Water Condensation Rate Research Articles

Experimental investigations on water condensation in the nanopores of shales

ABSTRACT Condensation is an important mechanism influencing the flow and accumulation of water in shales, which is important in many resource and environmental issues. This study presents a laboratory study on the capillary condensation process of water in the nanoscale pores of shales. Four borehole core samples of shale obtained from the Qaidam Basin, China, were used to perform the experiments. The water condensation experiments were performed at various degrees of relative humidity ranging from 65 to 95%. The condensation experiments indicated that relative humidity and pore diameter of shale are the two most important factors to control the water condensation. When the RH is 65%, the equilibrium water condensation amount of the four samples (S36, S49, S52, S65) is 0.001245 g/g, 0.000753 g/g, 0.007339 g/g, and 0.006993 g/g, respectively. When the RH is increased to 95%, the equilibrium water condensation amount of the four samples is 2.08, 2.70, 1.30, and 1.26 times of that of 65% relative humidity. In the beginning, the water condensation rate increased with the relative humidity and decreased gradually when the RH became higher than a critical relative humidity value, which had not been accurately determined but within the range of 90–100%. RH and pore diameter are the two most important factors to control the water condensation amount. The water condensation amount exhibited a correlation with the Kelvin Condensation Amount, which is defined as the calculated water condensation amount based on Kelvin equation and pore size distribution. According to the experimental data, we developed a mathematical model that described the exponential relationship between the Kelvin condensation amount and the water condensation amount. The total organic carbon content, clay content, and pore size were the dominant factors in the process of water condensation, while the quartz had little effect on the process.

Experimental investigation on the performance parameters of a helical coil dehumidifier test rig

ABSTRACT Water scarcity is a major problem faced in different parts of the world due to various reasons. Highly humid places closer to sea offers discomfort to the people and the moisture transport inside the building causes hazards to the interior and exterior over a period of time. However, both the water scarcity and high humidity problem can be addressed with the development of a novel system. Present work focuses on the dehumidification process where highly humid air moves over the copper coils wound helically, with cold water running through it. Vapor compression refrigeration cycle maintains the temperature of the cold water. The dehumidification is enhanced with the condensation of moisture and then dehumidified air enters the room. The fresh water collected is used as drinking water. Thermal parameters like temperature and humidity are measured and the overall dehumidification efficiency is assessed. Water condensation rate is found to be optimum for the air velocity 2 m/s with a dehumidification coil temperature of 2°C. These values are 22% and 31% higher than the water temperatures of 5°C and 10°C. The average water harvesting from the current system is 1.90 kg/hr. or 2.57 liters per hour (l/hr.).

Self Assembly of Super-hydrophobic Nanotextured Methyl Functionalized Silica on Copper and Aluminium Surfaces for Moist Air Condensation

The super-hydrophobic surfaces enhance the transport coefficients of the condensation process and therefore it is very useful in water harvesting devices. In the present study, super-hydrophobic substrates are fabricated by growing self-assembled silica nanostructures on copper (Cu) and aluminum (Al) surfaces by a sol-gel based solution immersion method at room temperature. The contact angles measured were 155 ± 2° and 156 ± 2° on coated Cu and Al surfaces respectively. The water condensation rate on the coated Cu surface significantly increased from 188 ml/m2-hr to 630 ml/m2-hr, while that of the coated Al surface increased from 190 ml/m2-hr to 650 ml/m2-hr. The present work shows that the metallic substrates with super-hydrophobic coatings have excellent potential for water harvesting from moist air, and they were effectively used for more than 120 days.

Molecular Dynamics Simulations of Water Condensation on Surfaces with Tunable Wettability.

