Thermo-flow Characteristics Research Articles

Assessment of heat transfer capabilities of some known nanofluids under turbulent flow conditions in a five-turn spiral pipe flow

Abstract In this study, the thermo-flow behaviours of the spiral tube were examined using water and some nanofluids such as TiO2, Al2O3, Fe2O3, CuO, ZnO, and CeO2. The computational flow dynamic modelling of the spiral coiled tube was performed with ANSYS 20 software program. The k–ε model with a standard wall function was used to simulate the thermo-flow characteristics. The solution of the governing equations was performed using the discretization method of finite volume. The study was carried out considering the case of fluid-to-fluid heat transfer in turbulent conditions. The influence of different key design parameters such as Reynolds number, different nanofluids, and flow arrangements was of main interest. The volume concentration of the nanofluids is 1%. The experiments were performed at different Reynolds ranges (9,000, 14,000, 20,000, and 25,000). The outlet temperature values, heat transfer coefficient, coefficient of friction, Nusselt number values of water, and nanofluids were found and compared. It was found that the outlet temperature, heat transfer coefficient, and Nusselt number values of water were the lowest, while the coefficient of friction value was the highest compared to the nanofluids. Among the nanofluids, CeO was found to have the highest outlet temperature, heat transfer coefficient, and Nusselt number value, as well as the lowest coefficient of friction value. TiO2 was found to have the lowest outlet temperature (T out), the heat transfer coefficient value, and the highest coefficient of friction value. Al2O3 was found to have the lowest Nusselt number. In addition, Nusselt number values were obtained at different Dean numbers of water (2,200, 3,400, 4,900, 6,100, 7,350, and 8,600) and found to be compatible with previous studies. In addition, the coefficients of friction values of water at different velocities (0.18, 0.24, 0.41, 0.71, 0.95, 1.07, and 1.18) were obtained and found to be compatible with previous studies.

Numerical Investigation of Thermo-Flow Characteristics of Tubes with Transverse Micro-Fins

The article presents the results of numerical studies of heat transfer and pressure drops in a channel with transverse micro-fins. The main aim of the study was to prepare the thermal and flow characteristics of such a channel for a variable longitudinal spacing of micro-fins. For the tested pipe with an internal diameter of D = 12 mm, the absolute height of the micro-fins was e = 0.243 mm, which is 2% of its diameter. The tests were carried out for turbulent flow in the range of Reynolds numbers of 5000–250,000 with the variable spacing of micro-ribs in the range of L = 0.28–13.52 mm, which corresponds to their dimensionless longitudinal distance, L/D = 0.023–1.126. For the studied geometries, the characteristics of the friction factor, ft(Re), and the Nusselt number, Nu(Re), are shown in the graphs. The highest values of Nu were observed for a spacing of L/D = 0.092 in the range of Re = 5000–60,000, while the lowest were observed for a geometry of L/D = 0.035 for Re = 60,000–250,000. The friction factors, however, were the highest for the two geometries L/D = 0.161 and L/D = 0.229 over the entire range of the tested Re numbers. A large discrepancy was observed between the friction factors calculated from the Colebrook–White equation (for irregular relative roughness depicted in the Moody diagram) and those obtained from simulations (for pipes with the same roughness height but regular geometry created by micro-fins). An analysis of the heat transfer efficiency of the tested geometries was also presented, taking into account the criterion of equal pumping power, i.e., the PEC (performance evaluation criteria) coefficient. The highest values of the PEC coefficient, up to 1.25–1.28, were obtained for micro-fin spacings of L/D = 0.069 and L/D = 0.092 in the Re number range of 20.000–30.000.

Effects of the forced convection induced by assistant fans on the thermal performance of an indirect dry cooling system

Auxiliary forced convection induced by axial flow fans was introduced to improve the ventilation and heat dissipation of a large-scale dry cooling tower under crosswinds. A numerical model coupling aerodynamic characteristics of the fans, thermo-flow characteristics of the tower, and thermodynamic calculations of the condenser was developed. By altering fan layout position, compactness, and inclination, the induced effects on thermal performance of the indirect dry cooling system were studied. Results showed that at wind speeds below 6 m/s, it is best to arrange the fans horizontally on the inlet cross-section of tower body. On this basis, distributing the fans uniformly in three rings could reduce flow turbulence inside the tower and meanwhile increase the tower ventilation. A moderate inclination of the fans could improve the synergy between the ventilation directions of the fans and airflow directions inside the tower. The combination of these steps significantly enhances thermal performance of the indirect dry cooling system, and the caused drop in back pressure of the turbine exceeds 3 kPa. At high wind speeds, the vertical arrangement of the fans outside the radiators becomes the most-effective layout for alleviating the adverse wind effects by remarkably reducing air inflow deviation angles of the radiators.

