Positive impact of a tower inlet cover on natural draft dry cooling towers under crosswind conditions (original) (raw)
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The performance of natural draft dry cooling towers under crosswind: CFD study
International Journal of Energy Research, 2004
The thermal performance of a natural draft dry cooling tower (NDDCT) under a crosswind has been investigated using a general-purpose CFD code. A three-dimensional study using the standard k–ε turbulence model to simulate airflow in and around an NDDCT has been conducted. A parametric study has been carried out to examine the effect of crosswind velocity profile and air dry-bulb temperature on the thermal performance of an NDDCT. Two approaches have been considered in this study to quantify the crosswind effect. Firstly, simulations have been conducted at the nominal conditions and crosswind effect has been represented by thermal effectiveness parameter. Secondly, the ejected heat from the NDDCT has been maintained at a constant value (285 MW) and the crosswind effect has been represented by the change in the cooling tower approach parameter. After quantifying the effect of the crosswind on the thermal performance, windbreak walls have been introduced as a means of reducing this effect. The results in this paper show the importance of considering the crosswind velocity profile. Moreover, the introduction of windbreak walls has indicated an improvement in reducing the thermal performance losses due to the crosswind. Copyright © 2004 John Wiley & Sons, Ltd.
2017
This article aims to study the thermal performances of four different natural draft cooling towers under crosswind condition. The windbreakers and the oblique exit plane have been simultaneously included in the structure of the new cooling tower. A finite volume method using SIMPLE algorithm was used to simulate the flow field around each cooling tower. The thermal performance of the new geometry has been compared with those of others for the generally investigated wind velocity profile for 10 m/s, and also two uniform wind velocities for 3 and 7 m/s. The cooling capacity of the cooling tower utilizing windbreakers and the oblique exit plane was predicted as 98.3% of the design value in the presence of generally studied wind velocity profile of 10 m/s, while that of the cooling tower utilizing windbreakers was predicted as 93.5%. Of course, the percentage of the thermal improvements of the different restoring strategies are sensitive to the profile of an approaching wind. The uniform wind velocity decreases the thermal efficiency of the cooling tower more than the distributed one, while the restoring strategies using windbreakers provide a higher percentage of thermal improvements in the presence of uniform wind velocity.
Simultaneous effects of water spray and crosswind on performance of natural draft dry cooling tower
Thermal Science, 2013
To investigate the effect of water spray and crosswind on the effectiveness of the natural draft dry cooling tower (NDDCT), a three-dimensional model has been developed. Efficiency of NDDCT is improved by water spray system at the cooling tower entrance for high ambient temperature condition with and without crosswind. The natural and forced heat convection flow inside and around the NDDCT is simulated numerically by solving the full Navier-Stokes equations in both air and water droplet phases. Comparison of the numerical results with one-dimensional analytical model and the experimental data illustrates a well-predicted heat transfer rate in the cooling tower. Applying water spray system on the cooling tower radiators enhances the cooling tower efficiency at both no wind and windy conditions. For all values of water spraying rate, NDDCTs operate most effectively at the crosswind velocity of 3m/s and as the wind speed continues to rise to more than 3 m/s up to 12 m/s, the tower effi...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 2018
The performance of natural draft dry cooling towers (NDDCTs) depends on the environmental conditions. Crosswind is known to have the most destructive effect, whereas the ambient temperature is marked as the next. A 3-D numerical model was developed to investigate the thermal performance of a single as well as three aligned units of NDDCTs under crosswind conditions. The computed results showed major discrepancies between computed velocity patterns and pressure fields around three aligned towers and those of the single tower due to windshield effect of neighboring cooling towers. The thermal performance losses for the single tower under crosswind showed higher values compared with those of towers in the aligned arrangement. The best thermal performance of three aligned NDDCTs was achieved when the crosswind was directed along the towers' connection line.
Experimental Study Of Wind Effects On The Airflow Of Natural Draft Wet Cooling Towers
2010
Natural draft cooling towers may enhance the overall performance of a thermal or a nuclear power station by providing coolant water to the condenser at a reduced temperature. The cooling tower thermal performance and its air flow inside the tower are influenced by the prevailing cross winds which in turn are amplified or damped by the flowconditioning characteristics of surrounding structures, building and terrains in the relative proximity and orientation to the tower. These characteristics were investigated in the No-1 cooling tower at the Mount Piper Power Station near Sydney in Australia. The tower was instrumented using thermocouples and directional anemometers to measure air velocities and temperatures both inside and outside of the tower over three months period. The test results have indicated that surrounding structures and their relative orientations to the tower and wind directions affect on the air flow rate inside a tower and should be considered at the design stage..
