Warming Barrels of Honey With Light

[VABeekeeper]

TL;DR Summary

I'm trying to come up with a way to warm 55 gallon drums of honey using a reflective box and LED lights.

Hi physics lovers,

I'm a beekeeper and I need all the brain power I can get on this problem. If anyone can offer some guidance or opinions, I'm all ears. I'm not a STEM guy. I've taken a few semesters worth of college STEM stuff (chem, physics, calculus, comp sci, does bio count? lol) but I'm not afraid to roll up my sleeves to try to figure out what I need to do here.

Here's the problem: I need to be able to warm 55 gallon drums of honey to about 90F. For simplicity we can assume they start at 60F. I need to warm them so I can pour and pump the honey.

We can also assume I only need to do this for one drum, but in reality I'd like to set up an area for warming 10 drums. Maybe more in the near future.

What I'm thinking of doing is building a large box (plywood) that will just cover the upright drum(s) while it sits on a pallet. The inside of this box would be covered with some foam insulation and a reflective layer on top of that. I'm thinking of adding heat to the box with some LED lights, preferably from the bottom. Ideally the bottom of the drums would be exposed to light to allow the contents to be more efficiently warmed and mixed through convection. Warming 660 pounds of honey in a drum can take a while, especially if the bottom is not directly warmed.

The effect would be a very reflective and somewhat insulated box with a drum of honey inside and some lights. What I'm really unsure of is how do I go about calculating how much wattage I should need to achieve this? The calculations don't have to be super precise either, just in the ball park. If I could get the honey warmed in a week that would be wonderful, but I'm expecting it will take about 2 weeks. Again, I'm just unsure of how to estimate how many lights I need and of what output. I could experiment with it but I have 1000 other things to learn by trial and error, so I'm hoping some math can get me in the ballpark quicker.

**Some options that I've ruled out include radiant heat in the floors, barrel heating bands, heat tape, heating blankets, heat exchanging coils/plates, and a few more. I'm ruling these out for economic reasons or because of the potential to scorch the honey.

 

[DaveC426913]

Insofar as doing actual heating, and insofar as being economical, I'd think LED lights would be nearer the bottom of your list.

Why not incandescent bulbs? They convert a much larger portion of electricity into heat without wasting it all on light.

Have you considered passive sources, such as sunlight heating water in a coil?
Or a solar-powered camping/boating shower? (scaled up of course)

 

[VABeekeeper]

hey Dave,
Thanks for the quick input. I'm definitely open to other types of lights. I am concerned about burning the place down with some of the other types of lights. Maybe LED is just as risky but my seat of the pants feeling was that it would be a little safer? I was thinking about fitting some skinny LED light boards below the drums. Something in this shape: https://horticulturelightinggroup.com/collections/lamps/products/hlg-65

Maybe that's all really goofy and I should stick to some heat lamp type bulbs (not below the drums) and try to insulate, reflect, have them out of the way so nobody smashes them while wheeling the drums around them.

The passive options like you describe could work I'm sure but I'm not sure how I can personally implement it especially in the winter when I need the heat the most. But I will look into it more.

Thank you!

 

[DaveC426913]

I am concerned about burning the place down with some of the other types of lights. Maybe LED is just as risky but my seat of the pants feeling was that it would be a little safer?

Since the heat you want to produce to warm the honey is a fixed amount, it should not matter what type of light you use to do it. eg. a 1000 watts of heat from an LED is the same 1000 watts of heat from incandescent.

As a bonus, with incandescent, you'll just need a lot fewer lights and much less electricity.

And presumably you're going to have some way of monitoring/controlling the temp anyway, so it doesn't reach the ignition point of plywood.

 

[VABeekeeper]

Ok, well I'll definitely look into the incandescent options. Yes, I was planning on using an inkbird controller I have laying around but may get something nicer.

Also, any thoughts on using some kind of actual electric heater (infrared, oil filled radiator type, others?) and some fans to circulate warm air? Maybe the whole light thing isn't the best way to achieve this. Again, I'm open to ideas.

Thanks

 

[berkeman]

Welcome to PF.

Here's the problem: I need to be able to warm 55 gallon drums of honey to about 90F.

Wow, that's a *lot* of honey!

**Some options that I've ruled out include radiant heat in the floors, barrel heating bands, heat tape, heating blankets, heat exchanging coils/plates, and a few more. I'm ruling these out for economic reasons or because of the potential to scorch the honey.

No, an electric blanket is a good candidate, especially since you can set the desired temperature on many of them.

allow the contents to be more efficiently warmed and mixed through convection. Warming 660 pounds of honey in a drum can take a while, especially if the bottom is not directly warmed.

Honey is too viscous to be warmed throughout via convection. You will likely need to actively stir the honey in the drum while you warm the outside of the metal drum with the electric blanket.

