Vapor Region Research Articles

1D and Q2D thermal resistance analysis of micro channel structure and flat plate heat pipe

Heat pipes and two-phase heat transfer devices are widely used in electronics cooling, and the thermal resistance is a key issue to ensure the system performance and reliability. In this study, the traditional one dimensional (1D) and quasi-two dimensional (Q2D) methods were utilized to analyze the thermal resistance of the previous boiling experiments of evaporator tests with silicon (Si) and copper (Cu) micro channel structures as well as the existing flat-plate heat pipe tests with aluminum micro channels as wick structures. The temperature distributions and variations under different test conditions were collected, and the 1D and Q2D methods were applied to calculate the overall thermal resistance for evaporator tests and heat pipe tests and compared with the experimental data. The results showed that the Q2D method can predict the overall thermal resistance for the evaporator region and the whole heat pipe with a higher accuracy because the spreading resistance was significant and should be considered under small heater area (hot spot) conditions. Detailed distributions of thermal resistance and the calculated errors of each test sample under different heat loads were presented and compared. For present tests, the Q2D method can reach a lower average error (about 10%) and is recommended for calculations. Furthermore, the spreading resistance of Q2D method is further applied to calculate the selected test cases to investigate the wall thickness effects. The spreading resistance of the selected evaporator tests and heat pipe tests may decrease and increase, respectively, as wall thickness increases due to different evaporative heat transfer conditions. The present results demonstrate the applicability of the Q2D methods for both evaporator and heat pipe tests, and the present analyses can be a reference for future thermal management and electronic cooling designs.

Collection efficiency of <i>α</i>-pinene secondary organic aerosol particles explored via light-scattering single-particle aerosol mass spectrometry

Abstract. We investigated the collection efficiency and effective ionization efficiency for secondary organic aerosol (SOA) particles made from α-pinene + O3 using the single-particle capabilities of the aerosol mass spectrometer (AMS). The mean count-based collection efficiency (CEp) for SOA across these experiments is 0.30 (±0.04 SD), ranging from 0.25 to 0.40. The mean mass-based collection efficiency (CEm) is 0.49 (±0.07 SD). This sub-unit collection efficiency and delayed vaporization is attributable to particle bounce in the vaporization region. Using the coupled optical and chemical detection of the light-scattering single-particle (LSSP) module of the AMS, we provide clear evidence that delayed vaporization is somewhat of a misnomer for these particles: SOA particles measured as a part of the AMS mass distribution do not vaporize at a slow rate; rather, they flash-vaporize, albeit often not on the initial impact with the vaporizer but instead upon a subsequent impact with a hot surface in the vaporization region. We also find that the effective ionization efficiency (defined as ions per particle, IPP) decreases with delayed arrival time. CEp is not a function of particle size (for the mobility diameter range investigated, 170–460 nm), but we did see a decrease in CEp with thermodenuder temperature, implying that oxidation state and/or volatility can affect CEp for SOA. By measuring the mean ions per particle produced for monodisperse particles as a function of signal delay time, we can separately determine CEp and CEm and thus more accurately measure the relative ionization efficiency (compared to ammonium nitrate) of different particle types.

Numerical analysis on heat transfer of a complete anti-gravity loop-shaped heat pipe

Anti-gravity loop shaped heat pipe (AGLSHP) with continuous step-graded sintered wick is useful for enhancing the effective heat transfer in the anti-gravity direction. In this work, a complete steady state model has been presented to investigate in the thermal performance and hydraulic behavior of the AGLSHP. The governing equations for the heat and mass transfer are developed for the loop operation, with specific attention given to the evaporator region. By comparing the numerical simulation with the experimental data, the heat transfer mechanism is revealed. The liquid/vapor velocity and pressure distribution in the evaporator are discussed, and the temperature distribution along the transport line is also analyzed. The numerical results indicate that with the increase of the heat load, the maximum velocity and pressure value of the liquid and vapor increase as expected. The highest temperature position occurs at the outlet of evaporator surface. Providing the capillary pressure for the circulation of working fluid, the wick in the liquid line is paid more attention. Moreover, the longer condensation length is more effective in decreasing the temperature at the outlet of condenser and improving the heat transfer capacity of the AGSLHP.

