EFFECTS OF LIQUID TEMPERATURE AND VISCOSITY ON VENTURI INJECTORS

Abstract

The effect of chemical temperature change on the injection flow rate of a Venturi injector was evaluated. The percent change in flow rate corresponding with changes in temperature should be quantified because Venturi injectors are connected to chemical tanks at various temperatures due to radiative and convective heat transfer. Water, CAN17 (calcium ammonium nitrate), UAN32 (urea ammonium nitrate), soybean oil, and Orchex® were injected from a thermal reservoir into a PVC pipeline with a Venturi injector. Both CAN17 and UAN32 are soluble in water, while soybean oil and Orchex oil are insoluble. The injection flow rate for the four chemicals and water was measured over a range of pressure differentials between the upstream and downstream side of the Venturi, and over a range of chemical temperatures. The viscosity of water was less than 1.5 mPa·s. The viscosity of the other four chemicals ranged from 3.1 mPa·s to 121 mPa·s. The injection flow for water, with low viscosity, did not change significantly with temperature. However, the injection rate for the four chemicals was correlated with temperature and viscosity. If the chemical tank temperature variation is 20°C during the day, then the injection flow rate variation would be in the range of 50% for soybean oil, 30% for Orchex®, 10% for UAN32, and 5% for CAN17. Insoluble chemicals had much higher injection rates than soluble chemicals at the same viscosity. Because the injection rate for Venturi injectors is temperature dependent, and flow increases as chemical temperature increases, the increased cost of chemicals, environmental contamination, and crop loss might be greater than capital and maintenance savings.