4 replies to this topic

[SawsanAli311]

Dear All,

I came across the requirement of having sufficiently thick orifice for chokes flow to occur due to the reaction forces acting on the nozzle induced by high differential pressure as well as to prevent plate bending. The literature by Ward Smith states that a maximum achievable coefficient of discharge of 0.84 with a minimum t/d ratio of 0.5.

I would like then to understand if there is a relation between the t/orifice diameter ratio and the beta ratio (orifice bore diameter to pipe diameter). I guess these are two independent factors where:

- beta ratio affects the value of Cd specifically for the sub critical case, generally larger beta ratio contributes in larger low at the expense of low differential pressure.
- t/d ratio for sharp square edge orifice directly affects the value of max Cd where an optimum range of t/d between 1 and 6 at which Cd is maximum 0.84 but for cylindrical sharp edge

Thanks

[shvet1]

- t/d ratio for sharp square edge orifice directly affects the value of max Cd where an optimum range of t/d between 1 and 6 at which Cd is maximum 0.84 but for cylindrical sharp edge

 

No

 

Some links

[SawsanAli311]

Thank you for your inputs feedback,

 

kindly note that Ward Smith addressed the cylindrical nozzles with sharp edges. However, Cummingham also performed experimental data on square edge orifices where he also demonstrated the maximum achieved Cd is 0.84 for a t/d between 1 and 6 on average. 

Both agree that for chokes flow to occur with its associated high differential pressure, the orifice shall be thick enough to withstand the reaction forces across it and hence this comes at the expense of less Cd and hence less flow dictating sometimes to go with multistage ROs. 

[breizh]

Hi,

Consider the document attached to support your query.

Breizh

[SawsanAli311]

Thank you very much Breizh