These are straight horizontal lines measuring the actual mass of water vapor per mass of dry air (grains/lb or g/kg). This tells you how much moisture is in the air.
Once you learn to see the air through these lines, you will never look at a cloudy window or a sweat glass of iced tea the same way again. You are seeing psychrometrics in action. Standard psychrometric charts are published by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and are available for various altitudes. psychrometric graph
The term comes from the Greek psukhros (cold) and metron (measure). While it measures "cold," its real power lies in measuring change. To read the chart, you must identify its seven fundamental components. Most charts are plotted with Dry Bulb Temperature (the temperature your thermometer reads) on the horizontal axis. These are straight horizontal lines measuring the actual
These are sweeping parabolic curves. Each curve represents a percentage of saturation (0% to 100%). The 100% RH line is the Saturation Line . Air cannot hold more moisture beyond this line; it will start to condense (dew, fog, rain). You are seeing psychrometrics in action
These are slightly sloped diagonal lines indicating the volume occupied by a unit mass of dry air (cubic feet per pound). This is critical for sizing fans and ducts.
These are diagonal lines sloping downwards to the right. The wet bulb temperature is measured by a thermometer with a wet wick. It represents the cooling effect of evaporation. Along the saturation line, WBT = DBT.
This is the temperature at which the air becomes saturated (100% RH) if cooled at constant pressure. To find it, move horizontally left from your point to the saturation curve.
These are straight horizontal lines measuring the actual mass of water vapor per mass of dry air (grains/lb or g/kg). This tells you how much moisture is in the air.
Once you learn to see the air through these lines, you will never look at a cloudy window or a sweat glass of iced tea the same way again. You are seeing psychrometrics in action. Standard psychrometric charts are published by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and are available for various altitudes.
The term comes from the Greek psukhros (cold) and metron (measure). While it measures "cold," its real power lies in measuring change. To read the chart, you must identify its seven fundamental components. Most charts are plotted with Dry Bulb Temperature (the temperature your thermometer reads) on the horizontal axis.
These are sweeping parabolic curves. Each curve represents a percentage of saturation (0% to 100%). The 100% RH line is the Saturation Line . Air cannot hold more moisture beyond this line; it will start to condense (dew, fog, rain).
These are slightly sloped diagonal lines indicating the volume occupied by a unit mass of dry air (cubic feet per pound). This is critical for sizing fans and ducts.
These are diagonal lines sloping downwards to the right. The wet bulb temperature is measured by a thermometer with a wet wick. It represents the cooling effect of evaporation. Along the saturation line, WBT = DBT.
This is the temperature at which the air becomes saturated (100% RH) if cooled at constant pressure. To find it, move horizontally left from your point to the saturation curve.