Condensation Heat Transfer Of Steam In The Presence Of High Content Non-condensable Gas Outside Of A Horizontal Three-dimensional Finned Tube

Condensation of steam in the presence of non-condensable gas is an important heat transfer mode in the petroleum, chemical engineering, electric power, refrigeration industry. But the heat transfer efficiency of the heat exchanger will be reduced deeply due to the existence of the non-condensable gas, especially in the process of biomass pyrogenation and liquefaction. Such how to condensate the mixture gas which is composed by the biofuel vapor and non-condensable gas rapidly and efficiently becomes the key point for the application of the technology of biomass pyrolysis liquefaction in the engineering. This makes the understanding for the mechanism of enhanced condensation heat transfer of steam in the presence of high content non-condensable gas more important either for the theory or for the application. In the past decades, little efforts has been done on the investigation of condensation of steam in the presence of high content non-condensable gas due to its complication.Additionally, no papers are reported on the condensation of steam in the presence of non-condensable gas on the surface of the tube with three dimensional fins. In this paper, the experimental apparatus was designed and set up for the condensation heat transfer outside the tube in the space. The experiments on condensation heat transfer of steam-air mixture gas on a horizontal three-dimensional finned tube and a smooth tube were carried out within an experimental range of 0.18~0.69 in the non-condensable gas mass. Then, the correlation of condensation heat transfer coefficient for the horizontal three-dimensional finned tube was established based on the experimental data. A two dimensional analytical model for the condensation of steam in the presence of non-condensable gas was proposed based on the mass, momentum and energy conservation equations of condensing mixture flow and Nusselt's theory. The simulation results were compared with the experimental data and the effects of the parameters such as the content of non-condensable gas , wall subcooling , and the geometry of the finned tube on the performance of the condensation heat transfer were analyzed respectively. Furthermore, the thermogravimetric experiments, which were the preparation for the biomass pyrogenation, were carried out for seven kinds of biomass in Chongqing, corn stalk, corn cob, broomcorn stalk, rice straw, wheat straw, Huangjue tree and bamboo by the thermogravimetric analyzer. The remarkably conclusions are drawn as follows:1. The experimental results showed that the condensation heat transfer coefficient of the three-dimensional finned tube is 0.7 to 1.9 times larger than that of the smooth tube at a specific operation condition. At the fixed wall subcooling, both the condensation heat transfer coefficient of the three-dimensional finned tube and the...