A new drag reducing chemical additive has been experimentally tested to minimize skin friction in turbulent pipe flow of Iraqi crude oil. Large-scale pipes of 1" 2", 3" and 4" sizes have been used in the experiments.
A friction reduction up to 63 percent has been achieved when 9 ppm of additive was added to crude oil.
The effects of crude flow rate, pipe diameter and additive concentration on t.he rate of drag reduction have been Experimentally investigated.
Many researchers [1–4{ have used different chemical additives in order to either minimize friction or increase flow rate of fluids flowing turbulently inside pipes.. Few of these who used pilot-scale pipes in their experiment.
In this paper large-scale commercial pipes have been used to investigate the effect of adding a new additive called GEM solvent (see Table 1) to Iraqi crude oil in order to practically solve the problem of controlling pumping costs and fluid flow rate.
A set of experiments have been conducted on Iraqi crude oil flowing in commercial steel pipes of 1, 2, 3 and 4-inch I.D. and 00015 relative roughness. These pipes are a. part of a loop consisting of a storage tank, a centrifugal pump, control valves. and a flow meter. Crude oil has been pumped from the storage tank via the pump in each pipe of specified diameter separately from other isolated pipes which are installed in the same loop, this is done before adding the chemical solvent and repeated after" the addition of GEM solvent to the storage tank. For each pipe the pressure drops between points of 5 meters span are recorded by the means of a multi-tube manometer. The corresponding tempera lures are reported by the means of mercury thermometers inserted in each pipe.
The results of friction factor as a function of Reynolds number for the pure crude oil are compared with the crude oils containing the chemical additive in different pipe for different additive concentrations, as shown in Figures (1–4).
As it can be shown in Figs.(1–4), a 3 ppm of additive concentration is enough to cause an appreciable and measurable amount of friction reduction. The maximum drag reduction obtained in all experiments is 63% and this was achieved in the 4-inch pipe, the thing which gives a promosing sign for practical application since the 4-inch size is close to the ones used in crude oil pipelines.
Figures (1–4) show also, as reported by Hoyt. (1972) and Virk (1975), that. friction reduction increases with Reynolds number (flow rate) for fixed pipe diameter and physical properties of oil.
Figure (5) shows that maximum drag reduction can be achieved at an optimum additive concentration of 9 ppm for the I", 3" and 4" pipes, While maximum drag reduction is obtained at 12 ppm additive concentration for the 2-inch pipe.
Figure (6) shows the effect of pipe diameter variation on the friction reduction at constant optimum additive concentration of 9 ppm. It can be noticed that drag reduction increases with increasing pipe diameter, which is promosing for practical applications.
