Air Psychrometrics

The study of moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content

Absolute Humidity of Air

Humidity - or moist - is the water vapor present in air where commonly used terms are Absolute, Specific and Relative Humidity

Air - Altitude, Density and Specific Volume

Density and the specific volume of air vary with elevation above sea level

Air - Molecular Weight

Dry air is a mixture of gases where the average molecular weight (or molar mass) can be calculated by adding the weight of each component

Air - Specific Heat at Constant Temperature and Various Pressure

Specific Heat of air at constant temperature 20oC and pressure ranging 0.01 to 100 atm

Air Composition

Dry air is a mechanical mixture of nitrogen, oxygen, carbon dioxide and more

Air Humidifying with Steam - Imperial Units

Amount of vapor (lb/h in 100 cfm) in humid air

Air Humidity measured by Dry and Wet Bulb Temperature

Estimate moist air relative humidity by measuring dry and wet bulb temperature

Air Properties

Density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl's number - air temperature ranging -150 oC to 400 oC

Changing the State of Air by Heating, Cooling, Mixing, Humidifying or Dehumidifying Processes

Basic air condition processes - heating, cooling, mixing, humidifying and dehumidifying by adding steam or water - psychometric diagrams and the Mollier charts

Compressed Air and Water Content

Saturation pressure and maximum water content in compressed air

Cooling and Dehumidifying Air

Cooling and dehumidifying processes of moist and humid air - sensible and latent cooling

Cooling Tower Efficiency

Maximum cooling tower efficiency is limited by the wet-bulb temperature of the cooling air


Classification of dehumidifiers

Density of Moist Humid Air

Density of dry air and water vapor - moist or humid air

Dry Air and Water Vapor - Density and Specific Volume - Imperial Units

Density and specific volume of dry air and water vapor at temperatures ranging 225 to 900 degF (107 to 482 degC)

Dry Air Properties

Dry air properties at temperatures ranging 175 - 1900 K - specific heat, ratio of specific heats, dynamic viscosity, thermal conductivity, Prandtl number, density and kinematic viscosity

Dry Bulb, Wet Bulb and Dew Point Temperatures

Dry Bulb, Wet Bulb and Dew Point temperatures are important to determine the state of humid air

Drying Force of Air

The drying force of air can be expressed with moisture holding capacity of air and the evaporation capacity from water surface to air

Enthalpy of Moist Air

The enthalpy of humid air consists of sensible and latent heat

Evaporation from Water Surfaces

Evaporation of water from water surfaces - like swimming pools or open tanks - depends on water temperature, air temperature, air humidity and air velocity above the water surface - online calculator

Evaporative Cooling

An evaporative cooling tutorial

Great Sensible Heat Factor - GSHF

Great Sensible Heat Factor is the ratio between sensible and total heat in a cooling coil

Heating Humid Air

Enthalpy change and temperature rise when heating humid air without adding moisture

Human Heat Gain

Heat gain from persons in air conditioned spaces - in btu/hr

Humid Air and the Ideal Gas Law

Pressure, temperature and volume for an ideal or perfect gas like air with water vapor - or moist air

Humidifying Air by Adding Steam or Water

Air can be humidified by adding water or steam

Humidifying Air with Steam - SI units

Use steam to humidify air

Humidity and Heat Index

Humidity and the apparent temperature

Humidity Ratio of Air

The ratio between the mass of water vapor present in moist air - to the mass of dry air

Ideal Gas Law

The relations between volume, pressure, temperature and quantity of a gas, including definition of density of a gas.

Indoor Comfort Temperature versus Outdoor Temperature

Recommended indoor comfort temperature vs outdoor temperature

Indoor Relative Humidity versus Outdoor Temperature and Relative Humidity

Indoor relative humidity versus outdoor temperature and relative humidity

Latent Heat Flow

Latent heat is the heat, when supplied to or removed from air, results in a change in moisture content - the temperature of the air is not changed

Maximum Moisture Carrying Capacity of Air

Maximum water content in humid air depends on temperature

Metabolic Heat Gain from Persons

Human metabolic heat gain in air conditioned rooms

Mixing Humid Air

The state of mixed moist air - enthalpy, heat, temperature and specific humidity

Moist Air - Density vs. Pressure

Density of moist air versus pressure ranging 75 - 1000 mm Hg

Moist Air and Daltons Law of Partial Pressure

Pressure in a mixture of dry air and water vapor - humid or moist air - can be estimated by using Daltons Law of Partial Pressures

