Condenser Configuration Research Articles

EXPERIMENTAL INVESTIGATION OF THE EFFECT OF CONDENSER CONFIGURATION ON A HORIZONTALLY ROTATING WICKLESS HEAT PIPE PERFORMANCE

This experimental study investigates the effect of condenser configurations on the thermal performance and operational characteristics of a horizontally rotating heat pipe. The investigated parameters include three condenser lengths (112.5, 150, and 187.5 mm), outer condenser conical ends (60, 80, and 100°), and inside condenser tapered angles (1, 2, and 3°). An experimental apparatus was designed, constructed, and commissioned with nine condenser sections to explore the effect of condenser configuration on the steady-state thermal performance of heat pipes. The heat pipe is tested at a constant speed of 1500 rpm and various heat loads ranging from 25-200 W, using water as the working fluid. Results indicated that under a constant filling, charge equals the inside evaporator volume, the best condenser length of the heat pipe equals the evaporator length. Under a variable filling, charge equals 0.25, the inside pipe volume; the best condenser length equals 1.25, the evaporator length. The condenser with a conical end of 60° enhances the heat pipe performance by about 37.5-60% over the plain condenser. However, the condenser with a tapered angle of 3° produces the best heat pipe thermal performance compared to the conical end or the different-length condensers. The tapered condenser with an angle of 3° enhances the heat pipe thermal conductivity over the plain condenser by 33.3-257.8%. Also, it achieved higher thermal conductivity than the condenser with a conical end of 60° by 16.6-125.0%.

Principles of operational optimization of CSP plants based on carbon dioxide mixtures

This research, developed in the framework of the SCARABEUS project, studies the off-design performance of transcritical power cycles running on C2-S2 mixtures in Concentrated Solar Power applications. The objective of this work is to identify optimum operational strategies that maximize net energy production when exposed to variable ambient temperature, with special focus on the operation of the Heat Rejection Unit (Air-Cooled Condenser).Four different strategies are identified, depending on ambient temperature: variable or constant condensation pressure for ambient temperatures lower than the design value, and constant turbine inlet temperature or constant return temperature of the heat transfer fluid for ambient temperature higher than design value. The results show that a combination of variable and constant minimum cycle pressure stands as the most promising alternative for low ambient temperatures, enabling net system efficiencies higher than 41%. As a drawback, this strategy poses potential issues on the control of the compressor inlet, which must be further investigated in future works. On the other hand, constant turbine inlet temperature enables higher net performance than constant return temperature of the heat transfer fluid, even if at the expense of a reduction in energy storage capacity for the same inventory of molten salts and the creation of detrimental thermal transients. Finally, it is found that the Air-cooled condenser configuration with all fans equipped with Variable Frequency Driver stands as the best alternative to maximize the techno-economic performance of the system.

Hierarchical Optimization Configuration Strategy of Synchronous Condenser in High Penetration Wind Power Sending Systems

The increasing deployment of large-scale wind turbines in place of conventional generators is expected to lead to the dominance of asynchronous power sources in future power systems, further accelerating the trend toward grid electrification. As a result, the ability of power sources to support system voltage and frequency is gradually diminishing. Synchronous condensers (SCs), which are synchronous machines operating without prime movers, serve as effective devices for providing both dynamic voltage support and inertia. They can significantly enhance the system’s capacity to maintain voltage and frequency stability. However, most existing studies on the optimization of synchronous condenser configurations tend to focus on only one aspect at a time rather than addressing both simultaneously, limiting the full potential of these devices. Optimizing either the voltage or frequency in isolation often results in suboptimal improvements in the other. Moreover, the simultaneous optimization of both voltage and frequency can lead to non-convergent outcomes, complicating the search for an optimal solution. To address this, the paper proposes a hierarchical optimization strategy for synchronous condenser configuration aimed at enhancing both voltage and frequency stability. First, the connection sites for the synchronous condensers are determined based on short-circuit ratio (SCR) constraints. Next, an outer layer optimization model is developed to minimize the total installed capacity of the condensers while taking into account the SCR and transient overvoltage levels as constraints. Following this, an inner layer optimization model is introduced, incorporating a rate of change in the frequency and maximum frequency deviation as constraints. The model is solved using the bacterial foraging optimization algorithm (BFOA). Finally, a case study of a power grid with a high proportion of wind power validates the effectiveness of the proposed synchronous condenser configuration strategy. Compared to traditional methods, the total required capacity of synchronous condensers was significantly reduced.

Study on the transient overvoltage suppression effect of the synchronous condenser of high percentage renewable energy in the sending-end system

Abstract This paper analyzes the impact of configuring a synchronous condenser on the characteristics of the Inner Mongolia power grid following the commissioning of the first grid-to-grid DC project. Simulation results show that, after the configuration of synchronous condenser, the multiple renewable energy stations short circuit ratio (MRSCR) rises, and the DC sending end of the grid is a strong system, which is conducive to the whole scale of renewable energy transmission of Inner Mongolia power grid. DC bipolar blocking faults and transient overvoltage problems at the sending end occur for different operating conditions, such as reduced power and bipolar operation. Then, the effect of different numbers of synchronous condensers on transient overvoltages is studied. The study shows that it is necessary to reasonably arrange the DC project supporting thermal power unit start-up mode and configure large-capacity synchronous condenser or a certain number of distributed regulators, which can help to alleviate the problem of transient overvoltage during faults.

Study on the effect of condenser configuration of pulsating heat pipes for space applications

In this study, the effect of condenser configuration on the thermal performance of pulsating heat pipes (PHPs) for space applications is experimentally investigated. The thermal performances of a single-condenser PHP and double-condenser PHP are compared under the constraints of the same evaporator and condenser areas. The PHPs are composed of a meandering channel with 30 turns and are made of a stainless-steel tube with the inner and outer diameters of 1.0 and 1.6 mm, respectively. R-134a is used as the working fluid, and the filling ratio is varied from 30 % to 60 %. Under various experimental conditions, the thermal performances of both single- and double-condenser PHPs are examined from two perspectives. First, the thermal resistances of the two PHPs are compared across a range of condenser temperatures from 10 to 30 °C and heat inputs from 0 to 700 W. According to the experimental observations, the double-condenser PHP exhibits a considerable reduction in thermal resistance, up to 55 % compared with the single-condenser PHP, across all the experimental conditions. Second, the operating ranges of the two PHPs are compared. For the single-condenser PHP, either an increase in the filling ratio or a decrease in the condenser temperature results in a narrower range of stable operation, with a maximum allowable heat input of approximately 200 W. On the other hand, the double-condenser PHP is mostly in the stable operating region regardless of the filling ratio or condenser temperature. Consequently, it exhibits an operating range approximately four times wider than that of the single-condenser PHP, indicating a significantly expanded range of stable operation. These improvements in thermal performance can be attributed to having the effects of doubling the number of evaporator-condenser pairs and halving the length between the evaporator and the condenser.

Exergy analysis of hybrid air-conditioning systems with different evaporative-cooling condensers under hot-humid climates

Evaporative cooling (EC) technology can effectively improve the energy efficiency of the mechanical vapor compression (MVC) system by enhancing the heat exchange capacity of its condenser. However, the current evaporative-cooling condenser system is usually only equipped with a single-stage evaporative cooler as the precooling unit, and these designs are mainly suitable for hot-dry conditions. In this study, three hybrid air-conditioning systems with different two-stage evaporative-cooling condenser configurations were proposed, one is single-condenser type and the other two are dual-condenser type, which are used to improve the exergy performance and adaptability of the evaporative condenser system under hot-humid climates. Then, the all systems were modeled via the distributed parametric method and analyzed comparatively based on the exergy method. A suitable exergy reference temperature at air saturation was discussed. Finally, the effect of four key parameters (ambient temperature and relative humidity, outdoor airflow rate and room heat load) was studied. The results showed that under the high temperature, relative humidity or room heat load conditions, the hybrid systems have a low exergy efficiency ratio (EXR) and high exergy efficiency (ηx,OEC). Among them, the newly countercurrent dual-condenser configuration (MVC-TSEC(C)) exhibits the best exergy performance under most hot-humid conditions. Compared to the conventional MVC system, the EXR and ηx,OEC of MVC-TSEC(C) increased by at most 35.0 % and 78.2 %, respectively. Moreover, its components like compressor, condenser and expansion valve have the maximum reduction rates of exergy destruction of 43.5 %, 17.2 % and 55.3 %, respectively.

Enhancing the Experimental Performance of Axially Rotating Wickless Heat Pipe Using Annular- and Longitudinally Finned Condensers

Abstract This paper investigates the impact of longitudinal- and annular-finned condensers on the steady-state thermal performance of a horizontally rotating wickless heat pipe. The parameters investigated include two fin types (longitudinal and annular) for different numbers of longitudinal (6, 12, and 18) and annular fins (15, 30, and 45) at a constant rotating speed of 1500 rpm and heat fluxes from 2090 to 16,700 W/m2. A heat pipe was designed, constructed, and commissioned with seven condenser sections. The heat pipe is charged with water as a working fluid, filling 35% of the internal pipe volume. The results indicated that fins significantly enhance the performance of the rotating heat pipe. The longitudinally finned condenser with 18 fins achieved the highest performance among the condenser configurations. Specifically, at a heat flux of 2090 W/m2, the temperature difference between the condenser and evaporator decreased by 71.2% compared to the plain condenser. Additionally, the effective thermal conductivity of the heat pipe exhibits a remarkable enhancement of 3.47 times over the plain heat pipe at the same heat flux. This enhancement highlights a substantial effect of the longitudinally finned condenser on the axially rotating heat pipe performance.

Low-grade heat to electricity conversion using the self-circulation of a magnet inside a single-turn pulsating heat pipe

Low-temperature (≤100°C) heat sources are abundantly and ubiquitously available in nature, such as solar energy, and in the form of untapped waste heat. This work aims to harness low-grade heat sources by introducing a portable harvesting system capable of effectively converting small spatial temperature gradients to mechanical and then electrical energy while maintaining a relatively high heat transfer capability. The designed and studied pair of harvesters are based on single-turn pulsating heat pipes with different condenser locations. Asymmetrical heating and cooling of the looped capillary glass tube gives rise to the bulk circulation of the internal fluid with occasional oscillation. The thermally-driven two-phase flow carries a spherical neodymium magnet fitted inside the tube. Two external solenoids generate a small amount of electricity every time the magnet passes through them. The proper functioning of energy-harvesting pulsating heat pipes (EH-PHPs) was investigated for pure water, acetone, and ethanol as the working fluids. Only water demonstrated satisfactory results and was thus selected as the main working fluid. Subsequently, high-frame-rate imaging of the internal flow along with time-domain temperature and open-circuit voltage data were employed and discussed to study the working principles of the harvester. In the next step, the mechanical, thermal, and electrical performance of the two EH-PHPs were quantitatively investigated for five different filling ratios (FRs) between 20% to 80% and five levels of heat input from 20.0W to 40.0W for each FR. Among the studied conditions, the EH-PHP with horizontal condenser (HC) configuration and 50% FR demonstrated the best performance in all three aspects. Accordingly, when 40.0W of heat was supplied to this ideal case, the magnet mean circulation frequency around the loop, effective thermal conductivity, and average induced open-circuit voltage (peak-to-peak) reached their maximum values of 0.46Hz, 11.5kW/(mK), and 0.53V, respectively. Although the integration of electromagnetic generators had reduced the heat transfer performance, the thermal conductivity of the EH-PHPs was comparable to that of conventional heat pipes and at least 25 times better than copper. Finally, the EH-PHP with HC configuration and 50% FR, the superior case, produced up to 5μW of electrical power while its solenoids were connected to load resistances with an optimum impedance. Therefore, even in its early stage of development, the portable EH-PHP can be used to supply low-power electronics such as a quartz watch. The generated electricity corresponds to about 0.01% relative Carnot efficiency. The remarkable thermal conductivity and capability of electricity production with less than 5°C temperature difference across the tube distinguish the EH-PHPs from mature energy harvesting technologies with higher energy conversion efficiencies.

Effect of the State-of-the-art Condenser Configuration on the Performance of Axially Rotating Wickless Heat Pipes

Abstract This experimental study aimed to investigate the effect of a newly shaped condenser on the thermal performance and operational parameters of a horizontally rotating wickless heat pipe. The new condenser shape has been developed based on assessing the effect of conical external ends and inner tapered wall condensers. The newly developed condenser configuration implies an external conical end of 60° and an inner tapered walls condenser of 3°. The heat pipe was subjected to a consistent rotational speed of 1500 rpm while being exposed to different heat loads, ranging from 25 to 200 W. Various filling ratios of water, from 5 to 55% of the total inner volume of the heat pipe, have been tested at rotation speeds of 750, 1000, and 1500 rpm. The results indicated that the heat pipe with the advanced condenser has a superior performance over the ones with the plain condenser by 46.75%, the conical end condenser by about 31.15%, and the tapered condenser by about 7.54%, on average over the tested heat loads from 25 to 200W. The filling ratio of 25% achieved better performance than the other tested filling ratios as the effective thermal resistance of the heat pipe decreased by 3.1 to 10.1%, 2.8 to 19.5%, and 8.9 to 24.8% for rotational speeds 750, 1000, and 1500 rpm, respectively.

