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The present study is carried out using CFX, a commercial computational fluid dynamics (CFD) software, to estimate the thermal characteristics of a heat pipe. A heat pipe consists of three concentric circular tubes with three different split sections: Evaporator, adiabatic, and condenser sections. A detailed parametric study takes water and methanol as working fluids – Additionally, a study investigates the heat pipe with condenser section subjected to ambient air. The complete analysis is performed for an existing heat pipe with given design characteristics such as orientation, diameter and length, wick structure, and the stated circumstances and intake flow to the evaporator. The results are reported and compared in graphical form. It is observed that the water improves the heat pipe thermal features in terms of temperature than that of methanol. The maximum surface temperature is recorded in the evaporator zone at 132 oC, while the lowest temperature was measured at the conclusion of the condenser portion at 87.6 oC. The condenser portion's extreme surface temperature is 79.93 oC, whereas the evaporator portion's extreme surface temperature is 127 oC. When attributes are compared at atmospheric pressure, water outperforms methanol in terms of merit. This shows that compared to methanol, water has greater heat transfer properties. [ABSTRACT FROM AUTHOR]

Relevance. The necessity to develop the technologies in Russia that use non-traditional energy sources. The formation of these technologies will allow providing energy resources to the population without harmful emissions into the environment. Aim. Comprehensive analysis of the operating characteristics of a binary geothermal power plants in various climatic operating conditions. Objects. Thermal diagrams of binary geothermal power plants applicable to installation in different geographic regions and operation from different geothermal sources. Methods. Numerical studies based on mathematical algorithms of binary geothermal plant systems, comparative analysis of the efficiency of binary geothermal plants based on various external parameters. Results and conclusions. Numerical studies have been conducted to determine the efficiency of geothermal power plants with a binary thermal circuit and an air-cooled condenser were conducted during their operation on various sources, for which 15 known geothermal sources located in Russia in different geographical regions were selected. Possible operating parameters of binary geothermal power plants were analyzed based on the known characteristics of the fluid at the well outlet. Since the geothermal power plant has an air-cooled condenser in its thermal circuit, its operating parameters were obtained from the average monthly ambient air temperatures in the calendar year in the region where the analyzed geothermal source is located. Numerical studies showed the impact of thermal source parameters and climatic features on the efficiency of electric energy generation by means of a binary plant. It was revealed that with the possible operation of a binary geothermal plant during a calendar year, the highest average monthly electric power is expectedly achieved in the cold period of time, in this case in January, and is 1752 kW for the Mogoysky hot spring. For the warmest month of the year – July – the binary power plant of the Mechigmen hot spring could have the greatest electric power of 930 kW. The greatest absolute electric efficiency in January reaches 15.22%, depends to a greater extent on the value of the temperature of the heat supply in the cycle and among the binary stations considered in this work, the geothermal power plants in the settlement of Chazhemto could have it.

Water spraying upstream of an air-cooled condenser enables high heat dissipation. Meanwhile, a good control on the spray-heater parameters is crucial to avoid excesses of water and heat transfer destruction. This paper aims to experimentally illustrate the impact of the operating time of the mist device on the condenser thermal performances and the refrigerator energy consumption. To better visualize water stagnation phenomena, experiments are performed using a low pressure spraying device with 0.0065 L/min in water flow and 2–4 bar in pressure range. Several series of measurements have been performed on the refrigerant temperatures and pressures and on power consumption for different operating times of the mist device. Measured results showed that with 2 min of misting, the condenser inlet airflow temperature and the refrigerant condensing pressure drop respectively from 32 to 27.4 °C and 10 to 7.2 bar, while for 1 min of misting they decrease from 32 to 28 °C and 10 to 7.6 bar, respectively. In this work, compared to the system without misting, maintaining the mist system in operation for 2 min allowed 54.9 % enhancement in the Coefficient of Performance and 17.2% reduction in energy consumption. Consequently, the operating time of the mist device highly affects the condenser cooling performances and the refrigerator power consumption. Meanwhile, it is found that, above 2 min of misting, the condenser inlet airflow is saturated and the condensing pressure hardly changes while water stagnation is occurring. Hence, misting should be applied momentarily to avoid heat transfer destruction and water losses.

