Evaporation Parameters Research Articles

냉장고용 핀-튜브 증발기의 착상 성능해석에 관한 연구

The objective of this study is to provide numerical and experimental data that can be used to investigate the performance characteristics of a flat plate fin-tube evaporator in household and commercial refrigerators under frosting conditions. Computer simulations with variations of operating conditions such as air inlet temperature, relative humidity, and geometries were performed to find out optimal design parameters of a fintube evaporator for household and commercial refrigerators. The tube-by-tube method was used in the simulation and the frost growth model was considered under frosting conditions. The developed analytical model predicted the decreasing rates of heat transfer capacity and air flow rate ratio within ± 10% compared to the experimental results for a refrigerator under real operating conditions. As a result, the frost thickness at 3 ℃ & 80% is increased 40% than that of -3 ℃ & 80%, and the frost thickness at 3 ℃ & 90% is increased 30% than that of 3 ℃ & 60%. Accordingly, the operating time of the evaporator in the refrigerator was reduced with the increase of the decreasing rate of air flow rate ratio at each condition.

Variation of infiltration rate through karstic surfaces due to land use changes: A case study in Murgia (SE-Italy)

Groundwaters of the Murgia carbonate aquifer represent the main groundwater resource of the Apulia region (SE Italy). In the highlands (Alta Murgia) karst crops out in different forms and textures which have been preserved up to the 1970s: little evolved agriculture and sheep rearing produced only a marginal modification of the epikarst while a high degree of division into parcels by drystone walls helped in preserving soils from erosion. In the last years the original scenery of the Alta Murgia changed due to widespread transformations of surface karstic textures for agricultural purposes, with undeniable negative consequences on the hydrogeological balance, concerning both the infiltration and the runoff terms. Stone shattering led to flattening and deep alteration of a large part of the original karstic landscape and to demolition of drystone walls. In a study area of about 139 km 2 located in the Alta Murgia, the comparison of aerial photos related to the period 1950–2001 indicated that stone shattering had occurred for about 42% of the area. The hydrological behaviour of the first soil layer of experimental parcels representing both shattered stone and natural karstic surface textures was analysed by using the numerical model Hydrus-2D with the aim of estimating the variation on infiltration rate due to stone shattering. Intensive field and laboratory measurements concerned soil texture, soil water content, pressure head, saturated hydraulic conductivity, pan evaporation and meteorological parameters.

Specific features of the evaporation of C60 films

The evaporation of pure C60 films is investigated. The rates of evaporation of the fullerene are experimentally measured, and the saturated vapor pressures are determined in the temperature range 250–290°C. The influence of atmospheric oxygen and ultraviolet irradiation on the rate of evaporation of the fullerene is studied. It is shown that the evaporation parameters of pure C60 films differ substantially from the reference values.

Singly charged tungsten and tantalum ions observed during high-temperature field evaporation

High-temperature field evaporation of tungsten and tantalum emitters in the temperature range from room temperature to 2500 K is studied using a static magnetic mass spectrometer equipped with a field source of ions. At room temperature, triply charged W3+ and Ta3+ ions alone are observed in the mass spectra. However, as the emitter temperature grows, the charge of the ions decreases. At T ≈ 1000 K, doubly charged W2+ and Ta2+ ions dominate in the spectra, and singly charged W+ and Ta+ ions appear in the temperature range 1900 < T < 2500 K. The evaporation rate of the singly charged ions is one to two orders of magnitude lower than the evaporation rate of the doubly charged particles. The energy parameters of field evaporation for differently charged tungsten ions are found.

Estimation of evaporative fraction and evapotranspiration from MODIS products using a complementary based model

We present a new formulation to derive evaporative fraction (EF) and evapotranspiration (ET) maps from remotely sensed data without auxiliary relationships or site-specific relationships. This formulation is based on Granger's complementary relationship and Priestley–Taylor's equation. The proposed model eliminates the wind function and resistance parameters commonly applied to ET calculation by including a relative evaporation parameter (ET/Epot). By combining this relative evaporation parameter, Granger's complementary relationship and Priestley–Taylor equation, we obtain a simple equation to estimate ET. We tested and validated the proposed formulation over the Southern Great Plains (SGP) region of the United States for seven clear sky days during March–October 2003. MODIS Atmospheric and Land products were the only source of data used in this study. Estimates of ET show an overall root mean square error and bias of 33.89 and − 10.96 Wm − 2 , respectively. Our results suggest that the proposed approach is robust and valid for a wide range of atmospheric and surface conditions.

