Low Inlet Air Temperature Research Articles

Technical and Economic Feasibility Analysis of Solar Inlet Air Cooling Systems for Combined Cycle Power Plants

In this study, the thermodynamic behavior of a combined cycle power plant with integrated solar-driven inlet air cooling was simulated for Tehran, Phoenix, and Houston during warm-hot seasons. A considerable reduction in the output power was realized during hot ambient conditions due to the lower density of the air and lower mass flow rate to the turbines. The output power decreases from 306.6 to 260.8 MW as ambient temperature increases from 15 to 45 °C. This research focuses on utilizing solar cooling systems to achieve low inlet air temperature to generate high-electricity yields. Four different types of solar collectors and two different absorption chiller units were selected and simulated for each city to achieve the required goal. It was identified that integrating a solar inlet air cooling (SIAC) system can avert the reduction in output power with no impact on efficiency. The humid climatic condition in Houston and the low electricity cost in Tehran posed some challenges in designing a feasible SIAC system. However, by optimizing the solar collectors and cooling capacities, an optimal solution for utilizing inlet air cooling in humid climates is presented. In terms of overall impact, the evacuated flat plate collector (EFPC) coupled with a double-effect absorption chiller displayed the best economic performance among the four variants under study. In Phoenix, this combination can maintain output power during hot days with a DPR of 2.96 years.

Analysis and Possible Improvements of Scramjet Engines: The Effective Thrust and the Combustion Stability Problems

The scramjet is the representative of the future jet engine, and it has irreplaceable advantages in terms of working performance and service life. Although it has been developed more than fifty years, there are many problems in the driven system of the scramjet engine. This paper mainly focuses on the problems of the effective thrust and the combustion stability. The research shows that how the pressure ratio affects the positive thrust and the combustion stability. Furthermore, this paper also shows that the elements which can affect the pressure ratio. The lower inlet air temperature is beneficial to enhance the thrust. According to the relevant research which apply the CJ detonation theorem to find the possible reason for the combustion instability. For the possible improvements, the research found that the engine thrust at different speed and the allowable maximum speed. The type of fuel and the reactivity of the fuel can influence the thrust.

Influence of intake air temperature on the performance of gasoline engines using a different type of fuel

The aim of the present study is to investigate the effect of Intake air temperature on the performance of gasoline engines. Various factors are taken that affect the performance of four-stroke gasoline engines. Changes in air intake temperature have a significant impact on the performance of a petrol engine. Consequently, an increase or decrease in the global ambient temperature will impact the performance and air quality of gasoline engines in particular. therefore, this investigation will discover the hot value of intake air temperatures that effects engine performance. This study tested two Kurdistan-Iraq gasoline kinds at different intake temperatures (25Co, 35Co, 45Co, and 50Co). Experiments utilized a four-stroke spark ignition _engine that operated at various rates of speeds (1300, 1500, 1800, 2000, 2300 and 2500 revolutions per minute) under a half load with a 50% throttle opening. The experimental outcomes were compared with Ricardo Wave software simulations. The Ricardo Wave's theoretical outcomes were in good agreement with the experiment data it showed a near 5% to 10% variance between simulation and practical data. Additionally, utilizing fuels having higher RON increases brake power owing to gasoline's greater hydrogen content and the engine's high octane fuel requirement. Also, lower inlet air temperatures would be denser (more oxygen) and offer a larger mass flow during each piston cycle. Hence, due to those factors, brake power was enhanced by reducing intake temp and raising RON. Generally, the experiment results demonstrated that utilizing higher octane number gasoline under lower intake temperature improved engine performance which demonstrates higher power, torque, and efficiency with lower bsfc compared to utilizing higher intake temperature and lower octane gasoline.

Studies on supercritical fluid extraction and spray drying effect on the quality of instant tea of Mulberry leaves (Morus alba L.)

