Poredoš Primož, Kitanovski Andrej, Poredoš Alojz
Laboratory for Refrigeration and District Energy, Faculty of mechanical Engineering, University of Ljubljana, 1000 Ljubljana, Slovenia.
Slovenian Energy Association, 1000 Ljubljana, Slovenia.
Entropy (Basel). 2019 Apr 10;21(4):388. doi: 10.3390/e21040388.
This paper presents an exergy-efficiency analysis of low-temperature district heating systems (DHSs) with different sanitary hot-water (SHW) boosters. The required temperature of the sanitary hot water (SHW) was set to 50 °C. The main objective of this study was to compare the exergy efficiencies of a DHS without a booster to DHSs with three different types of boosters, i.e., electric-, gas-boiler- and heat-pump-based, during the winter and summer seasons. To achieve this, we developed a generalized model for the calculation of the exergy efficiency of a DHS with or without the booster. The results show that during the winter season, for a very low relative share of SHW production, the DHS without the booster exhibits favorable exergy efficiencies compared to the DHSs with boosters. By increasing this share, an intersection point above 45 °C for the supply temperatures, at which the higher exergy efficiency of a DHS with a booster prevails, can be identified. In the summer season the results show that a DHS without a booster at a supply temperature above 70 °C achieves lower exergy efficiencies compared to DHSs with boosters at supply temperatures above 40 °C. The results also show that ultra-low supply and return temperatures should be avoided for the DHSs with boosters, due to higher rates of entropy generation.
本文对配备不同生活热水（SHW）增压装置的低温区域供热系统（DHS）进行了火用效率分析。生活热水（SHW）的所需温度设定为50°C。本研究的主要目的是比较无增压装置的DHS与配备三种不同类型增压装置（即基于电、燃气锅炉和热泵的增压装置）的DHS在冬季和夏季的火用效率。为实现这一目标，我们开发了一个通用模型，用于计算有无增压装置的DHS的火用效率。结果表明，在冬季，对于生活热水产量的相对份额非常低的情况，无增压装置的DHS与有增压装置的DHS相比，具有良好的火用效率。通过增加这一份额，可以确定在供水温度高于45°C时的一个交点，在该交点处，有增压装置的DHS具有更高的火用效率。在夏季，结果表明，对于供水温度高于70°C的无增压装置的DHS，与供水温度高于40°C的有增压装置的DHS相比，其火用效率较低。结果还表明，由于熵产生率较高，应避免有增压装置的DHS采用超低的供水和回水温度。
