Condenser Performance Research Articles

Comparison of Heat Transfer Performance for Condensation in Corrugated Low Finned Tube and Smooth Tube with Air

The existence of air served as non-condensable gas makes it difficult to design effective titanium condenser in PTA plant. In this paper, the heat transfer characteristic for condensation inside corrugated low finned tube and smooth tube in presence of air was compared. The local heat transfer performance was studied by comparing bulk temperature and local heat transfer rate. The effect of non-condensable gas mass fraction on overall heat transfer performance was also analysed. The results indicated that both the bulk temperature and the local heat transfer rate decreased along the axial direction due to the reduction of steam partial pressure and temperature difference. The average heat transfer coefficient and total heat transfer rate decreased with the increase of inlet non-condensable gas mass fraction. And the corrugated low finned tube could reduce the impact of non-condensable gas by reducing the thickness of gas film and condensate film.

Experimental investigation of a vapor chamber featuring wettability-patterned surfaces

Vapor-chamber heat spreaders are hermetically-sealed systems that rely on metal wicks to circulate a phase-changing liquid and spread heat more efficiently than solid-metal heat sinks. But metal wicks also impose capillary limitations due to their high pressure drop. Surface-wettability patterning does not pose the same limitations and, as shown in this work, could replace metal wicks in vapor chambers to transport the condensate faster and more efficiently. Combining the fast condensate transport characteristic of wettability patterning with the added advantage of domain-regulated dropwise condensation (DWC) and filmwise condensation (FWC) towards enhanced condensation performance, an intriguing hypothesis is explored here by incorporating surface-wettability patterning inside vapor chambers made of copper with and without wicking posts. Wettability patterns with different ratios of superhydrophilic (FWC-promoting) to hydrophobic (DWC-promoting) domains are explored and compared with a control case of unpatterned mirror-finish copper, all located on the condenser side. The heat-spreading capability of the devices from a heated spot of ~0.9 cm2 to an effective vapor chamber area of ~25.8 cm2 is tested at a horizontal orientation where gravity acts perpendicular to the vapor chamber plane and at a vertical orientation. The lowest thermal resistance achieved is 0.24 K/W at 87 W heat load (heat flux of 97 W/cm2) with a horizontally-placed vapor chamber that has a 0.5 mm-thick evaporator wick, a wettability-patterned condenser plate and no wicking posts. The work offers quantitative arguments for incorporating wettability patterning in vapor-chamber technology, and motivates further optimization towards achieving the full potential of this approach.

A useful formulas to describe the performance of a steam condenser in off-design conditions

The article presents relations for determining the performance of a steam condenser in off-design operating conditions. To determine some steam condenser characteristics that are simplified, but useful for analyzing steam cycles of a power unit, a model validated on the basis of factory characteristics and measurement data was used. Formulas presented in the article-for given values of cooling water temperature at the condenser inlet, the cooling water mass flow rate, the inlet steam mass flow rate and reference data-determine the cooling water temperature at the outlet and the pressure in the steam condenser. The model can be used to analyze the operation of cooling systems in off-design conditions and to optimize the way the condenser works with the low-pressure (LP) part of the turbine and all steam cycles. The two proposed relations make it possible to determine the condenser performance easily and with acceptable accuracy. The correctness of the proposed relations was verified on the basis of data obtained from the condenser simulator, measurements obtained from the Distributed Control System (DCS), and data provided in the literature.

Effective reduction of non-condensable gas effects on condensation heat transfer: Surface modification and steam jet injection

Various methods have been proposed to reduce the performance degradation effects of non-condensable gases (NCG) on condensation heat transfer. Among the papers that can reduce the negative effects of NCG, the paper about comparing passive and active methods is insufficient. In this study, to overcome the performance degradation effects of NCG, super-hydrophobic surface modification (passive method) and the steam jet injection method (active method) were applied to horizontal aluminum tubes, which were evaluated experimentally. The test variables were the initial pressure and total pressure for adjusting the NCG mass fraction. The overall and condensation heat transfer coefficients were derived according to the NCG mass faction. In surface modification experiments, super-hydrophobic tubes exhibited better overall heat transfer coefficients up to three times that of filmwise condensation in bare tubes. By reducing the NCG mass fraction from a high level to a low level, the condensation phenomena of the super-hydrophobic tubes transformed in the order of dropwise condensation, flooded condensation, and attached filmwise condensation, resulting in the degradation of heat flux efficiency. In particular, attached filmwise condensation resulted in worse condensation performance than normal filmwise condensation, so no performance improvements can be expected based on surface modification under these circumstances. In contrast, the steam jet injection method provided a noteworthy heat transfer enhancement ratio of 1.18–1.77 times for a broad range of NCG mass fractions.

