Dehumidify with a Waterfall? - Short #259 · HVAC School - For Techs, By Techs summary

Key takeaways

Willis Carrier was instrumental in creating the first modern air conditioner in 1902 by discovering the importance of dew point in humidity control.
Psychometrics is crucial in understanding how air can hold moisture and at what temperatures condensation occurs.
The romantic idea of using waterfalls for dehumidification has many practical limitations, which modern HVAC systems have addressed.
Carrier's innovation set the stage for current technologies, showing the evolution of HVAC systems and their importance in climate control.

Summary

History of Dehumidification

In this episode, Bryan discusses the historical context of dehumidification, tracing back to 1902 when Willis Carrier devised a solution to humidity issues at a printing company. He discovered that by cooling the air below its dew point, moisture could be removed, leading to the invention of the first modern air conditioner. His method involved spraying chilled water into the air to reduce humidity, which highlighted the principles of psychometrics.

Psychometrics Explained

Bryan explains psychometrics in the context of air moisture. The dew point is the temperature at which air cannot hold any more water vapor. When air is cooled below this temperature, moisture condenses. He illustrates this by connecting Carrier's method to the concept of a cooling coil, emphasizing that understanding dew point is essential for effective dehumidification.

Limitations of Waterfall Dehumidification

While the idea of using a waterfall for dehumidification sounds appealing, Bryan discusses the practical drawbacks. Issues such as algae growth, corrosion, and the costs associated with pumping water are significant. Modern systems have evolved to more efficient designs like chilled water and direct expansion coils, which avoid these complexities.

Carrier's Innovations and Modern Implications

The podcast culminates in discussing how Carrier's foundational work laid the groundwork for modern HVAC systems. Bryan reflects on how the same principles apply today with different technologies, while still emphasizing the importance of managing humidity effectively in air conditioning systems.

Show notes

In this short podcast episode, Bryan talks about history and HVAC science: how to dehumidify the air with a waterfall and how cold water became the first air conditioner.

In 1902, Willis Carrier worked for a printing company in Brooklyn, New York. There was a huge humidity problem during the summer: the printing plant got damp, causing paper to swell and ink to smudge. Carrier realized that he could wring water out of the air if he brought the air's temperature below the dew point. His solution was to spray chilled water into the airstream; he filed a patent for an invention that would pass air through a mist of cool water, which caused it to cool down and shed its moisture. He called it the "apparatus for treating air."

This invention applies basic psychrometric principles. Air holds water vapor up to a certain point. The dew point defines that point. If the air is full of water vapor and its temperature drops below that dew point, excess water vapor condenses to liquid water (such as when it passes over an evaporator coil). In the case of Carrier's invention, the cold water in the spray chamber acted as a giant cooling coil. However, if the water is warm, the opposite effect would happen.

We do NOT dehumidify with liquid water due to the requirement for water treatment (to prevent algae and scale buildup). Cold water is less prone to bacterial and algal growth than warm water, but it's still essentially an indoor science experiment. Water is also messy and causes corrosion, and pumping it is expensive. Carrier's experiment evolved to the chilled water coil, which then evolved to the DX coils we see today.

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Dehumidify with a Waterfall? - Short #259