Feed Moisture Content Research Articles

'The effect of inulin addition on structural and textural properties of extruded products under several extrusion conditions': The effect of inulin addition on structural and textural properties of rice flour extrudates.

The growing consumer demand for healthy snacks has turned the interest of industry and research in the development of new ready-to-eat products, enriched with dietary fibers. Inulin is a soluble fiber with a neutral taste that promotes the good function of the intestine. Rice flour extrudates were produced under various extrusion temperatures, screw speeds, feed moisture concentrations and inulin replacement levels. The objective of this study was to investigate the effect of the material characteristics and the extrusion conditions on the structural and textural properties of the extrudates. Simple mathematical models were used for properties correlation with process conditions and through regression analysis it was revealed that there is a significant effect of extrusion temperature, screw speed, feed moisture content and inulin concentration on the final properties. Both density and maximum stress increased when moisture content and inulin concentration increased, while they decreased when extrusion temperature and screw speed increased. These results were also strengthened by scanning electron microscopy. The highest expansion ratio was presented when decreasing all process conditions apart from screw speed.

Physical properties of extruded snacks enriched with soybean and moringa leaf powder

This study was conducted to investigate the application of extrusion cooking in the production of snacks containing soybean (SB) and Moringa oleifera (MO) leaves as inexpensive sources of micronutrients. The specific objectives were to examine effects of barrel temperature, residence time and moisture content of feed on selected physical properties of extruded snacks (extrudates), namely water absorption index (WAI), water solubility index (WSI) and expansion ratio (ER). The extrudates were obtained by blending different levels of input ingredients of maize flour (MF) (55 to 80%), full fat soybean flour (FFSF) (10 to 30%), and Moringa oleifera leaf powder (MOLP) (5 to 15%). Extrusion process variables in a twin-screw extruder were at three levels for temperature (100, 130 and 160°C), feed moisture content (15, 22.5 and 30%), and residence time (60, 75 and 90 s). The performed study revealed that the level of incorporation of both FFSF and MOLP, and feed moisture content have significant effects on the expansion ratio, water solubility index and water absorption index of the extrudates. It was concluded that the role of processing conditions and blending levels have a significant contribution to the quality characteristics of the soy-moringa expanded snacks.

The effect of extrusion conditions on the functional properties of defatted cake of sunflower-maize based expanded snacks

The effect of extrusion conditions, including feed moisture content (14–20%), screw speed (300–500 rpm), and barrel temperature (120–180oC) on the functional properties (water absorption index (WAI), and water solubility index (WSI), fat absorption capacity (FAC) and foaming capacity) and sensory properties (color, appearance, flavor, overall acceptability and textural characteristics) of an expanded sunflower snack was investigated. Extruded snacks were prepared by substituting maize flour with developed texturized flour of sunflower at 0–40% levels. Protein content increased to 13.83% in snacks prepared with 10% texturized sunflower meal as compared to the control i.e., 7.55%. Fibre content increased while protein digestibility improved with increased level of incorporation of texturized defatted sunflower flour in extruded snacks making. Increasing feed moisture content results in extrudates with lower expansion, lower WAI, higher WSI, higher hardness and lower sensory acceptability. Increasing screw speed caused slight reduction of density and hardness of sunflower extrudate. Feed moisture had positive while screw speed and barrel temperature had negative influence on WAI. Negative coefficient of linear terms of moisture and screw speed indicated that WSI decreased with increase in these variables. Higher moisture content in extrusion process could diminish protein denaturation which lowered WSI values.

The Effect of Feed Moisture and Barrel Temperature on the Essential Amino Acids Profile of Sorghum Malt and Bambara Groundnut Based Extrudates

Malnutrition is prevalent and serious problem in Africa especially where most people are ravaged and displaced by war especially in northern Nigeria by the activities of the terrorists Boko Haram. Sorghum malt and bambara groundnut flour were processed to produce an extruded product using a twin screw co-rotating intermeshed extruder. The formulations were extruded at 100°C, 120°C and 130°C and feed moisture contents of 20%, 25% and 30% respectively. This work has therefore attempted to investigate the effect of feed moisture and barrel temperature on the retention of essential amino acids in the extrudates. Extrusion was used to obtain best extrusion conditions to develop a protein-enriched extruded product with desirable physio-chemical and sensory properties. The results showed different physical and chemical properties of the extrudates compared to those of the raw materials used. The extrusion of Sorghum malt and Bambara groundnut blend gave a good complement in terms of the essential amino acids but was faced with the challenge of depletion of the amino acids resulting from maillard reaction probably. Extrusion of foods in the presence of reducing sugars has been found to have negative effect on the quality and quantity of the essential amino acids due to maillard reaction. The results showed that the mean observed values for lysine ranged from 3.62 g/100 g to 4.51 g/100 g, while methionine has the values from 1.47 g/100 g to 2.68 g/100 g. The values for reducing sugars ranged from 222.16 mg/100 g to 453.51 mg/100 g in glucose to 680.70 mg/100 g to 835.70 mg/100 g in maltose. ANOVA was adapted for the statistical analyses. The values showed significant difference at p ≥ 0.01. The values decreased with increased barrel temperature, while increase in feed moisture increased the reducing sugar and essential amino acid contents. The essential amino acid content of the extrudates met the FAO/WHO (1973) recommended pattern for supplementary foods. This is the first attempt to produce protein enriched sorghum malt and bambara groundnut extruded product with millet and beans that can be included in a child’s meal as a breakfast cereal or a snack to fight protein malnutrition.

Optimization of Extrusion Process Parameters for Red Lentil-carrot Pomace Incorporated Ready-to-eat Expanded Product Using Response Surface

For optimization of extrusion process for development of red lentil-carrot pomace incorporated ready- to-eat rice based expanded product, experiments were planned in Box-Behnken design using response surface methodology. The independent process variables for extrusion were feed moisture content (14-20%), die temperature (120-180℃), screw speed (300-500 rpm) and formulation (rice flour: pulse flour; 60-80%: 10-30%) with constant proportion of carrot pomace powder (10%). Second order polynomials were used to model the extruder responses, functional and physical properties as a function of extrusion process variables. The extrusion process was optimized for maximum expansion ratio, water absorption index, overall acceptability and minimum bulk density, water solubility index, specific mechanical energy and hardness with in experimental range. The optimum extrusion process conditions obtained were 80:10:10 (rice flour: pulse flour: carrot pomace powder), 14% feed moisture content, 394 rpm screw speed and 120℃ die temperature. An analysis of variance (ANOVA) revealed that among the process variables, feed moisture content followed by screw speed had the most significant effect on all the responses; screw speed had the significantly higher effect on specific mechanical energy. The proportion of red lentil and carrot pomace in rice based expanded product was observed to have significantly lower effect on the selected responses.

Thermo‐mechanical extrusion and sodium hydroxide pretreatments for ethanol production from destarched corn fiber

The effect of thermo‐mechanical extrusion and sodium hydroxide pretreatments on ethanol production from destarched corn fiber (DCF) was investigated. DCF was extruded at screw speed of 300 rpm, feed moisture content of 30%, and melt temperature of 140°C and then pretreated by 0.75, 1.50, 2.25, and 3.00% of sodium hydroxide solution in the autoclave at 121°C for 1 h. After sodium hydroxide pretreatment, the liquid and solid fractions were separated by centrifugation. The dry solid fraction was used for the determination of composition, characterization (crystallinity index, microstructure, degree of polymerization), enzymatic saccharification and fermentation process. Extruded DCF pretreated by 0.75% sodium hydroxide significantly decreased lignin content, crystallinity index and degree of polymerization for efficient enzymatic saccharification and gave significant increase in ethanol yield (35.13 g L−1). Therefore, thermo‐mechanical extrusion followed by 0.75% of sodium hydroxide pretreatment was a good pretreatment for ethanol production from DCF. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 823–831, 2015

Investigation of functional properties and color changes of corn extrudates enriched with broccoli or olive paste.

Following the tendency of replacing common food snacks with healthier food products, extruded snacks with corn flour and broccoli (4-10%) or olive paste (4-8%) were investigated in this study. The effect of material characteristics, including feed moisture content (14-19%), and broccoli or olive paste concentration, and extrusion conditions, including screw speed (150-250 r/min), and extrusion temperature (140-180 ℃), on the functional properties (water absorption index, water solubility index, and oil absorption index), as well as color change (ΔE) of the extruded snacks was studied. Regression analysis showed that screw speed did not significantly influence (p > 0.05) the properties. After mathematical modelling it was found that broccoli and olive paste concentration, as well as temperature increment, caused a decrease in water absorption index (minimum of 5.6 and 6.4 g/g sample, respectively) and an increase in water solubility index (maximum of 18.7 and 10.9 g/100 g sample, respectively), while feed moisture presented opposite tendency. Higher extrusion temperature led to an increment of oil absorption index (approximately to 1.2 and 1 mL/g sample) and decrement of color changes. Finally, feed moisture and broccoli concentration lowered oil absorption index and color of corn/broccoli extrudates, while olive paste concentration caused their increment.

Production and Quality Evaluation of Noodles From Sweet Potato Starch

The effect of extrusion parameters (feed moisture content, barrel temperature, and screw speed) on the quality of noodles produced from sweet potato starch was investigated. Starch was extracted from the tuber of sweet potato and processed into noodles using single screw cooking extruder. The moisture, protein, and ash contents of the noodles decreased linearly with the feed moisture content and barrel temperature but decreased with increasing screw speed. Increased feed moisture content also led to decrease in water absorption capacity, cooking time, and water solubility index. Lateral expansion increased with increasing barrel temperature. Barrel temperature had significant effect (p < 0.05) on lateral expansion while screw speed and feed moisture content had significant effect (p < 0.05) on cooking time. Significant (p < 0.05) positive correlation was obtained between the overall sensory acceptability, appearance, firmness, and chewiness. The study showed that noodles of desirable functional qualities and sensory acceptability can be obtained from sweet potato starch using barrel temperature of 110°C, screw speed of 100 rpm, and feed moisture content of 47.5%.

English

There is increase in the use of cocoyam tubers for flour production which can be use for food and industrial purposes in Nigeria. Cocoyam (Xanthosoma sagittifolium) flour was cooked and extruded in a single screw extruder. A second order central composite response surface design was used in designing the experiment which generated 20 runs on selected process parameters including feed moisture (22, 24 and 26%), screw speed (60, 70 and 80rpm) and barrel temperature (200, 220 and 240&deg;C) on the functional and physical properties (density, expansion, water absorption index (WAI), water solubility index (WSI) and hardness) of the extrudates. Furthermore, the nutritional compositions of the snacks were also determined. Increase in feed moisture content results in higher density, lower expansion, higher WAI, lower WSI and higher hardness in the extrudates while increase in barrel temperature decreases the density, WAI and hardness but led to increase in expansion and WSI in the extrudates. The nutrient value for the extruded snacks were protein (3.76%), fibre (6.41%), carbohydrate (79.50%), energy (343.03 kj/100 g), Ca (238.50 mg/100 g), Mg (113.71 mg/100 g), K (283.77 mg/100 g), Na (97.66 mg/100 g), P(161.23 mg/100 g), vitamin C (1.03 mg/100 g) and niacin (0.78 mg/100 g). This study has established that a nutritious and acceptable snack can be produced from cocoyam flour using extrusion cooking. &nbsp; Key words: Cocoyam flour, single screw extrusion, functional, physical properties, nutritional composition.

Influence of a High-Pressure Comminution Technology on Concentrate Yields in Copper Ore Flotation Processes

Abstract The article concerns the issues of flotation process effectiveness in relationship to the operating conditions of a high-pressure comminution process course. Experimental programme covering a flotation laboratory batch tests was a verification technique of a high-pressure crushing operations course. The most favorable values of flotation concentrate weight recoveries were obtained for the pressing force 6 kN and 4% of the feed moisture. It was also determined the model of the concentrate weight recovery as a function of pressing force in the press and feed moisture content. This model was the basis for the optimization of effects of copper ore flotation processes preceded in high-pressure crushing operation in roller presses.

Canola meal moisture-resistant fuel pellets: Study on the effects of process variables and additives on the pellet quality and compression characteristics

This study focuses on pelletization of waste canola meal biomass to increase the bulk density, thereby reducing the transportation and storage costs, thus provide better material feeding in gasification reactors with less dust formation. The effects of feed constituents of canola meal such as protein, fiber, fat, lignin and feed moisture content as well as added binder, lubricant and densification process parameters on the strength and durability of the densified product are investigated. The increased durability (99%) of canola meal pellets was a result of added binder (5wt%) and the inherent protein (40wt%) and lignin (12wt%) content in the feed. From the compression data at different temperature and pressure, Kawakita and Lüdde model (1971) was developed to classify the feed material into groups. The R2 value ≥0.999 showed good model fit. It was found that at temperature >70°C, the particle undergoes rearrangement followed by fragmentation and particle plastic deformation during the compression process. The effects of coating agent on pellet durability, hardness and moisture uptake were studied to produce moisture-resistant pellets. Finally, the pellets were gasified in a fixed bed reactor using different gasifying agents such as steam, oxygen (O2) and carbon dioxide (CO2) and their effects were assessed. Carbon dioxide was found to give maximum carbon efficiency (CE) up to 82.7% and 50.7MJ/m3 LHV of gas at a temperature of 750°C and equivalence ratio (ER) of 0.4., whereas O2 gave 66.5% of CE with 44.7MJ/m3 LHV of gas at 650°C and 0.4 ER and steam produced gas with LHV 40.8MJ/m3 with CE 27.4% at 650°C and 0.2 ER. Thus, by producing moisture-resistant canola meal pellets with reasonable fuel characteristics, pelletization of canola meal provides a promising alternative for the utilization of canola meal waste as an alternative source of renewable energy.

Antioxidant potential and quality characteristics of vegetable-enriched corn-based extruded snacks.

Phenolic content, antioxidant activity and sensory characteristics of vegetable-enriched extrudates were investigated as a result of extrusion conditions, including extrusion temperature (140-180°C), screw rotation speed (150-250rpm) and feed moisture content (14-19% w.b.). Broccoli flour and olive paste was used in mixtures with corn flour at a ratio of 4 to 10% (broccoli/corn) and 4 to 8% (olive paste/corn). A simple power model was developed for the prediction of phenolic content and antioxidant activity of extrudates by extrusion conditions and feed composition. Phenolic content and antioxidant activity of broccoli enriched extrudates increased with extrusion temperature and broccoli addition and decreased with feed moisture content. The antioxidant activity of olive paste extrudates increased with material ratio and decreased with feed moisture content and screw rotation. Sensory porosity, homogenous structure, crispness, cohesiveness and melting decreased with feed moisture content, while the latter increased the mealy flavor and hardness of extrudates. Acceptable snacks containing broccoli flour or olive paste can be produced by selecting the appropriate process conditions.

A Fuzzy Inference System (FIS) and Dimensional Analysis for Predicting Energy Consumption and Mean Residence Time in a Twin-Screw Extruder

Modeling the extrusion process is complex because of the many confounding variables and the dynamic properties of the materials subjected to heat, shear and pressure. Efforts have been made to predict various system and product properties using a flow-modeling phenomenological approach. However, because of the many assumptions and the complexities involved, these models become often impractical for application. In this study, dimensional analysis was used to determine significant dimensionless parameters for the inputs and outputs of a model constrained only by the available experimental data. Thereafter, a rule-based FIS was used, instead of a conventional exponential model, for the prediction of output dimensionless parameters. Optimization or selection of subtractive cluster radii for FIS was achieved using a genetic algorithm. Data were obtained from 4 × 3 × 3 × 2 experimental design (16, 20, 24 and 28% moisture contents; 80, 120 and 160 rpm screw speeds; 3, 4 and 5 mm nozzle diameters and 120 and 140C barrel temperatures) and 3 × 2 (80, 120 and 160 rpm screw speeds; 120 and 140C barrel temperatures for a 4 mm nozzle diameter and 26% moisture content). These factorial design experiments were conducted using a laboratory twin-screw extruder. After training, the FIS captured the process trend based on the experimental data. Correlation coefficient (r2) values were found higher than those obtained from a linear regression model. Practical Applications Extrusion process is widely used to produce human foods, dog foods and polymers. Prediction of extrusion performance and scale-up of the process are very challenging because of complex and dynamic characteristics of biological materials when shear and heat are applied simultaneously. This study presents a novel modeling method to predict dimensionless parameters involving MRT and torque experienced by the extruder. The model was validated with data collected from extrusion of corn starch. This model can be used by producers to predict change in energy consumption and MRT and facilitate scale-up when feed moisture content, die diameter, screw speed and barrel temperature are changed. The modeling methodology can be further expanded to predict other extrusion performance parameters and for other materials by training and validating the model with new data set.