Application of transport membrane condenser for recovering water in a coal-fired power plant: A pilot study

Transport membrane condenser is considered as promising equipment for recovering water and heat in the thermal power plants. However, most of the studies on transport membrane condenser are either at laboratory scale or theoretical research level. In this study, a pilot scale testing platform is established for investigating the feasibility of transport membrane condenser application in engineering. The importance of this pilot study is to find the fundamental factors affecting the transport membrane condenser and make comprehensive technical and economic analysis of the engineering application. These are the factors which previous laboratory scale did not investigate. Various transport membrane condensers are manufactured for the two-stage experiments in a coal-fired power plant, and some innovative optimization measures are proposed for improving the performance of transport membrane condenser. In this study, the modified transport membrane condenser performs much better than that in other studies. Furthermore, the relationship between recovered water flux, condensation and permeation resistances is analyzed. Condensation resistance is found as the most fundamental factor affecting the recovered water flux. Finally, taking a 330 MW coal-fired unit as an example for technical and economic analysis, transport membrane condenser exhibits a good economic application prospect in engineering.

Water Condensation and Droplet Shedding Behavior on Silica-Nanospring-Coated Tubes

In this work, the water condensation performance of methylated silica-nanospring (SN)-coated horizontal aluminum tubes is assessed. Coated samples with varying nanospring mat thicknesses, from 784 to 2902 nm, were studied, which exhibited static contact angles and CA hysteresis values of 155° and 16°, respectively. Dropwise condensation and increased droplet shedding were observed on these coated tubes. Video analysis determined that tubes with 15 and 20 min SN growth times experienced an 84% increase in the condensate removal rate over the baseline. Moreover, with a hybrid wettability consisting of alternating regions of SN and bare aluminum, a 96% increase in condensate removal was experienced. Additionally, the average droplet departure size was reduced on these SN-coated tubes. SEM imaging and XEDS analysis were also performed on the tubes and revealed that the coating was reasonably durable having withstood the condensation environment. Moreover, the coated tubes were shown to exhibit the same XEDS spectra both before and after testing.

Evaluation of Zn- and Fe- rich organic coatings for corrosion protection and condensation performance on waste heat recovery surfaces

Abstract The corrosion protection performance of commercial organic coatings over Stainless Steel (304 L) was investigated in highly acidic media. Three coatings were applied by air spraying and subsequently evaluated for their performance against chemical corrosion by concentrated H2SO4, HNO3, and HCl in terms of % mass loss. Open current potential (OCP) and potentiodynamic polarization (PD) measurements were performed. The water condensation properties of the coatings were monitored for their evaluation as potential protective coatings in condensing economizer applications. ZN691 coating exhibited better protection than ANORZINC and TROPIS versus time in contact with 40% of H2SO4, HNO3 and 37% HCl. Electrochemical results confirmed the superior performance of ZN691 over ANORZINC and TROPIS with corrosion rates at 0.017, 0.098 and 0.097 mpy respectively. Condensation experiments for ZN691 showed a water collection rate of 1.487 ml m−2 h−1 at 40 °C and 100% RH. According to the results, the Zn rich epoxy-based coatings are promising for corrosion protection of condensing economizer elements.

P-wave holographic superconductors with massive vector condensate in Born\u2013Infeld electrodynamics

In this paper, we have studied the effect of Born–Infeld electrodynamics in holographic p-wave superconductors with massive vector condensation. We have analysed this model in the probe limit using a variational method known as the Stürm–Liouville eigenvalue approach. For this p-wave holographic superconductor model, we have calculated the critical temperature T_{c} as well as the value of the condensation operator for two different choices of m^{2}. We have also pointed out the similarities and dissimilarities between this model for m^{2} = 0 and p-wave holographic superconductor model constructed out of Einstein–Yang–Mills theory. We have then computed the conductivity of these holographic superconductor models using a self-consistent approach and have shown that the DC conductivity diverges.

Condensation and Wetting Behavior on Hybrid Superhydrophobic and Superhydrophilic Copper Surfaces

Abstract A novel hybrid superhydrophobic and superhydrophilic copper surface was fabricated using a lift-off process to integrate the benefits of dropwise and filmwise condensation together. The superhydrophilic surface was comprised of microflower like CuO and nanorod Cu(OH)2 with a diameter in the range of 200–600 nm and the superhydrophobic surface was fabricated by chemical modification with Cytop on the hierarchically structured surface of CuO/Cu(OH)2. Wetting condition effect on the hybrid surface was investigated experimentally with a high-speed camera attached to a microscope and an environmental scanning electrical microscope (ESEM). Out-of-plane droplet jumping motion on superhydrophilic region and gravity effect on the droplet motion were examined. Experiment results showed that effective heat transfer coefficients of hybrid superhydrophobic and superhydrophilic surfaces were improved as compared with those of pure superhydrophobic surface. Comparison results between two hybrid surfaces with 2 and 4 mm pattern pitches indicated that the distance reduction between two neighboring superhydrophilic areas can enhance the condensation performance because short distance can promote the microcondensate coalescence and droplets removal.

Data driven assessment of a small scale evaporative condenser based on a combined artificial neural network with design of experiment approach

Abstract The performance of evaporative condensers depends on operating parameters such as the state of ambient air and circulating water (environmental) and the condition of the refrigerant fluid (operational). The equipment behavior can be analyzed in a laboratory environment with the aid of Design of Experiment DoE tools, which effectively assists in the identification of trends and couplings, but the procedure depends on data collected in a controlled manner. The aim of this paper is to analyze the behavior of a small-scale evaporative condenser tested in the laboratory environment with the aid of DoE, based on an uncontrolled experimental dataset. A data driven approach is applied to the problem by creating an neural network algorithm capable of reproducing the equipment behavior as if it were obtained from controlled factors, with coefficients of determination of 0.973 and 0.988 for the heat reject q ˙ c o n d and the overall heat transfer coefficient Ucond. General functions for these outputs are obtained out from a factorial 2k DoE approach, allowing to identify the environmental air wet bulb temperature Twb, in as the most relevant parameter for the q ¯ c o n d prediction and m ˙ s w and (Twb, in, m ˙ a i r ) as the most relevant ones concerning Ucond prediction. The errors from these prediction functions are calculated to be 3.48% and 3.69% respectively, with coefficient of determination of 0.793 and 0.752. The proposed data driven metamodels showed to be useful tools to represent and simulate complex systems in a much easier way, concerning both their mathematical implementation and computational running time.

Stable dropwise condensation observed on a hierarchically structured superhydrophobic surface incorporating micro-domes

With global temperatures increasing and air conditioning becoming more prevalent, the need to limit its electricity consumption and improve its efficiency is greatly increased. However, air conditioning heat transfer is often impeded by condensed atmospheric water accumulating on cooling coils, potentially leading to degraded cooling performance and the growth of pathogens that may endanger human health. In order to improve air conditioning heat transfer performance, surfaces with superior dropwise condensation and more rapid condensate-shedding capability are desirable. Inspired by the exceptional droplet shedding performance of natural plant leaf surfaces, we have developed a fabrication process to create hierarchical surfaces composed of arrays of micro-domes or -pillars that are then coated with a nanoporous, fluorosilanized zinc oxide film. In this paper, we characterize the performance of these surfaces when exposed to supersaturated moist air. We found that the most desirable condensation performance was provided by one specific surface, which featured a micro-dome array with diameters and spacings of 30 μm. This surface repeatably offered stable dropwise condensation over 30-min experimental durations. Surfaces with other dome separations, surfaces with square-tipped micropillars, and flat surfaces with only the nanoporous coating all showed less stable dropwise condensation and tended to become flooded with condensate as time progressed. The fabrication, testing and image analysis techniques described here could help in the development of optimized surfaces for heat exchangers operating in moist air.

Research on Variable Operating Characteristics of Condenser Considering Vacuum Tightness

Considering the effect of vacuum tightness on the performance of condensers, the influence of various operating parameters on condenser pressure and terminal difference was studied by establishing a calculation model of variable operating conditions of condensers. The results show that the change of heat load has a greater impact on the vacuum, and the effect is more pronounced when the initial temperature of the cooling water is higher. Therefore, it is necessary to strictly control the internal leakage of the valve, reasonably adjust the steam parameters of the shaft seal, and minimize the additional heat load on the condenser. The cooling water flow and initial temperature directly affect the condenser vacuum and have a greater impact. The initial temperature of the cooling water is not easy to control. When the initial temperature is high, most power plants use a method of increasing the flow to increase the condenser vacuum. The cleaning coefficient and air leakage have a great impact on the quality of the vacuum. Therefore, regular operation of the rubber ball cleaning system and timely vacuum leak detection are necessary measures to ensure the vacuum of the unit, which can effectively improve the economic efficiency of the unit.

