Vacuum Inside The Boiler Flow And Heat Transfer Characteristics Of The Test And Applied Research

The boilers used for heating are energy-consuming devices. Most boilers for heating in China are running under bad conditions—feed-water is in poor quality, which causes a large amount of energy wasting. Since 1980's, a new type of boiler— vacuum-boiler has been widely applied in Japan due to the advantages of safety and energy saving. This type of boiler is rapidly developed in China and partly taking the place of the ordinary heating boilers presently.The researches and developments of vacuum-boiler are reviewed in detail in this paper. The hydrodynamics and heat transfer characteristics of the vacuum-boiler are analyzed, and a sample machine of 0.7MW was also designed and being manufactured on the basis of the investigations.A program in programming language of the VC++ for series of the vacuum-boiler designing which is easy for use is brought forward based on the thermal and hydrodynamic analysis. And some techniques for heat transfer enhancement in the vacuum-boiler are also proposed in this paper.The flow and heat transfer characteristics of the water-steam system in the vacuum-boiler were studied experimentally with an experimental setup. Different kinds of additives, which may enhance the condensation heat transfer coefficients, were also investigated with different concentrations during the experiments. The non-condensable gas such as air plays an important role in preventing heat transfer in vacuum-boilers that causes the condensation coefficient to drop sharply. Many improvements and valuable results for the designing and developing of the vacuum-boilers are obtained in this paper.