air dryers

Hi all, been away from the forums for a while...business has been very good.

I have a question regarding refrigerated air dryers, and more specifically shell and tube condensor attached to this machine.

We have a water cooled shell and tube condensor attached to an Ingersol Rand refrigerated air dryer. The water source is a recirculated loop, cooled in 2 cooling towers. The cooling water is shared by 3 air dryers and 6 Ingerssol Rand air compressors. this is a process system where the compressed air has to be dried before it can be used for the process.

Ok the water flow through the condensor is controlled by a head pressure activated water regulating valve.

So The question is: Should the water regulating valve be installed on the inlet side of this condensor, or the outlet side of the condensor.

Currently the water reg valve is installed on the inlet. It has operated for 15 years this way. I believe it should be installed on the outlet so the condensor is always flooded, and I believe the way it has been installed, contributes to the buildup of scale.
(Not certain about the scale, yet, but signs are there. I have yet to open the system, as the customer...isnt certain if they trust me yet, lol)

In a perfect world, i would like to suggest that we eliminate the water reg valve completely, maintain constant flow through the condensor and install a receiver and headmaster control. Any thoughts on this idea.

last question: How do I determine if this thing is working correctly. What back pressure should I be looking for. (R22) Is there any way i can determine efficiency. I have to admit that I was the factory service agency for Hi-Ross Denko 20 years ago, but life has been full of some big issues and I almost have to wear a name tag these days, in order to remember my own name (j/k) so if someone wouldnt mind jogging my memory/re-educating me, it would be much appreciated.

Quote:

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Originally Posted by Sledge

I believe it should be installed on the outlet so the condensor is always flooded, and I believe the way it has been installed, contributes to the buildup of scale.

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That would be my preference also IF a water regulating valve must be used.

If you use constant flow on the water you will have to regulate the tower supply water temperature within a fixed range, or you would still have head pressure issues.

I like the idea of eliminating the water regulator valve completely also, as it would eliminate some water flow troubles they are having...constant flow is easier to maintain than water flow that is fluctuating due to flow restriction on the system caused by these regulators.
This system works off a big holding tank of water...not sure the capacity, it is a cube 12x12x12. The temperature of the water controls cooling fans on the cooling tower and also there is a bypass valve bypassing water around the cooling tower completely, again controlled by temperature. This is the only means they have off controlling water temperature in the loop.

I dont understand why we would experience head pressure issues, if we went with a constant flow through the condensor, and used a headmaster and receiver setup. I have worked on countless systems for refrigeration that have this same set-up and they operate in Canadian winters with no issue?

I am using the word "headmaster"...might not be correct term. I am thinking of a combination valve for flooding the condensor with liquid refrigerant when temperature of condensor fluid medium is too cold. Maybe should be an OROA valve.

Hi Sledge
The HPRValve should always be on outlet for 2 reasons, higher h2o pressure and smaller air bubles = increase heat transfer. There should be a throtling valve at the end of conddenser h2o loop and now days a vsd for water pump. To measure efficiancy tricky - output/input, kW refrig divide by kW elect. kW refrig would need to measure / calculate h20 removed, humidity cond h2o temp and volume of air processed. If you look at system COP as opposed to compressor COP the HPRValve is more efficient. Not sure about the headmaster but it works on most domestic fridges.

Hi Sledge

I would fit a 3 port Penn valve to the condenser water outlet side. This will allow constant flow rate back to the tower pumps and still control its head pressure on the compressor

If you say the system has worked for 15 years, than there are other problems, try taking a look at

1. the current flow reg valve has a build up of scale or muck blocking the valve because the tower temp is constant and so is the incoming heat load by the compressor (cooled by same tower), so the water reg will open to the same size every time, catching the larger sized objects. (remember towers are open to air and can pick up contaminates that form sludge and block valves and filters

2. Check any upsteam filters of the condensers

3. Dehum units for compressors run a above freezing point evporators. There might be a EPR valve or a AXV (automatic expansion valve, common on atlas copco screw air compessors) on the evaporator. Efficiency is hard to calc as the evaporator dosen't cool the air that much <2k. The cooling is provided by the intercoolers or condenser water.

4. Check efficiency or blockages of the intercoolers on the air compressors. Check the inlet temp from the air compressor after its discharge cooling system. Discharge Air into the dehum unit should not be more than 5 to 10K above ambient.

5. if the client lets you ! lol strip down the condensers and rod them out if you suffer high liquid temps, as a last resort!

This may help with the general servicing of the machine, but always ask the question to the client, ''how long ago was that pulled apart''? before you dive in stripping things down

hope that helps

Womby :D

Hi Sledge,
I work on fridge dryers along with Ingersoll compressors , the water dryers cooled ones I`ve come across have all had the regulator valve fitted before the condensor. If the cooling towers are above the condensor then the condensors should always be flooded.
Back pressure should be around the 60psi mark with a pressure dew point of 2-6 0c. much depends on the compressed air inlet temp. I must admit I`ve never liked water cooled m/cs, with air cooled you can see what`s going on easier.
If you let me know the model No. I`ll see what I can dig out

Hi sledge. I work on Atas copco dryers and had the same problem. The regulator valve must definitely be on the outlet.

Sledge. I think i know the exact dryer you have.. Does it have a trim cooler on it? Is it an open drive 100hp compressor on it? If you got head problems make sure the water valve is on the outlet. Make sure the screen is clean.. If everything else fails that trim cooler is cooling the water for the condenser! Change the glycol!