HumCooler: The Stack

The stack is the unique heart of the HumCooler, not like anything you'd see anywhere else, and most people have no experience building something like this. No worries, it's simple, and dimensions are not critical.

The stack should be made of a material that conducts as little heat as possible. This may seem surprising, but it's because the gas does the work of moving heat along the stack -- any leakage of heat through the stack material is wasted energy. Stainless steel is a common choice (although it's metal, it's not a very good conductor of heat), and stacks have also been made of ceramic, plastic, and even paper. Keep in mind that the material must be able to stand the heat of the hot end without burning.

The original device was called a "stack" because it was made of a stack of fiberglass wafers. Theoretically, a stack of parallel plates is better than a honeycomb (or similar array of holes) because it minimizes viscous loss. In practice, honeycomb is much easier to obtain. [LIST COMMERCIAL VENDORS HERE]