Verification of Tubing Inner Diameter

Abstract

We wanted to know whether there is a discrepancy between the inner diameter of the tubes used for dosing both in Honduras as well as the AguaClara labs that could partially account for deviations from the mathematical models.

Introduction and Objectives

During previous experimentation it was observed that despite careful calculations done while designing the flow control modules, the flow values observed in both plants in Honduras and in the AguaClara lab are inconsistant with these models.  In previous experimentation, the mathematical model was adjusted to fit the observed results by using a scalar, as shown [here|Flow versus head loss data in the turbulent range].  One possible explanation for this linear variation is a difference between the actual inner diameter of the tubing used and that used for calculations.

Procedures

The procedure for this was fairly simple, though also prone to human error.  A section of tubing was cut and placed in a bucket with a plug (in this case a screw) with the same diameter as that of the inside of the tube.  The scale was then tared and the tube was filled with distilled water.  This was difficult due to air bubbles being trapped, but it was found that pipeting the water into the tube until it overflowed with out any signs of bubbles was most effective.  The tube was plugged on one end and dried, being careful not to spill any water.  It was then massed.  The bucket is needed here to ensure that any water that is spilled is also weighed.

 After being weighed, the tubing was removed and the length was measured, excluding the length of the plug inside the tube.  The diameter of the tube was calculated using this equation: