CFD analysis of pre-cooling water spray system in natural draft dry cooling towers

Lin, Xiaopei; Gurgenci, Hal; Liu, Deyou; Guan, Zhiqiang; Zhou, Ling; Wang, Pei

doi:10.1016/j.applthermaleng.2016.03.096

Cited by 51 publications

(22 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several inlet air pre-cooling methods, such as spray cooling [12][13][14] and wetted-media cooling [15][16][17], have been developed to improve the NDDCT's performance during the high ambient temperature period. Spray cooling has become increasingly used due to its simplicity, low capital cost and ease of operation and maintenance [14]. Different from ambient temperature, crosswind causes a significant decrease in performance by disturbing the natural draft processes, and its effects are considerably more complex and difficult to predict.…”

Section: Introductionmentioning

confidence: 99%

Positive impact of a tower inlet cover on natural draft dry cooling towers under crosswind conditions

Liu

Lin

et al. 2018

Applied Thermal Engineering

Self Cite

View full text Add to dashboard Cite

This study proposes a tower inlet cover to improve the performance of the small natural draft dry cooling tower (NDDCT) under crosswind conditions. CFD analyses are performed on a small NDDCT with tower inlet covers of different lengths, and the CFD model is validated against experimental results. The air temperature, air pressure, air flow and heat flux fields are presented, and the thermal performance for each heat exchanger and the NDDCT are obtained using CFD simulations. The CFD simulation results show that the high-pressure zone around the tower side wall, formed by the crosswind, causes the decrease in air flow through the tower and the deterioration in tower performance with a crosswind. The tower inlet cover can improve the tower performance in crosswinds by increasing the air flow of the heat exchangers. Tower inlet covers with lengths of 1.5 m, 3 m and 4.5 m improve the tower heat load by 40% to 65%, 70% to 130% and 85% to 230%, respectively, when the crosswind increases from 4 m/s to 12 m/s.

show abstract

Section: Introductionmentioning

confidence: 99%

Positive impact of a tower inlet cover on natural draft dry cooling towers under crosswind conditions

Liu

Lin

et al. 2018

Applied Thermal Engineering

Self Cite

View full text Add to dashboard Cite

show abstract

“…The heat and mass transfer processes in different types of cooling towers have been subject of extensive scientific research. These studies include experimental and numerical investigations of thermal and hydraulic performance of mechanical air draft wet cooling towers with counterflow [5], parallelflow [6], and crossflow arrangements [7,8], as well as natural air draft dry cooling towers with adjacent Savonius turbines [9], solar preheating of the airflow [10], water redistribution systems [11], water systems with vertical and horizontal spray nozzles [12]. All of these solutions aim to increase the cooling tower efficiency.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Heat and Mass Transfer Inside a Wet Cooling Tower

Blecich

Wolf

2018

Teh. glas. (Online)

View full text Add to dashboard Cite

This paper presents a numerical investigation of heat and mass transfer inside a wet cooling tower with forced air draft, which find application in energy process industries and oil refineries. The mathematical model consists of mass, momentum and energy conservation equations, water droplet trajectories and their interaction with the gas phase, the computational domain and boundary conditions. Numerical distributions of air velocity, air temperatures, water vapor fractions and evaporation rates are shown and discussed. The wet cooling tower achieves an efficiency of around 80%, which can be improved by optimizing the value of the water droplet size, nozzle spray angle and water-to-air flow rate ratio. The water droplet size has a dominant effect on the cooling tower efficiency, whereas small droplets improve the efficiency up to 10%. On the other hand, the spray angle and the water-to-air ratio lead to slight improvements, about 2-3% in the best case.

show abstract

“…The Eulerian framework is utilized to describe the continuous phase (air), while the Lagrangian trajectory simulations are 20 performed for the discrete phase (water droplets) [65]. The continuous phase and discrete phase flows are solved in a fully coupled manner.…”

Section: Cfd Simulationmentioning

confidence: 99%

“…It is assumed that after impingement the normal momentum component is zero while the tangential component remains the same [65]. The 'escape' boundary condition is used at drift eliminators, water basin and shell supports boundaries, which means that water droplets are terminated and excluded from further calculation at these parts [65].…”

mentioning

confidence: 99%

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

Li¹

View full text Add to dashboard Cite

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.

show abstract

CFD analysis of pre-cooling water spray system in natural draft dry cooling towers

Cited by 51 publications

References 20 publications

Positive impact of a tower inlet cover on natural draft dry cooling towers under crosswind conditions

Positive impact of a tower inlet cover on natural draft dry cooling towers under crosswind conditions

Numerical Investigation of Heat and Mass Transfer Inside a Wet Cooling Tower

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

Contact Info

Product

Resources

About