PDA

View Full Version : Re: Banana Storage Problems



PRING
02-08-2006, 06:54 AM
Dear Engineers,

We have a problem in our cold storage regarding too much moistening of our banana boxes. We took the moisture content of the boxes before these boxes were loaded inside the cold storage & the average reading ranged from 14-15 % after 5 days of storing we pull out the boxes to be loaded in the refrigerated vessel and took the moisture reading again, and the average reading ranged from 21-22%. The boxes had gained moisture as high as 8% and this is now our problem because our corrugated boxes had collapsed.

This was the situation of our cold storage:
Our cold storage was newly installed and had 3 circulating fans. the 2 side fans had air velocity of 2.8 m/sec and center had 7 m/sec. The room temperature was set to 13.3 degrees centigrade & had an area of 1650 m x 440 m with relative humidity readings of more than 95%. Fresh air will be introduced to the cold room every 6 hours to neutralize the build up of carbon dioxide given off by the banana fruits.

The cold storage was not equipped with dehumidifier and there was no proper drainage for the condensed water, that it just dripped inside the room flooding the floor. The side walls were also sweating including the porch The fans were installed horizontally that the condensed water dropping will be carried over & atomized by the force of air blown by these circulating fans.

My questions are:
1) Does the water flooding the floor of the storage compartment contributed to the dampening of our boxes?
2) Will the circulating air pick up some water on the floor during its circulation inside the room?
3) Our bananas were placed in plastic bags with perforations (polypack) but we did not experience dehydration at the market because the weight of fruits were maintained, where did these water came from? Was it coming from the make-up air?
4) What was the cause of chilling damage of fruits?
4) What shall we do to solve these problems.

Please help us

Thank you

Pring

The MG Pony
02-08-2006, 08:08 AM
yes the water will come in from make up air.

First this is to properly deal with the condensate and get it out of your cold store, second is get a dehumidifyer in there and dry the whole place befor further usage, and it would be a good idea to sterylize the flood after drying

then after that wait till the more experianced guys come in and they'll be able to help you perminantly fix it.

Darshi
02-08-2006, 12:28 PM
Pring,

Your problem is very interesting but solvable.
Let us assume the following

Ambient Dry bulb temperature is 37 0C
Ambient Relative humidity is 65%
Abs. Humidity 25 g/kg

Storage Dry bulb temperature is 13.3 0C
Storage Relative humidity is 65%
Abs. Humidity 25 g/kg
Delta w 25-9 =16 g/kg

Few questions first.
1. What is the fresh air quantity to remove Co2 every six hours and how long is the fresh air supplied?
2. Kg. air/Hr x T Hours x Delta w /1000 = w Ltrs/hr
3. T is the time you run the fresh air fan.
4. w is the water coming in thru fresh air every 6 hours
Now that we have accounted for water coming fro fresh air ,if you say that there is an increase of 7% in the moisture content of the fruit ,now if fruit was X000 kg
Water in produce = X0000x7/100 Ltrs.
If both the quantities are same .Than fresh air is the culprit.
If not please check the following
5. vapour barrier in walls /fllor/ceoiling?
6. Are the doors vapour sealed
Please post the information back and we will solve the puzzle

knighty
02-08-2006, 10:01 PM
mmm, if he boxes are cold compared to the fresh air you're introducing then the moisture in the fresh are will condense onto the boxes....

personally I'd prefer to supply a constant stream of fresh air rather then at intervals... if you have fresh air coming (slowly) into the room and directly into the evaporator then it should be cooled right away to a temp. lower then the temp. of the boxes and so solve your problem :)

(p.s. I'm not a refrigeration engineer tho!)

frank
02-08-2006, 10:09 PM
if you have fresh air coming (slowly) into the room and directly into the evaporator then it should be cooled right away to a temp. lower then the temp. of the boxes and so solve your problem :)
Yes it would but you would need to increase the size of the evaporatror to handle to additional latent load

US Iceman
02-08-2006, 11:25 PM
Fresh air will be introduced to the cold room every 6 hours to neutralize the build up of carbon dioxide given off by the banana fruits.


Using fresh air for dilution of the CO2 is OK as long as a certain amount of air/CO2 is also allowed to leave the room, otherwise you end up pressurizing the room.

You also have to condition the fresh air. If the fresh air is introduced into the room without cooling and some dehumidifying, then you will have condensation problems.

The fresh air should be cooled by a separate evaporator, then allow the air to enter the cold storage area. If you depend on the refrigeration evaporators in the room for this, you can have condensation close to where the air is introduced.

Peter_1
03-08-2006, 07:38 PM
Interesting problem and interesting replies so far.

If you want to control it perfectly, then you need a dehumidifier.