Mulberry (Morus alba L.) is a Moraceae family plant that is often used for silkworm feeding. The value-added forms of mulberry leaves (Morus alba) significantly help to reduce blood sugar, cardiovascular diseases, inflammation levels, cholesterol and fight against heart disease. A process technology comprising supercritical fluid extraction (200 bar and 50 ºC), optimizing spray drying (inlet air temperature of 147 ºC and feed flow rate of 3 mL/min) and fluidized bed drying (45 ºC) was developed for production of instant tea from mulberry leaves. Physical, biochemical and reconstitution properties of the developed instant powder were determined. The powder had excellent handling and flow characteristics at low inlet air temperatures (130 °C). The increase in input air temperature resulted in a considerable improvement in reconstitution characteristics. The developed instant mulberry tea powder under optimized conditions showed Hausner ratio of 1.09, Carr's index of 9.35%, solubility of 97.51%, moisture content of 2.29%, protein of 1.32%, fat of 0.45% and energy of 403.94 kcal/100 g. The prepared instant mulberry tea had more acceptability in terms of sensory qualities compared to commercial mulberry tea.

Numerical simulation on heat transfer characteristics of gas pipeline in urban utility tunnel

Recent years, more and more utility tunnels are adopted in China with the development of urbanization. Compared to the conventional method for utility installation, the utility tunnel that co-locates more than one utility underground eliminates the need for frequent excavation and reinstatement of roads. Ventilation systems are essential in utility tunnel for safety reasons, especially for gas compartments. This paper aims to evaluate effect of the longitudinal ventilation on gas temperature field by investigating the heat transfer process on gas pipeline. Numerical models including convection, conduction and radiation were established and then used to simulate the heat transfer process on gas pipeline. Results show that the ventilation has a great impact on gas temperature. In case of low inlet air temperature, the gas temperature may drop below -10 °C, which is too low to guarantee a normal operation.

Effect of Maltodextrin Concentration and Inlet Air Temperature on Properties of Spray Dried Powder from Reverse Osmosis Concentrated Sweet Orange Juice

Sweet orange juice is an important part of diet since it is nutritious beverage offering good taste and play significant part in a healthy diet. High hygroscopicity, thermo-plasticity and presence of low molecular weight components in sweet orange juice offer low glass transition temperature (Tg), likely to form soft particle with sticky surface leading to sticky powder during drying. Maltodextrins are amorphous drying aids that tend to inhibit sugar crystallization and form a high Tg product after drying. In this study, the effect of the different spray drying parameters on the quality of powder derived from control and concentrated juice at three inlet air temperatures 120, 130 and 140 °C and at three levels of juice total soluble solids (TSS): maltodextrin levels at 1:0.5; 1:1 and 1:1.5 were studied. The impact of inlet air temperature and maltodextrin concentration has significantly affected various properties of sweet orange powder. For control juice, process yields increased with increase in inlet air temperature and maltodextrin concentration. However, for reverse osmosis (RO) concentrate, process yield increased with increase in maltodextrin concentration and decreased with increase in inlet air temperature. For control juice, process yields obtained were in the range of 12.59-41.16% and in case of concentrated juice, the process yield obtained was in the range of 21.35-56.95% at different combinations of inlet air temperature and maltodextrin concentrations. Spray-dried powder was considered as “possible” and “fair” in terms of flowability and cohesiveness. Vitamin C retention was high at lower inlet air temperature with lower concentration of maltodextrin.

Effects of fuel variation and inlet air temperature on combustion stability in a gas turbine model combustor

In this study, influences of fuel variation and inlet air temperature on the combustion stability characteristics in a gas turbine model combustor were experimentally investigated. Test fuels involved three selected single component hydrocarbons, including one linear alkane (n-decane), one branched alkane (iso-octane) and one cyclic alkane (methylcyclohexane (MCH)). RP-3 jet fuel was also selected as a technical reference. For all the fuels, experiments were conducted at a fixed equivalence ratio of 0.86 and varying inlet air temperatures from 383 to 483 K. Results showed that RP-3 and n-decane exhibited similar stability behaviors. At low inlet air temperatures, when the combustor was fueled with RP-3 and n-decane, the flame was stabilized and anchored in the combustor. The combustor then shifted to thermo-acoustically unstable state when the inlet air temperature exceeded a threshold value, which was associated by large-scale flame shape variations. On the other hand, noticeable differences can be observed for MCH and iso-octane flames, which featured thermo-acoustically unstable combustion throughout all the tested conditions, and unique mode-shift phenomenon was observed when the inlet air temperature was raised from 403 K to 423 K. Additional flame dynamics was visualized by OH⁎ chemiluminescence imaging. The underlying mechanisms that led to the differences in combustion stability and flame dynamics of the tested fuels were discussed with respect to their differences in physicochemical properties.

