Numerical simulation of water spray for pre-cooling of inlet air in natural draft dry cooling towers

Alkhedhair, Abdullah M.; Gurgenci, Hal; Jahn, Ingo; Guan, Zhiqiang; He, Suoying

doi:10.1016/j.applthermaleng.2013.08.012

Cited by 115 publications

(76 citation statements)

References 20 publications

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“…[13]. Some previous studies also already analyzed the impact of physical parameters [12,18]. However, to the best of our knowledge, none of these studies included grid-sensitivity analysis, and none of them included a drop spectrum rather than a single drop size.…”

Section: Introductionmentioning

confidence: 99%

CFD analysis of the impact of physical parameters on evaporative cooling by a mist spray system

Montazeri

Blocken

Hensen

2015

Applied Thermal Engineering

118

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Section: Introductionmentioning

confidence: 99%

CFD analysis of the impact of physical parameters on evaporative cooling by a mist spray system

Montazeri

Blocken

Hensen

2015

Applied Thermal Engineering

118

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“…These source terms are computed from the Lagrangian framework by an alternate process through volume averaging method [66]. The governing equation of the air flow is as the same as equation (7).…”

Section: Cfd Simulationmentioning

confidence: 99%

Numerical and experimental study of small natural draft dry cooling tower for concentrating solar thermal power plant

Li¹

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The typically arid climates in the likely locations for renewable thermal power plants such as Concentrating Solar Thermal (CST) power plants provide the motivation for dry cooling technology applications. Natural draft dry cooling tower (NDDCT) with low maintenance cost and no parasitic power consumption offers a feasible and cost effective option for such applications. Compared with the conventional coal fired and nuclear power plants, the size of the CST power plant proposed for Australian regional communities is much smaller. However, the existing cooling tower design is optimised for large steam power plants, and is not optimal for these renewable power plants. (2) The performance of the experimental tower was tested at two constant heat loads of 600 kW and 840 kW, respectively, with various ambient temperatures. The 1D numerical model was refined and validated with the experimental data. The thermodynamic model of a 1 MW CST power plant running with sCO2 cycle was developed and integrated with the updated cooling tower model. Significant differences were observed between the steam Rankine and sCO2 cycles in terms of the effect of the ambient temperature on power generation. The differences between steam Rankine and sCO2 Brayton cycle in this context were analysed and discussed.(3) Two potential cooling issues with small NDDCT, the crosswind and the cold inflow, were identified and the detail experimental data were presented. The crosswind effect on small cooling tower is different from the conventional big cooling towers. With the increase of the crosswind speed, the overall cooling performance of the small NDDCT first decreases and then increases. The mixed convection theory and the Richardson Number were proposed to explain this phenomenon. On the other hand, repeated cold inflow events were observed during the tests, which cause a significant decrease of the air temperature inside the cooling tower. The water outlet temperature can be increased up to 3°C as a result of the cold inflow effect. Further analysis of the mechanism shows that the cold air incursion at the top of the cooling tower could decrease the driving force and also form an extra flow resistance for the airflow through the heat exchanger.(4) Based on the working mechanism of the air-cooled heat exchanger and the crosswind effect on NDDCT, this study proposed a new method to increase the cooling performance of NDDCT under crosswind conditions by optimizing the water mass flow rate in the air-cooled heat exchangers. By optimising the water distribution, the water outlet temperature of each heat exchanger is more uniform and the adversely influence of the crosswind can be effectively relieved.The findings in this paper can lay an important foundation for future small cooling tower design and operation.

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“…The air temperature and the equivalent mass fraction of water vapour profiles at various distances across the duct obtained for various droplet sizes (20,35,50 It was apparent that more nozzles were required to cover the full duct area. There was a significant difference in the average temperature between the two illustrations.…”

Section: Air Cooling Performancementioning

confidence: 99%

“…The use of numerical simulation for two-phase flows has a number of advantages over experimental approaches. CFD offers the advantage that full-field local data can be Spray cooling systems performance have been a subject of research for many years and several investigations have been carried out by means of Computational Fluid Dynamics technique [3,20,25,[29][30][31][32]41]. CFD is a good tool for spray cooling systems optimisation.…”

Section: Cfd Modelling Of Spray Coolingmentioning

confidence: 99%

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Modelling and experimental study of spray cooling systems for inlet air pre-cooling in natural draft dry cooling towers

Alkhedhair¹

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Geothermal energy is a promising renewable energy to be used for baseload electricity. Most potential sites with high geothermal temperature are mostly located in remote areas where water is limited. This is besides water scarcity and environmental protection, which made dry cooling systems a better alternative solution for heat rejection of power plants. Furthermore, natural draft cooling towers have the advantage of avoiding parasitic losses introduced by the fans at mechanical draft cooling towers. However, power plants utilizing dry cooling technologies experience a significant reduction in power generation during high ambient temperature periods. This reduction often goes along with the peak power demand which results in a great loss for the power plant owners. In certain instances, dry cooling tower performance can be enhanced during these periods by pre cooling of the inlet air by spraying atomized water into the inlet air.The present study introduces the use of spray cooling for inlet air pre-cooling in natural draft cooling towers. Spray cooling is investigated in this study due to its simplicity, low capital cost, ease of operation and maintenance, and capability of increasing power plant efficiency while consuming only a small amount of water compared to wet cooling towers or other evaporative cooling methods. Although spray cooling has found successful applications in process coolers and gas turbine inlet air cooling, the large scale applications in power industry have been limited.Several issues limit the application in power industry. The main one is the incomplete evaporation of water droplets which can cause corrosion and scaling of heat exchanger surface. Incomplete evaporation also increases operational cost due to water consumption. To the best of our knowledge, a detailed investigation of the spray cooling performance in natural draft dry cooling towers operating environment has not yet been performed. The aim of the current work is to optimise a spray cooling system for inlet air pre-cooling in natural draft dry cooling towers.In the present study, an Eulerian-Lagrangian 3-D numerical model was developed which is capable of simulating evaporating water sprays produced by real nozzles. In order to reproduce real nozzle characteristics in the simulation, a new adaptable method for hollow-cone spray representation in Eulerian-Lagrangian numerical models was developed. This allows real nozzles characterised during experiments to be included in the simulation, thereby correctly accounting for radial evolution of droplet size distribution and air/droplets momentum exchange. The CFD model was applied to calculate local droplet transport and evaporation, and spray cooling efficiency at different operating conditions for spray cooling systems optimisation under typical Natural Draft Dry Cooling Tower conditions.iii Experimental measurements from a wind tunnel test rig simulating Natural Draft Dry Cooling Tower inlet flow conditions have been performed in order to investigate droplet transport...

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Numerical simulation of water spray for pre-cooling of inlet air in natural draft dry cooling towers

Cited by 115 publications

References 20 publications

CFD analysis of the impact of physical parameters on evaporative cooling by a mist spray system

CFD analysis of the impact of physical parameters on evaporative cooling by a mist spray system

Numerical and experimental study of small natural draft dry cooling tower for concentrating solar thermal power plant

Modelling and experimental study of spray cooling systems for inlet air pre-cooling in natural draft dry cooling towers

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