SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS Theoretical modeling and experimental verification of a passive downdraught evaporative cooling tower Stellenbosch University Energy Postgraduate Conference 2013

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 2 Introduction HVAC accounts for substantial amount of energy use in buildings (4000 gWh annually in S.A.) Greenhouse gases (GHG) emissions from HVAC account for up to 22% of total GHG emissions. Reducing the total HVAC load would result in a reduction in operating costs, GHG emissions and related environmental impacts MotivationIntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 3 Adequate ventilation for buildings is needed Air-conditioning and mechanical ventilation expensive running cost Natural ventilation cheap or with no running cost PDEC (Passive Downdraught Evaporative Cooling) efficient method of passive cooling in arid regions Design Strategies include: CFD Empirical Methods 2D Axisymmetric Theoretical Model Motivation IntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 4 PDEC Principle Psychrometric Chart MotivationIntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 5 PDEC Principle MotivationIntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 6 PDEC in practice MotivationIntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 7 2D Model of PDEC MotivationIntroductionPDEC2D ModelCFDConclusion Control Volume Grid

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 8 2D Model of PDEC Conservation of Mass Mass diffusion Conservation of energy Conservation of momentum MotivationIntroductionPDEC2D ModelCFDConclusion

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 9 CFD Model of PDEC Transport Equations where  may be 1 (continuity) velocity components u, v turbulent kinetic energy k turbulent dissipation rate  temperature water vapour concentration Change = Convection + Diffusion + Source In the air MotivationIntroductionPDEC2D ModelCFDConclusion The standard solver can be customized to meet the requirements unique to a particular application by using the user-defined functions

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 10 CFD Model of PDEC MotivationIntroductionPDEC2D ModelCFDConclusion PDEC laminar flow in room

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 11 Conclusions MotivationIntroductionPDEC2D ModelCFDConclusion Important to understand the fundamentals of the down- draft evaporative cooling PDEC tower can’t maintain a constant performance due to a strong climatic dependency PDEC towers may not be suitable to humid climates without significant advancement CFD tools have been extensively used to simulate flow and thermal fields for a variety of applications. Climatic data with Theoretical models could benefit the design and implementation of PDEC towers

SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, Aug 2013 iThemba LABS 12 Thank you