help building chiller

[kayl]

i am hoping to build a chiller

I currently have this compressor its out of a 1750w air conditioner

do i need to add oil or do a oil change onit, is it best to do it before I braze it into the chiller?

[kayl]

In the original unit the condenser was a total length of 15.48m or 51.6 foot long. The evaporator was 6.6m or 22.2 foot long.

I want to reuse the condenser and make a copper coiled evap and stick it in a 10 litre esky (can somone recommend what size esky would be best as a res)?

Using this link

http://www.benchtest.com/calc.html#OC



I estimate the cpu to be around 170w and I will also have a GF4 ti4200 (ive read its about 40w)

So in total I will have around a 210w load, how much extra should I include for losses

What size length copper pipe should I use and what captube should I use?

[kayl]

the suction line has broken off the condenser so I will need to rejoin it again. I thought of cutting it here and brazing it here.

Is this a good idea whats the best way about doing it?

[kayl]

sorry cutting it here and rejoining

[Gary Lloyd]

Your evaporator is designed to absorb 1750 watts of heat, but you only need to absorb 200 watts of heat, therefore the evap is way more than enough.

The condenser must dissipate the heat absorbed by the evaporator, plus heat of compression, which adds about 25-50%, therefore the condenser is also way oversized.

The cap tube needs to flow enough refrigerant to absorb the heat load, so it is also way oversized.

Note that all of these are dependent upon heat load, not compressor size. We can design the entire system without knowing what size compressor will be used.

The first step is knowing what the heatload will be.

Next is selecting the evaporator.

Then deciding what refrigerant to use.

Then selecting the cap tube.

Then the condenser.

Then the compressor.

Whether the oil must be changed depends upon what refrigerant you will use.

The res should be as small as possible. The more coolant, the slower the pulldown.

Yes, you can cut into a return bend in the condenser and braze it together, bypassing part of the coil.

[kommando]

Originally posted by Gary Lloyd
Your evaporator is designed to absorb 1750 watts of heat, but you only need to absorb 200 watts of heat, therefore the evap is way more than enough.

The condenser must dissipate the heat absorbed by the evaporator, plus heat of compression, which adds about 25-50%, therefore the condenser is also way oversized.

The cap tube needs to flow enough refrigerant to absorb the heat load, so it is also way oversized.

Note that all of these are dependent upon heat load, not compressor size. We can design the entire system without knowing what size compressor will be used.

The first step is knowing what the heatload will be.

Next is selecting the evaporator.

Then deciding what refrigerant to use.

Then selecting the cap tube.

Then the condenser.

Then the compressor.

Whether the oil must be changed depends upon what refrigerant you will use.

The res should be as small as possible. The more coolant, the slower the pulldown.

Yes, you can cut into a return bend in the condenser and braze it together, bypassing part of the coil.

Oh great there goes my day trying to build a chiller.

Why so much steps, can't you kind of link the steps in some way?

Damn my mate is lazy, i want my compressor!

(it is powerfull :))

[Gary Lloyd]

Your evaporator is designed to absorb 1750 watts of heat, but you only need to absorb 200 watts of heat, therefore the evap is way more than enough.


Okay, I need to qualify this. There is a very large difference between the temperature of the air and the temperature of the refrigerant in an A/C. This would be undesirable in a chiller. In order to minimize this, we would want more evaporator surface area. In other words, while the evaporator is technically oversized, such oversizing is advantageous in our chiller evaporator.

[kayl]

Ok so I have a total load given off by the computer totalling about 210w

So for the evaporator I was hoping to do a similar design like the one below in the picture. What size and length copper tubing should I use?

For the refrigerant I hope to use r22. for now I will get a fridge tech to charge the system, or maybe I may look into recovering some Freon in a gas barbeque once I all the equipment..

Then finally what size captube should I use.
Also now that I have decided on all the rest of the stuff I guess I need to know what length I should cut the condenser down to?


I measured the current draw on the compressor with nothing connected to it and it draws 2A’s and the mains are 240v here so it consumes about 480w, can this give an indication of what size the compressor it is?

[water_cooler 20]

lol nice pic:D

[kayl]

is there any way that i can recover this gas and then re-use it.
its a 6,500 btu unit so i was thinking of using the compressor as a vaccume pump it uses 846w
what size compressor would you say it is?

[water_cooler 20]

i think that would be 1/2 HP

[kayl]

anthor option i was thinking of was that my brother is a mechanic and he said he can get me some R134A.
what percent of R290 would be good to add to the R134A to decrease the overall boiling point of the mix, while still tryin to keep the mixture safe, i dont want a fire

R134a (-26deg) and propane from propane torch bottle (~-42)
what sort of boiling point to you think i could achieve?