Thermal mass is a tricky thing.

A colleague (and sometime reader of this page) recommended to me quite some time ago that I put lots of water or some such thing in my refrigerator. The idea being that the water has a high thermal mass and would remain cold, taking up space that would be air that left the fridge when I opened the door. From there, it's an easy logical step to imagine that there is less warm air entering the space, needing to be chilled.

Maybe I over-think these things, but if I put big gallon jugs of water in the fridge, doesn't it have to chill them, defeating the purpose? Water has a very high specific heat (a measure of the energy needed to change the temperature of a given mass of a thing), meaning a large thermal mass, and that cuts both ways. If I put water in the icebox to increase the thermal mass, there is an initial energy cost to cool the water that's much higher for water than for air (relatively low specific heat), but if I don't, I pay over time to continuously chill additional air that goes into the refrigerator every time I open the door, right?

And here I sit, still trying to figure that one out.

CDs listened to today:

• Celso Garrido-Lecca: String Quartet No. 2
• Jellyfish: Bellybutton
• My Morning Jacket: Z