I am having trouble cooling water at the rate that I need.

[Justinaray]

I need a system that will produce 7.5 liters per minute of water at 5 degrees Celsius and at standard water pressure. The best equipment I can seem to find produces 1.86 liters per minute and I cannot find how cold the water becomes. Can anyway help me find the equipment needed to produce this? Or at the least point me in the right direction. Thank you!

 

[zdas04]

Your post raises so many more questions than it answers.

By "standard water pressure" I'm assuming that you mean you are at the mercy of a municipal water system and can't install your own pump for whatever reason? This matters because the differential pressure across a water chiller can be very large and then there won't be enough residual pressure to overcome friction at your target flow rate.

What temperature is your supply at? Does it vary from season to season? It matters.

What are you cooling with the chilled water? The equipment needed to get to your target temperature and flow rate is pretty dependent on the pressure drops in the system (you have a different chiller if you are cooling a single meat locker than if you are running cooling to a dozen air handlers for space cooling.

Do you have any power limitations? Not all chillers are created equal and you can get a pretty wide range of required power for seamingly the same job.

How about space limitations?

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[Justinaray]

I apologize for the vagueness. I am an electrical engineer assigned to a mechanical job so many of these aspects had not occurred to me.

I would be able to install a pump if needed and not completely limited to the municipal water system. I just need it to produce water at standard water pressure, because it will be used for testing with dishwashers.

I believe the water supply in the lab is around 38 degrees Celsius. I would prefer something that could be powered through a standard U.S. wall outlet.

The system needs to be able to fit into a reasonably small lab, but it doesn't have to be portable or incredibly compact.

 

[LittleInch]

Hmmm,

I've just run some first order numbers here base do your 7.5 litres/min reducing water from 38 to 5C with a heat capacity of 4.18 J/cc/K, gives me a heat rejection rate of over 17kW. In chiller terminology this equates to 5 tons of refrigeration. I ton = 3.5kW heat rejection.

Practical value for kW input (compressors, fans etc) seems to range 0.5 (ideal big unit) to >1 kW/ton. So you're looking at about 5kW power input and a pretty large condenser with quite a high air flow to get rid of 17kW. I think that's abit beyond a "standard" power socket or domestic chillers

You are definitely into the commercial range of chillers here I think - try mr google for your nearest vendor, but I think you'll be a bit surprised by the cost and size.... especially if your 7.5 l/min is fairly continuous over a period of time greater than a few seconds

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[zdas04]

"Standard water pressure" is a slippery concept. My dishwasher has a stated minimum (I think it is 30 psig) and maximum (seems like it is 80 psig, but I'm not certain) so I assume that they tested at 20% below minimum and 20% above maximum. For consumer equipment you are going to want to install your own pump to allow you to test the boundary conditions independent of municipal supply.

Your supply water will vary considerably from winter to summer if you are outside of the tropics. Typically you are going to want to size your chiller for the warmest reasonable supply temperature.

Do a search for "Industrial Water Chillers". There are hundreds of manufacturers. Your heat load is something like 18 kW so you are probably not going to be able to just plug it into a wall outlet.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[zdas04]

LittleInch,
Were you looking over my shoulder while I was typing? Reassuring that we came up with the same numbers and same conclusions.

For his application I'd probably use municipal water instead of air to cool the process (smaller, quieter unit, but the cooling water can get expensive)

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[Justinaray]

Cost is not a big issue for the project, because the project is for a well established company. I will most likely be able to get a 18KW load and will start looking into industrial water chillers. Thanks for the help!

 

[LittleInch]

Zdas04 - I had to go look up what a "ton" of refrigeration was, but now I know(!)

I am a little surprised by how hot the "cold" water supply is in his lab - Glad I don't work there...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way