Air Cooling vs Water-Cooling: A Brief Introduction

Akasa
6 min readNov 2, 2022

Have you ever thought about why your laptop gets too hot when leaving it on your bed? Or why do you need such a large cooler for your high-end CPU? Overheating is the most common enemy for anyone who owns a computing device, from gaming consoles to high-end PCs, laptops to phones, and tablets to smart televisions. One of the most power-hungry and essential components in many computers is the main culprit: the all-powerful processor, which produces tons of heat.

The reason for this stems from how a processor works. Within a processor, a bunch of switches control the logic behind all the computer’s operations. A small amount of energy is needed to turn the switch on and off, which travels through tiny wires. However, these wires resist some of the energy transfer, which gives off some heat as a by-product. Due to the minuscule size of each switch and the huge abundance of them within a processor, the heat can quickly build up, especially under high loads of computing. These switches will be turning on and off more frequently and at a faster rate, so whether it is gaming, rendering or complex modelling the heat produced by the processor will increase dramatically.

To prevent the CPU from overheating and causing damage to itself, a system needs to be in place to move the heat away from the internal components. This can be done using a heat sink, which is a block of aluminium or copper that transfers heat quickly and efficiently. The resulting heat can then be transferred to another medium, which I will discuss in this article.

The three main ways in which the heatsinks can be cooled are:

  1. Passively, using a large capacity heatsink
  2. Air cooling, with a heatsink combined with computer fans
  3. Water cooling, with a radiator filled with coolant, combined with computer fans

This article will focus on the latter two methods, as passive cooling simply uses the ambient air to extract the heat from the processor.

Air cooling vs water cooling!

Both air cooling and water cooling require fans to work; the air flowing through the fan is used to move the heat from the heat sink to the ambient air. This means the fan specifications will affect the performance of a CPU cooler — especially the fan’s airflow, air pressure, and fan speed. These will also be affected by the air convection within the PC case, which can be optimised to increase the amount of air cycling through the system.

This is where the differences begin. The heat capacity of air is much lower than that of water, an important property which extends further than just computer cooling. Heat capacity refers to the amount of heat energy that can be stored within an object; imagine it as a battery storing energy, or a bank storing money! In this case, air is like a small local bank (with a smaller bank vault to store heat), whilst water is more like a national bank, with more capacity to store the heat.

This attribute is the main reason why a water-cooled CPU is preferred for some PC builds. Since the coolant inside a water cooler can hold more heat, the water will not get as hot as an air cooler (initially), meaning the cooler can efficiently remove more heat from the processor compared to an equivalent air cooler. Water coolers are therefore suitable for use on high-end processors, especially the newest yearly CPU releases where the recent trend has been an increase in power consumption and heat output.

The secondary effect of water cooling allows the fans attached to the radiators to run at a lower RPM. Combined with the much quieter water pump, fan noise is greatly reduced. This is perfect for quieter or silent systems, as some PC setups completely remove the fans from the case and only use the circulating water for cooling.

This image shows how the water cooling system works. The pump passes coolant over the CPU, picking up the heat and storing it. The coolant then moves through the rubber tubing, then to the radiator. Now that the heat is spread over a much larger surface area, case fans transfer the heat stored in the coolant to the air. The cooled coolant is then pumped back to the heat sink/pump, where the cycle can begin again.

A downside to water-cooling is the much higher need for maintenance. More moving parts can eventually lead to more things breaking, which can be an expensive fix, especially for high-end computer components. Most computers do not need this — air cooling is sufficient and low risk as replacement fans are widely available. Larger tower heat sinks come with copper heat pipes, which transfer the heat from a CPU to the fins using fluid convection within the pipes. These pipes use the physics of heated air to remove the heat efficiently and effectively, making air coolers the most popular method of cooling!

Closed loop (AIO) cooling vs open loop water cooling

The difference between all-in-one (AIO) coolers compared to open loop cooling systems can be quite drastic. AIO coolers are known as closed loop systems as the coolant and pump are all produced as one object, which cannot be modified without a lot of tinkering. Custom loop water cooling is an open loop system, where almost everything is customisable and changeable, and it is up to the user to design and build the entire cooling system.

This can be a daunting task to set up, but the high risk comes with a high reward. As custom loops can be altered, updated, and repaired, higher efficiency of heat transfer can be reached. The coolant, pump, radiator, tubing, and cooling block can all be changed to increase the cooling system’s ability. More coolant can be used compared to an AIO cooler which expands the heat capacity of the entire system, and the tubing can be moulded and bent into all different shapes. There are also GPU cooling systems available to connect with the open loop — these are rare to find in an AIO solution and are especially important for gaming and rendering purposes for which these PCs may be commonly used.

Photo by Barez Omer on Unsplash

Usually, only enthusiast PCs will be water-cooled; the CPU temps will be very low, and the fans used in conjunction can be even slower moving and quieter (or not even used). The other reason someone may want to use this method is for aesthetic reasons, the customisable options can be matched, and dyes for the coolant are available for purchase to spice up the PC build!

Bonus round: Oil?

There exists an almost forbidden technique to cool the whole computer called mineral oil cooling. A lot of preparation is necessary for this rogue method to work. The whole motherboard is cleaned and placed within a tank, which is then filled with mineral oil. Since this oil does not conduct electricity, it will not short-circuit the motherboard and the components are safe (and quite oily). Combined with a tank pump, the oil can be circulated to remove the heat from all areas of the PC, including the parts which usually would not be water cooled (i.e., VRMs, hard drive, and RAM). These setups are always head-turners, usually with an aquarium theme to complete the look.

If this risk is too much for you, Akasa’s SOHO H4 tower coolers and the SOHO 240 and 360 AIO water coolers are now available from most major online retailers. These come with premium SOHO AR fans, which have been tweaked for optimised airflow and air pressure to give the lowest noise output. In combination with the sleek aRGB ring, these fans will flaunt your system and enhance the tower coolers/water coolers inside your PC build!

Calvin On — marketing@akasa.co.uk

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