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HELP: refrigerator design and heat transfer
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Posted by: josphate

03/16/2005, 09:33:45

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i am a student at the national university of science and technology, zimbabwe and i am designing a portable refrigerator for vehicle use, powered by the cigerate lighter and capable of being moved out of the vehicle. the problems i am facing are more of tactical and design oriented rather than technical.
first:
i cannot find a small enough compressor for the fridge and this is a major setback. i have had to resort to employing an absoption type system which results in a reduced COP and system efficiency. is there a better alternative?
second:
in a matter of opinion, what would you suppose would be the best cooling load for such a small refrigerator...to be used in a car, without interfering with the usuall operation of the car?
third:
i am failing to obtain tables for chemical and thermo dynamic properties of refrigerants which can be used in such confined spaces without being a health hazard to the occupants of the vehicle, yet fulfilling the design specifications. do you have any suggestions or appropriate links that i can refer to?
forth:
in a matter of opinion, what type or texture of material for the refrigerator covering would you be comfortable with?
fifth:
i only have a month left to complete this project and i do not have a prototype as yet...do you have any quick ideas?

thanks,

josphate






Modified by josphate at Wed, Mar 23, 2005, 02:47:39

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Re: HELP: refrigerator design and heat transfer
Re: HELP: refrigerator design and heat transfer -- josphate Post Reply Top of thread Forum
Posted by: devitg

03/27/2005, 20:12:39

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Well , we lost about 11 days.
Just to avoid all the problem you face .

use a peltier cell refrigerator.

Search for PELTIER CELL at any search motor
It could be GOOGLE







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Re: HELP: refrigerator design and heat transfer Sad
Re: Re: HELP: refrigerator design and heat transfer -- devitg Post Reply Top of thread Forum
Posted by: josphate

03/29/2005, 03:40:08

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thank you for responding, and for the suggestion...but on my side of the world, i think the component is too difficult to find on the market and i think its too late for me to try and fabricate it( the PELTIER CELL ).
the idea is to present it(the refrigerator) at the Zimbabwe International Trade Fair, which is now in a months time... which isn't a lot of time.

i although have resorted to using a fuel pump in an absorption system of ammonia, though its toxic, i feel its good enough for exhibition purposes only...then further development might follow.

the problem is

i can't get affordable piping other than stainless steel and

i'm not sure how long mild steel will last under corrosive ammonia

or how goods it will perform in terms of heat trnasfer

let alone finding a thin enough pipe, that can be easily bent.

i'm finding it difficult to determe the enthalpies of the aqua ammonia solution at different concentrations coz this requires an enthalpy-concentration chart...which i can't also find.

...do you have any suggetions...i really am lost and my ego is dangling on the line.

i really need the help, thanks







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Re: HELP: refrigerator design and heat transfer
Re: Re: HELP: refrigerator design and heat transfer -- josphate Post Reply Top of thread Forum
Posted by: peru715

03/29/2005, 20:31:45

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As the post stated...you best option given the time constraints are with a Peltier cooling system - is it any more difficult to find on the market than Ammonia, piping, "small compressor". For a Peltier system, all you need is

1. Peltier Chips (purchased rather than made - some manufacturers give them away as samples)
2. An insulated box
3. A Heat exchanger i.e.fans and heatsinks. A computer CPU Peltier cooling system might be an easier way to go with this...a search on computer and cooling would yield some results

Good luck







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Re: HELP: refrigerator design and heat transfer Smile
Re: Re: HELP: refrigerator design and heat transfer -- peru715 Post Reply Top of thread Forum
Posted by: josphate

04/02/2005, 05:13:13

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...thank you guyz for all your effort. i just got educated on what the peltier cell is and i am going to try it out. i just hope to make it in time.

thanks







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