What is a Psychrometric Table?
A psychrometric table is a fundamental tool used to determine the physical and thermal properties of air-water vapor mixtures. It helps professionals in fields like HVAC (Heating, Ventilation, and Air Conditioning), meteorology, and agriculture to analyze and control air humidity, temperature, and other related properties.
The tables on this page provide data for both Celsius
(-10°C- 40°C) and Fahrenheit
(14°F-
101°F) scales, allowing for precise readings based on
dry-bulb and wet-bulb temperature measurements.
A Brief History of Psychrometrics
The term psychrometrics comes from the Greek words "psyche" (meaning "cold" or "breath") and "metron" (meaning "measure"). The study of air and moisture mixtures dates back to the 18th century when scientists began investigating atmospheric humidity's effects on human comfort and industrial processes.
One of the key developments in psychrometrics was the invention of the psychrometer by Ernst Ferdinand August in the early 19th century. This device used two thermometers—one dry and one wet—to measure the air's humidity level. Over time, the data collected from such measurements were compiled into detailed psychrometric charts and tables, becoming indispensable tools for engineers and scientists.
How to Use a Psychrometric Table
-
Measure Dry-Bulb and Wet-Bulb Temperatures:
- The dry-bulb temperature is the regular air temperature measured with a standard thermometer.
- The wet-bulb temperature is measured using a thermometer with a wet cloth wrapped around its bulb, representing the cooling effect of evaporation.
-
Find the Corresponding Values:
- Locate your dry-bulb temperature on the table.
- Cross-reference it with your wet-bulb temperature to determine properties like relative humidity and dew point.
-
Apply the Data:
- Use the information for HVAC system optimization, weather prediction, agricultural planning, or any process where moisture control is critical.
Applications of Psychrometric Data
-
HVAC Systems: Psychrometric data helps in designing systems that regulate air temperature and humidity for optimal indoor comfort.
-
Meteorology: Weather forecasters use psychrometric principles to predict dew points, fog, and rainfall probabilities.
-
Agriculture: Farmers rely on humidity and temperature data to manage greenhouse environments, irrigation schedules, and crop health.
-
Industrial Processes: Industries like textile manufacturing, food processing, and pharmaceuticals use psychrometric data to maintain product quality.
Fun Facts About Psychrometrics
-
Evaporative Cooling: Psychrometrics explains why we feel cooler when we sweat. As sweat evaporates, it absorbs heat from our skin, lowering our body temperature.
-
Dew Point & Comfort: When the dew point is close to the actual air temperature, the air feels more humid and sticky. This is why summer nights can feel uncomfortable even if the temperature isn’t very high.
-
Fog Formation: Fog forms when the air reaches 100% relative humidity, causing water vapor to condense into tiny droplets. Psychrometric tables can predict the conditions under which fog will appear!
About the Tables Below
Whether you're working with Celsius
or Fahrenheit, use the tables below to get
psychrometric data for your projects. Each table provides
detailed intervals for precise readings:
These tables, together with an Psychrometric Calculator included
in the CHEMIX School software, is quite big and in the *.png
image format.
- Celsius Table
: Upper/Lower Horisontal Row: Dry-Wet (t
- T) up to 20°C (Intervals of 0.2°C)
Vertical Left Column: Minimum dry temp (t) =
-10°C and maximum dry temp (t) = 40°C
- Fahrenheit Table : Upper/Lower Horisontal Row: Dry-Wet (t- T) up to 34°F (Intervals of 0.4°F) Vertical Left Column: Minimum dry temp (t) = 14°F and maximum dry temp (t) = 101°F
