研究活動

2023年9月に，下記のとおり、論文発表（査読あり）を行いました。

発表会議：The 18th International Symposium on District Heating and Cooling　＠北京五洲クラウンインターナショナルホテル

発表場所：オンライン

 著者：タイトル他
Jincheng Dai, Minako Nabeshima, Masaki Nakao: Evaluation of Heat Transferred Between Facilities via An Uninsulated-Pipe Network on A Heat-Source Water Network, Conference Proceedings of The 18th International Symposium on District Heating and Cooling, pp. 137-144, 2023

＜抄録＞

A single-loop heat-source water network system that utilizes hot spring and wastewater heat for the hot-water-supply heat pump has been planned for hotel facilities as a system to utilize hot spring heat from the district. Although previous studies have confirmed that the heat-source water network system saves more energy than conventional systems, it is necessary to consider whether insulation is necessary for low-temperature heat-source water pipes to reduce the initial costs associated with buried piping during installation. In this study, to simulate a system consisting of a pipeline and a heat pump, a simple unsteady lumped-parameter model for heat loss from a buried pipe was proposed instead of the conventional finite element method model. This model showed that the steady-state characteristics were equal to the heat transfer analysis values, and the heat loss from the pipe was a good approximation with the results of the FEM model. Finally, the unsteady buried piping model in a heat-source water network system was simulated using Dymola to calculate heat transfer between facilities with varying soil conditions and burial depths. In the case study, the effect of soil conditions on the amount of heat obtained from the heat-source network was found to be significant for small-scale facilities, which tend to lack hot spring heat, and the effect of the burial depth was found to be small within a realistic range of burial depths. When the heat demand of the small-scale facilities increased without heat recovery equipment, the calculated heat loss of the network piping system decreased as the obtained heat of the small-scale facilities from the uninsulated buried piping system increased and the heat source temperature decreased. The obtained heat from the uninsulated buried piping system was estimated to be almost the same as that from the insulated-pipe system. The overall system coefficient of performance (COP) decreased by 0.02, compared to that of the system with insulated pipes.

＜Keywords＞

Hot spring heat utilization; District Heat Supply System; Unsteady Heat Transfer