Moist Air and Degree of Saturation

Humidity ratio of moist air to humidity ratio of saturated moist air

Moist Air Properties

Psychrometric table with humid air properties

Moisture Holding Capacity of Air

Moisture holding capacity of air increases with temperature

Mole Fraction of Water Vapor in Moist Air

Mole fraction of water vapor is the ratio of water molecules - to air and water molecules

Mollier Diagram 

The Mollier diagram is a graphic representation of the relationship between air temperature, moisture content and enthalpy - and is a basic design tool for building engineers and designers

Non-ideal gas - Van der Waals equation and constants

Listing of van der Waals constants for more than 200 gases, used to correct for non-ideal behavior of gases caused by intermolecular forces and the volume occupied by the gas particles

Outdoor Temperature and Relative Humidity - US Winter and Summer Conditions

Outdoor summer and winter design temperature and relative humidity in US states and cities

Properties of Air - temperatures ranging -100 to 1000 oF

Dynamic viscosity, thermal conductivity, specific heat and Prandtl number of air at moderate pressure - Imperial units

Psychrometric Chart - Barometric Pressure 29.921 inches of Mercury

A psychrometric chart in English units - temperature ranging 20oF to 120oF

Psychrometric Chart for High Temperatures at Sea Level

Psychrometric Chart in I-P Units at high temperature at sea level and barometric pressure 29.921 Inches of HG

Psychrometric Chart for Low Temperatures at Sea Level

Psychrometric chart in I-P Units at low temperature at sea level and barometric pressure 29.921 Inches of HG

Psychrometric Chart for Normal Temperatures at 5000 Feet Altitude

Psychrometric chart in I-P Units at 5000 feet and barometric pressure 24.896 Inches of HG

Psychrometric Chart for Normal Temperatures at 7500 Feet Altitude

Psychrometric chart in I-P Units at 7500 feet and barometric pressure 22.653 Inches of HG

Psychrometric Online Calculator

Calculate moist air properties in SI and Imperial units with this online calculator

Psychrometric Table - 29.92 Inches of Mercury

Dry and wet bulb temperature, pressure and weight saturated water vapor and air saturated with water vapor

Psychrometric Terms

Dry and Wet Bulb Temperature, Specific Volume, Relative Humidity,  Enthalpy and more ..

Relationship between Specific and Relative Humidity of Air

Calculating specific humidity of moist air - knowing relative humidity, water vapor and air density

Relative Humidity in Air

The relative humidity in air can be expressed by partial vapor and air pressure - density of the vapor and air - or by the actual mass of the vapor and air

Relative Humidity in Production and Process Environments

Recommended relative humidity in production and process environments - like libraries, breweries, storages and more

Removing Heat with Air

Estimating heat removed with air using wet bulb temperature

Room Sensible Heat Factor - RSHF

Room Sensible Heat Factor - RSHF - is defined as sensible heat load divided by total heat load in a room

Sensible Heat Flow

Sensible heat is dry heat causing change in temperature but not in moisture content

Sensible Heat Ratio - SHR

Sensible Heat Ratio - SHR - is defined as the sensible heat or cooling load divided by the total heat or cooling load

Specific Heat of Dry Air

Specific heat of dry air will vary with temperature

Specific Volume of Moist Air

Specific volume is defined as the total volume of humid air per mass unit of dry air

Transforming a Mollier Diagram to a Psychrometric Chart - or vice versa

The relation between Psycrometric charts and Mollier diagrams

Vapor Pressure in Moist Air

Vapor pressures vs. dry and wet bulb temperature in moist air

Water - Saturation Pressure

Online calculator, figures and tables showing water saturation (vapor) pressure at temperatures ranging from 0 to 370 °C and from 32 to 700°F - in Imperial and SI Units

Water Vapor and Saturation Pressure in Humid Air

The saturation pressure of water vapor in moist air varies with temperature

Water Vapor in Air

Weight of water vapor in air

Wet Bulb Globe Temperature (WBGT)

The wet bulb globe temperature can be used to measure general heat-stress index

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