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The use of wickless heat pipe heat exchangers has been improving a wide range of thermal applications such as solar water heaters. Therefore, more scientific research needs to be conducted to improve its performance. In the present study, a wickless heat pipe heat exchanger test rig has been designed and fabricated to investigate the effect of different parameters on its performance. Two different heat pipe working fluids have been used namely pure water and water with nanoparticles (Al2O3) using different fluid volume ratios (20%,40%,60%,80%, and 100%). The concentrations of the nanoparticles in water range between 1.3 and 7 % wt. For the heat exchanger, various inlet hot air temperatures (50, 55, and 60 ℃) have been tested at the hot side (heat pipe evaporator) whereas the inlet temperature of the cold side (heat pipe condenser) has been maintained at 20 ℃. The effect of airflow Reynolds number has also been examined with a range of 2583-20664. Results showed that the best heat exchanger effectiveness is achieved at a Reynolds number of 10332 and nanoparticles concentration of 7% wt. Also, the use of nanoparticles reduced the thermal resistance in the heat pipe due to the significant reduction in its surface temperature compared to that of pure water. [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]

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical tool used in modern science and technology. Its novel incarnation, based on measurements of NMR signals without external magnetic fields, provides direct access to intramolecular interactions based on heteronuclear scalar J-coupling. The uniqueness of these interactions makes each zero-field NMR spectrum distinct and useful in chemical fingerprinting. However, the necessity of heteronuclear coupling often results in weak signals due to the low abundance of certain nuclei (e.g., 15N). Hyperpolarization of such compounds may solve the problem. In this work, we investigate molecules with natural isotopic abundance that are polarized using non-hydrogenative parahydrogen-induced polarization. We demonstrate that spectra of hyperpolarized naturally abundant pyridine derivatives can be observed and uniquely identified whether the same substituent is placed at a different position of the pyridine ring or different constituents are placed at the same position. To do so, we constructed an experimental system using a home-built nitrogen vapor condenser, which allows for consistent long-term measurements, crucial for identifying naturally abundant hyperpolarized molecules at a concentration level of ~1 mM. This opens avenues for future chemical detection of naturally abundant compounds using zero-field NMR. Zero- and ultralow-field (ZULF) nuclear magnetic resonance (NMR) has emerged as a complementary technique to conventional high-field (≳1 T) NMR, however, the ability to distinguish heteronuclear coupling remains challenging due to the low abundance of certain nuclei. Here, the authors apply non-hydrogenative parahydrogen-induced hyperpolarization to identify naturally abundant molecules, and demonstrate the detection of pyridine derivatives at a concentration level of ~1 mM. [ABSTRACT FROM AUTHOR]

Radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor. This effect has been known for centuries, and is exploited by some insects to survive in dry deserts. Humans have also been using radiative condensation for dew collection. However, all existing radiative vapor condensers must operate during the nighttime. Here, we develop daytime radiative condensers that continue to operate 24 h a day. These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy. Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies. [ABSTRACT FROM AUTHOR]

This research presents a novel Extended Thermodynamic Analysis Method(ETAM)to respond to the issue of which equipment holds the highest priority of receiving improvements in a thermodynamic cycle'. This novel analysis comprises three parts: extended energy, extended entropy, and extended exergy analyses. As a case study, a low-temperature geothermal Kalina cycle system-34 was analyzed. The results of Conventional Exergy Analysis Method (CEAM), Advanced Exergy Analysis Method(AEAM), and the proposed novel method were compared with each other. CEAM results indicate that the condenser, followed by the evaporator and turbine, has the most exergy destruction. In contrast, according to AEAM results, the top priority for improvement should be given to the condenser, followed by turbine and Low-Temperature Recuperator(LTR). The improvement priority using the presented novel extended analysis was also given to the condenser, turbine, and LTR, the finding being the same as the results of AEAM, while the proposed novel method is less complicated than the AEAM. [ABSTRACT FROM AUTHOR]

This study concerns the numerical simulation and the experimental implementation of a low-scale Phase Change Material-based (PCM-based) condenser, to be included in a PCM-based portable cooling systems. In this category of cooling systems, the PCM can be integrated either in the condenser or in the evaporator. In the present study, the PCM is integrated in the condenser of the vapor compression cycle to absorb the heat power released from the refrigerant fluid (R134a) during condensation, thus eliminating the need to transfer heat to the external environment. The main objective of the present study is to realize and validate a numerical model capable of simulating both the refrigerant fluid and the PCM thermofluid dynamics. For this purpose, a commercial solver was used for the implementation of the developed numerical model, and experimental tests were performed to validate the numerical simulations results. The paper reports the details and test results of both the numerical model and the experimental apparatus. The simulation results indicate a good accordance between the numerical and experimental data. [ABSTRACT FROM AUTHOR]

The rise of large-scale HVDC transmission technology has introduced new requirements for dynamic reactive power compensation in power systems. The new generation of synchronous condensers is independent of grid voltage and does not need to be dragged by a coaxial prime mover, which can improve the dynamic reactive power compensation of the power grid. This new generation of synchronous condensers is dragged by the static frequency converter to a 105% rated speed, after which the static frequency converter logs out. In the process of idling, the excitation mode switching is completed and the unit is connected to the grid simultaneously. The synchronous device passively captures the connection-dot in the process of idling; as a result, increasing the grid-connection success rate and reducing the impact of grid connection become a pair of contradictions. In this paper, the boundary conditions of the new generation of synchronous condenser grid-connection systems are analyzed. These provide the basis for setting the synchronous device parameters. Furthermore, this paper proposes an optimized grid-connection strategy to ensure the new generation of synchronous condensers possesses good grid-connection characteristics. [ABSTRACT FROM AUTHOR]

