CONDENSATION OF PURE FLUIDS AND MIXTURES OF PROCESS FLUIDS IN COMPACT WELDED AND SPIRAL HEAT EXCHANGERS

Condensation occurs in many industrial processes, but rarely with pure fluids. The fluids encountered are mixtures and often non-condensable gases are present, and this makes the condensation process very complex.
This paper presents experimental results of the condensation in presence of inert gases of process fluids in two geometries of compact heat exchangers: welded plate and spiral heat exchangers. The tests have been performed using pentane and isopropanol in order to investigate the effect of viscosity during the condensation processes.
In both cases the heat transfer coefficient increases with the Reynolds number, which reveals the effect of the inert gases. For low condensate Reynolds number (below 100), we can assume, referring to the tests with pure fluid (Thonon and Bontemps 2002), that the liquid Him is almost laminar. Therefore, for a pure fluid, the heat transfer coefficient should decrease while increasing the Reynolds numbers. In presence of an inert gas, there is an additional mass transfer resistance in the gas phase near the liquid gas-interface. This mass transfer resistance is inversely proportional to the gas Reynolds number, and this latter value is proportional to the liquid Reynolds number. The increase of the heat transfer coefficient is then due to a decrease of the mass transfer resistance in the gas phase.
The data will be used for the development of a predictive model, both the Him model and the condensation curve method will be applied.