[spirally]

1).A cylinder contains 0.5m^3 of steam,at 4bar and 200 degree celsius.if the steam
is cooled at a constant pressure untill the volume is 0.1m^3,find the mass of the steam
calculate the final dryness fraction,work done and heat transferred.

2).2kg of steam is initially at a pressure of 3bar.the initial dryness fraction is such that when
the steam has been heated at constant volume to 4 bar,it is saturated.after this heating process the
steam is compressed isentropically to 10 bar.find the final temperature.

3) A bicycle pump which has a stroke of 20cm is used to force air into a tyre against a pressure
of 4bar.what length of stroke will be swept through before air begins to enter the tyre when the piston is pushed  (a)slowly (b)quickly. Assume atmospheric pressure to be 1 bar

[Borek]

Please read forum rules.

[spirally]

i really am sorry,i would have sent the questions one at atime,but i really do need the answers
urgently.to the forum ,i apologize.

[Borek]

Please read forum rules once again. You have to try. We can help, but we won't do questions for you.

[Donaldson Tan]

You need a steam table to solve Q1 and Q2

Using Q1 as an example to guide you how to solve these 2 problems:

To find the mass of the system, you need an isobaric table (at 4 Bar) which shows how the density changes with temperature. You can generate the required steam table at the NIST Web Book. By establishing the density of steam at 4 bar 200C, you can find the mass by multiplying the volume by its density. Take note of its internal energy at that this state. Call this U₁ (unit kJ).

The state whereby vapour and liquid phases co-exist must be that at the saturated temperature and pressure. To find the required phase composition, you need the table that shows the saturated properties of water and steam. You can generate this table again at the NIST Web Book. The saturated temperature at 3.9549 bar is 143.20C. The saturated temperature at 4.1113 bar is 144.60C.  I am sure you can extract the saturated temperature at 4 bar from this data set by assuming the saturated temperature varies linearly with pressure.

Apply the same method to extract the specific volume (inverse of density) for saturated liquid and vapour phases at 4 bar. Do a mass balance between the 2 phases to establish the vapour and liquid fractions. Sum up the internal energy contributions from the liquid and vapour phases to get the internal energy of this state. Call this U₂ (unit kJ).

To find work done (W) and heat transfer (Q)

use dU = Q + W where dU = U₂ - U₁ (applicable to close system)

Since this is a close system, W = - p.dV = - (4E5)(0.1-0.5) = 160 kJ

Q = dU - W = U₂ - U₁ - 160 (Unit kJ)

To solve Q2, please go to the NIST Web Book to get your relevant data yourself and solve Q2 on your own

The NIST Web Book Address for obtaining fluid properties is: http://webbook.nist.gov/chemistry/fluid/