Підвищення енергоефективності водогрійних котлів за допомогою інтенсифікації теплообміну

Abstract

In the work the research of the efficiency of the heat exchange intensification in the gas-tube heat exchanger of the water heating boiler was carried out, the analysis of the obtained results was carried out. It was noted that for heat pump gas boilers the problem of heat transfer intensification is especially important, since the coefficient of heat transfer from gases to the wall in the channels without intensification is rather small, and the temperature of the waste gases and the efficiency coefficient depend on the heat transfer intensity of the heat exchanger. The review of literary information, which showed that in modern water-heating boilers of small and medium power intensifiers are used: wired inserts of various configurations, ring grooves, spiral inserts, band swirls, screw turbulators, plates of different configurations, combined methods. As part of the course design, the design of a heat generator on wood chips with a rated power of 550 kW was developed. For this design, numerical studies of the influence of the installation of intensifiers on the performance of the boiler on the full and partial load are carried out. To study the boiler's energy characteristics, a mathematical model has been developed, which is supplemented with dependencies for the calculation of the intensified heat transfer in the boiler heat exchanger. Influence of installation of the intensifier on the temperature of flue gases at the output from the boiler and on the efficiency coefficient is investigated. It is shown that the greatest reduction of the temperature of the exhaust gases is observed for the intensifier in the form of a twisted tape, a combined method, an intensifier of the original construction and a bent plate with different geometric parameters. It is noted that when choosing a method for intensifying heat exchange in a boiler for solid fuels and parameters of intensifiers, it is necessary to carry out a detailed thermal and aerodynamic calculation when changing the boiler's thermal power and to estimate the ranges of rational work, which will exclude significant cooling of flue gases, and the effect of installing the intensifiers will exceed the cost of overcoming the additional hydraulic resistance in the heat exchanger.