shut the door/heat exchanger

[jayjay]

Is there anyway to roughly calculate how much it cost every time the freezer door is opened on a 3000 sf freezer. freezer runs at 0 degrees door is about 8'x8'.
Also can I install a heat exchanger on the return line of the freezer? Would like to capture the extra heat to heat the building if possible.
Thanks

[FrozenPhiber]

This is a very complicated calculation. You would need to use an engineering modeling program such as IES to get that information. Heatcraft Probox software may also be able to help.

As for the heat exchanger on the return (suction?) line, there is almost no point as the suction line will be returning at 0 degrees at the evap. exit.

[jayjay]

Thanks for getting back to me I have been having trouble logging back on. I'm just trying to get an idea how much it would cost when you open the door. $.50 or $50.00.
I'm not a refrigeration guy so I have no idea which line I'm talking about. One of the lines is so hot you cant touch it. I thought I could almost just build a small heat exchanger basiclly wrap the pipe in a copper coil and run water through it to a boiler mate type of unit.
what do you think?
Thanks

[winfred.dela]

I'm just trying to get an idea how much it would cost when you open the door. $.50 or $50.00.

Hi jayjay,

I've built quite a lot of cold rooms (just above zero up to minus 55 deg C.)
I would be very interested in a software or any way to figure out this cost.

I hope somebody out there have figure out a way to do this and share the knowledge.

Regards,
Winfredy

[Darshi]

winfredy ,
I did develop an algoritham ,long time back for losses thru open doors for air curtain application . I will try if I can find it in my old notes.
It was ages back

[jayjay]

That would be great. My tenant wants to rent out the freezer space and I'm telling him he can't because of the cost everytime the door opens. He thinks it insignificant.
Hope to here from you.

[US Iceman]

If the doorway is completely unobstructed when it is open the operating costs can be significantly higher due to the air infiltration of the ambient air. I would call this an "unprotected" door.

If you want to reduce this penalty to something a lot more reasonable, install some plastic strip curtains to cover the doorway. This would make the door somewhat "protected".

Even with the plastic strip curtains, you do not completely eliminate the air infiltration (and associated higher operating costs). However, these do offer a cheap fix to your problem.

I would also suggest you make the renter responsible for maintaining the strip curtains. If they tear them up, then provide an upcharge for higher energy use until the strip curtain is repaired at their costs.

[Darshi]

That would be great. My tenant wants to rent out the freezer space and I'm telling him he can't because of the cost everytime the door opens. He thinks it insignificant.
Hope to here from you.

I will endorse the thought forwarded by US iceman .
That is the best solution

[jayjay]

I do have the curtians up. He wants to go from twice a week opening the door to 10 times a day. I think this will make a difference. He doesn't think so. Still having trouble finding the Dixell xweb500. The guy in Holtsvill will not sell it to me and all the people he recomends don't know what I'm talking about

[Paulajayne]

Hi

http://www.frperc.bris.ac.uk/home/about/af/cfdinfil.pdf

paula

[jayjay]

well I read it the link thanks. Unfortunitly I understood none of it. Can anyone simplify it for me?

[TXiceman]

ASHRAE had a claculation for flow across an open door. Been some time since I have used it. I put the subroutine in a box load calculation program I wrote about 15 years ago. I still have the notes some where and a copy of the program in DOS Basic.

Ken

[US Iceman]

Paula,

Thanks for posting that link on door infiltration loads. The models mentioned in this report are similar to the method TXiceman mentioned in his post.

[winfred.dela]

I put the subroutine in a box load calculation program I wrote about 15 years ago.
I still have the notes some where and a copy of the program in DOS Basic.

HiTXiceman,

It would be nice if you could share program.
Is there a version done by a manufacturer (refrigeration, door, panel, etc.) that have been around for a while?

Regards
Winfred

[TXiceman]

EASYLOAD.zipHere is the last Dos version I had used. Jeff and developed it earlier and I made extensive mods to it later. This is not the one with subroutines, but the door open calcs is in the program. BasicA is included as the program runs from basic. You will have to load basic first then use F3 too load Biload. Then F2 to run the program. It is an engineering program designed for engineers. You need to have a basci understanding of the ASHRAE (or Krack) load calculations. I have not run the program for several years and take no responsibility for the results.

Ken

[Darshi]

well I read it the link thanks. Unfortunitly I understood none of it. Can anyone simplify it for me?

Try this link
http://www.berner.com/sales/energy.php5

[jayjay]

Thanks guys I looked at the Berner link and it calculates roughly to $7.00 per hour an 8'x8' door is open with outside temp 70 and freezer 0 at a cost of .13cents per kW that seems low to me?

[TXiceman]

If you don't feel the info is right for your case, it is not all that hard to run the calcs for fully developed flow across the door based on the open time, door size and the differential temperature to see the difference in load on the box. Once you have the load difference, you can then do an energy/cost analysis for the open door and closed door cases.

Ken

[mrm12399]

Hey JayJay,
This is one of those guys in Holtsville. Send me an email with some contact info and I will get things going for you on an XWEB500. My email is mike@weissinstruments.com