Efficient and cost-effective district heating system with decentralized heat storage units, and triple-pipes

The novel concept of district heating system with decentralized heat storage units, different supply temperatures and two pairs of parallel twin-pipes was recently proposed and investigated thermodynamically. In this work, the use of triple-pipes for the distribution and service segments of the pipeline of this district heating scheme (where the transmission segment remains with twin-pipe type) is proposed and investigated. For this, computational fluid dynamic methods together with Evolutionary Polynomial Regression/Multi-Objective Genetic Algorithm approach are used to drive reliable correlations for estimating the rate of heat losses from the twin- and triple-pipes. The validity of the numerical simulations and the developed correlations are examined with the available data in the literature. Then, the performance of the specific district heating system in its conventional form and the revised design (i.e. when employing twin- and triple-pipes) is investigated and compared. The results show that the use of triple-pipes for the district heating improves the overall energy efficiency of the system by offering a considerably lower rate of heat loss through the distribution and service pipes. In addition, this eliminates the need for the secondary pairs of distribution and service twin-pipes, decreasing the costs of the system. (C) 2019 Elsevier Ltd. All rights reserved.