Evaluation of thermal performance for natural and forced draft wet cooling tower
Journal of Mechanical Engineering and Sciences, 2019
This paper presents an experimental and numerical investigation of the thermal performance of natural draft wet cooling tower (NDWCT). The experimental investigation is carried out under natural draft condition and forced draft condition created by an axial fan. The operational parameters considered in this study are the thickness of the fill (10 and 20 cm), inlet water temperature (40, 45, and 50 °C) and inlet water volume flow rate (5.68, 7.75, and 9.46 L/min). The experimental results showed that the thermal performance is improved when the fans are used with the NDWCT. The temperature difference between inlet and outlet and effectiveness increase by 35% and 37.2%, respectively at fill thickness of 20 cm and water volume flow rate of 11.35 L/min. The temperature distribution of the air and the relative humidity were numerically simulated for both cases of natural and forced draft by employing the commercial CFD software ANSYS Fluent 15. The experimental and numerical results were validated with results from a previous work and showed a good agreement. The experimental results showed that the effectiveness increase by 22% and 30% for NDWCT and FDWCT respectively when in case of fill thickness 20 cm.
Performance Analysis of the Natural Draft Cooling Tower in Different Seasons
Cooling towers are the biggest heat and mass transfer devices that are in widespread use. In this paper we use a natural draft counter flow cooling tower in investigating the performance of cooling tower in different seasons. The humidity is defined as water particles present in air. The humidity is the major factor in the atmosphere, it depends upon ambient temperature. Humidity is high in winter season and low in summer season.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
recently proposed theoretical method. Results showed that the towers behave in the same way under different ambient conditions. Having a reference condition and calculating three coefficients, a simple general mathematical model is created that can predict the tower's thermal performance for a wide range of applicable wind velocities. It is shown that the selection of the reference condition has a high effect on the error generated by the model. The range of the best reference condition for using the mathematical model is obtained to be wind velocities between 3 and 4 m/s and initial temperature difference (ITD) of more than 20°C. The proposed model is validated against other reported NDDCTs (numerical models for 0.41 < D/H < 0.63). The maximum error in heat rejection was shown to be 13%. This mathematical model is also extended to predict the performance of a three aligned NDDCTs located in Shiraz/Iran, by introducing a correction factor.
International Journal of Thermal Sciences, 2008
The experiment in terms of heat transfer performance of natural draft counter-flow wet cooling is done for cases with crosswind conditions. The variation of circulating-water temperature difference (T) and cooling coefficient of efficiency (η) with crosswind velocity, circulating water inlet temperature and flow rate, are shown under crosswind conditions, compared with cases without wind. According to experimental results, it is found that T and η are influenced by the crosswind , and T and η can decrease mostly by 6% and 5%, respectively. When the critical Fr l number is less than 0.174, T and η decrease with increasing crosswind velocity, however, when it is greater than 0.174, T and η increase with increasing crosswind velocity. In addition, based on the data regression analysis, the correlation between T , η and parameters, such as circulating-water inlet temperature and flow rate, is derived for cases with windless conditions. Furthermore, its correspondence is given out for cases with crosswind conditions.
Enhancing performance of wet cooling towers
Energy Conversion and Management, 2007
The effect of windbreak walls on the thermal performance of natural draft wet cooling towers (NDWCT) under crosswind has been investigated numerically. The three dimensional CFD model has utilised the standard k-e turbulence model as the turbulence closure to quantify the effects of the locations and porosities of the wall on the NDWCT thermal performance. Moreover, the improvement in the NDWCT thermal performance due to windbreak walls has been examined at different crosswind directions. Results from the current investigation have demonstrated that installing solid impermeable walls in the rain zone results in degrading the performance of the NDWCT. However, installing solid walls at the inlet of the NDWCT has enhanced the NDWCT performance at all of the investigated crosswind velocities. Similarly, installing walls with low porosity has shown improvement in the performance of the NDWCT. A reduction of 0.5-1 K in the temperature of the cooling water coming from the tower to the condenser has been achieved at all of the investigated crosswind velocities by installing porous walls both inside and outside the rain zone.