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Air Psychrometrics

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

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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 - Composition and Molecular Weight

Dry air is a mechanical mixture of nitrogen, oxygen, argon and several other gases in minor amounts

Air - Density at varying pressure and constant temperatures

Figures and tables showing changes in air density at pressure varying from 1 to 10 000 bara (14.5 - 145000 psi) and constant, selected temperatures. Figures are given in different scales.

Air - Density, Specific Weight and Thermal Expansion Coefficient at Varying Temperature and Constant Pressures

Online calculator, figures and tables showing density, specific weight and thermal expansion coefficient of air at temperatures ranging -100 to 1600 °C (-140 to 2900 °F) at atmospheric and higher pressure - Imperial and SI Units

Air - Diffusion Coefficients of Gases in Excess of Air

Diffusion coefficients, D12, for gases in large excess of air at temperature varying from 0 - 400 °C

Air - Dynamic and Kinematic Viscosity

Online calculator, figures and tables showing dynamic (absolute) and kinematic viscosity of air at temperatures ranging from -100 to 1600°C (-150 to 2900°F) at pressure ranging from 1 to 10 000 bara (14.5 - 145000 psia) - SI and Imperial Units

Air - Maximum Moisture Carrying Capacity

Maximum water content in humid air depends on temperature

Air - Molecular Weight and Composition

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 - Prandtl Number

Figures and table showing changes in Prandtl number for air with changes in temperature and pressure

Air - Properties at Gas-Liquid Equilibrium Conditions

Figures and tables showing how the properties of air changes along the boiling and condensation curves (temperature and pressure between triple point and critical point conditions). An air phase diagram are also given.

Air - Specific Heat at Constant Pressure and Varying Temperature

Online calculator, figures and tables showing how specific heat (Cp and Cv) of dry air vary with temperature at different pressures, SI and imperial units

Air - Specific Heat at Constant Temperature and Varying Pressure

Figures and table showing isobaric (Cp) and isochoric (Cv) specific heat of air at constant temperature and varying pressure ranging 0.01 to 10000 bara

Air - Thermal Conductivity

Online calculator, figures and tables showing air thermal conductivity at varying temperature and pressure, SI and imperial units.

Air - Thermal Diffusivity

Figures and tables showing dry air thermal diffusivity at varying temperarure and pressure, SI and Imperial units

Air - Thermophysical Properties

Thermal properties of air - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusicity, and more

Air Humidity measured by Dry and Wet Bulb Temperature

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

Air Humidity Ratio

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

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Air- Moisture Holding Capacity vs. Temperature

Moisture holding capacity of air increases with temperature

Ammonia - Density at Varying Temperature and Pressure

Online calculator, figures and tables showing density and specific weight of ammonia at temperatures ranging -50 to 425 °C (-50 to 800 °F) at atmospheric and higher pressure - Imperial and SI Units

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 Water Content

Saturation pressure and maximum water content in compressed air

Cooling and Dehumidifying Moist 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 Surface

Evaporation of water from a water surface - like a swimming pool or an open tank - 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

Heat Recovery Efficiency

Classification of heat recovery efficiency - temperature efficiency, moisture efficiency and enthalpy efficiency - online heat exchanger efficiency calculator

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 - Imperial Units

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

Humidifying Air with Steam - SI units

Use steam to humidify air

Humidity and Heat Index

Humidity and the apparent temperature

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

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 - Degree of Saturation

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

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 Properties

Psychrometric table with humid air properties

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 Waal's 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

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 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

Universal and Individual Gas Constants

The Universal and Individual Gas Constants in fluid mechanics and thermodynamics. Individual gas constant is given for the most common gases.

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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