High Barrel Research Articles

ENERGY CONSIDERATIONS ON EXTRUSION OF TARHANA, A WHEAT FLOUR BASED PRODUCT

ABSTRACT Tarhana, a traditional Turkish cereal food, was extruded using a twin‐screw extruder. The effect of the changes in barrel temperature (60–120C), feed rate (10–20 kg/h, wet basis) and screw speed (100–300 rpm) on the mechanical and thermal energy inputs was investigated. Energy balances showed that increasing barrel temperature tends to reduce the contribution of heat energy converted from the mechanical energy (ME) to the total heat energy absorbed by tarhana. The use of high‐screw speeds at relatively high barrel temperatures and at low feed rates is not suitable from an energy point of view because only a small portion of the ME introduced into the system is absorbed by tarhana. It is concluded that higher barrel temperatures, lower screw speeds and higher feed rates are more suitable for economic tarhana extrusion. PRACTICAL APPLICATIONSTraditional batch method of tarhana production is not automated with manufacturing capacities being low and highly labor extensive. Developing tarhana using extrusion cooking would allow tarhana to be produced at a lower cost because of more efficient use of energy and greater process control; production capacity would be greater, and quality control could be more easily monitored, leading to a standard product. Moreover, an easier preparation of instant tarhana soup would facilitate its usage at home for households and in school, hospital and military canteens. Investigating the energy changes during tarhana extrusion could lead to a clearer understanding of tarhana extrusion from an engineering point of view.

Effects of extrusion conditions on system parameters and physical properties of a chickpea flour-based snack

Abstract Response surface methodology (RSM) was used to study the effects of feed moisture content (16–18%), screw speed (250–320 rpm), and barrel temperature (150–170 °C) on extruder system parameters (product temperature, die pressure, motor torque, specific mechanical energy, SME) and physical properties (expansion, bulk density, hardness) of a chickpea flour-based snack. Second-order polynomials were used to model the extruder responses and product properties as a function of process variables. Product temperature and die pressure were affected by all three process variables, while motor torque and SME were only influenced by screw speed and barrel temperature. All three variables affected product responses significantly. Desirable products, characterized by high expansion ratio and low bulk density and hardness, were obtained at low feed moisture, high screw speed and medium to high barrel temperature. It was demonstrated that chickpeas can be used to produce nutritious snacks with desirable expansion and texture properties.

Optimization of Extrusion Process Variables Using a Genetic Algorithm

Optimization of process variables during single screw extrusion cooking of a fish and rice flour blend was carried out using a genetic algorithm (GA). Second-degree regression equations were developed for the extrudate properties such as expansion ratio (ER), bulk density (BD), hardness (H) and water solubility index (WSI) in terms of the independent variables: barrel temperature (°C), screw speed (rpm), fish content (%) and feed moisture content (%). These equations were used as the objective function to find the optimum process conditions separately for each (individual) and commonly for all (common) extrudate properties. The regression equations of ER and WSI were maximized and BD and H were minimized for both types of optimum process conditions. A maximum population of 100, and 100 iterations, was sufficient for successful convergence. A high barrel temperature, of about 200°C, and screw speed of 110 rpm were identified as both individual and common optimum process conditions for all the extrudate properties except for WSI. Fish content and feed moisture content were identified as two interacting process variables. Under individual optimum process conditions, maximum ER and minimum hardness required a low fish content of 5% (w/w) and feed moisture contents of 60 and 40%, respectively, and minimum BD and maximum WSI required high fish content of 41–45% and medium moisture content of about 40%, respectively. However under common optimum process conditions all four extrudate properties were optimized at a high fish content of 41–45% and medium moisture content of 40%. The experimental extrudate properties matched the values predicted for ‘common optimum’ conditions more closely than those for individual optimum process conditions.

Effects of extrusion variables on the properties of waxy hulless barley extrudates.

The objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory-scale corotating twin-screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170 degrees C) to develop a snack food with high beta-glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and beta-glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although beta-glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower beta-glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high beta-glucan content, especially using LS conditions.

Investigation of Melting Phenomena in Modular Co-rotating Twin Screw Extrusion

Abstract An experimental investigation of the mechanisms of melting of polyolefins in a modular co-rotating twin screw extruder was carried out as a function of (i) barrel temperature including below the melting temperature (ii) screw speed and (iii) feed rate. The modular screws were removed from a twin screw extruder following experiments where pellets of linear low density polyethylene or isotactic polypropylene had been fed and processed under steady state conditions. The modular screws contained thermoplastic carcasses. These were sectioned and removed as well as inspected. Three melting initiation regimes were identified. These were (i) melting initiated from barrel, (ii) melting initiated from screw, and (iii) melting initiated in the bulk. At high barrel temperatures mechanism (i) is observed, at lower barrel temperatures and slower screw speeds mechanism (ii) is found, and at lower barrel temperatures and higher screw speeds mechanism (iii) is observed. The propagation of the melting process was also investigated. Pellet bed instabilities are usually involved at higher screw speeds. We discuss modeling of these mechanisms.

Effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber in capillary die flow

AbstractThe effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber compounds in an extrusion capillary rheometer were investigated. Either the barrel diameter or the die diameter was altered so that different barrel‐diameter/die‐diameter (DB/DD) ratios were obtained, both the barrel and die diameters also being varied simultaneously. The extrudate swell and entrance pressure drop were dependent not only on DB/DD but also on the actual diameters used. For fixed DB/DD ratios, the change in the extrudate swell was linearly influenced by the entrance pressure drop at low actual barrel and die diameters (DB/DD = 20/4–30/7 mm/mm) but was associated with a change in the material viscosity at high barrel and die diameters (DB/DD = 35/7–40/8 mm/mm). When the die diameter was fixed, the relationship between the entrance pressure drop and the extrudate swell was linear up to a certain value of the barrel diameter greater than 30 mm. Beyond this critical barrel value, the relationship became nonlinear and associated with the shearing stress generated by the formation of semipluglike flow patterns and the residence time of the material. For a constant barrel diameter, the smaller the die diameter was, the greater the extrudate swell was because of the increases in the extensional deformation and wall shear rate coupled with a reduction in the material residence time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1762–1772, 2002

Bulk Polymerization of ε-Caprolactone in an Internal Mixer and in a Twin Screw Extruder

Abstract Bulk polymerization of ε-caprolactone has been carried out both in a laboratory internal mixer (Brabender Plasticorder) and in a modular intermeshing co-rotating twin screw extruder. Various initiators, such as titanium n-butoxide, aluminum triisopropoxide, and sodium hydride were used to polymerize ε-caprolactone in an internal mixer. The continuous polymerization of ε-caprolactone was performed using aluminum triisopropoxide under a range of processing conditions, including barrel temperature profiles, throughput, and screw speed. This polymerization was investigated for various ratios of monomer to initiator. GPC analysis demonstrated that significant quantities of oligomers were produced together with high molecular weight polymer at different reaction temperatures. H NMR detected the hydroxylation of growing chain end group for bulk polymerization at high barrel temperature. The molecular weight was reduced along the screw axis once the maximum molecular weight was obtained after the first kneading disk block. Increasing screw speed caused further reductions in molecular weight.

Effects of selected process parameters in extrusion of yam flour (Dioscorea rotundata) on physicochemical properties of the extrudates.

Raw yam (Dioscorea rotundata) flour was cooked and extruded in a Brabender single-screw laboratory scale extruder. Response surface methodology using an incomplete factorial design was applied with various combinations of barrel temperature [100, 125, 150 degrees C], feed moisture content [18, 22, 26%] and screw speed [100, 150, 200 rpm]. Initial viscosity at 30 degrees C, water solubility index, expansion and hardness were determined. The highest values of initial viscosity were at the highest barrel temperatures and the highest moisture contents. At high feed moisture content and high barrel temperatures the yam extrudate flour showed the greatest values of water solubility index. The physical properties of the extruded product showed that at high temperature the lower the moisture content the greater the expansion index. Hardness was influenced directly by moisture content and inversely by extrusion temperature. The extrusion of yam flour led to the production of snacks and pre-gelatinized flours of diverse properties. Also extruded yam flour can be successfully used in the preparation of 'futu' (pre-cooked compact dough), a yam-based food, popular in Western Africa.

Influence of extrusion variables on the proteinin vitro digestibility and protein solubility of extruded soy tarhana

Tarhana, supplemented with 150 g kg−1 full-fat soy flour, was extruded at different extrusion conditions (barrel temperature: 80–120°C; screw speed: 100–300 rpm; feed rate: 10–20 kg h−1 ) using a twin-screw extruder. The effect of extrusion conditions on the in vitro digestibility (PD) of the protein and protein solubility (PS) was investigated using response surface methodology. Regression equations for predicting PD and PS were developed. While the barrel temperature had a significant effect on PD (P <0.1), feed rate was the most significant variable on PS of the samples (P<0.05). Since the protein solubility should be high for the instant properties of extruded soy tarhana soup, it is suggested that soy tarhana should be extruded at low feed rates (ie high residence times) while high barrel temperatures should be achieved for the inactivation of antinutritional factors present in the soy flour. © 1999 Society of Chemical Industry

