To demonstrate and substantiate the friction reducing properties of an additive based on Tenside in an existing transmission pipeline and to shed light on the problems of heat transfer in heat exchangers through experiments with plate heat exchangers through experiments with plate heat exchangers used in this project. The project may lead to immediate 40 Gwh/Y reduction in power consumption for district heating in Denmark, and 90 GWh in West Germany.

The turbulent flow of piped water produces high frictional resistance on the boundary walls which can be reduced by the addition of small amounts of high molecular polymers or special surfactants.
Surfactants build up rod-like micelles. Under flow conditions these rods are not only aligned in the direction of flow but also build up large scale structures. Turbulence transverse to the direction of flow, especially in the core region of the pipe is damped by these ordered structures which finally cause drag reduction in turbulent pipe flow.
The cationic surfactants, with special counter ions to be used in this project, developed by Hoechst, are stable at high sheer stresses and up to 145 deg.C.
Tests indicate both that the additive has remained stable and that it should reduce pressure loss in district heating pipes by 50 per cent. The only negative results to date seems to be a reduction of the heat transfer in the tube heat exchangers used. The heat exchanger surface had to be increased by 20 per cent to ensure heat capacity.
Part of the project is to isolate the test pipe line from the rest of the transmission system for which a new heat exchanger will be built into the transmission system where the branch line is to be located.
Therefore the new, as well as the existing heat exchangers must be able to accommodate additional plates to compensate for the decrease of heat transfer, and to maintain flow temperature of 80 deg.C in the distribution network.
The Tenside will be added to the water in assumed concentrations of 250 ppm, 500 ppm, and 1,000 ppm after the pressure conditions at selected positions of the pipeline have been measured to plot its characteristics in normal operating conditions. In order to calculate pump efficiency and power consumption electricity consumption will be measured by different flows.
In advance of the test a 20 l sample of heating water will be taken out for the purpose of carrying out parallel laboratory tests.
At the maximum value of the Tenside concentration and the maximum value of the flow it should be possible to observe a reduction of the Tenside effect. This will be carried out in the broadest possible temperature range in order to measure the influence of temperature on the effect of the Tenside. Separate measurements may be carried out in the flow and return pipelines. During the test run frequent samples of the district heating water will be taken to test the value of the Tenside concentration. Test runs will be made in pipelines of 6, 14, 30 and 45 mm.
After testing, the Tenside concentration will be left in the network to observe changes with the composition of the water and the Tenside. Metal samples will also be introduced into the network to investigate improved protection against corrosion.
The project has five phases, beginning 1st September 1986 and ending 31st December 1989. Prospects for duplication are favourable with export markets to large district heating networks.