How to cool in the desert: the fluid dynamics of water evaporation from our clothing in hot and dry conditions

About one-third of us live in "drylands" and could have an easier time coping with the more frequent and intensive heat waves by evaporating water from our clothing. In such dry and hot conditions, the near human body fluid dynamics that drive water evaporation are intricate. In particular, air temperature and humidity have a competing effect on air buoyancy and can cause flow stagnation and reversal. In addition, radiative heat from the environment also strongly influences the evaporation process. To understand the intricacies of personal evaporative cooling, I developed a comprehensive model that couples conductive, convective, evaporative, and radiative heat transfer with mass transport in natural or forced laminar flow. Using this model, I will show that the vast majority of water evaporated from our clothing is wasted due to solar radiation and excessive convective losses. I will also show that these issues can be resolved through systematic flow model-driven design of collapsible sun and wind "shade" layer [1].