The study on interface characteristics near the metal wall by a molecular dynamics method

The condensation process of the multiple-atom and polar water molecular at a solid wall is studied. It is found that a monomolecular layer structure is existed on the wall surface and the intensity of solid-liquid potential can be revealed by the monomolecular density peak. At high-temperature conditions, liquid drop in vapor and bubble near wall can be observed. The solid-liquid potential energy on monomolecular layer structure has a greater impact than on gas-liquid interface. The simulated densities in the vapor region are consistent with the macroscopic values by refprop8.0, while in the liquid region the simulated densities are a bit lower than the macroscopic ones. Besides, the solid-liquid-gas three-phase model consisting of argon, water, freon and copper was constructed using Materials Studio software, and their interface characteristics are studied.

A comparison of models for the evaporation of the Lennard-Jones fluid

The evaporation of a thin liquid film is studied by a diffuse interface model whose thermodynamic and transport properties are consistent with those of the Lennard-Jones fluid. Solutions are obtained for various liquid film temperatures and downstream vapor flow velocities. The results are compared with reference molecular dynamics simulations of a system of atoms interacting by the 6-12 Lenard-Jones potential. It is shown that the diffuse interface model underestimates the temperature drop across the non-equilibrium vapor region next to the liquid–vapor interface but overestimates the density drop, thus predicting smaller evaporation rates. Results indicates that the discrepancies between molecular dynamics and diffuse interface model predictions become smaller when the liquid film temperature approaches the critical temperature and the vapor becomes a dense, non-ideal gas. Further successful comparisons of molecular dynamics results with the predictions of a hybrid model, combining the continuum description of the liquid with the kinetic description of the vapor, suggest that the observed discrepancies can be attributed to poor description of the Knudsen layer provided by the diffuse interface model when the vapor phase is dilute.

Thermal characterization of crude oils in the presence of limestone matrix by TGA-DTG-FTIR

In present work oxidation of two heavy oils in limestone matrix was studied using simultaneous thermogravimetry (TGA), derivative thermogravimetry (DTG) and FTIR-spectroscopy techniques in the temperature range from 25 to 900°C. Before the measurements, the composition and properties of crude oils and limestone were evaluated. Obtained TG and DTG curves shows four different reaction regions: low temperature oxidation (LTO), fuel deposition (FD), high temperature oxidation (HTO) and decomposition of limestone. LTO reactions were accompanied by evaporation of light hydrocarbons, which was confirmed by appearance of stretching vibration bands of C-H groups in FTIR-spectra of evolved gases. Formation of carbon dioxide was observed for all oxidation reaction regions according to spectroscopic data. At the same time, CO was formed only in HTO region for both studied crude oils. Despite the different composition two crude oils have practically the same reactions intervals and peak temperatures. However, crude oil with higher API-gravity has a greater mass loss at the LTO and evaporation regions. The conversion of heavier oil with higher content of asphaltenes is larger during the high-temperature oxidation step.Three different kinetic models (Arrhenius, Coats & Redfern and Ingraham & Marrier) were used for analysis of TGA-DTG curves in LTO and HTO regions. Activation energy values of the crude oil samples were varied between 6.9–10.6kJ/mol in low temperature oxidation and 91.8-.0–181.9kJ/mol in high temperature oxidation regions. For two crude oils activation energies are similar in low temperature oxidation region. In high temperature oxidation region, crude oil with higher content of asphaltenes has larger activation energy.

Sedimentary <italic>n</italic>-alkanes record of precipitation D/H ratios in arid regions of the Tibetan Plateau

The hydrogen isotope ratios of sedimentary leaf waxes have been investigated in various environments and are considered as a promising proxy for paleohydrological and paleoclimatic reconstruction. However, there is a growing concern regarding whether or not sedimentary leaf waxes can be used as an environmental proxy in extremely arid regions, where intensified evaporation strongly enriches the deuterium both in water and in leaf waxes. Here we present a record of the n -alkane D/H ratios of surface sediments from 21 lakes. The data were collected from 2012–2014. The n -alkanes extracted from lake surface sediments range from n C16 to n C35, with the most abundant compounds being n C23, n C25, n C29 and n C31. In addition, there is an evident odd-over-even preference for long-chain n -alkanes, with carbon preference index (CPI) values varying between 3.41 and 10.75, suggesting that the long-chain sedimentary n -alkanes mainly originated from terrestrial plants in arid regions on the Tibetan Plateau. The D/H ratios of the precipitation ( δ Dp) atall the lakes in this studywere calculated using the Online Isotopes in Precipitation Calculator. The OIPC calculates precipitation isotope ratios at a given site by combining an empirical model for isotopic trends related to latitude and altitude with detrended interpolation based on the isotope data from stations in the Global Network of Isotopes in Precipitation. The mean annual hydrogen isotopes ratios of precipitation ( δ Dann) at the lakes in this study vary from - 78‰ to - 115‰, with lower precipitation δ D values occurring in the southern TP and higher values in the northern TP and the Qaidam Basin. The δ D values for summer precipitation (July–September, δ Dsum) range from - 68‰ to - 126‰, with a similar range of variation for δ Dann. The sedimentary n -alkane D/H ratios are strongly correlated with the D/H ratios of annual precipitation ( r 2=0.84) and summer precipitation ( r 2=0.91), suggesting that the hydrogen isotope signal in sedimentary n –alkanes is mainly derived from precipitation, and that the n -alkane D/H ratios may reflect the D/H ratios of precipitation in arid regions on the Tibetan Plateau. Water is the ultimate source of hydrogen in plant tissues, and organic matter derived from terrestrial plants should record the isotopic ratio of soil water, which is ultimately recharged by precipitation. The δ D values of n -alkanes in lake surface sediments could thus be expected to be correlated with the δ D values of precipitation, on a large spatial scale. Furthermore, precipitation on the Tibetan Plateau mainly occurs from July to September, which accounts for ~70% during the year, and the n -alkanes of leaf wax are synthesized during the plant growing season. Therefore, it is unsurprising that the best correlation between D/H ratios of sedimentary leaf wax and precipitation occurs in the summer months. The apparent hydrogen isotopic fractionation between sedimentary n -alkanes and precipitation averages - 113‰, evidently smaller than that in relatively humid regions. A possible reason for the smaller apparent fractionation might be spatial differences in soil evaporation and plant transpiration. Mean annual precipitation amount and mean annual evaporation at the studied lakes is 207 and 2343 mm, respectively. However, in the humid areas, such as the southeastern TP, the mean annual precipitation amount and mean annual evaporation are 1298 and 795 mm, respectively. Due to the strong evaporation in arid regions, the δ D values of soil water and plant water are more isotopically-enriched relative to precipitation than those in humid regions. Overall, our results demonstrate that sedimentary n -alkanes can be used as a proxy indicator of variations in the isotopic composition of summer precipitation, in order to document past changes in summer monsoon intensity and hydrology.

Interaction of Levitating Microdroplets with Moist Air Flow in the Contact Line Region

ABSTRACTSelf-organization of levitating microdroplets of condensate over a liquid–gas interface has been observed in several recent experiments involving evaporation at high heat fluxes, although the nature of this phenomenon is still not completely understood. We conduct an experimental investigation of the behavior of such an ordered array of microdroplets as it approaches a region of intense evaporation near the contact line. Interaction of the array with the local highly nonuniform gas flow results in breakup of the pattern. Some droplets fly over the contact line region and end up above the dry part of the solid substrate, whereas others are trapped before they approach the contact line. Our experimental setup provides a unique tool for investigation of the moist air flow near the contact line by using microdroplets as tracers. Local gas flow velocities near the contact line are obtained based on trajectories of the droplets.

CFD Study on Emergency Core Cooling of Hot Vertical Nuclear Fuel Rod Bundle by Jet Impingement

The rewetting is the process of re-establishment of coolant with hot surfaces. This rewetting characteristic influence on cooling of nuclear rod bundles was conducted using CFD-CFX code. The numerical results are compared with experimental result and achieved good agreement. The present study intended in the prediction of rewetting behavior in rod bundle. It is observed that the rewetting behavior was significantly affected by phase distribution. It is seen that the peak rewetting temperature appears in the vapor region. The wetting delay is negligible at inlet section, but longer period is observed in others section of the rod bundle. It was noted that the complication of rewetting regimes is due to the uneven and irregular flow of coolant which affect re-establishment of coolant into hot surface.

CFD Analysis of Multi turn Pulsating Heat pipe

Pulsating Heat Pipe (PHP) is a heat exchanger device which absorbs heat from evaporator region and transfers it to the condenser region. The flow in pipe is Multi-Phase flow. Vapour plugs and Liquid slugs are formed in PHP due to the capillary action.CFD modeling is done in ANSYS CFX with two turns of PHP and Methanol is used as the working fluid and a fill ratio of 60%. At evaporator boundary, heat flux that is equivalent to 10 W to 70 W is supplied and the condenser boundary is set as heat flux of range 4423 W/m^2 and in the adiabatic section heat flux is zero. The obtained CFD results are compared with the experimental paper [1].The CFD analysis is performed and the outputs of the simulations are plotted in graphs and contours. Decrease in the methanol temperature at the evaporator suggests that heat is carried away to the condenser part. Change in volume fractions of methanol and air in three regions viz. evaporator, adiabatic region and condenser reflects to the flow pattern of the fluid inside the PHP.

EXCIPLEX TECHNIQUE FOR SIMULTANEOUS VISUALIZATION OF THE LIQUID AND VAPOR PHASES OF PILOT-INJECTED SPRAY BY LASER-INDUCED FLUORESCENCE

An optically accessible single-cylinder compression-ignition two-stroke research engine equipped with dual-injection system, image acquisition, and control system have been designed to acquire two-dimensional images of the pilot and main diesel fuel sprays. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency tripled to operate at the ultraviolet wavelength of 355 nm. The liquid fuel was decane with TMPD-naphthalene dopant dispersed in it. After ultraviolet excitation by the pulsed laser, liquid fuel regions fluoresced with a spectrum centered at the wavelength of 380 nm, while vapor regions fluoresced with a spectrum centered at 470 nm. This approach, called Exciplex technique, was applied to permit simultaneous acquisition of the liquid and vapor fuel regions in the cup-in-head geometry of the combustion chamber. The results from limited conditions suggest that existence of the pilot injection affects the chamber flow field, particularly in the near-wall region, in such a way that less liquid fuel accumulation occurs with pilot injection scheme thus should reduce hydrocarbon emission. The area spreading rate of both vapor and liquid phases within the visualization plane were linear in early stages with former having a higher rate. Close to the impingement time, vapor phase area penetration is reduced to near zero, while liquid continues linearly but at slower rate than its initial value. Both air utilization and evaporization are therefore reduced. Also, based on this and work by others, the suggestion is made that to achieve optimum simultaneous reduction in soot and NOx, the timing between the pilot and main injections (dwell) should be chosen with due consideration of the interaction between the swirl flow and pilot spray and the relative magnitudes of the ignition delay period with respect to the dwell.

Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

Abstract. Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IR vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.

Flexible Thermal Ground Planes Fabricated With Printed Circuit Board Technology

Thermal ground planes (TGPs) are passive thermal management devices that utilize the phase-change of a working fluid to achieve high thermal conductivity and low thermal resistance. TGPs are flat, two-dimensional heat pipes—similar to vapor chambers—in which liquid is held within a capillary wick, and vapor is held in a sealed vapor layer. Heat is absorbed at an evaporator region, causing the liquid to evaporate. The heated vapor in the vapor core is carried via convection to a condenser region where it condenses as the heat is expelled from the TGP to an external heat sink. The condensed liquid is then pulled back to the evaporator via capillary forces in the wick. In numerous applications, mechanical flexibility of the TGP is required, as is low-cost manufacturing and viable integration routes with electronics. This work describes a flexible TGP (FTGP) fabricated using printed circuit board (PCB) technology, in which commercially available copper-cladded polyimide sheets are used as the casing material. The wick is composed of three layers of fine copper mesh electroplated or sintered together and coated with atomic layer deposited TiO2. A coarse nylon or polyether ether ketone (PEEK) mesh defines the vapor transport layer, and water is used as the working fluid. The perimeter of the device is heat-sealed with flouroethylene propylene (FEP), which has been found to provide a near-hermetic seal for several months and is suitable for flexible applications. This architecture allows the TGP to function with minimal reduction in heat transfer performance while bent by 90 deg, and full functionality is returned when the device is returned to its flat configuration. The FTGP's measured thermal resistance is about half that of an equivalent copper reference for input heat fluxes of 3–6 W/cm2. More than 30 copper-cladded polyimide FTGPs were fabricated and characterized using both simple qualitative and more involved quantitative test setups. The results show that the fabrication and assembly processes developed in this work are repeatable and the devices are durable.

Regional evaporation estimates in the eastern monsoon region of China: Assessment of a nonlinear formulation of the complementary principle

AbstractThe performance of a nonlinear formulation of the complementary principle for evaporation estimation was investigated in 241 catchments with different climate conditions in the eastern monsoon region of China. Evaporation ( ) calculated by the water balance equation was used as the reference. estimated by the calibrated nonlinear formulation was generally in good agreement with the water balance results, especially in relatively dry catchments. The single parameter in the nonlinear formulation, namely as a weak analog of the alpha parameter of Priestley and Taylor (), tended to exhibit larger values in warmer and humid near‐coastal areas, but smaller values in colder, drier environments inland, with a significant dependency on the aridity index (AI). The nonlinear formulation combined with the equation relating the one parameter and AI provides a promising method to estimate regional with standard and routinely measured meteorological data.

Reconstruction of soil water oxygen isotope values from tree ring cellulose and its implications for paleoclimate studies

Abstract We present here a rationale for estimation of soil water oxygen isotope values ( δ sw ) from tree ring cellulose oxygen isotope data and examine, for the first time, its ( δ sw ) efficacy as a tool to obtain paleoclimate information. We analyzed pre-dated tree ring cellulose samples collected from a site at Western Himalaya for oxygen isotopes, used similar dataset of overlapping time period from 12 different locations across the world, reconstructed δ sw for 1901–2004 CE, compared the data with available observations and examined implications of this technique. Our study shows (a) good agreement in spatial ranges between observed and estimated δ sw data suggesting its suitability for a representative parameter, and (b) reconstructed δ sw largely depend on soil moisture content modulated by regional evaporation regimes. Considering a growing importance of measurement of recycled soil moisture and its ensuing role in rainfall amount, a method to reconstruct soil moisture isotope as presented in this work will enable application of land hydrological models to the past.

Lake Evaporation in a Hyper-Arid Environment, Northwest of China—Measurement and Estimation

Lake evaporation is a critical component of the hydrological cycle. Quantifying lake evaporation in hyper-arid regions by measurement and estimation can both provide reliable potential evaporation (ET0) reference and promote a deeper understanding of the regional hydrological process and its response towards changing climate. We placed a floating E601 evaporation pan on East Juyan Lake, which is representative of arid regions’ terminal lakes, to measure daily evaporation and conducted simultaneous bankside synoptic observation during the growing season of 2013–2015. A semi-empirical evaporation model derived from Dalton model was parameterized and validated with measured data. The model was then used to estimate lake evaporation during 2002–2015. According to in situ measurements, maximum, minimum and mean lake evaporation were 8.1, 3.7 and 6.5 mm/day, and growing season evaporation was 1183.3 mm (~80% of the annual amount). Adding up non-growing season evaporation that we converted from φ20 pan evaporation at Ejina weather station, the annual mean lake evaporation, 1471.3 mm, was representative of lower Heihe River’s ET0. Model inter-comparison implied our model performed well both in simplicity and accuracy and has potential utilization in a data-sparse area. In 2002–2015, estimated mean daily evaporation was 6.5 mm/day and growing season evaporation was 1233.7 mm. Trend analysis of estimated evaporation proved the evaporation paradox’s existence in this hyper-arid region and validated complementary relationship theory’s adaptability.

