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The copper tube in your laptop moves heat by boiling water in a vacuum
💡 A heat pipe moves heat by boiling and re-condensing a fluid in a sealed low-pressure tube, using capillary wicking — not gravity or pumps — to cycle the liquid back.
Look inside a gaming laptop or a modern phone and you'll find a flattened copper tube snaking away from the processor. It's a heat pipe, and despite having no pump, fan, or moving parts, it can shuttle heat tens of times more effectively than a solid copper bar of the same size. The trick is that it doesn't rely on metal slowly conducting heat — it uses a phase change.
Inside the sealed tube is a tiny amount of working fluid (often just purified water) and almost no air — it's held at low pressure, which drops water's boiling point to around body temperature. At the hot end (the evaporator, touching the chip), the fluid flashes into vapor, soaking up a large amount of energy as latent heat. That vapor rushes to the cool end (the condenser, usually under a fan or fin stack), where it releases the heat and condenses back into liquid.
The genius is the return trip: a porous wick lining the inner wall pulls the condensed liquid back to the hot end by capillary action — the same effect that draws water up a paper towel. That means a heat pipe works even lying flat, or with the hot end above the cold end, no gravity or pump required. The loop runs continuously and silently as long as heat keeps arriving.