In a world constrained by economics, resources, and above all thermodynamics, an optimal system consumes few resources in both its production and operation. Thermodynamics is often a cruel player in this minimization game, since in fields such as electricity production and building heating and cooling systems, the most thermodynamically efficient procedures have historically been among the least economical. In fact, while the governing trend due to global concerns over carbon emissions and rising fuel prices has seen a shift towards thermodynamic efficiency in operating procedures, there often remains a disconnect between economic profitability and thermodynamic efficiencies.
CHAOS Lab is currently investigating the materials and modeling of a porous hydrophobic evaporative cooling system which inherently consumes little energy in its operation taking advantage of wet-bulb depression psychometrics.
Water remains in contact with the building structural element (pictured below as cinderblocks from x = 0 to xI). At x = xW the water is additionally in contact with a hydrophobic membrane with pores on the order of 1 micron which allows water vapor to pass yet restricts liquid water. Energy removed through the spontaneous evaporation of water induces sensible heat transfer with the building interior, in turn cooling the building. The external facade element (pictured as brick at x = xM) will ideally be porous enough as to not impede evaporation.
Initial results demonstrate that the system can supply the cooling demand for indoor areas with large external walls, such as auditoriums and lecture halls.
To accurately account latent, sensible, and evaporative fluxes and associated mass and heat transfers, steady-state analysis of the membrane cooling system was performed. In conjunction with other models developed at Princeton University, CHAOS has produced a quasi-steady-state model predicting evaporative membrane performance.