Experimental research of thermohydraulic dispatcher operating regimes

Abstract

Heat carrier transportation in district heating (DH) systems is an issue of a significant energy saving potential. This potential can be achieved by applying a thermohydraulic dispatcher (THD) into DH systems. THD is a vertical or horizontal shunt pipe of a large diameter with relatively low hydraulic resistance in comparison with that of connected circuits. Installation of THD along with distributed variable speed pumps in DH systems can lead to reducing or even eliminating electric energy losses caused by throttling of redundant hydraulic head. It also leads to decreasing pressure in heat supply network which improves reliability of the network. But the opportunity of further rational implementation of THD in DH systems is limited because of insufficient amount of theoretical and experimental research. This paper is concerned with the experimental research of THD operating regimes. Already known aspects of THD operation were checked and proved. New dependencies were obtained for bypassing regime and for mixing regime of THD. Besides, different types of the primary circuit connection to THD were considered: connection for non-condensing boilers and connection for condensing boilers. Simplified models describing bypassing and mixing regimes of THD were proposed. It is possible to estimate return temperature of primary circuit with the help of the bypassing regime model with an error less than 1%. At the same time the mixing regime model is suitable for finding supply temperatures of primary circuits with an error less than 2%.The results of this paper can be used for further research and development of DH systems with THD. Such systems could be traditional as well as prospective ones (low temperature and pressure DH systems).