John C. Polasek

Dispersion of Carbon Monoxide from Roadways at Low Wind Speeds

The information in this paper is directed to those persons involved in air quality along roadways. Data from an ongoing model validation program for dispersion of pollutants from roadways in Texas show that pollutant concentrations do not increase as rapidly with decreasing wind speed as predicted by most models which are based on a gaussian formulation. In fact, the actual ground level concentration may decrease with decreasing wind speed when the speed drops below some critical value. The Texas data should be sufficient to address many of the difficulties that are inherent to gaussian models at low wind speeds.

A SIMPLE APPLICATION OF MURPHREE TRAY EFFICIENCY TO SEPARATION PROCESSES

Vapor-liquid equilibrium is predicted by using the Soave modification of the Redlich-Kwong equation of state (EOSrpar;. The concept of equal fugacities is used to calculate the equilibrium constant, K1 = y1/x0, then, it is shown how the Murphree tray efficiency can be applied on the liquid or the vapor phases to modify that constant. The derivatives needed are calculated numerically, and it is shown that for absorbers and distillation columns, Murphree tray efficiency applied this way can be used to simulate the actual number of stages Murphree tray efficiency values can be specified for one, several or all of the components on any stages of a column A dehydration example is shown, the dew point depression values of a mixture of water-gas, using a triethylene glycol solution for dehydration purposes, are calculated by incorporating the method into a process simulator program called PROSIM® and compared with the values reported in the literature.

Traffic Measurement for Roadway Pollution Studies by Radar Methods

In roadway pollution studies, the vehicle count, speed, and length classification are needed to estimate the source strength. The common techniques of manual counts, tube counters and loop counters have several major difficulties in obtaining accurate counts. Furthermore, accurate speed measurement and vehicle classification is nearly impossible with these methods. A traffic measuring scheme consisting of doppler radar units mounted over each lane and interfaced to a minicomputer has been shown to be very effective in counting vehicles, and in measuring their length and speed. The accuracy has been found to be within 5%.