Server delta-T is a powerful indicator of your facility’s cooling performance, and yet it is rarely monitored. This article explores how measuring the server delta-T can:

• Evaluate cooling effectiveness

• Calculate how much cooling is required for the actual IT Load

• Calculate how much cold air is being wasted and why

What is server ΔT?

Server delta-t is the temperature difference between the intake air going into the server and the exhaust air leaving the server. As cold air flows through the server, it will pick up the heat produced by IT equipment, causing the exiting exhaust air to become hotter.

There is a fixed relationship between the airflow (CFM), the server delta-T (ΔT), and the IT load (W), where:

ΔT = (3.10 X CFM) / W

CFM = (3.10 X W) / ΔT

W = CFM X ΔT/ 3.10

*Note that 3.10 = a constant coefficient at sea level

If you know two of the three parameters CFM, delta-T and/or W - you can start to manage your cooling performance.

How to Calculate Your Required CFM

First, you can use server delta-T and the kW load to determine how much cold air (CFM) you need to cool your server.

For mathematical simplicity, let’s imagine two servers each with a 10 kW load.

The first server with a 10°F ΔT requires 3100 CFM whereas the second server with the 20°F ΔT requires 1500 CFM.

The higher the server ΔT, the less CFM you need to cool your server(s).

This is a powerful tool for managing your cooling performance. In many cases, the load and configuration has changed from the Day 1 design. By measuring your server delta-T and your kW load, you can calculate how much CFM is actually required today, and how much is being over or undersupplied.

With Purkay Labs’ software, you can easily perform a CFM analysis.

How to Evaluate Your Cooling Performance

Another way to use your server delta-T to manage airflow is by comparing the server ΔT to the air moving through the CRAC units, the CRAC ΔT.

Ideally, the CRAC ΔT and the server/cabinet ΔT should be the same. But this is rarely the case, and indicates that there air that is not reaching the server intake (bypass airflow), or some exhaust air might be returning to the server intake (recirculation airflow).

Ideal Cooling Pattern

Cooling Waste

By measuring the server delta-T and the CRAC delta-T, you can evaluate your air management and determine what is causing hot spots or other airflow issues.

With Purkay Labs’ software, you can quickly visualize your cold air performance and effectiveness.

Conclusion:

Server delta-T is a powerful tool for the busy Data Center Operator.

If you want to learn more about server delta-T, please email info@purkaylabs.com or set up a meeting with us directly.