The design of heat exchanging equipment is strongly influenced by the physical properties of the fluids to be heated or cooled, as far as they are important for determining heat transfer rates, pressure drops, and momentum. A great number of physical property data for various fluids are listed in Section 5.5, but it sometimes occurs that for a certain fluid no data are available or the range of given data is not sufficient. In order to cover these cases many methods for estimating properties of gases and liquids have been developed. Some of them are simple and easy to employ, but-due to the real nature of the phenomena, which is generally complicated-their results are not too reliable. More elaborate methods can give better results, but they are often restricted to limited groups of compounds (mostly organic). Some of these methods can be evaluated economically only with the aid of a computer. Very good collections of estimating methods have been published, especially Reid et al. (1977) or Hecht et al. (1966).

In this chapter an attempt is made to give some of the simpler rules and methods which may be sufficient in many cases. At least, they may help to decide if more elaborate methods or the services of a data center are required where not only the available data but also the most modem estimating methods are computerized. This step is recommended in all cases where the exactness of the data is essential.

References

1. Reid, R.C., J.M. Prausnitz and T.K. Sherwood (1977). The Properties of Gases and Liquids. McGraw-Hill, New York.
2. Hecht, G., H. Lehmann, H. Lehmann, I. Thielemann, E. Ruschitzky, B. Jacobi and C. Holste (1966). Berechnung thermodynamischer Stoffwerte von Gasen und Flüssigkeiten. VEB Deutscher Verlag für Grundstoff-Industrie. Leipzig.