Superheat and Subcooling

[honglo]

If, SH = (INWBT * 3 - OSDBT - 80) /2, is there a formula for SC?

[Diceman]

E=mc-squared

It's the only formula I know off by heart.

[spotts]

1 part oxygen.


Black powder is made from sulfer, saltpeter and charcoal.

Thats some I know.

[honglo]

OoooooK,
however, Diceman, I don't think it is -squared....
and spotts, if you don't get the percentages right you won't get a boom with the blackpowder. (been there, done that)

Come on now..... surely there's a mathamatical formula for subcooling!!!?????

[Diceman]

See, I can't even get that one right.
How about ummmmmmmmm
8am+work-all-day=5pm+time-for-beer.
Or 8am+wad=5pm+tfb

Is that any help?

[glitho]

hmmmm I always thought it was SLT-SST=SH and SCT-LLT=SC

[honglo]

glitho,
Your right in using that to discover what it IS.... I'm looking for the formula to discover what it SHOULD be.

[Senior Tech]

Originally posted by Diceman
See, I can't even get that one right.
How about ummmmmmmmm
8am+work-all-day=5pm+time-for-beer.
Or 8am+wad=5pm+tfb

Is that any help?

Liar, Liar, pants on fire...we know you quit at noon and start drinking at one...

[Diceman]

Sometimes I wait till 2.

[len]

superheat=the amount of rubber you are leaving on the road from the burnout of your tires from the last job you did.now subcool=is the amount of beer you can drink to start cooling off.great equation .

[midhvac]

Aw crud. Be real careful. Every time somebody starts one of these threads about s_p_rh__t (didn't want to spell it out), 3 unnamed individuals here get into a major slugfest. Maybe this one will be different because it includes subcooling.

[midhvac]

Honglo, I kinda don't think there's going to be such a formula for sc, because unlike sh, there are different sc's for different txv systems, which is what I'm assuming you're going to checking the sc on.

[sonofdawra]

Originally posted by honglo
If, SH = (INWBT * 3 - OSDBT - 80) /2, is there a formula for SC?


Where did this formula come from?

[honglo]

It was taken from this forum but I forgot to whom goes the credit. I was just wondering if there were a similar formula for subcooling.

[CityHvac]

Originally posted by honglo
It was taken from this forum but I forgot to whom goes the credit. I was just wondering if there were a similar formula for subcooling.


honglo.....give the credit to lmtd..he is the one that tossed that superheat formula out here...I think he has one for SC. If you do the search thing, You will find it.

[honglo]

I wouldn't doubt it. LMTD has been a very BIG help to me in the not so distant past. We should all be proud that we have people like him on this forum.
I am not one to throw out (flowers) like that to just anyone but I humbly listen when he (speaks). I've only been at this stuff since 1973 and his knowledge puts mine to shame.
I've done a few searches for this info and it is difficult to narrow down the parameters without coming up with thousands of hits or nothing at all.
I'll keep trying.

P.S. this (subcooling formula) is no biggie, I just promised myself a long time ago I should try to learn something new about the business every day. (That keeps it from getting boring while allowing me to run circles around a high percentage of competition. Unfortunately I have found that for the most part, the more you know; the less you make. Go figure!)

[bigtime]

I would humbly defer to LMTD on this or any refrigeration cycle question, but I think subcooling should usually be around 15deg. I usually don't worry about it. I am more concerned about the head pressure and suction pressure. If the pressures are right, the subcooling will be okay whatever it is. If you have to much subcooling, the condenser is full of liquid, and the head pressure is to high. I subcooling is to low, you don't have enough gas, and the suction is to low.

[espock]

Originally posted by lmtd
... If I design a coil for 20 over ambient and ten degrees of subcooling, the line leaving the condenser will be 10 degrees over ambient. If I were to charge the system to 15 degrees of subcooling, that does NOT mean the line would be 5 degrees over ambient, in fact, it is not going to complete that task at all. You would still find your line some where near 10 degrees over ambient, but your saturation temp would be more than 20 degrees over ambient.

What's the relation/significance of "coil design for X F over ambient" to the "achievable" SC ?

[frozensolid]

Some Kramer refrigeration condensing units use two sight glasses for determining correct charge. One is on the inlet of the receiver, and one on the outlet. Their method is to clear the outlet glass, while leaving the inlet glass flashing. The receiver inlet is below the condenser outlet. The liquid exiting the condenser is sub cooled.

The flashing sight glass demonstrates liquid is not backing up in the condenser. The thermometer shows the liquid is sub cooled. This leads me to believe sub cooling is not about how much liquid is in the condenser. It’s more about how much heat it lost before it left.

Is this correct?

[honglo]

Thanks for the info lmtd!
All this time, I thought proper subcooling was only (obtained) so the metering device wouldn't get any flash gas that would cut it like water through a leaky faucet. I didn't know that units were actually designed with a particular subcooling in mind.
I put a 2.5 ton compressor in a Goodman CK60 at my house after the original 2.5 ton unit was bashed by hail. It sounds like your explanation addresses compressor capacity vs condenser volume and would apparently have something to do with the funky subcooling readings I am getting. What reasoning do they use to (decide) on what subcooling to design around? Will a higher subcooling design always deliver a higher effeciency? If so, does that place a limiting factor on the maximum subcooling design due to unit cost? (Higher subcooling, larger use of material to make the condenser)? Or does the higher subcooling designs have nothing to do at all with effeciency?

[espock]

LMTD, If I understand correctly, at "designed conditions", the head pressure which translates to the saturated temp of the hot gas is what you called designed SCT (am I correct ?). The coil is designed to remove some amount of heat and results in LL temp which translates to SC. Now if ambient is higher than "designed ambient" -> less Q transferred at the coil -> higher LL temp -> lower subcool (supposedly). But this would also result in less liquid and more space to cool in the coil -> lowering LL temp -> raising SC. So the net effect is that SC stays fairly same.

[Edited by espock on 09-09-2004 at 10:44 AM]

[sodadude]

Originally posted by len
superheat=the amount of rubber you are leaving on the road from the burnout of your tires from the last job you did.now subcool=is the amount of beer you can drink to start cooling off.great equation .

Good one Len. How is your boss doing?

[len]

sodadude hes doing good,just got transferred from ma.general too r.i.rehab.has to learn how too walk and talk again,it will be several more mos.before hes out and about thanks for asking.

[cde72]

I cannot believe you said that bigtime.... your pressures could be peachy with a sub-cooling low OR high...

[TB]

Originally posted by honglo
OoooooK,
however, Diceman, I don't think it is -squared....





I gotta back Dice on this one.

E=MC^2 it is, and E=MC^2 / 450500 is the energy of a bullet impact

where:
E= energy in foot pounds
M= mass in grains
C= velocity in feet per second

now where is that 9mm thread