subzero refrigeration
subzero refrigeration
(OP)
hey all..
what's the difference in designing a refrigeration cycle for air conditioning and for refrigerating?
For example: u design an air conditioning cycle to have 80/67 entry conditions with like 45F for evaporating temp, and on the condenser u may try 95F outdoor air, to 125F condensing temperature...
but what about the refrigeration when u have a room way below 0 Celsius (32F)..0F lets say..
how do u do that?
Thank you
Elie
what's the difference in designing a refrigeration cycle for air conditioning and for refrigerating?
For example: u design an air conditioning cycle to have 80/67 entry conditions with like 45F for evaporating temp, and on the condenser u may try 95F outdoor air, to 125F condensing temperature...
but what about the refrigeration when u have a room way below 0 Celsius (32F)..0F lets say..
how do u do that?
Thank you
Elie





RE: subzero refrigeration
Really, the only thing that changes is evap EAT and LAT and, depending upon the refrigerant, the condensing temperature may change.
RE: subzero refrigeration
RE: subzero refrigeration
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RE: subzero refrigeration
at startup the freezer temperature is high, the compressor is stronger and needs more cooling. Since u made ur design on the operational temperature your condenser will be very small compared to the maximum power of the compressor. Ur system will heat up and shut down.
But when evp temperatures reach very low levels, the compressor power is more than halved so it needs only half the condenser.
What my question is, at what temp. should i design it so i don't face problems like overheating and stuff. Standards say that in HVAC u need to measure the capacity of ur machine at 80/67 entering conditions and design it accordingly.. what about subzero refrigeration.
RE: subzero refrigeration
Again, you're designing for the whole system, hence the plural on "operation temperatures." You have to design for a particular lifetime, reliability, maintainability, energy consumption, cooling capacity, ambient conditions, region of the world where it's used, installation constraints, etc. It's not just about temperatures.
What about subzero refrigeration? It's a different problem with different requirements. There are no humans being cooled in this problem, hence many of the constraints used in A/C don't apply.
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RE: subzero refrigeration
http://www.eng-tips.com/threadminder.cfm?pid=1010
I'm my opinion it does look horribly unprofessional.
Back to the question: the unit has to be sized large enough to pull the space down from ambient to the design condition in a reasonable time. The unit also has to be sized to meet the heat gains occuring at static design.
The original equipment sizing will be the largest load that the unit has to produce at the worst expected combination of design temperatures. Part-load can be met with a number of strategies, the simplest being cycling. If a really tight temperature control is required then VFD and other tight capacity control concepts can be introduced.
RE: subzero refrigeration
Anyone who communicates (types) that way in a site created for "Engineering Professionals" will not be bothered to seek out and frequent forum1010: Engineering Language/Grammar Skills . So if it is not pointed out that the chosen quality of communication is sadly lacking in professionalism, how will the OP come become cognisant of this shortfall?
RE: subzero refrigeration
I'll tell someone if I find their writing style annoying and that I find it 'horribly unprofessional'. I'll even start a new thread in another forum to discuss it. I won't tell them how to type though.
Feels very authoritarian for a peer forum.
RE: subzero refrigeration
In my opinion IRstuff's post had the perfect combination of constructive criticism with constructive help.
4 wot 1ts wurf, IRs p0st was purfik, no wot 1 m33n
RE: subzero refrigeration
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RE: subzero refrigeration
" The fact that the OP is getting relatively few responses speaks volumes" Forgive me but what is "OP" I find it a turn-off when I don't see a word spelled out
RE: subzero refrigeration
That one took me a long time.
RE: subzero refrigeration
RE: subzero refrigeration
"... and that's all I have to say about that!"
RE: subzero refrigeration
Engineers already get a bad enough rap for poor English skills.
RE: subzero refrigeration
RE: subzero refrigeration
My objective is to always give the best possible answer, but sometimes, the best answer is not an engineering answer. Getting the OP to communicate and elucidate is quite often required to even come close to getting any answer to a question.
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