Improved antigen retrieval in freeze-fracture cytochemistry by evaporation of carbon as first replication layer

The recently developed freeze-fracture replica immunolabeling technique uses sodium dodecyl sulfate to clean replicas obtained from chemically unfixed, rapidly frozen cells by evaporation of platinum as first and carbon as second replication layer. The detergent dissolves remains of cellular material with the exception of components which are in direct contact to the replica film. Membrane lipids and membrane protein complexes of the protoplasmic and the exoplasmic membrane halves remain attached to the replica film and are accessible for cytochemical localization. We immunolabeled the membrane proteins caveolin-1 and connexin 43 in mouse cell lines as well as the membrane attached protein tetrachloroethene reductive dehalogenase (PceA) in bacterial cells at freeze-fracture replicas generated by different evaporation parameters. The labeling experiments for caveolin-1 and the PceA showed that freeze-fracture replication of cellular membranes accomplished with thin platinum layers as well as replication with carbon as first evaporation layer lead in these cases to an improved antigen retrieval, whereas the labeling efficiency of connexin 43 was not affected by different evaporation conditions.

Investigation of the site occupation of atoms in pure and doped [formula omitted] intermetallic

Dual-phase TiAl/Ti 3 Al -alloys consisting of a lamellar structure, comprising γ -phase plus a small amount of α 2 -phase, with addition of 1, 5 and 10 at% Nb were prepared. The samples were investigated by means of field ion microscopy (FIM) and atom probe tomography (APT). The influence of doping elements on the variation of field evaporation and microstructural parameters in the γ -phase as studied by FIM and APT will be reported in this contribution. The intermetallic γ -Phase of TiAl exhibits a L1 0 -structure, which has alternating Ti- and Al-planes in the [0 0 1]-superstructure direction. Because of the significant difference in the evaporation field strengths of Ti and Al, it is usually not possible to directly distinguish Ti- and Al-planes in this direction in the APT data. Therefore, it is not possible to assign Nb to any plane, as well. To solve this problem an algorithm, using statistical methods, was developed, which allows to inherently distinguish the planes. A comparison of the results for [1 0 0]- and [0 0 1]-directions shows that Nb prefers Ti-sites. The sequence of field evaporation field strengths, which follows the trend E Nb > E Al > E Ti , could also be deduced.

Using Lidar Remote Sensing for Spatially Resolved Measurements of Evaporation and Other Meteorological Parameters

Remote sensors are useful tools for making measurements that are not possible with conventional point instruments. We developed methods to obtain spatially resolved latent energy fluxes from Raman water vapor data and the regional virtual potential heat flux from elastic lidar data. The evaporation method is based on Monin–Obukhov similarity theory applied to spatially and temporally averaged data. Latent heat flux estimates were found to be well correlated (R2 = 0.84, slope = 0.98) compared with eddy correlation measurements. The standard error of the flux estimates was 36.5 W m−2 (a 14% root mean square [RMS] difference), which is close to the predicted uncertainty of 15%. A vertically staring elastic lidar was used to obtain a continuous record of the boundary layer height and thickness of the entrainment zone between a soybean [Glycine max (L.) Merr.] and a corn (Zea mays L.) field. The surface heat flux was calculated using the Batchvarova–Gryning boundary layer model. The virtual potential heat flux estimates were found to be well correlated (R2 = 0.79, slope = 0.95) compared with eddy correlation measurements. The standard error of the flux estimates was 21.4 Wm−2 (31% RMS difference between estimates and surface measurements), higher than the predicted uncertainty of 16%. Other parameters such as the Monin–Obukhov length, the stability correction functions, and integral scale can be obtained from lidar data.

Effect of evaporative pattern casting process parameters on the surface roughness of Al–7% Si alloy castings

Evaporative pattern casting (EPC) process has drawn great attention from both academia and industry in recent years. The expandable polystyrene (EPS) pattern is a key feature of EPC process which is buried in unbonded sand and replaced by molten metal. This paper investigates the effect of process parameters like degree of vacuum, pouring temperature, grainfiness number, amplitude of vibration and time of vibration on the surface roughness of Al–7% Si alloy castings in EPC process. In order to evaluate the effect of selected process parameters, the response surface methodology (RSM) is used to formulate a mathematical model which correlates the independent process parameters with the desired surface roughness. The central composite rotatable design has been used to conduct the experiments. The analysis of results indicates that the surface roughness increases with increase in degree of vacuum, pouring temperature. Whereas, it has an inverse relationship with grainfiness number, amplitude of vibration and time of vibration.

