UFC 3-400-02

28 FEBRUARY 2003

2-4.2.2

It is often useful to calculate the behavior of the proposed system at "most

common" conditions and assess these calculations in addition to the traditional peak

design calculations. This will help ensure that the selected equipment and controls are

capable of modulation and control at all points of operation rather than simply at

extreme conditions.

2-5

Figure 2-4 is an example of Data Set Page 4, a psychometric display of the site's

design values.

2-5.1

Similar to Data Set Page 3, this chart depicts the saturation curve (when

RH = 100%) along with peak design values. The design values are calculated as in the

table on Data Set Page 1 (Figure 2-1), but this chart shows their relationships

graphically, depicting their position relative to each other and relative to the saturation

curve.

2-5.2

Above and to the left of the saturation curve, RH would be greater than

100% (not possible). The area below and to the right of the curve (including the points

on the curve itself) represent the area where RH is less than or equal to

100%, and thus where all observations occur. Note that since the humidity ratio is a

function of pressure, and pressure varies with elevation, different sites will have

different saturation curves.

2-5.3

The dry bulb temperature is the horizontal coordinate on this scatter plot,

and the humidity ratio is the vertical coordinate. Peak design values are depicted by the

red square (1.0% Temperature [dry bulb]), the green circle (1.0% Humidity Ratio), and

the blue diamond (99% Temperature [dry bulb]).

2-5.4

The table below the chart shows the exact values of 99% dry bulb

temperature, 1.0% humidity ratio, and 1.0% dry bulb temperature, along with calculated

values of enthalpy, mean coincident wet bulb temperature, and humidity ratio (as

applicable). The value of enthalpy coincident to each temperature/humidity ratio is

created using the psychrometric functions provided by the Linric Company, Bedford,

New Hampshire. The dry bulb temperature and humidity ratio are used to calculate

enthalpy using the Linric algorithms.

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