Energy-Saving Strategies of Axial Flow Fans for Direct Dry Cooling System

The operating conditions of axial flow fans are closely related to the thermo-flow characteristics of the mechanical draft direct dry cooling system. Moreover, the uneven distribution of cooling air driven by axial flow fans may lead to the deterioration of the heat transfer capacity of air-cooled condensers (ACCs). Therefore, developing energy-saving operating methods for axial flow fans is very meaningful. In this work, two kinds of adjustment strategies to make the flow field more uniform are proposed for a 2 × 300 MW direct dry cooling power-generating unit. The performance of ACCs in the prevailing wind direction is predicted with the help of the macro heat exchanger model. It is found that the inlet air temperatures of fans are significantly reduced by proposed strategies, especially at high wind speeds. Moreover, the minimum cooling air can meet the cooling demand of ACCs for the strategy which made the air flow rates of all fans consistent. Compared with the case without adjustment of fans, the total power consumption of the fan array was cut down effectively, up to 13.94% at the wind speed of 12 m/s. In conclusion, the energy efficiency of ACCs can be improved by the uniform flow field.

Exploratory research on annular-arranged moist media to improve cooling capacity of natural draft dry cooling tower and thermo-flow characteristics of its radiators

The well-arranged moist media should be a promising solution to improve the thermal performance of the natural draft dry cooling tower (NDDCT) by the synchronous implementations of air inflow field optimization and inflow air pre-cooling. In the present study, a 3D numerical model coupling a full-scale NDDCT and annular-arranged moist media was established, and the effects of the introduced moist media were explored by numerical simulation. Results show that the moist media are effective to increase the cooling capacity of the NDDCT under crosswind, with the maximum increment of 20.9% achieved at the medium wind speed of 8 m/s. The cooling capacity of the tower after the action of the moist media under the wind speed of 4 m/s exceeds the original maximum one. Through air inflow field optimization provided by the media, thermo-flow characteristics of the delta-form radiators improve. Performance deviation among the radiators alleviates, and the two cooling columns of each radiator almost have identical performance. With the further implementation of inflow air pre-cooling, each radiator, especially its cooling column right downstream the medium, obtains a further performance improvement. Under crosswind, inflow air pre-cooling is generally superior to air inflow field optimization on promoting tower performance, but the opposite result is achieved at the wind speed near 8 m/s. From the view of cost-effectiveness, the introduced moist media are most efficient at the wind speed of 6 m/s, and a 1.50 MW increment in the cooling capacity of the tower can be achieved by every 1 kg/s water evaporation.

Investigation of Thermo-Flow Characteristics of Natural Draft Dry Cooling Systems Designed with Only One Tower in 2 × 660 MW Power Plants

In recent years, natural draft dry cooling systems with only one tower have been adopted in some 2 × 660 MW power-generating units owing to the advantage of lower construction costs. The operating cases of two power-generating units and one power-generating unit will both appear based on the power load requirement, which may lead to very different flow and heat transfer performances of this typical cooling system. Therefore, this research explores the local thermo-flow characteristics of air-cooled heat exchangers and sectors, and then analyzes the overall cooling performance of the above two operating cases under various wind conditions. Using the numerical modeling method, the results indicate that the flow and heat transfer performance of this cooling system decreases significantly in the case of one unit with half sectors dismissed. At wind speeds lower than 8 m/s, the difference in turbine back pressure between two units and one unit appears obviously higher than in other wind conditions, even reaching 4.37 kPa. Furthermore, the air-cooled heat exchanger in the lower layer always has better cooling capability than that in the upper layer, especially in conditions where there is an absence of wind and under low wind speeds. The operating case of one unit is not recommended for this dry cooling system because of the highly decreased energy efficiency. In conclusion, this research could provide theoretical support for the engineering operation of this typical natural draft dry cooling system in 2 × 660 MW power plants.