Extrusion Cooking of Rice Flour and Amaranth Blends

Response surface methodology was used to investigate the extrusion cooking and product properties of rice flour and amaranth blends in a CM45-F conical, counter-rotating twin-screw extruder. Three mixtures at a level of 20, 40 and 60 g/100 g amaranth were extrusion cooked using a central composite design with varied barrel temperature (150-190 °C), feed moisture (11-16 g/100 g wb), feed rate (15-35 kg/h), and screw speed (58-82 rpm). Pressure, torque, specific mechanical energy (SME), Brabender pasting properties, expansion of extrudate characterised by sectional (SEI) and longitudinal expansion (LEI), product density, breaking strength, and total colour change were determined. Increasing amaranth content in the blends increased die pressure, but decreased torque and SME. Increasing amaranth content caused an enormous decrease in the sectional expansion index (SEI) and increase in the breaking strength of extrudate. Well expanded rice-amaranth products with acceptable soft texture were at amaranth levels of 20-40 g/100 g. Optimal extrusion cooking conditions most likely to produce rice-amaranth products suitable for a puffed snack food were at high barrel temperature, low moisture, high screw speed, and feed rates in the range of 25-35 kg/h.

Tensile properties of injection molded Mg&amp;ndash;Al based alloys

The relationship between the process parameters and the mechanical properties of injection molded magnesium alloys based on Mg-Al system (AZ91D, AM60B, AM50A and AS41B) is investigated. It is shown that the tensile properties of injection molded specimens are superior to those of die casting. A high barrel temperature reduces solid fraction and improves tensile properties of injection molded magnesium alloys. These properties tend to saturate above the liquid temperature.

Twin-screw extrusion of rice-green gram blend: Extrusion and extrudate characteristics

A rice and green gram ( Vigna radiata L.) blend (1:1, dry basis) was extruded using a co-rotating twin-screw extruder with a barrel diameter of 31 mm. The effects of barrel temperature (100–175 °C) and screw speed (100–400 rpm) on the extrusion system parameters (torque and specific mechanical energy) and extrudate characteristics (expansion ratio, density and maximum shear stress) were studied. The response functions (torque, specific mechanical energy, expansion ratio, extrudate density and maximum shear stress) were related ( r ≥ 0·870, p ≤ 0·01) to the process variables (screw speed and temperature) by second-order polynomials. The torque during extrusion was highest at the highest temperature levels. The specific mechanical energy linearly increased with screw speed. The maximum breaking (shear) stress of the product was highly sensitive to the levels of the extrusion variables and varied up to 25-fold. Temperature and screw speed also imparted curvilinear effects on the extrusion and extrudate characteristics. High barrel temperature combined with a low screw speed is suitable for obtaining an expanded product.

Extrusion of tarhana: effect of operating variables on starch gelatinization

Tarhana, a traditional Turkish cereal food, was extruded using a twin-screw extruder. The effect of barrel temperature (6–120 °C), feed rate (10–20 kg h −1, wet basis) and screw speed (100–300 rpm) on starch gelatinization was investigated using response surface methodology at constant moisture content (43%, wet basis). A regression equation for predicting starch gelatinization was developed. Barrel temperature had the most pronounced effect on starch gelatinization at constant moisture content, followed by feed rate and screw speed. Response surface plots suggest that a high degree of starch gelatinization can be achieved when tarhana is extruded at high barrel temperatures and screw speeds but low feed rates (i.e. high residence times).

A maintainable large bore, high performance railgun barrel

This paper reviews the design features and performance characteristics for a large bore (90 mm) barrel system fabricated for the Defence Research Agency (DRA) to operate at the Kirkcudbright Electromagnetic Launch Facility. This 90 mm barrel was designed for testing developmental launch package designs. The barrel design permits the rapid refurbishment of bore insulators and rails that are commonly damaged by launch package failures during development testing. The barrel system is designed for operation with both plasma and metal armatures up to peak current levels of 3.5 MA. The results of initial performance testing including inductance gradient and bore deflection are presented. >

金属粉末射出成形プロセスにおける成形条件の最適化

In the metal injection molding process, fluidity of the compound with metal powder and binder is very important factor for molding without defects. In this paper, the effects of molding condisions (injection temperature and rate) on the moldability and the mechanical properties of compacts have been investigated by means of flow test and tensile test. The compound consisted of a carbonyl iron powder and a multi-component wax-polymer binder. Two different types of the binder were used for this study, one was APP-binder (consisted of 20% Atactic polypropylene) and the other was IPP-binder (20% Isotactic polypropylene). The results were summarized as follows:1) The compound with APP-binder gave the good moldability, because its fluidity showed gradual change in the relation between temperature and viscosity.2) When the low injection rate was adopted at low barrel temperature which the compound showed high viscosity, flowmark type of the defect appeared on the surface of green compacts. On the other hand, when the high injection rate was adopted at high barrel temperature which the compound showed low viscosity, segregation of the binder was observed in the green compacts. Such molding conditions were detrimental to the mechanical properties of sintered compacts.3) The combination process with thermal and solvent debinding produced a shortening the binder removal time and preventing the distortion.

