VENTILATION SYSTEM FOR FOOD PROCESSING UNIT

[tcihvacff1]

Hello Everybody!
Good Day!!!
With reference to the subject I am dealing with a retrofitting project for a food processing unit. wherein the food processing unit already has a ventilation system but failed or its inadequate.
The floor has two portions, one is consists of big OVENS (2nos) from which the cake & pastries are made and another portion is the working platforms for workers i.e, packing the pastries etc. But their is no partition between these two portions of the floor.
The heat dissipation is only from the OVENS. whenever the OVEN door is opened the hot air stream is coming out & this hot air is also travelling into the second portion of the floor. And also there are outlets on the top of OVENS for smoke exhaust.
Current ventilation system comprises of 3 exhaust fans connected with ducts & 2 fresh air fans also ducted.
But still the workers feel more heat & discomfort.
Please review the attachment showing the existing ventilation system in Single Line drawing.

My question is that should I provide a partition wall between these two portions of the floor & then use exhaust fans to extract heat & smoke? parallelly providing fresh air? And does Air-Conditioning require near the OVENS?

Please advice. Your comments are highly appreciated.


Thanks in advance.

 

[Compositepro]

The ovens should be under an exhaust hood that captures all the hot air and smoke that comes out of the ovens. Such hoods usually are large in volume so that the blast of hot air that comes from opening an oven door can rise into the hood to be completely captured and then exhausted to the outside at reasonable flow rate with a blower. This should remove most of the heat load to the room due to the ovens. Air conditioning will be needed to cool the make-up air entering the room and for normal cooling as required for worker comfort. Sometimes it is beneficial to have an extra exhaust blower come on automatically when an oven door is opened. Your ovens will have a vent where fumes and moisture come out during normal operations. The fumes from this vent should be captured by the hood. Make sure your room ventilation does not create drafts that interfere with the capture efficiency of the hoods.

 

[capliard]

Ponctual source of emission is to be controlled by having exhaust very close to it. That's a Mantra!

As Compositepro said, have a hood over it that will suck the hot air out.

Ingenieur Minier. QuTbec, Canada.

 

[tcihvacff1]

Thanks Compositepro for your detail explanation.
And capliard thanks for u too.

@ Compositepro! I got your point. Hoods are the best source of smoke extraction. But in this case we have an issue that thr is no enough space above the Ovens for Hood installation.
Height from the top of the ovens to the ceiling is 700mm only.
That's why I am looking for another option.

Can anyone suggest me.


Thanks in advance.

 

[tcihvacff1]

And if I change the position of Ovens , what is the ideal height to be maintain between the top of the oven & the hood?


Pls share your experience.
Awaiting for your valuable comments.

 

[dbill74]

When you talk hood, I hope you are not thinking of the typical commercial range hood found in restaurant kitchens with grease traps and all. These are relatively small and designed for grease laden air from fryers and grilles.

The hood as mentioned by Compositepro needs only 6-12" deep edges which will be located beyond the edge of the oven, grease filters shouldn't be needed since you are baking pasty foods. Depending on the size of the oven you may want/need multiple exhaust points within the hood. Consider also a fan(s) to collect hot air from right above the doors, interlocking these fans with the doors can save lots of energy in the long run.

Sounds like the oven doors are pointed in the direction of the workers, in this case a partition will help with occupant comfort. Shouldn't need a full partition, just big enough to act as a shield for the workers from the initial heat wave when the oven doors are opened and radiant heat.

Cooling for the workers is a must, be it from small spot coolers are a larger system with diffusers at the work stations. There are lots of ways to do this and most everyone here will be happy to give their opinion, but in the end, it is your decision how this gets done.
You are going to have a lot of exhaust for the ovens which means even more outside air coming in. Good thing is you don't actually have to condition all this make-up air, only any going toward occupant comfort. Ventilation dedicated for hood exhaust/ovens need not be conditioned. (It may yet be prudent depending on the bakery's location and the oven's environmental requirements.)

