Sciencemadness Discussion Board

build your own refrigerator

xxxxx - 12-5-2008 at 15:01

typically a refrigerator can weigh several hundred pounds. i was interested in constructing a refrigerator using peltier coolers with 6 inch thick styrofoam insulation with 3/32 inch aluminum sheeting inside and outside measuring 3 feet deep by 4 feet wide and 5 feet tall giving about 20 cubic feet storage and weighing about 80 pounds. would this be practical and why or why not.

bio2 - 12-5-2008 at 16:53

Peltiers are super inefficient but if this is no concern your
idea sounds feasible.

8-10 picnic cooler sized modules should do it. Do they make these
for Line voltage or just 12V?

The 12V ones can be used at 18V or more with corresponding
output and input characteristics.

not_important - 12-5-2008 at 18:41

Calculate the R value of the insulation combination you want to use. Then calculate the heat flux, rate of heat leaking through the entire surface area of the box at the desired internal temperature for the maximum expected external temperature. Add about another 10% for door leakage and defects in the insulation.

After that you need to consider how fast you want anything pu inside to be cooled down. Treat it as an equal weight of water at ambient temperature, calculate the additional cooling capacity needed to bring it to the target temperature in the amount of time you want it to. This gets added to the basic heat flux.

Once you know that you can determine what the requirements are for a TEC that can keep the inside as cold as you want it to be. Several manufactures of TEC (Peltier coolers) have tools to assist in designing or selecting a TEC to meet those needs.

As already said, a TEC is not very efficient. Expect to use fans to get rid of waste heat, the hotter the heat radiators the worse the TEC will do at cooling.

Shiny foil is better than sheet Al, consider sandwiching foil between styrofoam. Check into prefab insulation.

Once you've done that, you've designed a modern refrigerator except using TEC instead of the conventional compressor-evaporator.