Experimental Characterization and Numerical Simulation of a Low-Scale Personal Cooling System with Integrated PCM

Phase Change Materials (PCMs), among the existing thermal storage technologies, are characterized by higher storage densities than conventional storage systems, and absorb and release thermal energy at nearly constant temperatures. In recent years, the potential advantages that can be obtained by the integration of these materials into refrigeration machines have attracted the attention of specialized literature. Indeed, PCMs can allow a more efficient operation through an appropriate increase in thermal inertia, for applications relative to air conditioning in both internal residential environments and inside vehicles for the transport of people, and also in the case of machines used in the field of food refrigeration. Furthermore, in recent years, innovative solutions with integrated PCM have also been analyzed, aiming at enhancing the usability and transportability of refrigeration systems, as well as increasing the energy efficiency and reducing environmental impact. In this context, the present work focuses on the experimental characterization and numerical simulation of a cooling system with integrated PCM. In particular, the cooling system, designed for a personal cooling application, is experimentally analyzed by varying the configuration of the PCM-based condenser, while the numerical simulations have been realized to validate a simulation tool that could be used for the design and optimization of the PCM condenser configuration. The results allow us to identify the main characteristics of the analyzed personal cooling system, namely, the cooling capacity and operating autonomy, and to point out the utility and the limits of the developed simulation tool. Among the various configurations analyzed, the best one in terms of refrigeration power and autonomy is the one characterized by the highest heat transfer surface of the heat exchanger, with the refrigerant compressor at 50% power.

Comparative study on energy-saving performance of single- and two-stage evaporative-cooling condenser systems

The mechanical vapor compression system (MVC) coupled with the evaporative-cooling condenser is an effective method to improve its high temperature adaptability. However, this hybrid systems typically use an evaporative cooler as a single-stage pre-cooling unit of condenser and is mainly designed for hot–dry climates. In this paper, based on conventional evaporative-cooling condenser configuration, three two-stage evaporative-cooling condenser systems (MVC-TSEC(A), MVC-TSEC(B) and MVC-TSEC(C)) were proposed. The MVC-TSEC(A) consists of one condenser and an indirect/direct evaporative-cooler. The MVC-TSEC(B) and MVC-TSEC(C) have two condensers (in series), which are coupled with a two-stage evaporative cooling system. The refrigerant in the MVC-TSEC(C) forms a counter-flow configuration with the outdoor air, while it is concurrent flow in MVC-TSEC(B). Subsequently, the effects of the ambient parameters and outdoor air flowrate on the three two-stage hybrid systems were analyzed comparatively based on detailed numerical models. Finally, the application potential of these hybrid systems was evaluated comprehensively in hot–humid climates. The results showed that the seasonal COP and energy-saving rate for the MVC-TSEC(C) are reached by 4.2–4.7 and 12.7–21.1 %, respectively. Moreover, the static equipment payback period of the three two-stage hybrid systems are 3.8, 3.3 and 3.0 years, respectively.

Cooling water flow influence on power plant unit performance for various condenser configurations setup

Cooling water flow influence on power plant unit performance for various condenser configurations setup

Advancements in Household Refrigeration: Evaluating Cooling Efficiency and Sustainability through Innovative Technologies

Abstract: Household refrigeration technology has undergone significant advancements in recent years, driven by the need for energy efficiency, environmental sustainability, and improved cooling performance. This comprehensive study delves into various aspects of household refrigerators, including single condenser systems, double condenser configurations, and the integration of Phase Change Materials (PCMs) on the condenser surface. In Case 1, we conducted experiments to determine the cooling capacity of a standard household refrigerator equipped with a single condenser. Precise measurements and data analysis allowed us to evaluate its cooling efficiency, a crucial factor in preserving perishable items and assessing energy consumption. Case 2 extended our investigation to refrigerators with double condenser units, aiming to understand their impact on cooling performance. By comparing results with Case 1, we evaluated the potential advantages of this configuration in terms of cooling capacity and energy efficiency