Experimental study of the heated contact line region for a pure fluid and binary fluid mixture in microgravity

Understanding the dynamics of phase change heat and mass transfer in the three-phase contact line region is a critical step toward improving the efficiency of phase change processes. Phase change becomes especially complicated when a fluid mixture is used. In this paper, a wickless heat pipe was operated on the International Space Station (ISS) to study the contact line dynamics of a pentane/isohexane mixture. Different interfacial regions were identified, compared, and studied. Using high resolution (50×), interference images, we calculated the curvature gradient of the liquid-vapor interface at the contact line region along the edges of the heat pipe. We found that the curvature gradient in the evaporation region increases with increasing heat flux magnitude and decreasing pentane concentration. The curvature gradient for the mixture case is larger than for the pure pentane case. The difference between the two cases increases as pentane concentration decreases. Our data showed that the curvature gradient profile within the evaporation section is separated into two regions with the boundary between the two corresponding to the location of a thick, liquid, “central drop” region at the point of maximum internal local heat flux. We found that the curvature gradients at the central drop and on the flat surfaces where condensation begins are one order of magnitude smaller than the gradients in the corner meniscus indicating the driving forces for fluid flow are much larger in the corners.

Confinement-Induced Supercriticality and Phase Equilibria of Hydrocarbons in Nanopores.

For over a century, the phase behavior of bulk fluids has been described as PVT (pressure-volume-temperature) three-dimensional properties, but it has become increasingly clear that the liquid-vapor phase behavior in confined geometries is significantly altered from the bulk. Efforts have been devoted to accessing confined phase transitions using sorption, molecular simulations, and theoretical methods. However, a comprehensive picture of PVT relationships for confined hydrocarbons remains uncertain. Herein, we introduce d (confining pore diameter) as a fourth dimension, and we present PVT-d behavior of confined fluids in nanopores. For the first time, a T-d phase diagram is presented for n-hexane, n-octane, and n-decane under multiple confinement scales (37.9, 14.8, 9.8, 6.0, 4.1, 3.3, and 2.2 nm cylindrical pore diameter) using experimental differential scanning calorimetry and PVT-d equation of state theory at atmospheric pressure. As pore diameter decreases from 37.9 to 4.1 nm, the bubble point increases by as much as 15 K above bulk, until we observe behavior consistent with a supercritical state, pointing to confinement-induced supercriticality. Remarkably, experimental and theoretical findings overlap very well, showing that this approach effectively captures the phase boundaries between the liquid, vapor, and supercritical fluid regions. The model and completed EOS are additionally extended to calculation of isothermal capillary adsorption, and its validity is discussed.

Experimental and Numerical Study of Multiphase, Multicomponent Flow in Porous Media with a Multiphase Mixture Model

This article describes experimental results and the numerical validation for multiphase, multicomponent evaporation in porous media 1d flow. We apply the model of Lindner et al. (Transp. Porous Media 112(2):313–332, 2016. doi:10.1007/s11242-016-0646-6). The permeability of the porous medium is measured in an additional setup with a constant head permeameter to verify the validity of Darcy flow. The heat losses are considered in an analytical approach of correlating measured temperatures and heat inputs with enthalpies. A method of interpreting the experimental results is discussed to determine the phase state. We can show good qualitative agreement of the shift and position of the evaporation region when varying boundary conditions such as mass flux, concentration and heat input.

Surface-Subface Geochemical and Mineralogical Study of Gypcrete in Alexandria Area Central Iraq

Gypsiferous soil deposits (Gypcrete) are weakly consolidate earthy mixture of secondary gypsum, sand and clay. It is formed in arid and semi- arid area with annual precipitation rainfall less than 400mm. These sediments occur in surface and subsurface in region of little rainfall and rapid evaporation. This research deals with the study of gypcrete in Alexandria to improve the mineralogical and geochemical properties of the gypcrete. The gypcrete soil is used as raw material to produce the plaster for building purposes. Three samples of gypcrete were chemically and geochemically analyzed. The common mineral is howed in 0-0.5m Gypsum followed by Calcite in 0-1m and Quartz in 1-1.5m due to leaching and infiltration by rainfall as well as it full the clay Matrix and the voids between soil constituent, therefore soil properties changes with depth and the clay materials increases such as (Al, Na and K oxides) and Gypsum compound decreases (Ca, S and Sr oxides), yet the change in element concentration, takes the same path. This indicate that annual season rainfall is the only factor affecting mineralogy in this arid area and this means that the Gypsum concentration cannot be affected by ground water either increasing or decreasing. This research concerns about mineralogy and element occurrence variation in this material with accordance to their concentration from surface to depth of 1.5 meter.