Heating/Cooling Coaster
Apr. 6th, 2023 06:59 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
carlfoxmartenA few years ago, I'd found a dual-function drinks coaster. At the moment, the house I'm living in doesn't have anywhere near enough insulation, so I'd been looking for a drinks coaster that was capable of cooling my drinks. Having a glass of juice with lime in it was fairly effective at keeping me cool, but only when the drink wasn't allowed to get that hot.
Anyway, while most electric drinks coasters just heat your drinks, the one I'd found also included a cooling function. Though, I suspect it's less effective given that it's USB powered instead of wall-powered.
Now, in larger heat-moving systems, a highly compressible gas is used to literally pump heat (hence, "heat pump") around, but in much smaller systems like this, you can buy solid-state devices that move heat around to a less efficient extent. Called Peltier devices, if you hook it up to power the right way around, it uses the flow of electricity to move heat from one side to the other. A higher voltage moves more heat around, in this case, and while it comes with a USB cable by default (thus running at 5V), you are supposed to be able to buy a 9V power adapter separately, which increases the amount of heat it pulls out of your drink.
On the opposite side of the coin, if you apply the power in the opposite direction, it instead generates heat, and the power switch on the front of the coaster toggles which direction the power is applied.
Unfortunately, the cooling function has two separate flaws. The first being a small fan. This fan blows air across the bottom side of the Peltier device, with the intent to blow the heat pulled from your drink away, but it's noisy enough to be a distraction most of the time.
The second being that cold doesn't rise. Which means that, if your drink starts out being warmer, you end up with a temperature gradient in your cup, with the bottom layers being colder than the top layers.
With the modicum of success I'd found using this device, and finding that its price had dropped afterwards, I'd bought a couple more. The idea being to experiment with it. For example, fixing the fan noise problem would be simple enough hardware wise, by replacing the original fan with a larger module, which is quite easy to obtain and I've already done so. Structurally, however, I'm still trying to figure out how to support the whole thing, as there's nowhere near enough empty space for a fan of this size in it, so I basically need to build a new frame to support it. Given my limited set of tools and experience, a lot of thought is required here.
But, that doesn't solve the second problem. How do you make an entire glass of water (for example) colder at the same time? Do you mount the Peltier device so it makes contact with the side of the glass instead of its base? Being spring-loaded such that it pivots back and forth as necessary to make contact with the side of the glass, no matter what angle it's on? Maybe with a flexible air duct from the base to the bottom of the heat sink already attached to the Peltier device, so the fan in the base forces a lot of air through it?
Unfortunately, that concept doesn't quite work here, as all of my glasses are round in two dimensions, such that a flat object pressed against them would make contact at a single point, not even a line. Thus, heat transfer would be highly inefficient.
You can see my dilemma, and why I haven't tried doing anything else with this concept just yet. Granted, with how many of these I have right now, I could probably make one that just has a larger fan and contacts the bottom of the glass, then keep fiddling with another to see if I could make it any more efficient.
Anyway, while most electric drinks coasters just heat your drinks, the one I'd found also included a cooling function. Though, I suspect it's less effective given that it's USB powered instead of wall-powered.
Now, in larger heat-moving systems, a highly compressible gas is used to literally pump heat (hence, "heat pump") around, but in much smaller systems like this, you can buy solid-state devices that move heat around to a less efficient extent. Called Peltier devices, if you hook it up to power the right way around, it uses the flow of electricity to move heat from one side to the other. A higher voltage moves more heat around, in this case, and while it comes with a USB cable by default (thus running at 5V), you are supposed to be able to buy a 9V power adapter separately, which increases the amount of heat it pulls out of your drink.
On the opposite side of the coin, if you apply the power in the opposite direction, it instead generates heat, and the power switch on the front of the coaster toggles which direction the power is applied.
Unfortunately, the cooling function has two separate flaws. The first being a small fan. This fan blows air across the bottom side of the Peltier device, with the intent to blow the heat pulled from your drink away, but it's noisy enough to be a distraction most of the time.
The second being that cold doesn't rise. Which means that, if your drink starts out being warmer, you end up with a temperature gradient in your cup, with the bottom layers being colder than the top layers.
With the modicum of success I'd found using this device, and finding that its price had dropped afterwards, I'd bought a couple more. The idea being to experiment with it. For example, fixing the fan noise problem would be simple enough hardware wise, by replacing the original fan with a larger module, which is quite easy to obtain and I've already done so. Structurally, however, I'm still trying to figure out how to support the whole thing, as there's nowhere near enough empty space for a fan of this size in it, so I basically need to build a new frame to support it. Given my limited set of tools and experience, a lot of thought is required here.
But, that doesn't solve the second problem. How do you make an entire glass of water (for example) colder at the same time? Do you mount the Peltier device so it makes contact with the side of the glass instead of its base? Being spring-loaded such that it pivots back and forth as necessary to make contact with the side of the glass, no matter what angle it's on? Maybe with a flexible air duct from the base to the bottom of the heat sink already attached to the Peltier device, so the fan in the base forces a lot of air through it?
Unfortunately, that concept doesn't quite work here, as all of my glasses are round in two dimensions, such that a flat object pressed against them would make contact at a single point, not even a line. Thus, heat transfer would be highly inefficient.
You can see my dilemma, and why I haven't tried doing anything else with this concept just yet. Granted, with how many of these I have right now, I could probably make one that just has a larger fan and contacts the bottom of the glass, then keep fiddling with another to see if I could make it any more efficient.
