bbka news- Wide dummies: more heat transfer crimes

[user 6228]

The article on wide dummies in the BBKA news has highlighted again the misconceptions about heat transfer in hives.
It propogates the myth that if you only reduce the volume available to the bees you will reduce heat loss.
In this instance the author has forgotten that air will convect in to gaps around and importantly over the tops of the dummies. In addition convection inside the dummies will occur.

if you reduce the surface area conducting heat to the outside world you will most likely reduce the volume, however you can reduce the volume without reducing the conducting area, as this author has demonstrated.

 

[oliver90owner]

So are they talking dummy frames, rather than insulated dividers?

Not particularly interested in most of the bbka trash, put out by dinosaurs in the beekeeping world.

 

[madasafish]

I use a much easier solution - Celotex dummy boards to deal with interior space. MUCH easier to make, insulation and easier to handle..

Plus external insulation..

Our Association apiary is trying these wide dummies.. I made 6 for them - a real pia compared to Celotex ones.

(My Celotex is as usual cheap via ebay)

 

[Madge]

...

if you reduce the surface area conducting heat to the outside world you will most likely reduce the volume, however you can reduce the volume without reducing the conducting area, as this author has demonstrated.

I use a much easier solution - Celotex dummy boards to deal with interior space. MUCH easier to make, insulation and easier to handle..

Plus external insulation..
...

If I understand Derek correctly, then your insulated dummies (same as mine - I also use them) reduce volume and not the conducting area so we might as well dump them and replace them with any ordinary frames (drawn or just foundation).

In your case, MaaF, your external cosy probably helps. I don't use cosies and never will.

So I suppose, Derek, for those of us not using cosies, are you saying the insulated dummies are useless and we should perhaps replace them with a sheet of something that spans from top to bottom and from the front to the back of the hive?

 

[Gilberdyke John]

The article on wide dummies in the BBKA news has highlighted again the misconceptions about heat transfer in hives.
It propogates the myth that if you only reduce the volume available to the bees you will reduce heat loss.
In this instance the author has forgotten that air will convect in to gaps around and importantly over the tops of the dummies. In addition convection inside the dummies will occur.

if you reduce the surface area conducting heat to the outside world you will most likely reduce the volume, however you can reduce the volume without reducing the conducting area, as this author has demonstrated.

I don't disagree with your assertion that convection losses will take place around the wide dummy frames. However let's keep in mind that the time of year and external temperatures together with the level of bee activity affect the situation. If you have an active colony, expanding and drawing comb, the dummy simply steers the comb drawing etc to the space available. Any savings during those times are in the words of an old workmate "three quarters of f*** all".
In colder times a "seal" to inhibit convection is very much more important and I use 1" kingspan cut to a close fit with floor, sides and crown board.
Works for me

 

[user 6228]

If I understand Derek correctly, then your insulated dummies (same as mine - I also use them) reduce volume and not the conducting area so we might as well dump them and replace them with any ordinary frames (drawn or just foundation).

In your case, MaaF, your external cosy probably helps. I don't use cosies and never will.

So I suppose, Derek, for those of us not using cosies, are you saying the insulated dummies are useless and we should perhaps replace them with a sheet of something that spans from top to bottom and from the front to the back of the hive?

if your dummies dont seal to the roof and side - they arent insulating much at at all
if they arent packed with insulation they are doing even worse...
if the dummies are not packed

 

[user 6228]

I don't disagree with your assertion that convection losses will take place around the wide dummy frames. However let's keep in mind that the time of year and external temperatures together with the level of bee activity affect the situation. If you have an active colony, expanding and drawing comb, the dummy simply steers the comb drawing etc to the space available. Any savings during those times are in the words of an old workmate "three quarters of f*** all".
In colder times a "seal" to inhibit convection is very much more important and I use 1" kingspan cut to a close fit with floor, sides and crown board.
Works for me

thats not the case, In spring summer,
more of the hive is required to be at brood temperature, or above for honey ripening, increasing the heat loss area. The average spring summer temperature in this country is a long way bellow 35C and the winds still blow.
Heat requirements and losses go up in spring and summer not down. a bit counter intuitive

 

[pargyle]

I use dummies made out of 50mm Kingspan/Celotex which fit snugly to the walls of the hive and up against the crownboard. In addition, any vacant space in the hive on the other side of the dummy is filled with 'blocks' of Kingspan that I bind together with barbecue skewers and aluminium tape - I have various sized 'blocks' to accommodate different sizes of space that needs filling.

I've also used plastic bags full of the polystyrene cocktail sausages that come by the bucketful when you order things from Paynes and they seem to work quite well - l overfill the bags and then squash them down in the space I want to fill.

