# First Law of Thermodynamics help

**1. The problem statement, all variables and given/known data**

Steam flow through a pipe at a pressure if 8bar and a temperature of 340C. A valve is opened and steam is allow to enter an insulated enclosure whose volume is 0.5(m^3), until the pressure equals the quantity of steam that enters the enclosure.

**2. Relevant equations**

Q – W + ∑M_{IN}(h_{IN}+(v^{2}_{IN})/2+gz_{IN}) – ∑m_{OUT}(h_{OUT}+(v^{2}_{OUT})/2+gz_{OUT}) = m_{2}(u_{2}+(v^{2}_{2})/2+gz_{2}) – m_{1}(u_{1}+(v^{2}_{1})/2+gz_{1})

**3. The attempt at a solution**

(Here is where I’m not sure)

I know that:

gz = 0 for all

And I would have thought that because up until the pressure in the chamber is equivalent to the mass of the steam, m_{OUT} would be zero, as the steam is only coming in.

I also THINK that Q is 0 because no heat is being added to the system, and W is zero because there is no mechanical reactions.

However, what I don’t understand is the answer says that m_{1} is 0 (why? Is this because the only input is m_{IN}?), v_{IN} is 0 (is this because of the equivalence of v_{1} and v_{IN}?)

The next step in the solution is

m_{IN}h_{IN} = m_{2}u_{2}

And is it right that m_{IN} and m_{2} will be equivalent based of continuity?

Thanks for any help as I am alright with using steam tables and interpolation later

**1. The problem statement, all variables and given/known data**

**2. Relevant equations**

**3. The attempt at a solution**

http://ift.tt/1viSe2Z

## Leave a comment