Dr. Jack Demystifies Delta-T

For International data center day on March 26, 2025 Purkay Labs Principal Consultant wrote up a fun poem for Data Center operators. Back by popular demand, is the second Dr. Jack.

Dr. Jack Demystifies Delta-T

by Gregg Haley

Do you have some time?

Then come and sit with me.

We’ll have a little talk,

All about Delta-T

Delta-T wears many hats,

Supply, Return, Server and CRAC,

Some like it High, Some like it Low

It is up to you to really Know.

Supply side is generally easy,

Making the plenum cool and breezy,

Bringing air into the cold aisle, 

A result that makes everyone smile.

If the Supply Delta-T is Low,

You should be good to go.

If the Supply Delta-T is High,

That's not good, please find out why.

Return air is Supply’s partner,

The Servers should make the air hotter,

Bringing the air back to the CRAC, 

Keeping the air cycle on its track.

If Delta-T is low,

Again you’re good to Go,

If Delta-T is high,

Air mixing is usually why.

The Server Delta-T,

 where the rubber meets the road,

Cool air in, hot air out, 

should be the standard mode,

If Delta-T is low, is the Server fan racing?

The CFM to heat load should determine the fans pacing.

If there is a higher Delta-T,

proper heat extraction it must be.

Last but not least we look at the CRACs,

The key to cooling all Servers in Racks.

Taking Hot air in and making it cool,

Controlling the airflow like nobody’s fool.

A high Delta-T,

And it’s a big hit.

A low Delta-T,

And it's a big miss.

Bad Delta-Ts are costing you money,

and money out the window is never funny.

So place your sensors,and watch the readings

They will pay you back with savings you’ll be reaping.

Dr. Jack will visit your center,

Even if you are just the renter,

Contact Purkay Labs, and talk to our crew,

We’ll get you the data, so you’ll be running like new.