 

[tcihvacff1]

Thanks a lot @ dbill74

 

[berkshire]

tcihvacff1 ,
You make a comment in your response to Composite pro about not having enough height for a hood. the popular conception of a hood is one with sloping sides up to an extractor fan. The alternative in your case is sometimes referred to as a canopy. It is a structure with vertical sides bolted up to the ceiling and spaced away from the oven sized to catch the buoyant air coming out of the oven as the doors open, to where fans can deal with the hot air.
Another alternative is a venting shaft with a damper inside the oven bigger than your smoke vents which is opened just before the oven is opened to remove the hot air prior to opening the doors.
B.E.

You are judged not by what you know, but by what you can do.

 

[jasonlaroche]

For new installation you need a neutral for the oven if it requires one and a separate ground. Generally amtek air conditioning don't require neutrals so they are not necessary.

 

[chicopee]

"...But still the workers feel more heat & discomfort..." Welcome to the world of commercial baking ovens and I think that is the result of radiation emitted from the ovens and not so much from convection. Your present ventilation system should have an airflow at the work height with a velocity of 25-50 ft/min and your worker have to get acclimatized in a similar fashion to foundry workers.

 

[Drazen]

Compositepro, you offer detailed answer, but i wonder had you ever studied that problem or implemented it in practice?

the reason for my question is quite wrong statement how fumes make most of cooling load. while i cannot swear that to be case for each and every particular case, mostly, for such baking ovens, radiation heat make major heat load most of time.

the other question is why large hood would be put over complete oven? do you know how large square footage such ovens have, while all fumes come out of oven doors, which usually present just portion of smaller side surface. that is, putting hood over the whole oven would absolutely make no sense?!

 

[Compositepro]

Ovens are very common in the composites industry. The fumes that may come from these ovens is toxic and it smells really bad. These ovens operate under a slight negative pressure so fumes do not escape into the room during normal operation. Efficiently capturing the hot air when opening the doors is the hard part, and requires a good hood design. I've seen many bad designs too.

Baking ovens produce a lot of steam, which needs to be vented outside. Most baking ovens I've seen are not very well insulated and I believe that is because heat loss through the walls is a small part of the heat put into the oven. Also insulation tends to rapidly become unsanitary.

 

[tcihvacff1]

Dear All,
I highly appreciate your valuable comments on the subject & thanks for ur involvement.

From your different answers I Finally came to a proposal that:
1.Firstly I will construct a partition between the Oven area & the working area.
2.Secondly, for the extraction of hot fumes coming out when the oven doors are open, I will drop a duct & will fix a low level exhaust air diffuser. So that whenever the oven doors are open the hot fumes will be sucked thru the diffusers positioned in-front of the door.
And as far as the smoke from the top of the oven is concerned I will fix a duct & route it to the atmosphere.
3. Thirdly, for the working area I will provide treated fresh air to maintain comfort in the working area. Client is worried about the budget, so avoiding air-conditioning in the working area.

what do you guys say about this proposal?

 

[berkshire]

tcihvacff1

.Secondly, for the extraction of hot fumes coming out when the oven doors are open, I will drop a duct & will fix a low level exhaust air diffuser. So that whenever the oven doors are open the hot fumes will be sucked thru the diffusers positioned in-front of the door.

You are going to get a nasty surprise with this scheme, Unless you have an extraction rate at the mouth of the diffuser of better than 3000 feet per minute, you will not get enough capture to collect that rush of hot air when the door is opened, unless you have pre vented the oven with the exhaust stack I mentioned in an earlier post. The reasons for a seemingly oversized canopy are to contain the buoyant hot air until it can be disposed of at a lower extraction rate.
B.E.
Time served apprentice, in the manufacture and design, of heating ventilating and fume removal systems.

You are judged not by what you know, but by what you can do.

 

[tcihvacff1]

Dear berkshire,
I think you are correct.
I will try to provide a shaft with damper as u said.
Thanks for ur suggestion