In this project, it is proposed to validate a ball valve prototype to check if it meets the required operating conditions. These conditions are as follows:
- Maximum operating flow: 2 m3 / h.
- Nominal operating flow: 1-1.5 m3 / h
- Desired opening range for nominal flow: around 70%.
- Outlet pressure: atmospheric.
- Working fluid: water.
To perform this type of validation, the first thing is to build the exact 3D model to be evaluated.
When analysing whether the design complies with the imposed restrictions, the characteristic curve of the valve will be the element that provides the most information. Said curve typically shows the relationship between the valve opening percentage and the maximum flow percentage that circulates for that opening. Since, a priori, the absolute flow rate that could flow through the valve could be any, it is necessary to assume an operating range, which is imposed by the maximum flow rate of 2m3 / h. Knowing this flow rate, a first simulation can be carried out with the valve open, in which this flow rate and an atmospheric outlet pressure will be specified. From this test, the numerical value of the total inlet pressure can be obtained, which, as is well known, results from the following equation, for an incompressible subsonic flow:
Pe: static pressure
Pt: total pressure
U: fluid velocity
Keeping this total inlet pressure fixed for each opening, the aforementioned curve can be obtained since, as the head loss increases, the inlet static pressure term will increase, proportionally decreasing the speed value and, therefore, circulation flow.
The fluid dynamic results show the expected trend, the speed range is lower the more closed the valve is (in the previous images, in order, 100%, 70% and 40% opening). The same results are used to evaluate that all the fluid passes through the expected path, with which the CFD simulations would also allow to detect leaks or unwanted preferential passages.
Finally, and after drawing up the curve, it is verified that the valve complies with the requirements imposed at the beginning, the 70% opening corresponding to approximately 1.2 m3 / h. In addition, it is observed that from 0 to 30% of the valve opening, the flow that passes through it is practically zero, which indicates that there are no leaks in the design.