=100%)
of the Psychrometric
Chart.
The following Water Vapor Saturation Data is required
in order to plot the Saturation Curve (Relative Humidity
=100%)
of the Psychrometric
Chart.
|
|
The basic information used to construct a psychrometric chart is the water vapor saturation data (Tsat, Pg) which is obtained from steam tables over the range from Tsat = 0.01°C through 50°C. The specific humidity
The saturation curve (100% relative humidity) is also known as the dew point curve is drawn as a red line. Notice that on the saturation curve the wet and dry bulb temperatures have the same values. For more information refer to Chapter 10b on the Psychrometric Chart ____________________________________________________________ Source of the (Tsat, Pg) data: NIST Chemistry WebBook - accessed Feb 2008 |
The major simplifying assumption in the construction of the chart is that the enthalpy of the mixture is assumed to be constant throughout the adiabatic saturation process (described in Chapter 10a). This implies that the evaporating liquid added does not significantly affect the enthalpy of the air-vapor mixture, leading to the constant slope wet bulb temperature / enthalpy lines defined by:
Note that this simplyfied linear equation results in an error of less than 1% over the temperature range 0.01°C to 50°C.
Finally the specific volume curves which complete the chart are given by:
Refer to the complete MATLAB program for Plotting the Psychrometric Chart using these equations.
______________________________________________________________________________________
Engineering Thermodynamics by Israel
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is then evaluated using the relative humidity