Improving air-side heat transfer performance in air-cooled power plant condensers

One method to reduce water consumption in cooling towers for steam condensation is to use dry-cooled technologies with air as the heat rejection medium. These air-cooled systems are beneficial where water is unavailable or uneconomical, but typically result in lower power plant efficiencies. The present study investigates the application of an A-frame air-cooled condenser (ACC) with various air-side enhancements to increase dry-cooled plant performance to levels approaching wet-cooled plants. A computational model was developed to predict the air-cooled condenser performance during the summer (inlet air at 30 °C and 25% relative humidity), when air-cooled systems typically perform the worst. Parametric studies were conducted to identify optimal condenser geometries with smooth, wavy, and louvered fins. The segmented condenser model was integrated into Rankine cycle and combined cycle power plant models to determine the impact of various condenser fin geometries on overall cycle performance. While ACC designs with wavy or louvered fins improved the overall cycle efficiencies over the baseline case, it was found that a reduction in fin spacing of the conventional, smooth fins resulted in the largest improvement in cycle efficiency (1.14% increase for the Rankine cycle, and a 0.84% increase for the Combined cycle).

Optimization Study of New Type High-Capacity Synchronous Condenser based on Coupling of Electromagnetic and Temperature Field

In order to optimize electromagnetic structure of new type high-capacity synchronous condenser, increase reactive capacity, and improve the speed of dynamic response, the theoretical derivation of the effects on the main performance parameters of the synchronous condenser is carried out, also the influence of the structure size of the synchronous condenser on the transient characteristics is clarified. Changing the air gap length and improving the size of stator structure are proposed to optimize the performance of synchronous condenser. The electromagnetic calculation of the optimized synchronous condenser is carried out by using finite element analysis method, the mathematical relationship between length of air gap and reactive capacity is clarified and the relationship between size of stator slot and fast response characteristics is explicited too. The temperature field of the synchronous condenser under multiple working conditions is simulated. The simulation results show that the temperature distribution of the optimized synchronous condenser is reasonable, and it possess good effect of cooling. Also the overload capacity of the synchronous condenser is verified with the temperature field.

Data-Driven Air-Cooled Condenser Performance Assessment: Model and Input Variable Selection Comparison

This paper presents a data–driven model for the estimation of the performance of an aircooled steam condenser (ACC) with the aim to develop an efficient online monitoring, summarized by the condenser pressure (or vacuum) as Key Performance Indicator. The estimation of the ACC performance model was based on different dataset from three different combined cycle power plants with a gross power of above 380 MWe each, focusing on stationary condition of the steam turbine. The datasets include both boundary (e.g. Ambient Temperature, Wind Speed) and operative parameters (e.g. steam mass flow rate, Steam turbine power, electrical load of the ACC fans) acquired from the power plants and some derived variable as the incondensable fraction, which calculation is here proposed as additional parameter. After a preliminary sensitivity analysis on data correlation, the paper focuses on the evaluation of different ACC Condenser models: Semi-Empirical model is described trough curves typically based on steam mass flow rate (or condenser load) and the ambient temperature as main parameters. Since monitoring based on ACC design curves Semi-Empirical models, provides biased poor results, with an error of about 15%, the curves parameters were estimated basing on training data set. Other two data driven models were presented, basing on a neural network modelling and multi linear regression technique and compared on the base of the reduced number of input at first and then including aldo the other process variables in the prediction of the condenser back pressure. Estimate the parameters of the Semi-Empirical model, results in a better prediction if just steam mass flow rate and ambient temperature are available, with an error of the 7%, thanks to the knowledge contained within the “curves shapes”, with respect to linear regression (8.3%) and Neural Network models (7.6%). Higher accuracy can be then obtained by considering a larger number of operative parameters and exploiting more complex data-driven model. With a higher number of features, the neural network model has proved a higher accuracy than the linear regression model. In fact, the mean percentage error of the NN model (2.6%), in all plant operating conditions, is slightly lower than the error of the linear regression model, but presents and much lower than the mean error of the Semi-Empirical model thanks to the additional data-based knowledge.

Membrane Condenser for Particulate Abatement from Waste-Gaseous Streams

Membrane Condenser (MC) is a novel membrane contactor operation recently investigated for the valorization of industrial waste gaseous streams. In particular, until now, it was applied for water recovery from flue gas, cooling tower plumes, etc. More recently, its effectiveness and flexibility in contaminants (such as, NH3 , HF, SO2 ) removal and control from waste gaseous streams was also proved. In the present work, the application of membrane condenser for water recovery as well as microparticles removal from gaseous streams are presented. Experimental tests showed that microparticles did not affect membrane condenser performance, neither in terms of water recovery nor in term of fouling. Moreover, the carried-out tests revealed also that the complete retention of particles can be achieved only through the proper choice of the membrane, with pore size lower than particles diameter.

