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Was wondering in practical the operating high pressure reading taken at compressor discharge service valve (hot has pressure) has the same high pressure reading taken after an air-cooled condenser (High pressure liquid)?
If it is normal to have a pressure difference, what is the cause of it?
The pressure loss you describe is caused by the flow resistance of the piping, fittings, valves, etc. The pressure of the high-side can vary between the compressor discharge service valve to the inlet of the expansion valve. All of this is the high-side of the system.
However, there are slight differences in the pressure at any point in the high-side of the system. The compressor discharge service valve will have the highest measurable pressure. At the inlet to the condenser, the pressure will be slightly lower. At the exit of the condenser, the pressure will be even lower.
When flow occurs in the system (and it will when the compressor is running normally) the flow creates pressure drop. Larger pipes will have a lower pressure drop, than smaller pipes with the same mass flow (same kg of refrigerant circulated per minute).
Each component cause pressure loss (heat exchangers, solenoid valves, service valves, etc.)
Changes in elevation can cause pressure loss also. A good example of this is a vertical liquid line. The pressure will be higher at the bottom of the pipe, but lower at the top. The pressure at the top of the pipe is less because of static pressure and friction loss (flow through the pipe).
The only way you will see no pressure loss is if the compressor is not running.;)
ExactlyQuote:
The only way you will see no pressure loss is if the compressor is not running.
Cofreth it's like in any other hydraulic system . . . friction loss occures in the lines . . . between any 2 points and even if the line is straight with no elbows or other restriction friction losses will occure . . .this loss will occure due to the fluid viscosity and to the internal pipes surface propreties . . . so with elbows and other restrictions immagine the losses , like a car in on a straight road and suddenly meets and elbow . . . will it be at the same speed ?:D
this is a link that talks about the losses in pipes and duct systems
http://www.engineeringtoolbox.com/to...pes-d_625.html
regards
US Iceman & Botrous,
Thank you very much for the information.
Sometimes when we refer to what is the system high pressure reading, so actually which part of the high side it is refering to? (Before or after condenser or as close to TXV)
I have ever came across a DunhamBush air-cooled screw chiller running on R-22 gas and the pressure difference before & after condenser coil about 30psig.
I guess this is nomal?
Hi Cofreth,
I have attached a file to show the basic refrigeration. The dotted line through the middle of the drawing separates the high-side and low-side of the system.
As you can see in the picture, the high-side is from the compressor discharge to the inlet of the TXV.
The low-side is from the TXV inlet to the compressor suction.
At any point in the refrigeration system you will find different pressures and temperatures. Part of the issue when troubleshooting a system is determining if the temperature is a saturated temperature, or something else.
Any pressure & temperature that matches the pressure/temperature chart is saturated. If the recorded temperature (from the system) is higher than the pressure/temperature relationship shown on a pressure/temperature chart, the refrigerant is probably superheated.
If the temperature recorded from the system is lower than the pressure/temperature relationship shown on a pressure/temperature chart, the refrigerant is probably subcooled.
Here is a link for a quick review of pressure/temperature charts. This is one of the most important pieces of information you can use for troubleshooting a refrigeration system.
http://www.sporlan.com/10-135.pdf
I do not remember what the pressure drop is for an air-cooled condenser, but I know they are much higher than any other component. This is the way they are circuited.
Regards,
US Iceman
The old gold website :)Quote:
Here is a link for a quick review of pressure/temperature charts. This is one of the most important pieces of information you can use for troubleshooting a refrigeration system.
http://www.sporlan.com/10-135.pdf