Fan Speed

[Giannis]

Hi from Greece,

I want less humidity in a cold room (***** 22) with porks , the evaorator dont have ice but inside the room you can find a lot of water drops in the roof and the porks are very wet.
The temperature inside is -0.5C whith Differential 0.5C The RH Humidity is 50% but the customer need less. The fans are ON when the Solenoid valve is ON and ofcourse off during defrost.
If i install an inverter and when the solenoid valve is OFF i start the fans at low speed continiusly can i have less humidity ?

Regards,

Giannis

[Spiffinator]

Are there any delay on fans after a defrost?
Sounds like they start immediately after the defrost cycle is done.
Try to delay 'em 2-3 min or till coil temerature is below zoro, that would prevent the water to "spray" out of the evaporator and stick to the cieling after a defrost cycle.

In order to lower your humidity in the cold room you need to lower the temperature in your evaporator.
If you have higher temperature difference between coil temperature and air intake temperature you will "catch" more water on the coil, thus lowering the humidity in the room.
Maybe you can achieve it by lowering the fanspeed as you say, would like to hear the result if you decide to do this )

[paul_h]

Whats the evap temp air on/off?
What's the coil size, heat load, coil surface area?
If you want low humidty, you want a large TD on the air on/air off.
But without any details we don't know if there's a low TD or high humidity from coolroom leaks or product sweating.
But just guessing, if there's no ice on the coil and the coil temp is -0.5C, then you have a lot of defrosts or the coil isn't removing much humidity due to low TD

[PaulZ]

Hi Giannis Are the water drops all over the roof or just in front of the evaps? Increasing the TD across the coil will decrease the humidity but be careful you don't get too big a TD as this will dry the meat out and the weight loss will be considerable. The best way to chill carcasses is to put the evaps behind a wall and reverse the air flow, blow the air from the bottom of the room and have the return air at the top. This stops condensation on the roof of the room. With a conventional room the air coming off the evap is very cold and this causes the roof to get very cold and when the hot carcasses are put in the room the hot humid air from the meat hits the cold roof and condenses. By running a colder evap you can compound the problem as the roof will be colder then it is at present. You can install some deflectors to direct the air away from the roof (this may help) and increase the air speed to max during the initial chill period then drop it back as the high air speed will also dry the meat out. Let us know how you get on . Paul

[Giannis]

First i will tommorow set the delay after defost as Spiffinator told me and i will send the data of 1 week temperature (room,evaporator,CP) recordings in this forum .Thank you i will have news tommorow

[hendry]

First i will tommorow set the delay after defost as Spiffinator told me and i will send the data of 1 week temperature (room,evaporator,CP) recordings in this forum .Thank you i will have news tommorow

please also observe the cold room daily operations esp. on how long they leave door open and etc.

this also helps to determine the suitability of the design apart from changing refrigeration paraemters.

[Giannis]

This Attachment is one week recordings from the room. And photo from the drops, (some times ice drops)

ROOM SIZE 90m3
***** R22
COOLING CAPACITY 17KW
AIR FLOW 15200m3/hour
AIR THROW 20m
FANS 2 X 500mm

waiting your replay

[chillin out]

What height is the ceiling?
What height is the thermostat?

Sounds like you have warm air rising up and condensing on the ceiling. I would run the fans (or at least one of them) all the time except during a defrost.

Also if you could get the evaporator colder it would help.

Chillin

[Gary]

If i install an inverter and when the solenoid valve is OFF i start the fans at low speed continuously can i have less humidity ?

You can lower the humidity by running a lower fan speed when the solenoid valve is ON.

Keep in mind that this will lower the weight of the pork and therefore lower its value.

[Gary]

I would run the fans (or at least one of them) all the time except during a defrost.

I agree. Cycling the fans with the solenoid valve is not a good idea. The fans should only be off during defrost.

[Giannis]

Thank you Gary

I will try to Have the fans always ON but OFF during defrost.

Must i change the speed ?
Low speed when solenoid is ON and high when is OFF or the negative ?

My Customer dont care about the weight losses but about the quality (not dark meat)

[Gary]

Lowering the fan speed (when the solenoid is ON) lowers the evaporator temp, thus increasing the TD. As several people have stated, increasing the TD lowers the humidity.