Thermal power generation is economical in the current scenario, but it is a water-intensive process, resulting in a high-water footprint. In this research, life cycle water use (LCWU) was assessed for three coal-based thermal power plant in India. The LCWU was found to be in the range of 2.5 to 3.5 L-kWh−1. The results of the LCWU of coal-based thermal power plants in India are higher than the global average of 1.75 L-kWh−1. In order to reduce the dependency on water, air-cooled condenser (ACC) with a novel approach of reducing temperature of air before entering into condenser is purposed using vapour absorption chillers. A 300 MW thermal power plant located in the South India region is chosen to illustrate the application of the proposed system. Initially, waste heat from flue gas is used to run a vapour absorption chiller, and finally a solar-assisted vapour compression chiller is used. Also, in order to utilize large coastal lines in India, an alternate approach of sea water cooling-based thermal power generation is investigated. A 2 MW steam turbine plant utilizing deep sea water is designed and analysed. In seawater cooling system the condenser temperature is reduced, increasing efficiency by 1.9% and power output by 133 kW. It resulted in power generation with multiple benefits, including cooling, desalinated water, and increased plant efficiency. The outcomes of this study provide information on water use in Indian thermal power plants along with its comparative assessment. A study of ACCs and seawater-cooled condensers is also an opportunity to reduce the life-cycle water use in thermal power plants in India. [ABSTRACT FROM AUTHOR]

Generators and condensers are the two vital equipment items that determine the output of vapor absorption refrigeration systems. Arid weather conditions produce a significant reduction in the performance of the vapor absorption refrigeration cycle due to low condenser heat dissipation despite high generator temperatures. Although numerous studies on condenser cooling methods in vapor compression systems have been reported in the literature, solar-operated vapor absorption systems have not been studied. Limitations in generator temperatures of solar-operated vapor absorption systems necessitate a focused study in this area. This study makes the selection of the best choice for condenser cooling from among four different condenser cooling methods which have an impact on the performance of the vapor absorption refrigeration system for effective cooling using solar energy. A solar vapor absorption refrigeration system working with low-grade heat using a compound parabolic collector is considered in this study. Analysis of a vapor absorption refrigeration system for cooling in arid weather conditions is carried out using different condenser cooling methods with Engineering Equation Solver. Initially, the model used in the study is compared with a similar study reported in the literature. Techniques considered are air, water, evaporative, and hybrid cooling techniques. The performance of the vapor absorption cooling system was analyzed using experimental values of a solar compound parabolic collector obtained from real-time measurements for simulating the model. Results show that water cooling can provide suitable condenser cooling and improve the coefficient of performance of the solar vapor absorption refrigeration system using the solar collector. The water-cooled condenser has 1.9%, 3.3%, and 2.1% higher COP when compared to air-cooled condensers for spring, summer, and autumn seasons respectively, whereas the water-cooled condenser cooling recorded 6%, 14%, and 8% higher COP relative to the evaporative cooling method. Cost comparison showed maximum cost for water-cooled condensers and minimum cost for hybrid-cooled condensers. The effect of each cooling method on the environment is discussed. [ABSTRACT FROM AUTHOR]

An Air-cooled condenser (ACC), which finds popularity in a steam power plant in arid areas, is usually less efficient as film condensation occurs inside the condenser tube. Recent research is directed towards eliminating the thermally insulating liquid film with the application of novel superhydrophobic surfaces. The self-cleaning property of such surfaces facilitates easy condensate drainage in the form of jumping droplets exposing favourable nucleation sites, thereby significantly promoting dropwise condensation. The present study explores the characteristics of jumping droplet condensation in finite condenser tubes using computational fluid dynamics (CFD). The wall-heat-flux for condensation is modelled here by a uniform suction boundary condition. The strength of suction is quantified by a suction Reynolds number Re s . We mainly focus on the zone corresponding to 2.3 < Re s < 10, where no previous solution exists. In a long horizontal tube, the progressive realization of a self-similar region starting from the developing regions is demonstrated. We examine the characteristics of the developing region based on the sign of the pressure gradient. The results of three-dimensional CFD simulations illustrate the variations of droplet trajectories with the inception size and coordinates of jumping droplets determined locally by the relative contributions of various force components, viz. gravity, axial drag in the vapour core, suction induced radial drag and Saffman lift. The present study also predicts the effect of pipeline inclination on condensate drainage. Ultimately, considering multiple jumps, we found that the maximum condensate emission can be obtained for small droplets (5−15 μm), while medium-sized droplets (20−50 μm) are most advantageous for isolated jumps. [ABSTRACT FROM AUTHOR]

This study discusses the influence of natural wind on the air flow of air-cooled condensers (ACCs) and then proposes a partition speed-regulation strategy for a fan group with enhanced generalized capability, which is of great practical significance for optimizing energy-saving operations. The stochastic time-varying features of natural wind are characterized by sine–Gaussian, Weibull, and composed winds. In a natural wind disturbance, using the Sugon Supercomputing Center, the transient numerical simulation of the dynamic evolution of the ACC flow field was found: the dynamic system of air flow is a typical time-varying nonlinear process. Cluster analysis was used to extract the nonlinear features of air flow, divide the fan group into four subregions with generalization capability, and implement a partitioned speed operation. It was found that giving priority to increasing the fan speed in the headwind partition can suppress the natural wind disturbance and improve the overall air flow, thus reducing the fan speed in the leeward partition, which reduces the overall air flow loss. The dynamic characteristics of the fan group obtained from the simulation and the proposed fan partition method can guide the optimized energy-saving operation of ACCs. [ABSTRACT FROM AUTHOR]

