A passive cooling wind catcher with heat pipe technology: CFD, wind tunnel and field-test analysis

Wind catchers are natural ventilation systems based on the design of traditional architecture, intended to provide ventilation by manipulating pressure differentials around buildings induced by wind movement and temperature difference. Though the movement of air caused by the wind catcher will lead to a cooling sensation for occupants, the high air temperature in hot regions will result in little cooling to occupants. In order to maximise the properties of cooling by wind catchers, heat pipes were incorporated into the design. Computational Fluid Dynamics (CFD) was used to investigate the effect of the cooling devices on the performance of the wind catcher, highlighting the capabilities of the system to deliver the required fresh air rates and cool the ventilated space. Qualitative and quantitative wind tunnel measurements of the airflow through the wind catcher were compared with the CFD data and good correlation was observed. Preliminary field testing of the wind catcher was carried out to evaluate its thermal performance under real operating conditions. A cooling potential of up to 12 °C of supply air temperature was identified in this study

Thermal comfort and indoor air quality analysis of a low-energy cooling windcatcher

The aim of this work was to investigate the performance of a roof-mounted cooling windcatcher integrated with heat pipes using Computational Fluid Dynamics (CFD) and field test analysis. The windcatcher model was incorporated to a 5m x 5m x3 m test room model. The study employed the CFD code FLUENT 15 with the standard k-ɛ model to conduct the steady-state RANS simulation. The numerical model provided detailed analysis of the airflow and temperature distribution inside the test room. The CO2 concentration analysis showed that the system was capable of delivering fresh air inside the space and lowering the CO2 levels. The thermal comfort was calculated using the Predicted Mean Vote (PMV) method. The PMV values ranged between +0.48 to +0.99 and the average was +0.85 (slightly warm). Field test measurements were carried out in the Ras-Al-Khaimah (RAK), UAE during the month of September. Numerical model was validated using experimental data and good agreement was observed between both methods of analysis

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

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–ε model to conduct the steady-state RANS simulation. The windcatcher model was incorporated to a 3 × 3 × 3 m3 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%

Climatic analysis of ventilation and thermal performance of a dome building with roof vent

This paper presents a climatic analysis of a naturally ventilated geodesic-type dome building situated in a hot climate. A comprehensive review of the literature was conducted to provide an overview of previous related research on dome-type-roof buildings. The two-floor geodesic dome building assessed in this study was based on a 3V icosahedron type and had a roof vent for natural ventilation. The airflow and temperature distributions inside the building were simulated using computational fluid dynamics modelling with the standard k-d turbulence model. The computational modelling was verified using sensitivity analysis and flux balance analysis. Validation was carried out by using a similar dome-shaped building model from the literature. The atmospheric boundary layer flow was simulated in the computational domain for a more realistic prediction of wind conditions. The thermal comfort level was assessed using the predicted mean vote method. The results showed that the integration of the roof vents was advantageous and could reduce the indoor temperature and introduce fresh air, particularly during winter. The results also revealed that natural ventilation using roof vents could not satisfy the thermal requirements during summer periods, and potential cooling solutions that could be integrated into the system are discussed

Sustainable buildings: opportunities, challenges, aims and vision

In recent years, a large and rapidly growing body of research in the built environment has involved multi disciplinary collaboration, a trend driven by the increased funding for multi-disciplinary projects and research institutes, along with the challenges and opportunities detailed previously. There is therefore more scope for disseminating the research output of these initiatives in a focused, effective and multi-disciplinary journal. Sustain able Buildings intends to fulfil this role and serve the diverse international community of engineers, architects, urban physicists, urban designers, researchers, scientists and industry professionals, providing a forum where each can communicate their original and innovative findings and provide motivation and direction towards meeting the current and future challenges of sustainable buildings. The journal will focus on advancing the knowledge on the forum of the global sustainability practices and to stimulate the exploration and innovations aimed at creating a climate resilient built environment that reduces energy consumption and environmental deterioration and creates high quality indoor environment

Computational Analysis of Natural Ventilation Flows in Geodesic Dome Building in Hot Climates

For centuries, dome roofs were used in traditional houses in hot regions such as the Middle East and Mediterranean basin due to its thermal advantages, structural benefits and availability of construction materials. This article presents the computational modelling of the wind- and buoyancy-induced ventilation in a geodesic dome building in a hot climate. The airflow and temperature distributions and ventilation flow rates were predicted using Computational Fluid Dynamics (CFD). The three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations were solved using the CFD tool ANSYS FLUENT15. The standard k-epsilon was used as turbulence model. The modelling was verified using grid sensitivity and flux balance analysis. In order to validate the modelling method used in the current study, additional simulation of a similar domed-roof building was conducted for comparison. For wind-induced ventilation, the dome building was modelled with upper roof vents. For buoyancy-induced ventilation, the geometry was modelled with roof vents and also with two windows open in the lower level. The results showed that using the upper roof openings as a natural ventilation strategy during winter periods is advantageous and could reduce the indoor temperature and also introduce fresh air. The results also revealed that natural ventilation using roof vents cannot satisfy thermal requirements during hot summer periods and complementary cooling solutions should be considered. The analysis showed that buoyancy-induced ventilation model can still generate air movement inside the building during periods with no or very low wind

