Are YOU a free thinker "Challenge" - Refrigeration-Engineer.com forums

mad fridgie · #1 30-10-2009, 09:55 AM

About 12 years ago i built a test facility(long term storage 6 months at a time)
box 1 1m3 -75C
box 2 1m3 -65C
box 3 1m3 -55C

All held within in room 40m3 -40C
(anti chamber -5C).

I had a single compressor air cooled condensing unit
only refrigerant involved R507 (R404a) suction pressure "never" went into a "vacuum".
No Nitrigen,CO2 etc, no pre freezing
HOW WAS IT ACHIEVED?
No answers from NZ

desA · #2 31-10-2009, 05:09 AM

This is not my field, at all, but a few thoughts:

- Liquid pumps;
- Flash tanks;
- Collector vessels;
- Time sequencing.

Gary · #3 31-10-2009, 07:23 AM

I'm thinking New Zealand is not too far from Antarctica.

mad fridgie · #4 31-10-2009, 09:38 AM

Miles away Des and Gary (using my wifes heart does not count either " way to cold" for this application)

Clk320_Greg · #5 31-10-2009, 02:16 PM

built high up towards the outer atmosphere?

cadillackid · #6 31-10-2009, 03:29 PM

high altitude low humidity - no freezing of coils... high amount of solar energy high up that could heat condensor enough to keep above dewpoint....
-Christopher

Gary · #7 31-10-2009, 04:30 PM

R404a/R507 are not going to achieve these temps without a vacuum involved somewhere... within the boxes if nowhere else.

**Peter_1** · #8 31-10-2009, 08:24 PM

Agree with Gary's last post, unless you can do it - which I doubt - via an autocascade and separating the composition in its mixture gases.

Gary · #9 31-10-2009, 08:52 PM

Quote:

Originally Posted by Peter_1

Agree with Gary's last post, unless you can do it - which I doubt - via an autocascade and separating the composition in its mixture gases.

R404A contains R134a, which can reach -80C at atmospheric pressure, but R507 does not. Separating the R134a from the mixture transforms R404A into R507, so perhaps that is why the two refrigerants were mentioned... and you may be right about the autocascading.

mad fridgie · #10 31-10-2009, 11:45 PM

Excellent ideas, but still incorrect
The reason for the design was to get away from the ozone depleting refrigerants that were available at that time.
I bit of a clue, I am not a purist when it comes to refrigeration. Refrigeration is the process of moving energy from one place to another.

Gary · #11 31-10-2009, 11:51 PM

Perhaps added some thermo-electrics (TEC's) in there?

mad fridgie · #12 31-10-2009, 11:57 PM

Quote:

Originally Posted by Gary

Perhaps added some thermo-electrics (TEC's) in there?

Give Gary a Dounut, well done

mad fridgie · #13 01-11-2009, 04:35 AM

Solution.
In the three small boxes we had a number of TECs with large aluminium heat sinks, (top to bottom in the box, 15mm thick and slightly thicker at contact points, very smooth at these point) We built some copper boxes, (electrical earth bars, brazed then machined) these were used a flooded evaps (R507) these were placed on the hot side of TECs.
We controlled the TECs by solid relays 48VDC(power on and Off) and a PID controllers.
The refigeration system was quite normal, There was always sufficient load to keep it running in positive pressure.
Because this was opened very rarely we only defrosted the main room (-40C) once a week.

Gary · #14 01-11-2009, 06:50 AM

Sounds like an interesting project.

desA · #15 01-11-2009, 09:49 AM

Quote:

Are YOU a free thinker

No... consultants are paid for their thinking...

mad fridgie · #16 01-11-2009, 09:57 AM

Quote:

Originally Posted by desA

No... consultants are paid for their thinking...

I never known a consultant think

, accept for you DesA, crawl, crawl, crawl

**Peter_1** · #17 01-11-2009, 10:20 AM

Quote:

Originally Posted by mad fridgie

I had a single compressor air cooled condensing unit
only refrigerant involved R507 (R404a) suction pressure "never" went into a "vacuum".
No Nitrigen,CO2 etc, no pre freezing
HOW WAS IT ACHIEVED?
No answers from NZ

Your post was a little misleading, I read it as only that refrigerant was used.
But is the efficiency of TEC's not extremely low? How many TEC's/chamber you needed to install then?

mad fridgie · #18 01-11-2009, 10:44 AM

Quote:

Originally Posted by Peter_1

Your post was a little misleading, I read it as only that refrigerant was used.
But is the efficiency of TEC's not extremely low? How many TEC's/chamber you needed to install then?

