Victoria Blue World Aquarium WYSIWYG review

[martinmcnally]

Definitely have to say this was the best packed shipment of corals I have ever received. They were bagged 5 times and the carbon pellets were a good touch too to soak up any nasties that accumulate during shipping. All corals doing well!!

However I have noticed this trend lately of taping the heat pack to the lid and I have been wondering why.

Heat rises!

Heat is transferred in one of 4 ways:
Radiation - Needs to be infra red heat (which a heat pack is not)
Conduction - Air (and packing peanuts) are very poor conductors of heat.
Convection - A convection current cannot start inside the box because heat rises and the heat source is at the top.
Advection - Doesn't happen because nothing inside the box is moving.

If you want the best use of a heat pack with also protecting the corals place the heat packs in the center of the bottom of the box, put some packing peanuts on top of them or some Styrofoam less than size of the footprint of the box. The corals can then go on top of that. That way they are not touching the heat pack and the heat back is free to create a convection current inside the box. The warm air will rise up over the corals and cool air sink to the heat packs. Thus the corals stay warmer. If the heat pack never gets hotter than the water temperature then the corals can go right on top of them. Then you get convection and conduction!

That thermal conductivity class did come in handy after all haha. Lord Kelvin would be proud haha we went to the same university although he died 92 years before I got there.

[sphelps]

In reality it makes no difference where the heat pack goes as your main concern is the heat loss through conduction through the insulated box resulting from a temperature differential. There should be little to no air in a properly packed box and it should also be air tight. The heat loss will be the same regardless whether it's placed on the bottom, side or top. If you're attempting to make free convection flow patterns in your shipping boxes then you're doing it wrong. The temperature in the box and the bags of corals should and will eventually be the same during shipping. Heat packs do get hotter than safe temperatures for livestock so direct contact of the packs and bags containing livestock is not recommended. BWA is correct, the bigger issue with shipping is actually too hot, not too cold.

They are placed at the top simply because it's the least likely place to get wet. 9 times out of ten the bottom of shipping boxes arrive wet or flooded. No other reason, it's just common sense.

On a side and completely unrelated note, three types of heat transfer exist, advection is just a form or convection (forced convection). Radiant heat transfer occurs in all objects provided there is temperature difference, so a heat pack certainly does transfer heat through radiation.

[davej]

Something else to consider is that the heat packs need a supply of oxygen for the chemical reaction to take place and create said heat. I the box is air tight the oxygen will get used up heat producing reaction will stop.

[RedCoralEdmonton]

Coming from a (not really) competitor.... the packing methods they used are top notch, with regards to the heat pack placement, this is industry standard, in such a small space placement isnt critical, if you were to place it under the bags, you would have over heating for the first few hours which would be worse for the shipment. Having a shipment a little colder isnt a huge deal with coral (not with fish). I like seeing the thick boxes and the heat packs, this is what you want from a supplier. Seeing as how the shipments made it, and are flourishing is the key. This is the end game for any hobbyist, a healthy thriving coral!

Cheers,

Steve

[sphelps]

Originally Posted by davej

Something else to consider is that the heat packs need a supply of oxygen for the chemical reaction to take place and create said heat. I the box is air tight the oxygen will get used up heat producing reaction will stop.

Hmm interesting, maybe suppliers should start drilling some air holes in their boxes
The amount of O2 needed is minuscule at best, boxes should be sealed air tight, allowing air in would be quite foolish and counterproductive.

[kien]

don't argue with Steve, he knows a lot about "hot air" !!

[sphelps]

Originally Posted by kien

don't argue with Steve, he knows a lot about "hot air" !!

This is true, I'm also good at blowing smoke up certain places