Mass Of Silica Gel Research Articles

Design of silica gel/water adsorption chiller powered by solar energy for air conditioning applications

The design and thermo-economic studies for a silica gel/water solar adsorption cooling system are presented in this paper using Simulink to perform a numerical analysis of refrigeration systems employing a pair of silica gel and water. A case study for modelling the adsorption system with several cooling load capacities ranging from 10 to 100 Ton of Refrigeration (TR) was also presented. The simulation output results include the desorber temperature, the temperatures of hot water and chilled cooling, the temperatures of two adsorption/desorption beds, condenser and evaporator, the refrigerant and silica gel mass, area, and cost of all parts in the system, mass flow rate and thermal power. Results showed that the cost of the system and the mass of the silica gel were 20,708.4$ and 2266 kg, respectively for 10 TR cooling load, while for 100 TR cooling capacity, it was 189,169.6$ and 22,667 kg, respectively. Results also showed that when the cooling load increased from 10 TR to 100 TR, the area of the condenser, evaporator, bed, and collector increased, and the mass flow rate of the collector, condenser cooling water, chilled water, and the cooling circuit increased with a percentage increase of 9 times.

A novel desiccant compound for air humidification and dehumidification

• A novel silica gel-based desiccant material for open air systems is proposed. • Silica gel is mixed with sodium polyacrylate, vinyl glue and polypropylene fibers. • The maximum water uptake on dry silica gel mass basis is equal to 0.32 kg kg −1 . • Thermal and sorption stability of new and on-purpose aged samples are observed. • Dehumidification capacity is around 3.5 g kg −1 when the regeneration occurs at 52 °C. Currently, there is an increasing interest in the development of HVAC systems based on solid desiccant materials to achieve efficient and affordable air dehumidification and humidification processes. Many research efforts deal with the development of novel composite materials suitable to manufacture such devices. In this work we present a novel silica gel-based desiccant compound, which can be used to prepare different products, such as sheets, monolithic components, and coatings. The proposed formulation is based on a combination of silica gel, sodium polyacrylate, vinyl glue and polypropylene fibers. The preparation procedure of the sorbent material and its characterization (adsorption capacity, morphology and surface analysis, mechanical properties by pull-off test, structural and thermal stabilities of new and aged samples and volatile compounds emissions) are described in detail. A small-scale prototype has been also manufactured and experimentally tested under typical operating conditions of air dehumidification processes. Results show that the proposed material has a suitable sorption capacity (maximum water uptake equal to 0.32 kg kg −1 ), good mechanical properties (pull adhesion strength around 2.74 MPa) and stability (decomposition threshold of 400 °C). The performances achieved by the prototype are comparable with those of a reference silica gel packed bed system, highlighting that the desiccant material performs adequately also at system scale.

Possibility of Advanced Modified-Silica-Based Porous Materials Utilisation in Water Adsorption Processes—A Comparative Study

Due to a high risk of power outages, a heat-driven adsorption chillers are gaining the attention. To increase the efficiency of the chiller, new adsorbents must be produced and examined. In this study, four newly developed silica–based porous materials were tested and compared with silica gel, an adsorber commonly paired with water. Extended sorption tests using mercury intrusion porosimetry, gas adsorption, and dynamic vapor sorption were performed. The morphology of the samples was determined using a scanning electron microscope. The thermal properties were defined using simultaneous thermal analysis and a laser flash method. Metal organic silica (MOS) nanocomposites analysed in this study had thermal properties similar to those of commonly used silica gel. MOS samples have a thermal diffusivity coefficient in the range of 0.17–0.25 mm2/s, whereas silica gel of about 0.2 mm2/s. The highest water adsorption capacity was measured for AFSMo-Cu and equal to 33–35%. For narrow porous silica gel mass uptake was equal about 25%. In the case of water adsorption, it was observed that the pore size of the sorbent is essential, and adsorbents with pore sizes higher than 5 nm, are most recommended in working pairs with water.

