Air Solubility In Oil With Respect to Temperature

Hi,

any solubility is dependent on temperature and pressure, so why not of gas in fluids (or solids)?

Most solubilities increase with temperature as the gaps between the molecules of the fluids increase and there is more space available to fill with gas or water vapor.

One exception is CO2 in water, here is the solubility going down with temperature because there is a chemical reaction involved of H2O plus CO2 reacting to H2CO3, and all chemical reactions are also dependent on pressure and temperature.

So what is your problem?

Rhabe

Now i am confused too:I always believe to know first bubbles appears in a glass of water is just solved air what is being rejected when the temperature rises because the solubility decreases then some vapor bubbles could appear if temp keep rising ¿Just the CO2 in the air have this property?

Hi Ferquiza,

I assume that you are right with air in water, my experience was with air in oil, but also in this situation I am not sure about the physical and chemical principles of absorption and desorption. Likely that the surface of the walls is playing an important role.

Bubbles that form at raising temperature in water need (similar to crystals) some point of disturbance, where the energy balance is not the mean.

And if there is a first tiny bubble it may redissolve if the bubble comes detaches from the point of disturbance.

My experience is also with small pumps of low pressure and flow rate used with a mostly watery solution for hydrostatic bearings of unusual properties: to support only a few grams of load but to do this with nearly no torque transmitted to the load by non-radial flow patterns of the fluid.

The fluid has either direct contact to air or contact through plastic elements, both allow for air to go into solution and to come out as bubbles in local minima of the pressure inside the pump. These bubbles may stay attached to some structure and disturb the flow pattern and disturb the instrument that is suspended on this flow.

RHABE

Hi RHABE, Thank you for your reply. You have told that the most solubilities increase with temperature. But the Deaerator principle is that gas solubility in a solution decreases as the temperature of the solution rises. So we can reduce the solubility level by means of increasing temperature if it is in a solution and we can increase the solubility level if the soluble gases away from the solution by means of increasing temperature. Is it correct?

Hi Natarajan,

this is correct in some cases but the contrary is true in other cases of liquid-gas "solubility" as absorption and desorption and chemical reactions play an important role.

Best way to degas is to evacuate.

RHABE

With the common gases (air, oxygen, nitrogen) in water, solubility decreases with rising temperature. Solubility of oxygen from the atmosphere (i.e. at a partial pressure 0.21 bar) is given accurately enough in practice by the formula 468/(31.6 + T) mg/l where T = °C. This is pretty close for temperature range 0 - 50°C at least. Similar formulas for other gases but I can't remember them offhand.

I'd be surprised if something similar doesn't apply to other gases and liquids, but don't know without investigating.

Cheers.........Codey