Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/7/2001
Publication Date: 2/7/2001
Citation: HOLT, G.A., LAIRD, J.W., BAKER, R.V., FUNK, P.A. CALCULATED VERSUS MEASURED PRESSURE LOSSES FOR TWO SEED COTTON UNLOADING SYSTEMS. APPLIED ENGINEERING IN AGRICULTURE. 2001. V. 17(4). P. 465-473. Interpretive Summary: Pneumatic conveying systems are widely used throughout the cotton ginning industry. These systems account for approximately 60 percent or more of the power requirements necessary to operate a gin. Inefficiencies in these systems can be costly and result in reduced processing rates and poor performance of the equipment. Efficiencies of pneumatic conveying systems are commonly associated with pressure loss across the system. But, how accurate are the equations used to estimate those losses when compared to "real world" systems? This paper documents modifications made to the seed cotton unloading system at the USDA-ARS, Lubbock, TX gin lab and compares the measured pressure losses against those calculated by two different methods commonly used. Results show the equations were within the range of less than 0.14 percent to 24 percent of the measured losses, depending on the equations used. Overall, the importance of properly sizing pipe, operating equipment at minimum pressure drops, and sealing leaks are made evident by the fact that the velocity in the seed cotton unloading telescope was increased 19 percent, using 37 percent less power.
Technical Abstract: Pneumatic conveying systems are commonly used in the cotton ginning industry. Inefficiencies in those systems can reduce productivity, create choke ups, and result in high operating costs. The fact that inefficient pneumatic conveying systems are costly is nothing new to the ginning industry. But, how can system losses be determined and how accurate are the eequations recommended for calculating those losses? The purpose of this papaer is threefold: 1) document modifications that were made to the seed cotton unloading system at the USDA-ARS, Lubbock, TX ginning laboratory, 2) compare those changes to values that were obtained from using standard friction loss calculations found in the literature, and 3) report the effect that modifications had on power consumption. The results showed that the equations ranged from 0.14 percent to 23.9 percent of the actual measured system losses, depending upon the calculation method used. Modifications resulted in a 19 percent velocity increase in the unloading system's suction telescope using 37 percent less power.