Air-cooled condensers in thermal power plants have recently become increasingly popular. Besides all the advantages they have, like no demands for water supply on the plant site and no need for taking care of environmental regulations, they also have some serious disadvantages. One of the biggest disadvantages air-cooled condensers do have is precisely the nature of the Earth's atmosphere being their low temperature reservoir. Low density and low heat capacity of the air as the cooling medium combined with extremely stochastic behavior of the atmosphere itself put some serious challenges in front of the air-cooled condenser's proper and steady functioning. In this paper, the operating parameters of the air-cooled condenser in the chosen thermal power plant were investigated to gain a clearer insight into the influence of the atmospheric changes on its entropy generation and consequently on its efficiency. Also, the acquired results were further proposed as a starting point for potential optimization of the process inside the device. [ABSTRACT FROM AUTHOR]

The self-circulating evaporative cooling technology, by using latent heat, solves the bottleneck problem of high heat flux dissipation of the power electronic devices. In selfcirculating system, the pressure drop of heat transfer fluid through each component needs to be minimized for the weak circulating power. Thus, the air-cooled condenser design must consider the pressure drop along the fluid flow. This paper presents the design flow and thermodynamic model of the air-cooled condenser, and the self-circulating test platform which features heat exchange capacity and pressure drop measurement. In view of the heat exchange capacity of 17 kW and the pressure drop limit below 500Pa, a new air-cooled condenser is constructed with design flow optimized parameters and verified through experiments. The results indicate that the pressure drop error between experimental and designed values was less than 16.6% for a heat dissipation rate over 17kW. After further discussion, it is concluded that a fluid-sided hydraulic diameter of 2.5-3mm provides an effective balance between heat exchange capacity and pressure drop. With the increase of air speed, the total heat transfer coefficient of the condenser increases dramatically while the fin spacing makes a greater increase in air pressure drop than in heat transfer coefficient. [ABSTRACT FROM AUTHOR]

The paper presents the results of a theoretical and experimental study aimed at improving the efficiency of commercial refrigeration systems and taking into account the external negative impact on heat transfer and aerodynamics of an air-cooled condenser. The issues of the impact of solid fouling on the outer heat transfer surface of the air-cooled condenser as a factor that worsens its energy efficiency and operational reliability have been studied. A small-scale commercial refrigeration machine has been used for carrying out the study. To create external real conditions in the experimental bench, a climatic chamber and a thermostatic chamber are provided. Three types of solid fouling have been used: dust, fluff, and sand. The fouling has been collected from real operating air-cooled condensers which are identical to the experimental heat exchanger. The experimental study has been carried out with a variable mass of fouling, which made it possible to simulate various real operating conditions for the air-cooled condenser. As a result of the experiment, it has been found that out of a set of fouling roadsides, the dust has the greatest negative impact on the characteristics of the refrigeration machine as a whole, and sand has the greatest negative effect on the internal characteristics of the air-cooled condenser. Recommendations are made to determine the moment of cleaning the surface of the air-cooled condenser based on energy-saving parameters. It is proposed to fix the moment of cleaning using computer software using the permissible air mass velocity as a key parameter and the refrigeration machine operation interval under this condition. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Wet cooling towers (WCT) are widely used to reject the unutilized heat in coal thermal power plants (TPPs). But this comes at the cost of excessive water consumption. Adoption of air-cooled condensers (ACC), also known as dry cooling systems, in all proposed Indian TPPs would reduce their water consumption by 26% in 2030. However, power producers are reluctant to install ACC due to technical and economic disadvantages such as high capital investment and land footprint. This study evaluates the major challenges in implementing ACC by quantifying them in terms of cost of electricity generation. Critical parameters of WCT and ACC, such as water and auxiliary consumption, are also estimated at varying ambient air conditions. The study shows that cost of electricity generation in TPPs with ACC would increase by 0.26–0.30 INR/kWh (0.37–0.42 US cents/kWh) compared to those TPPs with WCT. Despite this, installation of ACC would still be economically viable for those TPPs that are susceptible to at least 1 month of shutdown annually due to water shortages. On an average, Indian plants that are located at high water-stressed regions operate 1.5 months lesser than those at low and medium water-stressed regions. Such TPPs would see an increase in cost of electricity generation by 0.17 INR/kWh (0.24 US cents/kWh) compared to TPPs with ACC.

