Random #HVAC thing I love that I think about whenever I'm doing #chiller plants is the unit "Ton" of cooling. Derived from the amount of #BTUs to melt a 1 ton block of ice in 24 hours. Basically 12000 BTUs/Hr or 288000 total BTUs. That's how they used to cool large buildings! Big blocks of ice in the air stream, delivered by truck.

And, of course, everything old is new again; so new versions of this are in use in places today with local ice-making equipment!