Or you can add some condensors in your cold room - what a huge cold room you have there - or condensor batteries in front of the evaporators so that you can use the refrigeration system to dry the room.

Another technique I saw is cutting off evaporator surface so that the evaporating temperature goes lower and you dehumdify more.
But this energetical seen not so interesting as the condensor.

I think it's difficult to measure and propably not correct to say that the mositure isn't coming from the product itselves. What's the ratio between the wood of the crates and the products in the cold room?

If the make-up air is so determining for the problems, then you must make that you have a controlled flow, controlled by a max CO2 controller, like they use in a controlled cold room for apples or pears.

The drain must be directed to the outside as MGPony suggested if moisture is a problem.

Darshi gave you some good information.

Knighty, even if you're not a Refr. tech, your idea was not that bad.
I think Frank that the location where you brought it in the room doesn't matter for sizing the evaporator.
The latent heat is inside the coldroom and this must removed anyway.

Let us anyway know the progress of your problem because we all an learn from it.
Do you have the possibility to make some pictures of this coldroom?

Andy
03-08-2006, 10:25 PM
Yes it would but you would need to increase the size of the evaporatror to handle to additional latent load

Increase or reduce now that is the question:D

I would say reduce the evaporator size or increase the compressor size, dry the room out:)

Kind Regards Andy:)

Darshi
04-08-2006, 04:08 AM
"A problem well defined is half the solution ", said some wise man.
This storage problem needs clearer definition before we jump to solutions.
If fresh air is the problem, solutions like Co2 absorbers are much cheaper than putting in a new compressor or throwing away the old evaporator or even adding a new Dehumidifier
In tropical countries ,the ambient moisture loads are as high as 25 to 30 grams /kg of air . The moisture content at the storage at thr storage conditions (13.3 and 95% Rh) will be around 9 grams/kg. If the vapour barrier is poor or punctured in the storage walls floor or ceiling, the moisture from outside will migrate to the produce and strike an equilibrium.
Friends who have handled cold storage jobs would have experienced broken floors due to ice formation in the ground below the floor. Please refer- Refrigeration & air-conditioning- by Jordan and Priester for more on effects of vapour pressure dynamics

US Iceman
04-08-2006, 04:50 AM
"A problem well defined is half the solution ", said some wise man.


And, also re-quoted by another.;)

You are indeed correct. We (all refrigeration people) do have a tendency to jump at solutions before the problem is well defined. Sometimes in the haste to solve the problem, others are created. This clearly falls into the area of "look before you leap".

In some cases, this tends to result in adding more cooling equipment, rather than fixing the real problem.

Perhaps, the solution is to continue to ask more questions until sufficient information is available.

I have to say this is been some of the best advice I have seen in a long time. I for one will look into the book availability. Thanks.

Josip
13-08-2006, 09:09 AM
Hi, Pring :)


Dear Engineers,

We have a problem in our cold storage regarding too much moistening of our banana boxes.

This was the situation of our cold storage:
Our cold storage was newly installed ........

The cold storage was not equipped with dehumidifier and there was no proper drainage for the condensed water, that it just dripped inside the room flooding the floor. The side walls were also sweating including the porch

My questions are:
1) Does the water flooding the floor of the storage compartment contributed to the dampening of our boxes?
2) Will the circulating air pick up some water on the floor during its circulation inside the room?
3) Our bananas were placed in plastic bags with perforations (polypack) but we did not experience dehydration at the market because the weight of fruits were maintained, where did these water came from? Was it coming from the make-up air?
4) What was the cause of chilling damage of fruits?
4) What shall we do to solve these problems.

Please help us

Thank you

Pring

It is not easy to say but it seems that your cold storage is not installed properly i.e. air leaks in..improper equipment...handling time...maybe your boxes are not of good quality;)

I agree with guys asking you to define your problem or give as much as possible details

Best regards, Josip :)

Samarjit Sen
13-08-2006, 02:02 PM
Dear Pring,

The Storage conditions for bananas are 8.9 to 11.7 Deg. C with a RH of 90 to 95%. From what you stated it appears that the either you are using an Evaporator Unit with water spray over it or an Humidifier which is discharging the moisture of water particles between 10 to 15 microns.

If we consider that the door is air tight, then the water on the floor is due to the high molecules of water drpolets . Further the water on the floor shall increase the humidity .

The packing for the bananas should be in corrugated fibre board boxes with 13 to 18 kg per box. Polyethene film and paper pads should be laid inside so as to reduce the moisture and protect the plantains from damage during handling and transport.

Specially for fruits such as these CA system are best and most suitable. Should you require any further information, kindly do let me know.

