What is the pressure generated by water at different temperatures?
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I would appreciate it if everyone could help me out. I’ve run into this problem recently and am a bit confused: there are two open vertical pipes, each one meter in height, and a differential pressure transmitter is installed at the bottom of each pipe. The two pipes are exactly identical. One is filled with cold water, and the other with warm water at 60 degrees. I want to know what the pressure values should be in these two cases. My measurements show that the pressure is higher for the warm water and lower for the cold water – what is the normal value? I would also appreciate it if friends could help explain it.
For open pipes, I’ve checked that the density of water at 60 degrees is lower than that of cold water; yet the data shows that the pressure in warm water is higher. If the height is the same and the volume is also the same, then the densities should be equal. How can it be that the value of lower density is higher? Pressure = density * height * gravity – isn’t that the formula used?
You use a gauge pressure transmitter to measure the height of the liquid column, thereby determining the pressure (gauge pressure). Normally, it should be the conclusion upstairs. So, has the transmitter’s “zero point” been calibrated? Are the two transmitters installed at the same height? Your measurement is around 10 KPA, so it’s necessary to carry out these tasks. Or, swap the transmitters and take measurements to see what’s going on?
Haha, seeing you type so much – what you say makes quite sense; the other things don’t matter that much. What others have told me is that, actually, I just want to know the difference between cold and hot water under the same measurement conditions. Logically, the pressure of hot water should be lower due to its lower density, but in reality the pressure of hot water is higher – it’s strange. I performed this operation just to check whether there was anything wrong with the transmitter. As you said, the pressure difference is only around 100 pascals, but such a difference is not acceptable in practical applications. Please understand, haha
Actually, it involves taking two measurements in the same open pipe, once with cold water and once with hot water; the pipe is filled with water, just to make things clearer. Are you saying that it should be the pressure of warm water that matters? But the density of warm water isn’t normal
Then, warm water can be gradually mixed in with cold water to replace it, in order to observe the trend in pressure changes. If 100 Pa is not allowed either, then simply check the liquid level in the glass tube and use a magnifying glass. ;P
What is the purpose of the original poster doing this?
This error may not be a measurement error at all; it could simply be an instrument error – for instance, the accuracy of the instrument changes with temperature variations (perhaps because the instrument’s measurement principle does not take into account the effect of temperature).
It is recommended to use a U-shaped mercury level gauge for measurement; it will be clear at a glance. Don’t waste time on these pointless things; not all electrons are necessarily good. From a production perspective, ROSEMNET and EJA offer good continuity; as for installation specifications and the selection of appropriate models, it is important to be careful and not act blindly. For reference only.
The pressure guide tube is a blind tube; once it goes in, it isn’t released and remains there. What I mentioned earlier about \"replacing cold water with hot water\" is to keep cold water remaining in the pressure guide tube; in other words, it takes into account the change in diaphragm temperature as considered by the senior colleague. Original poster, try again by “replacing cold water with hot water” and give us a conclusion.