Extrusion 제조 조건에 따른 쌀 스낵 제품의 이화학적 품질특성

Physicochemical properties of rice-based expanded snacks extruded with rice flour, high amylose starch, and isolated soy protein were investigated using a twin-screw extruder. The ingredients were extruded at various feed moisture contents (19~23%) and screw speeds (200~400 rpm) at a constant feed rate (43.4 kg/hr). Bulk density and apparent density of rice snacks were 0.06~0.21, and 0.55~0.65 respectively. Bulk density, apparent density, water absorption index, and breaking strength of rice snacks increased with increasing feed moisture content and decreas- ing screw speed. However, expansion and water solubility index of rice snacks increased with decreasing feed moisture content and increasing screw speed. Hunter's color L values of rice snacks was lower with increasing screw speed at feed moisture contents of 19% and 21%, but was not significantly different from a feed moisture content of 23%. On the other hand, a and b values of rice snacks were higher with increasing screw speed a feed moisture content of 19%. X-ray diffraction intensity of rice snacks decreased with decreasing feed moisture content and increasing screw speed. X-ray diffraction of rice snacks was V-type at feed moisture contents of 19% and 21% and screw speeds of 300, and 400 rpm. In the microstructure of the cross section of rice snacks, air cells in rice snacks were not well formed, and cell walls were thicker with increasing feed moisture content and decreasing screw speed.

Development of flaxseed fortified rice - corn flour blend based extruded product by response surface methodology.

Flaxseed imparted the evidence of health benefits in human being. Response surface methodology (RSM) was employed to develop flaxseed fortified rice - corn flour blend based extruded product using twin screw extruder. The effect of roasted flaxseed flour (RFF) fortification (15-25%), moisture content of feed (12-16%, wb), extruder barrel temperature (120-140°C) and screw speed (300-330 RPM) on expansion ratio (ER), breaking strength (BS), bulk density (BD) and overall acceptability (OAA) score of extrudates were investigated using central composite rotatable design (CCRD). Increased RFF level decreased the ER and OAA score significantly while increased BS and BD of extrudates (p < 0.01). Moisture content of extruder feed was positively related to ER (p < 0.01) and OAA (p < 0.05) and negatively related to BD (p < 0.01). Extruder barrel temperature was found to be negatively related to ER and OAA (p < 0.05) and positively related to BD (p < 0.1). Quadratic effect of screw speed was significantly positively related to ER (p < 0.01), BS (p < 0.05) and negatively related to BD (p < 0.01). 15% RFF fortification with rice flour, 16% moisture content (wb) of extruder feed, 120°C extruder barrel temperature and 330 RPM of screw speed gave an optimized product of high desirability with corresponding responses as 3.08 ER, 0.53kgf BS, 0.106g.cm(-3) BD and 7.86 OAA.

Optimization of barrel temperature and kidney bean flour percentage based on various physical properties of extruded snacks.

The aim of the experiment was to optimize barrel temperature (122 to 178 ± 0.5°C) and red kidney bean flour percentage (KBF) (12 to 68 ± 0.5%) based on physical properties of extrudates like flash off percentage, water absorption index (WAI), water solubility index (WSI), bulk density (BD), radial expansion ratio (RER) and overall acceptability (OAA) using single screw extruder. The study was carried out by central composite rotatable design (CCRD) using Response surface methodology (RSM) and moisture content of feed was kept as constant 16.0 ± 0.5% throughout experiments. Mathematical models for various responses were found to fit significantly (P < 0.05) for prediction. Optimization of experimental conditions was carried out using numerical optimization technique and the optimum barrel temperature and kidney bean flour percentage were 120°C (T1) & 142.62°C (T2 = T3) and 20% respectively with desirability value of 0.909. Experiments were carried out using predicted values and verified using t-test and coefficient of variation percentage. Extruded snack prepared with rice flour (80%) and kidney bean flour (20%) at optimized conditions was accepted by the taste panellists and above 20%KB incorporation was found to decrease overall acceptability score.

