August 15, 2009

Steam Properties - II

In the previous post I discussed about P & T correlation for saturated steam. I also mentioned that its better to use Excel add-in than using these formulae in Excel sheet. However, these are essentially required if you are using some non worksheet based computer program for the evaluation / simulation of your project.

So here I will cover the other major property that is enthalpy & latent heat for steam.

2. Enthalpy of Saturated Steam at Given Temperature

Enthalpy Hv = alphat + gamma

alphat = 0.99615 t + 1.8239 x 10^-6 * t^2 -0.13468 x 10^ (-0.036 t) + 0.13468

gamma = 597.34 - 0.555 t - 0.2389 x 10^alpha

alpha = 5.1463 - 1540 / T

Where t = temperature in °C
T = temperature in K

So if you need to find out the enthalpy at a given P, you first need to calculate saturation temperature based on methods given earlier.

3. Enthalpy of Saturated Water at Given Temperature

Hl = 0.001 t2 + 0.8663 x t

Where Hl = enthalpy of Saturated liquid at t temperature in Kcal/Kg
t = temperaure in °C

4. Latent heat of Vaporization at Given Temperature

Lambda = Hv - Hl

Hv & Hl are calculated above.


5. Saturation temperature from Pressure
This part is also required frequently, so I developed an equation based on data from steam tables.

t = A x y^5 + B x y^4 + C x y^3 + D x y^2 + E x y + F
Where
y = Log10 (Pv)

A = 0.03878244
B = 0.5246778
C = 2.7767678
D = 12.6450237
E = 63.9525883
F = 99.082168

Pv is in Kgf/cm2.

List of other property estimation methods on this Blog.

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