 

[DaveC426913]

Maybe the whole light thing isn't the best way to achieve this. Again, I'm open to ideas.

Since cost is a factor, it would be important to understand under what circumstances you are doing this - what resources you have available (inlcuding free ones, such as access to sunshine, etc). What is the amboent temp your are working from? Indoors? Warehouse? etc.(Full disclosure: I am merely a layperson; I have no particular knowledge to bring-to-bear upon this challenge; and I won't be able to help with the math. I am simply asking questions that the experts, when they show up, will probably want answers to anyway.)

 

[DaveC426913]

Here's the problem: I need to be able to warm 55 gallon drums of honey to about 90F.

Wow, that's a *lot* of honey!

That's not a lot of honey...

in reality I'd like to set up an area for warming 10 drums. Maybe more in the near future.

That's a lot of honey.(I suspect he plans to hold the world for ransom by controlling its honey supply. The next Bond Villain: HoneyFinger)

 

[Baluncore]

1000 litre bag containers are built with electric heating mats for the transport of butter. It only takes 12 hours overnight for the butter to heat from refrigerated transport and storage, to reach the temperature where it will flow from the container.

I would build an insulated room big enough to stand the drums of honey on a mesh or channelled floor, like a small 'reefer' container. I would then use a small fan to remove air from the top of the space, to be heated to bring it up to 90F, before being returned to points under the drums. The drums would be surrounded by, and soak up that heat, so would move towards that temperature over a day or so.

Small refrigerated vans are used for food deliveries. When the vans are retired the insulated box is replaced, it is not moved to the new truck. One of those boxes may be available at low cost, and without the light truck, would make the insulated room you require. You would need to retrofit your temperature regulated heating and air circulation system.

Extracted from: https://honey.com/images/files/Detailed-Nutrition-Information.pdf
"Specific Heat & Thermal Conductivity.
The specific heat of honey is in the 0.54-0.60 cal/g/°C range for liquid honey, and is equal to 0.73 cal/g/°C for finely granulated honey. The thermal conductivity of honey increases with temperature and total solids, ranging from 118 x 10^-5 to 143 x 10^-5 cal/cm sec °C."

So, honey will heat in about 75% of the time that the same mass of water would heat.

 

[DaveC426913]

The specific heat of honey is in the 0.54-0.60 cal/g/°C range for liquid honey, and is equal to 0.73 cal/g/°C for finely granulated honey. The thermal conductivity of honey increases with temperature and total solids, ranging from 118 x 10^-5 to 143 x 10^-5 cal/cm sec °C."

So, honey will heat in about 75% of the time that the same mass of water would heat.

I wonder if that takes into account the convection Berkeman mentions.

IOW, if water heats at a given rate including its natural tendency for convection, then the comparison to honey - which may not have that convection - might result in erring on the optimistic side.

 

[jrmichler]

Honey has a specific gravity approximately 1.5, so 55 gallons will weigh 690 lbs. Increasing the temperature by 30 deg F will require $0.6 BTU/{lb-deg F} * 690 lbs * 30 deg F = 12,400 BTU$.

Electricity has $3412 BTU/KwH$, so you will need $12,400 BTU / 3412 BTU/KwH = 3.6 kilowatt-hours$ of electricity to heat the honey. There will also be heat loss, so assume a well insulated box, and estimate 4 kilowatt-hours of electricity. That could be a 250 watt heat lamp for 16 hours, two 250 watt heat lamps for 8 hours, or a one kilowatt heat blanket for 4 hours.

I would suggest putting the heat into the bottom of the drum, and toward one side in order to encourage convection currents.

 

[berkeman]

How about putting a heated stirrer into the drum instead? Dumb idea?

 

[Drakkith]

IR lamps seem to me to be the easiest choice and are very low cost. You can get 250-watt bulbs for less than 10 bucks and the electrical equipment to install them is also of similar price.

 

[Nik_2213]

How viscous is the barrel honey as-is ??

I used to get 'NZ manuka' honey from eg Costco, deep-discounted as 'crystallised in storage'. We preferred 'spreadable' to 'crunchy', so I'd warm their jars to baby-bottle / blood temperature until all clear...

Is your barrel honey sufficiently runny that you could you sink a heating coil in it ? Either indirect via a working fluid (water) and thermostatic heater, be it convective or pumped, or directly with a self-limited electric element ??

If 'set', would this warm coil soften where it stood, allowing progressive sinking to working level ??

I ask, as you may not want to leave even food-grade s/steel in honey for longer than required, else coil could be emplaced when barrel was being filled, ready for this 'dispensing' stage...