Conjugate heat and mass transfer model for predicting thin-layer drying uniformity in a compact, crossflow dehydrator

A conjugate heat and mass transfer model was implemented into a commercial CFD code to analyze the convective drying of corn. The Navier–Stokes equations for drying air flow were coupled to diffusion equations for heat and moisture transport in a corn kernel during drying. Model formulation and implementation in the commercial software is discussed. Validation simulations were conducted to compare numerical results to experimental, thin-layer drying data. The model was then used to analyze drying performance for a compact, crossflow dehydrator. At low inlet air temperatures, the drying rate in the compact dehydrator matched the thin-layer drying rate. At higher temperatures, heat losses through the external walls resulted in temperature and moisture variations across the dehydrator.

Curcumin encapsulation by spray drying using Aloe vera mucilage as encapsulating agent

AbstractIn this work, curcumin was spray‐dried (SD) with Aloe vera mucilage as the encapsulating agent giving particular attention to the effect of the relevant process parameters (feed flow rate, atomization speed, and inlet air temperature) on the resulting properties of the SD powders. The powders obtained were analyzed by infrared spectroscopy, scanning electron microscopy, rheology, and release profiles. Results show that the best drying conditions are low SD inlet air temperature (150 °C), low feed flow rate (1.5 L/hr), and high atomization speed (27,500 rpm). These conditions produced particles with smooth morphologies, preserving the total phenolic content (0.0611 μg EAG), with a radical scavenging capacity of 911.48 μmol Trolox/mg. Release profiles revealed an extended release of encapsulated material with a maximum of about 65% at 24 hr for these conditions and point out the suitability of encapsulated systems for potential applications in functional foods, antioxidant systems, pharmaceutical, and organic pigments.Practical applicationsThis research presents an optimization method to obtain powders of mucilage (Aloe vera, Av)‐curcumin (Cu) by spray drying (SD), where the Av was used as wall material to encapsulate Cu and obtain the best process conditions (SD) to produce prolonged delivery systems of antioxidant compounds that can be used in the food and pharmaceutical industry. The encapsulated systems were analyzed by rheological tests and were supported with other characterizations, such as antioxidant capacity, morphology (SEM), chemical (FT‐IR), and releasing profiles.

Maltodextrin: A consummate carrier for spray-drying of xylooligosaccharides

The aim of this study was to evaluate the influence of spray-drying on the powder qualities and microstructures of prebiotic xylooligosaccharides (XOS). The relationships between glass transition temperature (Tg) and XOS retention, moisture content, drying yield as well as specific surface area under different inlet air temperatures and maltodextrin concentrations were investigated. Antioxidant activity retention, hygroscopicity, color attributes, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) of the spray-dried XOS product were also assessed. The results indicated that an increase in inlet air temperature decreased the moisture content, hence the Tg value was increased. Higher maltodextrin concentration increased the Tg value, and was attributed to the molecular weight increase. The wall deposition was a tendency to occur when the temperature beyond the Tg, reduced the drying yield. Higher temperature and wall deposition promoted the decomposition of XOS into monosaccharide. The crust formation rate of droplets and stickiness of microparticles were affected by Tg, and hence, influenced the specific surface area. The antioxidant activity retention of XOS exhibited a concentration-dependent behavior. The hygroscopicity of the microparticles could be reduced by both of the low inlet air temperature and high maltodextrin concentration. According to the results of color attributes, XRD and SEM, the particles were colorless and amorphous, and tended to become more spherical and scattered with the addition of maltodextrin. The FT-IR analysis confirmed that no chemical reaction occurred between XOS and agent, which indicated that maltodextrin is a promising carrier for producing bioactive XOS powder.

Color, bioactive compounds and morphological characteristics of encapsulated Asian pear juice powder during spray drying.

Encapsulated Asian pear juice powder was produced through spray drying using three maltodextrin levels (15, 20, and 25% w/v) and three inlet air temperatures (130, 150, and 170°C). The impact of maltodextrin concentrations and inlet air temperatures on color, bioactive compounds, and morphological characteristics of encapsulated Asian pear juice powder were investigated. Maltodextrin concentrations and inlet air temperatures significantly influenced L* and b* values of encapsulated Asian pear juice powder. Increasing inlet air temperatures increased total phenolic content, whereas the vitamin C content decreased. Vitamin C content was strongly correlated with particle size, inlet air temperature, and maltodextrin concentration. ABTS+ radical-scavenging activity was highly correlated with total phenol content while DPPH radical-scavenging activity was highly correlated with vitamin C content. Encapsulated powders made with higher inlet air temperature and higher maltodextrin concentration had lowest median particle diameter with a smoother, more regular and rounded outer surface than those of encapsulated powders produced with lower inlet air temperature and lower maltodextrin concentration. Therefore, the results demonstrate that high-quality encapsulated Asian pear juice powder could be manufactured by adding 15% (w/v) maltodextrin and spray-drying at 170°C.

