ENHANCEMENT OF THERMAL AND HYDRAULIC CHARACTERISTICS OF RECUPERATIVE HEAT EXCHANGERS WITH SECONDARY EMITTERS

Abstract

In frame of the presented work the results of comparative experimental investigations carried out on heat transfer and fluid dynamics processes within high temperature recuperators of the authors’ and alternative designs are discussed. The researches were fulfilled at firing rig with a purpose of comparison the characteristics of the test sections of smooth tube recuperator (BD) and the specimens with the facilities of different geometry providing heat transfer intensification: 1) the designs SP with the spiral inserts installed by the whole length of heat exchange tubes with the relative pitch of the spirals s/d = 4,0. These recuperators meet the existing foreign analogous prototypes; 2) design MD of authors’ design with flexible cross-shaped inserts – the secondary emitters installed by the whole length of heat-exchange tubes. The heat engineering and combined heat and hydraulic advantages of proposed recuperators of MD type in comparison with the foreign designs with the spiral inserts – turbulators and with traditional native smooth-tube recuperators (BD) have been identified. It has been stated that especially appreciable results of the tests make the advantages of MD design regarding the most representative temperature criterion – temperature difference ΔT w-a between the tube walls and of an air flow. This value for authors’ design is decreased approximately 4 times in comparison with BD design and more than 2 times lower in comparison with that for foreign designs SP.