Effect of water maldistribution on cooling tower fill performance evaluation

[摘要] ENGLISH ABSTRACT: A 1.5 x 1.5 m2 counter-flow fill performance test facility is described in detail.Instrumentation was selected and installed in the cooling tower fill test facility andcalibrated to ensure measurement accuracy. A facility control program was writtento simplify the operation of the test facility via a user interface. The programcalculates automatically the Merkel number and loss coefficients as measures offill thermal and flow performance respectively. A spray frame was designed andmanufactured to ensure uniform water distribution to the fill. The waterdistribution through different fills with varying fill heights and different waterflow rates was measured. The water attached to the walls of the test facility wasexamined.Film, trickle and splash fills are tested in the upgraded test facility. The film andtrickle fill performance determined during testing is deemed acceptable as thesefills have minimal migration effects. Fills with poor distribution effects and largemigration of water towards the walls of the test facility, like the splash fill tested,cannot to be tested accurately in a 1.5 x 1.5 m2 test section as the results do notrepresent the performance of the fill in a relatively large cooling tower.Other aspects examined were:• air flow uniformity• air fill bypass effects• location of water inlet and outlet temperature measurement points• location of pressure measurement probes.It was determined that, in the current test facility:• air uniformity is suitable for performance testing• air bypass effects can be ignored for open fills and can be minimised fordense fills by packing sponge between the fill and walls• water inlet and outlet temperatures should be measured in the pipe-work,resulting in a measurement method that is not influenced by the relativeweightings of each thermocouple• pressure difference over the fill height measured by the pressuremeasurement tap is independent of its location on the fill outlet planeprovided the pressure measurement points are perpendicular to the airstream and are not against the walls.

[发布机构] Stellenbosch University