New lessons on the Sudd hydrology learned from remote sensing and climate modeling

Abstract. Despite its local and regional importance, hydro-meteorological data on the Sudd (one of Africa's largest wetlands) is very scanty. This is due to the physical and political situation of this area of Sudan. The areal size of the wetland, the evaporation rate, and the influence on the micro and meso climate are still unresolved questions of the Sudd hydrology. The evaporation flux from the Sudd wetland has been estimated using thermal infrared remote sensing data and a parameterization of the surface energy balance (SEBAL model). It is concluded that the actual spatially averaged evaporation from the Sudd wetland over 3 years of different hydrometeorological characteristics varies between 1460 and 1935 mm/yr. This is substantially less than open water evaporation. The wetland area appears to be 70% larger than previously assumed when the Sudd was considered as an open water body. The temporal analysis of the Sudd evaporation demonstrated that the variation of the atmospheric demand in combination with the inter-annual fluctuation of the groundwater table results into a quasi-constant evaporation rate in the Sudd, while open water evaporation depicts a clear seasonal variability. The groundwater table characterizes a distinct seasonality, confirming that substantial parts of the Sudd are seasonal swamps. The new set of spatially distributed evaporation parameters from remote sensing form an important dataset for calibrating a regional climate model enclosing the Nile Basin. The Regional Atmospheric Climate Model (RACMO) provides an insight not only into the temporal evolution of the hydro-climatological parameters, but also into the land surface climate interactions and embedded feedbacks. The impact of the flooding of the Sudd on the Nile hydroclimatology has been analysed by simulating two land surface scenarios (with and without the Sudd wetland). The paper presents some of the model results addressing the Sudd's influence on rainfall, evaporation and runoff of the river Nile, as well as the influence on the microclimate. The paper presents a case study that confirms the feasibility of using remote sensing data (with good spatial and poor temporal coverage) in conjunction with a regional climate model. The combined model provides good temporal and spatial representation in a region characterized by extremely scarce ground data.

Controlling Cell Growth by Nanoparticles

ABSTRACTWe report preliminary results of using nanoparticles to control cell attachment and growth. We present the way to create titanium surfaces with different roughness in a rage between 2 nm and 117 nm by using nanoparticles as a superficial layer and varying the evaporation parameters. We examined cell proliferation on titanium substrates with increased surface roughness compared to smooth titanium surface. We used nanoparticles to create a micrometer-sized lateral layout onto substrates preliminary structured by microcontact printing. We demonstrate controlled cell growth on substrates laterally structured with nanoparticles.

A field study of hydraulic, geochemical and stable isotope relationships in a coastal wetlands system

Both chemical and stable isotope data provide important supplemental information to more traditional hydraulic data and unravel the processes that underpin the large variations in chemical and stable isotopic composition within a coastal wetland system. The system studied was the Lake Warden wetlands, located in Esperance, in south coast of Western Australia. The spatial and temporal variations of chemical and isotopic composition of the individual water bodies within the system were measured for an annual cycle. In broad terms, the groundwater levels appear to follow the topography but the distinct higher chloride and isotopic concentrations observed within the wetlands were not reflected in the low lying coastal plain groundwater. The hydraulic analysis of the region surrounding the wetlands suggest that the wetlands are flow-through bodies, however the chemical and isotope information indicates the lakes almost invariably act as discharge points for the surface water flows and the north-south groundwater flow. The northeast–southwest groundwater flow is along an observed paleochannel within the wetlands system and in this case the chemical and isotopic evidence are complimentary with the hydraulic study. The study highlighted the importance of correcting the isotopic values for the salt effect in highly saline water. The isotopic activity ratios of δ 2H ( δ 2H a) of some samples were up to 15‰ higher than the uncorrected values. The high salinity of the terminal lake in the wetlands chain also required implementation of a theoretical evaporative model to explain the lower enrichment of the isotopic results as compared to expectations for a shallow and ephemeral lake. The inter-lake variation in the theoretical evaporative model parameters, coupled with a significant variation in the hydrochemistry and isotope composition suggests that the lakes within the wetlands system cannot be treated as single water body as is implied by the bathymetry survey.

