Question

For which of 'water' flow velocities at 200C can we assume that the flow is incompressible ? a.1000 km per hour b. 500 km per hour c. 2000 km per hour d. 200 km per hour

Answer 1

Answer:d

Explanation:

Given

Temperature$=200^{\circ}\approc 473 K$

Also $\gamma for air=1.4$

R=287 J/kg

Flow will be In-compressible when Mach no.<0.32

Mach no.$=\frac{V}{\sqrt{\gamma RT}}$

(a)$1000 km/h\approx 277.78 m/s$

Mach no.$=\frac{277.78}{\sqrt{1.4\times 287\times 473}}$

Mach no.=0.63

(b)$500 km/h\approx 138.89 m/s$

Mach no.$=\frac{138.89}{\sqrt{1.4\times 287\times 473}}$

Mach no.=0.31

(c)$2000 km/h\approx 555.55 m/s$

Mach no.$=\frac{555.55}{\sqrt{1.4\times 287\times 473}}$

Mach no.=1.27

(d)$200 km/h\approx 55.55 m/s$

Mach no.$=\frac{55.55}{\sqrt{1.4\times 287\times 473}}$

Mach no.=0.127

From above results it is clear that for Flow at velocity 200 km/h ,it will be incompressible.