A numerical investigation of the plenum chamber aerodynamic behaviour of mechanical draught air-cooled heat exchangers

Meyer, C. J. (Christiaan Johannes) (2000-12)

Thesis (Ph.D.)--University of Stellenbosch, 2000.

Thesis

ENGLISH ABSTRACT: The primary purpose of this dissertation is to further the understanding of the influence of plenum chamber aerodynamic behaviour on mechanical draught air-cooled heat exchanger (ACHE) performance. The investigation, which included both forced and induced draught ACHEs, was conducted through the use of a commercially available computational fluid dynamics (CFD) code. A numerical axial flow fan and heat exchanger model that simulates the effect of the axial flow fan and heat exchanger bundle respectively on the flow field within the ACHE was developed and included in the CFD-code through user-programming. Where appropriate the numerical investigation was augmented with experimental data. The plenum chamber aerodynamic behaviour is characterised and included in the draught equations associated with forced and induced draught ACHEs through the introduction of dimensionless plenum chamber recovery and plenum chamber loss coefficient respectively. The influence of changes made to a range of mechanical draught ACHEs on plenum chamber aerodynamic behaviour was investigated. These changes include: • Operating conditions of the axial flow fan. • The height of the plenum chamber in the fan axial direction. • The heat exchanger bundle isothermal flow resistance. • The fan to heat exchanger area ratio. • The axial position of the fan in the fan casing. From the results of the numerical investigation a set of design guidelines are set for both forced and induced draught ACHEs. The design guidelines include recommended values for the dimensionless plenum chamber recovery and plenum chamber loss coefficient to be used in the respective draught equations enabling a more accurate prediction of the operating point of a proposed mechanical draught ACHE. KEYWORDS: air-cooled heat exchanger numerical investigation plenum chamber aerodynamic behaviour

AFRIKAANSE OPSOMMING: Die primere doel van hierdie proefskrif is om die kennis aangaande die invloed van plenum ruimte lugdinamiese gedrag op die werking van meganiese-trek lugverkoelde warmteruilers (LVWRs) te verbreed. Die ondersoek wat geforseerde- asook geinduseerdetrek LVWRs ingesluit het is uitgevoer deur gebruik te maak van In kornmersiele verkrygbare berekeningsvloeimeganika-pakket. In Numeriese aksiaalwaaier- en warmteruilermodel wat die invloed van respektiewelik die aksiaalwaaier en die warmteruiler op die vloeiveld in die LVWR simuleer is ontwikkel en in die berekeningsvloeimeganika-pakket geinkorporeer d.m.v gebruikers-roetines. Waar van toepassing is die numeriese ondersoek aangevul met eksperimentele data. Die plenumruimte lugdinamiese gedrag word gekarakteriseer en ingesluit in die onderskeie trekvergelykings vir geforseerde- en geiduseerde-trek LVWRs deur die daarstelling van In dimensielose plenumruimteherwinnings- en plenumruimteverlieskoeffisient. Die invloed van veranderinge wat aangebring is aan In reeks meganiesetrek LVWRs op die plenumruimte lugdinamiese gedrag is ondersoek. Hierdie veranderinge sluit die volgende in: • Die werking van die aksiaalwaaier. • Die hoogte van die plenumruimte in die aksiale rigting van die waaier. • Die isotermiese lugweerstand van die warmteruiler. • Die waaier-tot-warmteruiler area-verhouding. • Die aksiale posisie van die aksiaalwaaier in die waaierring. In Stel ontwerpsriglyne Vir beide geforseerde- en geinduseerde-trek LVWRs word geformuleer gebaseer op die resultate van die numeriese ondersoek. Die ontwerpsriglyne sluit aanbevole waardes vir die dimensielose plenumruimte-herwinnings- en plenumruimteverlieskoeffisient in wat op hulle beurt aangewend kan word om In meer akkurate aanduiding van die werkspunt van In beplande LVWR te bereken deur gebruik te maak van die toepaslike trekvergelyking. SLEUTEL WQORDE: lugverkoelde warmteruiler numeriese ondersoek plenurnruimte, lugdinamiese gedrag

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/51616
This item appears in the following collections: