Willis H Carrier. Father of Air Conditioning. R V Simha. Keywords. W H Carrier, rational psychro- metric formulae, psychrometric chart, invention of centrifugal. PSYCHROMETRIC CHART. ▫ Identify parts of the chart. ▫ Determine moist air properties. ▫ Use chart to analyze processes involving moist air. 35 40 45 50 0,36 55 Carrier PSYCHROMETRIC CHART NORMAL.
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No, it is not an offshoot of Scientology—thank goodness. Are you a heating and air conditioning professional?
Do you install ventilation systems with the skill and precision of Julia Psychrometriic baking a chicken potpie?
If you do, you should probably know something about psychrometrics.
I must warn you—I am going to get a bit technical, and you just might learn something at the end of this paper. But, I can guarantee that possessing sound, theoretical knowledge of psychrometrics will help you understand more about how ventilation systems function, as well enable you to simplify the technical workings of the systems when talking to clients.
Psychrometrics, at its core, is an area of engineering investigating the moist properties of air.
Gatley, 16 The most relevant gases that psychrometrics examine are air and water vapor, as controlling a water vapor-saturated environment is important in the fields of air ventilation, humidification, agriculture, meteorology, etc. Human comfort in large part depends on air humidification—the amount of gaseous water vapor may be the difference between a dry, parched throat in the winter and a sweaty, muggy environment in the summer!
The goal of an experienced ventilation professional is to use psychrometrics to ensure that the air is comfortably humidified so clients can live in comfort, as well as breathe easier. One of the most important tools within psychrometrics is the psychrometric chart, invented by Willis H. Gatley, 18 Carrier is considered the inventor of modern air conditioning, although like any landmark engineer, he had some help from previous research.
The original Carrier Psychrometric Chart was compiled from empirical data from meteorologist William Ferrel as well as a Professor Marvin. Gatley, 17 Carrier compiled this data to create a descendant of the Psychrometric Chart, called the Hygrometric Chart:. This chart possesses some features that would become a mainstay of modern psychrometric charts, such as dry bulb temperature on the horizontal axis, more commonly referred to as air temperature.
Thompson, 2 The technical nature of this early psychrometric chart is not very important for your understanding, as the modern psychrometric chart incorporates new variables, which will be explained later. What is important to note, however, is that psychrometrics has a long, storied history of over one hundred years, and has been a vital mainstay of the air conditioning trade. But more significantly, the psychrometric chart still serves as an important educational tool to professionals who want to learn more about how air humidification works.
Want to teach an old HVAC dog some new tricks? The technical aspects of the modern psychrometric chart will be discussed below. Here is a modern version of the psychrometric chart:.
The horizontal axis is air temperature, also known as dry-bulb temperature, which is indicated psycnrometric the reading of an unwetted bulb in a thermometer. Thompson, 1 The vertical axis is humidity ratio, which indicates how much water vapor is present in the air although this is a ratio, think of it as a number value!
PSYCHROMETRIC CHART CARRIER
The upmost, leftward-curved line in the psychrometric chart represents the maximum of water vapor that is present in the air at a given temperature. Note the curvature of the graph: Wet bulb temperature is represented by the diagonal lines that slope from right-to-left. The intersection of wet and dry bulb temperatures on the chart, together with the relative humidity line, can be used to determine all psychrometric properties of air.
If you are like me, you probably had to read that paragraph a few dozen times before you actually began to conceptualize what the chart is conveying.
A dry bulb air temperature thermometer reads degrees Fahrenheit and a wet bulb thermometer reads 68 degrees Fahrenheit. What is the relative humidity?
Find the vertical line on the graph marked — this is the degrees psychromrtric line. Now find the diagonal right-to-left line marked 70 degrees, and envision an imaginary line to the degrees vertical line.
Notice where they meet on the graph. The humidity ratio is the located on the vertical axis. The humidity ratio of this point is approximately. A cooling of air temperature represents a shift to the left. Find the vertical line marked Now, refer to the diagonal wet-bulb line of 68 degrees in the carrjer problem.
Chapter 10b: The Psychrometric Chart (Updated 7/22/)
Let me introduce another variable into the mix: This is because the grass cools rapidly, and moisture in the surrounding air condenses at a rate greater than it can evaporate. Refer to this example:. What is the dewpoint temperature of the air at 90 degrees Fahrenheit wet-bulb temperature and 80 degrees dry-bulb temperature?
Find the point where the vertical dry-bulb line and the diagonal wet-bulb line intersect. Now, imagine a vertical line descending from the point to the dry-bulb temperature x-axis. Therefore, the dewpoint temperature of the air at 90 degrees Fahrenheit wet-bulb temperature and 80 degrees dry-bulb temperature is 75 degrees Fahrenheit. Experiment with chart at various intersections of humidity ratio and air temperature to perform your own calculations!
Once you are able to understand the mathematics of the chart, it will make measuring the humidity of your systems quite an easy process. There is a recap of the technical terms introduced in this paper below. A tool used by engineers and ventilation professionals to determine psychrometric values such as the relative humidity, humidity ratio, and relative humidity.
Also known as air temperature, the reading of an unwetted bulb in a thermometer.
Psychrometrics Made Simple – United Trades
Dry-bulb temperature is indicated on the x-axis of the psychrometric chart. Indicated on the diagonal lines sloping from right-to-left on the psychrometric chart, wet-bulb temperature represents the reading of a thermometer with a wetted cotton wick around the bulb. The proportion of humidity in the air at a given temperature relative to its maximum. Represented by the sloping left-to-right lines in the chart possessing percent values.
The dew point is the temperature below which the water vapor in air condenses into liquid water at carier same rate psychrometfic which it evaporates. You must be logged in to post a comment. Type and press enter to search. Overview Psychrometrics, at its core, is an area of engineering investigating the moist properties of air.
Chartt of the Psychrometric Chart One of the most important tools within psychrometrics is the psychrometric chart, invented by Willis H.
Gatley, 17 Carrier compiled this data to create a descendant of the Psychrometric Chart, called the Hygrometric Chart: How does a Psychrometric Chart Work? Here is a modern version of the psychrometric chart: What is the humidity ratio at this point? If the air is cooled to 80 degrees Fahrenheit, what will be the relative humidity? Refer to this example: Conclusion Experiment with chart at various intersections of humidity ratio and air temperature to perform your own calculations!
The area of engineering investigating the moist properties of air. Thompson, 3 Humidity ratio: Simplified, the amount of water vapor in the air. Leave a Reply Cancel reply You must be logged in to post a comment.