Improving pedestrian micro-climate in urban canyons: City Center of Alexandria, Egypt

Due to the accelerated pace of urbanization, the study of the local urban microclimate has acquired significance. A detailed and accurate prediction of outdoor ventilation and thermal comfort is required for a healthy environment, particularly in densely built areas, due to the complex interaction of physical phenomena across different length and time scales. Engineering approaches are critical for solving the issues of wind discomfort. These approaches can however not be applied independently of the architectural context. An interdisciplinary approach can bridge the gap between architectural design and engineering wind-comfort solutions in a coastal city of developing countries with a temperate climate. The current study aims to evaluate the effect of urbanization on an asymmetrical historical canyon in the city center of Alexandria, Egypt. Challenges and limitations are imposed regarding applying retrofitting techniques to improve pedestrian comfort without changing the historical features of these areas.This paper provides a Computational Fluid Dynamics (CFD) simulation of a residential district in the modern city of Alexandria which contains the library of Alexandria and the two oldest paved roads in the world which still in use until today. The 3D steady Reynolds-averaged Navier-Stokes (RANS) equations and the standard k-ε model are used to calculate the aerodynamic flow field. These computational settings were validated with previously published wind-tunnel results. The indices of thermal comfort were calculated using a Predicted Mean Vote (PMV) model utilizing Custom Field Functions (CFF). On-site measurements of air velocity, temperature, and humidity were conducted to validate the thermo-flow characteristics with the numerical simulation and they were in a good agreement.To reach the comfort level which contributes to a pedestrian-friendly environment, it brings a range of measures that covers qualitative design guidelines on street and building level to mitigate wind discomfort and excessive solar access in urban canyons. One of these measures presents (CFD) simulations for comparing the model of the modern city with a visualized model of the ancient city of Alexandria at the end of Cleopatra's reign. This comparison aims to give a close vision on how urbanization has influenced the aerodynamics and thermal comfort in this region. The current study helps urban planners and architects to enhance the current situation for better urban microclimate at the pedestrian level, without setting up new developments during hot summer days.

Numerical Study of Parameters Effect on Thermo-flow Characteristics of up Bubbling Fluidized Bed Particle Solar Receiver

Numerical Study of Parameters Effect on Thermo-flow Characteristics of up Bubbling Fluidized Bed Particle Solar Receiver

Influencing Mechanisms of a Crosswind on the Thermo-Hydraulic Characteristics of a Large-Scale Air-Cooled Heat Exchanger

For the large scale air-cooled heat exchanger of a natural draft dry cooling system (NDDCS) in power plants, its thermo-flow characteristics are basically dominated by crosswinds. Unfortunately however, the detailed mechanisms of the crosswind effects have yet to be fully uncovered. Therefore, in this research, the local flow and heat transfer performances of the cooling deltas, which are also termed as the fundamental cells of the large-scale air-cooled heat exchanger, are specifically investigated with full consideration for the cell structure and the water-side temperature distribution at various wind speeds. A 3D CFD method with a realizable k-ε turbulence model, heat exchanger model, and porous media model is developed, and the accuracy and credibility of the numerical model are experimentally validated. With the numerical simulation, the overall 3D outlet air temperature of the large-scale air-cooled heat exchanger, and the corresponding local air velocity and temperature fields of the cooling deltas are qualitatively analyzed. Furthermore, the air-mass flow rate and heat rejection are also quantitatively studied at both the global and local views. The results depict that with an increase in the wind speed, the air mass flow rate and heat rejection will increase greatly for the frontal deltas; however, they will drop dramatically for the middle-front deltas. As for the middle- as well as the middle-rear deltas, the thermo-flow performances vary markedly at various wind speeds, which behave in the most deteriorated manner at a wind speed of 12 m/s. The rear deltas show the best thermo-flow performances at a wind speed of 12 m/s, but the worst at 16 m/s. A detailed analysis of the variable fields for each cooling delta may contribute to the performance improvement of the large-scale air-cooled heat exchanger of NDDCS.

