Inlet Air Temperature Research Articles

Characterization and effect of optimized spray-drying conditions on spray-dried coriander essential oil

Coriander (Coriandrum sativum L.) essential oil (CEO) has many beneficial features, including antimicrobial and antifungal properties along with good aroma. It also has an important role in food processing and preservation. However, CEO is highly volatile and sensitive to external factors (heat, light and oxygen), as well as susceptible to lipid oxidation due to environmental and general processing conditions. This limits water solubility, making it difficult to incorporate CEO into aqueous food matrices, which further limits their industrial application. Spray-drying encapsulation may prevent CEO oxidation, increase CEO oxidative stability and improve their physicochemical properties. In this study, spray-dried CEO (SDCEO) was prepared using a mini laboratory-scale spray-dryer and the processing conditions were optimized. The SDCEO were characterized in respect to free fatty acids (FFA), peroxide values (PV), fatty acid (FA) profiles, Fourier-transform infrared spectroscopy (FTIR) and physical morphology by scanning electron microscopy (SEM). Results indicated that the maximum value of FFA, PV, fatty acid composition (including petroselinic, linoleic and oleic acids) in SDCEO were observed at the following spray-drying conditions: an inlet-air temperature (IAT) of 140 °C, needle speed (NS) of 2 s and the wall-material (WM) at 25%. The minimum values were observed at an IAT of 180 °C, NS of 4 s and WM of 30%. Analysis of variance and the interaction effects of independent factors showed that IAT and WM significantly positively influenced the response for good oxidative stability. Thus, SDCEO is likely to be used as a natural active ingredient in the food processing, cosmetic, nutraceutical and pharmaceutical industries with high stability, and may be stored for a long time without evaporation or oxidation.

Predicting Temperature and Humidity in Roadway with Water Trickling Using Principal Component Analysis-Long Short-Term Memory-Genetic Algorithm Method

The heat dissipated from high geo-temperature underground surrounding rocks is the main heat source of working faces, while thermal water upwelling and trickling into the roadway will notably deteriorate the mine’s climate and thermal comfort. Predicting airflow temperature and relative humidity (RH) is conductive to intelligent control of air conditioning cooling and ventilation regulation. To accommodate this issue, an intelligent technique was proposed, integrating a genetic algorithm (GA) and long short-term memory (LSTM) based on rock temperature, inlet air temperature, water temperature, water flow rate, RH, and ventilation time. A total of 21 input features including over 200 pieces of data were collected from an independently developed modeling roadway to construct a dataset. Principal component analysis (PCA) was conducted to reduce features, and GA was used to tune the LSTM and PCA-LSTM architectures for best performance. The following research results were yielded. The proposed PCA-LSTM-GA model is more reliable and efficient than the single LSTM model or hybrid LSTM-GA model in predicting the air temperature Tfout and humidity RHout at the end of the water trickling roadway. The importance scores (ISs) indicate that Tfout is mainly influenced by the surrounding rock temperature (IS 0.661) and the inlet air temperature (IS 0.264). While RHout is primarily influenced by the rock temperature in the water trickling section (IS 0.577), the inlet air temperature (IS 0.187), and the trickling water temperature and flow rate (total IS 0.136), and it has an evident time effect. In addition, we developed relevant equipment and provided engineering practice methods to use the machine learning model. The proposed model, which can predict the mine microclimate, serves to facilitate coal and geothermal resource co-mining as well as thermal hazard control.

Analysis of Cavity Disk Heat Transfer by Solving Inverse Heat Transfer Problem

Abstract The flow and heat transfer within compressor rotor cavities of aero-engines is a conjugate problem. The operating conditions buoyancy forces, caused by radial temperature difference between the cold throughflow and the hotter shroud, can influence the amount of entrained air significantly. By this, the heat transfer depends on the radial temperature gradient of the cavity walls, and in turn, the disk temperatures are dependent on the heat transfer. In this article, disk Nusselt numbers are calculated in reference to the air inlet temperature and in comparison to a modeled local air temperature inside the cavity. The local disk heat flux is determined from measured steady-state surface temperatures by solving the inverse heat transfer problem in an iterative procedure. The conduction equation is solved on a 2D mesh using a validated finite element approach, and the heat flux confidence intervals are calculated with a stratified Monte Carlo approach. An estimate for the amount of air entering into the cavity is calculated by a simplified heat balance. The major influences on the Nusselt number were found to be the mass flowrate entering the cavity and the density of the fluid inside the cavity.