Two-phase flows are found in almost all areas of technology. For example, tubular evaporators, boiling water reactors, boiler blowdown systems, heaters, boilers, gas lift pumps, oil and geothermal wells, oil and gas pipelines, refrigerators, process pipelines, and condensers. Two-phase flows are classified as mixtures. According to the composition of the mixture are divided: (a) for single-component (or one-component) - vapor-liquid flows; (b) multicomponent - gas-liquid flows. One-component mixtures consist of the same substance in different states of aggregation. This can be not only vapor-liquid, but also a mixture of liquid or vapor with a solid phase, a water-ice mixture, or a vapor flow with ice particles, for example, in sublimation installations. Multicomponent mixtures are a combination of substances of different physical nature. These include not only gas-liquid flows, but also, for example, mixtures of air and sand, water and oil. The paper presents the main attention is paid to the movement of two-phase flows in the pipeline. [ABSTRACT FROM AUTHOR]

A brand new method of inhibiting corrosion and scale deposits on the surface of evaporative condensers, which consists in packing inhibitor molecules in capsules of chelated compounds, is proposed and implemented. Encapsulation of the inhibitor can increase the effectiveness of a wide range of corrosion inhibitors in preventing metals corrosion. [ABSTRACT FROM AUTHOR]

Making use of two different analytical–numerical methods for capacity computation, we obtain matching to a very high precision numerical values for capacities of a wide family of planar condensers. These two methods are based respectively on the use of the Lauricella function (Bezrodnykh and Vlasov, 2002; Bezrodnykh, 2016 [64,65]) and Riemann theta functions (Bogatyrëv, 2012; Grigoriev, 2013; Bogatyrëv and Grigor'ev, 2017; Bogatyrëv and Grigor'ev, 2018). We apply these results to benchmark the performance of numerical algorithms, which are based on adaptive h p -finite element method (Hakula et al. 2011, 2013, 2018) and boundary integral method (Tsuji, 1959; Jaswon and Symm, 1977; Albrecht and Collatz, 1980). [ABSTRACT FROM AUTHOR]

The short circuit response of voltage source converters (VSCs) could be significantly different from that of synchronous condensers (SCs) under unbalanced faults. This paper investigates the combined effect of VSC-based sources and synchronous condensers under grid unbalanced faults considering two groups of VSC fault-ride-through control strategies. It aims to provide an evaluation of typical control strategies and to explore the impact of equipping a synchronous condenser at the point of common coupling (PCC). By examining the combined short-circuit currents, PCC voltages, DC-side voltages, and system frequency responses, this study points out the merits and demerits of the examined control strategies, illustrates the benefits of synchronous condensers on mitigating the disadvantages of certain control strategies, and provides suggestions on selecting the control strategies for the VSC when incorporating a synchronous condenser at the PCC. [ABSTRACT FROM AUTHOR]

• A parametric analysis of a shell-and-tube-surface condenser is performed. • Results are adjusted by an ANFIS for its design and evaluation under other conditions. • The use of ANFIS shows advantages over other traditional approaches such as the EES. • Results were compared with the EES and the error is lesser than 10%. Surface condensers are among the widest equipment used in various industrial sectors as well as in power plants. One of the most common types of surface condensers is shell and tube heat exchangers which are robust and easy to use in multifold environments. On the other hand, adaptive neuro-fuzzy inference systems (ANFIS) are widely used in many engineering applications such as healthcare services, production management, quality control, emergency responses, traffic control and so on. In the current study, a shell-and-tube-surface condenser is represented by a phenomenological model and a parametric analysis of the operational and geometric variables is performed. These results are adjusted by an ANFIS in order to enable a systematic tool that allows the design and evaluation of the equipment under other operating conditions. The use of ANFIS to evaluate the operation of a surface condenser or to make a previous design based on certain operating conditions demonstrates advantages over the use of traditional approaches such as the Engineering Equation Solver (EES) because the use of fuzzy rules offers a high combinatorial option in the analysis that joint with the possibility of learning of neural networks allow to obtain a reliable and easy application tool to quickly achieve the desired results within a planned range of operation and design, being possible, in addition, to change the ranges of the input variables without needing to do calculations, only reusing the tool obtained with different data, depending on the conditions of the process in question. The results obtained were compared with a conventional evaluation tool (EES) and the percentage error when comparing both approaches is lesser than 10%, which demonstrates the validity of the neuro-fuzzy system proposed. [ABSTRACT FROM AUTHOR]

The study explores the thermal-hydraulics parameters of a condenser of a nuclear power plant with 1200MWe net electric output and 37% thermal efficiency using empirical correlations of pressure drop and heat transfer coefficient both for the tube and shell sides. Considering a two-phase fluid system, a shell and tube condenser with coolant water on the tube side and condensing steam on the shell side has been selected. For designing a condenser with a thermal load of 2060MWth, the input temperature data of cold fluid inlet and outlet temperatures are taken as 29.4°C and 40°C while the condensation temperature is taken as 53.97oC. Transverse, two-pass condenser with 4 shell tanks has been considered in this study and the length of each shell tank is taken as 14m. Based on these input data, this work finds heat transfer area, logarithmic mean temperature difference (LMTD), and convection heat transfer coefficient inside the tubes as 549536m², 18.74°C, and 2869.85W/m².°C respectively for 20mm tube outer diameter. Hydrodynamic parameters relating to the friction factors and pressure drops on tube side are found as 0.031 and 14.86kPa respectively. Similar design data have been generated for varying coolant inlet temperatures and tube inner diameters. Results reveal that velocity of flow inside the tubes as well as the number of tubes in a bundle decrease with the increase in tube diameter. Finally, the thermal-hydraulic data may be used to design a large scale commercial condenser to be applicable for a large scale nuclear plant since limited design data are available in the literature. [ABSTRACT FROM AUTHOR]