Water condensation plays a major role in a wide range of industrial applications. Over the past few years, many studies have shown interest in designing surfaces with enhanced water condensation and removal properties. It is well known that heterogeneous nucleation outperforms homogeneous nucleation in the condensation process. Because heterogeneous nucleation initiates on a surface at a small scale, it is highly desirable to characterize water-surface interactions at the molecular level. Molecular dynamics (MD) simulations can provide direct insight into heterogeneous nucleation and advance surface designs. Existing MD simulations of water condensation on surfaces were conducted by tuning the solid-water van der Waals interaction energy as a substitute for modeling surfaces with different wettabilities. However, this approach cannot reflect the real intermolecular interactions between the surface and water molecules. Here, we report MD simulations of water condensation on realistic surfaces of alkanethiol self-assembled monolayers with different head group chemistries. We show that decreasing surface hydrophobicity significantly increases the electrostatic forces between water molecules and the surface, thus increasing the water condensation rate. We observe a strong correlation between our rate of condensation results and the results from other surface characterization metrics, such as the interfacial thermal conductance, contact angle, and the molecular-scale wettability metric of Garde and co-workers. This work provides insight into the water condensation process at the molecular scale on surfaces with tunable wettability.

Impact of poleward heat and moisture transports on Arctic clouds and climate simulation

Abstract. Many general circulation models (GCMs) have difficulty simulating Arctic clouds and climate, causing substantial inter-model spread. To address this issue, two Atmospheric Model Intercomparison Project (AMIP) simulations from the Community Atmosphere Model version 5 (CAM5) and Seoul National University (SNU) Atmosphere Model version 0 (SAM0) with a unified convection scheme (UNICON) are employed to identify an effective mechanism for improving Arctic cloud and climate simulations. Over the Arctic, SAM0 produced a larger cloud fraction and cloud liquid mass than CAM5, reducing the negative Arctic cloud biases in CAM5. The analysis of cloud water condensation rates indicates that this improvement is associated with an enhanced net condensation rate of water vapor into the liquid condensate of Arctic low-level clouds, which in turn is driven by enhanced poleward transports of heat and moisture by the mean meridional circulation and transient eddies. The reduced Arctic cloud biases lead to improved simulations of surface radiation fluxes and near-surface air temperature over the Arctic throughout the year. The association between the enhanced poleward transports of heat and moisture and increase in liquid clouds over the Arctic is also evident not only in both models, but also in the multi-model analysis. Our study demonstrates that enhanced poleward heat and moisture transport in a model can improve simulations of Arctic clouds and climate.

Impacts of Humidity Adjustment Through Radar Data Assimilation Using Cloud Analysis on the Analysis and Prediction of a Squall Line in Southern China

AbstractThis study examines the impacts of humidity adjustment in a cloud analysis system on the analysis and forecast of a squall line that occurred in southeast China on 23–24 April 2007. Radial velocity data are assimilated using the ARPS three‐dimensional variational system while reflectivity data are assimilated by a cloud analysis system. Experiments with two different humidity adjustment schemes are performed, with the original and enhanced versions. Another experiment does not adjust moisture. Both schemes generally decrease the humidity in front of the convective line and increase the humidity within the convective and stratiform regions of squall line compared to no humidity adjustment, and the original scheme produces the higher humidity within precipitation regions, especially the stratiform region. Both schemes improve the forecast of squall line structure, including the leading convective line, a transition zone, and a trailing stratiform region. Among the three experiments, the enhanced scheme produces the highest precipitation forecast skill. The latent heating rates are also diagnosed to investigate the microphysical responses to the humidity adjustment. The cooling outside of the observed precipitation regions corresponding to the humidity reduction also acts to suppress spurious precipitation. Water vapor condensation into cloud water and cloud water evaporation generally dominate the latent heating/cooling below the freezing level. Compared to the enhanced scheme, the original scheme releases much more latent heat in the middle troposphere, causing more warming. This is linked to the higher cloud water condensation rate, due to the higher amount of moisture addition/adjustment by the original scheme.

