4 replies to this topic

[rahul210807]

Hi everyone, i'm doing a project which includes the passage of a material inside a tunnel. The diameter of the tunnel is 10 meters and the tunnel is a RCC (reinforced cement concrete) tunnel of 5kms length. The air density has to be increased to 100 kg/meter cube. And the flow rate is 70km/hr. So could anyone provide the calculations or suggest how much power is required to run the compressor.

[kkala]

Can you please check mentioned air density of 100 kg/m3, or give explanations? Atmospheric air at usual ambient temperatures has density around 1.2 kg/m3; assuming nearly isothermal flow, 100 kg/m3 would correspond to ~83 Atma.
Besides 70 km/h (=19.44 m/s) seems to concern air velocity, with corresponding flow rate 19.44*π*10^2/4=1527 m3/s.
This velocity is common for air; tunnel will cause a small ΔP, probably around 0.2 Atm. Assuming atmospheric pressure at the end of the tunnel, pressure at discharge of the compressor (I imagine fans) would be around 0.2 Atm g.
Please confirm or explain otherwise, to clarify the case.

[rahul210807]

Can you please check mentioned air density of 100 kg/m3, or give explanations? Atmospheric air at usual ambient temperatures has density around 1.2 kg/m3; assuming nearly isothermal flow, 100 kg/m3 would correspond to ~83 Atma.
Besides 70 km/h (=19.44 m/s) seems to concern air velocity, with corresponding flow rate 19.44*π*10^2/4=1527 m3/s.
This velocity is common for air; tunnel will cause a small ΔP, probably around 0.2 Atm. Assuming atmospheric pressure at the end of the tunnel, pressure at discharge of the compressor (I imagine fans) would be around 0.2 Atm g.
Please confirm or explain otherwise, to clarify the case.

Thank you so much, Yes, according to my requirement i need an air density of 100kg/m3

[kkala]

Assumptions of post No 2 are mentioned in the attached "tunnel.doc", whose results does not comply with 100 kg/m3 air density, apparently at compressor / fan discharge. Can rahul210807 give more explanations? If air flows along the tunnel at 70 km/h and exits to atmosphere, pressure at the beginning of tunnel will be ~ 0.018 kgf/cm2 above atmospheric; and air density would be only 1.7% higher than atmospheric (~1.2 kg/m3). Understanding may be missing something though, what is the "passage of a material inside a tunnel"? Does the "material" differ to air?

Attached Files

•  tunnel.doc   26KB   20 downloads

[Shivshankar]

Hi

See if atatched file helps.

Regards
Shivshankar

Attached Files

•  Chapter 3.3 Compressed Air System.pdf   496.67KB   43 downloads
•  3.3_Compressed_air_system.pdf   112.23KB   30 downloads