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[SOLVED] Liquid Cooling of MOSFET's

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Janani_Baskaran

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Can anyone tell me about Liquid Cooling and its use in Cooling down the Switching MOSFET's.

Is the approach necessary or are there any alternates for the same?
 

Hi,

not necessary, as long as you can ensure low enough junction temperature as given in the datasheet.

Altenative: air cooling

Klaus
 

Its a messy business, pumps, hoses, heat exchangers, and if you spring a leak it can damage a lot of components.
Its only really useful if you are forced to use water cooling for other things, such as in an induction heating furnace.

Anything else, forget water cooling, just use conventional aluminium heatsinks and forced air cooling if necessary.
 

Hi,

I agree, there are only a couple applications where water cooling is essential.

Once we built a circuit used in cleanroom for semiconductor production. About every equippment is cooled with water there. Air heatsinks or fans ar not allowed, because they spread dirt in the air causing the semiconductor yield to drop.

Klaus
 
Agreed, water cooling should only be considered in two situations:
1. Total lack of available airflow near the FETs. Clean rooms are a good example.
2. Water cooling is already available in the design. One example is drivers for water pumps, where the pumped water can be routed along the enclosure (assuming the water is cool).
 

An application field where you often find liquid cooling is motor inverters for electric cars. I see it also in multiple 100 kW power inverters, but it's not necessarily.
 

Generally speaking, another application where liquid cooling would be strictly necessary is in the case where the heat source is relatively distant from the region available for heat dissipation, although this is not a common constraint in designs.
 

I have seen heat pipes used where the source of heat is some distance from the heat dissipation area. Its not strictly liquid cooling, although in a strange way it is related.

One rather obscure use of liquid cooling is in some military fighter jets, where the massive fuel flow to the engine is first routed through some high power density electronics for cooling purposes.
 

Speaking of heat pipes, there is one in my laptop (Dell Inspiron 1525, purchased secondhand). The dealer had the cover off while refurbishing it. He pointed out the heat pipe to me, saying it was a novel feature. It did not look like it carries liquid. It looks like a length of flattened bent copper tubing. No pump, no moving parts. The heat pipe carries away heat several inches, to the vent slots where a fan circulates air.
 

BradtheRad said:
saying it was a novel feature. It did not look like it carries liquid. It looks like a length of flattened bent copper tubing. No pump, no moving parts. The heat pipe carries away heat several inches, to the vent slots where a fan circulates air.
Click to expand...

Heat pipes has been there for about 50 years (just recalling from memory)- it has been there before the laptops.

It is a hollow tube and does contain a liquid. Heat causes liquid to evaporate and near the heat sink (yes, one end ends with a heatsink) the vapour condenses back to the liquid that goes back to the other end. No pumps are required: the liquid moves by a capillary action.

Using a heat pipe for a laptop CPU is certainly an overkill. But the novel feature can get extra bucks...
 
I don't think convection based heat pipes are that novel in the laptop and sever world where space is quite constrained (and often in one dimension like rack mounted 1U servers).

They're certainly to be avoided if possible though.

Not helpful for fets but a colleague told stories of using regular old copper pipes as high current conductors (was it for a large transformer? I forget) with liquid pumped through them for cooling.
 
asdf44 said:
... regular old copper pipes as high current conductors (was it for a large transformer? I forget) with liquid pumped through them for cooling.
Click to expand...

They are routinely used for large electromagnets- both in lab and in industry. Deionised chilled water is circulated with a pump. The currents can be in excess of 100A (often 500A) but they are slowly getting replaced by superconducting magnets.
 

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