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Vacuum Pressure (vacuum + pressure)
Selected AbstractsNovel pervaporation technology using absorption refrigeration for vapor removalAICHE JOURNAL, Issue 11 2002Alaa Fahmy A novel process configuration for pervaporation and vapor permeation realizes the permeation driving force by absorbing the permeate vapor into a suitable solution with a very low vapor pressure. Although the suggested process design lacks an experimental demonstration, by using two well-established technologies,the separation by pervaporation and the absorption refrigeration,it can achieve technical and economic advantages over the conventional condensation technology. Vacuum pressures as low as 8 mbar can be obtained at ambient temperatures without refrigeration, as well as low vacuum ranges that are not possible by condensation without freezing. Process simulations and feasibility investigations for the suggested process are discussed. [source] Optimising microwave vacuum puffing for blue honeysuckle snacksINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2010Chenghai Liu Abstract Fresh blue honeysuckle fruit slices were puffed in a microwave vacuum dryer up to a final moisture content about 5% (w.b.). The effect of initial moisture content (IMC) (25,45%), vacuum pressure (VP) (70,90 kPa) and microwave intensity (MI) (10,30 W g,1) on quality attributes, in terms of expansion ratio (ER), hardness (HD), crispness (CR) and colour of the products, were analysed by response surface methodology. Besides the effect of MI on chroma (CH), the high IMC and low VP had a significantly positive impact on the quality attributes of blue honeysuckle snacks. The optimum product qualities, which were ER (1.62 times), HD (5836.31 g), CR (4.48), and CH (28.7) were obtained at an IMC of 38.42%, VP of 82.02 kPa, and MI of 22.42 W g,1. The microwave vacuum method has obvious advantages when puffing the blue honeysuckle snacks. [source] The optimization of vacuum frying to dehydrate carrot chipsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2005Liu-ping Fan Summary The effects of pretreatment and processing conditions, such as frying temperature, absolute vacuum pressure and frying time; on the properties of fried carrot chips were studied. Statistical analysis with response surface regression showed that moisture content, fat content and breaking force of carrot chips were significantly (P < 0.05) correlated with frying temperature, vacuum absolute pressure and frying time. The optimum conditions were a vacuum frying temperature of 100,110 °C, a vacuum absolute pressure of 0.010,0.020 MPa and a frying time of 15 min. [source] Influence of resin viscosity and vacuum level on mechanical performance of sandwich structures manufactured by vacuum baggingADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010A. Valenza Abstract The choice of process parameters is critical in optimizing the mechanical properties of sandwich structures produced using the vacuum bagging technique. The aim of this paper is to analyze how the viscosity of the resin/curing agent system and the vacuum level influence the morphology and the mechanical behavior of sandwich beams with composite faces (epoxy resin and glass fiber fabric named COMBI 900) and a PVC foam core. Four different sandwich structures were produced by varying the viscosity of the epoxy resin/curing agent at constant maximum vacuum pressure. Three further structures were manufactured by varying the strength of the vacuum with the resin viscosity maintained constant at the minimum level. Three point bending tests were carried out on all seven sandwiches. The analysis shows that although both parameters affect the mechanical characteristics of the structure, the viscosity of the resin system is clearly the more influential of the two. The morphological structure of the sandwiches was analyzed both by scanning electron microscope (SEM) and by muffle furnace ignition to calculate the percentage of fibers, matrices, and voids present in the different samples © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:20,30, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20172 [source] CHARACTERISTICS OF CHAMBER TEMPERATURE CHANGE DURING VACUUM COOLINGJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2009RUI ZHAO ABSTRACT In order to investigate the dynamic changing pattern of the chamber temperature