Discussion of the internal heat exchanger's effect on the Organic Rankine Cycle. (22nd January 2015)

• Record Type: Journal Article
• Authors: Zhu, Yadong; Hu, Zhe; Zhou, Yaodong; Jiang, Liang; Yu, Lijun
• Is Part Of: Applied thermal engineering. Volume 75(2015:Jan.)
• Page Start: 334
• Page End: 343
• Publication Date: 2015-01-22
• Subjects: Energy conversion -- Organic Rankine Cycle (ORC) -- Internal heat exchanger (IHE) -- Output power -- Thermal efficiency -- Exergy efficiency; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2014.10.037
• Languages: English
• ISSNs: 1359-4311

Abstract

Abstract: This paper explores the performances of IHE (Internal Heat Exchanger) in ORC (Organic Rankine Cycle) systems. Although previous studies hold multitudinous opinions, this study gives clear statements of IHE in both subcritical and supercritical ORC systems by setting a new model taking pressure drop in loops and acid dew point into consideration. Commonly used working fluids R123 and R600 are chosen for subcritical and supercritical cases separately. The temperature of the heat source applied is 200 °C and the mass flow rate of it is 1 kg/s. The analysis is accomplished by program Engineering Equation Solver. A modified method of calculating maximum heat exchange in IHE is given when modeling a supercritical cycle, because of the momentously changing specific heat near the critical point. Besides, a new approach is put forward to calculate the outlet temperature of the heat source and find the location of pinch point in supercritical cases. The results provide that IHE is beneficial to a subcritical case, but it improves system performance only in part of the low pressure stage in a supercritical case. Moreover, after the acid dew point T ad is taken into account, it is found that IHE is able to enlarge euphemistically the maximum system net output in a subcritical case. And in a supercritical case, the original evaporation pressure which does not conform to the rule T h, out > T ad is available now. It is revealed that the utilization of IHE will strengthen the applicability of the system. Highlights: The performances of IHE in subcritical and supercritical ORC systems are explored. The paper has set a new model and taken acid dew point into consideration. A modified maximum heat exchange in IHE calculating method has been given. A new approach calculating pinch point position has been put forward. It gives useful insights for design and operation in applications of IHE to ORC.