Articles on Psychrometrics and HVAC
Guides to psychrometrics and the psychrometric chart for HVAC engineers, in IP units.
-
AHU Cooling Coil: Capacity and Dehumidification
How to size a cooling coil in an air handling unit. Calculating cooling capacity, dehumidification, dew point and the air state after the coil.
-
Energy Recovery (ERV/HRV): Efficiency and Savings
How to calculate energy recovery savings in HVAC: temperature effectiveness, air states on the psychrometric chart, plate vs. wheel, and standards.
-
Cleanroom Air: Temperature and Humidity Requirements
Psychrometric requirements for cleanrooms per ISO 14644 and cGMP: the effect of humidity on ESD and microbial contamination, and HVAC design.
-
Condensation in Buildings: Causes and Prevention
When and where water vapor condensation occurs, surface vs. interstitial condensation, and how to predict it from the dew point and the chart.
-
Data Center Humidity: Psychrometrics for IT
Data center psychrometrics: ESD and corrosion risks, ASHRAE classes A1–A4, free cooling and adiabatic cooling. How to optimize total energy use.
-
Industrial Drying and Psychrometrics: Dryer Design
Psychrometrics in industrial drying: the drying phases, energy balance, recirculation and a lumber-kiln example. Calculations on the psychrometric chart.
-
Meteorological Psychrometrics: Atmospheric Humidity
Psychrometrics in meteorology: the condensation level, adiabatic lapse rate, chinook winds and fog. EPW and TMY3 data for building energy simulation.
-
Psychrometrics in Agriculture: Greenhouses and Grain
Psychrometrics in agriculture: greenhouse VPD, grain equilibrium moisture (EMC) and post-harvest corn drying. Calculations on the psychrometric chart.
-
Air Conditioning Design on the Psychrometric Chart
Designing air conditioning with the psychrometric chart: design conditions, air mixing and cooling capacity. A worked example of an office for 100 people.
-
Air Humidification: Steam, Adiabatic or Ultrasonic?
Comparing humidification options in HVAC — steam, adiabatic, ultrasonic. Capacity calculation, hygiene and how each appears on the psychrometric chart.
-
Air Humidity Calculation: All the Psychrometric Formulas
A full reference of psychrometric equations: saturation vapor pressure (Buck, Magnus), humidity ratio, enthalpy, dew point and density. With examples.
-
Desiccant Dehumidification: Silica Gel and Zeolites
Desiccant dehumidification with silica gel and desiccant wheels: the principle, the psychrometric chart and uses in industry, pharma and storage.
-
Dew Point Calculation: Formulas, Tables, Calculator
How to calculate dew point from dry-bulb temperature and relative humidity. Magnus–Tetens, ASHRAE comparison, and worked examples in IP units.
-
Evaporative Cooling: Efficiency and Psychrometric Chart
How evaporative (adiabatic) cooling works, calculating saturation efficiency and plotting it on the psychrometric chart. Direct vs. indirect cooling.
-
Calculating Moist Air Enthalpy: Formula and Tables
How to calculate moist air enthalpy from temperature and humidity. ASHRAE IP formula plus worked examples of heating and cooling coil capacity.
-
Moist Air Processes: Heat, Cool, Humidify, Dry
Heating, cooling, humidification and drying on the psychrometric chart — the four basic processes with examples and capacity calculations.
-
The Psychrometric Chart: Guide for HVAC Engineers
Learn to read the psychrometric chart, plot air-treatment processes and export the result to your submittal. Calculations per ASHRAE Fundamentals 2021.
-
Relative Humidity: Definition, Changes, Measurement
What relative humidity is, why it changes with temperature, and how to measure it. Recommended levels for homes, museums and data centers.
-
Thermal Comfort PMV/PPD: Calculation per ISO 7730
What the PMV and PPD indices are, how thermal comfort is calculated and the role of air humidity. Standards ASHRAE 55 and ISO 7730.
-
Wet-Bulb Temperature: Physics and Measurement
What wet-bulb temperature is, how a psychrometer measures it and where to find it on the psychrometric chart. Dew point difference and Sprung equation.
-
What Is Psychrometrics? A Guide to Moist Air Science
Psychrometrics made clear: humidity ratio, enthalpy, dew point and the psychrometric chart. Practical uses in HVAC, drying and building science.
Try the interactive psychrometric chart
Open PsychroView →