Climatic analysis of a passive cooling technology for the built environment in hot countries

Abstract

The aim of this work was to determine the ventilation and cooling potential of a passive cooling windcatcher operating under hot climatic conditions by replicating the monthly wind velocity, wind direction, temperature and relative humidity (RH) observed in a hot-desert city. The city of Ras-Al-Khaimah (RAK), UAE was used as the location of the case-study and available climatic data was used as inlet boundary conditions for the numerical analysis. The study employed the CFD code FLUENT 14.5 with the standard k-model to conduct the steady-state RANS simulation. The windcatcher model was incorporated to a 3 x 3 x 3 m 3 test room model, which was identical to the one used in the field test. Unlike most numerical simulation of windcatchers, the work will simulate wind flows found in sub-urban environment. The numerical model provided detailed analysis of the pressure, airflow and temperature distributions inside the windcatcher and test room model. Temperature and velocity profiles indicated an induced, cooler airflow inside the room; outside air was cooled from 38˚C to 26-28˚C, while the average induced airflow speed was 0.59 m/s (15% lower compared to a windcatcher w/out heat pipes). Field testing measurements were carried out in the Jazira Hamra area of RAK during the month of September. The test demonstrated the positive effect of the integration of heat pipes on the cooling performance but also highlighted several issues. The comparison between the measured and predicted supply temperatures were in good agreement, with an average error of 3.15%.

Performance control of a spray passive down-draft evaporative cooling system

“…The study found that the new system can lower the supply air in the range from 10°C to 20°C. Calautit et al [32] undertook a CFD study to see the ventilation and cooling potential in a hot climate in the United Arab Emirates. An experiment was also done and the results of the experiment showed both a positive cooling effect and some issues in the indoor thermal environment for certain periods.…”

“…The literature review showed that a few studies investigated how the cool humid supply air that a spray PDEC system discharges affect the indoor thermal environment [5,12,[19][20][21]26,28,32]. The majority of the building applications using PDEC technology operated with no performance control, or applied a simple on-off control, rather than immediately responding to the variable cooling loads [5,12,20,22].…”

Practical natural ventilation performance metric based on thermal autonomy for sustainable building design

“…For example, the effective area sufficient for windows or vents should be determined and the driving force sufficient to move the ventilated air should be designed to ensure design flexibilities at the later stage when the detailed natural ventilation design is performed. Natural ventilation should be implemented considering other passive heating or cooling designs [27] as well as advanced HVAC operations [28]. Even a complex facility integrating daylighting and natural ventilation functions may be installed [29].…”

Investigation of Airflow Patterns in a New Design of Wind Tower with a Wetted Surface

“…The blockage ratio is defined as the cross-sectional area of the tower in the domain area. This parameter must be small enough to avoid the blockage effect, and we determine that the blockage ratio is around 3.3% which is considered acceptable for the simulations [43,44]. …”

“…Steady-state three-dimensional CFD simulations are performed with a standard k-ε turbulence model, following previous studies on wind towers [1,[43][44][45][46][47][48][49]. It is possible to predict the natural ventilation airflows inside and around wind towers and also indoor airflows with this approach.…”