Re: Help cutting open 40ft reefer, we now have problems
Quote:
Originally Posted by
adrian_uk17
We are storing pre/preg composite material in the freezers it has a 30 day outlife at ambient temperatures but if you can cool it to -4C it can last for up to a year.
Does the product arrive at your location pre-frozen? If not, this represents additional heat load, pulling it down from ambient temperature.
Is the extension of shelf life linear in regards to temperature (the lower the temperature, the longer it lasts)... or does it only last longer when frozen?
Re: Help cutting open 40ft reefer, we now have problems
Quote:
Originally Posted by
adrian_uk17
You are all right...... However i did do some calculations etc for heat flow etc.
So the 40ft reefers have approx 74m3 of space, we used to freeze these down to -24C
We now have 3 x reefers which are able to chill 225m3 down to -24C.
We have added an enclosed area in between which is 300m3.
So we now have a total of 523m3 and 3 x Reefer compressors.
We no longer want the reefer boxes to go down to -24C we can live with -4 to -5C and the cool area in between can live at 0C approx.
It is a mistake to assume spillage from the freezers in your calculations. The refrigeration system for the cold store area should be capable of handling its own load. You need to minimize spillage in order for the freezers to work as designed.
Re: Help cutting open 40ft reefer, we now have problems
There is little doubt that you are going to need additional cooling for the cold store area, and this is where you can profit greatly from professional help.
Ideally, this main cold store unit would be a system designed specifically for a cold store (medium temperature) application as opposed to a freezer (low temperature) application.
This unit should be sized to handle the entire cold store load under normal conditions. Its temperature control would be set to maintain 0-3C.
The temperature control for unit#4 would then be set to maintain 3-5C, thus acting as a back-up unit, assisting in handling heavier than normal loads.
This way, assuming spillage from the freezers is minimized, you can have all units professionally designed/sized for their particular areas.
And at this point, that's as close as you can get to doing this right. :)
Re: Help cutting open 40ft reefer, we now have problems
Quote:
Originally Posted by adrian_uk17
...the company i work for are not very good at shelling out money for design, in fact we are very good and getting things to half work...
This is an all too common issue. I have been involved in several projects like this where the owner decided he would save a few dollars and do it himself. Then after a year or so of constant problems and lost product they finally ask for help and then complain about all the money that has to be spent to fix the installation.
There is nothing like being in the position of being the messenger and getting yelled at for previous mistakes made (by someone who shall remain nameless, of course:rolleyes:)
In the long run, if you added all the costs spent on an "alternative arrangement" to one designed specifically for the application requirements the owner would be money ahead. But hey, they saved some money initially, right?
As you might have guessed, I am more than a little sensitive to giving away too much information in these conditions, because some firm should have made some money from this.
This is not directed at you personally as it is at the situation Adrian, so don't take my comments to heart.
Re: Help cutting open 40ft reefer, we now have problems
Quote:
Originally Posted by
US Iceman
This is an all too common issue. I have been involved in several projects like this where the owner decided he would save a few dollars and do it himself. Then after a year or so of constant problems and lost product they finally ask for help and then complain about all the money that has to be spent to fix the installation.
There is nothing like being in the position of being the messenger and getting yelled at for previous mistakes made (by someone who shall remain nameless, of course:rolleyes:)
Been there, done that, cried all the way to the bank where I deposited a big fat check. :D
Re: Help cutting open 40ft reefer, we now have problems
There are DIYers and there are Hacks.
Those who invest the time and effort to educate themselves and do the job right have my respect and even admiration.
Those who do a hack job get no sympathy and get no price breaks. They are an insult to myself and my profession, believing that what I do for a living requires no particular expertise.
They reap what they sow. Stick it in and break it off.
Re: Help cutting open 40ft reefer, we now have problems
This is a classic case of "should have". A very definite case of should have hired a professional design engineer to do it right in the first place.
At this point, you need to STOP ALL WORK until an experienced engineer can see what you have and most important, see what you want. He can then address the solution(s) and how to best to salvage what you have. You are at the point of throwing good money after bad unless you get it engineered.
Ken
Re: Help cutting open 40ft reefer, we now have problems
if you have as i think cut the sides out of the trailer why dont you fit insulated curtains like curtain side trailers and you have no problem with -4 temps
Re: Help cutting open 40ft reefer, we now have problems
Guys:
There seems to be alot of beating up and very little problem solving here, Lets be professional about what we want in a forum, help and exchange of ideas....
Okay, I have a very similar setup I use quite sucessfully for a 30x40x16 cold storage in the seafood business. I have nearly constant ingress/egress of product and forklifts, and maintain -5 to -10 F with 4 carrier transicold units. SO HOW DO I DO IT?
First there was a learning curve I will admit. There are peculiarities about van units that have to be overcome.......If yours are anything like Carrier units, the defrost can be initiated either by time, manual, or will automatically initiate initiate based on lack of differential temp air/coil. The unit then goes into defrost until a thermister above the coil reaches a whopping 78degrees f or 30 min elapses. Works great in a small enclosed area (van full of product with very little air volume) but doesn't ever terminate from temperature (read incomplete defrost) in an open room with several other units sucking the heat away (and the resulting moisture, causing them to ice up) This was the case our trial run, frozen evaps, no cooling
First step was to attempt to fool the thermister, but the units are too smart and fault out,( so much for parallel resistoring).
Next step was to enclose the unit air to "isolate" it for defrost. A simple foam box in front of it with a curtain (read blue tarp) door for air inlet and outlet (dont forget a horizontal bulkhead between the two. This allows a small space to get up to temp and the defrost to work "normally" When the fan resumes operation, the flaps are blown in/out without significant penalty of air transfer hp. make sure the box is 2' or so away from the unit so the flaps dont get sucked in, and its important for the inside wall of the unit to defrost, as drain channels are part of it, and it must warm up or it resembles a frozen waterfall soon.
Secondly, defrosting all units at the same time manually helps, as the other units aren't attempting to blow cold air around your warm moist pocket. when we have heavy traffic, we defrost every 3 hours.....
Lastly, if your coils are really frozen up, you may need 2 or 3 or more sequential defrosts to deice them to start with.
If this works out on your units let me know, dglaab@gmail.com
One other note, until recently, all van units were 12, then 134a, and many still are 134a. They work fine, albeight less energy efficiently than current ones, but that is mostly due to compressor design advances. If our esteemed friend is able to make this work, he will have likely spent about 10-20% over building a purpose built system, and the cost of the electricity to run the long duty cycle will be insignificant compared to the original capital outlay, which would be a good management technique had it been properly executed from the get go.
Dan
Re: Help cutting open 40ft reefer, we now have problems
Re: Help cutting open 40ft reefer, we now have problems
Thanks for the bump. I never saw this thread before and I needed a laugh.
Reminds me of a job I had where the owner had two freezer rooms side by side. One working, one not. His solution to get both working was cutting a hole in the wall between them and fitting a fan to blow cold air from the working freezer into the non working freezer room.
Yeah, neither room was cold after that. Perfectly working freezer room wouldn't drop below 6C anymore.