Temperature and Velocity Profiles in Drag Flow of a Temperature Dependent Power Law Fluid

Abstract This paper analyzes non-isothermal drag flow between parallel plates. First, non-isothermal drag flow is considered of a Newtonian fluid with a non-zero pressure gradient, assuming viscous dissipation is negligible. Second, non-isothermal drag flow is considered of a power law fluid with zero pressure gradient, again assuming viscous dissipation is negligible. Finally, pure drag flow of a temperature dependent power law fluid is analyzed, including the effect of viscous dissipation. When the temperature of the stationary plate is increased, the flow rate increases. Applying this analysis to screw extrusion, this means that increasing the screw temperature relative to the barrel temperature will increase the flow rate. Also, the temperature sensitivity of the flow rate reduces with increasing screw temperature and with increasing power law index. This points to useful benefits of screw heating. With shear thinning fluids increased channel depth raises the stock temperatures, even though the shear rates in the fluid will be reduced. The increased temperatures are due to longer heat transfer distances; the viscous heat generated is less easily conducted away to the walls. At high values of the Brinkman number, the heat flux at the lower plate reduces when the upper plate temperature increases, while at low Brinkman numbers the opposite is true. This is important in the analysis of melting in extruders. It indicates that while high barrel temperatures in the melting zone may be beneficial at low screw speeds, it can be detrimental at high screw speeds. At high screw speeds, therefore, lower barrel temperatures may be more appropriate to obtain efficient melting.

The Romanesque Elevations of Tewkesbury and Pershore

The later medieval remodeling of the stylistically related abbey churches of Tewkesbury and Pershore has presented the architectural historian with the problem of ascertaining the nature of the original Romanesque design. One school of thought favors a four-story elevation for choir and transepts which would have entailed a wood roof; the other, while not agreeing on the number of stories, suggests the reconstruction of high barrel vaults. Detailed analysis of both fabrics in the context of West Country architecture after the Conquest and select French Romanesque structures will demonstrate the original existence of a three-story scheme with barrel vaults over the main spans.

Processing–mechanical property relationships in injection moldings of polybutylene

AbstractTwo unfilled nonpigmented extrusion grades of polybutylene have been injection‐molded into a tensile bar mold under a wide range of barrel and mold temperatures. The overall structure of the moldings has been determined and correlated with processing conditions. The short term tensile mechanical properties of the moldings have been ascertained and correlated with molding structure. For low mold temperatures, the Young's modulus and tensile strength of injection moldings of polybutylene are controlled by the extent of and structure within the highly oriented skin. Low barrel temperatures can give rise to highly crystalline thick skins that treble the Young's modulus and fracture stress, when compared to high barrel temperature moldings. Increasing the mold temperature introduces a brittle response in polybutylene injection moldings. Modulus is controlled, at the high mold temperatures, by the skin thickness and by the crystallinity of the material comprising the core of the molding.

Optimisation of process variables in extrusion texturing of soya

A Brabender laboratory-scale extruder was used together with response surface methodology to study the effect of processing variables on the quality of textured soya protein (TSP). Variables examined were: barrel temperature in two zones; die temperature and exit diameter; screw compression ratio and speed; and feed moisture; each at five levels. Six different assessments of the resultant TSP were made, including expansion ratio and texture quality after retorting, using an Instron with an Ottawa Texture Measuring Cell. This provided the best numerical scale of texture quality and correlated well with sensory assessment. Detailed results are presented as contour maps showing regions of optimum processing conditions. High screw compression ratio, high barrel temperature and low die temperature favoured good texture. The effect of maximum temperature drop between barrel and die was particularly striking. Optimum expansion occurred under different conditions, potentially enabling a wide range of expansion to be achieved for similar texture performance. Texture quality was reduced at extremes of small or large die exit diameter but the effects of screw speed and feed moisture were much more complex. Understanding these subtle interactions provided a means of ‘fine tuning’ to improve texture and/or expansion whilst running.

A precision high vacuum target barrel

Abstract A precision high vacuum target barrel has been constructed to be used in the 85 cm carbon free scattering chamber system. The design of this target barrel features the use of a Saginaw ball screw and Thompson linear bearings to achieve accurate positioning of targets in the chamber. The design and operation of the barrel are presented.