what else i have to measure or evaluate in a mixture refrigerant for to improve it?

[mebluna]

Hello everybody!:)
I am María Elena... I have some questions, if you can help me, thanks.
I would like to know more about what specific caracteristics make a refrigerant the best. I need to improve some mixtures of refrigerants. I have been changing the composition of the mixtures and see how change the thermodynamic properties, sometimes it works, but not like i want. I have a problem, for example if i have 3 mixtures with the same behavior and aparently the same properties but it works different in the same system.
I want to know if i have to consider more that just the properties of the refrigerant or something else??? I am talking about that i will compare the refrigerant in the same system and in the same conditions to see which is better. I can determine the thermodynamic properties for each mixture that i prepare but isn´t possible to make experiment with 100 mitures...

Problem: After i made an experiment desing i have 3 good mixtures with similar properties in theory, i mean similar delta H, curve P Vs T, and similar density and viscosity but when i went to the laboratory happened that i had result so diferent, so i thought i have to evaluate something else in adition to this properties. What do you think about it?
i am a novate in this area and i am learning about this interesanting topic, so let me know if you have some information for to read or if i can talk with you for a while if you are an expert and can help me solve my questions.


so, what can i check or look in a mixture refrigerant to make it better in a specific system?

Maybe you don´t know everything, but i just need some information, if you have an article or paper please send me it to my mail or add me to your messenger: mebluna@hotmail.com (mebluna@hotmail.com) THANKS!! =)

[Peter_1]

Mebluna, welcome on this forum.
Why you want to make new mixtures and for what purpose?
All the available components are made for traditional refrigerants.
I think that calculating the behavior of a mixture is almost impossible. You will need to test it in a real lief situation.
Personally, I think that the chemical manufacturers have huge laboratories to find the perfect mix for a certain application.

[mebluna]

Thanks Peter, i have been working on it for a company that want to improve its mixtures, and it is because i have been making my thesis project for my master degree in this topic also.
We have been calculated the behavior with a software which made it with an excelent accurate and confidence, we have checked it with experimental information later. Many properties can´t be measure but you can obtain it indirectly considering mathematics ecuations and a good program. The ideal for to have the total accurance and confidence about the final information could be to test all the mixtures in a real lief situation, i agree whit you, but you know that it is imposible and it isn´t an option for a company economically viable. For the money and the time, i don´t want to make experiment for to do it, i want to design it, you know conducted experiments. So, i have been trying to design the experiment before make it, i mean i want to test only the mixture for which i hope to have a good behavior on the system, for that i use the simulation software. I told you that sometimes it works. The experiment´s design works when i have a good variable to measure (variable response like pressure vs temperature, H, Density etc). Now this is my problem, because i think i need to find or consider anothers variables to measure beside entalphy, viscosity, density, volume, presion etc. the question is what else i have to consider for to evaluate a mix as the best? I am asking you because i think it have to be related to the system beside the properties or something like that...

You said...
"Personally, I think that the chemical manufacturers have huge laboratories to find the perfect mix for a certain application." Yes i think so, my questions is how or what look them in a mixture? ;)...

Thanks and greetings,

María Elena

[mebluna]

Thanks Peter, i have been working on it for a company that want to improve its mixtures, and it is because i have been making my thesis project for my master degree in this topic also.
We have been calculated the behavior with a software which made it with an excelent accurate and confidence, we have checked it with experimental information later. Many properties can´t be measure but you can obtain it indirectly considering mathematics ecuations and a good program. The ideal for to have the total accurance and confidence about the final information could be to test all the mixtures in a real lief situation, i agree whit you, but you know that it is imposible and it isn´t an option for a company economically viable. For the money and the time, i don´t want to make experiment for to do it, i want to design it, you know conducted experiments. So, i have been trying to design the experiment before make it, i mean i want to test only the mixture for which i hope to have a good behavior on the system, for that i use the simulation software. I told you that sometimes it works. The experiment´s design works when i have a good variable to measure (variable response like pressure vs temperature, H, Density etc). Now this is my problem, because i think i need to find or consider anothers variables to measure beside entalphy, viscosity, density, volume, presion etc. the question is what else i have to consider for to evaluate a mix as the best? I am asking you because i think it have to be related to the system beside the properties or something like that...

You said...
"Personally, I think that the chemical manufacturers have huge laboratories to find the perfect mix for a certain application." Yes i think so, my questions is how or what look them in a mixture? ;)...

Thanks and greetings,

María Elena

[The MG Pony]

R&D get some good scales and keep close track of your mix then fireing a bit of each started from your bas amount to tweak it to the performance you want.

In other words: Take your best designed mix and charge the test system with it.

Take all the single part gases that are in your mix and set them up in a manifold rig so you can let it in the system while running, have a high quality messuring device to weigh or indicate amount added for each cycliner.

Once you have a base line data for the rig start adding the verious gasses untill you get your desired resualt.

make a new OEM of the now adjusted mix and test for consistancy. Now patent and sell :)

[Peter_1]

... the question is what else i have to consider for to evaluate a mix as the best? ....
Best mix will be that mix which will give the highest enthalpy versus the lowest absorbed power by the compressor, so a system running with the highest COP.
The closer you can come by NH3, the better.
This all falling within the specs of the compressor manufacturers (not too high discharge temperatures and condensing temperatures which gives some safety margin when it becomes warm outside) but this will be not a problem I suppose.
Don't forget the oil managment in the whole system.
The ideal for me should be reaching the properties of the good old refrigeants R12, R502 and R22 (which is almost at the age of retirement now:p )

[mebluna]

R&D get some good scales and keep close track of your mix then fireing a bit of each started from your bas amount to tweak it to the performance you want.

