Refrigeration 101

[desA]

If we monitor the subcooling while observing the sightglass, on a wide variety of systems, we will find that the last vapor bubbles disappear at about 10-15F/5.5-8.5K subcooling. Thus we can identify the SLP by measuring the subcooling at the receiver outlet, ensuring that (with all else functioning properly) we are neither undercharged, nor overcharged.

How does SLP concept this relate to the concept of 'liquid cooling'?

Where : LC = Tc,sat - Txv,in

A few points to note:
1. LC will vary as Tc,sat varies over the cycle range;
2. The allowable subcooling (SC = Tc,sat - Tc,exit) differs for different condenser types. SC of 5.5-8.5K will be a problem for plate condensers (2-4K), & air-cooled condensers (~ 0K).
3. In the quest for increased SC, be careful of not pushing up Tc,sat. Basically, Tc,sat levers up off the cooling medium temperature. There is a happy balance point for each system.

[Gary]

How does SLP concept this relate to the concept of 'liquid cooling'?

Where : LC = Tc,sat - Txv,in

A few points to note:
1. LC will vary as Tc,sat varies over the cycle range;
2. The allowable subcooling (SC = Tc,sat - Tc,exit) differs for different condenser types. SC of 5.5-8.5K will be a problem for plate condensers (2-4K), & air-cooled condensers (~ 0K).
3. In the quest for increased SC, be careful of not pushing up Tc,sat. Basically, Tc,sat levers up off the cooling medium temperature. There is a happy balance point for each system.

There is no doubt an ideal balance for each specific system... and I would not recommend SLP at the condenser exit for any system.

What I have found works reasonably well for refrigeration systems in general is to have the SLP in between the condenser outlet and the TXV inlet.

Generally, I would want the SLP to be near the receiver outlet and this is where I measure the SC. I suspect this is the very reason sightglasses are usually mounted near the receiver outlet.