# A hermetically sealed tank contains a mixture of water and steam at pressure P 1 . The tank wall is.

A hermetically sealed tank contains a mixture of water and

steam at pressure P1. The tank wall is made of carbon steel. The

wall on the inside is covered by a stainless steel cladding and on the outside

by a layer of insulation. Use the specified data to find the time it takes for

the tank pressure to drop to P2 MPa.

Pressure data: Initial pressure: 2030.5 psia, final

pressure: 1500.0 psia,

Geometry data: tank total volume: 1500 ft3, water

volume fraction: 40%, tank height: 6 ft, cladding thickness: 0.5 in, carbon

steel thickness: 5 in, insulation thickness: 3 in,

Heat transfer data:

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A hermetically sealed tank contains a mixture of water and

steam at pressure P1. The tank wall is made of carbon steel. The

wall on the inside is covered by a stainless steel cladding and on the outside

by a layer of insulation. Use the specified data to find the time it takes for

the tank pressure to drop to P2 MPa.

Pressure data: Initial pressure: 2030.5 psia, final

pressure: 1500.0 psia,

Geometry data: tank total volume: 1500 ft3, water

volume fraction: 40%, tank height: 6 ft, cladding thickness: 0.5 in, carbon

steel thickness: 5 in, insulation thickness: 3 in,

Heat transfer data: ambient temperature: 85 F, heat transfer

coefficient from the mixture to the inside of the tank wall: 150 Btu/h·ft2

·F, heat transfer coefficient from the tank to the ambient: 25 Btu/h·ft2

·F,

Property data: stainless steeel: k = 8.6 Btu/h·ft·F, cp =

0.123 Btu/lbm·F, _ = 488 lbm/ft3,

carbon steel: kcarbon steel = 29.6 Btu/h·ft·F, cp

= 0.11 Btu/lbm·F, _ = 487 lbm/ft3, insulation: k = 0.3

Btu/h·ft·F, cp = 0.037 Btu/lbm·F, and _ = 27 lbm/ft

Assumptions:

a) heat loss takes place from all surfaces and

b) heat transfer coefficients remain constant throughout the

event.

[Ans.: about 20 hours].

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