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[nextpage title=”Introduction”]

Nowadays, most cases have several places where you can put a fan. Supposing that you want to install only one fan on your computer, where is the best place to do it? Let’s run some tests and find out.

It is a well-known fact that the fans installed in the lower half of the case must be installed as intake, while the fans installed in the upper half of the case must be installed as exhaust, blowing air to the outside of the case. Because of the physics law which states that hot air rises, it makes no sense to force the hot air to flow downward.

In order to answer this question, we ran some tests, measuring the temperature difference between the CPU core and room temperature with the case fan at different locations: at the rear panel, at the top panel, at the front panel, and at the side panel. We also repeated the test with no case fan at all, with the case’s left panel closed and open. We will present the test methodology and results in the following pages.

[nextpage title=”How We Tested”]

We tested different positions for the case fan using a Core i5-2500K, which is a quad-core CPU with a 3.3 GHz clock and a TDP of 95 W. This CPU was overclocked to 4.5 GHz (increasing the multiplier to x45), with a core voltage (Vcore) of 1.1 V.

In order to get 100% CPU usage in all threads, we ran Prime 95 25.11 with the "In-place Large FFTs" option. (In this version, the software uses all available threads.)

We used a Thermalright True Spirit 120 CPU cooler, with the thermal compound that comes with this cooler. Click here to read our review for this cooler.

We used the Cooler Master Elite 430 case, which has the power supply at the bottom, and has the possibility to install case fans at the rear, top, front, side, and bottom panels. We didn’t test the fan at the bottom panel because our power supply was too deep and wouldn’t allow this installation. We removed the stock fan from the case before testing.

The fan used in our tests was the SilverStone FM123. We chose this fan because it is very strong, always spinning at 2,700 rpm.

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.

Hardware Configuration

Operating System Configuration

  • Windows 7 Home Premium 64-bit SP1
  • NTFS Filesystem

Software Used

Error Margin

Since both room temperature and core temperature readings have 1°C resolution, we adopted a 2°C error margin, meaning temperature differences below 2°C are considered irrelevant.

[nextpage title=”Our Tests”]

We tested the effect of the case fan on the CPU core temperature in different configurations. First we tested with no case fan and the left panel open. Then we tested with no fan and the case closed.

The following tests were done with the case fan at the rear, top, front, and side panels, as shown in Figures 1, 2, 3, and 4. The case was closed for those tests.

Which is the best place to install a case fan?Figure 1: Fan at the rear panel

Which is the best place to install a case fan?Figure 2: Fan at the top panel

Which is the best place to install a case fan?Figure 3: Fan at the front panel

Which is the best place to install a case fan?Figure 4: Fan at the side panel

The following table shows our results.

Test Room Temp. Core Temp. Difference
Open case 24 58 34
No fan 24 63 39
Rear fan 24 58 34
Top fan 23 57 34
Front fan 23 58 35
Side fan 24 61 37

The graph below shows the temperature difference between the CPU core temperature and the room temperature in each test.

Which is the best place to install a case fan?

[nextpage title=”Conclusions”]

The first conclusion we can make corroborates what we found in our article, “How the Case Rear Fan Improves CPU Cooling.” Keeping the left panel of the case open can reduce
the CPU temperature in the same measure as having a well-ventilated, closed case.

Answering the question in the title of the article, we can say that the best places to install a case fan are the rear and the top panel, at least for the CPU temperature. (A fan on the left panel is said to lower the temperature of the video card, but we will still need to make some tests to check whether this claim is true or not.) It is curious that in both places the fan acts as exhaust, which means that, in our system, it was better to work with negative air pressure rather than positive air pressure, i.e. more forced air exiting the case than entering it.

Finally, remember that the results we achieve apply only for the kind of system we used, with a well-ventilated mid-tower case with the power supply installed at the bottom of the case. Different systems (with horizontal coolers, for example) may behave differently.