Methocel Rheology

Pipe Viscometer

The objective of this experiment was to determine if an existing piping structure at an old site was capable of delivering a methocel/water mixture without blowing a rupture disk at the pipe enterance. To do this, we used a pipe viscometer to characterize the rheology of the mixture and applied our findings to the existing piping structure. Our data suggested the existing pipe structure was adequate for the proposed use.

Given that the 1.00% wt methocel solution is non-Newtonian, the power law fluid model was selected for data fitting. Over 200 sample points of data per trial included the pressure drop across a segment of pipe and the fluid flowrate. We ran 7 trials per day over 2 days. Assuming a laminar flow profile, a linearized form of the pressure drop equation revealed the n value associated with our system. We then compared the Reynolds number of each point with the critical Reynold number to validate our assumption.

Our analysis of the data is shown to the left. When compared together, we saw a poor fit between the two days of experiments. However, given the linearity of each day's results, we decided to inspect why.

A careful review of the operating conditions of the experiment revealed a large temperature difference between the two days of trials. On day 1, the system temperature was measured at ~40 Celsius, while day 2 was much lower at 20 Celsius.

Knowing that the temperature difference wouldn't account for the large difference between the days, we consulted our class advisor to explore other reasons for our results. We concluded that another group of students had forgotten to turn off the pump, causing the system pressure to increase as the fluid was heated through circulation. This caused a small portion of the water to evaporate from the system, changing the rheology of the system as the methocel weight percent increased though the day.

Additionally, we were able to raise the need for additional operation measures to prevent the unnecessary pump use if future students failed to turn off the pump.