Pipe direct contact heat exchange

Almost all feedstocks of interest have such properties that they do not flow readily through cither pipes or shell of a conventional heat exchanger without distribution problems. Afler a number of alternatives had been considered it was concluded that the most adequate way of preheating is direct injection of hot water. In Fig. 3 this is done in vessel V where a stream of hot recycle water is mixed with the feed. A special way of contacting achieves efficient heat and mass transfer. It has been verified in our experiments that at 200-250°C biomass feedstocks of different origin, including wood chips, arc softened and form a pastc-like substance [7,8]. The... 

Heat pipe tubes The absorbed heat is transferred by using the heat pipe principle without direct contact to the heat transfer fluid of the solar loop. In this case, there are two different ways of connection (1) the dry connection, where the heat has to be transferred from the condenser through the material of the header tube. This way the installation and removal of the tubes is much easier than with direct flow pipes brazed to the header. On the other hand, heat-conductive paste often has to be used, thus requiring that the pipes be installed professionally and (2) the wet connection, where the fluid of the solar loop directly flows around the condenser of the heat pipes. In this case, no heat-conductive paste is needed, but the exchange of tubes is more difficult. 

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