Applications

Abstract

As soon as the first experiments in drag reduction by addition of small amounts of polymers, surfactants, and fibres were reported, several proposals were made for the possible applications of the effect. However, it is a long way from the idea of a possible practical application to a realization in a running installation. Several restrictions must be considered. Firstly, there has to be an ecomomic benefit besides the technical one. Thus it is essential to consider the following points:

• (i) One has to spend money on the additives. Even when the additive concentration needed to produce the desired drag reduction is very low, the consumption of additives can be considerable in case of high flow rates. In an economic study the costs for the additives are part of the variable costs.

  Besides, one has to think of how to put the additives into the flow. This requires injection and/or mixing devices. The costs for these devices are part of the fixed costs. If pumps or stirrers are needed, they will consume energy, which again increases the variable costs.

• (ii) Any additive will harm our environment to some extent. Thus any possible application requires a study of the risks for the environment.