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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%.
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:
The results are displayed on a psychrometric or a temperature-relative humidity chart and indicate the ranges of temperature and relative humidity that will be comfortable with the given the values input for the remaining four parameters. [44] The PMV/PPD model has a low prediction accuracy. [45]
English: This chart represents the acceptable combination of air temperature and humidity values, according to the PMV/PPD method in the ASHRAE 55-2010 Standard. The representation is made on a temperature-relative humidity, instead of a standard psychrometric chart.
ANSI/ASHRAE Standard 55 provides a table of metabolic rate of different continuous activities. These values are valid for an average adult with surface skin area of 1.8 m 2 (19.6 ft 2). The standard reminds the users that they should use their own judgment to match the activities being considered to the comparable activities in the table.
Figure 2: On a standard psychrometric chart, the air flow state points of the Cromer cycle are shown. The psychrometric process of the air passing through the system with four state points is shown on the psychrometric chart of Figure 2 as 1, 2, 3 and 4. The state points of the air are also depicted in Figure 1.
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.