Psychrometric software

Psychrometric Software and Tables As an alternative to using charts or individual calculations, lookup tables have been published for many years for common psychrometric conversions, e.g., to find relative humidity given the dry-bulb and wet-bulb temperatures. These were often very extensive. To give precise coverage of in 1°C or 0.1°C steps, a complete table woul(3 be needed for each individual dry-bulb temperature. 

Software may be effectively used to draw psychrometric charts or perform calculations. A wide variety of other psychrometric software may be found on the Internet, but quality varies considerably the... 

For practical purposes, the properties of humid air are recorded on psychrometric (or humidity) charts such as those of Figures 9.1 and 9.2, but tabulated data and equations also are available for greater accuracy. A computer version is available (Wiley Professional Software, Wiley, New York). The terminal properties of a particular adiabatic humification of air are located... 

For practical purposes, the properties of humid air are recorded on psychrometric (or humidity) charts such as those of Figures 9.1 and 9.2, but tabulated data and equations also are available for greater accuracy. A computer version is available (Wiley Professional Software, Wiley, New York). The terminal properties of a particular adiabatic humification of air are located on the same saturation line, one of those sloping upwards to the left on the charts. For example, all of these points are on the same saturation line (7)//) = (250,0.008), (170, 0.026) and (100,0.043) the saturation enthalpy is 72 Btu/lb dry, but the individual enthalpies are less by the amounts 2.5, 1.2, and 0, respectively. 

Software is available that will perform calculations of humidity parameters for any point value, and for plotting psychrometric charts. Moreover, British Standard BS 1339 Part 2 (2006) provides functions as macros which can be embedded into any Excel-compatible spreadsheet. Users can therefore generate their own tables for any desired combination of parameters as well as perform point calculations. Hence, the need for published lookup tables has been eliminated. However, this software, like the previous lookup tables, is only valid for the air-water system. For other vapor-gas systems, the equations given in previous sections must be used. 

FIG. 12-7 Mollier psychrometric chart (from PSYCHIC software program) showing determination of adiabatic saturation temperature plots humidity (abscissa) against enthalpy (lines sloping diagonally from top left to bottom right). Courtesy AspenTech.)... 

Drying Software Several software programs for psychrometric charts and calculations are available and are described in the Psy-chrometry section. 

Electronic reference software applications provide source data used in technical operations. They are typically externally developed and accepted as authoritative by the purchasing firm. Where employed, they are important resources for specialized technical users. Software in this group included the 2000 International Building Code, Plumbing/Mechanical, Akton Psychrometric Chart for Windows, and AHFS First. The first two are self-explanatory the third is a pharmaceutical database. 

Free software available on the Internet for humidity and psychrometric calculations is of limited value for practical drying calculations such as dryer flowsheet calculations since drying problems are much more complicated than simple psychrometric calculations. 

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