Visualized experimental investigation on cross-flow indirect evaporative cooler with condensation

In hot and humid regions, condensation will easily occur in the dry channels of indirect evaporative cooler (IEC) due to high dew point temperature of primary air. However, the visualized investigation on cross-flow IEC with condensation has seldom been reported by previous studies. Therefore, a visualized cross-flow IEC was constructed with a transparent cover plate for observing the condensation in a primary air channels. A series of experiment had been carried out to investigate the comprehensive performance of IEC under different inlet primary air temperature and humidity. The outlet primary air temperature, wb-effectiveness, water consumption rate, heat transfer rate and condensation rate were analysed in detail under non-condensation, partial condensation and total condensation cases. The experimental results showed that the turning point from non-condensation to partial condensation was 33.0 °C under relative humidity of 50%, 29.0 °C under relative humidity of 60% and partial condensation to total condensation was 35.0 °C under relative humidity of 70%, 30.0 °C under relative humidity of 80%, respectively. Condensation improved the outlet primary air temperature, total heat transfer, water consumption rate and condensation rate but lowered the wb-effectiveness. Furthermore, the thermal resistance of condensate film was non-ignorable because of thick water film.

Black powder formation by dewing and hygroscopic corrosion processes

The presence of black powder in natural gas pipelines can lead to equipment erosion, valve failure, instrumentation malfunction, and increased pressure drop. However, despite its impact on downstream and midstream operations, black powder production is poorly understood. In the present work, black powder formation as a result of corrosion was investigated by simulating sales gas conditions in a glass cell. Steel specimens were systematically exposed to a range of CO2, H2S, and O2 partial pressures at differing water condensation rates. The potential for hygroscopic material assisting black powder formation was also investigated. Friable corrosion products found in dewing conditions consisted of siderite (FeCO3), mackinawite (FeS), and hematite (Fe2O3). The expected mass of corrosion products, as determined from experimental corrosion rates, are in line with the high levels of black powder that can be experienced. The presence of hygroscopic NaCl crystals facilitated corrosion at relative humidities as low as 33%.

Design and Simulation of Condensing Heat Exchanger

The conventional heat recovery techniques recover only sensible component of the flue gas heat and a significant portion of the flue gas heat is lost to the atmosphere. Condensing heat exchangers are designed to retrieve both sensible and latent heat components of the heat present in flue gas by promoting condensation of water vapour present in the flue gas. It has several challenges due to non-availability of the low-temperature heat sink. The paper explains numerical simulations based on analytical modeling of the heat and mass transfer processes involved in condensation of moisture in the flue gas in a cross-counter flow tubular heat exchanger- of size 1.752 m × 1.274 m × 2.230 m which comprises of 78 tube passes and 6 tubes with cooling water flowing inside and flue gas over the tubes. The performance of the system is exhibited as a function of different parameters. A mathematical model using MS-Excel and VB Macros as a tool is developed to study the effect of operating parameters on the performance. The governing equations and correlations based on mass and energy balances for the system are used to compute variables such as flue gas exit temperature, cooling water outlet temperature, mole fraction and condensation rates of moisture. The equations are solved using an iterative solution technique with calculations of heat and mass transfer coefficients and physical properties. The paper focuses on the maximization of heat recovery and the various parameters affecting the heat and moisture recovery and condensation. The effect of operating parameters like inlet temperatures of both the fluid streams and flow ratio is studied in order to achieve the maximum heat and moisture recovery. The condensation and heat transfer rates increase significantly by increasing the flow ratio and decreasing the inlet cooling water temperature.

Patterned Polymer Coatings Increase the Efficiency of Dew Harvesting.

Micropatterned polymer surfaces, possessing both topographical and chemical characteristics, were prepared on three-dimensional copper tubes and used to capture atmospheric water. The micropatterns mimic the structure on the back of a desert beetle that condenses water from the air in a very dry environment. The patterned coatings were prepared by the dewetting of thin films of poly-4-vinylpyridine (P4VP) on top of polystyrene films (PS) films, upon solvent annealing, and consist of raised hydrophilic bumps on a hydrophobic background. The size and density distribution of the hydrophilic bumps could be tuned widely by adjusting the initial thickness of the P4VP films: the diameter of the produced bumps and their height could be varied by almost 2 orders of magnitude (1-80 μm and 40-9000 nm, respectively), and their distribution density could be varied by 5 orders of magnitude. Under low subcooling conditions (3 °C), the highest rate of water condensation was measured on the largest (80 μm diameter) hydrophilic bumps and was found to be 57% higher than that on flat hydrophobic films. These subcooling conditions are achieved spontaneously in dew formation, by passive radiative cooling of a surface exposed to the night sky. In effect, the pattern would result in a larger number of dewy nights than a flat hydrophobic surface and therefore increases water capture efficiency. Our approach is suited to fabrication on a large scale, to enable the use of the patterned coatings for water collection with no external input of energy.