The object of this research was to investigate of the energy performance of a national chicken slaughterhouse in order to achieve condenser heat utilization generated by the operation of the existing, refrigerant systems. The paper focuses also for the technical realization of condenser heat utilization by concept plans and payback time calculations. The utilizing heat of a cooling circle's condenser is a quite quickly returnable investment. The time of payback is around 330 days by heat utilizing for hot water preheating and also air heating. [ABSTRACT FROM AUTHOR]

• The designs of vapor-recompression distillation columns for the ethylene-ethane separation with high or low pressures in the auxiliary condenser are compared. • High pressure reduces refrigeration cost in the condenser but increases compressor cost. • The high-pressure design has 11% lower total energy cost but requires more capital investment. • The return on investment is quite attractive. A recent paper studied the separation of ethylene and ethane using several types of distillation systems in which cryogenic cooling is required. The economics of a conventional column using a very low-temperature expensive refrigerant in the condenser were compared with several configurations using process compressors. The alternative configurations involve the pressure in the auxiliary condenser and the fraction of the column overhead vapor sent through the compressor. Low pressure in the condenser requires a very low-temperature expensive refrigerant but has lower compressor costs. The purpose of this paper is to show that all of the vapor from the column should be compressed and then split, with some going to the reboiler and the rest going to an auxiliary condenser that operates at high pressure so that a higher-temperature less-expensive refrigerant can be used. [ABSTRACT FROM AUTHOR]

• We describe an equation-oriented parallel column model for simulation of Dividing Wall Columns. • The model can simulate DWCs of arbitrary configuration. • The model is verified by comparing results to those obtained from multi-column models. • The parallel column model converges quickly. Dividing Wall Columns (DWC) have attracted considerable attention in recent years. It is often stated that no commercial flowsheet simulation package has yet offered a DWC as a standard model. As a result, nearly all simulations of DWCs employ interlinked multi-column equilibrium stage models in a sequential-modular process simulator. It is claimed that equation-based simulators offer advantages over sequential modular simulators when modelling DWCs but, to date, no empirical evidence in support of such a contention has been published. In this paper we describe an equation-based parallel column model (PCM) designed to enable the straightforward simulation of an entire DWC as though it were a single column. With the aid of simulations of several different DWCs with one, two, or three walls, and with one or two condensers, we demonstrate that an equation-oriented PCM can have good numerical performance, arguably superior to sequential-modular multi-column models. [ABSTRACT FROM AUTHOR]

Abstract The prototype system of integrated anaerobic filter with condenser of air conditioner (anaerobic filter-condenser; ANCO) was developed for sustainable water-energy management model in green office building. The ANCO consists of an insulated anaerobic filter (IAF) and condenser that are connected to an existing refrigerant of air conditioner. The system applied waste heat energy from an air conditioner to improve wastewater treatment efficiency. While the performance of air conditioner also could be enhanced by decreasing refrigerant temperature from transferring waste heat through the IAF system for increasing wastewater temperature. The waste heat from air conditioner could stimulate higher microbial activity in the IAF and at the same time, this could increase air conditioner performance. From the overall results, it was found that with wastewater flow rate 180 liter/day, the ANCO prototype could recycle waste heat approximately 2.82 kWh/day. The waste heat transferred into wastewater could increase water temperature up to averagely 35.4 °C. The system performance for removal of suspended solids (SS) and COD were averagely 49.9% and 49.3%, respectively. The coefficient of performance (COP Overall) of air conditioner was increased by 30.25% and electric consumption was decreased by 22.96%. The ANCO system could save electrical energy averagely 2.62 kWh/day. Then, the ANCO system can decrease heat into environment and decrease greenhouse gas emission 602 kgCO 2 eq/year. Therefore, the ANCO system was pronounced to be the prototype eco-friendly onsite-wastewater treatment system for green office building application. Highlights • The novel prototype of combined anaerobic filter-condenser system (ANCO) has been developed in this research. • The ANCO system uses waste heat for wastewater treatment and also uses wastewater to increase air conditioner performance. • The prototype ANCO system could recycle waste heat from air conditioner at 2.82 kWh/d for wastewater flowrate of 180 L/d. • COP Overall of air conditioner in the ANCO system was increased to 30.25% and electric consumption was decreased by 23.14%. [ABSTRACT FROM AUTHOR]

The R245fa condensation heat transfer is investigated in a phase separation shell-tube condenser with mesh tubes inserted. The condenser has three copper tubes which have an inner diameter of 14.70 mm and a heat transfer length of 1600 mm. Four mesh tubes with mesh pore width of 15 μm are arranged in each copper tube. The comparative experiments are conducted for condensers with or without mesh tubes inserted. The flow pattern visualization is investigated to explore heat transfer enhancement mechanisms. The results showed that, with vapor mass qualities and mass fluxes increased, condensation heat transfer coefficients and friction pressure drops are increased, but heat transfer enhancement ratios and performance evaluation parameters are decreased. At low mass fluxes, the heat transfer coefficients behave a slow decrease trend with increase of inclination angles. The pressure difference between annular region and core region drives liquid flow towards core region, reducing liquid film thickness on tube bottom and increasing vapor void fractions near tube wall. With increase of inclination angles, the pressure difference is reduced but liquid film thickness on tube bottom is increased. For horizontal flow, there is an optimal match between pressure difference of annular region and core region and liquid-mesh tube contact area. Under such circumstance, the heat transfer enhancement ratios reach maximum. [ABSTRACT FROM AUTHOR]

