Part 3 of this article details how the underlying physics principles of heat and heat transfer were translated by Carrier into a viable air-conditioning system. The chart is widely available online, of course, and also as printed pads. Many versions of the chart highlight an area in the center – bounded approximately by 68⁰F and 82⁰F (20⁰F and 28⁰C) on the left and right, and 30 to 70 percent relative humidity on the top and bottom – as the zone in which most people feel comfortable.
Once you know this point, you can determine all the other air-property variables at this state point. (Image: )Ī single point on the psychrometric chart is defined by the intersection of any two-variable lines and represents a unique “state point” for air properties. (Image: Parker Hannifin Corp) Fig 4: This simplified (metric) psychrometric chart shows the relationship among the critical air-property variables it defines a specific state point based on the intersection of any two property lines.
#CARRIER PSYCHROMETRIC CHART SI UNITS MOVIE#
The first installations of his radical system, which weighed several tons, were in movie theaters and department stores, as they needed a way to draw customers inside on hot, humid days and could afford the cost and size. His patent (US808897A) consists of just one page of drawings and a little over two text pages. After several false starts due to constituent parts’ inadequate performance, he devised a compression-based system that was patented in 1906. He knew that cool air holds less water vapor than warm air, and realized that if his system could saturate the air and then control its temperature at saturation, as a machine-made fog, it could control the amount of moisture in the air. Also, they did not lower humidity, a major component of discomfort, and, in fact, they often raised it.Īccording to his recollections, Carrier had a flash of insight while waiting for a train platform on a foggy night as temperatures dipped toward freezing. These energy-consuming but passive techniques were not effective (except perhaps psychologically). Others used air blown across the pipes filled with relatively cool water from a stream that was pumped through them.
Methods included using fans to blow air across ice blocks or spraying cool-water mists into the air circulated into an area. Inventors tried other approaches to cooling hot, humid areas, but they had limited success. Willis Carrier was not the first person to attempt to cool air, of course. Part 1 of this article reviewed basic thermal and heat concepts and measurement units related to air conditioning this part looks at the development of such systems,
#CARRIER PSYCHROMETRIC CHART SI UNITS PLUS#
We take air conditioning (cooling plus humidity control) for granted, and its development is largely due to one man’s “flash” of insight related to thermal principles and basic physics.