Mothballs

It’s hardly an appealing thought, but the overpowering fragrance of mothballs in a large wind tunnel could provide the key to improving air quality in towns and cities.

Researchers at the University of Reading, in collaboration with EnFlo, based at the University of Surrey, are developing a series of tests that will help them understand how pollution and heat behave at street level so that more effective ventilation methods can be developed.

In towns and cities, pollution and heat released below building height (e.g. from cars and buildings) can be trapped at street level until ventilated to the air above. This can cause pollution ‘hotspots’ which affect sufferers from respiratory diseases such as asthma. It can also contribute to an uncomfortably warm urban climate.

The new research will focus on the ventilation process. This process depends on street layout, wind speed and other factors, and understanding it is vital to taking effective action to improve urban climate and air quality.

The project will centre on wind tunnel tests that simulate airflow in urban areas. Cube and bar shapes representing a variety of urban settings will be placed in a wind tunnel and covered in naphthalene (an aromatic hydrocarbon used in mothballs), which is carried by airflow in a similar way to heat and pollution.

By measuring the net loss of naphthalene after air has flowed over it, the rate of ventilation for the airflow and urban layout under examination can be calculated.

Interpretation of the results, which will require expertise in fluid dynamics, turbulence, heat transfer and meteorology, will enable the impact of different factors on ventilation to be assessed. An innovative feature of the research will involve the use of sensors to detect naphthalene concentrations.

Deploying the sensors successfully will require trial and error, but will ultimately enable the extent and duration of ‘hotspots’ to be determined.

The project team has already found that ventilation depends on street width, building height and the precise location of the pollution or heat source.

Dr. Janet Barlow, who is leading the team at the University of Reading’s Department of Meteorology, said: ‘Better understanding of heat and pollution ventilation rates will help inform the decision-making of architects and town planners. This should help to promote more sustainable, more comfortable and healthier urban environments.’

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