Note: IIRC, suitable 'food-hygiene grade' heater / cooler coils are used by 'micro-brewery' enthusiasts. Both to pre-heat brew-mix to initial fermentation conditions, then cool it as yeast really gets going lest tank 'brews up'...

 

[Baluncore]

Is your barrel honey sufficiently runny that you could you sink a heating coil in it ?

If the honey is soft enough to be penetrated by a heater, then it will flow without heating and there is no problem.

The outside of the drum has a greater surface area than a submerged heating element, so the thermal gradient and the peak temperature difference in the honey, will be less when heating the honey from the outside, inwards.

Should the heat reach the external surface of the drum from:
1. Incident IR radiation ?
2. Circulated hot air ?
3. Circulating hot water, like a bain-marie ?
4. Or from an electrically heated jacket, externally insulated, that fits over the drum ?

 

[Nik_2213]

Don't forget heating/cooling coils intended for immersion are designed for good heat transfer, while barrel / keg is designed for handling robustness...

Also, If 'set', would this warm coil soften where it stood, allowing progressive sinking to working level ??

Whatever, given viscosity, probably better to heat from both outside via jacket --Search 'Drum Heater'-- and centre via immersed device, be it self-limited element or flow-coil per micro-brewery...

 

[Baluncore]

Don't forget heating/cooling coils intended for immersion are designed for good heat transfer, ...

Heating from outside the drum, will avoid contamination of the product.
The central axis is then being heated gradually, from all sides.
The large external surface area, will trump the heat transfer coefficient of a thin central element.

 

[Rive]

Also, any thoughts on ... some fans to circulate warm air?

That's the one I would vote for here. Easy to have the temperature below a set point and the uniformity of heat is about the fans only. Cheap, commonly used components, no exotic stuff.

 

[VABeekeeper]

Wow thank you so much for all the responses. I'm making my way through them and I'm seeing lots of great info, including actual calculations of the energy required. Awesome!

Believe it or not, this is not much honey at all. Some honey packing operations that are still considered small go through upwards of 50 drums a week. The industry standard way of warming honey is in a special hot room usually with radiant heat in the floors. This is an expense I'm going to avoid for now as it would require ripping up concrete, among other things.

I don't want to put any kind of heating coil in the honey itself, for one, because that would open a whole can of worms about contamination and sterilization of the coils between use and storage. Also it becomes less practical to scale up for 10 to 20 drums in the near future with methods like that or individual heating blankets, barrel bands and the like.

Now I'm gonna chew on what you all have provided. Thanks!

 

[VABeekeeper]

Once again, I'm so grateful for all the input from each of you. I'm reading and rereading your comments.

It's very helpful to hear your perspectives and have my own thoughts organized, confirmed, or challenged by yours.

 

[jrmichler]

If I could get the honey warmed in a week that would be wonderful

I'd like to set up an area for warming 10 drums.

I missed the part about a week to warm a barrel. That makes the problem a lot easier. The heat requirement to warm one barrel in a week is less than 100 BTUH. The calculation is $12,400 BTU / 168 hours = 74 BTUH$. A room at about 95 deg F, and gentle air circulation from a box fan or ceiling fan, would provide enough heat transfer to heat the honey from 60 F to 90 F in that time.

If you built a room 12 X 12 X 8 feet high, and insulated as follows:
Walls R20
Ceiling R30
Floor R10
Then the heat loss, assuming 95 F in the room, and 70 F outside the room, would be calculated as follows:
Walls $4 walls * 12 feet * 8 feet high = 384 ft^2$
Ceiling $12 feet * 12 feet = 144 ft^2$
Floor $12 * 12 = 144 ft^2$

Heat loss:
Walls $384 ft^2 / 20 * 25 deg F = 480 BTUH$
Ceiling $144 / 30 * 25 = 120 BTUH$
Floor $144 / 10 * 25 = 360 BTUH$

Total heat loss from insulated room = 960 BTUH. Heating the room plus warming 10 barrels at the same time would still have less than 2000 BTUH heat requirement. You could build a room with less insulation, but I do not recommend it. The floor needs to be insulated. Possibly two inches of foam under a double layer of 3/4" plywood. The plywood would be glued, screwed, and have the seams offset.

This heat requirement is far too small for a gas furnace. A possible heater would be a 1000 watt electric baseboard heater controlled by a barn thermostat. The photo below shows a barn thermostat. Note that the thermostat is calibrated to 110 deg F. Barn thermostats are built for use in environments that would kill residential house thermostats.

Do not try to save a few dollars by wiring a thermostat to a milk house heater as shown in the photo. After extended use, the plug connection resistance can increase to the point where the plug insulation melts. Ask me how I know this.

Don't forget a circulating fan. Most box fans or ceiling fans should be designed for continuous use at 95 deg F. I suggest a standard ceiling fan set to blow downward.