Combined Thermoelectric Power Generation and Passive Vacuum Desalination

Abstract This paper proposes a passive water desalination system combined with thermoelectric power generation. Desalination is achieved by reducing the saturation temperature of saline water through vacuum. The vacuum is generated using 5m of negative head (drop), which significantly reduces the boiling temperature of water. The thermoelectric generator unit (TEGU) uses four thermoelectric cells to generate electricity using Seebeck effect. The cold side temperature of TEGU is maintained by the reduced saturation temperature of saline water, and temperature for hot side can be provided by low grade heat source, e.g. solar, waste heat. The heat transfer through the system is a transient to steady state conduction, and theoretical calculations show that an absolute pressure of 50 kPa can be achieved in the system which reduces the saturation temperature to around 80 ° C. Thermal resistance and heat flow networks are used to validate fresh water output, evaporation, and condensation rates based on input heat. The objective is to achieve proof of concept through experimental model, and thermal analysis. Further research is directed into elimination of non-condensable gases in the system and use of passive condensation techniques to reduce energy input.

Modeling humid air condensation in waste natural gas-powered atmospheric water harvesting systems

4% of the natural gas produced globally is flared at oilfields due to the absence of gas handling infrastructure and unfavorable economics. Recent work has proposed the utilization of this excess gas for atmospheric water harvesting (AWH) for oilfield operations, wherein gas-powered refrigeration cycles generate the cooling capacity for large scale dehumidification, via condensation. This work develops an indepth, comprehensive, analytical modeling framework to predict the water condensation in waste gas-powered AWH systems. Firstly, gas powered refrigeration systems are analyzed to identify key system parameters and considerations. Secondly, an analytical model is developed to capture the complex heat and mass transfer phenomena associated with condensation of humid air in a fin and tube heat exchanger. This involves using heat and mass transfer relations to estimate the dehumidification process line. The model can predict the water condensation rate as a function of the gas flow rate, ambient weather and the refrigeration system utilized. The model is used to predict flared gas-based water harvests in the Eagle Ford (Texas) and Bakken (North Dakota) Shale oilfields, which account for the majority of US flaring. Results indicate that 1 cubic meter of natural gas can condense 2.3 and 0.65gallons water (on an annual average basis) in Texas and North Dakota, respectively. The weather-dependent condensation rates range from 3 to 10 (Texas) and 0 to 0.8 (North Dakota) gallons/day/square meter of condenser area. Overall, flared gas-based AWH can utilize 77% and 40% of the excess gas in Texas and North Dakota, respectively. This work analyzes various aspects of humid air condensation and evaluates the sensitivity of the condensation rate to key engineering parameters. Overall, this work develops the foundational modeling tool to predict the performance of all types of humid air condensation systems.

Performance analysis of a liquid desiccant system with an adjustable reflux ratio of regeneration solution

In the liquid desiccant system, the amount of the diluted solution sent to the regenerator has a great influence on the system performance. The liquid desiccant system with an adjustable reflux ratio of regeneration solution was proposed in the paper, and the effect of the solution regeneration reflux ratio on the system performance was analysed by simulation. The energy consumption, the electric coefficient of performance and the thermal coefficient of performance under different water condensation rates and varied solution regeneration reflux ratio were obtained. The results show that, the overall performance of the liquid desiccant system can be improved by reducing the solution regeneration reflux ratio; a 1% decrease in the reflux ratio leads to a 0.56–1.02% average growth rate of electric coefficient of performance and a 0.51–0.95% average growth rate of thermal coefficient of performance. Moreover, when the regeneration temperature is high and the water condensation rate of the process air is low, the improvement from decreasing the solution regeneration reflux ratio is more significant. However, the reflux ratio cannot be reduced to an unlimited extent. There is a rational optimum range of the reflux ratio to achieve high thermal coefficient of performance, the optimum range under low dehumidifying load is different from that under high load. Practical application: The performance of a liquid desiccant system can be improved by the proposed system configuration with an adjustable reflux ratio of regeneration solution, such novel system configuration could be applied for the design of air conditioning system, which is beneficial for the energy saving in building. Moreover, the rational optimum ranges of the reflux ratio to achieve high coefficient of performance under different dehumidifying loads are obtained, which could provide guidelines for the design and operation management of the liquid desiccant based building air conditioning system.

