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Home Built Mini-Fridge

One day whilst admiring one of my friend’s cheap mini-fridges, I began to think about how I could improve on the design. After all, his fridge barely functioned. After taking apart a similar fridge to see how it worked, I found only a basic metal heatsink and fan. Whilst this does provide cooling, I’ve found it incredibly slow at cooling a volume like a fridge compartment.

So, I decided I could do better.

My first rough designs in the CAD software Google SketchUp were figuring out the compartment itself. How large is the average beer bottle? Would it open from the front? Would it open like a chest? How would the heatsink and fans be placed? Answering these questions gave me some of the following ideas:

Initial Compartment Ideas

While my first idea was to use a heatsink with more surface area and a fan that pushes more air, my research quickly introduced myself to the Peltier. This piece of equipment, named after the discoverer of the effect that makes it so useful Jean Peltier, can convert electricity to cooling. This plate, when a current is passed through it, will cool one side and heat the other. Here’s the interesting part though: The cooler you can keep the side that heats up, the cooler the cool side will be. And without too much effort, it can get really cold!

Below are some photographs I took after my initial tests of a peltier unit that I purchased. It’s running via a modified computer PSU (I rewired it to output 12v without a PC attached to it, very useful) and the hot side is held pressed up against a standard computer heatsink and fan by two black weights. As you can see, after not too long ice has formed on the plate. I’d call this experiment a success!

TEC Test

I did further research into the Peltier units to discover the best voltage, current and temperatures to achieve the most efficient cooling. The tech specs for these units were very helpful.

TEC Specifications

The Peltiers would be placed between the heatsink and the fridge compartment itself, and then fans mounted to draw heat away from the heatsink. I went through a number of iterations for the best layout of peltiers and fans. Should I use six 120mm fans or two 220mm fans? The considerations included things such as cost, airflow, and of course noise. Fans make noise, and more fans means more noise. I eventually settled with using two 220mm fans:

Cooling Plate Iterations

As shown at the top of this entry, I then modelled the entirety of the fridge in great detail. This includes main compartment, insulation, placement of thermostat and power suppplies, the design of the wooden enclosure with a mesh back for easy maintenance/cleaning access, the top chest-doors, etc.

All that remains is for me to complete construction. As of right now, I am putting money aside to complete the project. This fridge is certainly not as cheap as my friend’s terrible fridge, but it’s going to be a lot better. And the coolest thing? I’m going to think about all the fun I had designing and building it every time I look at it!

Project Details

  • Designed From Scratch
  • Thermostat Controlled
  • 27.7 Litre Capacity
  • Cooled via Thermoelectric Effect
Lunch Project

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