Since it will be dehumidifying more it will be cooling less, so the run time is increased and you can expect more frost on the coil also.

If you lower the fan speed too much, there won't be enough cooling to bring down the temperature and you may need more defrost cycles.

Everything is a trade-off. You need to find the right balance between cooling and dehumidification. Slower fan speed, but not too slow.

High fan speed when the solenoid is OFF will help to defrost the coil and will help to circulate the air throughout the room.

[Giannis]

Lowering the fan speed lowers the evaporator temp, thus increasing the TD. As several people have stated, increasing the TD lowers the humidity.

Since it will be dehumidifying more it will be cooling less, so the run time is increased and you can expect more frost on the coil also.

If you lower the fan speed too much, there won't be enough cooling to bring down the temperature and you may need more defrost cycles.

Everything is a trade-off. You need to find the right balance. Slower, but not too slow.

High speed when the solenoid is OFF will help to defrost the coil and will help to circulate the air throughout the room.

Thank you Gary, And what about the Expance valve ? i must close a little or open ?

[Gary]

You won't need to adjust the expansion valve.

[Giannis]

Thank you Gary,

I Will have the results soon !

[hendry]

This Attachment is one week recordings from the room. And photo from the drops, (some times ice drops)

ROOM SIZE 90m3
***** R22
COOLING CAPACITY 17KW
AIR FLOW 15200m3/hour
AIR THROW 20m
FANS 2 X 500mm

waiting your replay

a glance of the data ... i interprete as insuficient pulldown of temperature before the next defrost interval.

kindly consider this. you definitely need the pulldown to works to your advantages.

[Andy]

a glance of the data ... i interprete as insuficient pulldown of temperature before the next defrost interval.

kindly consider this. you definitely need the pulldown to works to your advantages.

Hi hendry

it would seem the room has not enough refrigeration in it

About 30kW would suffice

Evaporation is also important, but only if there is enough duty and air circulation in the room, I suspect neither is right in this situation.

Kind Regards Andy

[Gary]

According to the temperature chart provided, the cooling seems to be off much longer than it is on... or am I reading it wrong?

[Andy]

According to the temperature chart provided, the cooling seems to be off much longer than it is on... or am I reading it wrong?

Hi Gary

yes the coolers are off on stat quite a bit, too much for a room this size with this amount of cooling duty.
Possibly the dual discharge coolers are short cycling their air or more likely by the humidity levels only refrigerating part of the room.
Dual discharge coolers would not be my first choice to cure a meat product.

Something is very wrong with this installation

Kind Regards Andy

[Gary]

Hi Gary

yes the coolers are off on stat quite a bit, too much for a room this size with this amount of cooling duty.
Possibly the dual discharge coolers are short cycling their air or more likely by the humidity levels only refrigerating part of the room.
Dual discharge coolers would not be my first choice to cure a meat product.

Something is very wrong with this installation

Kind Regards Andy

Hi Andy,

I suspect we may see an entirely different picture once the fans are running during the off cycle. Cycling the fans with the solenoid would be the first thing that is very wrong here.

[Giannis]

Yes, we isntall a big evaporator becouse of customer,

If you need more information Gary i can tell you anything about this system.

I always trust your answers


Regards

Giannis

[Andy]

Hi Andy,

I suspect we may see an entirely different picture once the fans are running during the off cycle. Cycling the fans with the solenoid would be the first thing that is very wrong here.

Yes very wrong

Air should move constantly in the room, with a minimum of 0.5m/sec around the inside of the hams.


Kind Regards Andy

[s/market guru]

run fans continuously , only shut down on defrost.adjust temp set pouint from -0.5 to -1.0 with a 1.0 degree differential. slow fan speed down,adjust defrost frequency to suit coil frosting up.then log progress

[hendry]

Hi Gary

yes the coolers are off on stat quite a bit, too much for a room this size with this amount of cooling duty.
Possibly the dual discharge coolers are short cycling their air or more likely by the humidity levels only refrigerating part of the room.
Dual discharge coolers would not be my first choice to cure a meat product.

Something is very wrong with this installation

Kind Regards Andy

as i was saying ... temperature pulldown is insufficient.