[Display omitted] • The iceberg shape like condenser can efficient collect vapor in hot weather. • The introduction of a TG between photothermal and evaporation layer can decrease heat loss. • Excellent durability performance in solar steam desalination. • This ISWG may pave the way for industrial desalination. Interfacial solar steam generation has emerged as a promising eco-friendly and low-carbon emission technology to address the global water scarcity. So far, the majority of attention is paid to the improvement of the evaporation rate while the efficient vapor collection sector remains broadly unexploited. Herein, an inverted iceberg-inspired solar water generator (ISWG), consisting of a thermoelectric generator coated by a photothermal agent, a bilayer all-fiber nonwoven fabric and a passive cooling vapor condenser, is constructed. Inspired by the shape of an iceberg, the majority of the ISWG system is underneath the bulk water, leaving only the evaporation section floating on the water. This ISWG system not only avoids the vapor condensation induced solar input loss, but also transfers the heat to the surrounding bulk water, resulting in passive cooled and enhanced vapor collection. Moreover, a thermoelectric generator, which utilizes the temperature difference between the photothermal layer and evaporation layer, is sandwiched for thermal conduction in place of the traditional metal plate. The ISWG can achieve a high vapor collection rate of 1.02 kg m-2 h−1 and extra output electricity with a power of 0.47 W m−2 under sunlight with the ambient temperature at about 42 ℃. This work may pave the way for the development of an efficient solar-induced water-electricity co-generation system in tropical islands. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the impact of moving the condenser of a household refrigerator within the body on the refrigerator's performance and energy consumption. The effects of the internal and external condensers on energy consumption and cooling capacity in a household refrigerator are next explored. This study was conducted experimentally and in a laboratory setting, and all terms and conditions were in accordance with the international electrotechnical commission 62552-2015 for cooling system testing. The studies were conducted in a 5- foot refrigerator. On this refrigerator, both internal and external condenser models were installed. In the first situation, the internal condenser was inserted into the cooling cycle and the associated tests and calculations were performed. In the other situation, the internal condenser was removed from the cooling cycle and the external condenser was replaced by changing the valve status. In this case, the relevant diagrams and calculations were obtained and analyzed. Based on the findings of this study, it can be stated that using the internal condenser reduces energy consumption and, as a result, has a higher energy grade than using the external condenser. The internal condenser in the heat transfer process work better than the external condenser, based on the temperatures obtained. An internal condenser is also a preferable solution for a household refrigerator in terms of installation and cost. [ABSTRACT FROM AUTHOR]

Transport Membrane Condenser (TMC) is a promising technology that works based on the capillary condensation property of the nano-scale ceramic porous membrane materials and can recover both waste heat and water in various industrial applications. For applications with high volume flow rate such as in power plants, a large number of TMC heat exchangers are required, which highlights the importance of the optimum design for the TMC exchangers in order to obtain the maximum heat transfer and minimum cost of the TMC heat exchanger unit. In this paper, the effects of different tube spacing and the inlet water vapor mass fraction on the overall performance of a membrane-based heat exchanger have been studied numerically using a combined condensation model based on the capillary condensation and condensation on a solid wall. The results were obtained in terms of the Euler number, dimensionless volumetric heat transfer density, and contours of the water mass fraction and temperature distribution inside the TMC heat exchanger. [ABSTRACT FROM AUTHOR]

Several alternative process equipment configurations have recently been proposed to replace the conventional two-column extractive distillation process. One interesting configuration features a single column with a divided wall running from the stripping section all the way two the top of the column. There is only one reboiler at the base of the column, but each of the segregated upper sections has its own independent condenser, reflux and distillate product. The vapor split at the bottom of the wall is fixed at design by the location of the wall. Steady-state economic advantages are claimed over the conventional two-column process. However, the dynamic controllability of this process is in question because the loss of the ability to manipulate the vapor split reduces the number of control degrees of freedom. The purpose of this paper is to propose a new control structure that avoids this loss of control flexibility by manipulating the pressures on the two sides of the wall. [ABSTRACT FROM AUTHOR]

Micro-condenser using the phase separation concept was investigated in this paper. Lined pin fin arrays generate liquid passages and vapor passages alternatively in chip width direction. The decreased Gibbs free energy with gas–liquid interface advancing pin fin throat location is the mechanism to induce liquid flow from vapor passages to liquid passages. The decreased energy dissipation due to decreased interfacial area between the two phases accounts for pressure drop reduction. Three micro-condensers were investigated: microchannel condenser (SWM), parallel phase separation condenser (PPS with constant cross sections of fluid passages) and conical phase separation condenser (CPS with varied cross sections of fluid passages). Micro-condensers had identical project condensation surface of 25.0 mm by 3.0 mm. The etched depth was 75 μm. Water-vapor was the working fluid. Compared with SWM, phase separation condensers increased mass flow rate by 15% at similar pressure drops. PPS condenser enhances heat transfer at moderate or smaller cooling intensity, but deteriorates heat transfer at large condensed liquid flow rate, at which over liquid expansion occurs to flood all pin fin side walls. CPS condenser self-adapts variations of flow rates of the two phases to stabilize vapor–liquid interface near pin fin membrane. Pin fin side walls facing vapor passage are covered by thin liquid film to eliminate over liquid expansion. CPS condenser enhances heat transfer over entire operating parameter ranges, increasing condensation heat transfer coefficients by 74% maximally while pressure drops are decreased. CPS condenser has the best performance among the three condensers. [ABSTRACT FROM AUTHOR]

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]

