A TECHNIQUE TO MEASURE INSTANTANEOUS MASS FLOW RATE FOR TIME-PERIODIC LAMINAR PIPE FLOWS AND ITS VERIFICATION WITH A UNIQUE MASS FLOW RATE CONTROL DEVICE

摘要

The present paper reports a mass flow rate measurement technique which, in principle, is applicable to any time-periodic laminar pipe flows. The referred mass flow rate metering technique is based on the exact analytical solution for fully-developed, laminar, pulsating pipe flows. In this paper, the theoretical background of the measuring technique is summarized. For experimental verification, a mass flow rate control unit was employed which permits any predetermined, time-varying, mass flow rates to be produced that is proportional to the voltage of an electronic input signal to the unit. The basic concept of this unit and its performance are also summarized in the paper. The application of this unit for verifying the performance of the developed mass flow rate measuring technique forms the major part of the paper. Performance tests were carried out for various time variations in mass flow rate pulsations. It is shown that the mass flow rate of the mean flow and that of the pulsating flow can be separated and both can be accurately measured with the proposed method. Comparative measurements show that this technique works extremely well and accurately reproduces the mass flow rate variations in time, imposed by the mass flow rate control unit, even in the case of pressure induced mass flow oscillations that results from the sudden changes in flow rate which are also known as "water hammer" or pressure surge.