Thread: Temperature of a box containing heated water

I'm looking for a way to maintain a constant temperature of 110°F in a medium-sized camping cooler. The temperature needs to be fairly constant for as long as 30 days, so the heat source needs to be efficient and not prone to burning out. Putting a light bulb in the cooler does work, but it's not very cost effective because bulbs burn out, and also are not especially efficient heat generators.

If I put a gallon jar of water in the cooler, and heat the water with a fish tank heater to 95°F, how warm will the air in the cooler get? Fish tank heaters will not go beyond 95°F, since I guess there are no fish wanting warmer water than that. The lid is not airtight (there is just enough gap at the handle for an electric cord to pass), but airflow from the cooler is minimal. Where would I find formulas that model this kind of thing? Thanks for your help.


Byron

It wouldn't get any hotter than the setting of your thermostat. You will have to replace the thermostat with one with a higher setting, maybe from a yogurt maker, an egg incubator, or an electric water heater.

The relevant formula would be Newton's law of cooling.
Lumped capacitance model - Wikipedia, the free encyclopedia

... and also are not especially efficient heat generators.

Actually incendecient bulbs have quite high heat efficiency, probably 90% or better.

I'd make sure you had excess heating capacity and use snap thermostat switches (~$5-10) to regulate the heat--they come in a variety of temperature ranges.