Thermosiphon
A thermosiphon (or thermosyphon) is a device that employs a method of passive heat exchange based on natural convection, which circulates a fluid without the necessity of a mechanical pump.
Its purpose is to simplify the transfer of liquid or gas while avoiding the cost and complexity of a conventional pump.
A good thermosiphon has very little hydraulic resistance so that liquid can flow easily under the relatively low pressure produced by natural convection.
If the piping of a thermosiphon resists flow, or excessive heat is applied, the liquid may boil.
[citation needed] When phase change occurs in a thermosiphon, it means that the system either does not have enough fluid, or it is too small to transfer all of the heat by convection alone.
[7] A study published in 2006 by oil giant ConocoPhillips reports that Alaska's permafrost, upon which much of the state's infrastructure is built, has degraded since 1982 amid record warm temperatures.
The most commonly used heat exchanger is a radiator, where fans actively blow air across an increased surface area to condense the vapour to a liquid.
Without proper cooling, a modern processor chip can rapidly reach temperatures that cause it to malfunction.
Even with a common heat sink and fan attached, typical processor operating temperatures may still reach up to 70 °C (160 °F).
The system has to be completely airtight; if not, the process of thermosiphon will not take effect and cause the water to only evaporate over a small period of time.
Some early cars, motor vehicles, and engine-powered farm and industrial equipment used thermosiphon circulation to move cooling water between their cylinder block and radiator.
More compact engines began to use smaller radiators and require more convoluted flow patterns, so the water circulation became entirely dependent on the pump and might even be reversed against its natural direction.
An engine that circulates its cooling water only by thermosiphon is susceptible to overheating during prolonged periods of idling or very slow travel since the lack of forward motion provides too little airflow past the radiator, unless one or more fans are able to move enough air by themselves.