Combined air-cooled condenser layout with in line configured finned tube bundles to improve cooling performance

Air-cooled condensers (ACCs) are commonly arranged in the A-frame form to extend the heat transfer surface with some well-recognized design flaws that inhibit the cooling performance. For overcoming this geometric defect, the combined natural draft ACC is proposed with the horizontally in line arranged finned tube bundles inside the dry-cooling tower and vertically in line configured bundles outside the tower. A three dimensional CFD method with the realizable k-ε model, radiator model and porous media model is developed and experimentally validated. The thermo-flow characteristics of the proposed ACC are analyzed and compared with two types of traditional ACCs. Besides, the effects of the platform heights from 5 m to 50 m are also investigated for the novel ACC layout. The results show that the new proposed ACC can endow with splendid cooling performance at the wind speeds lower than 9 m/s, especially in the absence of winds with the heat transfer rate increased by nearly 20% in comparison with two conventional ones. While at high wind speeds, the traditional ACC with vertically arranged heat exchanger bundles shows the highest cooling efficiency, thus is applicable to the regions with strong prevailing winds. Moreover, for the novel ACC, there exist the optimal platform heights of 15 m and 40 m at the low wind speeds and high wind speeds respectively, which can contribute to the optimal design of natural draft air-cooled condenser in power plants.

Industrial Solar Drying System: Modeling and Design Optimization of Plate Slotted Fin-and-Tube Heat Exchanger

Drying is one of the most energy-intensive stages in clay bricks manufacturing where fuel or another conventional energy source is used to heat the air before blowing it on the wet bricks. In order to reduce the energy consumption and decrease the carbon footprint of construction materials, thermal solar heat represents a promising and suitable energy source for this industrial application. In this paper, the utilization of solar energy in clay bricks drying process through compact cross flow water-to-air heat exchanger is investigated. Considering the intermittent profile of solar radiations, modeling and experimental validation of a water-to-air heat exchanger thermo-flow characteristics estimation at variable hot fluid temperature is performed. An agreement of more than 97% between numerical results and experimental measurements is demonstrated. Additionally, in order to improve the industrial solar drying system efficiency, an optimization of the heat exchanger geometric parameters is carried out based on the performance evaluation criterion and the required drying temperature in clay bricks manufacturing. According to findings, the recommended configuration for a constant heat transfer volume of 0.05m3 is characterized by tube diameter, longitudinal and transverse pitches of 18 mm, fin spacing of 2.9 mm and fin thickness of 0.6 mm. This configuration is able to increase the heat exchanger performance evaluation criterion by around 53% compared to the baseline configuration. The annual thermal performance of the solar dryer is evaluated via dynamic simulation via the TRNSYS software and shows that the optimal configuration improves the drying temperature by more than 16%.

Thermo-flow characteristics of indirect dry cooling system with elliptically arranged heat exchanger bundles around a traditional circular cooling tower

In a traditional indirect dry cooling system, the heat exchanger bundles are circularly arranged around the circumference of a cooling tower, which suffers severely from ambient winds. In this paper, an elliptical arrangement of heat exchanger bundles, which surround a traditional circular cooling tower, is proposed to restrain the adverse impacts of ambient winds. Elliptically arranged heat exchanger bundles with four different minor to major axis ratios were investigated on the condition that the total heat transfer area is the same as the traditional indirect dry cooling system. The flow and temperature fields of cooling air in the absence/presence of ambient winds were obtained. The mass flow rate, heat rejection and outlet water temperature of the alternative indirect dry cooling systems were calculated and analyzed. The results show that the elliptically arranged heat exchanger with a small ratio of minor to major axis is superior in thermo-flow performance at high wind speed. It is recommended that indirect dry cooling system incorporating elliptically arranged heat exchanger bundles be applied in regions with strong prevailing winds to achieve better thermo-flow performance.

Numerical simulation of cooling effect of vegetation enhancement in a subtropical urban park

Vegetation covers in urban parks are very useful for providing a cool microclimate which mitigates urban heat islands (UHIs). The objectives of this investigation are to therefore conduct on-site measurements and computational fluid dynamic simulations to evaluate the cooling efficacy from vegetation planted in a public park in Taipei, which is a subtropical city in Taiwan. The thermo-flow characteristics are predicted and compared with the measured air velocity and temperature data by using ultrasonic anemometers and an infrared camera to validate the computer modeling, including the sophisticated configurations of trees. Computations are also conducted to resolve the physiological equivalent temperature (PET) profiles for assessing the thermal comfort state at the pedestrian level of the outdoor environment. To investigate the impacts of park renewal on the urban microclimate, three pavilions and supplementary green areas are added to the simulation, and the results reveal that there is a better cooling effect in the park with a higher green coverage ratio (GCR). Moreover, the simulations find that the increased tree coverage ratio can more than compensate for loss of coverage of grasses, resulting in an overall decrease in average temperature. The relationship between thermal comfortable area and green coverage ratio tends to be nonlinear in nature. However, it would be more convenient for applications to adopt the linear regression analysis for determining the correlation between the GCR and PET for the percentage of areas that are comfortable (Cf). It shows that Cf=0.96×GCR+5.08, with a reasonable R2 value of 0.91, for GCR ranged from 54.5 to 71.6%, indicating that there is a significant reduced UHI effect with increases in the GCR. In addition, the correlation implies that a completely thermally comfortable condition will prevail in the park if it has full green coverage. This correlation thus serves as an important guideline for urban planners and managers when designing and managing public urban spaces, such as parks.

Thermo-flow characteristics in a corrugated plate heat exchanger considering plate deformation

Heat transfer and pressure drop characteristics were numerically investigated in a corrugated plate heat exchanger, considering the operating conditions for the nuclear power system. The plate deformation which is induced by the large pressure difference between the hot fluid side and cold fluid side was examined using the two-way fluid-structure interaction (FSI), and then the friction factors and Colburn factors were investigated for the deformed geometry. The Colburn factors for the deformed geometry were similar to those of the previous correlations, while the friction factors for the deformed geometry were about 7% higher than those of the previous correlations in large pressure difference regime.

Thermal performance and orientation effect of an inclined cross-cut cylindrical heat sink for LED light bulbs

An inclined cross-cut cylindrical heat sink was investigated in an attempt to improve the energy conversion and management of LED light bulbs. The thermo-flow characteristics were studied to enhance the cooling performance of a cylindrical heat sink, which is the cooling apparatus used for LED light bulbs. In the inclined cross-cut heat sink, the natural convection flow with an incidence angle had a flow path length that was more stretched in comparison to the flow path length of a straight cross-cut heat sink. Accordingly, the heat transfer rate between the air and fins was increased. When the fins had an inclined angle of 25–30°, the thermal resistance was the smallest. However, when the inclined angle increased to greater than 50°, only the blocking effect was increased and the flow path length was not stretched. Hence, cooling performance was decreased with inclined angles greater than 50°. A correlation predicting the degree of improvement in cooling performance relative to a baseline straight cross-cut heat sink was suggested as a function of heat sink design variables and the installation angle of the heat sink. Finally, a contour map was developed, which can be used to select the optimum heat sink type, with respect to the installation angle of the heat sink and the inclined angle of the fins.

Anti-freezing water flow rates of various sectors for natural draft dry cooling system under wind conditions

Freezing risk of air-cooled heat exchangers for natural draft dry cooling system is a key concern in power plants during cold days, so it is beneficial to the safe and economic operation of natural draft dry cooling system to propose the anti-freezing measures at various ambient conditions. As a main issue, the anti-freezing water flow rate of air-cooled heat exchanger is investigated by using the macro heat exchanger model based on the heat load balance between the circulating water and ambient air. The detailed thermo-flow characteristics of the cooling deltas and the anti-freezing water flow rate for each sector at various wind speeds are obtained with reference to the water freezing temperature, and the residual anti-freezing coefficient is introduced to describe the affluent anti-freezing capacities of each sector and cooling delta at the anti-freezing water flow rate. The results show that the anti-freezing water flow rate is highest and the residual anti-freezing coefficient is lowest for the frontal sector compared with those for other sectors. For the middle and middle-rear sectors, even with small anti-freezing water flow rates, the residual anti-freezing coefficients can be high because of the reduced heat rejection to the deteriorated air flows.

Impacts of geometric structures on thermo-flow performances of plate fin-tube bundles