Growth of fine aerosol particles is investigated during the Aerosol-CCN-Cloud Closure Experiment campaign in June 2013 at an urban site near Beijing. Analyses show a high frequency (∼ 50%) of fine aerosol particle growth events, and show that the growth rates range from 2.1 to 6.5 nm h−1 with a mean value of ∼ 5.1 nm h. A review of previous studies indicates that at least four mechanisms can affect the growth of fine aerosol particles: vapor condensation, intramodal coagulation, extramodal coagulation, and multi-phase chemical reaction. At the initial stage of fine aerosol particle growth, condensational growth usually plays a major role and coagulation efficiency generally increases with particle sizes. An overview of previous studies shows higher growth rates over megacity, urban and boreal forest regions than over rural and oceanic regions. This is most likely due to the higher condensational vapor, which can cause strong condensational growth of fine aerosol particles. Associated with these multiple factors of influence, there are large uncertainties for the aerosol particle growth rates, even at the same location. [ABSTRACT FROM AUTHOR]

Free convection heat transfer over the outer surface of helical coil condenser (HCC) and existing wire-on-tube condenser (WOTC) in air was experimentally studied under steady-state conditions. Two types of condensers are tested: namely, helical coil condenser of different coil diameter to tube diameter ratio and an existing wire-on-tube condenser. The experiments were conducted for turbulent flow outside, the helical coil surface as well as, conventional wire-ontube condenser surface and comparative analysis was done. The experimental results show that decrease in diameter ratio as well as pitch leads to increase in outside heat transfer coefficient. The heat transfer coefficient was higher 12.42% outside for the helical coil condenser in comparison with the conventional wire-on-tube condenser. It was also observed that the COP of the domestic refrigerator with designed HCC is 12.77 % higher than existing WOTC. [ABSTRACT FROM AUTHOR]

• Main photothermal materials and relevant improvement strategies are summarized. • Methods for ISVG component enhancement are analyzed and reviewed. • Recent progress at system-level designed strategies is also summarized. • Issues and challenges of interfacial solar vapor generation are presented. Interfacial solar vapor generation has recently emerged as a promising technology because of its high solar evaporation efficiency and many studies have been conducted from multilevel, i.e., material level, component level, and system level. However, there is still a lack of timely and systematic review of these studies. Thus, this study provides a state of the art review regarding the multilevel designs of interfacial solar vapor generation. At the material level, the study reviews the developments of atomic/molecular-scale designs and nano/micro-scale designs. The atomic/molecular-scale designs mainly involve energy band adjustment and molecular engineering; while the nano/micro-scale designs mainly include material composition regulation and material structure adjustment. At the component level, the study mainly focuses on the fast developments of the key components, such as the water supplier, thermal insulator, ambient air and water, and vapor condenser, and their interactions. Regarding the system-level design strategies, the study reviews and analyzes the latest progress in integrating interfacial solar vapor generation with other functional systems for round-the-clock water production, water-related application, and co-generation of freshwater and electricity. In the end, the study discusses and states the challenges faced and future research directions of this technology, especially on its wide and large-scale applications. [ABSTRACT FROM AUTHOR]

An example of assessment of condenser casing strength taking account of extending the casing life 30 years beyond the design life is discussed. [ABSTRACT FROM AUTHOR]

Liquid separation condenser (LSC) is a newly developed fin-and-tube condenser. It is superior to other traditional condenser because of its relatively low pressure drop without reducing heat transfer coefficient. It is suitable to be used in the organic Rankine cycle. However, the design of LSC is a very complex and time consuming task base on traditional methods. In this study, a new modelling, simulation and optimization methodology for LSC design is developed. A pass-by-pass tube side modelling method is proposed. An equivalent heat transfer coefficient and total pressure drop are defined, modelled and validated. Then, a mathematical model containing multiple continuous and discrete variables for the optimal design of LSC is developed. The main continuous variables are tube length, pressure drops, fluid velocity, air velocity, heat transfer area, and outlet air temperature. The main discrete variables are the type selection of finned-tubes, number of passes, number of tubes per pass, fin number per unit tube length. The objective function is the minimization of the total cost, which is the best trade-off between the heat transfer coefficient and the pressure drop. The resulting model is a non-convex mixed integer non-linear programming (MINLP) model. A solving strategy that integrates model relaxation, solver selection, and tube-pass scheme initialization is proposed. Two case studies are elaborated to test the effectiveness of the proposed methodology. Comparison of the optimization results with base case reveals that the proposed methodology can be successfully applied to the design optimization of LSC. The influences of pass number, fin number, tube–fin type, tube number, and investment cost on the optimization results are also discussed. [ABSTRACT FROM AUTHOR]

The steam condenser is one of the most important element in whole power plant installation. Their proper design and operation makes a significant contribution to the efficiency of electricity production. The purpose of this article is to propose a 2-D mathematical model that allows modelling condenser work. In the model, the tube bundle is treated as a porous bed. The analysis has been subjected to a two passes power condenser with a capacity of 50 MW. The mathematical analysis was compared with the results of experimental studies. The average error between the model and the experiment for difference of cooling water temperatures was 5.15% and 11.60% for the first and second pass, respectively. This allows to conclude that the proposed model is good enough to optimize future work of the condenser [ABSTRACT FROM AUTHOR]

