РАЦІОНАЛЬНІ МЕТОДИ ІНТЕНСИФІКАЦІЇ ТЕПЛООБМІНУ В ГАЗОТРУБНИХ КОТЛАХ

Abstract

In the paper, the study of the effectiveness of heat exchange intensification in the gas-tube heat exchanger of a water-heating boiler was carried out, a comparative analysis of the results was carried out. It is shown that for heat pump gas boilers the problem of heat transfer intensification is especially important, since the temperature of the exhaust gases and the efficiency coefficient depend on the heat transfer intensity in the heat exchanger. The review of literary information has shown that in modern gas-tube boilers the intensifiers are mainly used in the form of spiral wiring inserts, twisted around the axis of metal plates, ring or spiral coil, extrusion of different shapes, which allows to destroy the boundary layer and turbulize the surface layers gas flow. As part of the course design, a heat generator design for 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. The influence of geometrical parameters of the intensifier on the coefficient of heat transfer from the gases, the temperature of the flue gases at the outlet from the boiler and on the growth of the hydraulic resistance in the gas tube heat exchanger have been investigated. It is shown that the convective coefficient of heat transfer after the establishment of intensifiers is increased in 1,7 ... 2,94 times with the growth of pressure losses in 2,24 ... 3,11 times compared with the option without intensification of heat exchange, while the efficiency of the boiler increased by 10,8 - 13 %. It is noted that when choosing a method for intensifying the heat exchange in a boiler for solid fuel and parameters of the 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.