The effects of crude C. inophyllum seed oil to silica gel mass ratio and number of stages on the isolation of wax

Calophyllum inophyllum is one of the most notable mangrove species that grows a lot in the coastal areas of the Indonesian archipelago. Despite its long lifespan (50 years) and abundant seed oil production, this plant has not been utilized optimally. Wax is reported as a constituent of C. inophyllum seed oil, but the quantity has not been discovered yet. Wax has been commonly used as ingredient in coating, cosmetic, food, and pharmaceutical industries. The aims of this work were to separate wax from C. inophyllum seed oil in high purity and investigate the effects of crude C. inophyllum to silica gel mass ratio and the stages number on wax isolation. Silica gel was employed to adsorb crude C. inophyllum seed oil. Mass ratios of C. inophyllum seed oil to silica gel used in this work were 1:4, 1:2, and 1:1 (g/g). After that, the seed oil adsorbed onto silica gel was extracted by soxhlet extraction with hexane as the solvent. Wax was separated by putting the hexane extract in cold storage at 4 ºC for 24 h. Furthermore, wax obtained was analyzed by High-Temperature Gas Chromatography (HT-GC) and confirmed by Thin-Layer Chromatography (TLC). It was found that wax (purity 93.2 % and yield 0.4 %) was best isolated by employing two-stage of adsorption-extraction, with crude C. inophyllum seed oil to silica gel mass ratio of 1:1 (g/g), followed by crystallization in cold acetone for 24 h. Moreover, wax content in crude C. inophyllum seed oil was 0.43%.

Calophyllolide Separation from <i>Calophyllum inophyllum</i> Oil by Silica Gel Adsorption

Nyamplung (Calophylluminophyllum), widely spreads in Indonesia archipelago, is known to have many advantages. It has various benefits that can be utilized from its root, stem, leaf, and seed. C inophyllum’s seed contains bioactive compounds called calophyllolide. However, the utilization of C. inphyllum’s seed is limited because it contains harmful toxins. Therefore, C. inophyllum’s seed is generally used and investigated as a raw material of biodiesel. This research aimed to find the best condition to isolate calophyllolide, to know the yield of isolated calophyllolide and to know its purity percentage from crude C. inophyllum oil. Current research on calophyllolide is to extract the substance from C. inophyllum’s shell nut without further treatment on it. In this work, calophyllolide was separated from crude C. inophyllum oil by silica gel adsorption. Each fraction obtained was tested qualitatively using Thin Layer Chromatography (TLC) and quantitatively using Gas Chromatography (GC) to analyze calophyllolide mixture. In this study, the best separation method (12.92% purity, 8.03% yield, and 95.02% recovery of calophyllolide) was obtained by using crude C. inophyllum to silica gel mass ratio of 1:2 (g/g).

Experimental investigation on anti-condensation characteristic of desiccant coated metal cabinet

Condensation occurring on metal cabinet surface seriously affects the maintenance and operation safety. In order to prevent condensation, desiccant coating surface method is proposed and investigated in this paper. Basic operation model of desiccant coated cabinet to realize anti-condensation and regeneration is first introduced, then an experimental setup is established to investigate and compare both anti-condensation and regeneration capacities of zinc sheet samples with and without desiccant coating. Widely adopted silica gel is adopted as desiccant material in this study. Results show that silica gel coated sample can effectively extend the anti-condensation time 2 to 6 times longer. When surface temperature is between 35 °C and 50 °C under experimental conditions, the coated desiccant material can be regenerated and recycled. The corresponding longest regeneration time is 160 min. The dynamic adsorption capacity of coated silica gel is also analyzed and it is found that both adsorption rate and mass of silica gel increases under lower surface temperature, and improvement index gradually becomes less obvious with decreasing surface temperature, the corresponding saturated adsorption mass of silica gel before condensation is about 0.3 g/g. Finally a practical case study of desiccant coated cabinet is conducted at Shanghai and operation testing shows that occurrence probability of condensation for desiccant coated cabinet greatly decreases from 70% to 10% compared with conventional cabinet in plum rain season, and there is no condensation occurring within desiccant coated cabinet in early autumn. The performance of silica gel coated cabinet is tested under relatively extreme condition with simulated high humid environment (30 °C, 90%) lasting for 7–10 h, it is found that the cabinet could continuously operate for about 60 h without condensation. In conclusion, desiccant coating method is proven to be an effective way to prevent condensation.

A parametric analysis on the regeneration performance of silica gel in a proposed comfort provision strategy for a typical office space in Harare, Zimbabwe

This paper reports the influence, design and climate parameters have on the regeneration performance of a proposed strategy for passive comfort provision for an office space. Solar regeneration of an external silica gel bed is later followed by regeneration of internal surfaces laden with silica gel. The internal surfaces regeneration is effected utilizing air dried by the external bed. External bed regenerating air conditions are evaluated based on simple energy balance and buoyancy models. Thermal efficiency is formulated based on its fundamental definition. Silica gel drying models are obtained from literature. MS Excel Spreadsheet program is applied in the present simulations. Internal surfaces regeneration depends largely on; ventilation rate, initial dryness and mass of external silica gel bed. There is an optimum ventilation rate for a given mass of silica gel in the external bed for particular initial moisture content. Channel depth is quite critical to the regeneration effect on the external silica gel bed, with an average influence coefficient of 200%. The specific humidity of the regenerating air has the least coefficient of influence of 82%. Considering the foregoing, the design of the proposed system calls for simulation to estimate performance.