In other words: Take your best designed mix and charge the test system with it.

Hello The MG Pony,

I do it with every mixture that I hope it will have a good behavior because its thermodynamic properties. :p I will explain what is my problem and why I asking you for something else to consider in a process for to improve a mixture refrigerant. For example if I have 2 mixture A and B, and I test it in the same system I hope to be the best COP with a mixture A which have the highest enthalpy and the lowest absorbed power by the compressor because in a diagram Pressure versus Temperature the mixture A have lowest pressure compared to B. If I just consider it as Peter said, I hope obtain the best COP with the mixture A, but not because the mixture A, also have the lowest density and it affect m, yeah? for to determine Q:m(ethalpy) and as A have a low density, so it decreases to m and you know, if m down, Q and obviously COP will too… its man that I had to consider the density also. Ok I learned it. Now I think I have to consider something else because I have some mixtures with similar properties like Enthalpy, pressure and density, this mixture have a big different COP, why? I don´t know. It make me think that something else affect the system and I have to find what is it? You got it? For what? For I consider it when I am modeling and designing new mixtures and choose reality the best for to test in not just one system if not a lot system for to ensure what I predict seeing and comparing the properties of the mixtures.

Sorry if my English isn´t not so good, if you don´t understand something, tell me and I will try to explain it better or what I mean ok?.

Thanks a lot.

Have a nice day.

María Elena

[mebluna]

The ideal for me should be reaching the properties of the good old refrigeants R12, R502 and R22 (which is almost at the age of retirement now:p )

Hello Peter;) , please read what i wrote to The MG Pony, it is also for you, then read the next.

Which properties exactly? i mean which properties make that this refrigerant have or obtain a good COP? Please don´t tell me that because it refrigerant have a good energy efficience or good COP, i would like to know what in this substance do it capable for to do it. yeah?

Tanks a lot!

Have a nice day.

María Elena

[nh3simman]

Hello Mebluna,

By now, you have probably read the ASHRAE chapter on refrigerant properties so you know all about the safety and practical lubrication issues.

COP is not a property of the refrigerant, but a characteristic of the refrigeration system with that refrigerant. So to use COP as an indicator of refrigerant performance, you need to specify te,tc,sh and sc. From that, you see that performance depends on the intended application. I would also question the effect of the compressor efficiency on a real system.

I would suggest that you buy the NIST Refprop program. For what you get, it is very cheap. This has hundreds of refrigerant properties including an interface that you can use to compare properties. At least you can now compare your new refrigerant to existing ones.

One question for you. If you install the same refrigerant into two different systems, would you expect the same performance?

[mebluna]

Hello Mebluna,

By now, you have probably read the ASHRAE chapter on refrigerant properties so you know all about the safety and practical lubrication issues.

COP is not a property of the refrigerant, but a characteristic of the refrigeration system with that refrigerant. So to use COP as an indicator of refrigerant performance, you need to specify te,tc,sh and sc. From that, you see that performance depends on the intended application. I would also question the effect of the compressor efficiency on a real system.

I would suggest that you buy the NIST Refprop program. For what you get, it is very cheap. This has hundreds of refrigerant properties including an interface that you can use to compare properties. At least you can now compare your new refrigerant to existing ones.

One question for you. If you install the same refrigerant into two different systems, would you expect the same performance?

No, i don´t´think so, because the same reason that you wrote ... COP is not a property of the refrigerant, but a characteristic of the refrigeration system with that refrigerant...performance depends on the intended application... i think it is more clear for me now, thanks. But now i understand that i have to study more about the refrigeration and air conditioning system like if i were mechanic or ingenieer because really i don´t know nothing about it, i am chemist, but if i want to improve the mixture and study somethings like the compatibility of this new mixture with plastics, polymers and the oil lubricants, i have to do it for understand more.
By the way, i get the NIST Refprop 7 version and lately the new version already. It is a good tool, thanks for your advice.
Thakns for your comments,
Have a nice day!
María Elena

[The MG Pony]

Again trial and error, there is so many veriables to be watched the only practicle way albeit intensive is to meter in a tiny bit of various types untill you land one that fits the bill, record the total mix of ingreadients, make a jug of it, and then try it on several systems to see if it performs well in them as well.

There is no easy way to do it in other words.

[US Iceman]

Version 8 of RefProp just became available last week I believe. I highly recommend this tool.

Properties that I think would be desirable are:

High latent heat
Low specific volume for the vapor (so the inverse would be a high vapor density)
and moderately high pressures to maintain high suction pressures at low temperatures.And we also have to consider the safety aspects too such as flammability, possible carcinogens and combustion by-products.

Then, I think the next concern is the material compatibility problems with elastomers, gaskets, etc.



The ideal for me should be reaching the properties of the good old refrigerants R12, R502 and R22 (which is almost at the age of retirement now:p )


I completely agree.:D What we need are complete azeotropes that are stable.:cool: