Regarding the difference of their saturation temperature, the so-called saturation state of the solution: it means that the liquid and the vapor are in a state of dynamic equilibrium, that is, the rate of molecules passing through the liquid surface to the vapor is equal to the rate of molecules returning from the vapor to the liquid.
Because the boiling point of lithium bromide is very high, it will not evaporate in the temperature range used in lithium bromide absorption refrigeration, so the total pressure of the vapor in equilibrium with the lithium bromide solution is equal to the pressure of the water vapor.
The vapor pressure of lithium bromide solution is very low, much lower than the saturated vapor pressure of pure water at the same temperature (and thus has strong hygroscopicity), and the higher the concentration of the solution or the lower the temperature of the solution, the lower the vapor pressure.
Because the lithium bromide molecules in a lithium bromide solution are more attractive to the water molecules than they are to the water molecules;
In addition, the number of water molecules decreases because of the presence of lithium bromide molecules in the unit volume of liquid, so the number of water molecules in the unit volume of vapor on the liquid surface is less than that on the pure water surface at the same temperature. Assuming that the liquid water is saturated, the saturation pressure of a solution of lithium bromide at the same temperature is lower than that of water.
But they have the same saturation temperature; If the pressure of the solution of lithium bromide is increased to be equal to the saturation pressure of water, the saturation temperature of the solution must be greater than the saturation temperature of water. So in the generator, the water vapor produced is always overheated.
