Binary mixtures

Binary mixtures consist of a solvent and a cooling agent. The mass fraction of the cooling agent is specified via a parameter XI.

Binary mixtures are possible with streams of the types

• Binary mixture
• Universal fluid

In Ebsilon the following binary mixtures libraries are available.

• LibAmWa
• LibWaLi 
• LibSecRef

The LibAmWa library contains substance value functions for mixtures of ammonia and water (with ammonia as refrigerant, XI is the ammonia content).

The library LibWaLi contains substance value functions for mixtures of water and lithium bromide (with water as refrigerant, XI is the water content).

The library (LibSecRef) contains substance value functions for mixtures of a cooling agent and water. Each refrigerant/water mixture (see below) can be selected as an independent sub-library.

All three libraries are created and maintained by KCE-Thermofluidproperties.

Note on the LibWali (Water/Lithium Bromide Mixtures)

The LibWali-library is undefined in regions where solid LiBr crystallizes. For practical purposes, this reason is being avoided anyway. However, the calculation sometimes crosses states in this region. Therefore, the boundary behaviour was improved. Especially, there was a change in the behaviour of the function "dew point temperature". As the dew point (for XI<1) is always outside of the validity range, because after the evaporation of the latest water drop all LiBr will be in the solid state. For simplicity, the function returned the boiling temperature in this case.

Now, the function returns the correct value of the dew point temperature: as soon as solid LiBr begins to crystallize during the evaporation, an additional heat supply will no longer rise the temperature because the water fraction in the liquid phase remains constant now (the more water evaporates, the more solid LiBr will crystallize). Therefore, the dew point temperature must be the same temperature as where the crystallization begins. This temperature can be calculated without any knowledge about the 3-phase-region.

Note: as the dew point temperature is also used in the measurement point (component 46) with FTYP=35 ("degrees super heating") you have to change to FTYP=34 ("degrees sub cooling") with the corresponding negative value for MEASM, if you want to receive the same results as before.

Due to the extremely low steam pressure of lithium bromide, no more lithium bromide is existent in the gaseous phase, but only pure water.

Note on the LibSecRef

The mixtures available in the library and the corresponding ranges of validity for cooling agent fraction and temperature are specified in the following table. The range of the freezing points (tf) is specified as well.

Name of solute	ξmin	ξmax	tmin = tf,min	tmax=tb,max	tmax,[1,2]
Ethylene glycol	0	0.60	- 51.2 °C	110.5 °C	100 °C
Propylene glycol	0	0.60	- 50.0 °C	109.1 °C	100 °C
Ethyl alcohol	0	0.60	- 44.9 °C	80.6 °C	40 °C
Methyl alcohol	0	0.60	- 73.0 °C	74.1 °C	40 °C
Glycerol	0	0.67	- 46.5 °C	111.8 °C	40 °C
Potassium carbonate	0	0.40	- 37.5 °C	108.8 °C	40°C
Calcium chloride	0	0.30	- 48.0 °C	110.5 °C	40 °C
Magnesium chloride	0	0.215	- 33.6 °C	108.1 °C	40 °C
Sodium chloride	0	0.234	- 21.1 °C	106.3 °C	40 °C
Potassium acetate	0	0.45	- 52.0 °C	112.5 °C	40 °C
Potassium formate	0	0.48	- 50.0 °C	- °C	40 °C
Lithium chloride	0	0.24	- 62.9 °C	111.5 °C	40 °C
Ammonia	0	0.30	- 84.1 °C	27.5 °C	30 °C

With steams of type "binary mixture", negative values for FBIN have been assigned to these substances in order to make it clear, that there are certain limitations in the application, as – in contrast to NH3/H2O and H2O/LiBr (LibAmWa and LibWaLi) – no phase transitions can be handled, like they are required e.g. in the Kalina cycle.

tf is the freezing point of the solution (depending on XI (Mass fraction of refrigerant) 

tb is the boiling temperature

All physical properties functions are only available in the liquid phase.