I also agree with Josip, that the plant has not been designed and installed properly'

With best wishes, Samarjit

bananajim
28-03-2007, 07:19 PM
Pring forgot to mention, that the drain pans are flooded, and most of the moisture is coming from them, as well as the blow off. If the fans are operated at lower speed with a VFD, and possibly fitted with demisters, and the drain pans are modified to allow them to run dry, the problem will go away.

This problem has nothing to do with dry bulb or wet bulb or makeup air, it has to do with a failed experiment at providing free humidification, which really worked well, to the point of creating a much larger problem. IMHO.

lana
29-03-2007, 10:02 AM
Hi there,

Everything has been advised so far.
Banana is the most difficult fruit to store.:D :eek:
I have worked with KIWI fruit which needs 0°C and 95%RH. with no problems.
The first thing you have to do is to get the condensate water out properly. Then check the size of the evaporators with design cooling load and design TD (6°C).
For calculating the cooling load you must add the ventilation load as well, otherwise the compressor capacity would not be enough.
I think you have three major problems,
1- Condensate water stays in the room,
2- Room is not air tight and moisture gets in,
3- Ventilation air load was not accounted for.

Good luck.
Cheers:)

mauriziobadanai
29-03-2007, 11:27 AM
Does anybody use "special" gasses for the ripening or maintaining bananas.

I have heard that in such cases you need stainless steel heat exchangers otherwise the copper parts will be eroded in a few weeks....

nh3wizard
29-03-2007, 12:57 PM
1373

Not sure if this information would be helpful

Gary
29-03-2007, 03:35 PM
What I am hearing is:

1. Bananas need 90-95% RH

2. The room is above 95% RH

3. Condensate is being held in the drain pan and/or dumped on the floor.

The danger here is overcompensating and removing too much moisture from the room. It seems to me that the logical first step would be to drain the condensate outside the room and see if that gives us the proper humidity level. If this removes too much moisture, a solenoid valve could be installed in the drain line and controlled by a humidistat.

lana
29-03-2007, 03:52 PM
Does anybody use "special" gasses for the ripening or maintaining bananas.

I have heard that in such cases you need stainless steel heat exchangers otherwise the copper parts will be eroded in a few weeks....

Hi there,
Banana produces ethylene gas and it is very sensitive to it, i.e. it will ripen with ethylene.
As I mentioned before, banana is very difficult to store and maitaine. If the temp. changes from 13°C to 15°C then the storage time will be reduced considerably.:confused: :eek:
Cheers:)

Peter_1
31-03-2007, 08:18 AM
All interesting but Pring never came back, not even for a thank you or some update of his problem.

lana
31-03-2007, 10:55 AM
All interesting but Pring never came back, not even for a thank you or some update of his problem.


Maybe he is just reading:rolleyes: and learning:confused: or laughing:D

cheers

knight rider
31-03-2007, 11:09 AM
maybe pring has gone "bananas" after reading all the responce his had

Peter_1
31-03-2007, 12:07 PM
Or just a bad attitude, missing some basic manners

VENTECH
02-02-2008, 12:18 AM
It is generally accepted that temperatures below 13.8 Deg C will cause chilling injury, so I query Samarjit's statement that 8.9 to 11.7 deg is the correct temperature.
With regard to the problem of humidity caused by fresh air to purge out CO2, why not install a CO2 scrubber, then you don't need the fresh air?
Regards
Peter Evans Ventech Agrionics

nike123
02-02-2008, 12:44 AM
This is facts what I found about banana ripening:
http://tinyurl.com/2aav2k

Samarjit Sen
03-02-2008, 05:09 PM
Like all others, I too would like to know to as to what happened to Pring's bananas.

Double V
18-03-2008, 02:00 PM
Hi All

Like true Fridgies, we make the problem quite complicated. Why not just change the boxes?

:rolleyes:

Double V

Philip
28-03-2008, 06:57 AM
tell us first what happened to your banana

bananajim
23-05-2009, 07:24 PM
I've been doing this for awhile, here are my thoughts:

1) Does the water flooding the floor of the storage compartment contributed to the dampening of our boxes? YES. You need to drain condensate to outdoors, and install de-mister pads on the fan discharge, to stop water from blowing off the coils. Bananas are stored in corrugated boxes all over the world, awaiting vessel loading, and what you experienced does not normally happen in other cold stores.
2) Will the circulating air pick up some water on the floor during its circulation inside the room? YES.
3) Our bananas were placed in plastic bags with perforations (polypack) but we did not experience dehydration at the market because the weight of fruits were maintained, where did these water came from? Was it coming from the make-up air? YES. You should use a CO2 sensor to control the fresh air makeup, no sense bringing in more air than you need to.
4) What was the cause of chilling damage of fruits? You are probably measuring temperature to control cooling at the wrong point in the air travel. Be sure to measure discharge air, especially at such high velocities.
4) What shall we do to solve these problems.