Heat transfer and pressure drop of regenerative air pre-heater elements.

Abstract

In the present study the thermal and hydraulic performance of heating plates used in regenerative air pre-heater was investigated. Experimental results on new heating surfaces are presented as well as preliminary investigations into plates er.',led by fly ash in the flue gas. In the uneroded state, 12 different plate profile designs were tested. These new packs were tested in different configurations, i.e. with and without braces around the individual plates and with different numbers of plates per plate pack. For some designs the individuality of the packs (repeatability of manufacture) was investigated. In order to establish the accuracy of the test facility, a pack of flat plates was tested and compared with literature results. It is shown that the profile designs with the smallest profile heights have the highest heat transfer coefficient, but also the highest pressure drop. Good performance in one parameter always means bad performance in another parameter. Heat transfer coefficients and pressure drops of the various pack designs are in approximately inversely proportion to the hydraulic diameter. Profiles with a flat counterplate have a lower heat transfer coefficient than profiles with an undulated counterplate. One eroded pack (with 20%, 30% and 40% mass loss) was tested and compared with an uneroded one in terms of heat transfer and pressure drop behaviour. Pressure drop was approximately 15% lower for the eroded plates (irrespective of the extent of erosion) and heat transfer coefficient was essentially unaffected.