Numerical and Experimental Investigation of Solar Air Collectors Performance Connected in Series

In the present work, the investigation on the performance of series of solar air collectors to obtain high temperature air was performed. The first collector has been studied experimentally, while the rest of the series collectors have been investigated numerically with the same boundary conditions. The experimental and numerical results of the first collector show acceptable accruement, this lead to calculate the series of collectors numerically. The results indicated that collector’s series do not work with the same efficiency. The first collector will work at low inlet air temperatures, which lead to increase in the efficiency, on the contrary for the other collectors. The results showed that, it can be determined the required number of collectors in series that necessary to obtained the required outlet air temperature.

Inherent operational characteristics and operational stability of a variable speed direct expansion air conditioning system

Previous studies on the inherent operational characteristics of a variable speed (VS) direct expansion (DX) air conditioning (A/C) system at a fixed degree of refrigerant superheat (DS) setting without considering its operational stability have been conducted. Therefore, a follow-up study on the inherent operational characteristics of a VS DX A/C system considering its operational stability has been carried out and the study results are reported. Using an experimental VS DX A/C system, the inherent correlations between its output total cooling capacity (TCC) and equipment sensible heat ratio (E SHR) at different combinations of compressor speed and supply fan speed were studied and the unstable operating points of speed combinations under different DS settings and inlet air states identified. The experimental results suggested while different DS settings may not significantly influence the inherent correlations between TCC and E SHR, but did impact the operational stability. A lower DS setting would result in a larger unstable operating region. Furthermore, VS operation and different inlet air states to the DX evaporator also influenced the operational stability. A higher compressor speed or a lower supply fan speed, and a lower inlet air temperature or relative humidity would lead to a higher chance to instability.

Texture and Antioxidant Properties of Puffed Pounded-Unripe Rice Coated by Marigold Extract as Affected by Fluidized-Bed Coating Conditions

We investigated the effects of fluidized-bed coating parameters on texture and antioxidant properties of puffed pounded-unripe rice (PPUR) coated by marigold extract with variations of inlet air temperature of 50, 60 and 70°C and coating solution feed rate of 5, 7.5 and 10 ml/min. The results showed that increasing inlet air temperature tended to reduce the hardness of coated PPUR, while the adverse effect was found with increasing feed rate. Both parameters did not significantly affect the crispiness. We also found that fluidizing air temperature and feed rate significantly affect total phenolic content (TPC), total flavonoid content (TFC) and their antioxidant activities. Higher feed rate slightly increased TPC and antioxidant activities as determined by DPPH and FRAP assays, but not for TFC. As mostly found in medicinal plants, all antioxidant properties decreased when temperature increased. Based on the amount of TPC and TFC and their antioxidant activities, we recommend low inlet air temperature and high feed rate to improve health benefits of puffed pounded-unripe rice as a breakfast cereal. However, agglomeration must be concerned when using high feed rate.

Spray drying of coffee leaf extract

The coffee leaf extract formulation has been used as resistance inductor in plants and to control phytopathologies. This work aimed to study the influence of spray drying process variables with the use of maltodextrin as carrier on the characteristics of the powder, by using a central composite rotational design (CCRD). The independent variables were maltodextrin concentration (X1, 0 to 30 % w/v), coffee leaf extract concentration (X2, 2 to 32 % w/v), inlet air temperature (X3, 180 to 250 °C) and air flow rate (X4, 3.5 to 5.5 m3min-1). The response variables were collection efficiency (h), moisture content (MC), phenolic compounds content (Ph), soluble solids (S) content, wettability (We) and particle size (Me). The results showed that the combination of a higher concentrations of coffee leaf extract (X2) (32%) and lower inlet air temperatures (X3) (180°C) make the best drying performance. This process condition lead to a powder with higher Ph, S, We, Me and lower MC. Therefore, the use of high air flow rates (X4) increase the collection efficiency (h) of process and the use of low maltodextrin concentration (X1) lead to better preservation of phenolic compounds content (Ph) on coffee leaf extract powdered.

