Phase Change Experts Req'q

Steves_pc · 16 Dec 2011 at 08:50

Hi Guys,

Fairly easy question really, do any of the phase change units have a temperature control? if not are there mods about to add such a facility?

Thanks :cool:

Steve

kitfit1 · 16 Dec 2011 at 11:46

If you are asking "can the idle temp be altered on the fly", the answer is no. All phase change units are built to handle a defined load. Why do you want to know ?

pyropetepete · 16 Dec 2011 at 12:40

You can have one built so it controle the temp of the head but cold boot & cold bugs are a thing of the past

kitfit1 · 16 Dec 2011 at 12:50

pyropetepete said:
You can have one built so it controle the temp of the head but cold boot & cold bugs are a thing of the past

No you can't. Four things control the evap temp, the length of the captube, the amount of refrigerant in the system, the size of the compressor and the size of the condenser. Once the system is built, the only control is the on off switch. A controler can be used to switch the computer on when the evap temp gets low enough, but that's all.

Steves_pc · 16 Dec 2011 at 15:09

Hi Guys,

Righto, 1st off it's not a project for a pc so cold boot isnt an issue, it's actually for some lab work to test/confirm the freezing points of stuff, so load wise it'd be from ambient donw till the test subject froze.

TIA
Steve

Was just a thought as most fridges and freezers have some degree of control.

pyropetepete · 16 Dec 2011 at 15:51

kitfit1 said:
No you can't. Four things control the evap temp, the length of the captube, the amount of refrigerant in the system, the size of the compressor and the size of the condenser. Once the system is built, the only control is the on off switch. A controler can be used to switch the computer on when the evap temp gets low enough, but that's all.

Wrong!

Captube is the flow rate to which the gas can then be boiled off!
The amount of gas controls the temp
Size of comp is one factor!

You can use a valve to control hotgas bypass to flod the evap with hot gas to keep it from a low temp!

Look on XS and BTUK (if it's up again). There are few system out there that do it. Fact there is a vid on the tube!

It's not going to be cheap but it's been done and can be done!

kitfit1 · 16 Dec 2011 at 17:40

Steves_pc said:
Hi Guys,

Righto, 1st off it's not a project for a pc so cold boot isnt an issue, it's actually for some lab work to test/confirm the freezing points of stuff, so load wise it'd be from ambient donw till the test subject froze.

TIA
Steve

Was just a thought as most fridges and freezers have some degree of control.

In that case then, you just need a freezer stat that will measure the temps you want to go down to. All it actually does is turn the compressor of when the target temp is reached.

pyropetepete said:
Wrong!

Captube is the flow rate to which the gas can then be boiled off!
The amount of gas controls the temp
Size of comp is one factor!

You can use a valve to control hotgas bypass to flod the evap with hot gas to keep it from a low temp!

Look on XS and BTUK (if it's up again). There are few system out there that do it. Fact there is a vid on the tube!

It's not going to be cheap but it's been done and can be done!

The basic function of the hot gas bypass is to keep the suction pressure above freezing during low load situations. As a means of controling evap temp during a "loaded" situation it would not even be "open", if it was, the temp would shoot up and spiral out of control.
In the clocking world of phase, they are generally only used in "Cascades".
Unless of course you want to sit there opening and closing the valve yourself.
A complete waste of time and unneaded in a single stage phase unit.