There is nothing like a good cup of proper tea, and a post inspired by it.
It all started when a good friend of mine got me a thermally insulated mug as a present (they’re brilliant btw (friends and thermally insulated mugs)). I wanted to enjoy my tea without it going cold every 5 minutes, after repeatedly being pulled off, job after job, then coming back to find another cold mug of tea. After a while, there comes a breaking point.
A thermally insulated mug was the answer, but what was the question. How does it work. Well!
When particles are hot they bounce around banging into each other causing friction, causing heat. eventually the particles get so hot and bounce apart so much they start to tear and form bubbles in the water. If you continue to heat the water more the particles get so shaky they bounce off pretty much everything with a lower effective mass causing it to rise upwards (although a better description is the air is falling down under steam particles causing the steam to be pushed up, like water in a heavy fluid). A good way to combat heat loss is to place the fluid in a container and suspend it in a vacuum as then the particles have nothing to bounce off and less energy shifted from where it needs to be (in the cup). There are practicable limitations to have a perfect container suspended in a vacuum. But we can get something close.
You first get a un-suspecting victim and tell him/her to stand in the corner with a left handed screwdriver…
As we know heat rises (or rather gets displaced by colder denser particles with more effective relative mass). We can start by keeping in the steam, by placing a lid on the container and that’s where the most heat is quickly transferred.
We can then start working on the vacuum theory. But suspending a container inside another container and removing the air inside, we can make the walls of our vacuum mug. The high energy particles now can’t transfer easily to the outside as there is nothing there for energy to transfer to.
The materials used can play a big roll in keeping our liquid hot as well. Dense materials have lots of particles for the energy to transfer to, making materials like metals good conductors. Materials like wood and expanded polystyrene (horrible packaging balls) with very open ‘airey’ structures, excellent insulators. Fun fact: Some disposable cups are actually made of expanded polystyrene foam for this reason You can’t really use expanded polystyrene as a permanent cup material as when you put it in the dishwasher it would melt or tear. So something more rigid is required. The material also needs to be food grade, non-toxic. A more appropriate plastic like PTFE or Polycarbonate. Un'whala! Your perfect mug design, brought to you by science.
If you don’t have a awesome friend with a sexy thermally insulated mug (then I’m sorry). You can always try helping the situation by being careful where you place your cup. By placing you mug on a wooden surface rather than you metal Snap-On toolbox will help with the thermal transference from the bottom of the mug (I used a block of 4x4). Placing a lid on the top of the mug will help stop the pixies from escaping (something like a sheet of plastic or a Pringles lid can work wonders).
And there we have it, a bit of a ramble on the thermal properties of the humble mug. So drink up and don’t let it go cold!
Yours, The Enginer’d