[nextpage title=”Introduction”]

Which is the best position to install a tower CPU cooler: with the fan facing the front of the case, or rotated in 90 degrees, with the fan facing the video card? Let’s find out!

It is common sense that a CPU cooler with tower heatsink must be installed with its fan pulling air from the front of the case, blowing in direction of the rear of the case. Most CPU cooler manuals instruct to install it this way.

But what if you install the heatsink with its fan facing the video, blowing air to the top of the case?

In older computer cases, there were two reasons to direct the air to the rear panel. Usually, on those cases, the power supply was at the top, and there was no opening at the upper panel. So, the only way out for the hot air was the rear panel (or through the power supply). Nowadays, most good cases have the power supply positioned at the bottom, and the top panel is meshed. That is why we are questioning the standard “blowing to the rear” position.

There is also the heatpipe issue. Some people believe that in tower coolers, the heatsink must be in vertical position, so gravity can help the fluid inside the heatpipes return to the base of the cooler, improving the cooling performance of the cooler.

In order to test those theories, we installed a typical tower cooler (SilverStone AR01) in our testbed system, in both positions, and tested the cooling performance. See Figures 1 and 2.

Figure 1: Traditional position (fan facing memory modules)

Figure 2: Fan facing the video card 

We repeated both tests with our mid-tower case at its normal position (with the motherboard in vertical position) and also with the case laid down at its right side, with the motherboard at horizontal position.

Let’s check our testing methodology on the next page.

[nextpage title=”How We Tested”]

We ran the tests on a Core i5-2500K CPU (quad-core, 3.3 GHz), which is a socket LGA1155 processor with a 95 W TDP (Thermal Design Power). In order to get higher thermal dissipation, we overclocked it to 4.0 GHz (100 MHz base clock and x40 multiplier), with default core voltage (Vcore).

We used the SilverStone AR01 cooler, which has the typical design for tower coolers.

We measured temperature with the CPU under full load. In order to get 100% CPU usage in all cores, we ran Prime 95 25.11 with the “In-place Large FFTs” option. (In this version, the software uses all available threads.)

Room temperature measurements were taken with a digital thermometer. The core temperature was read with the SpeedFan program (available from the CPU thermal sensors), using an arithmetic average of the core temperature readings.

During the tests, the panels of the computer case were closed. The front case fan was spinning at minimum speed in order to simulate the “normal” cooler used on a well-ventilated case. We assume that is the common setup used by a cooling enthusiast or overclocker.

After the first test session, we remounted the cooler in both positions and tested again, and tested again to ensure there were no mounting issues. The results were the same as the first time.

Hardware Configuration

• Processor: Core i5-2500K
• Cooler: SilverStone AR01
• Motherboard: ASUS Maximus IV Extreme-Z
• Memory: 8 GB (2x4GB) G.Skill Ripjaws Z (DDR3-2133/PC3-17000), configured at 1,600 MHz, in dual channel
• Hard disk: Seagate Barracuda 7200.12 500 GB
• Video card: Zogis GeForce GTX650Ti 1 GB
• Video resolution: 1920×1080
• Video monitor: Philips 236VL
• Power supply: Seventeam ST-550P-AM
• Case: Cooler Master HAF 922

Operating System Configuration

• Windows 7 Home Premium 64 bit SP1

Software Used

• Prime95
• SpeedFan

Error Margin

We adopted a 2°C error margin, meaning temperature differences below 2°C are considered irrelevant.

[nextpage title=”Our Tests”]

The data acquired in our tests is shown in the table below.

The graph below shows the difference of the core temperature minus the room temperature for each test.

[nextpage title=”Conclusions”]

The acquired data show two clear conclusions. First, that the conventional position for the heatsink, with the fan facing the front of the case, blowing air from the front panel to the rear panel, offers worst cooling performance than the position with the cooler rotated in 90 degrees, with the fan pulling air from the bottom to the top of the case. It is probably due to the fact the hot air has the tendency to go up, and it is easier for the cooler to work according to the natural airflow.

The second conclusion is that there is no advantage in letting the heatpipes to point up. The CPU temperature was actually a little higher when the computer was laid down. The reason for this seems to be also that the case was designed to have an optimized airflow when in its original position.

In summary, at least in our system, the best way to install a tower cooler is with the fan facing down, and the computer case in the vertical position.