Note: Real exam questions from 2012, Knowledge section, afternoon session, question 21
Thread Content
This post was last edited by dondaqin on 2015-8-25 at 10:12. 21. Regarding the local resistance losses in piping systems, which of the following statements is correct? A. In a series piping system, the local losses in each branch are necessarily equal. B. In a series piping system, the local losses in each branch are not necessarily equal. C. In a parallel piping system, the local losses in each branch are necessarily equal. D. In a parallel piping system, the local losses in each branch are not necessarily equal. Does the question refer to local resistance losses caused by pipe fittings, inlets, outlets, etc., or to those in series and parallel piping configurations? If it’s the local resistance of pipe and valve components, then BD are both correct; if it’s the local resistance in series or parallel pipelines, then only C is correct. It’s confusing.
C, I guess there shouldn’t be any objections. . . .
21BD: The local resistance Zf = S*U^2/2. In a series system, the flow rate is the same; however, the value of s can vary, so it is not necessarily equal； In parallel systems, the flow rates are not necessarily the same; if S is identical, they may differ. Of course, there are also cases with S where the traffic is the same, so it’s not necessarily the case!
Digging graves – this is a single-choice question. Options A and B, as well as C and D, represent opposite choices; there must be two correct answers. This question has been asked for 2 years now, and the questions have been problematic every year. The case studies in particular are extremely misleading