I've one of those gel-filled bottles that is heated in a microwave oven (the sort that was withdrawn from sale due to an old dear killing herself by overheating one). It's getting a bit ancient now, so I'd like to get another one (or even a couple, for future use). I can find the wheat-filled things and some where I'm not sure what is in them, but anyone know of a source of the real thing, please?
Here is an expensive one.
Aha! The 'Hottie' gel filled hot water bottle. ebay would be the place for them.
Tim nw
With modern materials and care on the amount of air in it, surely the ideal filler is, um water?
Brian
Well before these devices I can well remember a thing that looked like a conventional hot water bottle that had a kettle type plug on the stopper end. From what I could see you plugged it in, and it cut off when it was a safe heat and you then took the lead off and put it into your bed . Seemed a nice idea, but I assume some idiots used to plug it in inside the bed and either electrocuted themselves or set fire to the bed with them as they are not around today.
Brian
No it'd be some sort of oil, the trouble with water is it's relatively low Specific heat capacity, i.e it cools down to quick. Notice that portable eleftric radiators tend to be oil filled rather than water filled.
______________________________________________________________________________________________________________
I think the point of the gel is that you get the latent heat released on the phase change from liquid to solid which is (usually) much greater than the heat released by the same amount of liquid cooling from any safe temperature. It also has the additional benefit that the liquid stays at the same (freezing point) temperature until it's all solid. C/f the freezer packs for cool boxes.
I have - and even occasionally use when I remember them! - gel handwarmers which rely on this. You "melt" them in boiling water, let them cool, then trigger their solidification when you want the heat. They're too small for a bed though - unless you just want to warm a couple of vital bits :) Lidl have them dirt cheap from time to time.
I remember those freezer packs well from camping as a kid.
They were of course pretty useless. OTOH we discovered that a 2 litre lemonade bottle filled and frozen is really rather good (just because it's so much bigger). We then found a campsite who had also discovered this and who had a stack in their freezer they'd swap for 50 euro-cents a go. I hope this practice spreads.
Eh? Water is 4.18 kJ/kg/K, oils struggle to make 2kJ/Kg/K.
Oils are generally insulators, non-corrosive and have higher boiling points at least for the relatively vicous "transformer" oils.
Also with the lower heat capacity heat up quicker than a water filled one would. A water one would take longer to cool as well making room temperature harder to control due to under/over shoot.
And not much chance of a steam explosion.
It needs twice the time of my current one, so should hold a lot of heat. Bit worrying that it's described as "rigid" - doesn't seem too comfortable.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.