J. Phil Thien's Projects

The benefits of using a bell mouth shape for the outlet of a top hat style separator were discussed extensively in this thread:  http://www.jpthien.com/smf/index.php?topic=550.0

One of the charts from that thread presents a variety of duct end treatments that improve airflow over a bare duct end.  Improvements are presented in terms of percent velocity pressure, which is difficult for most people to understand. The bell mouth showed the lowest losses of the six types listed. 

In the course of measuring the performance of a 2 HP blower, I realized that I could measure the impact of three end treatments from the chart: the unflanged pipe, the flanged pipe and the unflanged cone - all using materials at hand. 

This is an excerpt from a dust collector review that is no longer available on the Porter Cable website.

Last month I made some airflow measurements when I changed the bag under my dust collector.  It is a 1994 vintage Penn State DC-2 with a 1.5 HP motor; the blower has a 10.5" impeller, 6" inlet and 5" outlet.  I removed the original spiral ramp when I installed the Thien baffle last summer.  The baffle is ¼" masonite, sold for use as a whiteboard.  Since there is no cone in the ring, I added a ¾" plywood ceiling with a large coffee can chimney.  The can is 6" diameter and extended about halfway from the ceiling to the baffle.