Thin-Layer Drying of Mate Leaves (Ilex paraguariensis) in a Conveyor-Belt Dryer: A Semi-Automatic Control Strategy Based on a Dynamic Model

A feedback strategy of drying control of mate leaves in a thin-layer conveyor-belt dryer was experimentally evaluated. Moisture content in the discharge of the continuous dryer was controlled by manually adjusting the speed of the moving belt between 3.7 × 10−4 and 15.2 × 10−4 m s−1 for approximately 7200 s in 120 s time steps. The sets of PID controller parameters and manipulated conveyor velocities were computed with a dynamic drying model at conditions identical to those found in the closed-loop experiments. The model is represented by a system of two partial differential equations built by energy and solute mass balances in the solid phase of the dryer. A large set of experimental drying curves and temperature of mate leaves as a function of drying time, in the temperature range from 55 to 130°C, confirmed the reliability of the considered model. Experimental closed-loop responses of discharge moisture content in the presence of disturbances in the feed moisture content (≈ 0.5 − 1.7 dry basis) and variations in set-point (≈ 0.1 − 1.0 dry basis) validated the suggested control scheme.

Effects of extrusion cooking conditions and chemical leavening agents on lysine loss as determined by furosine content in corn based extrudates

The aim of this study was to investigate the effects of different variables on lysine loss as determined by furosine content in corn-based extrudates. Three formulations were prepared to study the effects of different chemical leavening agents, processing conditions (feed moisture content: 22, 24 or 26%; exit die temperature: 110 or 150 °C), and extrusion cooking methods (with/without CO2 injection) on furosine formation. Furosine levels of extrudates from both extrusion methods decreased around 20% when feed moisture content was increased from 22% to 26%. Amadori compounds (precursor of furosine) are formed in the early stages of the Maillard reaction, and later they are converted to further products. Consequently, furosine contents of extrudates significantly decreased as exit die temperature increased from 110 to 150 °C. Furosine contents of extrudates produced with sodium- and ammonium-bicarbonate at 150 °C exit die temperature significantly decreased, while the ones produced at 110 °C significantly increased. This may be due to accelerated formation of fructosyllysine at higher pH values followed by early degradation at 150 °C. The CO2 injection method did not have a significantly different effect on furosine content of extrudates than that produced by the conventional extrusion method, but had a positive effect on the physical properties of extrudates.

Characteristics of destarched corn fiber extrudates for ethanol production

The effect of extrusion on characteristics of destarched corn fiber was investigated. Extrusion was conducted at a screw speed of 300 rpm, feed rate of 100 g/min, feed moisture content of 30%, melt temperature of 140 °C and die diameter of 3 mm. After extrusion, characteristics of raw and extruded destarched corn fiber were compared. Raw and extruded destarched corn fibers were enzymatically saccharified and fermented using Saccharomyces cerevisiae (ATCC 24858). Extrusion pretreatment resulted in low crystallinity index, significant decrease in degree of polymerization and microstructure disruption of destarched corn fiber for enzymatic saccharification. This provides a significant increase in xylose yield for fermentation. Significant increase in protein digestibility and free amino nitrogen were additional benefits of extrusion for yeast nutrient in fermentation. Therefore, extruded destarched corn fiber significantly increased (p < 0.05) ethanol yield (29.08 g/L) and higher conversion (88.79%) by improving the physiochemical and functional properties for saccharification and fermentation.

Analysis of Operation Parameters in a Dual Fluidized Bed Biomass Gasifier Integrated with a Biomass Rotary Dryer: Development and Application of a System Model

An integrated system model was developed in UniSim Design for a dual fluidized bed (DFB) biomass gasifier and a rotary biomass dryer using a combination of user-defined and built-in unit operations. A quasi-equilibrium model was used for modelling biomass steam gasification in the DFB gasifier. The biomass drying was simulated with consideration of mass and energy balances, heat transfer, and dryer’s configuration. After validation using experimental data, the developed system model was applied to investigate: (1) the effects of gasification temperature and steam to biomass (S/B) ratio on the gasification performance; (2) the effect of air supplied to the fast fluidized bed (FFB) reactor and feed biomass moisture content on the integrated system performance, energy and exergy efficiencies. It was found that gasification temperature and S/B ratio have positive effects on the gasification yields; a H2/CO ratio of 1.9 can be achieved at the gasification temperature of 850 °C with a S/B ratio of 1.2. Consumption of excessive fuel in the system at higher biomass feed moisture content can be compensated by the heat recovery such as steam generation while it has adverse impact on exergy efficiency of the system.