- #1

Imolopa

- 21

- 1

I've been given the following relations where as I understand it subindex 2 equals subindex e and subindex 1 equals subindex i:

***EDIT***

More accurately

subindex 1; initial state of a control mass

subindex 2: end state of a control mass (end state is simply state 2 in the problem at hand)

subindex CV for work W and heat Q denotes what work W and work Q passes through the boundaries of what is defined as the control volume CV in the situation.

***END EDIT***u

and

u

Relation 1:

(Q - W)

However the above relations seem to contradict the previous statement:

So what is correct? And what is happening here?

***EDIT***

More accurately

subindex 1; initial state of a control mass

subindex 2: end state of a control mass (end state is simply state 2 in the problem at hand)

subindex CV for work W and heat Q denotes what work W and work Q passes through the boundaries of what is defined as the control volume CV in the situation.

***END EDIT***u

_{2}= h_{e}and

u

_{1}= h_{i}Relation 1:

_{1}(Q - W)_{2}=_{1}Q_{2}-_{1}W_{2}= m [ {u_{2}- u_{1}} + ( 1/2 ) * [ { v_{ 2 }^{ 2 }} - { v_{ 1 }^{ 2 }} ] + g {Z_{2}- Z_{1}} ]Relation 2:(Q - W)

_{CV}= Q_{CV}- W_{CV}= ∑ m_{e}[ ( h_{e}+ ( 1/2 ) * { v_{ e }^{ 2 }} + gZ_{e}] - ∑ m_{i}[ ( h_{i}+ ( 1/2 ) * { v_{ i }^{ 2 }} + gZ_{i}]Now in thermodynamic tables we have different columns for internal energy u and enthalpy h with different values, iow. h and u are different for the same state..However the above relations seem to contradict the previous statement:

So what is correct? And what is happening here?

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