# Search results

1. ### Air pressure difference between floor & ceiling

Thank you, AZ, as I too was unsuccessfully "measuring" height air dP in my room with a diff. manometer. Now I see why - so simple. I have tried just now, and exactly, as you imply, it is not possible with a flexible hose as a slightest deformation of its walls causes huge pressure fluctuations.
2. ### Static pressure inside an air conditioner's capillar

Language-thought is at all the wonder and mystery. Darvin might have originated from an ape but you, Jim, like many others in this world, and, I hope me too, we have not.
3. ### Static pressure inside an air conditioner's capillar

Thank you very much indeed for your explanation ! I understand the formulas, the physical laws, but still, something make me ask silly qwestions sometimes. Best regards ! (Proverbially the English are reknown for their newtonian empiricism in contrast to cartezian rationalism)
4. ### Static pressure inside an air conditioner's capillar

What I meant rather asking my qwestion : Can SP be lower upstreem of a point in a closed system consisting of the pipes of different diameters (and no phase change - only incompressible liquid)? Would not that imply the possibility of the existance of such thing as "negative P drop" ?!
5. ### Water speed in the closed system

BTW, water is used as refrigerant too.
6. ### Static pressure inside an air conditioner's capillar

Let's a system be as follows (with approximate but, still, real numbers). Compressed refrigerant gas get condensed in a condenser and as liquid with +/- 15 B SP enters a capillary (a "metering device"). It exits the capillary at high speed and enters the pipe leading to the evaporator having...
7. ### Water speed in the closed system

Thanks for your answers ! I am very sorry that my last post has appeared - I did not want it to. I wrote, and re-wrote a rather long post but, as writing improve thinking I finally gave it up, but, somehow, that something popped up. Sorry to have taken your time answering it. Only, Etudiant...
8. ### Water speed in the closed system

Am I right here at least - or not ?
9. ### Water speed in the closed system

let's say there is one longish line system with no branches, for instance. Two equal forces are excerted on the liquid by the pump. One force (decreasing along the line) pushes out and another force (increasing along the line) pulls the liquid back into the running pump. At some point in the...
10. ### Water speed in the closed system

I suppose, not only the flow slows more down the more far the liquid flows from the pump, but, there is a point at which its molecules stop for a moment - to accelerate after that towards the pump. It is at this point, I suppose, where the SP of the system stays always the same, independently on...
11. ### Water speed in the closed system

Does water speed in the pipes having the same diameter is strictly the same in any point of a closed (heating) system (with pump working) ? On the contrary, although liquids are "incompressible" in practice, however, does the piping still allows it to be so : the more far the water from the...
12. ### How to calculate pressure thrust created by a fan?

It is easier to measure. If you do not have a manometer, make a U-form one (transparent pipe may suit it) filled with water. Difference in water levels will show the vacuum in the box in mm of water column the fan can achieve.
13. ### Fan curve question

A fan curve goes with the fan, its manufacturer should have given it.
14. ### Underlying physics of partial pressures

Evaporation is not (yet) boiling, vapours is not steam. An example of slightly superheated steam in everyday life is the pressurised steam over the boiling water in a closed tea kettle.
15. ### Misting systems for HVAC

Sudden (unexpected) hot whether waves sometimes force to do this on the equpment not designed for high temperatures. But to keep without big reason the condensation pressure lower than designed may turn wrong. (However many would argue it would not.) Besides, for sure, the condenser fins get...
16. ### Chilled Beams vs. Variable Refrigerant Flow

Humidity control itself with those beams may ask more energy than fan consume in a fancoils system.
17. ### Does energy storage in liquid air technology pass the laugh test?

This air liquification should be most efficient in cold climate areas with their cold and dry air, by which heat rejected can be utilized for other needs.
18. ### Fire Water Main Leaking Water But Not Air

Sadly the line obviously being under the ground (not seen). Otherwise, I may be wrong however, but there should be additives for the water, very clearly seen in the light of an ultraviolet lamp.

Just the thought comes to my mind. I do not know what the type of the thread you work with, we here are basically metric and BSP (G). I would make an experiment with the metric, for instance. Would take M4, M5, M6, M8, M10, measured areas, applying the tensionmeter (forgot the proper name) make...

Sorry that I do not answer your qwestion - because I do not have an answer, but I have thought about this also. I presume, at first, the area of the contacting surfaces (nut thread/bolt thread) need to be calculated. From the force applied, friction loss is to be subtracted. Then you look up at...
21. ### Low pressure in water pipe

The remaining pump cannot do the work for two pumps.
22. ### Hydraulic total pressure

I got it so: the first statement (in my OP) - which one can meet not once in the writings on the subject - is true conditionally for only short lengthes of a system where head losses are considered negligeable. Thank you!
23. ### Pump question

It is for a closed or an open system ? Why don't you look at the pump curve?
24. ### Hydraulic total pressure

The TP at discharge is not = the TP at suction ? Why ?
25. ### Hydraulic total pressure

Does total pressure stay the same everywhere in a closed system ?
26. ### Hydraulic total pressure

Total pressure is a sum of the static pressure and the dynamic one, and is said to be the same along a pipe/duct. In the water pipe gauge (static) pressure is maximal after the pump and minimal at the pipe outlet, but the speed and the density being the same, the dynamic pressure is the same...
27. ### Air Δ P on a resistance

One little qwestion more please. For the known volume (for the known dP) to find the mass flow, what pressure (and RH) do we take : one of before the restriction, after, or a mean ?
28. ### Vacuum pumps

The pump (normal, not "turbo") speed controlled with an invertor with the invertor receiving signal from a pressure transducer. Qwestion : whether there are such pressure tr-s. ? (there should be)
29. ### Vacuum pumps

Indeed - "Turbo" - 90 000rpm ! Maybe to look for a refrigeration vacuum pump - the smallest one to be found in the trade ?
30. ### Air Δ P on a resistance

Thank you very much ! (all is clear now).