Hot Oil vs Glycol/water as heating medium
Hot Oil vs Glycol/water as heating medium
(OP)
Hi all,
We are looking at a new offshore oil & gas facility where we want to install a heating medium system. The heat will come from several WHRU on gas turbin outlets. Operating temperature of the system will be around 170°C (340°F), and the proposal is to go for a glycol/water mixture. I have done some work with hot oil systems before, and would have thought that would have been better suited, but naturally I am biased here
I have done some serching on the web, and some sources indicate that 170°C is too high for a glycol/water system. Others claim it is OK.
The way I see it, hot oil is less prone to fouling/degrading, can be operated at lower pressures, is inherently inert and hence less likely to cause corrosion. On the down side, it is flammable and more expensive to purchase than glycol/water. Then again,I would presume a glycol/water system would be more labour intensive in terms of operation?
Would love to have some feedback from my fellow eng-tips members.
We are looking at a new offshore oil & gas facility where we want to install a heating medium system. The heat will come from several WHRU on gas turbin outlets. Operating temperature of the system will be around 170°C (340°F), and the proposal is to go for a glycol/water mixture. I have done some work with hot oil systems before, and would have thought that would have been better suited, but naturally I am biased here
I have done some serching on the web, and some sources indicate that 170°C is too high for a glycol/water system. Others claim it is OK.
The way I see it, hot oil is less prone to fouling/degrading, can be operated at lower pressures, is inherently inert and hence less likely to cause corrosion. On the down side, it is flammable and more expensive to purchase than glycol/water. Then again,I would presume a glycol/water system would be more labour intensive in terms of operation?
Would love to have some feedback from my fellow eng-tips members.





RE: Hot Oil vs Glycol/water as heating medium
RE: Hot Oil vs Glycol/water as heating medium
The return temperature will be at least 30°C (86°F), so I don't anticipate any viscosity issues here.
RE: Hot Oil vs Glycol/water as heating medium
The temperature is a little high for glycol. Glycol works in your car at about 150C but that is because the reservoir is under pressure. If you use a closed system with a bladder for thermal expansion it should work fine. Oil does have less maintenance until the temperatures get really high. I guess I would go with whatever the client wants and just design accordingly.
Regards
StoneCold
RE: Hot Oil vs Glycol/water as heating medium
thanks for taking the time. The system (if glycol/water) will indeed have to pressurized, but at a much higher pressure than what would be the case for a hot oil system. My dilemma here is that I personally think a HO system would be better in terms of simplicity, lifetime operating cost and possibly also capital cost, but RFQs have already been issued HXs using water/glycol as the heating medium. This despite the fact that the heating medium system has yet to be designed (!).
As hot oil has lower heat capacity than glycol/water, I would expect distribution piping to be larger for the former, and that HXs will have to be slightly larger and thus costlier.
RE: Hot Oil vs Glycol/water as heating medium
Another reason for using glycol/water is the environmental impact in the event of a spill is negligible. Hot oil typically has a reportable quantity, while some of the glycols do not. Also, if the heat exchangers spring a leak (and they will) and you have tower water on the other side, it will make a mess in the tower. We have to use a two loop system to cool our hot oil - there is a hot oil to intermediate cooling water loop, then an intermediate water to cooling tower loop which has the plates replaced annually.
Regards,
Matt
Quality, quantity, cost. Pick two.
RE: Hot Oil vs Glycol/water as heating medium
RE: Hot Oil vs Glycol/water as heating medium