Moisture Board versus Quilt Block? - Page 4
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  1. #61

    Default Re: Moisture Board versus Quilt Block?

    Of course, I recognize that the conventional wisdom is not exactly correct. What is likely going on is that air is being warmed by the cluster, and as a result, there is a continual flow of air from below the cluster, moving up around the cluster, and then up toward the top of the hive. As a result of this flow, colder air is being drawn into the flow from the sides of the cluster, so conduction losses through the air do not make it to the sides of the hive at the level of the cluster. However, the cluster radiates heat, pretty much as a black body. In addition, heat is conducted through the frames and combs which pass through the cluster.

    In fact, I think it is Rusty Burlew over at honeybeesuite who has a fancy thermal camera that can "see" the location of the cluster through the hive walls.

    However, if the cluster is touching or near a wall, as it must be at some times of the winter, then it will lose a lot more heat through that wall.

    I haven't seen any quantitative information on how much water the bees need in order to liquify their food. While the water from burning honey to heat the hive will likely be in the vapor state, exhaled during respiration, it will likely condense to some extent somewhere in the hive.

    I hadn't thought about bees foraging for water outside of the hive in the winter. A lot probably depends on local conditions, and also on the bees. I will have to watch the bees next time they are out to see if that is what they are doing.

    This winter I have three colonies wintering in 6-frame hives. I insulated those hives in the narrow direction, since it seemed to me they would have difficulty accessing the stores on the outer walls. Since the colonies are pretty big, I suspect when the cluster is loose it touches both side walls. When I peeked at one on a 30F (-1C) evening, the cluster was at the bottom, and clearly filled the 5 frame gaps to the bottom. Couldn't see up the outside to see if they were there too. What I have noticed is that they are unusually active for the weather we are having. It suspect they perceive the conditions are warmer than they would without the insulation.

    Most likely they are using more food, as they are more active. However, if it were really cold outside, not 35F (2C) as it was today, they would probably be using less, as they would be in the small cluster/no brood mode of winter survival.

    When I actually weighed hives regularly through the winter (only did that one year, as it gets difficult) the bees used the least of stores when the weather was coldest.

    I have heard there is some recent research showing colonies use less stores and are stronger in spring if the hives are insulated. I haven't found the actual research though. It would certainly be worth looking at.

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  3. #62
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    Default Re: Moisture Board versus Quilt Block?

    Quote Originally Posted by Robert Holcombe View Post
    FYI: Look up Specific heat of water, vaporization requirements, etc. Condensing vapor to water releases 2,261 J/g which is about 5x more than energy than to heat the one gram of water from 0 to 100C. It is not a trivial number. Honey and air are pretty good insulators.
    You probably meant - honey is a good heat sink due to the high thermal mass.
    Thermal transfer resistance of honey is not that high - to be a good insulator.
    Thermal mass <> thermal transfer.
    Former "smoker boy". Classic, square 12 frame Dadants >> Long hive/Short frame/chemical-free experimentations.

  4. #63
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    Default Re: Moisture Board versus Quilt Block?

    Quote Originally Posted by crofter View Post
    ........That is the reason I state that the folklore statement that "The bees only heat the cluster, not the hive" is simply not correct.
    OK, I knew this.
    Unsure who even argues.


    Back to my "heating the Universe" example.
    The energy intake by the Universe from me is > zero in theoretic sense.
    And yet it is ~zero - so negligible.

    The energy loss BY ME - significant - at the same very time.
    My feet are cold, for sure, in this basement.
    Former "smoker boy". Classic, square 12 frame Dadants >> Long hive/Short frame/chemical-free experimentations.

  5. #64
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    Default Re: Moisture Board versus Quilt Block?

    I meant what I said and I appreciate the "heat sink comment". In the world of relative values I will resort to the Wikipedia Honey site comment: " Unlike many other liquids, honey has very poor thermal conductivity of 0.5 W/(m⋅K) at 13% water content (compared to 401 W/(m⋅K) of copper), taking a long time to reach thermal equilibrium.[60] Due to its high kinematic viscosity honey does not transfer heat through momentum diffusion (convection) but rather through thermal diffusion (more like a solid)" . Not as good as EPS foam at 0.033–0.046 W/(m x K) but pretty good as a natural product used for other important purposes.

    The interesting thing about liquid honey, to me that is, is the low convection effects and characterized by conductive values less than water or pine wood used to make enclosures. From a material point of view it is thermally more resistive than current, typical hive construction materials. Coupled with its' specific heat characteristic, it make honey a player in buffering rapid temperature swings. It is also isolated in small cells which further resist convection currents unlike standard hive air which is a poor conductor but very susceptible to circulation currents and increasing convective heat transfer coefficients. Convection currents could lead to significant heat loss from the cluster - unless blocked.

    One day it will be interesting to see a complete 3D dynamic thermal model of a cluster + various hive designs which also takes into account bees system control abilities like thermal regulation, expanding and compressing the cluster, opening through cluster vents and "dew point" control (a hypothesis of mine) based on limited data as well as humidity - fanning effects.

  6. #65
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    Default Re: Moisture Board versus Quilt Block?

    Quote Originally Posted by Robert Holcombe View Post
    I meant what I said and I appreciate the "heat sink comment". In the world of relative values I will resort to the Wikipedia Honey site comment: " Unlike many other liquids, honey has very poor thermal conductivity of 0.5 W/(m⋅K) at 13% water content (compared to 401 W/(m⋅K) of copper), ......
    I would certainly not use water as an insulator:
    Water 0.5918[12]
    https://en.wikipedia.org/wiki/List_o...conductivities

    Which is very similar to honey at 0.5.


    To speak of good natural insulators, dry snow is a good example (order of 10 difference from honey/water):
    Snow (dry) 0.050[4]–0.250[4]
    Or indeed air (at about 0.02 - 0.03) - also order of 10 difference from honey/water.
    Even generic soft wood (at 0.1-0.2) is much better insulator than honey.

    These are the proper materials to compare honey with for thermal conductivity, not aluminum or copper.
    Last edited by GregV; 12-14-2019 at 12:36 AM.
    Former "smoker boy". Classic, square 12 frame Dadants >> Long hive/Short frame/chemical-free experimentations.

  7. #66
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    Default Re: Moisture Board versus Quilt Block?

    Robert, I am sure Greg must have missed the convection component of the equation.

    Interesting forehead slapper for me too. I had considered honey to be similar to water in conductivity. The convection factor in both it and air is a game changer!

    Thanks.
    Frank

  8. #67
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    Default Re: Moisture Board versus Quilt Block?

    Quote Originally Posted by Robert Holcombe View Post
    <Snip>

    Finally I have never seen a test to verify condensation on the inner cover kills colonies. I have seen bees lined up along the the inner surface of a hive box to cover interface drinking the water coming in from a Nor'easter. Maybe that is why bees choose tree cavities. The top central surface or "top cover" is very well insulated with no top vent.
    What about all the horror stories about upper surface condensation dripping on the clusters and killing the bees. "Cold does not kill the bees, condensation does" etc.

    I agree that insulation to prevent condensation on the top is the way to eliminate potential problems with dripping. Also reduces the amount of heat the bees have to produce to maintain their desired cluster temperature. Added benefit, less honey consumed and less moisture produced.
    Frank

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