Page 337 - Chemical engineering design

312
thermal expansion, viscosity and radiative properties (emittance, reflectance, absorptance
and transmittance). CHEMICAL ENGINEERING
Elsevier have published a series of volumes on physical property and thermodynamic
data. Those of use in design are included in the Bibliography at the end of this chapter.
The Engineering Sciences Data Unit (ESDU, www.ihsesdu.com) was set up to provide
validated data for engineering design, developed under the guidance and approval of
engineers from industry, the universities and research laboratories. ESDU data include
equipment design data and software and extensive high-quality physical property data
mostly for pure fluids that are in use in the oil and process industries and in university
chemical and mechanical engineering departments worldwide.
Caution should be exercised when taking data from the literature, as typographical
errors often occur. If a value looks doubtful it should be cross-checked in an independent
reference, or by estimation.
The values of some properties will be dependent on the method of measurement; for
example, surface tension and flash point, and the method used should be checked, by
reference to the original paper if necessary, if an accurate value is required.
The results of research work on physical properties are reported in the general
engineering and scientific literature. The Journal of Chemical Engineering Data
specialises in publishing physical property data for use in chemical engineering design. A
quick search of the literature for data can be made by using the abstracting journals; such
as Chemical Abstracts (American Chemical Society) and Engineering Index (Engineering
Index Inc., New York). Engineering Index is now called Engineering Information (Ei) and
is a web-based reference source owned by Elsevier information (www.ei.org).
Computerised physical property data banks have been set up by various organisations
to provide a service to the design engineer. They can be incorporated into computer-aided
design programs and are increasingly being used to provide reliable, authenticated, design
data. Examples of such programs are the PPDS and the DIPPR databases.
PPDS (Physical Property Data Service) was originally developed in the United Kingdom
by the Institution of Chemical Engineers and the National Physical Laboratory. It is now
available as a Microsoft Windows version from NEL, a division of the TUV Sudde-
untschland Group (www.nel.uk). PPDS is made available to universities at a discount.
The DIPPR databases were developed in the United States by the Design Institute
for Physical Properties of the American Institute of Chemical Engineers. The DIPPR
projects are aimed at providing evaluated process design data for the design of chemical
processes and equipment (www.aiche.org/dippr/projects.htm). The Project 801 has been
made available to university departments; see Rowley et al. (2004) and http.//dippr.byu.
edu/description/htm.

8.4. ACCURACY REQUIRED OF ENGINEERING DATA

The accuracy needed depends on the use to which the data will be put. Before spending
time and money searching for the most accurate value, or arranging for special measure-
ments to be made, the designer must decide what accuracy is required; this will depend
on several factors: