Whether the liquid cooling of phone is reliable?
By Steve Lowry 2018-11-16 4045 0
Is liquid cooling reliable?
Three forms of heat transfer: heat conduction, thermal convection, and thermal radiation.
For mobile phones and other electronics, low temperatures determine their limited heat emissions, negligible. So there are only two ways to quickly emit heat from cpu-heat conduction and heat convection.
In the traditional heat dissipation mode of mobile phone, metal radiator (later replaced by graphite) is responsible for heat conduction, dispersing the heat of cpu, silicon grease or other phase change heat conduction material is to eliminate the distance between heat source (CPU) and heat sink and accelerate heat conduction. The final heat dissipation depends on radiators, mobile phone shells and the surrounding air for heat convection.
In general, the heat convection efficiency of fluid (gas or liquid) is higher than that of solid, which is the most fundamental reason of liquid cooling: heat transfer is replaced by heat convection of coolant, which accelerates the heat exchange process. If you want to increase efficiency, you can also force convection through pressurization, such as water-cooled pumps on computers. But obviously, it's hard to get forced convection in the limited space of a mobile phone, so it's only the natural convection of the fluid in the heat pipe that you can see now.
The liquid in the heat pipe is heated at the end of the heat source, and even occurs phase change (gasification). The heat convection is formed in the heat pipe, and then cooled at the end of the heat sink, and the heat source flows back and forth, so that the heat transfer can be accelerated.
At the same time, the specific heat capacity of the liquid is generally higher, that is to say, after absorbing the same heat, the temperature rise is relatively small and the process of temperature rising is relatively slow. So liquid cooling can also play a role in lowering the maximum temperature and slowing the temperature rise.
However, the fact is that:
● It is true that heat pipes can speed up heat transfer, but the extent of acceleration depends on the velocity of convection, which, apart from the liquid itself, is closely related to the cross section of the heat pipe in a mobile phone that cannot be loaded into a pump. So a slightly normal heat pipe is a circular tube, but grafted into the phone, can only knock flat. After the cross section area shrinks greatly after flat heat pipe, convection effect is difficult to say!
● Liquid cooling can lower the maximum temperature, and it is true to slow the temperature rise, depending on the specific heat capacity and the total amount of the liquid itself. Water has the highest specific heat capacity, but considering the safety in mobile phone heat pipe will not be used. It can only be insulated mineral oil or other similar liquids (some cell phone heat pipes do not even have liquid, but use evaporation), their specific heat capacity is smaller than water. In addition, the cell phone heat pipe capacity is limited, the internal poor little coolant or evaporates are difficult to achieve the desired temperature control effect.
● Heat pipe just let the heat from the phone transferred to the CPU of graphite piece a bit faster. For no active cooling channels for mobile phone, the final cooling effect, still relies on heat sink and the heat convection between the air. If you don't want your phone to overheat, fanning a fan is definitely more useful than a heating tube.
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