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A psychrometric chart is a graph of the thermodynamic parameters of moist air at a constant pressure, often equated to an elevation relative to sea level. The ASHRAE-style psychrometric chart, shown here, was pioneered by Willis Carrier in 1904. [10] It depicts these parameters and is thus a graphical equation of state. The parameters are:
English: This psychrometric chart represents the acceptable combination of air temperature and humidity values, according to the PMV/PPD method in the ASHRAE 55-2010 Standard. The comfort zone in blue represents the 90% of acceptability, which means the conditions between -0.5 and +0.5 PMV, or PPD < 10%.
The representation is made on a temperature-relative humidity, instead of a standard psychrometric chart. The comfort zone in blue represents the 90% of acceptability, which means the conditions between -0.5 and +0.5 PMV, or PPD < 10%.
The wet-bulb temperature is the lowest temperature that may be achieved by evaporative cooling of a water-wetted, ventilated surface.. By contrast, the dew point is the temperature to which the ambient air must be cooled to reach 100% relative humidity assuming there is no further evaporation into the air; it is the temperature where condensation (dew) and clouds would form.
The underlying property data for the Mollier diagram is identical to a psychrometric chart. At first inspection, there may appear little resemblance between the charts, but if the user rotates a chart ninety degrees and looks at it in a mirror, the resemblance is apparent. The Mollier diagram coordinates are enthalpy h and humidity ratio x.
Size of this JPG preview of this PDF file: 776 × 600 ... 1=Mollier Chart, IP Units}} ... Source=Hands Down Software HDPsyChart Psychrometric Analysis Program ...
The basic assumptions made for the 1962 version were: [3] air is a clean, dry, perfect gas mixture (c p /c v = 1.40) molecular weight to 90 km of 28.9644 (C-12 scale); principal sea-level constituents are assumed to be (in mole percent):
The dry-bulb temperature (DBT) is the temperature of air measured by a thermometer freely exposed to the air, but shielded from radiation. [1] The dry-bulb temperature is the temperature that is usually thought of as air temperature, and it is the true thermodynamic temperature.