The diameter and configuration of tubes are important design parameters of power condensers. If a proper tube diameter is applied during the design of a power unit, a high energy efficiency of the condenser itself can be achieved and the performance of the whole power generation unit can be improved. If a tube assembly is to be replaced, one should verify whether the chosen condenser tube diameter is correct. Using a diameter that is too large increases the heat transfer area, leading to over-dimensioning and higher costs of building the condenser. On the other hand, if the diameter is too small, water flows faster through the tubes, which results in larger flow resistance and larger pumping power of the cooling-water pump. Both simple and complex methods can be applied to determine the condenser tube diameter. The paper proposes a method of technical and economic optimisation taking into account the performance of a condenser, the low-pressure (LP) part of a turbine, and a cooling-water pump as well as the profit from electric power generation and costs of building the condenser and pumping cooling water. The results obtained by this method were compared with those provided by the following simpler methods: minimization of the entropy generation rate per unit length of a condenser tube (considering entropy generation due to heat transfer and resistance of cooling-water flow), minimization of the total entropy generation rate (considering entropy generation for the system comprising the LP part of the turbine, the condenser, and the cooling-water pump), and maximization of the power unit's output. The proposed methods were used to verify diameters of tubes in power condensers in a200-MW and a 500-MW power units. [ABSTRACT FROM AUTHOR]

This study presents the design of a novel boil-off gas (BOG) re-liquefaction technology using a BOG recondenser system. The BOG recondenser system targets the liquefied natural gas (LNG) bunkering operation, in which the BOG phase transition occurs in a pressure vessel instead of a heat exchanger. The BOG that is generated during LNG bunkering operation is characterized as an intermittent flow with various peak loads. The system was designed to temporarily store the transient BOG inflow, condense it with subcooled LNG and store the condensed liquid. The superiority of the system was verified by comparing it with the most extensively employed conventional re-liquefaction system in terms of consumption energy and via an exergy analysis. Static simulations were conducted for three compositions; the results indicated that the proposed system provided 0 to 6.9% higher efficiencies. The exergy analysis indicates that the useful work of the conventional system is 24.9%, and the useful work of the proposed system is 26.0%. Process dynamic simulations of six cases were also performed to verify the behaviour of the BOG recondenser system. The results show that the pressure of the holdup in the recondenser vessel increased during the BOG inflow mode and decreased during the initialization mode. The maximum pressure of one of the bunkering cases was 3.45 bar. The system encountered a challenge during repetitive operations due to overpressurizing of the BOG recondenser vessel. [ABSTRACT FROM AUTHOR]

Vapor chamber technologies offer an attractive approach for passive heat spreading in mobile electronic devices, in which meeting the demand for increased functionality and performance is hampered by a reliance on conventional conductive heat spreaders. However, market trends in device thickness mandate that vapor chambers be designed to operate effectively at ultra-thin (sub-millimeter) thicknesses. At these form factors, the lateral thermal resistance of vapor chambers is governed by the saturation temperature/pressure gradient in the confined vapor core. In addition, thermal management requirements of mobile electronic devices are increasingly governed by user comfort; heat spreading technologies must be designed specifically to mitigate hot spots on the device skin. The current work considers these unique transport limitations and thermal requirements encountered in mobile applications, and develops a methodology for the design of vapor chambers to yield improved condenser-side temperature uniformity at ultra-thin form factors. Unlike previous approaches that have focused on designing evaporator-side wicks for reduced thermal resistance and delayed dryout at higher operating powers, the current work focuses on manipulating the condenser-side wick to improve lateral heat spreading. The proposed condenser-side wick designs are evaluated using a 3D numerical vapor chamber transport model that accurately captures conjugate heat transport, phase change at the liquid–vapor interface, and pressurization of the vapor core due to evaporation. A biporous condenser-side wick design is proposed that facilitates a thicker vapor core, and thereby reduces the condenser surface peak-to-mean temperature difference by 37% relative to a monolithic wick structure. [ABSTRACT FROM AUTHOR]

A conventional desorber in the Absorption Heat Transformer (AHT) cycle requires a constant heat flux and vacuum pressure conditions to boil the working mixture and separate the working fluid. In this paper, an Air Gap Membrane Distillation (AGMD) unit was adapted as desorber/condenser with water/Carrol mixture in order to demonstrate the feasibility of the desorption process at atmospheric pressure conditions. Two membranes with 0.22 and 0.45 μm pore sizes were used and three temperature levels were tested. The maximum increase in the concentration (Δ X ) was 1.54% w/w (from 60.63 to 62.17% w/w) with a membrane with pore size up to 0.45 μm and a solution temperature of 82.7 °C. The maximum thermal process effectiveness was 17.7% (on average) with a membrane with pore size up to 0.22 μm and a solution temperature of 84.4 °C. Due to the corrosion process, a fouling particle by iron oxide was found on the membrane; this fouling layer could promote the “wetting” process in the membrane after a long operating time. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of inserting a new internal tube packing (TP) on the thermal performance of a thermosyphon heat pipe (THP). The THP pipe was made from copper with an inner diameter of 17.4 mm and length of 600 mm. The new internal tube packing (TP) had a central copper disc with two copper tubes soldered onto both sides to transport vapor and condensate. The upper tube or riser had an inner diameter of 8.3 mm and was 300 mm long; it was connected to a hole in the disc from the upper side to transport the steam to the condenser section. The lower tube or downcomer had an inner diameter of 5 mm, was 225 mm long and was connected to the lower side of the disc to collect the condensate and transport it to the evaporator. The TP was inserted inside the THP to complete the design of the improved heat pipe (TPTHP). Experimental results showed that the TPTHP reduces the transit time from 16 to 11 min and the thermal resistance by 17–62% based on the input power and depending on the conditions of the THP. The results also showed that the inclination angle and filling ratio have no effect on the thermal resistance of the TPTHP. [ABSTRACT FROM AUTHOR]