Yes it was a trick question, I sort of indicated that in the title.
At the time of the project (12 years ago), there were very little non ozone depleting refrigerants available, also this was a very low capital cost in comparrision to purchasing specialist imported test cambers.
The actual load was quite small on the small cabinets(they were already in the -40C room) and were only opened every 6 months. (food storage experiment)
We had 8 TECs in each cabinet. Efficiency was not the main driving force at the time. One benifit of TECs is they are very reliable. We chose the 48VDC because this a common voltage in telecommunications, so power supply was easily sourced.

**Peter_1** · #19 01-11-2009, 04:30 PM

Are the TEC's not prone to moisture?
Anyhow, very good solution MAdFridgie. You have to change your name to SmartFridgie from now on

desA · #20 01-11-2009, 04:43 PM

Quote:

Originally Posted by mad fridgie

I never known a consultant think

, accept for you DesA, crawl, crawl, crawl

Regards...

Gary · #21 01-11-2009, 06:19 PM

Quote:

Originally Posted by desA

No... consultants are paid for their thinking...

Consultants are paid for their credentials, which may or may not relate to their skill level and rarely coincides with talent.

Like everything else... you pay for the sizzle, but what you end up with, for better or worse, is the steak.

YMMV (Your Mileage May Vary)

mad fridgie · #22 01-11-2009, 08:09 PM

Quote:

Originally Posted by Peter_1

Are the TEC's not prone to moisture?

TEC's can be prone to water, like most things is about the quality and cost.
You can purchase them unsealed (most buy these because they are cheaper) or you can purchased fully sealed ( a bead of low temp silicon sealant around the edge) these cost abit more, but seem pretty reliable ( I only have limited experience)

Magoo · #23 02-11-2009, 02:10 AM

Mad Fridgie.
I had heard about your experiment way back and was itching to see how long it would take someone to think laterally outside the actual mechanical refrigeration aplication.
Good post, as well as your dry ice generator. You obviously have too much time and money on your hands. ( joke ).
I used a TE unit for my sons science project in last year of high school. Blew everyone away.

mad fridgie · #24 02-11-2009, 04:02 AM

Quote:

Originally Posted by Magoo

Mad Fridgie.
I had heard about your experiment way back and was itching to see how long it would take someone to think laterally outside the actual mechanical refrigeration aplication.
Good post, as well as your dry ice generator. You obviously have too much time and money on your hands. ( joke ).
I used a TE unit for my sons science project in last year of high school. Blew everyone away.

I did not know news travelled pass the bombay hills?
The first time I saw a TE was at my local uni (I was only there for the women, no education) they were using them in a casdade for condensing various gases, I was gobsmacked, as all I had ever been taught was compression and absorbtion (caravan fridge) from that day on I started to look at refrigeration in a different way.
I have plenty of time just looking for that product which will make me the money.
For the last few years being playing around with water heatig heat pumps.
I have some IP in relation to domestic, best COP by far, but I am not in a position to bring this to market.
Thought we had it sold once, but at the last minute fell over, to date we still do not know the reason.
Also just developed high temp machine for the dairy industry 85C water has an eCOP of about "6". Start production this week, marketting hopefully the week after. Shoud give the Mahana Blue a run for its money. designed for the trade by the trade. I will give away a secret, I have installed this magical thing called a reciever, so is not critical charge like MB. No doubt it will be copied in 10 mins.
As I have become older (and hopefully wiser) I no longer take risks on contracting jobs. No Balls any more

desA · #25 02-11-2009, 08:46 AM

Good stuff, MF. All the very best with your marketing...

Magoo · #26 04-11-2009, 04:44 AM

Hi MF.
Most people north of the Bombays are not from Auckland, me being another one. So the only toss pots are mainlanders that have never left the nest, mums apron strings have to be cut, think laterally. ( joke ), Jaffa ****heads and the like
The MB developed by George the grump is a totally great system, took an age for dairy industry to figure it out and save money.
All the best with your new project and marketing stratogy.
I have a few ideas about timber driers, pallet lots, can you PM me on subject with your thoughts.

mad fridgie · #27 04-11-2009, 07:58 AM

Quote:

Originally Posted by Magoo

Hi MF.
Most people north of the Bombays are not from Auckland, me being another one. So the only toss pots are mainlanders that have never left the nest, mums apron strings have to be cut, think laterally. ( joke ), Jaffa ****heads and the like
The MB developed by George the grump is a totally great system, took an age for dairy industry to figure it out and save money.
All the best with your new project and marketing stratogy.
I have a few ideas about timber driers, pallet lots, can you PM me on subject with your thoughts.

My mums apron strings are really long 12000miles lol.
Drying, one of my favorites. Loads of room for innovation. I was interested in the one by "nonickname" reducing waste water.