Abstract

Calculation of gas i.e. water distribution network is much more complex compared with branch-like distribution pipelines. In this paper is shown one more suitable method in comparison to modified Hardy Cross. Here shown method as well as modified Hardy Cross method are iterative methods. For balancing of network, approximately equal number of iteration are to be calculated after the here presented node-loop method as for the improved Hardy Cross. Main advantage of the node-loop method in comparison to improved Hardy Cross method is that the final result in each calculation is flow which is used directly as input parameter in the next iteration cycle. Disadvantage of the improved Hardy Cross method is that this flows are calculated indirectly using flow corrections which they need to be added after complicated algebraic scheme to the flows calculated in previous iteration.

Abstract

After the calculation of flows in a looped pipeline distribution network is done, very often velocity of fluid in some of the pipeline branches are undersized while in other are oversized. Hence, it is necessary to perform optimization of the pipes’ diameter to fit in range of suggested values. Suggested velocities for water flow in waterworks systems are 0.75-1.5 m/s, while in the case of natural gas flow in gas-pipelines this velocity limit is increased up to20 m/s. Problem of velocity in a gas pipeline is more complex in comparison to water velocity. This issue is caused by compressibility of gas. In this paper is shown procedure of diameters’ optimization after the modified Hardy Cross method. Difference in comparison to classical problem in which flow distribution is unknown is that on the contrary, in optimization problem flows are now constants while the diameters are treated as variables.

Abstract

In the absence of a flowmeter or due to its inaccuracy, the flow rate at the discharge section of the pipeline following the observed pump can be roughly estimated if the pressure can be measured instead. To use the proposed procedure two main conditions should be achieved: (1) a manometer should be installed at the discharge pipeline between the pump and the flow regulation valve, and (2) the actual curve that relates pressure and flow for the observed pump unit should be known in advance. The described example is from Serbia, but it is of interest for any water pumping station with a submersible pump (installed in wells or tanks) where a limited number of adequate places for the measuring of flow are available (if any are available at all), but where the pressure at the discharge pipe of the observed pump can be measured. This simplified method can find applicability in installations in remote rural regions where limited resources are available. The results show that the calculated values of the flow obtained by the presented method deviate greatly in relation to the measured values provided by the portable ultrasonic flowmeter, up to 60% at one of the measuring points. However, in relation to the measured values provided by the permanently installed flowmeter the discrepancy is significantly lower (0.6–6.8%).