PDA

View Full Version : Glycol ice bank







scorpx
30-09-2013, 10:33 PM
One of my custommer have Ice Bank ( Coils system in pool) Refrigerant is R717. Now output temrature of water is 0.5 C to 2 C . Compressors works only 8 Hour and stock Ice throw to coils, Then compressors stop and system use same ice for all day. Now this company wants -6C water output temp. Now question is if we add ethylene glycol %20 with water and freze this mix in -7C. can we get output -6C Water for all day ????? I never saw somethink like that. is it possible or not

mad fridgie
30-09-2013, 11:22 PM
A little less than 20%, will suffice.
Pumping properties and heat transfer co-efficents will change.

RANGER1
01-10-2013, 10:49 AM
I assume you mean -6C glycol, not water !
I could be wrong, but the glycol may not freeze on coil like ice, so it may not last all day like ice build up.

Correct me if I am wrong.

What is the purpose of the chilled water, or glycol?

scorpx
01-10-2013, 10:50 AM
So is it possible to Freeze gylcol and store it like a ice ? ?

scorpx
01-10-2013, 11:18 AM
I assume you mean -6C glycol, not water !
I could be wrong, but the glycol may not freeze on coil like ice, so it may not last all day like ice build up.

Correct me if I am wrong.

What is the purpose of the chilled water, or glycol?
Purpose is just use compressors 8 hour in a day and store gylcol ice (if is it possible) and use these ice for 16 hour. now system Works like that but output temperature of water is +0.5 C or +2.0 C. this water using in Water evaporaters for rooms but rooms can be +8 C minimum with +1 water. But we need +2room temperature.

mad fridgie
01-10-2013, 11:36 AM
Yes it will freeze, not quite the same ice but close enough.
If you want your rooms at 2 instead of 8, then you are going to need more storage, plus to make LT ice, you are going to have a lower SST, so reduced refrigeration capacity, so if 8 hours was just enough before, it will not be enough know.
You will pumps less, reduced heat capacity out of the coils. so do not expect the same results as you did with water.
Is the rooms used for food, or an industrial process, you may have to check that your glycol of choice is acceptable.

hookster
02-10-2013, 08:05 AM
Hi as mad fridgie says you will eventually freeze glycol mix but it will not be in your 8hr cycle. You could probably get fluid (glycol mix) down to -2 with continuous cycle of fridge plant. (giving up all the energy savings the ice bank was designed around) The ice bank is designed to match peak load conditions with the stored energy.

Has room load increased since original design? Usually room evaporators are designed for smaller delta T on ice bank systems with a much larger evaporator surface area. I presume there is no defrost on the coils as they are not normally included / needed. If you lower on temperatures of fluid you may find you start getting icing.

I would advise if room heat loads have not increased significantly to check condition of evaporators. Are they clean, door control, is air flow good, fans etc.

If load has increased in room best option is either increase ice storage capacity and increase evaporator surface in rooms.

Check your fluid on off temperatures to evaporators
Check how long in daily cycle stored ice is available (I think you are using up the stored potential quicker than design)
Check you refrigerant plant is operating correctly
Check ice sensors are in correct positions

Remember a usual ice bank design is 8 hours stored potential and 12 hours build during lower ambient. If the demand time exceeds this you will reduce ice build.

The benefit of the ice bank is a lower sized refrigerant plant for the peak load demand!

scorpx
03-10-2013, 09:18 AM
Thanks Hook
i Will check all you mention it and i can change eveparators (bigger ones) if need.

My problem is This custommer wants Gylcol Ice Storage.

I never see somethink like that i made many times -7C Gylcol / water mix Storage (witout ice)
And use it like a battary.

But What is Gylcol İce ? Is there any advantages Gylcol ice to Gylcol / water mix ?