Modelling of cooling tower splash pack

Dreyer, Andre Alexis (1994)

Dissertation (Ph. D.) -- University of Stellenbosch, 1994.

Thesis

AFRIKAANSE OPSOMMING: 'n Wiskundige model en 'n rekenaar simulasie program is ontwikkel om die vertoning van teenvloei koeltoring spat-pakking ("splash pack") te voorspel. Die een-dimensionele model gebruik basiese lugdinamiese, hidrodinamiese en warmte/massa-oordrag data om die vertoning te voorspel sander om van gemete koeltoring toetsdata gebruik te maak. Sekere basiese eksperimentele werk is gedoen om die volgende aspekte meer duidelik te maak: die massa water wat spat vanaf die nat latte, die grootte-verdeling van die spat druppels en die grootte-verdeling van die druppels wat afdrup vanaf die latte. Toetse is ook gedoen op twaalf verskillende pakkings om verwysingsdata te genereer waarteen die akkuraatheid van die simulasie-program getoets kon word. Die gemete oordrags-karakteristieke en drukval data is vergelyk met die voorspelde data wat met die program gegenereer is. Daar is gevind data die model die korrekte tendense in drukval en oordrags-karakteristieke voorspel. Die program het die oordrags-karakteristieke en die drukval oor die pakking oor-voorspel en moontlike redes hiervoor word bespreek. Die simulasie program is gebruik om ontwerpsriglyne te genereer vir die optimum pakkingsmateriaal uitleg. Met behulp van die program was dit ook moontlik om die effek van verlaagde oppervlakspanning (en gevolglik kleiner druppels) op die termiese vertoning van pakkingsmateriaal te ondersoek. Verskeie voorstelle vir verdere werk word gemaak.

ENGLISH ABSTRACT: A mathematical model and a computer simulation program have been developed for the modelling of counterflow cooling tower splash pack thermal performance. The onedimensional model uses basic aerodynamic, hydrodynamic and heat/mass transfer information to predict the performance of the splash pack without depending on cooling tower test data. Some basic experimental work has been done to clarify aspects such as the volume of water splashing from the grids, the size distribution of splash drops and the size distribution of the drops dripping from the lower edges of the slats. Tests were also performed on twelve different splash packs to generate reference data against which the simulation program could be verified. The predicted transfer characteristics and pressure drop data obtained with the simulation program are compared to experimental data. It has been found that the model predicts the correct trends for both the transfer characteristics and the pressure drop across the packing. Quantitatively the simulation program was found to over-predict the transfer characteristics and the pressure drop across the packing. Possible reasons for the differences are discussed. The program was used to obtain rough guidelines for optimum splash pack layout. The program was also employed to study the effect of reduced surface tension (resulting in smaller drops) on the thermal performance of splash pack. A number of recommendations for further research are made.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/58460
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