A Heat Exchanger with Water Vapor Condensation on the External Surface of a Vertical Pipe

The paper is concerned with water vapor condensation on vertical pipes. The vertical position of pipes in a condenser is not discussed very often. Its application has a number of particularities in terms of the numerical determination of heat transfer. In the first stage of this paper, the authors focus on the experimental identification of heat transfer during vapor condensation on vertical pipes with a diameter of 14.0 × 1.0 mm. The pipes are placed in a narrow channel and the steam flows around them in a perpendicular direction. Two channel widths were tested, i.e., 20.0 and 24.0 mm. In the second stage, numerical modelling (CFD) is used for a detailed identification of the vapor velocity fields near the pipes. In the third stage, the results of the experimental measurements and numerical modelling are compared with data published by various authors. There are studies in the literature dealing with axial flow around vertical pipes; however, the associated results are based on conditions which are distinct from those applied in our study. The outcome of this paper is the specification of the heat transfer coefficient and the calculation formulas precisely describing the studied condenser configuration.

Comparative Thermal Performances between Pumped Thermosyphon Loops with Different Condenser Configurations Using R245fa as Working Fluid

A pumped two-phase thermosyphon loop is broadly utilized to intensify the cooling duties of electronic chipsets/systems and the effectiveness for harvesting thermal energy. The configuration of a condenser not only affects the heat transfer in the condenser, but also has an effect on the saturation pressures during the boiling and condensation processes to alter the hydrothermal performance of a pumped thermosyphon loop. The influence of the condenser configuration on the hydrothermal performance of a pumped thermosyphon loop is rarely studied. The present study comparatively examined the thermal performances of two pumped thermosyphon loops with a conventional tube-fin condenser and the expansion-tank condenser. The thermodynamic cycles in pressure-temperature and pressure-enthalpy diagrams, Nusselt numbers of evaporator and condenser, thermal resistances and various performance indexes evaluated at constant pumping powers at the controlled through-flow Reynolds numbers, boiling numbers and condenser thermal resistances were measured. At the similar thermal loads, flow rates, and fluid entry temperatures of condenser, the operating pressure of the thermosyphon loop with expansion tank condenser was considerably reduced from that with tube fin condenser, leading to the lower saturation temperature for reducing the thermal resistance and the lesser pressure drop across the loop with a noticeable hydrothermal performance improvement. At the parametric conditions tested, the ratio of dimensionless overall thermal resistances between the loops with expansion tank condenser and tube fin condenser fell in the range of 0.81–0.99. When the loop performance was compared at a constant cooling airflow rate without considering the more pumping power consumption for the loop with tube fin condenser, the ranges of thermal resistance for the loops with expansion tank condenser and tube fin condenser were 0.13–0.21 (KW−1) and 0.15–0.23 (KW−1). The merit indices evaluating the comparative hydrothermal performances of evaporator, condenser and loop between the two looped thermosyphons highlighted the significance of condenser design and affirmed the performance improvement by changing tube fin condenser into expansion tank condenser. The empirical correlations of evaporator Nusselt number, condenser Nusselt number, and overall thermal resistance using Reynolds number, boiling number, and condenser thermal resistance as the controlling parameters were generated for relevant applications.

Composition-temperature cascade control of vapor recompression assisted dividing wall column with side heat exchanger

The vapor recompression assisted dividing wall column with side heat exchanger configurations have high energy efficiency but low controllability. In this paper, the control strategies of these configurations are studied, and two composition-temperature cascade control structures of these configurations are proposed for the first time. For the vapor recompression assisted dividing wall column with side condenser configuration, the side condenser duty is chosen to control the bottom purity instead of the bottom reboiler duty. For the vapor recompression assisted dividing wall column with side reboiler configuration, both of bottom and side reboilers duties are chosen to control the bottom purity and the sensitive stage temperature respectively. The control results of two separation cases shown that the proposed control structures are effective for these two kinds of configurations. This work makes a contribution for the industrialization of the vapor recompression assisted dividing wall column with side heat exchanger processes.

