Why don't smartphones need cooling fans even though they are as powerful as PCs?

However, despite all that power, have users ever noticed that their smartphones lack a cooling fan?

Computer cooling fans cannot be found on smartphones for some reason.

Fragile

Smartphone manufacturers have been trying for years to make their devices as thin as possible and these handsets wouldn't just be a few millimeters thick if you factor in the fan, but the fan is also bulky and requires space to move around.

The fan also breaks down pretty quickly due to actions like moving around with the phone, dropping it on the floor, etc. Everything inside the phone still works, but the fan will start to rattle or work poorly, causing everything to gradually overheat and break down.

Need open space

Devices that rely on fans for cooling are often not suitable for cramped spaces and can be uncomfortable when operating at high intensity. Smartphones are always on and the cooling fan must always be running. When placed in a pocket or bag, fan cooling becomes difficult due to the limited space. Imagine with a laptop, even using it under a blanket in bed is uncomfortable.

Mobile chips use less power, generate less heat

A key term that determines how power-efficient a CPU is is its thermal design power (TDP), which is usually listed in watts and represents the maximum power the CPU can produce under full load. The Snapdragon 8 Gen 3 is the current flagship chip for high-end smartphones with a TDP of 12.5W, which is higher than the 5W of earlier Snapdragon chips but comparable to lower-power Intel CPUs.

Snapdragon 8 Gen 3 is powerful but only has 12.5W TDP

The NVIDIA GeForce RTX 4090 has a TDP of 450w, and that’s just for a PC component. That kind of power usage is unfeasible for a battery-powered mobile device, and it also generates more heat. That’s part of the reason why PCs and laptops need fans, while phones don’t. It also explains why smartphones, no matter how advanced they get, can’t match the graphics of a dedicated gaming PC.

Mobile apps generate less heat, reducing cooling needs

Apps don’t take up physical space, but they do drain system power. If a bad app keeps making network requests, processes are running in the background while in sleep mode, and the device uses more power. Not all mobile apps are perfect, but they generally have a low impact on battery life, reducing the need for active cooling.

Smartphones using passive cooling systems

Fans use active cooling, unlike smartphones that rely on passive cooling. This is a process of heat transfer based on the difference in temperature between materials without any mechanical help. In simpler terms, things can cool down without moving anything. Phones often use metal plates between their electrical components and their external design to dissipate heat.

Passive cooling mechanism has limitations in heat dissipation under heavy load

Passive cooling works great for everyday use, but unlike active cooling, it can’t reduce the temperature to cool down quickly. That’s why some smartphones get particularly cranky during heavy tasks like gaming, when the CPU is generating more heat and the smartphone isn’t able to compensate. This is when thermal throttling kicks in, reducing performance to give the components time to cool down.

Several alternatives are under development.

Some smartphones today have special cooling modes to deal with heavy loads, especially gaming products, such as vapor chamber cooling on the Galaxy S23 series, or water carbon cooling on the Galaxy Note 9, Xiaomi's Loop LiquidCool technology, or the AeroActive Cooler 6 accessory for Asus' ROG Phone 6.

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