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The wind tower principle

Before the invention of air conditioners, inhabitants of the Middle East used wind towers to capture wind and cool their homes.

This is a wind tower at the Madinat Jumeirah. The wooden cross bars were draped with wet cloths so the wind would cool as it blew into the homes in an early evaporative cooling scheme

The principle of evaporative cooling is relatively simple. Air moving past water will cause the water to evaporate. The heat necessary to cause evaporation is drawn out of the passing airstream and hence the air is cooled. 

The human body uses this principle to control body temperature by varying the amount of moisture on the skin surface (perspiration). The evaporation of this moisture cools the skin and helps to lower the body temperature.

The amount of heat transfer depends on the evaporation rate, however for each kilogram of water vaporized 2,257 kJ of energy is transferred. The evaporation rate depends on the temperature and humidity of the air, which is why sweat accumulates more on hot, humid days, as it does not evaporate fast enough.

Another factor is the airflow. The higher the airflow, the more evaporation occurs and the cooler the body will become. And there modern humans create a problem, by dressing up in nice uniforms made of materials that prevent them to sweat.

The solution to this dilemma is simple. Dress in loose fitting uniforms, wear sweat aiding underwear (no cotton!) and use air-vests to increase the airflow around the body. This will assist your body in its natural capability to evaporate the sweat and with that to cool down.