To assess the thermal-hydraulics of a condenser of a typical automotive air conditioning system with maldistribution of intake air, a comprehensive investigation has been taken up. The investigation comprises both experiments and numerical simulations. A special purpose software, CoilDesigner is used to simulate the heat transfer and fluid dynamics of the multiple channel micro-tube air to refrigerant crossflow condenser. While experimentally the overall performance of the condenser is studied by creating blockages of different types and extents in the inlet air path, simulation results provide the spatial variation of pressure, temperature, heat transfer coefficient, and quality on the tube side, in addition to the overall performance for each of the cases. The simulation results clearly bring out the spatial change in the transport parameters due to a typical blockage. One can compare the effective use of the exchanger area of the heat exchanger for an unblocked and a typically blocked case. The simulation also gives a very reliable prediction of the overall performance as recorded by the experiment. [ABSTRACT FROM AUTHOR]

The performance of a novel vapor chamber based on the leaf vein system is tested in this study. In this vapor chamber, the conceptual structure, being composed of leaf-vein-like fractal network and micro fin-pins and used to simulate the transportation principle of plant leaf, is made on the inner surface of the top copper plate to form the wick of the condenser. To the inner surface of the bottom, a copper plate sintered with a layer of porous wick is used as the evaporator. Because the conceptual structure is not restricted by the shape, the vapor chamber is made into circular and rectangular shape respectively. In the circular vapor chamber, the supporting columns sintered with copper powder are used to strength the vapor chamber. However, in the rectangular vapor chamber, the wick of the condenser contacts directly with the wick of the evaporator so as to strength the vapor chamber and shorten the back flow length of the liquid condensed on the groove surface. In the circular vapor chamber, the fractal angle of the leaf-vein-like fractal network is 30–70°, and the vapor chamber is packaged with eight bolts for convenience. In the measurement, the vapor chamber has small thermal resistance when the fractal angle is 40° and 50°, and in the rectangular vapor chamber, the thermal resistance of the vapor chamber is about 0.06 °C/W. [ABSTRACT FROM AUTHOR]

The presence of superheated vapor in condenser heat exchanger is common in many applications, as heat pump or organic Rankine cycle. Rarely taken into consideration in the literature of plate heat exchangers, the present article focuses on the influence of the superheated vapor on the condensation characteristics of an organic fluid (pentane) in a brazed plate heat exchanger (BPHE). A specific experimental approach has been developed for this objective. The tested BPHE prototype consists of 2 channels with chevron angle of 55°, and a hydraulic diameter equal to 4.4 mm. The effect of the pentane mass flux, 9–30 kg m −2 s −1 , and the vapor superheat, 5–25 K, at a mean constant saturation temperature of 36.5 °C (1.029 bars), on the global and local thermo-hydraulic characteristics has been identified. An infrared (IR) metrology is used to distinguish the different fluid state distributions, which are representative of various heat transfers along the BPHE. The IR thermography shows a significant impact of the vapor superheat, on the fluid distribution at the channel inlet depending on the mass flux. Comparing the results with vapor superheat going from 5 to 25 K, we note: 1/an increase of the heat transfer coefficient reaching 70% for the lowest mass flux; 2/an increase of the pressure drop, whose rate (18%) is equivalent to the increase of the heat transfer coefficient for the larger mass fluxes. Superheated vapor is therefore very favorable to heat transfer for condensation in the gravity mode compared to the convective one. Based on experimental measurements and observations, various vapor desuperheating scenarios are tested. The analysis justifies that the suitable desuperheating scenario involves condensation from superheated vapor directly from the channel inlet with liquid vaporization from the condensate film. [ABSTRACT FROM AUTHOR]

The feed water heaters in power plants are actually the condensers using turbine extracting steam to heat feed water. The vertical feed water heater occupies less area than the horizontal one and convenient to lift tube bundles out in maintenance. However, the lower heat transfer coefficient due to thick condensate film limits its application. A novel trisection helical baffled vertical condenser (feed water heater) is proposed with liquid dams and gaps for facilitating condensate drainage. The flow and condensation heat transfer characters of two vertical condensers with variable angled trisection helical baffles of both single-thread and dual-threads and a variable spanned segmental baffled one were numerically studied with Mixture model of Fluent software. The distributions of velocity, pressure, volume fraction of condensate, and local heat transfer coefficient in these heat exchangers were demonstrated. The simulation results show that the inclined baffles with liquid dam and drainage gaps could drain condensate effectively from tube bundle surfaces and prevent liquid film from entraining into vapor, and that the variable angled trisection helical baffled vertical condenser with dual-threads could greatly improve the condensation heat transfer coefficient up to 35.7% higher than that of the variable spanned segmental baffled one. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate thermal–hydraulic characteristics of an air cooled condenser and optimized the design in terms of heat transfer per unit pumping power, area goodness factor, volume goodness factor and material requirement using the 3D numerical simulations. The annular-finned tubes have been considered in this study, which is one of the most common type of fin used for the design of air cooled heat exchangers and known to provide a high heat transfer coefficient per unit pressure drop. The effect of tube shape (elliptical and round), tube diameter [7–24 mm (circular), 30 × 10–30 × 20 mm (elliptical)], fin spacing (2–10 mm), number of rows (2–10), fin height (5–10 mm), air frontal velocity (4.76–6.32 m/s), transverse tube pitch (36.8–44 mm) on the thermal–hydraulic performance has been studied. It is observed that, with an increase in the fin spacing, the heat transfer coefficient increases (by 35–40%) at a constant inlet velocity and the pressure drop decreases (by 60–80%). The frontal area requirement increases by 100–150% with an increase in the fin spacing for the same heat removal capacity. As the row number is increased, the heat transfer coefficient increases initially for N r < 4 by 7–8%, and for N r > 4, the heat transfer coefficient decreases by 23%. An increase in the tube pitch increases the heat transfer coefficient per unit pressure drop by 40%. The fin efficiency is found to decrease with an increase in the Reynolds number, fin spacing and number of tube rows. In the last section optimization of the design has been performed based on Taguchi method and numerical results obtained. It has been observed that the number of tube rows must be kept between 2–4, fin spacing 3–5 mm, tube pitch around 40 mm, and fin height 5 mm for better performance of the condenser. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces for enhanced condensation in air gap membrane distillation (AGMD) may provide significantly improved distillate production rates and increased thermal efficiency. While AGMD is one of the most thermally efficient membrane distillation desalination configurations, large transport resistances in the air gap limit distillate production rates. AGMD experiments were performed with combinations of untreated, hydrophobic, and superhydrophobic condensation surfaces. A nanostructured copper oxide coated condensing surface produced durable 164°±4° contact angles and jumping droplet condensation. Tests were also performed on the air gap spacer, in this case a small diameter support mesh, to judge the effects of superhydrophobic treatment and conductivity on distillate production for AGMD. A novel visualization technique was implemented to see through PVDF membranes and confirm air gap behavior. The experiments were compared with numerical modeling of AGMD film-wise condensation and flooded-gap MD. The results indicate that the introduction of superhydrophobic surfaces can result in improvements in distillate production in excess of 60% over standard AGMD. However, for high distillate production, condensation on the superhydrophobic plate transitions from a partially wetted droplet morphology to Wenzel flooded (wetting) conditions. Mildly hydrophobic condensing surfaces were found to provide moderate improvement in distillate production. Superhydrophobic support meshes made a negligible difference in distillate production, but high conductivity support meshes showed significant increases in flux at the expense of increased conduction losses. The results outline recommended superhydrophobic condensation conditions at varied feed and cold side temperatures for substantial improvement to distillate production rate for AGMD systems in a flat plate configuration. [ABSTRACT FROM AUTHOR]

