Reinforced convection heating, the task of which is to
quickly restore the temperature in the hive, which is necessary for the active
work of the bees, or for brood rearing. In spring and summer, its presence is
usually associated with a large number of sealed brood, and sometimes with the
presence of queen cells. In winter - with a sharp cooling of cluster of
wintering bees.
The
existence of this type of heating was assumed by us for a long time, but
unfortunately we did not have enough observations to confirm this effect. Some
data from our summer observations and from experiment conducted in winter time
allowed us to confirm our ideas. What is the meaning of our idea .... The point
is, that for heating of a large volumes as quickly as possible, or for fixing
some kind of emergency situation, there is needed the most efficient method of
heating and transferring of heat. This is convection, which, in combination
with heating of the bee itself, can provide the fastest heating of the nest,
the wintering bees' cluster, or the hive as a whole.
The
use of this heating method in conjunction with the other three known methods -
heat insulation, passive heating, active heating with generation of
vibro-acoustic signals without movement of the wings, allows not only to
maintain the temperature in the most economical way, but also to eliminate the
consequences of emergency situations. In addition, the work of the bees, as an
active process, is also accompanied by the release of heat. This is not a
heating method, but this process participate in the overall picture of creating
and maintaining heat in the nest too.
What
exactly the mechanism of urgent heating is ...
We assume, that in addition to silent heating, and heating with thorax
vibration, exists the type of heating, which use wings flapping as a source of
heat generation. This mechanical loading reduces the resonant frequency of
vibration of the muscles of thorax, but increases the amount of work done, as a
result, producing more heat. This also
improves heat removal and provides forced convection, redistributing the heat
in an optimal way over the volume of the nest or in the winter cluster.
Why
is it better to flap wings with a frequency of about 100 Hz, than to vibrate
with a higher frequency? Or why not to flap wings with a frequency much more
than 100Hz? It is thought because in all
cases Nature avoids the waste of energy and life resources. Unfortunately, any
living being is not forever. Each has its own resource. And everyone save and
cherish it, lengthening their lives.
And
what about vibrations and flapping of the wings? In order to understand this,
we will give an example: When we freeze, we begin to shiver. Muscles vibrate,
producing heat. If this does not help and we continue to freeze, then the
shiver becomes stronger ... we just start to shake. Muscles begin to perform
even more work, releasing more heat. But the surest way to quickly warm up in
the cold time, is to start waving hands and running. So, our muscles make more
work, and produce more heat. Further,
our internal convection starts working. Yes, and we have it too. Convection of
blood begin to transfer heat to our internal organs, warming them. We get warm,
stop shivering, and stop running and waving our hands. Our body warmed up and
went out of the critical phase of cooling.
Realizing
that we all have a single Creator, we draw a direct analogy, believing that the
general algorithm for the functioning of living beings is one and the same ...
And the bees act quite similarly to us... When it become cold, bees begin to strain muscles, producing heat
without vibration. By the way, we are also know how to do it ... If this does not help, the bees begin to
vibrate, emitting more heat, thanks to the accomplishment of more work. If this
does not help, then the bees begin to flap their wings, as we do with our
hands... By doing more work, they achieve production of more heat! Moreover, in
the result of these actions, the bee blows on her own body, and on everything
that surrounds her...
What
is the reason for the importance of such a blowing ... The reason - is the
efficiency of heat transfer ....
We
have no doubts about the effectiveness of
convective heating. Convection is a process of heat transfer during
moving of volumes of liquid or gas (fluid) from the place with one temperature
to the place with another temperature. In this case the heat transfer is
inextricably linked with the transfer of the medium itself, which is
essentially a heat carrier.
Convection
of heat is always accompanied by conduction of heat. The joint process of heat
transfer by convection and conduction is called convective heat transfer.
The
intensity of transfer of heat( or cold ) from one medium to another is
characterized by the transfer coefficient, which depends from each environment.
If environments have dramatically different coefficients of heat transfer, the
heat transfer rate is determined by the environment, which makes it the most
slowly.
What
else affects the intensity of heat transfer. Of course, it's the relational
speed of movement of one media over other. As you know from the basics of heat
transfer, the heat transfer coefficient increases with increasing of the speed
of heat carrier, in our case air flow. But not indefinitely. There is an
optimal ratio of speed of air flow, relative to the stationary environment,
which is characterized by maximum quantity of the transmitted heat, with
expenditure of optimal amount of energy to move the heat carrier. In our case,
the two environments are - the body of the bee, and blowing air. If you will use
forced blowing of solid body by air flow, instead of free convection, then heat
transfer coefficient increases twice.
Additionally,
the heat transfer depends on the shape and geometry of the body, blown by the
air. The larger the contact area of solid body with air flow, the higher heat
transfer. The less streamlined is the shape of the solid body, blown by the
air, the higher the coefficient of heat transfer.
In
all these, bees are not too much lucky. Their streamlined body covered with a
chitinous exoskeleton is not the best heat exchanger. This means that the rate
of heat transfer from the body of bees to the air flow will not be very high.
So, the flapping of the wings provide air flow, removing heat from the body of
bees and transferring it to the brood and other parts of the nest can't be very
high. And frequencies rate of emitted sounds can't be very high.