• A scaled-down platform is established to study the cluster effect and fan partition scheme. • Experimental data is utilized to calculate the divisional cluster factor of fans. • An energy-efficient operation strategy based on divisional regulation is proposed. The aerodynamic behavior of the fans array of the direct air-cooled condenser is different from that of a single fan because of the interaction effect between fans and the influence of wind. In this paper, a scale-down fan array experimental platform with measurement of the airflow and ambient wind speed is established to study the fan array partition schemes and cluster effect. The divisional cluster factors are obtained by experiment and generalized by random forest regression. The dynamic models of the condenser backpressure are introduced by the moving-boundary method. To achieve transient performance, a divisional control strategy for the direct air-cooled condenser is realized by MPC-PID cascade control. The simulation result shows that the fan power consumption is reduced by 14.7% compared to the existing control strategy. Furthermore, the wind speed disturbance is quickly suppressed by cascade control. [ABSTRACT FROM AUTHOR]

The cooling performance of air-cooled condenser (ACC) is susceptible to adverse impacts of ambient winds. In this work, three kinds of lateral double-layered deflectors installed under the ACC platform are proposed to weaken the unfavorable effects of cross winds. Through CFD simulation methods, the main parameters of thermo-flow performances of a 2×660 MW direct dry cooling system are obtained, by which it can be concluded that the deflectors can effectively reduce the inlet air temperatures while enhance the mass flow rates of upwind fans due to the guiding effect, especially at high wind speeds, while the improvement of cooling capacity of ACCs in the 0° wind direction is weak. The inclined-vertical deflectors are superior to others in performance improvement of ACCs for all cases, which can reduce the turbine back pressure by 12.15% when the wind speed is 12 m/s, so they can be applied to the performance enhancement of ACCs under windy conditions in practical engineering. [ABSTRACT FROM AUTHOR]

For a direct dry cooling system, the turbine back pressure fluctuates with the meteorological conditions. Moreover, the operation of axial flow fans plays an important role in the cooling performance of air‐cooled condensers (ACC). It is of significant use to study the operation strategies of axial flow fans under various ambient conditions. Based on typical 2 × 660MWdirect dry cooling power generating units, the ACC model coupled with the turbine thermodynamic characteristics is developed, by which the thermo‐flow performances of the ACC are predicted in the dominant wind direction, and then the standard coal consumption is calculated. The results show that the increased ambient temperature and wind speed, or the reduced fan rotational speed leads to the high turbine back pressure. At the low ambient temperature and wind speed, the standard coal consumption rate of the unit can be reduced by reducing the speed of axial flow fans appropriately, with the maximum drop in coal consumption rate reached 0.734 g/(kWh) when the ambient temperature is 10°C without wind. If the wind speed exceeds 12 m/s or the ambient temperature reaches 25°C, 110% of the rated fan rotational speed is recommended. [ABSTRACT FROM AUTHOR]

This paper reports an experimental investigation of a closed‐loop thermosyphon system charged with water and other low saturation fluids, such as ethanol, acetone, and methanol, for different adiabatic lengths, filling ratios, and heat loads. The closed‐loop thermosyphon with two inline vertical heaters in the evaporator section and forced air‐cooled plate‐type heat exchanger in the condenser section, connected by a changeable adiabatic length, is investigated at different working conditions. Out of five filling ratios used in the analysis, at 0.6 filling ratio, the loop thermosyphon is seen to be operated at its best. The acetone‐charged loop thermosyphon shows the lowest values (up to 72% reduction) of overall thermal resistance than that of other fluids and significantly higher effectiveness, due to the plate‐type forced aircooled condenser. For the acetone‐filled thermosyphon, an almost 15% increase in the effectiveness is observed by changing the adiabatic length from 800 to 200mm. This study suggests that the limitation of the loop thermosyphon with a water‐cooled condenser to cool electronic components, computational clusters, and data centers is well fulfilled by the loop thermosyphon with plate‐type forced air‐cooled condenser. The nucleate pool boiling correlation is developed and validated for the loop thermosyphon system to determine the evaporator heat transfer coefficient. [ABSTRACT FROM AUTHOR]

