How to calculate head loss in a pipe with sudden diameter expansion?

[Chestermiller]

here it is , it should be 105N/(m^2)

Well, it's hard to know what they are referring to by "energy head lost." It isn't clear whether that is the same as "head lost." It also isn't clear whether the "given solution" is correct, because there is actually a head gain calculated , not a head loss.

Also, have you been learning about discharge coefficients and frictional head loss? If so, then the given solution is incorrect. There should be a frictional head loss included in the equation that is calculated from a discharge coefficient, based on the velocity at the 350 mm location (and and the diameter ratio at the sudden enlargement). So, have you been learning about discharge coefficients and, if so, what does your book give for the discharge coefficient for a sudden expansion to twice the diameter?

 

[foo9008]

Well, it's hard to know what they are referring to by "energy head lost." It isn't clear whether that is the same as "head lost." It also isn't clear whether the "given solution" is correct, because there is actually a head gain calculated , not a head loss.

Also, have you been learning about discharge coefficients and frictional head loss? If so, then the given solution is incorrect. There should be a frictional head loss included in the equation that is calculated from a discharge coefficient, based on the velocity at the 350 mm location (and and the diameter ratio at the sudden enlargement). So, have you been learning about discharge coefficients and, if so, what does your book give for the discharge coefficient for a sudden expansion to twice the diameter?

no , i haven't learn about discharge coefficient , but , according to the book , the loss due to expansion is given by [(V1 -V2)^2 /] 2g

 

[foo9008]

Well, it's hard to know what they are referring to by "energy head lost." It isn't clear whether that is the same as "head lost." It also isn't clear whether the "given solution" is correct, because there is actually a head gain calculated , not a head loss.

Also, have you been learning about discharge coefficients and frictional head loss? If so, then the given solution is incorrect. There should be a frictional head loss included in the equation that is calculated from a discharge coefficient, based on the velocity at the 350 mm location (and and the diameter ratio at the sudden enlargement). So, have you been learning about discharge coefficients and, if so, what does your book give for the discharge coefficient for a sudden expansion to twice the diameter?

but , if the solution look like the previous post ( your working ) , the question should be rephrased as estimate the head loss , but not estimate the total head loss/ total energy loss ?

 

[Chestermiller]

but , if the solution look like the previous post ( your working ) , the question should be rephrased as estimate the head loss , but not estimate the total head loss/ total energy loss ?

For calculating the frictional head loss at a sudden expansion, see Table 7.5-1 of Transport Phenomena by Bird, Stewart, and Lightfoot.