Should suction accumulators be insulated?

[superheated]

I always find excessive frosting on suction accumulators a nuisance. Any suggestion as to what are the causes and if insulation is the way to prevent it.

[Brian_UK]

It shows that the accumulator is doing the job it was designed for.

Possible causes are liquid boiling off inside or perhaps due to the pressure drop through the accumulator causing the temperature change. It could also be due to low ambient temperatures.

If you insulate it then you may loose the heating effect that is required for it to work properly.

[Billy Ray]

Suction accumulators will frost if the refrigerant temperature is low enough, this is not necessaraly a problem (except excessive rusting).

Suction accumulators are installed to collect refrigerant that has splashed over from the evaporator, typically in plants which have varying loads, blast chilling / process cooling etc. This is due to the ex valve not being able to control at the varying load conditions.

My thoughts are that heat is required to evaporate the refrigerant collected, therfore a heat source is required.

This could be achieved by leaving the accumulator uninsulated, however i prefer to use a accumulaor with the liquid line passing through. There is plenty of heat in liquid refrigerant avaialble, & a bonus of subcooling the liquid is achieved.

Back to basics, you dont really want the ex valve hunting & causing the effect in the first place!!

Billy Ray

[SteinarN]

If rust isnt a problem, yes. There is no ned for external heat for the trapped refrigerant to leave the accumulator. It is a smal hole in the bottom of the outlet tube. Trapped refrigerant (and oil) enters the outlet tube trough that hole. If that hole wasnt there the accumulator would be an absolutely terific oil accumulator or more precise an oil trap. The oil cant evaporate and wouldnt stand any chance in hell to escape the accumulator after first entering it.

[nike123]

This could be achieved by leaving the accumulator uninsulated, however i prefer to use a accumulaor with the liquid line passing through. There is plenty of heat in liquid refrigerant avaialble, & a bonus of subcooling the liquid is achieved.


Billy Ray

Here you talking about Combination Accumulator/Sub-Cooler !!

http://tinyurl.com/2yav3c

[Argus]

It shows that the accumulator is doing the job it was designed for.

Possible causes are liquid boiling off inside or perhaps due to the pressure drop through the accumulator causing the temperature change. It could also be due to low ambient temperatures.

If you insulate it then you may loose the heating effect that is required for it to work properly.

I agree.


But, if the frost is persistent or semi permanent, then rust may deteriorate the surface metal of the accumulator as was already pointed out - it is, after all, a pressure vessel and must be safe at all times and protected from corrosion.

Presuming that there are no problems with the system that is causing liquid to settle back through the suction line, vapour that is below the dew point will always attract moisture from the air.

However, if insulation is unavoidable, (for example the ice is presenting a hazard), Why not consider a small heater with insulation?
A crankcase heater, a hundred Watts or so, depending on the size of the vessel, and some insulation may solve the problem.

Heat in the accumulator you want - ice on the outside you don't.


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[superheated]

thanks all, great help.

[monkey spanners]

I replaced an accumilator last year and insulated it as the original had been insulated. I believe it was a Henry accumilator, which was the same diameter as a model of that companies oil seperators, so i got a heater for an oil seperator and fitted that too as the original also had a heater.

Jon