Such
sounds with the frequencies above 20 Hz. people can hear as a very low sounds,
and our device can register them, if their frequencies are higher than 70
Hz. And indeed, our device captures such
signals at times of tense situations in the bee family. The frequencies that we
fixated, were in the range of about 100 Hz and by the type of picture of the
spectrum could be attributed to the signals, created primarily by bee wings,
since they have the correct multiplicity of harmonics x2, x3 ... etc.
And
how do the bees use their heating
capabilities at different situations of their life ...
Settling
into a new home, the swarm immediately begin to maintain the temperature,
necessary for the beginning of egg laying by the queen. Then the bees begin the
process of maintaining the temperature using thermal insulation and passive
heating of the nest. Further, if it is necessary to maintain the temperature in
a larger volume, the bees use additional
active heating. In cases of a sharp drop in temperature, the bees immediately
use urgent heating. After restoring the temperature balance, this type of
heating stops and the bees go over to more economical forms of heating.
Let's
consider the examples of our observations, which we believe, confirms our
ideas...
Recently,
we conducted an experiment on cooling the nest of hibernating bees with the
fixation of changes in the background signals in the hive. The results were
very interesting. At the outside temperature of -15C , we received data,
possibly confirming our hypothesis about the "conditioning" of the
hive, that is, the use of ventilation of lowest force, in order to improve the heat removal from the bee's
body in emergency moments of severe cooling of the nest ...
We
assumed that in addition to heating, which is usually silent, heating with the
performance of flapping of the wings can be used by the bees. This reduces the
resonant frequency of vibration of muscles of thorax of the bee, but adds
improved heat removal and provides forced convection.
When
we removed the warming pillow and left only a thin fabric, separating the upper
part of wintering bees cluster from the street and made measurements, we saw
how the signals characteristic for various jobs in the warm nest began to
change, and turned into signals of the lowest frequencies ventilation, and thorax vibrations which in sum provide
the best heating and convection of warm air.
When
the pillow was returned, after 20-30 minutes, the signals changed again, and
began to correspond to the performance of in-hive works and feeding... We
managed to simulate this situation two times in a row. The predominant signals were - heating and convection.
Further
research conducted using our archives, showed, that this situation is not
unique. The same signals were recorded in the summer in a very specific
situation. This once again confirms the immutability of the principle of life
support in bees, and its independence from the season of the year.
The
appearance of the signals, was absolutely similar to our winter urgent heating,
but was recorded in June, in the family, in which there was sealed brood and
queen cells. And we already expected a
close exit of the first queens. It should be noted, that at this time, in June,
it was pretty cool. The bees in the hive were less than they needed, because
these families, in which we were waiting for the queens, were practically
divided in half. Thus, the number and age composition of bees in these families did not allow them to
use passive or active heating. And the bees used the most efficient method of
heating - heating with convection or as we called this effect - "urgent
heating with convection".
As
another confirmation, can serve an experiment, in which was used our observation hive, which we moved from sunny
outdoors place to the cold room. In this situation, when the bees placed on the
frame with sealed brood felt cold, they shifted from the passive state to active
... At first, they made attempt to
retain heat, and then they shifted to active heating and urgent active heating.
Here you can consistently see all the phases we talked about. And in the last
phase, it seems to us, we can see the signals of both types of heating - of
active heating and of urgent heating with convection.
Yes,
unfortunately everything is not so simple. We do not yet know, whether there is
a combined mode, when a bee can vibrate warming the chest, and at the same
time, to blow on itself using her wings. Apparently, since the same muscles are
involved in both modes, the bees cannot perform two types of work at the same
time. But they can do it in turn! After all, the vibro-acoustic signals which
were recorded by the scientists, were lasting for about 0.2 seconds or less.
This means, that for our eyes, a
periodic change of heating process to flapping by the wings, will be not
noticeable... But the device, based on the Fourier algorithms, will record two
chains of pulses with different frequencies of the fundamental tone - one will
correspond to the heating with the use of vibration of the thorax, the second
will be created by heating with the help of wings flapping ! The possibility of
this, we have to find out in our further researches.
There
is another possibility that is much more prosaic. It is possible that in this
situation we hear a few bees doing the work on heating the brood. But one of them use "active heating",
and the others have already switched to "urgent heating", considering,
it seems, that it is better to overdo, than to freeze sealed brood.
it seems to us, that on the diagram
it should look like this:
And
only Apivox algorithms, after processing the signals for a long period of time,
will determine the priorities in this mix of signals, and will give diagnosis
about the state of bees, in correspondence with the average situation for the
selected time interval.
Thus,
we can once again state the presence of four modes of thermoregulation in bees.
-
Performance of every-day in-hive works, leading to heat generation due to
metabolic processes, and further heat preservation due to thermal insulation
and creation of clusters.
- Passive heating with virtually no any
vibration of the thorax, but with the heating of the bee's chest.
- Active heating with powerful vibration
of thorax and creation of vibro-acoustic
signals in the low frequency zone of the working range, without the
participation of the wings, which are fixed in slightly open position.
- Urgent heating with the work of the muscles
of the thorax in resonance mode, similar to ventilation, but in which the wings
operate at extremely low frequency,
which leads to the development of the maximum amount of heat, and creating a weak air flow, providing improved
removal of heat from the body of the bee, and spreading it inside the hive.
