Calculating weight of refrigerant based on pipe size

[sheet59]

Hi, Im looking for refrigerant pipe sizing software or chart that will also give me the weight of the additional refrigerant needed based on pipe size and layout for larger commercial split systems. Any help would be appreciated.

[frostedflake]

Greetings and welcome to the forum!

maybe you can give some more information for the engineers in the forum to help you, like what kind of refrigerant you using, the pipe sizing/lenght you working with and the operating temperatures and such.

have you tried using nomographs?

these charts can help you trace the pipe sizing you need, depending on the system capacity and also considering pressure drop and number of fittings, DuPont has a complete piping book you can take a look at.

DuPont refrigeration piping handbook
http://www.rapidshare.com/files/208819119/COMPLETE_Refrig_Piping_Handbook.pdf.html

you can also try to use CoolPack.
http://www.et.web.mek.dtu.dk/Coolpack/UK/index.html

:)

hope this helps

regards

[Brian_UK]

Most manufacturers will detail the extra weight of refrigerant required per metre/foot extra to the basic charge.

[Argus]

.





Your tag says that you are in the USA, but in Europe it is a legal requirement to check certain systems regularly for leakage. This is part of the 'F Gas' Regulations that we mention from time to time. You may find some calculation tools we have for this useful.

The leakage test frequency is dependent on the size of the system and containment weight of refrigerant. In order to determine an approximate containment quantity, the UK Govt. have sponsored a help desk (F Gas Support) and have a user's help page on the DEFRA web site. There is a set of calculation tools there intended for system owners to estimate gas quantities. Ignore the regulatory information, as it applies to the UK and the EU only - it's the calculator core information that you can adapt.

http://www.defra.gov.uk/environment/air-atmos/fgas/comply/quantity.htm

Read the PDF guidance sheet, then you can probably adapt the excel calculators for your own use.

It assumes that you already have a system in place and know the pipe and vessel sizes.

Nominal design pipe sizes can be obtained elsewhere or calculated. Larger systems may contain an indeterminate quantity that can only be assessed practically at site.




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[krio]

Any help would be appreciated.

1) LineSize TechniSolve- Quick refrigerant line size calculations. The Refrigerant LineSize program has been developed to allow the system designer to do a quick and accurate refrigerant line sizing with very little effort.
2) *****- The program for calculation of necessary quantity of a coolant for refuelling of refrigerating systems . :)

[amitsaxena]

Dear Krio,

I am not able to download the LineSize TechniSolve and *****, please send me

Moderator's note: Please use the PM facility


Your help will be appriciated.

Thanks
Amit

[nike123]

I am not able to download the LineSize TechniSolve and *****

Probably because they are supposed to be commercial and you need to pay for them.:rolleyes:
http://www.coolit.co.za/software.htm

[sheet59]

Thanks to everyone for your time and help. Please allow me to be more specific about my scenario. I am a plan and spec contractor in southern us where temps and humidity reach high 90s. Although we use manuf recom for pipe size based on length, lift, turns etc., there charts for adding refrigerant are often lacking specifics. My goal is to reduce or eliminate tech time spent adjusting charge. Some of our projects range from 50-150 split systems up to 20 tons. I could realize a significant increase in work efficiency if I could give my techs the tools they need to precisely weigh in the correct amount of 22/410. This would be especially helpful when completing projects in the winter. Already checking (still waiting) with Trane, Carrier and York. Thanks again for all your suggestions and help. I will eventually get around to researching each one.

[chemi-cool]

Amount of refrigerant in the system has nothing to do with the lines size.

Amount of refrigerant used should not exceed the volume of the receiver + a 1\4 of the condenser internal volume when refrigerant is pumped down.

[krio]

Hi to all!!

Amount of refrigerant in the system has nothing to do with the lines size.
Amount of refrigerant used should not exceed the volume of the receiver + a 1\4 of the condenser internal volume when refrigerant is pumped down.

If you look in the textbook, then:
Calculate the mass of the refrigerant gas is as follows:
Mzapr = ρх.а * (0,4 * Visp + kg * Vres + Vzh.m), where
ρх.а - the density of the refrigerant used; ρR22 = 1,3 kg/dm3, ρR404 = 1,04 kg/dm3;
Visp - internal volume of air coolers;
V res - the internal volume of the receiver cooling unit;
V zh.m - internal volume of fluid lines;
kg - factor Arrangement condenser:
kg = 0,3 for the compressor-condenser units without a hydraulic pressure regulator condensation;
kg = 0,4 using a hydraulic pressure regulator condensation (mounting the unit on the street or the

[chemi-cool]

;) Very nice..........

In real life, I dont believe it will work.

There are too many other factors to consider but thats only my opinion.

[desA]

^ Fair comment. How then, would one go about determining the correct system mass charge?

Surely there would be some level of calculation first, followed by a charge adjustment - based on some criteria?

[chemi-cool]

As I see it, it will be the receiver volume + about 1\3 of the condenser volume.

Thats the amount when the refrigerant is pumped down.

Why in the first place it is so important for you to calculate it?

I have never seen a design for a refrigeration unit with the gas weight. Fill it and weight the amount, much more simple.

