Thermodynamics in pressure vessels for pressure surge protection

Abstract

The correct design of pressure vessels for pressure surge protection requires an accurate description of the thermodynamic processes, in particular the heat exchange with the compressed air cushion. The article presents a calculation approach for this purpose, which records the essential balance variables of the heat transfer. The essential balance variables are the conductive and convective heat transfer, the condensation heat of the water vapor during decompression, the radiant heat of the wall, which is absorbed by condensed mist droplets, and the solidification heat when the temperature falls below the freezing point. The approach is validated using measured values by comparing the change in the internal energy of the compressed air cushion. The data from decompression and compression tests as well as from pump shutdowns show good agreement. This means that the mostly used but less accurate approach using a constant polytropic exponent can be replaced in pressure surge programs.