Air-cooled condensers are predominantly used in condensing units of split air conditioning systems. These units are mostly installed on terraces or on outer walls of buildings. In case of tall buildings, the performance of air-cooled condenser is greatly affected by high-speed winds. Present work deals with a numerical study predicting the influence of high-speed winds on the performance of split air conditioning systems whose condensing units are installed on outer walls of buildings using mounting brackets. Simulation tools viz. ANSYS Fluent and VapCyc are employed in this work in order to obtain air flow and thermal characteristics of the condensing unit. Simulation results show that the thermo-flow performance of the split air conditioning system deteriorates significantly with high-speed winds due to an increase in the temperature of air entering the condensing unit and inferior air flow rates in the condensing unit. It is observed that the cooling capacity and coefficient of performance of the air conditioning system are reduced by 11% and 35%, respectively, when wind speed is 12.3 m/s in comparison with the baseline case. [ABSTRACT FROM AUTHOR]

Wet cooling towers (WCT) are widely used to reject the unutilized heat in coal thermal power plants (TPPs). But this comes at the cost of excessive water consumption. Adoption of air-cooled condensers (ACC), also known as dry cooling systems, in all proposed Indian TPPs would reduce their water consumption by 26% in 2030. However, power producers are reluctant to install ACC due to technical and economic disadvantages such as high capital investment and land footprint. This study evaluates the major challenges in implementing ACC by quantifying them in terms of cost of electricity generation. Critical parameters of WCT and ACC, such as water and auxiliary consumption, are also estimated at varying ambient air conditions. The study shows that cost of electricity generation in TPPs with ACC would increase by 0.26–0.30 INR/kWh (0.37–0.42 US cents/kWh) compared to those TPPs with WCT. Despite this, installation of ACC would still be economically viable for those TPPs that are susceptible to at least 1 month of shutdown annually due to water shortages. On an average, Indian plants that are located at high water-stressed regions operate 1.5 months lesser than those at low and medium water-stressed regions. Such TPPs would see an increase in cost of electricity generation by 0.17 INR/kWh (0.24 US cents/kWh) compared to TPPs with ACC. [ABSTRACT FROM AUTHOR]

• Theoretical and experimental study of natural-draft wire-on-tube condensers. • Semi-empirical correlation to predict the air-side heat transfer coefficient. • Tube and wire pitch es play the most important role in the heat transfer rate. • Condenser optmization focused on reducing the material mass. This paper investigates the heat transfer performance of natural draft wire-on-tube condensers considering the geometric range of current designs adopted by the household refrigeration industry. Fifty-four samples with distinct geometries were manufactured and tested inside a standardized climate chamber that sets the air-side conditions, while a purpose-built apparatus was used to circulate hot brine through the coil with a strict control of the inlet temperature and mass flow rate. The results pointed out that the condenser height, and the wire and tube pitches are the key parameters affecting the heat transfer rate. An improved correlation was put forward to calculate the air-side heat transfer coefficient, being able to predict 90% of the experimental data within the ±10% error bounds. Also, it was noticed that the condenser design can be optimized by reducing the wires and tubes mass for a given heat duty. [ABSTRACT FROM AUTHOR]

The power consumption of axial flow fans may account for more than 1% of the rated power output of the power generating unit, so it is of benefit to the energy efficiency of the power generating unit to propose an operation adjustment approach to axial flow fans. On the basis of representative 2 × 600 MW direct dry cooling generating units, a computational model of air‐side flow and heat transfer of an air‐cooled condenser (ACC) combined with exhaust steam condensation is developed, by which the airflow rate, inlet air temperature of ACCs, the power consumption of axial flow fans, turbine backpressure, and net power output of power generating units at various wind speeds and in various wind directions are obtained. The results show that the net power output in the presence of winds always decreases when the rational speeds of the first upwind row axial flow fans increase from the rated speed of 79 rpm by 10% to 86.9 rpm. However, the net power output will increase in various wind directions if the rational speeds of all the fans except the upwind first row fans increase to 86.9 rpm. This can contribute to the optimal operation of the ACC by rotational speed adjustment of axial flow fans. [ABSTRACT FROM AUTHOR]

