Cooling frame on the roof of the hive

Notes and tests Bumblebees PLUS

We tested the solution and here are some comments:

• If the frame has a large mass, part of the capacity of the cooling blocks will be used to cool it. Therefore, it is better to make the frame thin and insulate it well on the outside - the roof and sides.
• Depending on the solution and the volume of the “coolant”, the air temperature can be reduced quite significantly or even drastically by the lining, even by 15C – 20C. This is a large and sudden change in temperature. Therefore, we recommend a smaller cooling volume, which will not allow such a temperature jump and will not burden the bumblebees.
• When we tested the solution, in the extreme case, 15C was measured on the surface of the lining and 30C on the bottom.
• This solution has one disadvantage based on physics – condensation forms on the ceiling of the hive (the underside of the roof) during cooling, which can then drip into the nest. If there is a lot of it, the top can damage the nest. Humidity itself is not harmful, as long as the condensation does not flow into the nest.  
• Heat transfer from the hive space will increase if you place a wet rag under the cooling block – the contact area of ​​the cooling medium x the roof will increase significantly; however, the cooling block will “wear out” a little faster
• This solution does not solve improperly constructed hives. If such a hive is not well insulated, it is heated by warm ambient air from several sides. But that is a problem with the hive and not a problem with this solution
• On hot days, it is not worth letting the water warm up and then cooling it down suddenly. It is better to give a smaller number of blocks (12x max) before the temperature rises and replace the block during the day (if possible)
• Do not use this solution on days when maximum temperatures do not exceed 30 – 32C. On such days it is better to use more gentle cooling with a wet cloth and its evaporation
• The condition for using a thermometer has already been mentioned above.
• The placement of the thermometer is very important. There is no point in measuring the temperature in the lining, it is different in every place. Placing the thermometer (probe) in the air gap above the lining gives you at least some idea of ​​the air temperature in the hive. When using a cooling frame and the thermometer is cold air flowing over it, the measurement is not accurate. But it gives you some idea of ​​what it is like in the hive.
  If you use the same type of thermometer in your hives and place it in the same place, you can compare the temperatures in the hives. But do not expect to measure exact values.
• Be aware of the accuracy of the thermometer you use. The accuracy of cheap thermometers is generally poor, +/- a few degrees. Without calibration, thermometers show different values ​​at the same time. However, they can be easily calibrated at home and taken into account.

Conclusion

• Despite some disadvantages due to the laws of physics, this solution will allow to overcome critical temperatures on very hot days. Although it may be a relatively large temperature shock for bumblebees, it will allow them to overcome critical moments.
• We therefore recommend using it only on days when temperatures are expected to rise to 35C and only during the day. 
• After the outside temperatures drop, it is good to remove the condensate by ventilation (larger attachment, absorbent cloth under the roof) and return the humidity in the hive to values ​​around 90%