Determination and correlation of heat transfer coefficients in a falling film evaporator

The aim of the work was to determine the heat transfer parameters of a single effect evaporator under different operating conditions, in order to extrapolate them to a multiple effect unit. The falling film evaporator consisted of 12 stainless steel vertical tubes, 1″ OD and 3 m long, having an evaporation capacity of 240 kg/h. In this unit the conditions of each effect of a multiple effect evaporator were simulated, varying the feed concentration and the pressure, setting in this way the saturation temperature and the transfer regime. Obtained values were correlated by means of an equation that links the heat transfer coefficient with the fluid properties, geometric parameters and flow conditions. Comparison with existing correlations was carried out.

Physical organogels: mechanism and kinetics of evaporation of the solvents entrapped within network scaffolding

A series of hydrocarbon gels (based on leaded petrol and decalin) using physically crosslinked networks have been prepared using Al-salt of fatty acid as the physical gelling agent. The effects of gel network scaffolding on the mechanism and kinetics of evaporation of the solvents from the gels were investigated using conventional, isothermal and modulated thermogravimetric analysis. It has been clearly observed that the evaporation of solvent from gels followed a complex evaporation pattern compared to the pure solvent. It appears that with increase in network scaffolding the maximum rate of evaporation of the solvent decreases and its distribution become broader. The activation energy of evaporation for these solvents was found not to be dramatically dependent on the concentration of the gelator and tightness of the network scaffolding. Amongst different methods employed, isothermal measurements provided reliable information about the mechanism of evaporation. Modulated thermogravimetric analysis proved to be an efficient method to achieve kinetic parameters of evaporation from a single dynamic experiment. Scanning electron microscopy was used to probe for both dry gelator and gel network after evaporation of the solvents for evaluation of their surface morphology.

The effect of operating conditions on the performance of a supersonic ejector for refrigeration

A previously developed one-dimensional model, based on a forward marching solution technique of the conservation equations has been used to study ejector operation and performance in a large range of refrigeration working conditions. Several important features of ejector operation characteristics were simulated. Global parameter values, their local distributions along the ejector including the temperature, the pressure and the Mach number were calculated for design and off design conditions. Operation parameters such as the entrainment ratio ω, compression ratios P exit/ P ev, P g/ P exit and the geometric ratio ( D/ D c) 2 were found to significantly affect performance. The impact of the generator, the evaporator, the condenser and related thermodynamic parameters, which have been assessed in this study, are summarized as: Fluid mixing conditions dictated by the fluid type, the mixing chamber geometry, the inlet and outlet constraints, may lead to off design operation with related stability and performance deterioration Internal superheat generation, due to inefficient mixing and normal shock waves is very important in off design operation Some degree of inlet superheat (around 5 °C) is necessary to prevent internal condensation but excess superheat is detrimental to the condenser efficiency at exit Generator pressure conditions and the evaporator temperature significantly affect ejector performance.

Monitoring of rabbit cornea response to dehydration stress by optical coherence tomography.

To evaluate the application of optical coherence tomography (OCT) for continuous noninvasive monitoring and quantification of the dynamics of corneal response after exposure of the cornea to dehydrating stress. The changes in central corneal thickness (CCT) and scattering properties of the cornea were monitored with OCT in rabbit cornea in vivo after topical application of a glycerin-based hypertonic agent (HA) or prolonged surface evaporation of the cornea. The observed changes in backscatter were correlated with the changes in corneal hydration. An inverse relationship was found between the logarithm of the intensity of backscatter within the cornea and the degree of corneal hydration at which the intensity of the backscatter changed up to 20 times between the peak of the de- and rehydration phases. An analytical relationship is derived between the magnitude of the backscatter from the stroma and the extent of corneal hydration. Furthermore, depending on the concentration of the drug, a peak overshoot in corneal thickness in the range of 40% to 90% was detected during the rehydration process after topical application of the HA. At a 100% concentration of HA, the average dehydration rate was 74 microm/min, whereas the average rehydration rate was 12.4 microm/min. The same parameters for surface evaporation were 2.7 and 1.5 microm/min, respectively. OCT may offer a unique capability to quantitatively monitor the dynamics of corneal response and to assess corneal function based on noninvasive detection of the changes in the optical properties and morphology of the cornea after topical application of dehydrating agents.