with chamber pressure during vacuum cooling, 10 repeated experiments were conducted to evaluate the time-dependent temperature and pressure in the vacuum chamber during vacuum cooling of water. Water was chosen in the experiment as it is the main component of most foods. The results showed that the temperature in the vacuum chamber significantly depended on variation in pressure at different pumping stages. The temperature changes in the chamber generally followed a certain pattern. In the early stage of vacuum cooling, the chamber temperature dropped very quickly (0.26 K/s), while at the end of vacuum cooling, it increased rapidly (0.22 K/s), and was about 11.8 K higher than the ambient temperature when the vacuum was released with ambient air flowing back to the chamber. PRACTICAL APPLICATIONS Vacuum cooling is a rapid cooling method for the food industry; further understanding of the vacuum cooling mechanism can help to control and improve this cooling process. Temperature changing pattern and distribution affects the quality of the food product in vacuum cooling process. As the main component of most foods is water, it is necessary to investigate the dynamic temperature changing pattern and distribution with vacuum pressure during vacuum cooling of water so that the information obtained could be used as a reference for vacuum cooling of food products. [source] OPTIMIZATION OF VACUUM PULSE OSMOTIC DEHYDRATION OF CANTALOUPE USING RESPONSE SURFACE METHODOLOGYJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2005WILMER J. FERMIN ABSTRACT The optimum levels of vacuum pressure, concentration of osmotic solution and dehydration time for vacuum pulse osmotic dehydration of cantaloupe were determined by response surface methodology (RSM). The response surface equations ( P < 0.05 and lack of fit > 0.1) explain the 97.6, 88.0 and 97.1% of the variability in weight loss, water loss and °Brix increase, respectively, at 95% confidence level. The canonical analysis for each response indicated that the stationary point is a saddle point for weight loss and °Brix increase, and a point of maximum response for water loss. The region that best satisfied all the constraints (low values in weight loss and °Brix increase, and high value in water loss) is located within the intervals from 49.5 °Brix to 52.5 °Brix for concentration and from 75 min to 84 min for dehydration time at a vacuum pulse of 740 mbar. [source] EFFECTS OF ENZYME-AIDED PEELING ON THE QUALITY OF LOCAL MANDARIN (CITRUS RETICULATA B.) SEGMENTSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2004FANNY LIU ABSTRACT Pectinases are observed to selectively alter the albedo structure of citrus fruits and, hence, aid the removal of the peel and adhering albedo layer. This study was carried out to determine the optimum conditions needed to peel local mandarins using pectinases (Peelzym II, Novo Nordisk, Denmark). The experiment variables were enzyme concentration, vacuum pressure and vacuum infusion time. The mandarins were first scored from the stem end to the blossom end, followed by immersion in 1000 mL of enzyme solution at a set vacuum pressure and ambient temperature (27 ± 1C). Only one parameter was varied in any one experiment. Peelzym II at 0.4% v/w, 650 mm Hg vacuum and 16 min of vacuum time were optimal. The enzyme-peeled fruit segments were judged by the panelists using three different sensory tests to ascertain their appeal to consumers. A significant (P < 0.05) difference between enzyme-peeled and hand-peeled segments was found, with the panelists preferring the enzyme-peeled segments. [source] Reduction of Acrylamide Formation in Potato Chips by Low-temperature Vacuum FryingJOURNAL OF FOOD SCIENCE, Issue 8 2004C. Granda ABSTRACT: Potatoes and other foods that have a high content of the amino acid asparagine and a high accumulation of reducing sugars are subject to the formation of acrylamide upon frying. The objectives of this research were (1) to analyze the level of acrylamide formed during deep-fat frying of potato chips and (2) to evaluate means of reducing acrylamide in potato chips by using different potato cultivars and vacuum frying. Several potato cultivars were used in this research, including Innovator (I), NDTX 4930,5W (N), ATX 854 04,8W (ATw), Atlantic (A), Shepody (S), ATX847806,2Ru (ATr), and White-Rose (W). An electric bench-top (atmospheric conditions)-type fryer was