Dry cooler unit will hold less refrigerant then a flooded one, long lines will influence it too, hot ambient will makes you use less, etc. etc...

[desA]

Why in the first place it is so important for you to calculate it?


Because I design heat-pumps for a living.

The typical way we determine a gas fill has been to compute an initial charge & go in a little light. We then add charge progressively & test the system thoroughly. This can be a major time-consumer in the development stage.

A more accurate method of determining the required charge would be wonderful. :)

[sheet59]

Because I design heat-pumps for a living.

The typical way we determine a gas fill has been to compute an initial charge & go in a little light. We then add charge progressively & test the system thoroughly. This can be a major time-consumer in the development stage.

A more accurate method of determining the required charge would be wonderful. :)
thank you desa, you are on the same line of thought I am. Saving time on jobs where the line length and rise varies over multiple systems and we must account for varying design perimeters. If some smart guy would figure it out so that contractors could use it, I would buy the software. It would defiantly save me labor.

[sheet59]

We are not talking about the same thing. Im talking airconditioning for people comfort. Sorry if I misslead you. Thanks.

[sheet59]

Thank you for your input. I believe after translating the units of measurement, it may be what I've been searching for. Thanks so much.

[desA]

^ It is the same thing when you get down to it.

As you would know, both heat-pumps & air-conditioning use the same cycle - we only worry about the hot end of the machine, aircon worries about the cold end... :)

So, any methodology that would assist in the calculation of refrigerant charge would help the whole industry that relies on the vapour compression cycle.

[sheet59]

^ It is the same thing when you get down to it.

As you would know, both heat-pumps & air-conditioning use the same cycle - we only worry about the hot end of the machine, aircon worries about the cold end... :)

So, any methodology that would assist in the calculation of refrigerant charge would help the whole industry that relies on the vapour compression cycle.
Yes, as employers who depend on finding productivity through ingenuity, this would or could be a milestone as it relates to cost saved and a job better done. Thanks.

[nike123]

Since gas state of refrigerant is many,many,many... times greater volume of liquid one, any error in gas/liquid ratio calculation is many,many,many...... times amplified when we calculate refrigerant weight in system, and that is, I suppose, main reason why we still don't have any decently accurate method, formula or software for weight calculation.

[desA]

Ok, fair comment. That's a challenge for me then - I'll work on developing a suitable gas-charge estimation program. I have all the relevant gas/liquid/2-phase prediction data available - that's the easy part.

The more difficult part would be to be able to estimate the relevant hold-up areas in the equipment - the pipes are a given.

If anyone would like to contribute thoughts & ideas on this, I'll gradually develop an application. No promises, no pack-drill, but I think it would be useful.

[desA]

Some feedback
I've been working on developing a first-principles refrigerant charge mass technique for an air-to-water heat pump system. It's actually not so easy.

Using the rules, based on a system operating condition, the final mass turned out to be over-predicted.

I'm now slowly bleeding the system off until the system begins to behave - & observing. The final runs will begin at low mass & then work upwards in steps of 100g.

The AWHP is a rather testy device, it seems - especially near the top end of the temperature operating range. Slightly oversizing the TXV (one orifice #) can cause some very unstable hunting at the high pressures.

[garybb]

wher can i find an easy to read chart

[Brian_UK]

wher can i find an easy to read chart
I use Google, try this one..

http://en.wikipedia.org/wiki/File:Electricity_use_by_lightbulb_type.svg

[bill1983]

excellent Brian, simple and comprehensive as should be expected from one as experienced as yourself. i found it most helpful and shall use it as an example for all my engineers.
thanks again. oh and bonne annee to you sir.

[Engineerdave]

Thanks to everyone for your time and help. Please allow me to be more specific about my scenario. I am a plan and spec contractor in southern us where temps and humidity reach high 90s. Although we use manuf recom for pipe size based on length, lift, turns etc., there charts for adding refrigerant are often lacking specifics. My goal is to reduce or eliminate tech time spent adjusting charge. Some of our projects range from 50-150 split systems up to 20 tons. I could realize a significant increase in work efficiency if I could give my techs the tools they need to precisely weigh in the correct amount of 22/410. This would be especially helpful when completing projects in the winter. Already checking (still waiting) with Trane, Carrier and York. Thanks again for all your suggestions and help. I will eventually get around to researching each one.

Been reading this thread. Very interesting and useful topic. This exact subject came up recently at work. A guy 'guesstimated' how much R22 a split system would need. Two trips to RSD later, he got it right.

Here's a pdf from the crew at McQuay that google found for me. maybe it'll help.

w w w. mcquay. com/ mcquaybiz/ literature/ lit_systems/ AppGuide/ AG_31-011_120407.pdf

You'll have to delete the extra spacing in the url address, I'm too new to this site, it won't allow me to post a link yet.

Dave

[yairgre]

Hi All,

I have read your comments. However it seems I still don't understand how to calculate the total refrigerant mass i need in my system.

If I have a system composed of Compressor, Condenser, Evaporator. How do I calculate the total refrigerant mass [kg] i need in my system?

Thanks