Articles on psychrometrics and HVAC
Guides to psychrometrics and the Mollier diagram for HVAC engineers.
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AHU cooling coil: capacity and dehumidification
How to design a cooling coil in an air handling unit. Calculating the cooling capacity, dehumidification, dew point and the air state after the coil.
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Heat recovery (HRV): efficiency and energy savings
How to calculate HRV energy savings in HVAC: temperature efficiency, air states in the h-x diagram, plate vs. rotary exchanger, and standards.
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Cleanroom air: temperature and humidity requirements
Psychrometric requirements for cleanrooms per ISO 14644 and EU GMP: the effect of humidity on ESD and microbial contamination, and HVAC design.
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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 h-x diagram.
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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.
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Industrial drying and psychrometrics: dryer design
Psychrometrics in industrial drying: the drying phases, energy balance, recirculation and a wood-dryer example. Calculations on the h-x diagram.
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Meteorological psychrometrics: atmospheric humidity
Psychrometrics in meteorology: the condensation level, adiabatic lapse rate, the föhn effect and fog. EPW climate data for building energy simulation.
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Psychrometrics in agriculture: greenhouses and grain
Psychrometrics in agriculture: greenhouse VPD, grain equilibrium moisture (EMC) and post-harvest corn drying. Calculations on the h-x diagram.
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Air conditioning design on the h-x diagram
Designing air conditioning with the h-x diagram: design conditions, air mixing and cooling capacity. A worked example of an office for 100 people.
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Air humidification: steam, adiabatic or ultrasonic?
Comparing air humidification options in HVAC — steam, adiabatic, ultrasonic. Capacity calculation, hygiene and how each appears on the h-x diagram.
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Air humidity calculation: psychrometric formulas
A full reference of psychrometric equations: saturation vapor pressure (Buck, Magnus), humidity ratio, enthalpy, dew point and density. With examples.
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Desiccant dehumidification: silica gel and zeolites
Desiccant dehumidification with silica gel and rotary dehumidifiers: the principle, the h-x diagram and uses in industry, pharma and storage.
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Dew point calculation: formulas, tables, calculator
How to calculate the dew point from temperature and relative humidity. Magnus–Tetens equation, ASHRAE comparison, and examples for HVAC engineers.
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Evaporative cooling: efficiency and the h-x diagram
How evaporative (adiabatic) cooling works, calculating the saturation efficiency and plotting it on the h-x diagram. Direct vs. indirect cooling.
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Calculating moist air enthalpy: formula and tables
How to calculate the enthalpy of moist air from temperature and humidity. ASHRAE formula plus worked examples of heating and cooling coil capacity.
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Moist air processes on the h-x diagram
Heating, cooling, humidification and drying on the h-x diagram — the four basic psychrometric processes with examples and capacity calculations.
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The Mollier (h-x) diagram: a guide for HVAC engineers
Learn to read the Mollier h-x diagram, plot air-treatment processes and export the result to your report. Calculations per ASHRAE Fundamentals 2021.
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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.
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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.
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Wet-bulb temperature: physics and measurement
What wet-bulb temperature is, how a psychrometer measures it and where to find it on the h-x diagram. Difference from dew point and the Sprung equation.
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What is psychrometrics? A guide to moist air science
Psychrometrics made clear: humidity ratio, enthalpy, dew point and the h-x diagram. Practical uses in HVAC, drying and building physics.
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