Problem 1.2 - Using two manometers to measure pressure drop and downstream pressure of compressed air flowing in a pipe

A Throttling Valve is often used to control the downstream pressure of a high pressure fluid (such as steam or air) flowing in a pipe. In the following diagram we have a water manometer to measure the pressure drop ΔP caused by the throttling valve as well as a mercury manometer to measure the downstream pressure of the air.

If the height difference in the water manometer h_w is 150 cm, and that in the mercury manometer h_Hg is 225 cm, determine a) the pressure difference ΔP [14.7 kPa] and b) the downstream absolute pressure of the air P₂ [400 kPa]. Assume that the density of water is 1000 kg/m³, the density of mercury is 13,600 kg/m³, and that the atmospheric pressure is 100 kPa.

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Engineering Thermodynamics by Israel Urieli is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License