Aqua Cool Cooling Towers

[iken]

Can any body please advise contact details for the Manufacturer (not a supplier) of these Cooling Towers.

My problem is that I have a supplier stating that these towers (MSS141A) will operate fine under these conditions.

Design Flow = 73 l/s
EWT 35 degC
LWT 29.5 degC
Ambient WB 22.5 degC
Heat Rejection 1700kW

This is not the problem. The prblem is there are 3 towers (or would be), and all towers will have water flow regardless of the chiller operation. Here's the problem. When only one chiller is operating, there would only be 64 l/s to serve all Towers (21.3 l/s each). Under this condition, we have been advised the towers will operate fine, and would expect that the tower efficiency (related to outpt) would be around 80%.

These numbers do not seem to be correct - reduce flow to 30% design, and towers will only reduce to 80% design.

Any help would be greatly appreicated.

 

[quark]

Here is a list of cooling tower manufacturers from CTI and you will find the manufacturer details.

http://www.cti.org/directories/manufacturers.shtml

Have you checked the data you gave? Approach of 7⁰C is quite high and I never experienced it.

When you have 1/3rd flow, you always have a chance to switch of water supply to other two towers.

Just go through this link for a better understanding about cooling tower design and performance.

http://www.cheresources.com/ctowerszz.shtml

Regards,

 

[imok2]

Why not isolate 2 towers when operating 1 chiller? Have full flow to one tower or am I missing something. If each chiller has it's own condenser pump and you have 3 active towers you should get all the water you need for 1 chiller, however it seems to be a waste of energy. Remember if these towers are on a common supply and return header then the equilizer lines are critical and must be sized accordingly

 

[iken]

The design figures are correct (all as specified).

The option of isloting towers was not included. The supplier advised the consultant that you would need control valves. I disagree for two reasons. One, that the performance must be greatly effected by a lack of flow, but also if only one coolingt tower fan is operating, and water passes trhough all, then this cooled water is then mixing with water from the other two towers. This would result in higher temp water returning to chillers, and hence more towers operating to compensate this (all towers all the time).

Thanks for the links, I will look at these and track down the manufacturer (for their input).

 

[quark]

Better option is to have control valves on supply and return of cooling towers as suggested by your supplier. I operated a battery 6 cooling towers in this way.

 

[iken]

quark, unfortunitly, this was not suggested by the supplier. He advised control valves would not be needed. This is however what we (the contractor) feels the best option.

imok2, this is what we believe should happen, but the consultant still believes (due to being advised by local supplier) is unnecessary.

 

[SAK9]

Iken,

I asssume you have dedicated cooling tower for each chiller.When you operate only one chiller,part of cooling water will be diverted to non active cooling towers as well.This would obviously mean that the water leaving from the non active towers will be higher than 29.5C leading to inefficient operation of the chillers.

You would need to provide motorised isolation valves at the inlet of each cooling tower.No such valve is required on the suction line as the tower water levels will be maintained through an equaliser pipe.

The above arrangement may not be necessary if your plant operator is careful enough to isolate the non active towers by manually closing the valves.

 

[imok2]

Putting isolation valves is more expensive, however that is state of the art in my estimation, cheap can become more expensive.

 

[iken]

SAK9, imok2,

exactly my points to the consultant, but unwanted.

 

[lilliput1]

You may minimize enery use by staging cooling tower fan controls. Say all off then low speed on 1, then 2 then 3 cooling tower fans. Then high on one + (2) low etc till all on high. If cooling towers will operate in wnter or if chillers are limited on the minimum condenser water temperature, provide cooling tower bypass valve. Control to either slowly open full or slowly close fully (not modulating). Provide wide temperature range for its action to not be cycling (say open full when water temperature is 60°F and below, and close full when water temperature is 80°F and above and not to open till waterhas dropped down to 60°F). You should not modulate to avoid drips that can ice over.

 

[jherbert]

iken,

slightly off-topic, if I have read this right, you have no isolation valves for each tower?

- how does one isolate a tower for inspection, maintenance and cleaning?

- no bypass is mentioned either, that limits options for future chemical treatment, since only treatments that are fill friendly can be used.

regarding the design approach, I guess the designer is looking to for a philosphy whereby all towers run, even at low load, to lower the condenser pressure and recoup savings on compressor power. In principle that is a great idea if it is properly designed. Still need those valves for maintenance and as mentioned above CT fan control.
Sounds like your designer is out of his/her depth. Got a schematic?

 

[iken]

There are isolation valves at both the inlet and outlet of each tower.

There is also a bypass line between each tower.