Temperature from Data logger placed along track 1

Glossary of terms

Chapter 5. Air Flow and Temperature Measurement

5.4 Portable Air Flow Measurements

5.5.2 Temperature from Data logger placed along track 1

Figure 39: Location of instruments at Jesmond, Haymarket, Monument and Central Station and Tunnel geometry

5.5.2 Temperature from Data logger placed along track 1

The following section presents the results from the data logger measurements. An overview of all the data is presented in Figure 40 and Figure 41 which also show the local external weather temperature. Following the temperatures in the south to north direction in the direction of the background airflow the first measurement was taken at the tunnel portal at the Central Station (purple line). Comparing track 1 and 2 with the weather temperature (black line) in Figure 40 and Figure 41 it can be seen that the temperature during the day time was higher than at night and the temperature trend indicates a strong correlation with the external environmental weather temperature but the tunnel temperature was more stable showing less variability. The temperature at the Central station south of platform 1 was up to 4^oC higher than the weather temperature (black line) as shown in Figure 40. In the operational time there were

significant temperature variations which was the effect of the air flow constantly reversing due to the piston effect of the trains entering the station from the north.

On the other track (Figure 41) the temperature is very close to the weather temperature.

During the daytime the temperature was even lower than the weather temperature.

There was a 2^oC to 3^oC temperature difference between track 1 and 2 at the Central station which may be caused by local geography outside the tunnel entrance.

Figure 40: The temperature graph of loggers placed at track 1 with local weather

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Temperature (oC)

Tunnel temperature (Track1)

Jesmond Platform 1 South T (oC) Haymarket Platform 1 North T (oC) Haymarket Platform 1 South T (oC) Monument Platform 1 North T (oC) Monument Platform 1 South T (oC) Central station Platform 1 North T (oC) Central station Platform 1 South T (oC) Weather data

Figure 41: The temperature graph of loggers placed at track 2 with local weather For a better comparison of the temperature variations between the stations in each tunnel, the data has been broken down to consider individual stations as shown in Figure 42 to Figure 49. In both tunnels the air temperature increased by around 2^oC as it passed through the Central station and around a further 1^oC as it passed through the tunnel to the south of the Monument station.

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Temperature (oC)

Tunnel temperature (Track2)

Jesmond Platform 2 North T (oC) Jesmond Platform 2 South T (oC) Haymarket Platform 2 North T (oC) Haymarket Platform 2 South T (oC) Monument Platform 2 North T (oC) Monument Platform 2 South T (oC) Central station Platform 2 North T (oC) Central station Platform 2 South T (oC)

Figure 42: The logger temperatures at track 1 (Each side of the Central Station and south of Monument station)

Figure 43: The logger temperatures at track 2 (Each side of the central station and south of Monument station)

The temperature at track 1 dropped by 1ôC to 2ôC and track 2 raised by around 1ôC as the air passed through the Monument station. There was a 3ôC difference between the temperature entering the Monument station at platform 1 and that at the north end of platform 2 as shown by the yellow line in Figure 44 and Figure 45. The airflow appears to have mixed better in this station than in the other underground stations because of

Tunnel temperature from Central station to Monument (Track1)

Tunnel temperature from Central station to Monument (Track 2)

the connection corridors between the two platforms. This station was originally constructed for the largest pedestrian volume as the main station in the city centre.

The tunnel temperatures at the Monument station for both track 1 and 2 are shown in Figure 46. It can be seen that the air temperature leaving the station at the north of the platforms is very close and in the middle of the temperature range of the south platform.

The temperature fluctuation is miniscule from the North Monument station to Haymarket station and the temperatures of both tracks were very similar.

Figure 44: The logger temperatures at track 1 (Each side of the Monument station and south of Haymarket Station)

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Temperature (oC)

Tunnel temperature from Monument to Haymarket (Track1)

Figure 45: The logger temperatures at track 2 (Each side of the Monument station and south of Haymarket station)

Figure 46: The logger temperatures at the Monument station for both track 1 and 2 The temperature entering the Haymarket station was around 13ôC (dark green line) at both tracks as shown in Figure 47 and Figure 48. The temperature was raised 1ôC at the north of the Haymarket station on platform 2, but the temperature at the north of the Haymarket station on platform 1 dropped 2ôC to 3ôC due to the presence of a relief

Tunnel temperature from Monument to Haymarket (Track 2)

Tunnel temperature at Monument station (Track 1 and 2)

Monument Platform 1 South T (oC) Monument Platform 1 North T (oC) Monument Platform 2 South T (oC) Monument Platform 2 North T (oC)

shaft north of Haymarket platform 1 that allowed cool air to enter the tunnel. This is shown in Figure 40.

Figure 47: The logger temperatures at track 1 (Each side of the Haymarket Station and south of Jesmond Station)

Figure 48: The logger temperatures at track 2 (Each side of the Haymarket station and south of Jesmond station)

Tunnel temperature from Haymarket and Jesmond station (Track1)

Tunnel temperature from Haymarket and Jesmond station (Track 2)

The measurements taken at Jesmond station located at the north end of the tunnel showed that the temperature was very close to the weather temperature as shown in Figure 49.

Figure 49: The logger temperatures at track 2 (Each side of the Jesmond station) 5.5.3 Summary of data logger measurement results

Temperature variations in the tunnel can be highly variable. They tend to follow the local ambient temperature but are highly affected by the heat generated within the system. The air temperature tended to increase as it flowed through the tunnels but was also affected by the varying airflow from ventilation shafts and draught relief shafts.

In this system, the ventilation shafts had less effect on the tunnel environment compare to the draught relief shaft as the ventilation fans had not been used since 2009. The temperature difference between the local external ambient temperature and the tunnel could up to 9^oC as measured at the Monument station platform 1 south at 9:00 on 21/02/2014. It is these temperature differences together with the tunnel geometry elevation that drives a stable background airflow in the tunnel.

Tunnel temperature at Jesmond station (Track2)

94 5.6 Conclusion

This chapter has presented, described and discussed the air flow and temperature variation inside the station, in the immediate environment outside the station and in the subway tunnels. The findings of a previous study that showed that the mechanical ventilation and gate operation have an immediate and substantial effect on the background air flow and temperature were discussed. Furthermore, very detailed and sensitive measurement were taken using portable instruments and correlations between the weather station data and external weather condition outside the station exits established. These station external condition are the key influencing factor to the air flow inside the station through the exits. This data has also have been used for modelling and validating the microclimate CFD modelling described in Chapter 7. The data measured using portable instrumentation inside the station has shown a very high variation and sensitivity of the air movement within the station leading to a better understanding about the air movements inside the station. In addition, this measurement have been very valuable complimenting data obtained from the ultrasonic anemometers permanently located in the subway especially during operational hours. Lastly, the temperature measurements in the entire tunnel shows the temperature differences between the tunnel and the local weather could be up to 9^oC. This has a strong influence on underground air currents as it is this differential that creates the chimney effect driving the air flow through the station which in turn strengthens and stabilises the airflows in the tunnel system.

In document Integrated evaluation of air flow and gas dispersion for underground station safety strategies based on subway climatology (Page 111-120)