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Cylindrical shell: volume increase, 6 N/mm2 pressure

Short answer

Shell expansion ΔV_shell=1.919×10⁵ mm³, water compression ΔV_w=8.078×10⁵ mm³. Additional water required = total 9.997×10⁵ mm³ ≈999.7 cm³.

A cylindrical shell of length 4 m internal diameter 300 mm and wall thickness of 12 mm is initially filled with water at atmospheric pressure. Find the increase in volume if the water is pumped to increase the internal pressure to 6 N/mm26\ \text{N/mm}^2. Take E=2.10×105 N/mm2E = 2.10\times10^5\ \text{N/mm}^2, ν=0.3\nu = 0.3 and K=2100 N/mm2K = 2100\ \text{N/mm}^2.

The extra water pumped in must fill two things: the increase in the volume of the shell (it expands) and the reduction in the volume of the water already inside (water is compressed).

Data: d=300d = 300 mm, L=4000L = 4000 mm, t=12t = 12 mm, p=6 N/mm2p = 6\ \text{N/mm}^2, E=2.1×105 N/mm2E = 2.1\times10^5\ \text{N/mm}^2, ν=0.3\nu = 0.3, K=2100 N/mm2K = 2100\ \text{N/mm}^2.

Increase in shell volume

σc=pd2t=75.0 N/mm2,σl=pd4t=37.50 N/mm2\sigma_c = \frac{pd}{2t} = 75.0\ \text{N/mm}^2, \qquad \sigma_l = \frac{pd}{4t} = 37.50\ \text{N/mm}^2 εv=pd4tE(5−4ν)=6(300)4(12)(2.1×105)(5−1.2)=6.7857×10−4\varepsilon_v = \frac{pd}{4tE}(5-4\nu) = \frac{6(300)}{4(12)(2.1\times10^5)}(5-1.2) = 6.7857\times10^{-4} V=π4(300)2(4000)=2.8274×108 mm3,δVshell=1.9186×105 mm3V = \frac{\pi}{4}(300)^2(4000) = 2.8274\times10^{8}\ \text{mm}^3, \qquad \delta V_{shell} = 1.9186\times10^{5}\ \text{mm}^3

Compression of the water

K=pδVw/V⇒δVw=pVK=6×2.8274×1082100=8.0784×105 mm3K = \frac{p}{\delta V_w/V} \Rightarrow \delta V_w = \frac{pV}{K} = \frac{6\times2.8274\times10^{8}}{2100} = 8.0784\times10^{5}\ \text{mm}^3

Additional water required

δV=δVshell+δVw=1.9186×105+8.0784×105=9.9970×105 mm3\delta V = \delta V_{shell} + \delta V_w = 1.9186\times10^{5} + 8.0784\times10^{5} = 9.9970\times10^{5}\ \text{mm}^3

Answer: additional volume of water ≈999.7 cm3\approx 999.7\ \text{cm}^3 (of which 191.9 cm³ is the expansion of the shell).

✓ Answer checked by Claude Opus 5.5 (high effort)

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