Many economic and environmental restrictions have resulted in the growth of dry cooling technology. The air-cooled condenser (ACC), which can be used in power plants and other facilities, represents a way toward the minimisation of the water footprint. In the paper, a semi-empirical computational tool devised for the design and thermal assessment of the ACC is introduced. In comparison to commonly used CFD-based models, the presented tool is computationally effective and inexpensive. The model is based on a control-volume computational grid, which is coupled with three sub-models for the solution of steam-side, air-side, and fan-related phenomena. A number of empirical correlations collected in the literature review were incorporated in the model. Besides the underlying functionality, which includes the determination of the steam condensation capacity, the model allows for the consideration of advanced physical phenomena such as the condensate glut control and the influence of air in the steam to the condensation process. The comparison of the model with datasheets from manufacturers of ACCs as well as with experimentally gained data from a municipal solid waste incineration plant demonstrates that the semi-empirical model is a fast and accurate tool applicable for the design and thermal assessment of the ACC. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Energy and exergy efficiencies of the plant are 12.88% and 48.20%, respectively. • Efficiencies are higher than other plants with similar specific geofluid exergies. • Improvement potential analysis for each component in the cycle is evaluated. • Turbine-I has the highest exergy destruction ratio of 201,776 $/yr. • SUCP of the plant increases over 40% as the ambient temperature varies 30 °C. The thermodynamic and thermoeconomic performances of a 21 MW geothermal power plant with air-cooled two level binary type organic Rankine cycle was numerically investigated based on its design and operating data. The investigated plant is the Sinem Geothermal Power Plant in Germencik, Aydin, Turkey. The paper provides a detailed comparison of the exergetic performance of this plant with other eight similar type of plant units, which make use of geothermal resources with similar specific exergies. Results indicate that the exergetic efficiency of the Sinem Geothermal Power Plant is the highest with 48.2% and the others vary between 9.6% and 42.7%. This result is mainly related to the exergy losses due to suppression of heat transfer in this plant, via low temperature brine reinjection, small temperature difference in the heat exchangers and high efficiencies of the individual components. First and second law efficiencies, as well as the exergy losses and improvement potentials of each component in the plant are also calculated. In air-cooled geothermal power plants, since ambient temperature is a critical parameter for the plant performance, both thermal and economic analysis of the plant is performed based on variation in ambient air temperature. Specifically, thermoeconomic analysis of the plant is evaluated to determine the exergoeconomic factor, the relative cost difference and the sum unit cost of the product (SUCP) of the plant. The effect of ambient temperature on the SUCP of the power plant, power generation, energy and exergy efficiencies are also examined in the present study. The results showed that; when the ambient temperature increases from 5 °C to 35 °C the reduction in power generation is 6.8 MW, energy efficiency decreases from 13.7% to 9.2% while exergy efficiency decreases from 54.9% to 36.7 and SUCP of the plant increases from nearly 230 $/GJ to 330 $/GJ. [ABSTRACT FROM AUTHOR]

• A conjugate heat transfer model is applied to finned-tube steam condensers. • Both the incomplete/complete condensations are considered. • The in-tube heat transfer and film behaviors are quantitatively studied and compared. • The presented model allows for the improved design and operation of condensers. Considering both the incomplete and complete condensation, a conjugate-model-based approach is developed to characterize the distributed thermodynamic development inside finned tube condensers. Applied to an engineering oval finned tube, the approach verifies the in-tube flow pattern as annular and river in incomplete and complete condensation respectively; furthermore, quantifies and compares the varying characteristics of cooling wall temperature, condensation heat flux, condensation HTC, film thickness, wall shear in the two condensation. In incomplete condensation, the condensation HTC increases slowly with the condensation approaching, unaffected by the steam quality, or film Reynolds number. With regarding complete condensation, an immediate decline of cooling wall temperature, and condensation heat flux and HTC is observed at the end of condensation, one easy-freezing location is marked for the safety operation of condensers, and the backflow of air is found at the vapor outlet. Concerning the phase change section, due to a much lower cooling wall temperature, the complete condensation provides a much greater condensation heat flux, but a nearly equivalent condensation HTC, as comparing to the incomplete mode. The approach is beneficial in designing an enhanced finned tube and operating a field condenser efficiently. [ABSTRACT FROM AUTHOR]

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.

Axial flow fans play key roles in the thermo-flow performance of direct dry cooling system under windy conditions, so the energy efficiency of a power generating unit can be improved by optimizing the operation strategies of the axial flow fans. In this work, various measures based on the partition adjustment of axial flow fans with constant power consumption of a 2 × 660 MW power plant are studied by computational fluid dynamics (CFD) methods. The results show that increasing the rotational speed of the windward fans is beneficial to reduce the inlet air temperature and increase the mass flow rates of the fans, which enhance the heat rejections of the air-cooled condensers, especially at high wind speeds. Moreover, the turbine back pressures for the optimal and original cases are achieved by iterative methods, with the largest drop of 2.77 kPa at the wind speed of 12 m/s for 110-case 3 in the wind direction of −90°. It is recommended to adopt 110-case 1 and 110-case 3 at low and high wind speeds, respectively, in the wind directions of 90° and −90°, while 110-case 2 is always the best choice in the 0° wind direction.

