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

The density and the specific volume of air varies with elevation above sea level

Air - Molecular Mass

Dry air is a mixture of gases where the molecular weight 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 Properties

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

Changing Air Condition 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

Comparing Mollier Diagrams and Psychrometric Charts

Transform between Psycrometric charts and Mollier diagrams

Cooling Tower Efficiency

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

Cooling and Dehumidifying Air

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

Dehumidfication Process in a Psychrometric Chart

Dehumidification tutorial with psychrometric charts


Classification of dehumidifiers

Density of Dry Air, Water Vapor and Moist Humid Air

Calculate the density of dry air, water vapor or the mixture of air and water vapor - moist or humid air

Dry Air and Water Vapor Mix - Density and Specific Volume

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

Dry Bulb, Wet Bulb and Dew Point Temperatures

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

Drying Force of Air

Drying Force of air may be expressed as moisture holding capacity of air and evaporation capacity from water surface to air

Enthalpy of Moist and Humid Air

The enthalpy of moist and humid air is sensible and latent heat

Evaporation from Water Surfaces

The amount of evaporated water from a water surface - like a swimming pool or an open tank - depends on the temperature in the water - and the temperature, humidity and velocity of the air above the 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 for a cooling coil

Heat Removed with Air

Estimate the heat removed by air - using the wet bulb temperature

Heating Humid Air

Calculating enthalpy change and temperature rise when heating moist and humid air without adding moisture

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 Ratio of Air

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

Humidity and Heat Index

Temperature and humidity factor

Ideal Gas Law

In perfect or ideal gas the change in density is directly related to the change of temperature and pressure as expressed by the Ideal Gas Law

Indoor Temperature versus Outdoor Temperature

Recommended indoor temperature versus outdoor temperature

Introduction to Psychrometry

An introduction to air psychrometrics

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 Content in Air

The moisture limits in air varies with temperature

Measuring Air Humidity

Measuring relative air humidity with dry and wet bulb temperature

Metabolic Heat Gain from Persons

Metabolic heat gain from occupants in air conditioned spaces at different degrees of activities - in Watts

Mixing Humid Air

Calculating enthalpy, heat, temperature and specific humidity in mixing humid air

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 Properties

Psychrometric table with moist humid air properties

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

Moisture Holding Capacity of Air

Moisture holding capacity of air varies 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

Outdoor Temperature and Relative Humidity - US Winter and Summer Conditions

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

Outdoor to Indoor Temperature Rise - Relative Humidity

The effect on relative humidity when outdoor air temperature is raised to indoor temperature

People and Heat Gain

Heat Gain from Occupants in Air Conditioned Spaces - in btu/hr

Pressure and Water Content in Saturated Air

Air pressure and maximum water content in saturated air

Psychrometric Chart - Barometric Pressure 29.921 inches of Mercury

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

Psychrometric Chart - Normal Temperatures at Sea Level

Sea Level Psychrometric Chart - Ledger Size - Both US and SI units

Psychrometric Chart at 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 at 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 at Normal Temperatures at 5000 Feet

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

Psychrometric Chart at Normal Temperatures at 7500 Feet Altitude

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

Psychrometric Chart in SI Units for Download

A downloadable psychrometric chart at normal temperatures in SI Units

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 Humidities in Production and Process Environments

Recommended Relative Humidities in production and process environments like libraries, breweries, storages and more

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

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 a 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

Vapor Pressure in Moist Air

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

Water Flow through Hoses - Pressure Loss

Pressure loss due to friction in hoses

Water Saturation Pressure

Water saturation pressure at temperatures ranging 0 - 100oC and 32 - 700oF - Imperial and SI Units

Water Vapor - Weight in Air

Weight of water vapor in air

Water Vapor and Saturation Pressure in Humid Air

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

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