Partial 2-phase properties from separate liquid vapor properties
Partial 2-phase properties from separate liquid vapor properties
(OP)
I need to find the properties of a stream which is in two-phase. I'm only given separate properties i.e. liquid and vapor properties. I need to find the enthalpy for the two-phase mixture from the liquid and vapor enthalpy. See the table below:
I would really like to know how do I find mixture properties i.e. density, thermal conductivity, specific heat, viscosity & enthalpy
I would really like to know how do I find mixture properties i.e. density, thermal conductivity, specific heat, viscosity & enthalpy
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RE: Partial 2-phase properties from separate liquid vapor properties
with a similar expression for derivatives, cp = (dH/dT)p
the same for density, Density(mixture) = 1.0 / (Volume(vapor)+Volume(liquid))...
while for thermal conductivity, viscosity etc. you need mere elaborate expressions, see The Properties of Gases and Liquids or similar for details...
RE: Partial 2-phase properties from separate liquid vapor properties
The H(mixture) = H(Vapor) + H(Liquid) as you mentioned; I got the calculated duty closed to the required duty.
I also tried another method which H(mixture) = [wt. fraction (vapor) x H(vapor)] + [wt. fraction (liquid) x H(liquid)] and I get really close duty to the required duty.
At first I also tried adding up the enthalpy but for different case sometimes I got duty which is way off from the required duty.
I needed to find the enthalpy mixture so that I could find the LMTD for a two-phase for a partial two-phase heat exchanger where one side is sensible heat (single phase) and the other side is latent heat (partial phase) then plotted T-h diagram for the process
RE: Partial 2-phase properties from separate liquid vapor properties
I attach a (very basic) Excel page which calculates temperatures in diferent zones, but there are many similar examples...
RE: Partial 2-phase properties from separate liquid vapor properties
Yes, basically (I think) I'm had to look for specific enthalpy because after I find the H(mixture) at specific temperature points, I had to make a cumulative enthalpy and from there multiply each cumulative enthalpy with mass flow to obtain required duty. Afterwards the program plot the T-h diagram with both streams and find its effective LMTD.