Sales of air conditioning are growing rapidly in buildings, more than tripling between 1990 and 2016. This energy use for air conditioning comes from a combination of rising temperatures, rising population and economic growth. Energy demand for climate control will triple by 2050, consuming more energy than that currently consumed altogether by the United States, the European Union and Japan. This increase in energy will directly impact water consumption, either to directly cool a condenser of an equipment or to serve indirectly as a basis for energy sources such as hydroelectric power that feed these heating, ventilation and air conditioning (HVAC) systems. Knowing the unique and growing importance of water, a new index, Total Water Impact (TWI) is presented, which allows a holistic comparison of the impact of water use on water, air and evaporative condensation climate systems. 200 and 500 TON (tons of refrigeration) air-cooled and water-cooled systems are theoretically compared to evaluate the general water consumption level. The TWI index is higher in the smallest water condensing system. That is, holistically, water consumption is higher in the water condensing system than in the air condensing system. Thus, this index provides a new insight about energy consumption and ultimately, about sustainability.

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Water spray cooling is an efficient way to enhance heat transfer of the air-cooled condenser (ACC) of power generating unit under high ambient temperatures. Taking the air-cooled 300 MW power generating unit as object, the flow and temperature fields of ACC with water spray cooling were analyzed by numerical simulation with experimental validation. Based on the air flow field inside ACC cell, an improved water spray nozzles arrangement was proposed to enhance the cooling capacity. The inlet air temperature and back pressure of turbine were compared with that under the original nozzles arrangement. The water consumptions including that of water droplets pre-cooling evaporation in air flow, liquid film evaporation on the finned tube bundles, and drainage of redundant water were obtained. The influences of water spray rate, spray direction and nozzles distance on cooling performance were investigated. The results showed that the improved nozzles arrangement is expected to provide efficient cooling performance and significant reduction in back pressure of the objective power generating unit. The improved nozzles arrangement with upward spray direction and nozzles distance of 0.8 m can be applied to the design of water spray system in ACC. In addition, the obtained redundant drainage water under various ambient conditions provided the evidence for spray water rate optimization. [ABSTRACT FROM AUTHOR]

Solar-driven desalination is a potential solution to the problem of freshwater scarcity in many parts of the world. However, this technology requires considerable efforts to overcome a number of technical challenges such as high-energy consumption, intermittency of solar radiation, and high-water consumption. This paper proposes an optimized multi-effect distillation (MED) process driven by steam at 70 °C and 0.3 bar, which is provided by a linear Fresnel collector. The aim of the proposed integrated system is to reduce the equivalent mechanical energy of the MED process, and utilize the most cost-effective storage system. Moreover, we incorporated an air-cooled condenser instead of a water-cooled condenser, to reduce the water cooling facilities. A computer model was developed using the Engineering Equation Solver tool, to solve the mass and energy balance equations of the integrated system (under different operating conditions). Under the operating conditions of Qatar, the simulation results showed that 1 m 2 of solar linear Fresnel collector produces 8.6 m 3 of freshwater per year. The equivalent mechanical energy of the optimized MED desalination plant is 8 kWh/m 3 , which is 59% lower than that of existing commercial MED facilities with thermal vapor compression (19 kWh/m 3 ). This significant reduction in equivalent energy consumption would reduce the required solar field size by 25%. This study also showed that using a water storage system (instead of thermal energy storage) results in a lower total system capital cost. Furthermore, by integrating an air-cooled condenser, the overall plant water consumption reduced by 2 m 3 of sea water per m 3 of feed water. The performance of the air-cooled condenser can vary by as much as 300% due to fluctuations in dry-bulb temperature and relative humidity. [ABSTRACT FROM AUTHOR]

Ambient winds may deteriorate the thermo-flow performances of air-cooled condenser (ACC) in power plants, so it is of benefit to the energy efficient operation of ACC to propose measures against adverse wind effects. In this work, the air deflectors installed under the fan platform of ACCs are proposed on the basis of a 2 × 300 MW direct dry cooling power plant. The flow and temperature fields of cooling air are obtained and analyzed for the air deflectors with various geometric parameters. The air mass flow rate and turbine back pressure are computed and compared with the original ACCs. The results show that the thermo-flow performances of ACCs are significantly influenced by the width, pitch, inclination angle and number of air deflectors, and get improved due to the restrained reverse flows in windward condenser cells. In most cases, the wide and more air deflectors are preferred, but the moderate pitch is recommended to improve the ACC performances. Moreover, the 45° inclination of air deflectors is superior to others in restraining the adverse wind effects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Adverse wind effects on the thermo-flow performances of air-cooled condensers (ACCs) can be effectively restrained by wind-proof devices, such as air deflectors. Based on a 2 × 300 MW coal-fired power generation unit, two types (plane and arc) of air deflectors were installed beneath the peripheral fans to improve the ACC’s cooling performance. With and without air deflectors, the air velocity, temperature, and pressure fields near the ACCs were simulated and analyzed in various windy conditions. The total air mass flow rate and unit back pressure were calculated and compared. The results show that, with the guidance of deflectors, reverse flows are obviously suppressed in the upwind condenser cells under windy conditions, which is conducive to an increased mass flow rate and heat dissipation and, subsequently, introduces a favorable thermo-flow performance of the cooling system. When the wind speed increases, the leading flow effect of the air deflectors improves, and improvements in the ACC’s performance in the wind directions of 45° and −45° are more satisfactory. However, hot plume recirculation may impede performance when the wind direction is 0°. For all cases, air deflectors in an arc shape are recommended to restrain the disadvantageous wind effects.