 

[madasafish]

My dummies are very close fitting..

 

[jenkinsbrynmair]

Just saw the title of this thread - too many words I thought; BBKA and dummies - where's the news there?

 

[Madge]

if your dummies dont seal to the roof and side - they arent insulating much at at all
if they arent packed with insulation they are doing even worse...
if the dummies are not packed

The dummies are insulating, and I use poly hives. Doesn't the fact that the dummies reduce the space considerably help the bees to stay warm; and doesn't the air trapped between dummies also contribute to the insulation and warmth of the hive?

Ps: I haven't yet lost colonies over winter - so perhaps I'm doing something right.

 

[user 6228]

The dummies are insulating, and I use poly hives. Doesn't the fact that the dummies reduce the space considerably help the bees to stay warm; and doesn't the air trapped between dummies also contribute to the insulation and warmth of the hive?

Ps: I haven't yet lost colonies over winter - so perhaps I'm doing something right.

"Doesn't the fact that the dummies reduce the space considerably help the bees to stay warm"

No - the heat flow out of an enclosure is not related to its volume
(conduction :Heat flow is proportional to temperature gradient times the area.)

"and doesn't the air trapped between dummies also contribute to the insulation and warmth of the hive?"

Maybe - it depends on the detail of the geometry involved.

 

[Madge]

... No - the heat flow out of an enclosure is not related to its volume
(conduction :Heat flow is proportional to temperature gradient times the area.) ...

I'm not in my comfort zone talking about heat flow and temperature gradients - so, just based on my instinct, wouldn't the temperature gradient be influenced by what is inside the hive?

In other words, if the box contains just eight frames of bees surrounded by empty space, wouldn't that give a different temperature gradient to eight frames of bees surrounded by empty drawn comb, and again different to eight frames of bees surrounded by insulating dummies?

 

[itma]

The dummies are insulating, and I use poly hives. Doesn't the fact that the dummies reduce the space considerably help the bees to stay warm; and doesn't the air trapped between dummies also contribute to the insulation and warmth of the hive?

With a poly hive, you aren't going to increase the insulation much by adding (loose) fat dummies. Wedge in blocks of celotex so that the walls are effectively thicker, and you would improve the insulation of the end walls - but since the side walls (and roof) were unimproved, you wouldn't be reducing the total heat loss by much.

Where fat dummies may help would be in place of empty space beyond a thin dummy board. Anything that restricts air movement in the unoccupied part of the hive should help reduce heat loss through air change, or draughts as we used to call them (which is slightly different to insulation).
But I'd expect that extra frames full of stores would be much better for the bees' chances than fat dummies!

 

[Madge]

With a poly hive, you aren't going to increase the insulation much by adding (loose) fat dummies. ...

Where fat dummies may help would be in place of empty space beyond a thin dummy board. Anything that restricts air movement in the unoccupied part of the hive should help reduce heat loss through air change...
But I'd expect that extra frames full of stores would be much better for the bees' chances than fat dummies!

Thanks Itma. I understand that a slab of extra insulation wall to wall and top to bottom is better than dummies, but I think dummies help - perhaps as you say, to do with the air flow.

I've been using Ian Craig's method of over-wintering on double brood with space reduced in each box with insulating dummies - so they do have their stores of food!
Kitta

 

[user 6228]

I'm not in my comfort zone talking about heat flow and temperature gradients - so, just based on my instinct, wouldn't the temperature gradient be influenced by what is inside the hive?

In other words, if the box contains just eight frames of bees surrounded by empty space, wouldn't that give a different temperature gradient to eight frames of bees surrounded by empty drawn comb, and again different to eight frames of bees surrounded by insulating dummies?

Inside the hive cavity heat is transported to the walls by air movement , it then passes through the walls and roof by conduction. You need to reduce the amount of wall/roof the cavity air can reach, and if not reduce , then restrict the air flow between the cavity and the walls and roof.

 

[MartinL]

"Doesn't the fact that the dummies reduce the space considerably help the bees to stay warm"

No - the heat flow out of an enclosure is not related to its volume
(conduction :Heat flow is proportional to temperature gradient times the area.)

Wrong!

You're forgetting thermal mass!

 

[user 6228]

Wrong!

You're forgetting thermal mass!

your argument is timeless

thermal conductance = watts per K
thermal capacity = joules per K

or the size of the tank doesnt influence the flow rate out of the tap

 

[beebot]

or the size of the tank doesnt influence the flow rate out of the tap?

But water comes out of my small water butt much slower than my big one.

 

[oliver90owner]

Same depth of liquid in the tank would have been a better way to put it in the post. Flow is a function of pressure for fluids.