Pro/Forums - View Single Post - Need adcice on building a phase change evaporator

redleader · 06-09-2004, 08:34 PM

This is an extension of my last thread where it became clear that using a swiftech block as an evap was not an option. In that thread it was pretty obvious that i didn't really understand the pressures at work in an evap. So heres what I need to build a block capable of:

*Must be able to withstand at an absolute minimum 200 PSI of inside pressure. Ideally more in case i ever want to switch to a higher pressure refrigerant and for safety in all cases.

*Must be able to return a small amount of liquid oil to the compressor.

*Must have a large enough internal surface area for ~150w of heat to be transfered to the refrigerant during phase change.

My current idea:

Modify an old Maze 2 classic block:

First step would be to unsolder it. Then I'd need to clean it out and braze it together and replace the barbs with fittings for a gas line and a cap tube. Finally I'd bolt on a socket A to 754 conversion bracket. As an added bonus the bracket would allow me to bolt the block together in the four corners, further increasing its strength.

Again though this brings me back to pressure. I remember Dangerden pressure tested the old maze1 blocks which were very similar at 1000 PSI. Since I'll be brazeing and bolting I think i'll hold at least that much pressure, but i have no concept of what high pressure like this really does to a joint. Does this seem reasonable?

Also, about brazing. Is there some special braze I should be getting, or should i just go with the regular stuff used in AC systems? Will ordinary copper braze work when i braze in brass fittings? Finally does braze use flux? I've only worked with plumbers solder (though i have a MAPP torch).

Edit: Noticed i misspelled the topic sentence

06-09-2004, 08:34 PM	#1
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	Need advice on building a phase change evaporator This is an extension of my last thread where it became clear that using a swiftech block as an evap was not an option. In that thread it was pretty obvious that i didn't really understand the pressures at work in an evap. So heres what I need to build a block capable of: Must be able to withstand at an absolute minimum 200 PSI* of inside pressure. Ideally more in case i ever want to switch to a higher pressure refrigerant and for safety in all cases. Must be able to return a small amount of liquid oil to the compressor. Must have a large enough internal surface area for ~150w of heat to be transfered to the refrigerant during phase change. My current idea: Modify an old Maze 2 classic block: First step would be to unsolder it. Then I'd need to clean it out and braze it together and replace the barbs with fittings for a gas line and a cap tube. Finally I'd bolt on a socket A to 754 conversion bracket. As an added bonus the bracket would allow me to bolt the block together in the four corners, further increasing its strength. Again though this brings me back to pressure. I remember Dangerden pressure tested the old maze1 blocks which were very similar at 1000 PSI. Since I'll be brazeing and bolting I think i'll hold at least that much pressure, but i have no concept of what high pressure like this really does to a joint. Does this seem reasonable? Also, about brazing. Is there some special braze I should be getting, or should i just go with the regular stuff used in AC systems? Will ordinary copper braze work when i braze in brass fittings? Finally does braze use flux? I've only worked with plumbers solder (though i have a MAPP torch). Edit: Noticed i misspelled the topic sentence Last edited by redleader; 06-11-2004 at 05:52 PM.