Heat transfer investigation of supercritical R134a for trans-critical organic Rankine cycle system

Wang, Dabiao; Tian, Ruifeng; Zhang, Yue; Li, Lanlan; Ma, Yuezheng; Shi, Lin; Li, Hui

doi:10.1016/j.energy.2018.12.034

Cited by 24 publications

(8 citation statements)

References 39 publications

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“…The basic supercritical R134a heat transfer enhancement characteristics in the IRT were described in a previous experimental study [23]. The enhanced heat transfer will lead to smaller heat exchangers and a better TORC heat transfer economics.…”

Section: Heat Transfer Enhancement Characteristicsmentioning

confidence: 91%

“…TORC (Trans critical Organic Rankine Cycle) systems will be the next generation systems with higher thermal efficiencies and simpler system components than traditional ORC systems [8,9]. However, more research is needed to understand the supercritical organic heat transfer characteristics before TORC systems can be widely used in applications [10]. Supercritical organic heat transfer has two challenges with the need for more accurate heat transfer prediction correlations and the need for effective buoyancy restriction [11].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, heat transfer correlations based on one supercritical fluid often are not accurate for another supercritical fluid [13]. Previous supercritical heat transfer research has focused on vertical water and CO2 flows for supercritical boilers and supercritical reactors [10]. TORC systems use different tubes layouts and sizes with few studies of organic supercritical fluid heat transfer for TORC systems.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Supercritical R134a Heat Transfer in a Horizontal Ribbed Tube for Trans-Critical ORC Systems

Wang¹,

Lu²,

Fang³

et al. 2021

Proceedings of the 2nd International Conference on Fluid Flow and Thermal Science (ICFFTS'21)

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Internally ribbed tubes can improve TORC (Trans-critical Organic Rankine Cycle) heat transfer economics and safety by improving the heat transfer coefficient and restricting buoyancy effects in horizontal flows. The heat transfer characteristics of supercritical organic fluids in internally ribbed tubes need to be more thoroughly understood. The present study calculated the flow and temperature fields in a horizontal ribbed tube to analyze the heat transfer enhancement of super critical R134a and the buoyancy effects on the heat transfer. The results show that the heat transfer enhancement near the pseudo critical point is mainly caused by the large specific heat effect in the boundary layer. The buoyancy enhances the radial direction velocities (x and y directions) and reduces the axial speed (z direction) along the top of the horizontal tube. The lower axial speed reduces the turbulent kinetic energy and the top side heat transfer coefficient as a result. The simulation results were also compared with the heat transfer in a smooth horizontal tube and vertical ribbed tube with upwards flow. The results showed that the spiral follow induced by the internal ribs strongly restricts the buoyancy flow. Vertical upwards flow has a higher overall heat transfer coefficient and no circumferential temperature gradients, which improves the heat transfer economics and safety in TORC systems. Hence, vertical flow heat exchangers should be considered in TORC systems due to the improved heat transfer.

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Section: Heat Transfer Enhancement Characteristicsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Supercritical R134a Heat Transfer in a Horizontal Ribbed Tube for Trans-Critical ORC Systems

Wang¹,

Lu²,

Fang³

et al. 2021

Proceedings of the 2nd International Conference on Fluid Flow and Thermal Science (ICFFTS'21)

Self Cite

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“…The thermophysical properties of supercritical fluids considerably vary near the critical (T c ) or pseudo critical temperature (T pc ). The heat transfer coefficient, owing to dramatic variations near pseudo-critical point, depends upon pressure, tube diameter, flow direction, heat flux and type of working fluid [10]. Therefore, this results in complex heat transfer characteristics which may account for heat transfer enhancement or deterioration [11].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigations on Supercritical Heat Transfer Characteristics of Environmental Friendly Refrigerants

Ibrahim¹,

Hu²,

Jiang³

et al. 2021

IJCCE

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The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and numerical investigations have been conducted to explore supercritical water, carbon dioxide and R134a as heat transfer working fluids. Hydrofluoroolefin (HFO) and refrigerants blends have been considered the most environment-friendly refrigerants to replace Chlorofluorocarbons (CFCs), Hydrochlorofluoro-carbons (HCFCs) and Hydrofluorocarbons (HFCs). Their main advantage of zero Ozone Depletion Potential (ODP) and comparatively lower Global Warming Potential (GWP) have attracted growing amount of attention to mitigate environmental issues. This work adopts the computational method and takes the environmentally friendly refrigerants to investigate the heat transfer characteristics under widely used shear-stress transport (SST) model. A comprehensive comparison was performed at reduced pressure of 1.10 for supercritical fluids R515A, R1234ze(E) and R134a. The peaks of heat transfer coefficient occurred in the vicinity of pseudo critical temperature for all of these considered fluids; however, R134a resulted in higher heat transfer coefficient, Reynolds number and Prandtl number in comparison with R515A and R1234ze(E). The higher heat transfer coefficient of supercritical fluid R134a is owing to its thermophysical properties and the specific heat plays crucial role in the heat transfer of supercritical fluids. Owing to environmental issues, R515A can be a considerable replacement of R134a. R1234ze(E) is also promising alternative to R134a; however, safety issues should thoroughly concern its mild flammable characteristics.

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Section: Introductionmentioning

confidence: 99%

Thermophysical Properties and Supercritical Heat Transfer Characteristics of R515A

Ibrahim¹,

Hu²,

Jiang³

et al. 2021

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The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternative to replace conventional R134a, which can be beneficial for climate change. A considerable suggestion is R515A which possesses considerably lower global warming potential. The present simulations are designed to study supercritical fluid R515A under cooling conditions in horizontal position. The effect of pressure, mass flux, heat flux and tube diameter were considered for horizontal tube in the vicinity of pseudo critical temperature. Numerical investigations on heat transfer characteristics of supercritical fluid R515A were performed using widely used shear-stress transport (SST) model. Moreover, heat transfer correlations were developed and suggested to accurately predict Nusselt number within 10% accuracy. The simulation results showed about 3.98% average absolute deviation.

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Heat transfer investigation of supercritical R134a for trans-critical organic Rankine cycle system

Cited by 24 publications

References 39 publications

Numerical Study of Supercritical R134a Heat Transfer in a Horizontal Ribbed Tube for Trans-Critical ORC Systems

Numerical Study of Supercritical R134a Heat Transfer in a Horizontal Ribbed Tube for Trans-Critical ORC Systems

Numerical Investigations on Supercritical Heat Transfer Characteristics of Environmental Friendly Refrigerants

Thermophysical Properties and Supercritical Heat Transfer Characteristics of R515A

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