Hot well /Cold well tank sizing for chilled water application
Hot well /Cold well tank sizing for chilled water application
(OP)
Interested to know how to go about sizing the Hot well /Cold well tank for chilled water system.
We want hot well /cold well tank for acting as buffer tank the tank shall have bifurcation up to 75% height so that hot well is around 40% and cold well is 60 % holding capacity.
The chilled water from hot well at 12 degree C is pupmped to chiller and returns to cold well at 7 degree C.
The 7 degree C chilled water is circulated to Air handling units in the Paper Mill and returns to hot well at 12 degree C .
Presently we have sized the tank for 3 minutes storage with 60% for cold well and 40% for hot well.
Is there any guideline or article on sizing of the tank.
We want hot well /cold well tank for acting as buffer tank the tank shall have bifurcation up to 75% height so that hot well is around 40% and cold well is 60 % holding capacity.
The chilled water from hot well at 12 degree C is pupmped to chiller and returns to cold well at 7 degree C.
The 7 degree C chilled water is circulated to Air handling units in the Paper Mill and returns to hot well at 12 degree C .
Presently we have sized the tank for 3 minutes storage with 60% for cold well and 40% for hot well.
Is there any guideline or article on sizing of the tank.





RE: Hot well /Cold well tank sizing for chilled water application
If the chiller turn down is good due to multiple compressors or variable speed drives,it may not be required.It looks like you may a have a steady load as it is a paper mill.
RE: Hot well /Cold well tank sizing for chilled water application
Presently the tank we have is 40000 Liters with 1000 L for hot well and cold well capacity of 30000 Liters.We have cold well volume more to ensure cold well overflows to hot well so that the chiller unloads depending on the load.The load variation is mainly due to the weather fluctuation and the load factor of the plant.
Now the Paper mill is in expansion and we are adding 600 TR VAM two numbers and all the chilled water shall be in common cold well and hot well tank.We want to combine the tank into a single tank for all the 1000 +300 +600 +600 =2500 TR so that with any chiller all the areas can be covered.
RE: Hot well /Cold well tank sizing for chilled water application
On another note with absorption chiller you need to careful with buffer tank sizing. Absorption chillers do not turn down well. Therefore they are meant for steady base loads only. If the chiller trips on chilled water temperature, the machine will go into a dilution cycle which can take about 15 ~20 minutes. It will easily be 30 minutes before the machine can be back on line. Your process may not stand the temperature fluctuation due to such shut downs.
RE: Hot well /Cold well tank sizing for chilled water application
My question is: If the absorption chillers do not turn down well and the load is so big in this plant, why use a tank altogether?
If the load is this large, just sequenc eyour chiller plant to the one or two chiller sneedd to meet the load. Why add controls, space, equipment and complications?
I understand the use of a buffer tank (are qe talking about a buffer tank here with hot/cold well language? hope I am still in the subject) would have its application when the system volume is less than the manufcaturer recommended volume (equipment too close to the plant being the case, not enough piping to hold water)
Thanks
RE: Hot well /Cold well tank sizing for chilled water application
Is this purely a comfort AC application or is there some process cooling also done ?
HVAC68
RE: Hot well /Cold well tank sizing for chilled water application
There is small quantity for process cooling also.
Earlier they were having only primary pump concept with expansion tank located at top most point of chilled water circuit. The primary constant flow pump had to be oversized and always had problem of chilled water flow in some units or other. Moreover more flow was being pumped than required in chiller jeopardizing the operation.
We have 1300 TR VAM(vapor absorption Machine) with hot well cold well tank of 40000 Litres with partition at 2/3 to ensure overflow is from cold to hot so that the chiller stars operating on part load whenevr the return (hot water temperature is lwo due to mixing with cold water.Currently adding two 600 TR VAM with AHU's etc. We want to go in for Masonry tank combining both existing 1300 TR +1200 (being added) +600 TR provision for standby.We have sized tank as 80000 Litres.