The Impact of Modeling Complexity and Two-Phase Flow Parameters on the Accuracy of System Modeling for Unitary Air Conditioners

Current air-conditioning system models seek to balance the level of code complexity with the speed of execution. Ideally, the simplest code possible that can accurately predict system performance is desired. To further understand this issue, two methods of modeling unitary air-conditioning systems are compared: a detailed, local approach and a simplified, global approach. These methods have been applied to two commercial unitary air conditioners for which extensive experimental data were obtained. The global approach predicted absolute system performance as well as or better than the local approach. In a separate analysis, the effects of two-phase modeling parameters on system model predictions were considered. The two-phase friction factors, heat transfer coefficients, and void fraction models were independently varied. The resulting system performance predictions were sensitive to variations in the air-side heat transfer coefficients and the void fraction model and not as sensitive to variations in the friction factor. Both the void fraction model and the condenser parameters mainly affect the compressor discharge pressure and the compressor power consumption. The evaporator parameters mainly affect the refrigerant mass flow rate and the heat transfer rates in both heat exchangers.

On quantifying soil water deficit of a partially wetted root zone by the response of canopy or leaf conductance

Abstract Quantifying the soil water deficit (SWD) and its relation to canopy or leaf conductance is essential for application of the Penman–Monteith equation to water-stressed plants. As the water uptake of a single root depends on the water content of the soil in its immediate vicinity, the non-uniform distribution of water and roots in the soil profile does not allow simple quantification of SWD from soil-based measurements. Using measurements of stem sap flux (with a heat pulse technique), soil evaporation (with micro-lysimeters) and meteorological parameters the canopy conductance was obtained through inversion of the Penman–Monteith equation. SWD was evaluated by averaging the soil water content profile of the root zone (monitored by layers with the TDR sensors) weighted by root distribution of the layers. The average canopy conductance at midday (11:00–15:00, Israel Summer Time), denoted as Gnoon, was computed for each day of the experimental period. Stable summer weather, typical of the Mediterranean region, and the fully developed crop canopy, made water stress the only plausible cause of a Gnoon decline. However, the daily decline of Gnoon did not occur at the same weighted average soil water content during the successive drying cycles. For the cycle with less irrigation, the decline in Gnoon occurred at higher soil moisture levels. Alternatively, when SWD was determined from the water balance, i.e., by defining water deficit as irrigation minus accumulated evapotranspiration, the Gnoon decline occurred at the same value of water deficit for all irrigation cycles. We conclude that a climate-based soil water balance model is a better means of quantifying SWD than a solely soil-based measurement.

Interfacial nonequilibrium and Bénard-Marangoni instability of a liquid-vapor system.

We study Bénard-Marangoni instability in a system formed by a horizontal liquid layer and its overlying vapor. The liquid is lying on a hot rigid plate and the vapor is bounded by a cold parallel plate. A pump maintains a reduced pressure in the vapor layer and evacuates the vapor. This investigation is undertaken within the classical quasisteady approximation for both the vapor and the liquid phases. The two layers are separated by a deformable interface. Temporarily frozen temperature and velocity distributions are employed at each instant for the stability analysis, limited to infinitesimal disturbances (linear regime). We use irreversible thermodynamics to model the phase change under interfacial nonequilibrium. Within this description, the interface appears as a barrier for transport of both heat and mass. Hence, in contrast with previous studies, we consider the possibility of a temperature jump across the interface, as recently measured experimentally. The stability analysis shows that the interfacial resistances to heat and mass transfer have a destabilizing influence compared to an interface that is in thermodynamic equilibrium. The role of the fluctuations in the vapor phase on the onset of instability is discussed. The conditions to reduce the system to a one phase model are also established. Finally, the influence of the evaporation parameters and of the presence of an inert gas on the marginal stability curves is discussed.

Low-resistivity Mo thin films prepared by evaporation onto [formula omitted] cm glass substrates

In order to obtain a suitable back contacting material for CuInSe 2-based photovoltaic devices, molybdenum thin films have been deposited onto glass substrates up to 30 cm×30 cm area using an electron beam evaporator. In the CuInSe 2-based devices, molybdenum has to provide the electrical properties of a low-resistivity electrode and must also serve as a part of the substrate during the growth of successive photovoltaic components, maintaining chemical and mechanical stability during the whole device fabrication process. Film thickness, sheet resistance, optical reflectance and surface roughness measurements have been performed for the Mo layers prepared at various deposition power and time. The film microstructure, such as the preferred orientation and the residual intrinsic stress, has been determined by X-ray diffraction. The electrical requisites for photovoltaic applications have been achieved for Mo layers evaporated at different experimental conditions with similar homogeneity over the substrate area. On the other hand, the intrinsic stress in Mo films has been found depending on the evaporation parameters, mainly on the thin-film deposition rate.