Condensation corrosion of carbon steel at low to moderate surface temperature and iron carbonate precipitation kinetics

This study investigates the influence of surface temperature and droplet retention time (DRT) on the corrosion rate, FeCO3 supersaturation, and scaling tendency of carbon steel exposed to water condensation. This corrosion phenomenon is also known as top of the line corrosion (TLC). TLC is found to be governed by surface temperature irrespective of water condensation rates (WCR) at low surface temperature (15°C). The results also demonstrate that the DRT directly influences FeCO3 supersaturation and scale formation. A new kinetic constant for the calculation of FeCO3 precipitation rate under condensing condition at the top of the line is proposed.

Polymer heat exchanger design for condensing boiler applications

Condensing boilers achieve very high efficiency levels by recovering both sensible heat and water vapor latent heat from the flue gas. Research since the 1980's has focused on corrosion in such condensing heat exchangers related to the acidic condensate and material selection. Polymers in condensing heat exchangers have been considered to avoid the cost and corrosion concerns of metallic designs. Past efforts have shown that polymers offer the advantage of corrosion resistance and cost, however, lower thermal conductivity limited their application. More recent developments have introduced thermally conductive polymers which now offer promising conductivity values. This project focused on the evaluation of a thermally conductive polymer heat exchanger for this application.Computational fluid dynamic results indicated thermal conductivity values of stainless steel, a typical heat exchanger material, do not need to be achieved for similar heat transfer performance. An increase in thermal conductivity from about 10 times that of the base polymer can achieve an overall heat exchanger effectiveness similar to that achieved with stainless steel. A polymer composite thermal conductivity of approximately 2.5 W/m⋅K would be adequate. Thermally conductive polymer materials are now commercially available which offer values up to 20 W/m⋅K. In this work, one Nylon-12 and one thermally conductive polymer composite heat exchanger prototypes were constructed for a condensing boiler application. Tests demonstrated that good overall heat transfer performance was achieved. The lower thermal conductivity of the polymer heat exchanger will lead to higher surface temperatures and lower water condensation rates.

Numerical study of a water distillation system using solar energy

This paper tackles an optimization approach in order to boost the fresh water production of a new design of a solar still which is located at Sfax engineering national school in Tunisia. This optimization approach is based upon the above mentioned design’s improvement by coupling the conventional solar still into at a condenser, solar air and water collector and humidifier. This new concept of a distiller solar still using humidification- dehumidification processes (HD) is exploited for the desalination purpose. As a result of this work, the humidification- dehumidification processes have an essential effect in improving the solar still performance. Performance has been predicted theoretically in terms of water and inner glass cover temperatures, the inlet temperature of air and water of the new concept of distiller on water condensation rate and fresh water production. A general model based on heat and mass transfers in each component of the unit has been developed in steady dynamic regime. The developed model is used, simulating the HD system, to investigate the influence of the meteorological and operating parameters on the system productivity. The obtained set of ordinary differential equations has been converted to a set of algebraic system of equations by the functional approximation method of orthogonal collocation. The developed model is used to simulate the HD system in order to investigate the steady state behavior of each component of the unit and the entire system exposed to a variation of the entrance parameters and meteorological conditions. The obtained results were compared with those of other studies and the comparison gives a good validity of the present results.

