# Peltier cold temperature does not transfer when a heat sink is attached

I am trying to build a peltier cooler.

It works. Cold side temperature is about 10C on cold plate of peltier. I want to blow this cool air out.

But the cold temperature goes up as soon as the heatsink plate or plane plate. It seems that the cold temperature is not transfer thru the heatsink or the plane plate.

I want to hear any recommendations for improving transferring cold temperature!

• Put the heatsink on the hot side. – vofa Jan 18 '18 at 1:49
• cold temperature is not transfer thru the heatsink ... cold does not flow from cold side to the heatsink ... heat moves from the cold side to the hot side .... the heatsink on the cold side moves more heat from surrounding air to the cold side ... you need to enclose the cold side in a box and it will move heat from inside the box to the hot side – jsotola Jan 18 '18 at 5:58

You need to understand the relationship between heat flow and temperature.

A system's equilibrium temperature is whatever value that occurs when the heat flowing in matches the heat flowing out, keeping in mind that both flow rates are in some way dependent on that temperature.

The "bare" Peltier can reach 10°C because heat is transferring to it slowly relative to how fast the active circuit can transfer it away (to the hot side). When you add the heatsink, heat can flow into the cold side from the heatsink itself — as well as from the ambient air as the heatsink cools down — much faster. This raises the equilibrium temperature.

In other words, this is just a fact of physics. If you want to have a higher heat flow at a given temperature, you need a bigger Peltier device (or more of them).