The thermo-flow performances of air-cooled condensers (ACCs) are basically deteriorated under wind conditions, so it is of great concerns to propose the measures against the adverse wind effects on air-cooled condensers. In this work, a novel reconstruction of ACCs combined the V-frame condenser cells with the induced axial flow fans, and a modified layout of the novel ACCs for a specific wind direction are proposed based on the direct dry cooling system in a 2 × 600 MW power plant. The CFD approach with a validation is applied to the performance investigation of the novel ACCs. The variable fields, mass flow rate, inlet air temperature and turbine back pressure for both the conventional and novel layouts of ACCs under different wind conditions are obtained and compared. The results show that the mass flow rates of the novel ACCs increase conspicuously compared with the conventional ACCs both in the absence and presence of winds. The flow distortions through the induced axial flow fans are greatly restrained and the inlet air temperature of the novel ACCs decreases, which lead to the improved thermo-flow performances of ACCs and reduced turbine back pressure of power generating unit. [ABSTRACT FROM AUTHOR]

Natural draft direct dry cooling system (NDDDCS) uses the natural draft dry-cooling tower instead of axial flow fans, so can effectively reduce the power consumption, operating costs and also the noise caused by fans. In this work, two types of NDDDCS with horizontally arranged heat exchanger bundles (HAHEBs) and vertically arranged heat exchanger bundles (VAHEBs) are proposed respectively. Furthermore, the cooling delta apex angles from 60° to 180° are further investigated. The air-side velocity, pressure and temperature fields are presented and the heat rejections for various configurations of NDDDCS are calculated and compared. The results show that the cooling performance of NDDDCS with VAHEBs is superior to that with HAHEBs in any case, especially at high wind speeds. The VAHEBs with the apex angle of 150° have the best cooling performance, so can be recommended in the potential practical engineering of natural draft direct dry cooling system in power plants. [ABSTRACT FROM AUTHOR]

An updraft tower cooling system is assessed for elimination of water use associated with power plant heat rejection. Heat rejected from the power plant condenser is used to warm the air at the base of an updraft tower; buoyancy-driven air flows through a recuperative turbine inside the tower. The secondary loop, which couples the power plant condenser to a heat exchanger at the tower base, can be configured either as a constant-pressure pump cycle or a vapor compression cycle. The novel use of a compressor can elevate the air temperature in the tower base to increases the turbine power recovery and decrease the power plant condensing temperature. The system feasibility is evaluated by comparing the net power needed to operate the system versus alternative dry cooling schemes. A thermodynamic model coupling all system components is developed for parametric studies and system performance evaluation. The model predicts that constant-pressure pump cycle consumes less power than using a compressor; the extra compression power required for temperature lift is much larger than the gain in turbine power output. The updraft tower system with a pumped secondary loop can allow dry cooling with less power plant efficiency penalty compared to air-cooled condensers. [ABSTRACT FROM AUTHOR]

In the present paper, a system is proposed for improving the performance of steam power plant with air-cooled condenser during peak loads. In this system, the power plant comprises two steam turbines, and the air-cooled condenser is replaced by two condensers. The first one is air-cooled (dry) and used for condensing the exhaust steam of the first turbine, while the second is water-cooled and serves to condense the steam outlet of the second turbine. The warm cooling water exiting the wet condenser is pumped to a cooling storage container, where it is cooled and re-circulated to the wet condenser. Cooling is produced by a refrigeration machine driven by the extra electric power generated by the two turbines during the time of the off-peak-loads (low electricity rates). Simple energy analyses have been developed to predict the energy characteristics of this system. The results of this paper showed that the proposed system leads to improving the plant power output at peak-loads. About 6, 16, 24 and 33% increase in generated plant power can be achieved at peak-loads (high electricity rates) when the ambient temperature is 20, 30, 40 and 50°C respectively, and the whole steam exiting both turbines is cooled in a wet condenser to a design temperature of 20°C. The results showed also that choice of the capacity of each turbine is essentially affected by the quality of the refrigeration machine and ambient temperature.