Influence of the design parameters on the overall performance of a solar adsorption refrigerator

This paper describes a parametric improvement study of a solar adsorption refrigerator, using a flat plate collector with silica-gel and water as the adsorption pair. Based on a set of experimental results obtained with a prototype, used mainly for model validation purposes, a numerical study is conducted to determine the influence of the most relevant parameters and to improve the overall performance.The main parameters considered in this study are: the mass of silica-gel, the number of metallic fins in the silica-gel bed, the orientation of the solar collector (azimuth angle), the improvement of the collector's cooling during the night, the thermal contact resistance between silica-gel and the collector plate, the condenser surface area, the evaporation surface area, the radiant properties of the collector plate, and the thermal insulation of the refrigerated cabinet. The influence of each individual parameter is analyzed, and its optimum value is determined. The refrigeration system with all the individually obtained optimum parameters has an overall performance considerably higher than that corresponding to the analyzed prototype, providing useful information for a better integrated understanding of the solar adsorption refrigeration systems, and for a better design of such systems looking for their maximum overall performance.

Heat generation associated with pressure-induced infiltration in a nanoporous silica gel

As a liquid moves in the nanopores of a silica gel, because of the hysteresis of sorption behavior, significant energy dissipation can take place. Through a calometric measurement, the characteristics of associated heat generation are investigated. The temperature variation increases with the mass of silica gel, which consists of a reversible part and an irreversible part. The residual temperature change is about 30% to 60% of the maximum temperature increase and can be accumulated as multiple loading cycles are applied.

Comparative analysis of thermally activated, environmentally friendly cooling systems

This paper compares the relative performances of three different thermally activated, environmentally friendly cooling systems, e.g. a silica-gel–water adsorption system, a LiBr–H 2O absorption system and a desiccant air system. The adsorption and absorption systems in the current study employ water as the refrigerant, while the desiccant system cools atmospheric air directly. Each of these systems can be utilized at relatively low heat source temperatures such as achieved by flat plate solar collectors, but it is unclear which of these systems is best suited to what range of heat source temperature. Our study explores answers to this question by generating quantitative results comparing their relative thermal performance, i.e. COP and refrigeration capacity, and a qualitative comparison based on the size, maturity of technology, safe operation etc. In order to provide a fair comparison between the fundamentally different systems, a UA (overall heat transfer coefficient multiplied by the heat transfer area) value of 1.0 kW °C −1 is considered for the heat exchanger that transfers heat from the supplied hot water. Furthermore, to compare systems of similar size, the mass of silica-gel in the adsorption and desiccant systems and the mass of LiBr–H 2O solution in the absorption system were specified such that each system provides the same amount of refrigeration (8.0 kW) at a source temperature of 90 °C. It is found that the absorption and adsorption cooling systems have a higher refrigeration capacity at heat source temperatures below 90 °C, while the desiccant air system outperforms the others at temperatures above 90 °C.

Study on a re-heat two-stage adsorption chiller – The influence of thermal capacitance ratio, overall thermal conductance ratio and adsorbent mass on system performance

Silica gel/water based adsorption cycles have a distinct advantage in their ability to be driven by heat of near-ambient temperature so that waste heat below 100 °C can be recovered. One interesting feature of refrigeration cycles driven by waste heat is that they do not use primary energy as driving source. From this context, some researchers investigated the performance of multi-stage adsorption refrigeration cycles those can be operated by heat source of temperature 60 °C or lower which are usually purged to the environment, with a heat sink of temperature at 30 °C. However, the performances of multi-stage systems are low. To improve system performance, an analytic investigation on a re-heat two-stage chiller is performed to clarify the effect of thermal capacitance ratio of the adsorbent and inert material of sorption element, overall thermal conductance ratio of sorption element and evaporator along with silica gel mass on the chiller performance. Results show that cycle performance is strongly influenced by the sorption elements overall thermal conductance values due to their severe sensible heating and cooling requirements resulting from batched cycle operation. The effect of thermal capacitance ratio ( C s/ C m) becomes significant with relatively higher mass of silica gel. It is also found that the chiller performance increases significantly in the range of silica gel mass from 4 to 20 kg.

Calibration of the thermal desorption-gas chromatography-mass spectrometry system using standards generated in the process of thermal decomposition of chemically modified silica gel

A calibration method for the thermal desorption gas chromatographic-mass spectrometric (TD-GC-MS) determination of n-propanethiol based on a gas standard mixture generated in the process of thermal decomposition of chemically modified silica gel is proposed. The experimental results indicated that the total amount of n-propanethiol liberated from unit mass of the gel did not depend on the total mass of the gel used. A calibration curve for the TD-GC-MS system for n-propanethiol, determined for the relationship between the mass of n-propanethiol and the mass of the modified silica gel used, was found by a linear regression method and was characterized by a correlation coefficient r=0.99. This means that the amounts of liberated n-propanethiol are directly proportional to the mass of the modified gel used within the examined range of masses of silica gel samples. Consequently, the amount of the analyte (n-propanethiol) can be determined on the basis of mass of silica gel used and hence the modified silica gel can be treated as a standard of the liberated component (n-propanethiol) in this case).

Liquid-phase Adsorption from Binary Solutions on Silica Gel. Separation Factors and Orientation of Adsorbed Components on the Surface

Abstract The preferential adsorption equilibria of various binary solutions of cyclohexane-aromatic compounds and cyclohexane-cyclic ethers on chromatographic silica gel have been studied at 30°C. On the basis of the assumption that the adsorption is of the Langmuir-type, the separation factors (α) and the numbers of moles in the adsorbed-phase per unit mass of silica gel (nσ⁄m) have been calculated. The values of logα correlate well not only with the electron-donating properties of the preferentially-adsorbed components, but also with the powers of the gas-phase adsorption on silica gel and of the liquid-liquid interaction with liquid trimethylsilanol. Moreover, on the basis of the information on nσ⁄m, the orientation angles of the adsorbed components on the surface have been evaluated. The adsorption of the aromatic hydrocarbons was nearly flat to the surface, and that of the cyclic ethers, perpendicular.

Simultaneous heat and mass transfer in a fluidized bed of drying silica gel

AbstractThe determination of the partial coefficients of heat and mass transfer in air from and to a drying fluidized mass of silica gel is given. The analogy between the two methods of transport in the bed has been studied by an inspection of the relation between the two coefficients. A correlation of these coefficients with the void fraction, the superficial velocity, the particle size and the tube diameter of the bed has been derived. This correlation has been transformed into a correlation of dimensionless groups.

Aspects of the lithology of the Wessex Upper Greensand

The lithological variations shown by the Upper Greensand within the Wessex area are first considered. Glauconite, phosphate, limestone and chert, all of which characterise the series, are then discussed in turn. Five distinct types of glauconite occur, often in different sedimentary associations; the mineral has formed from a variety of source materials, but in all cases seems to have solidified from an original gelatinous state. Phosphatic nodules may form by replacement of calcareous shells, sponges or limestone concretions, and are particularly associated with depositional breaks and richly glauconitic horizons. Calcareous stone is mostly rich in detrital grains, being produced by the cementation by calcite of the surrounding sand. Nodules of pure limestone at certain horizons are thought to result from the recrystallisation of calcareous patches in the original sediment. The Upper Greensand cherts appear to have formed in fairly shallow but tranquil waters. A mass of silica gel, precipitated on the sea-floor, solidified into a nodule of porous stone which was subsequently converted into true chert by deposition of silica from solution. The arenaceous sediment was brought into the sea from a land-mass to the west.

The partial coefficient of heat transfer in a drying fluidized bed

The determination of the partial coefficient of heat transfer from air to a drying fluidized mass of silicagel is given. The data obtained can be correlated by means of the equation h = 1·31 ( R) 0·76. A comparison of the external and internal heat exchange in a fluidized mass is presented.

Temperature and humidity measurements in a drying fluidized bed

Temperature and humidity measurements of air in and above a drying fluidized mass of silica gel are given. It is proved that perpendicular to the flow of air the temperature and the humidity show no gradient ; that the temperature of the silica gel is practically equal to the temperature of the leaving air, being independent of the place in the apparatus ; that mass and heat transfer takes place in a very small layer only and finally that heat is transferred to the solid substance by the supporting sieves as well as by the air directly.