TEV and cooling loss

[epion2985]

With a tev the lowest temperatures would be right outside the orface within the TEV right? So would a tev setup with the valve pretty much within 1" of the evap be much worce then a capillary set up where the end of the cap tube is inside the evap right on top of the base? I would think so but I wanted to ask anyway. And if yes are we talking about evap temp difference of like 1-2 degrees or like 10-15 degrees?

[jinu117]

With a tev the lowest temperatures would be right outside the orface within the TEV right? So would a tev setup with the valve pretty much within 1" of the evap be much worce then a capillary set up where the end of the cap tube is inside the evap right on top of the base? I would think so but I wanted to ask anyway. And if yes are we talking about evap temp difference of like 1-2 degrees or like 10-15 degrees?

Errr... granted insulated as it should be... I see no reason why there will be much of loss in temperature. It isn't like in evap where you are cooling something. Only thing would be you wouldn't want to put subcooling on that discharge from TEV. It would be before TEV in this case.

[epion2985]

thanks :)

The way I looked at it was that the refrigerant boils, taking heat with it. And if it boils in the tev then thats what it will take the heat from.

I did not consider the fact that the refrigerant now as a gas is still at the temperature it evaporated at and is traveling in to the evap, so given no loss due to good insulation it should stay at the same temperature untill it hits the evap.

thanks again

*point on the subcooling taken. I have thought about this too earlier and came to the same conclusion.

[expansionvalve]

You really have nothing to fear, a tev withinin an inch of evap will loose you nothing, the liquid leaves the outlet of tev as a liquid and boils into gas inside the evap, the outlet temp maybe actually marginally higher than the boil point inside evap, the coldest part will be where the liquid boils fully and in a well set up system this should be inside the evap.

[epion2985]

You really have nothing to fear, a tev withinin an inch of evap will loose you nothing, the liquid leaves the outlet of tev as a liquid and boils into gas inside the evap, the outlet temp maybe actually marginally higher than the boil point inside evap, the coldest part will be where the liquid boils fully and in a well set up system this should be inside the evap.

ah! so my initial conclusion had some truth to it. I thought the coolest part will be where it boils off but I wasnt sure. Awsome. Thanks.

[epion2985]

would be better if you have a TEV > evap setup.

1. Have the piping from the TEV to the evap the same diameter as the TEV exit end.

2. Have the piping from the TEV to the evap much smaller then the TEV exit end. (so the pressure drop would not be so great, some refrigerant would boil off but some would make it in liquid state to the evap and boil off there maybe with this option? resulting in better temperatures?)

reason I ask is the end of a TEV:
http://www.rparts.com/Catalog/Major_Components/valves/txvs.asp

is 1/2" male flare outlet. It seems that from the orface to 1/2" piping thats quiet a pressure drop and would result in alot of refigerant boiling off in that piping rather then the evap. Am I tottaly of my rocker or is there a valid reason for concern here?

[epion2985]

to add another question, is the piping after the condenser 100% flooded with liquid refrigerant or is there still alot of gass in it untill it hits the TEV? I read alot of condensation happens in the capillary but with a TEV you dont have one.

[wdrzal]

condensation dosent happen in the cap tube. both require a liquid head to operate properly

[epion2985]

so the space in the piping after the condenser 100% filld with refrigerant in liquid state?

[epion2985]

I am wondering is the space in the piping after the condenser 100% filled with refrigerant in liquid state because I am not sure how to split it up. If it is then I can just have a 1/2" piping from compressor then cap it, drill 3 holes in the cap, braze 3 1/8" lines to each TEV and done deal, if its not all liquid then we have a problem with having more liquid go in one like then the other so plasement etc etc with acordance to gravity etc etc makes a big difference.

[wdrzal]

It depends on the charge ,while a liquid head is required,how much liquid is present in the liquid line is determined by the charge,pressure &sub-cooling.

it can be from the minimium liquid head in front of the tev to the liquid line and part of the condensor being full.

being new I would recommend you build a single cab tube rig until you get familiar with building a rig, don't over reach

[epion2985]

If I fail I fail, then try again, nothing to loose.

[wdrzal]

its not about failing but learning how to succeed!!!!

[epion2985]

Well thats a personal preference. The desiered result is success but falier is good too, teaches you alot. I never failed and not learned something valueble form it.

Anyway, my biggest issue is trying to split up. The problem is the pressure drop. If you have 1/2" piping and then you split it 3 ways you better split it up to something that adds up to 1/2" or less. If you have 1/2" piping and you split it up in to 3 1/2" lines then at the place of the split you will have a big pressure drop, and that kind of screws things up since you want the pressure drop to be in the evap/TEV atleast.

I was thinking about splitting it up right after the compressor, its still in gas state so to split it evenly should be easy, unlike liquid. But you still get the drop in pressure, going down to 1/3 of the original still.


If you do it after the condencer then you still have the pressure drop when you are going from your 1/8" to 3/8" male flare TEV inlet.


So for this to work the refrigirant at X pressure comming from the condenser though Y" pipe, being split up in to 3 Z" lines, then each Z" line opens up to the Y" line (assuming the compressor piping and the TEV inlet are both Y") so now the pressure in the TEV inlet is X/3, so for this to work refrigerant at X/3 needs to remain in liquid state. oh boy...