A Novel Analytical Modeling of a Loop Heat Pipe Employing the Thin-Film Theory: Part I—Modeling and Simulation

In this study, steady-state analytical modeling of a loop heat pipe (LHP) equipped with a flat evaporator is presented to predict the temperatures and pressures at each important part of the LHP—evaporator, liquid reservoir (compensation chamber), vapor-transport tube, liquid-transport tube, and condenser. Additionally, this study primarily focuses on analysis of the evaporator—the only LHP component comprising a capillary structure. The liquid thin-film theory is considered to determine pressure and temperature values concerning the region adjacent to the liquid-vapor interface within the evaporator. The condensation-interface temperature is subsequently evaluated using the modified kinetic theory of gases. The present study introduces a novel method to estimate the liquid temperature at the condensation interface. Existence of relative freedom is assumed with regard to the condenser configuration, which is characterized by a simplified liquid–vapor interface. The results obtained in this study demonstrate the effectiveness of the proposed steady-state analytical model with regard to the effect of design variables on LHP heat-transfer performance. To this end, the condenser length, porosity of its capillary structure, and drop in vapor temperature therein are considered as design variables. Overall, the LHP thermal performance is observed to be reasonably responsive to changes in design parameters.

Enhanced solar still condensation by using a radiative cooling system and phase change material

In this study, an experimental investigation of using the radiative cooling potential in a solar still was studied. Instead of using an auxiliary radiative panel, an integrated collector was utilized for both processes of absorption of solar radiations and emission of infrared radiations for radiative cooling. At night-time, the coldness was stored in the PCM inside the PCM-condenser. While during the day, the water was evaporated in an evaporation tank, the produced vapor was directed to the PCM-condenser and the air cooled-condenser. Different condenser configurations were tested to evaluate the effect of radiative cooling on daily yield and solar still efficiency. The lower temperature of PCM compared to the ambient air caused the condensation to start sooner. Therefore, the radiative cooling enhanced the condensation in the solar still and increased its daily yield by about 31.2%. The daily yield of the system was 2.139 kg/m2 without radiative cooling with an efficiency of 23.9%. Using the radiative cooling at night to store coldness in the PCM-condenser increased the daily yield and efficiency to 2.805 kg/m2 day and 30.7%, respectively. Because of the limited cooling capacity of radiative cooling, utilizing an air-condenser beside the PCM-condenser was necessary to condense all produced vapor.

The features of CLPHP with partial horizontal structure

Considering the requirement of special heat transfer position in practical application, a closed-loop pulsating heat pipe (CLPHP) with partial horizontal structure (horizontal evaporator and condenser configuration) is proposed, and the features of present CLPHP including vertical start-up height and thermal performance, are numerically investigated. The volume of fluid (VOF) model and the continum surface force (CSF) model are adopted in numerical process. The reliability of present numerical method is verified by comparing the results of vertical CLPHP using present method with those of available literature. The results indicate that the proposed CLPHP can start up and running normally, as long as the height difference between the evaporator and condenser section is more than a threshold which is defined as the critical vertical start-up height. Furthermore, the dimensionless critical vertical start-up height under the conditions of various heating power and filling ration is obtained. When the filling ratio of present CLPHP remains constant, it’s found that the thermal resistance reduces with the increase of the height difference between the evaporator and condenser section, which results from the greater gravity force effect. In addition, with the argument of heating power, the thermal performances of present CLPHP with different height difference are becoming the same gradually on account of the effect of latent heat and sensible heat transport.

Annularly arranged air-cooled condenser to improve cooling efficiency of natural draft direct dry cooling system

For natural draft direct dry cooling system, the triangularly arranged air-cooled condenser may lead to the unexpected airflow deviations and unbalanced flow distributions although with an additional buoyancy force from the dry-cooling tower. In this work, an annularly arranged air-cooled condenser is proposed for natural draft direct dry cooling system. By numerical simulations, the flow and heat transfer performances of these two dry cooling systems are analyzed and compared at various wind speeds. The results show that for the annularly arranged air-cooled condenser, the air flow interactions between the neighboring cooling columns are totally avoided at small wind speeds, and moreover, the vortices at the inlets of the cooling columns may vanish for the middle sector at high wind speeds. The air inflow and outflow deviations through the cooling columns are clearly restrained, which improve the local thermo-flow performances, thus increase the heat rejection conspicuously and recover the cooling efficiency of natural draft direct dry cooling system compared with the triangularly arranged air-cooled condenser, especially at small wind speeds. The annular configuration of air-cooled condenser could be recommended for the potential engineering applications thanks to its more energy efficient performance.