Blended Refrigerants Boiling Point(s) and Sensible Heat
I'm investigating potential blended refrigerants for a low temperature application. Lets say the evaporator is at atmospheric pressure, and the blend is 70% Argon, 15% Ethane, 15% Propane. (No smoking near the refrigerant!:confused:)
At this pressure, ethane will boil at 185 K and propane will boil at around 230 K. My thermodynamics is a little rusty so I'm wondering how much sensible heat is transfered into the refrigerant when one of the components is boiling ( and receiving a lot of latent heat). When the ethane starts boiling, I want to know how to determine how much sensible heat will be received compared to latent heat? Keep in mind the evaporator is part of a counter current heat exchanger, ideally with a 5-10C temperature difference between streams.
I've found whats called the Jakobs # which is a dimensionless number:
Ja = (Temp_Surface - Saturation_Temp ) / (Latent Heat Vaporization)
But I can't use this equation yet until I know the other streams temperature, which is depended on this stream!
Re: Blended Refrigerants Boiling Point(s) and Sensible Heat
Sorry my freind, but another wrong answer, lol.
I presume you have calculated you boiling points based upon each refrigerant being pure, and assuming that they will act indepentanly of the other refrigerants, this is not case in a flowing system, you need to calculate the properties of the blend as a whole (class as a single refrigerant).
Re: Blended Refrigerants Boiling Point(s) and Sensible Heat
Quote:
Originally Posted by
mad fridgie
Sorry my freind, but another wrong answer, lol.
I presume you have calculated you boiling points based upon each refrigerant being pure, and assuming that they will act indepentanly of the other refrigerants, this is not case in a flowing system, you need to calculate the properties of the blend as a whole (class as a single refrigerant).
I can understand how that would be possible using a mixture with two very similar boiling points (small glide) but when they are this far apart there should be two distinct boiling points and condensation points. We've been experimenting with flue gas from coal combustion and shown that different chemicals are condensing at different temperatures.
