Parametric study on dynamic behaviours of basic Organic Rankine Cycle recovering waste heat with thermal power fluctuations

ABSTRACT

Waste heat sources in industrial processes, transport sectors and solar energy generally possess fluctuating and intermittent nature, which presents a great challenge to the steady operation of Organic Rankine Cycle (ORC). Thus, a parametric study is conduced to investigate the dynamic behaviors of basic Organic Rankine Cycle under fluctuating heat source. Firstly, the dynamic simulation model of basic ORC was established based on the moving boundary method. Then the effects of thermal capacity (ρc_p) of evaporator and ratio of cross-section area (A_i/A_o) of two channels for working fluid and heat source are evaluated on the step response characteristics of basic ORC. Finally, the fluctuating heat sources are assumed as a series of sinusoidal waves, and the effects of period and amplitude of fluctuating heat sources are analyzed on the characteristics of continuous operation of basic ORC. The results indicate that the response speed of evaporating pressure and superheat degree decrease with the increase of the area ratio A_i/A_o and thermal capacity ρc_p, but A_i/A_o is the dominant impactor. As for the results of continuous operation under fluctuating heat sources, it is found that the minimum superheat degree decreases with the increase of the period and amplitude of fluctuating heat sources under a fixed A_i/A_o. When the area ratio A_i/A_o increases from 0.36 to 0.60, the maximum allowable amplitude of fluctuating heat source is improved within small-period range, and it showed a reverse trend within large-period range.

KEYWORDS:

• Organic Rankine Cycle
• fluctuating heat source
• dynamic performance
• response time
• safe working range

Additional information

Funding

This research was funded by the National Natural Science Foundation of China under [grant numbers No. 51976176 and No. 51806189]; the Fundamental Research Funds for the Central Universities, [grant No. 2020QNA4008]; the Royal Academy of Engineering through the Transforming Systems through Partnerships program, [grant number TSPC1098].