# Introduction

Thermoelectric (peltier) devices offer a compact and reliable, albeit somewhat inefficient, source of cooling/heating for the lab.

# Work Log

## 15 Jun 2020

I rebuilt the system using just a single layer of TECs and it works much better. I also insulated the cold reservoir with foam.

I’m happy with the results, so I am archiving this project.

120W TEC chillers are available for about $40. I imagine that they pump significantly less than 120W, however. I ordered 9 TEC1-12170s, two 120mm liquid cooler blocks, and one 240mm radiatior. I should have bought two radiators, but the eBay seller only had one available. Formulas for calculating pumping characteristics of cascaded TECs. ## 08 Aug 2019 It would take approximately 750W to boil 1L of water per hour. MAX1978 is a single chip driver for peltier units. If precise temperature control is needed, this is where to start. For my purposes,$24 to power 30W is just too expensive. A lot of good info from Maxim Integrated.

A full H-bridge with PWM control seems like an efficient option.

## 07 Aug 2019

Today my old chiller decided to quit. This is the second time it has done so. I was distilling some acetone at the time. I quickly rigged up a ice water bath chiller and disconnected the hoses from the old one. Several hours of smooth distillation went by without a problem. I went outside to walk the dog. During that unattended ten minutes or so, the old chiller decided to start up again (I had forgotten to unplug it) and spill all of its cooling fluid over my bench and floor.

So…. ya. I’m going to build a better, more reliable system. I’m starting with TECs because of the compact size.

From here it looks like 200-400 watts is common for bench top models.

Cooling capacity of radiators is about ~100W per 120mm section. These radiators are extremely cheap. Two should be sufficient (400W capacity).

A standard server power supply with PWM can be used to set the perfect voltage for each TEC. Alternatively, you can take a small hit on performance and just go with straight 12v each.

For the TEC1-12107:

$$T_{hot} = 25^{\circ}C, V = 12.0v; T_{cold} = 0^{\circ}C$$

$$\Rightarrow Q_{i} = 96W$$ $$\Rightarrow Q_{c} = 50W$$ $$\Rightarrow COP = 0.52$$

$$T_{hot} = 25^{\circ}C, V = 6.0v; T_{cold} = 0^{\circ}C$$

$$\Rightarrow Q_{i} = 24W$$ $$\Rightarrow Q_{c} = 15W$$ $$\Rightarrow COP = 0.63$$

# Bibliography

Thorén, Jonas, and Anton Widell. 2011. “Development of Liquid Cooling for PCs.” PhD thesis. https://odr.chalmers.se/handle/20.500.12380/153096.