used to fry the potatoes. Three temperatures were used: 150 °C, 165 °C, and 180 °C. The vacuum frying experiments were performed at 118 °C, 125 °C, and 140 °C and a vacuum pressure of 10 Torr. The potatoes were sliced (1.5-mm thick) and fried for different lengths of times. For potatoes fried at 165 °C (for 4 min) at atmospheric conditions, the acrylamide contents were 5021 ± 55 ppb (W), 552 ± 25 ppb (I), 358 ± 50 ppb (N), 397 ± 25 ppb (ATw), 646 ± 55 ppb (A), 466 ± 15 ppb(S), and 537 ± 14 ppb (ATr). Vacuum frying reduced acrylamide formation by 94%. Results showed that both cultivar and modified frying systems can play an important role in reducing acrylamide formation in fried potatoes. As the frying temperature decreased from 180 °C to 165 °C, acrylamide content in potato chips reduced by 51% during traditional frying and by 63% as the temperature decreased from 140 °C to 125 °C in vacuum frying. Increased frying time increased acrylamide formation during traditional frying for all temperatures and frying methods analyzed. However, the effect on acrylamide concentration was greater for the traditional frying than the vacuum frying. Keywords: acrylamide, vacuum, frying, potato, temperature [source] Frequency response analysis of slot coatingAICHE JOURNAL, Issue 9 2010Takeaki Tsuda Abstract Frequency responses to the slot die coating process is analyzed using empirical modal analysis to predict the effects of periodic process disturbances such as gap oscillation and variations in vacuum pressure, web velocity, and flow rate. A type of empirical modal analysis known as an experimental modal approach was used, and an oscillator basis model was assumed by using a linearized governing equation, and the coefficient of the basis model was determined by curve-fitting. By completing the process, we were able to decompose each mode, during which process it was found that the modes are of two types: a squeeze mode related to viscous characteristics and sinuous modes that are identical to capillary waves. Observation of the meniscus shapes of each mode revealed, in the third mode near the lip edge, significant fluctuations that can induce other coating defects. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Ovum Pick-up in Sheep: a Comparison between Different Aspiration Devices for Optimal Oocyte RetrievalREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2006C Rodríguez Contents In vivo ovum pick-up (OPU) in sheep may be improved with a proper choice of aspiration elements (needle and tubing) and aspiration vacuum pressure. In the present study, two experiments were carried out. In Expt 1, visible follicles in ovaries of slaughtered ewes (treated separately according to their diameters: small <3 mm, medium 3,5 mm and large >5 mm) were aspirated using different combinations of the three studied factors such as aspiration flow rate (10, 20, 30, 40 and 50 ml water/min), needle gauge (18 and 20 G) and tubing inner diameter (1, 2 or 3 mm internal diameter). In Expt 2, a study with two 18 G needles of different lengths (18 G: 82 mm; 18 GL: 600 mm) was carried out, using ovaries obtained post-mortem, and performing in vivo laparoscopic follicular aspiration on ewes. We considered good quality oocytes as those with both complete compact cumulus and a homogeneous cytoplasm. Recovery rate, proportion of good quality oocytes (good quality oocytes/100 oocytes recovered) and overall efficiency (good quality oocytes/100 follicles aspirated) were noted. In Expt 1, aspiration flow rate affect remarkable proportion of good quality oocytes (69.5%, 50.5%, 44.8%, 36.5% and 28.3% for flows from 10 to 50 ml/min respectively, p < 0.05). Needle gauge did not affect aspiration device efficiency. Thin and intermediate tubings were more effective (overall efficiency rates: 34.9%, 32.3% and 28.1% for 1, 2 and 3 mm respectively, p < 0.05). Follicle size did not affect recovery rate, but proportion of good quality oocytes was higher for large (77.9%) and medium (64.4%) follicles (p < 0.05). Finally, some combinations of the aspiration device showed greater effectiveness. In Expt 2, needle length did not influence recovery rate, but good quality oocytes rate was significantly modified both post-mortem and in vivo (good quality rate for 18 G vs 18 GL needles: 69.5% vs 47.7% and 58.1% vs 25.4%, post-mortem and in vivo respectively, p < 0.05). We conclude that low-aspiration flow rates (10 and 20 ml/min) with thin or intermediate tubings (1 and 2 mm), and any short needle (18 G or 20 G) are the most adequate aspiration factors for OPU in sheep. [source] L -Lysine Monohydrochloride Syrup Concentration using a Membrane Hybrid Process of Ultrafiltration and Vacuum Membrane DistillationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2008O. Bakhtiari Abstract The development of energy saving membrane separation processes is finding a unique position in process industries. One of the important areas where they are employed is the biotechnology industry. This industry has its own specifications and requirements, e.g., levels of diluteness, thermal, chemical and shear fragility. Membrane separation processes have the characteristics necessary to match these specifications and needs. In this research, the determination of the experimental concentration of L -Lysine monohydrochloride (L -lysine-HCl) syrup was investigated using ultrafiltration (UF) and vacuum membrane distillation (VMD) hybrid membrane processes. Four parameters that are known to have significant influence on the UF process were examined, i.e., pressure difference across the membrane, feed concentration of L -lysine-HCl, feed velocity on the membrane surface, and pH. For the VMD unit, pressure difference and pH were replaced with feed temperature and vacuum pressure on the permeate side of membrane. Each process was carried out separately and the results were used to design a bench-scale process. In order to save time and money, the Taguchi method of experimental design was employed. The effects of feed concentration, pressure difference across the membrane, feed velocity on the membrane surface, and pH on the target variable, i.e., the membrane flux, in the UF process were 39.93, 38.65, 9.36, and 9.59,%, respectively. For the VMD process, these values were 64.79, 22.16, 6.21, and 2.14,% for feed temperature, feed concentration, vacuum pressure on the permeate side, and feed velocity on the membrane surface, respectively. [source] Effects of cell structure and density on the properties of high performance polyimide foams,,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005Martha K. Williams Abstract Activity at the NASA Langley Research Center (LaRC) has focused on developing low density polyimide foam and foam structures which are made using monomeric solutions or salt solutions formed from the reaction of a dianhydride and diamine dissolved in a mixture of foaming agents and alkyl alcohol at room temperature. Monomer blends may be used to make a variety of polyimide foams with varying properties. The first foaming process developed consisted of thermal cycling the polymer precursor residuum and allowing the inflation of the particles to interact to create the foam. This process has resulted in foam structures with higher percentages of open cell content. Another innovative foaming process has been developed that begins with partially inflated microspheres, "friable balloons", with incomplete polymer molecular weight gain, which when fully cured into a foam results in more closed cell structures. In a research study performed by NASA Kennedy Space Center (KSC) and LaRC, two closely related polyimide foams, TEEK-H series and TEEK-L series, (4,4,-oxydiphthalic anhydride/3,4,-oxydianiline and 3,3,,4,4,-benzophenonetetracarboxylic acid dianhydride/4,4,-oxydianiline) were investigated for density effects and closed versus open cell effects on the thermal, mechanical, and flammability properties. Thermal conductivity data under the full range of vacuum pressures indicate that these materials are effective insulators under cryogenic conditions. Contributing factors such as cell content, density, and surface area were studied to determine the effects on thermal conductivity. Cone calorimetry data indicated decreased peak heat release rates for the closed cell system, TEEK-H friable balloons, compared to the TEEK foams with higher open cell content. Mechanical properties including tensile strength and compressive strength indicated that the materials have good structural integrity. Foams with more open cell content resulted in greater tensile and compressive strengths than the closed cell foams. The maximum closed cell content achieved in the "friable balloon" system was 78% at a foam density of 0.048 gm/cm3. Published in 2005 by John Wiley & Sons, Ltd. [source] | ||||||||||