Impact of Microstructure of Cathode MPL on Interface Water Transport and Power Generation Characteristics of PEFC

It is well known that water flooding in porous electrode of polymer electrolyte fuel cells (PEFCs) leads to severe performance degradation. Microporous layer (MPL) employed between cathode catalyst layer (CL) and gas diffusion layer (GDL) helps to alleviate water accumulation at CL/GDL interface. The aim of this study was to investigate the effect of carbon black (CB) loading of MPL on its microstructure, the interfacial water transport and the power generation characteristics of a PEFC. The pore structure of MPL was analyzed by SEM/EDX and mercury intrusion porosimetry. Furthermore, the water droplet behavior in the cathode electrode was optically visualized using a transparent cell. It was found that MPL addition accelerates water discharge through electrode and improves cell performance. In addition, high CB loading in MPL decreases condensation rate of product water at cathode CL and effectively reduces water flooding at CL/MPL interface.

Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation.

Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces. Numerous efforts have been made to create surfaces which can promote dropwise condensation, including superhydrophobic surfaces on which water droplets are highly mobile. However, the challenge with using such surfaces in condensing environments is that hydrophobic coatings can degrade and/or water droplets on superhydrophobic surfaces transition from the mobile Cassie to the wetted Wenzel state over time and condensation shifts to a less-effective filmwise mechanism. To meet the need for a heat-transfer surface that can maintain stable dropwise condensation, we designed and fabricated a hybrid superhydrophobic-hydrophilic surface. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values, and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for silanized silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles is low-cost, robust, and scalable and so could be used for heat transfer and water collection applications.

Droplet activation parameterization: the population-splitting concept revisited

Abstract. In this work, we postulate, implement and evaluate modifications to the "population-splitting" concept, introduced by Nenes and Seinfeld (2003), for calculation of water-condensation rates in droplet-activation parameterizations. The population-splitting approximation consists of dividing the population of growing droplets into two categories: those that experience significant growth after exposed to a supersaturation larger than their critical supersaturation, and those that do not grow much larger than their critical diameter. The modifications introduced here lead to an improved accuracy and precision of the parameterization-derived maximum supersaturation, smax, and droplet-number concentration, Nd, as determined by comparing against those of detailed numerical simulations of the activation process. A numerical computation of the first-order derivatives ∂ Nd/∂ χj of the parameterized Nd to input variables χi was performed and compared against the corresponding parcel-model-derived sensitivities, providing a thorough evaluation of the impacts of the introduced modifications in the parameterization ability to respond to aerosol characteristics. An evaluation of the parameterization computation of Nd and smax against detailed numerical simulations of the activation process showed a relative error of −6.0% ± 6.2% for smax, and −2.7% ± 4.8% for Nd, which represents a considerable reduction in prediction bias when compared to earlier versions of the parameterization. The proposed modifications require only minor changes for their numerical implementation in existing codes based on the population-splitting concept.

Chemical injection policy for internal corrosion prevention of South Pars sea-pipeline: A case study

Ten phases of south pars in five independent gas processing plants (GPP) are located on the Iranian coast of the Persian Gulf. In each phase, raw gas is taken from the on-veil platform and transferred in a multi-phase form through 32-inch submarine pipeline at a distance of 110 km from shore. In GPP No 1 or Phase 1, gas is daily extracted from two on-veil platforms and the gas-water separation as dehydration policy is performed on the platform. In order to preserve the pipes and avoid hydrate and corrosion, Mono Ethylene Glycol (MEG) accompanied by corrosion inhibitor as corrosion inhibition policy (in GPP No. 3, 5) or MDEA as pH stabilization policy (in GPP No. 2, 4) is transferred to the platforms via two 4.5-inch pipelines and injected into the submarine pipeline. Sludge and scale deposits formed within the pipeline as byproducts of the corrosion inhibition and PH stabilization techniques, respectively. The derivation of the field partitioning of MEG, ferrous ion, calcium, chloride, pH and weight loss coupons provide useful information concerning the sealine corrosion and scale accumulation. Heat transfer analyses of submarine pipeline show that the water condensation rate and top of the line corrosion can occur with the loose concrete and any pipe coating defects. The results show that the pH stabilization with the separation of brine water which is located in offshore has better performance than corrosion inhibition policy.