What is the structure of the oil-gas separator in a heat transfer oil furnace?
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Does the separation grid inside the oil-gas separator have one-way permeability? Why is there usually a pressure of two kilograms in the return oil, and why doesn’t it flow into the expansion tank, while the makeup oil can flow from the expansion tank into the return oil pipeline?
An oil-gas separator is just a tank with nothing inside it. Although the return oil is usually under a pressure of two kilograms, the suction force of the pump is more than two kilograms; moreover, a certain height exists in the expansion tank which creates pressure. As a result, the return oil cannot reach the expansion tank. When the temperature of the heat transfer oil drops and its volume decreases, the flow rate in the pipeline leading to the pump falls, and the oil in the expansion tank flows down due to gravity
This post was last edited by jmdc on 2017-11-1 at 12:45. Does that mean that the installation heights of both the oil-gas separator and the high-level expansion tank are calculated with great precision? There’s nothing inside; what’s the use of it? Won’t it still allow oil to be added if it’s removed?
This post was last edited by 402122290 on 2017-11-1 13:27. The oil-gas separator is essentially a high-level expansion tank that accommodates changes in the volume of the heat transfer oil. If you change to new oil, there will be water in it, and air will get into the system. After being heated and expanded by the heat transfer oil, it enters the expansion tank where the oil and gas are separated; the oil drops back into the circulation system while the gas is discharged. Without an oil-gas separator, the gas will spray out along with the oil. The installation position needs to be calculated; it definitely won’t work if it’s too low
You can take a look at this cycle diagram; it’s a screenshot from Dow’s training materials
Another key function is oil-gas separation.
I would also like to ask: 1. A certain level of oil pressure is generally required in front of the circulation pump to prevent it from experiencing vacuum conditions or the heat transfer oil from vaporizing at high temperatures. What is this typical oil pressure? 2. As stated in Question 1, since the oil pressure before the circulation pump is positive, meaning the oil in the pipeline is still under positive pressure, can it be inferred that the oil-gas separator is also under positive pressure? 3. The high-level tank is generally installed at a position more than 2 meters above the highest point of the pipeline; we will use 3 meters for calculations. The density of oil is taken as 0.8*10^3 kg/m3. In this case, the hydrostatic pressure provided by the oil in the high-level tank to the oil-gas separator is approximately 0.024 MPa. However, the return pipe usually still has a oil pressure of around 0.2 Mpa at this position. I believe that the pressure of the heat transfer oil in the oil-gas separator is higher than the hydrostatic pressure exerted by the oil in the high-level tank; yet the oil in the separator does not release pressure into the high-level tank due to this higher pressure (in other words, the oil does not keep flowing continuously into the high-level tank). Why is that? Thank you!
The hydrostatic pressure calculation was incorrect; it should be the height difference from the expansion tank to the pump inlet, which is generally around 15–20 meters. The pressure at the pump inlet is roughly 0.1–0.2 MPa