Survival, oxidative stability, and surface characteristics of spray dried co-microcapsules containing omega-3 fatty acids and probiotic bacteria

ABSTRACTThe objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130°C, 150°C, and 170°C) and outlet (55°C, 65°C, and 75°C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130°C and 150°C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170°C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130–65°C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 ± 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.

Modeling and Simulation of a Co-current Rotary Dryer

Abstract Mathematical models including mass and energy conservation were developed in order to predict the outlet particles temperature and moisture. As the inlet air temperature increased, the outlet particles temperature increased as well and the outlet particles moisture decreased quickly. The outlet particles temperature and moisture changed a little as a function of the speed of rotation at the low inlet air temperature, while the outlet particles temperature and moisture increased very apparently with the speed of rotation increased at the high inlet air temperature. The error of the simulation results compared to the experimental data showed good accuracy for particles temperature and moisture content. The mathematical model performs well to predict the outlet particles temperature and moisture content.

Preparation and Solidification of Redispersible Nanosuspensions

To test the feasibility of preparing redispersible powders from nanosuspensions without further addition of drying protectants, Lovastatin was processed into nanosuspensions and subsequently converted into a powder form using a spray-drying process. The effects of spray-drying process parameters and stabilizers on the properties of the spray-dried powders were evaluated. The inlet air temperature was found to have the most pronounced impact; a low-inlet air temperature consistently yielded dried powders with improved redispersibility. This was attributed to the low Peclet number associated with a low-inlet air temperature, making nanoparticles less prone to aggregation and coalescence during spray drying, as evidenced by the well-defined boundary shown between nanoparticles in the SEM photomicrographs of the spray-dried microparticles. The influence of atomization pressure is significant particularly at a low-inlet air temperature. The redispersibility index value of the powder is dependent on the type of stabilizers used in the nanosuspension formulation. Spray-dried powders with acceptable redispersibility were prepared with drug concentration as high as 3%. In conclusion, with optimized process parameters and selected stabilizers, spray drying is a feasible process in the solidification of nanosuspensions with high drug loading and acceptable redispersibility.

Experimental investigations on thin polymer desiccant wheel performance

In this study, the performance of a new polymer desiccant wheel (DW), which can be used for dehumidification in a solid desiccant cooling system, was investigated. In order to investigate the compact design of the DW for compact cooling system, DWs were evaluated at four levels of thickness while varying the inlet air temperature, humidity ratio, regeneration temperature, and rotational speed. It was found that lower inlet air temperature and higher humidity ratio are in favor of better DW performance. Higher regeneration temperature (60 °C) would bring a reduced marginal benefit in terms of latent coefficient of performance (COPlatent). Test results also indicate that the optimum rotational speed decreases while DW thickness increases. Three thin DWs (30, 50 and 70 mm) were compared with the typical thick DW (150 mm) and it was found that 50 and 70 mm DWs have the potentials in the compact cooling system with the maximum moisture removal capacity (MRCmax) based on specific volume (MRCmax/DW Volume) 1.2 and 0.7 times higher than that of 150 mm DW, respectively. In addition, the maximum COPlatent of 50 and 70 mm DW can be up to 0.45 and 0.5, respectively.

Microstructure of Calcium Stearate Matrix Pellets: A Function of the Drying Process

Drying is a common pharmaceutical process, whose potential to modify the final drug and/or dosage form properties is often underestimated. In the present study, pellets consisting of the matrix former calcium stearate (CaSt) incorporating the active pharmaceutical ingredient ibuprofen were prepared via wet extrusion and spheronization. Subsequent drying was performed by either desiccation, fluid-bed drying, or lyophilization, and the final pellets were compared with respect to their microstructure. To minimize the effect of solute ibuprofen molecules on the shrinking behavior of the CaSt, low ibuprofen loadings were used, as ibuprofen is soluble in the granulation liquid. Pellet porosity and specific surface area increased during desiccation, fluid-bed drying, and lyophilization. The inlet-air temperature during fluid-bed drying affected the specific surface area, which increased at lower inlet-air temperatures rather than the pellet porosity. The in vitro dissolution profiles were found to be a nonlinear function of the specific surface area. Overall, the microstructure, including porosity, pore size, and specific surface area, of CaSt pellets was a strong function of the drying conditions.