CFD and experimental data of closed-loop wind tunnel flow

The data presented in this article were the basis for the study reported in the research articles entitled ‘A validated design methodology for a closed loop subsonic wind tunnel’ [1], which presented a systematic investigation into the design, simulation and analysis of flow parameters in a wind tunnel using Computational Fluid Dynamics (CFD). The authors evaluated the accuracy of replicating the flow characteristics for which the wind tunnel was designed using numerical simulation. Here, we detail the numerical and experimental set-up for the analysis of the closed-loop subsonic wind tunnel with an empty test section

A review of numerical modelling of multi-scale wind turbines and their environment

Global demand for energy continues to increase rapidly, due to economic and population growth, especially for increasing market economies. These lead to challenges and worries about energy security that can increase as more users need more energy resources. Also, higher consumption of fossil fuels leads to more greenhouse gas emissions, which contribute to global warming. Moreover, there are still more people without access to electricity. Several studies have reported that one of the rapidly developing source of power is wind energy and with declining costs due to technology and manufacturing advancements and concerns over energy security and environmental issues, the trend is predicted to continue. As a result, tools and methods to simulate and optimize wind energy technologies must also continue to advance. This paper reviews the most recently published works in Computational Fluid Dynamic (CFD) simulations of micro to small wind turbines, building integrated with wind turbines, and wind turbines installed in wind farms. In addition, the existing limitations and complications included with the wind energy system modelling were examined and issues that needs further work are highlighted. This study investigated the current development of CFD modelling of wind energy systems. Studies on aerodynamic interaction among the atmospheric boundary layer or wind farm terrain and the turbine rotor and their wakes were investigated. Furthermore, CFD combined with other tools such as blade element momentum were examined

Determining the optimum spacing and arrangement for commercial wind towers for ventilation performance

CFD analysis of multiple wind towers located on the same building was performed following validation of a benchmark model against wind tunnel data. The positioning of the wind towers was varied in six different cases, two different arrangements with three different spacing lengths between wind towers. All analysis was compared against the benchmark (isolated) wind tower. The ability of the wind towers, particularly the leeward wind tower, to ventilate the space below was determined for a set occupancy against current guidelines for air supply rates. Furthermore, the effect of the spacing and arrangement on CO2 concentration within rooms ventilated by the leeward wind tower was investigated (re-entry of exhaust air pollutants into fresh supply). It was found that a parallel arrangement of wind towers was not effective for ventilating an occupied volume, regardless of the spacing between the two wind towers when incident wind direction was parallel to the arrangement. The maximum supply rate for the leeward wind tower in parallel arrangement at a spacing of 5 m was just over 50% of the regulation rate (10 L/s/occupant) and 40% of the supply rate of an isolated wind tower. Decreasing the spacing between the parallel wind towers to 3 m further reduces the supply rate to 2.4 L/s/occupant and the device was observed to be operating in reverse (airflow entering from leeward opening). As the angle of wind increased, an improvement of air supply rates was seen. For a staggered arrangement of wind towers, the leeward wind tower was capable of supplying the recommended ventilation rates at all tested spacing lengths. The average indoor CO2 concentration of the space with the leeward wind tower was higher in the parallel arrangement than the staggered arrangement at 0° wind angle. For the parallel arrangement, the average CO2 concentration was 28–50 ppm higher than the outdoor air. The staggered arrangement effectively minimised the re-entry of pollutants, with the indoor CO2 concentration 1–3 ppm higher than the outdoor

Effect of Rotation Speed of a Rotary Wheel on Ventilation Supply Rates of Wind Tower System

This study explores the integration of a rotary thermal wheel into a wind tower system, specifically the effect of the rotation speed on the ventilation rate and heat recovery. Wind towers are capable of supplying recommended levels of supply air under a range of external conditions, integrating a rotary thermal wheel will cause a reduction in the air supply rates due to the blockage created by the wheel. Using Computational Fluid Dynamics (CFD) analysis, the air supply rate and heat transfer of the rotary thermal wheel have been calculated for a range of rotation speeds between 0rpm – 500rpm. The recommended air supply rate of 8l/s/p is attained up to a rotation speed of 50rpm; beyond this rotation speed the air supply rate is too low. The maximum temperature recovered across the rotary thermal wheel is measured as 1.77°C at a rotation speed of 20rpm. Using the two results gained from the analysis, an optimum operating range of the rotary thermal wheel can be determined between 5rpm and 20rpm. The technology presented here is subject to an international patent application (PCT/GB2014/052513)