refrigerant flow

[Bruce A. King]

Does anyone know how fast (inches per second) refrigerant flows through the typical system in cooling mode?

[David A. Andersen]

Liquid or vapor?

A/C?

Type of Refrigerant?

[Bruce A. King]

I'm mainly interested in how fast it flows through the suction line on R22 and R410 systems.

[David A. Andersen]

Your question is significantly open-ended. You have not provided any design criteria for the equipment operation.

Refrigeration velocity is designed depending on horizontal and vertical runs. The primary concern is to return refrigerant oil back to the compressor.

Is this your concern?

The type of refrigerant, the evaporator temperature, the load on the equipment at BTU/hr, the diameter of the piping and it's orientation must be taken into account.

If you're looking for a rule of thumb, we shoot for 11.666 ft./s on horizontal piping runs and 25 ft./s on vertical risers to ensure adequate velocity to return oil to the compressor.

Pressure drops on the line dependant on its construction design effect the volumetric capacity of the refrigerant as does its temperature rise above saturation.

[Bruce A. King]

So its moving rather fast.........and would have little time to be affected by missing suction line insulation between the exterior wall and the outside unit as needed for compressor cooling. agree?

[David A. Andersen]

The faster it moves, the more heat it will pick up.

Insulating the suction line is more about preventing condensation than it is about efficiency loss.

Not to say that if you had 250 feet of exposed refrigeration line across a black flat roof in Arizona that you would not get a loss!

If you measure the amount of condensation, you can get a feel for how much efficiency loss that is occurring under those particular circumstances. There is about 1000 BTUs of heat absorbed through the pipe per pound of water production.


The length of missing insulation between the house and a condenser coil in a residential setting is totally insignificant!