PERFORMANCE OF NOZZLE, VENTURI, AND ORIFICE METERS RELATIVE TO EXTRAPOLATION CRITERIA

摘要

Evaluation of discharge coefficient magnitude and Reynolds number dependence with respect to accepted predictions is necessary to estimate extrapolation uncertainty. Acceptance criteria as defined by PTC 6, may be applied to other meter types with the resultant ability to extrapolate with an uncertainty as defined by PTC 6. Evaluations of individual meters of all four types have resulted in acceptable performance for a very small percentage of meters other than the Throat Tap Nozzle.rnThe lack of a flow straightener in some cases (as required by paragraph 4.8-18 of PTC 6) may require increased uncertainty due to installation effects for meters meeting acceptance criteria.rnThroat Tap Nozzle manufacturers finely control manufacturing processes to meet the PTC 6 acceptance criteria. Were design criteria and fabrication detail raised to the level of the throat tap nozzle and acceptance criteria required for other meter designs, experience with these devices may indicate similar performance to the throat tap nozzle.