c) makes sense but like you say, it is WAY off a).

Thanks for the reply tho, I appreciate it bud.