Experimental study on the heat and mass transfer characteristics of air-water two-phase flow in an evaporative condenser with a horizontal elliptical tube bundle

In this paper, the heat and mass transfer performance of an evaporative condenser with a horizontal elliptical tube bundlewasexperimentally studied. The effects of important parameters, such as the spray density, frontal air velocity, ambient temperature and humidity, on the heat and mass transfer performance were discussed in detail. Among all parameters studied, it was found that the wet bulb temperature has greater effects on the heat transfer performance than the relative humidity. Thedifference between the steamtemperature and tube wall temperature, the inlet steam flow rate and the steam saturation temperature all affect the mean within-tube condensation heat transfer coefficient. Themeanwithin-tube condensation heat transfer coefficientincreases greatly when the latter two increase, while the increase in the difference between steam and tube wall temperature hinders the mean within-tube condensation heat transfer coefficient. The empirical correlations of the mean within-tube condensation heat transfer coefficient, wall-film convective heat transfer coefficient and the film-air convective mass transfer coefficient were finally obtained by regression fitting the experimental data using the least square method and all empirical correlations have enough precision in engineering calculation.

Thermal hydraulic characteristics of two-phase natural circulation for secondary side passive residual heat removal system

Abstract The Secondary Circuit Passive Residual Heat Removal System (PRHRS) is designed for advanced nuclear power system. A research on thermal hydraulic characteristics of two-phase natural circulation process for secondary circuit PRHRS has been carried out using the RELAP5 code. For this, the natural circulation steam generator (SG) and the PRHRS are modeled. Five thermal boundary conditions are set to verify the function of PRHRS. The phenomenon of flow instability in the two-phase natural circulation process is of great significance for system operation, as well as the performance of SG and condenser. Therefore, the focus is on the natural circulation flowrate oscillation of steam and condensed water. The mixed water level difference between descending pipe of PRHRS and secondary side of natural circulation SG is found to be the meaningful parameter to characterize the flow instability of natural circulation. The comparative analysis is also performed by considering the effects of height between the SG and condenser, as well as system resistance, which can provide support for PRHRS design and optimization.

The ambient wind impact on eddy current distribution in air cooling island

With increasing ambient wind speed, eddy currents appear near condenser cells, affecting the thermal-flow performance of a direct air-cooled condenser. To examine the impact of ambient wind on the eddy-current distribution of an air-cooling island, a 2 × 600 MW direct air-cooling unit in North China was studied. To compare a series of different inlet wind speeds, the temperature and pressure distribution and the mechanism of and variation in eddy currents were studied. Moreover, the effects of ambient wind speed on the inlet flow rate of an axial-flow fan cluster were examined. Numerical results show that with increasing ambient speed, the chance of hot-air plume generation increases, resulting in a reduction in heat-transfer volume and efficiency. Additionally, more negative-pressure areas are created near the condenser cells. Vortices appear in the condenser-cell flow field, gradually becoming larger. The mass-flow rate of the axial flow fan cluster exhibits a downward trend with increasing ambient speed.

Numerical Investigation on the Influence of Mechanical Draft Wet-Cooling Towers on the Cooling Performance of Air-Cooled Condenser with Complex Building Environment

In air-cooled power units, an air-cooled condenser (ACC) is usually accompanied by mechanical draft wet-cooling towers (MCTs) so as to meet the severe cooling requirements of air-cooling auxiliary apparatuses, such as water ring vacuum pumps. When running, both the ACC and MCTs affected each other through their aerodynamic fields. To make the effect of MCTs on the cooling performance of the ACC more prominent, a three-dimensional (3D) numerical model was established for one 2 × 660 MW air-cooling power plant, with full consideration the ACC, MCTs and adjacent main workshops, which was validated by design data and published test results. By numerical simulation, we obtained the effect of hot air recirculation (HAR) on the cooling performance of the ACC under different working conditions and the effect of MCTs on the cooling performance of the ACC. The results showed that as the ambient wind speed increases, the hot recirculation rate (HRR) of the ACC increased and changed significantly with the change of wind directions. An increase in ambient temperature can cause a significant rise in back pressure of the ACC. The exhaust of the MCTs partially entered the ACC under the influence of ambient wind, and the HRR in the affected cooling units was higher than that of the nearby unaffected cooling units. When the MCTs were turned off, the overall HRR of the ACC decreased. The presence of MCTs had a local influence on the cooling performance of only two cooling units, and then slightly impacted the overall cooling performance of the ACC, which provides a good insight into the arrangement optimization of the ACC and the MCTs.