Continuous plate fin-tube heat exchangers are commonly applied to natural draft dry cooling system in power plants due to their excellent thermo-flow performances, but the effects of geometrical structures on the air-side flow and heat transfer characteristics have not been thoroughly clarified yet. In this study, the air-side flow and heat transfer models of plate fin-tube bundles are developed, and the numerical modeling and methods are validated by the experimental test. The thermo-flow characteristics of the plate fin-tube bundles at various parameters of air face velocity, fin oblique angle, fin spacing, fin thickness and tube external diameter are numerically simulated. The buoyancy effect due to natural convection is also investigated. The results show that the performance evaluation criterion (PEC) varies little with the fin oblique angle. As the fin spacing increases, the average PEC will increase despite of a considerable heat transfer reduction. The increased fin thickness and tube external diameter are both beneficial to the thermo-flow characteristics, but the buoyancy effect on the flow and heat transfer performances can be neglected. The fin oblique angle of 30°, fin spacing of 10 mm, fin thickness of 0.3 mm and tube external diameter of 18 mm are recommended within the scope of investigation. The correlations between the Nusselt number, friction factor and the Reynolds number and geometrical parameters are recommended using the orthogonal experimental design method, which can be used to the optimal design of air-cooled heat exchanger in power plants.

Numerical and Experimental Research on Performance of Single-row Finned Tubes in Air Cooled Power Plants

In this paper, a new configuration of drop-shaped tube is proposed to improve the finned-tube thermo-flow performance. As the basic heat exchanger element of a Direct Air Cooled Condenser (DACC), the performance of finned tubes is very important to the optimal design of DACCs. Under turbine rated load (TRL) conditions and various frontal air velocities, the airside flow and heat transfer performance of single row flattened finned tubes and drop-shaped finned tubes are numerically investigated. The flow field, temperature field and thermo-flow characteristics are analyzed. Experimental verification and field coordination (synergy) analysis are carried out, with the simulation results agreeing well with experimental results. The performance of pressure drop, heat transfer coefficient and power consumption of these 4 Schemes are comprehensively compared and evaluated. When compared to the flattened finned tube the pressure drop of the drop-shaped Scheme 4 tube reduced by 5.9 % while the heat transfer coefficient reduced by 2.8 % at a frontal velocity of 1.8 m/s. Scheme 4 produces the best thermo-flow performance, especially at low air velocity, benefiting from a lower pressure drop and a moderate heat transfer coefficient.

Impacts of tower spacing on thermo-flow characteristics of natural draft dry cooling system

Multi-towers are widely introduced to the natural draft dry cooling system in power plants, and the geometrical layout of dry-cooling towers is a key issue to the thermo-flow characteristics of natural draft dry cooling system. Based on a representative two-tower design with vertically arranged heat exchanger bundles around the circumference, the air-side flow and heat transfer models of natural draft dry cooling system at the tower spacing to diameter ratios from 0.1 to 3 are developed and the velocity, pressure and temperature fields of cooling air in the absence and presence of ambient winds are presented. The mass flow rate and heat rejection of the two air-cooled heat exchangers at various wind speeds and in various wind directions are calculated. The correlations between the heat rejection of each tower and the tower spacing, wind speed and angle are obtained. The results show that the impacts of tower spacing on thermo-flow characteristics of natural draft dry cooling system depend on the wind speed and the arrangement of towers. The towers arranged in line are superior to those arranged in other patterns. When the tower spacing to diameter ratio is lower than unity, the conspicuous interaction between two towers will deteriorate the thermo-flow performances of natural draft dry cooling system. The results can contribute to the dry-cooling tower layout of natural draft dry cooling system in power plants.

Effects of windbreak mesh on thermo-flow characteristics of air-cooled steam condenser under windy conditions

Ambient wind has adverse impacts on the thermal-flow characteristics of air-cooled steam condenser (ACSC). A windbreak mesh is arranged below the ACSC platform and outside the ACSC steel supporting structure to improve ACSC performance, and its effects are numerically investigated. The windbreak mesh in a rectangle-type configuration improves the volumetric effectiveness of almost all periphery fans because of the protection effect. It also increases the volumetric effectiveness of most inner fans at +X wind direction, while it has little effect on inner fans at +Y wind direction because main buildings locating upstream of the ACSC weaken the protection effect of windbreak mesh. In addition, the windbreak mesh has the greatest effect on inlet air temperatures of windward fans at +X wind direction because of the alleviation of reversed flow, while the inlet air temperatures of periphery fans locating in Row 1 and Row 8 decrease obviously at +Y wind direction as a result of hot air recirculation mitigated by windbreak mesh. Obviously, the total ACSC heat transfer effectiveness is improved by windbreak mesh under windy conditions. Compared with grid-type and cross-type configurations, the windbreak mesh in rectangle-type configuration can protect the periphery fans to avoid suffering ambient wind to the greatest extent, and it consequently shows the best performance in general.