This paper focuses on the behaviour of a liquid droplet on the surface of a treated solid substrate. We deal with the use of surface tension forces induced by heterogeneous wettability to allow the removal of the droplet. Our main aim is to present a new model able to predict the motion of a droplet of known volume along a wettability gradient taking into account the contact angle hysteresis: a key parameter in the dynamics of the droplet. [ABSTRACT FROM AUTHOR]

In this paper comparative analysis of R152a, R600, R600a, R410a, R290, R1234yf, R404a and R134a as refrigerants in two stage vapour compression refrigeration system has been done on the basis of energetic and exergetic performance. Performance parameters such as entropy generations, COP, exergetic efficiency, sustainability index were investigated at different ambient condition. It was found that both energy and exergy efficiencies of R134a is 8.97% and 5.38% lower than R152a and R600 respectively at -50 °C evaporating and 45 °C condensing temperatures. It was also observed that Irreversibility was minimal at higher evaporating temperatures and condenser was responsible for highest irreversibility or losses in two stage vapour compression refrigeration system. Sustainability index for R152a (1.96) was highest compared to other refrigerants. [ABSTRACT FROM AUTHOR]

Modern-day applications need mm-scale shear-driven flow condensers. Condenser designs need to ensure large heat transfer rates for a variety of flow conditions. For this, good estimates for heat-transfer rate correlations and correlations for the length of the annular regime (beyond which plug-slug flows typically occur) are needed. For confident use of existing correlations (particularly the more recent ones supported by large data sets) for shear-pressure driven internal condensing flows, there is a great need to relate the existing correlation development approaches to direct flow-physics based fundamental results from theory, computations, and experiments. This paper addresses this need for millimeter scale shear driven and annular condensing flows. In doing so, the paper proposes/compares a few new and reliable non-dimensional heat-transfer coefficient correlations as well as a key flow regime transition criteria/correlation. [ABSTRACT FROM AUTHOR]

The internal diameter of a tube in a 'church window' condenser was estimated using an entropy generation minimization approach. The adopted model took into account the entropy generation due to heat transfer and flow resistance from the cooling-water side. Calculations were performed considering two equations for the flow resistance coefficient for four different roughness values of a condenser tube. Following the analysis, the internal diameter of the tube was obtained in the range of 17.5 mm to 20 mm (the current internal diameter of the condenser tube is 22 mm). The calculated diameter depends on and is positively related to the roughness assumed in the model. [ABSTRACT FROM AUTHOR]

The use of flue gas condensers proved to be effective in increasing boiler efficiency and achieving primary energy savings. The transition to the 4th generation district heating will lead to temperature reduction in district heating networks. The aim of this study is to determine the effects of the reduction in the district heating return temperature on flue gas condenser efficiency. Different DH return temperatures and fuel moisture contents were examined, and a calculation model was created. The results show that a reduction in district heating return temperature can lead to an increase in heat recovery through the flue gas condenser. Primary energy savings were estimated based on the amount of heat recovered. [ABSTRACT FROM AUTHOR]

In this study, a reactive distillation column for production of isopropanol was investigated. Firstly, a dynamic model was developed for the process. The model of the process was then programmed, and the process simulated using a base case obtained from the literature. Results showed that distillate contained more than 58 mol% propylene-free isopropanol. In the next step, optimization of some operating variables was performed to maximize concentration of isopropanol in distillate with condenser temperature as constraint, which was considered to be above the freezing point of water. Several simulations were performed by changing operating parameters, and finally optimum isopropanol content in distillate was obtained above 58 mol%. Results of using classic controllers showed that PID controller had the best performance for both condenser temperature set-point tracking and disturbance rejection. [ABSTRACT FROM AUTHOR]