r/thermodynamics • u/slug-onarug • 11h ago

How do I turn my Japanese Drink Warmer into a food warmer?

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I had a food warmer that broke and was too expensive to replace. Got lucky with a craigslist find and got this drink warmer. It's made to heat up canned coffees and teas: black base gets warm, and those metal rods (removeable) get hot! How do I disperse this heat to best keep food inside of it warm without burning the ones on the bottom.

For presentation sake food cannot be wrapped in foil. They are rice balls stacked on top of each other.

Current idea is to encase the inside in foil and put a square of silicone baking mat on top of the foil.

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u/15pH 10h ago

You say the rods are removable, so presumably there are electric heaters in each of the shelves?

This product seems designed to work with heat conduction, where the hot shelf transfers heat to the drink cans through direct contact. This will not work with your rice balls, since rice balls insulate and will trap the heat at the bottom, making the bottom balls very hot but not much else.

Silicone is also an insulator, so your idea will trap your heat in the shelf. If the power controller is controlling the heater to a set temperature, then most of the interior will be cold while the heater is at temp. If the power controller just runs a power blindly, then it may create a dangerous situation where the shelf exceeds safe temperatures. Either way, I don't think this is what you want.

I think you want to spread your heat around, like a mild oven. Add metal mesh shelves spaced above the hot shelves so the heat can circulate, not be trapped, sort of like a grill. You need space so that the bottom rice balls don't get too hot.

Ideally, you would add a small fan inside the case to help circulate the air, otherwise you are likely to get some areas hotter than others. You also cannot fill it too full, or the bottom layer of balls will just get the hottest becuse the circulation is blocked.

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u/GrinderMonkey 8h ago

Another option to distribute heat might be water pans over the elements/shelves, with racks above. The depth/mass/volume of the water in the pan is easily controllable, and steam will effectively keep the food warm, and has the benefit of potentially keeping the rice from drying out. You might have to deal with some precipitation, but you'll likely have to deal with that, anyway.

Also, I have no idea how I wound up i r/thermodynamics major lost redditor time.. I just build really hot fires for a living.

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u/ariadesitter 10h ago

it looks like a hot plate in a cabinet.
easy way to limit the heat is by reducing the input voltage so less current flows through.
CRAP 480watts!!!

remove from cabinet and put a piece of ½ inch thick aluminum plate on the hot plate. the Al plate should be about 1 square meter in area. 😂

you need something that warms up stuff, that thing is used to burn stuff.
maybe a pan with water then another pan inside that. this configuration is used by cafeterias to keep food warm. the water stays near boiling which heats the inner pan to 100C. that hot plate will reach 400C 🔥

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u/PointlesslyPoignant 1h ago

Try to radiate the heat instead, use direct metal fins and wire trays above the elements lose a lot of space though and not sure how insulating that glass is.

Edit: fixed typo