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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%.
For locations at not more than 2000 ft (600 m) of altitude it is common practice to use the sea-level psychrometric chart. In the ω-t chart, the dry bulb temperature (t) appears as the abscissa (horizontal axis) and the humidity ratio (ω) appear as the ordinate (vertical axis). A chart is valid for a given air pressure (or elevation above sea ...
The graphic method utilizes an overlay on a psychrometric chart to indicate the operative temperatures and humidity at which thermal comfort is achieved in the winter (1.0 clo) and summer (0.5 clo). It is based on the Predicted Mean Vote (PMV) model. [ 4 ]
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.
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The psychrometric constant relates the partial pressure of water in air to the air temperature. This lets one interpolate actual vapor pressure from paired dry and wet thermometer bulb temperature readings. [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.
A common example is visual acuity testing with an eye chart. The person sees symbols of different sizes (the size is the relevant physical stimulus parameter) and has to decide which symbol it is. Usually, there is one line on the chart where a subject can identify some, but not all, symbols.