Page 23 - BASIC CONCEPTUAL OF THERMOFLUID

CHAPTER 2: FLUID APPLICATION

(a) (b)

Fig. 5: (a) Piezometer and (b) Barometer

Example 2.5
The inverted U-tube manometer of Figure k contains oil (SG = 0.9) and water as shown. The pressure differential
between pipes A and B, p A − p B, is −5 kPa. Determine the differential reading, h.

Figure 2.4: Inverted manometer
Solution:
Datum line, Po = Pp

LHL RHL

Pa – ρwg x 0.2 Pb - ρwg (0.3) – ρw x 0.9h

Pa – ρwgh = Pb - ρwg (0.3) – ρw x 0.9h
Pa – Pb = - ρwg (0.3) – ρw x 0.9h + 0.2ρwg

-5k = - 9810(0.3) – 9810 x 0.9 x h + (0.2 x 9810)
-5k = - 2943 – 8829h + 1962

h = 0.455 m

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