Cooling water drum

[mitch722]

Hello,

I'm trying to design a refrigeration system to cool down ~450L of water in a stainless steel drum radius 700mm, height 1m. The water will start at room temperature ~25 degrees C and needs to be cooled to ~2 degrees C (as close to freezing as possible).

The drum will be wrapped in copper tube carrying refrigerant and then insulated on the outside with 30mm of polyurethane foam. I can use the thermal conductivity of the foam to work out how much heat will be transmitted from the environment into the drum and hence how many "Watts of cooling" need to be applied to keep the drum at a stable 2 degrees C dependent on outside temperature.

I would like to use a single phase 240V max 10A compressor so the system can run off a normal household supply. I'm hoping to buy an off the shelf compressor/condensing unit like the 'Tecumseh Condensing Unit 1/2HP R404A MHBP Aet4460ZHR' to keep the cost down.

The questions I have:
- How can I calculate how many "Watts of cooling" this type of machine will supply to the drum? (and hence how long it will take to cool from room temp)
- Does refig coil length impact compressor size? Eg how many copper coils can/should I run around the drum to cool the water? I assume this is a similar problem to the thermal conductivity problem to that of the insulation above.
- Does coil diameter impact compressor size (I'm sure it effects refrigerant flow rate)? Eg what thickness copper coil would be required?
- Are there any suggested cost effect methods to increase thermal conductivity between the coils and the drum?

I'm hoping you guys can help me out with rough calculations. I'm sure there are many realworld limitations. I just want to make sure I'm spec'ing the system in the right ballpark and see how changing parameters will affect the system.
FYI I'm an electrical engineer so should be okay with physics concepts and maths but refig is way outside my norm.

This section is cut from the Tecumseh datasheet, does anyone know how to read the 'Capacity' Column?
refrig.PNG

[RANGER1]

Mitch,
To size you need to specify time period you can have to size up system.
Copper on outside inefficient, better on inside for full surface area.
Needs circulation
$$ limitations?
whats it for?
Actrol, Kirby etc can help with sizing components & equipment.
There is equipment you could just buy ready to go (water chiller).
You need Arctic license to work on it.

[Harper]

Hi mitch722!

To your question about the calculation:
Q=m*c*delta T
This results to a power of ~12kW. When you choose a compressor with 1.000 Watt it will take 12 hours to cool the water down.
About the construction I would also say, like Ranger1, that it is better to place the evaporater tubes inside the drum and ciculate the water.
When you wrap the copper on the outside, it is important to use thermal paste for a better efficency.

[RANGER1]

Here’s a bargain

https://www.machines4u.com.au/view/a...r-Unit/631090/

[adriansami]

You could sit this on top of a plant dolly (wooden platform with castor wheels for moving large plants around) take it anywhere inside or on to the patio. It's hot here in Texas so this is a worthwhile project. Thanks for posting.