Psychrometrics

Psychrometry is the thermodynamics of moist air. All conditions of humid air can be used as gas-vapor mixture of dry air (referred to as "gas" ) and water vapor (referred to as "steam" ) represent. The gas - vapor mixture thus consists of condensing and non- condensing components and behaves, as well as its two components, typical for the in meteorology and air conditioning ( air conditioning systems ) boundary conditions of temperature and pressure similar to ideal gases.

Representing let the states and state changes of the moist air in the hx diagram ( enthalpy vs. Vapor loading of the air ). Germany in the Mollier diagram is mainly used as the carrier diagram is applicable in the USA. Mollier diagram in the considered area of the unsaturated with water vapor was expanded by rotation of the abscissa of the coordinate system. The rotation is so conducted that the isotherm for zero degrees Celsius is even to the horizontal. The Enthalpielinien proceed accordingly not horizontal, but run with a gradient of the slope, which corresponds to the heat of vaporization of water at zero degrees Celsius. In the diagram, the relative humidity and the density of the air mixture are entered as a parameter in addition to the isotherms.

In the Mollier diagram can be mixing processes with two air currents, heating an air stream, cooling of air and pose without dehumidification and humidification by evaporation of water or steam.

As an example of the practical application of the determination of the humidity Psychrometrics be mentioned about the temperature difference between two thermometers. Such an instrument is called a psychrometer.

Here, one of thermometer is moistened with water ( wet bulb thermometer wet bulb = ). Through evaporation, the thermometer is cooled. The cooling is greater, the lower the relative humidity. ( sufficient air movement provided )

Example

At a temperature of 30 ° C and 50% RH, the wet bulb thermometer is cooled to 22 ° C.