POTENTIAL OF RICE BRAN PROTEIN POWDER PRODUCTION TO INCREASE PADDY INDUSTRY PRODUCTIVITY

The demand for alternative protein sources has been steadily increasing due to concerns about sustainability and animal welfare. Rice bran, a byproduct of rice milling, is a potential source of protein with high nutritional value. This study aims to investigate the production of rice bran protein powder using a pilot-scale ultrasonic spray dryer.The research methodology involves several key steps. First, rice bran is collected from the milling process and undergoes a series of pretreatment steps, including defatting and protein extraction. The extracted protein solution is then concentrated and purified to remove impurities and enhance protein content. The resulting protein solution is then fed into a pilot-scale ultrasonic spray dryer for powder production. The pilot-scale ultrasonic spray dryer offers advantages such as precise control over particle size, improved solubility, and reduced agglomeration. The drying conditions, including inlet air temperature, feed rate, and atomization pressure, are optimized to obtain a high-quality protein powder with desirable physicochemical properties. The produced rice bran protein powder is characterized for its protein content, amino acid profile, functional properties (such as solubility, emulsifying capacity, and foaming ability), and particle size distribution. These properties are evaluated to assess the feasibility of using rice bran protein powder in various food applications, including bakery products, beverages, and nutritional supplements. The results of this study provide insights into the potential of rice bran protein as an alternative protein source and highlight the effectiveness of pilot-scale ultrasonic spray drying as a production method. The findings contribute to the development of sustainable protein ingredients and support the utilization of rice bran, a byproduct that would otherwise be underutilized or discarded.

Yearly hour-by-hour performance evaluation of a SIEMENSE gas turbine power plant for Australia’s climate condition with and without a novel intake air pre-cooling strategy

The power production, fuel consumption and revenue of any gas turbine (GT) power plant are greatly affected by variations in ambient conditions (entering air into the compressor). This paper simulates and reports the power output and efficiency of a gas turbine-based power plant (SGT-750 SIEMENSE) using around 8000 h-by-hour yearly weather data of two regions of Australia (north and south) without pre-cooling, with sole M−cycle pre-cooling and finally with an innovative hybrid pre-cooler. The hybrid pre-cooler consists of a Maisotsenko indirect evaporative cooler (M−cycle) and an absorption chiller (ABC). Briefly, the results indicate that power raise of the GT plant using the M−cycle IEC alone is about 2 % in temperate regions and 4 % in hot regions, while it would be about 4 % and 6 % respectively if the hybrid pre-cooler is used. Reducing the inlet air temperature by 8–10 °C increases the generated power of a GT with pre-cooler by 8–9 %.

Impact of Preheating on Flame Stabilization and NOx Emissions From a Dual Swirl Hydrogen Injector

Abstract Flame stabilization, flame structure, and pollutant emissions are investigated experimentally on a swirled injection system operating with globally lean air/hydrogen mixtures at atmospheric conditions and moderate Reynolds numbers. This injector consists of two coaxial ducts with separate injection of hydrogen into a central channel and of air into an annular channel. Both streams are swirled. The resulting flames exhibit two stabilization modes. In one case, the flame takes an M-shape and is anchored to the hydrogen injector lips. In the second case, the flame is aerodynamically stabilized above the injector and takes a V-shape. Regions of existence of each stabilization mode are determined according to the operating conditions. For low air flow rates, the flame can be either anchored or lifted above the hydrogen injector lips depending on the path followed to reach the operating condition. At high air flow rates, the flame is always lifted regardless of the trajectory followed. The impact of air inlet temperature on these stabilization regimes is then evaluated from T= 300 K up to 770 K. Flame re-attachment is shown to be controlled by edge flame propagation and the impact of preheating is well reproduced by the model. Unburnt hydrogen and NOx emissions are finally evaluated. Unburnt hydrogen is only observed for global equivalence ratios below 0.4 and at ambient inlet temperature. NOx emissions decrease when the global equivalence ratio is reduced. Furthermore, at fixed global equivalence ratio, NOx emissions decrease as the thermal power increases, regardless of air preheating and the flame stabilization regime. At high power, NOx emissions reach an asymptotic value that is independent of the thermal power. The impact of flame shape, air preheating, and combustion chamber wall heat losses on NOx production is also evaluated. NOx emissions are shown to scale with the adiabatic flame temperature Tad at the global equivalence ratio and the residence time inside the combustor.

Effects of cluster dextrin encapsulation on the properties and antioxidant stability of fractionated Riceberry protein hydrolysate powder prepared by bromelain

In this work, the biological properties of fractionated Riceberry bran protein hydrolysate obtained by ultrafiltration (URBPH) were evaluated and the possibility of using cluster dextrin to produce hydrolysate powder by spray-drying was investigated. Fractionation into peptides < 3 kDa was observed to improve antioxidant activity. URBPH < 3 kDa was then freeze-dried (FD-URBPH) and spray-dried (SD-URBPH) at different inlet air temperatures of 100–160 °C. The water solubility and antioxidant activity of FD-URBPH were higher than those of SD-URBPH. Nevertheless, encapsulation of hydrolysate with 10% cluster dextrin and an inlet temperature of 120 °C was also successful in maintaining protein qualities, which showed high 2,2′-azino-bis 3-ethylbenzthiazoline-6-sulfonic (ABTS•+) scavenging activity (89.14%) and water solubility index (92.49%) and low water activity (aw = 0.53). Moreover, encapsulation preserved the antioxidant activity of peptides during gastrointestinal digestion better than the free form. URBPH and its spray-dried microcapsules could be used as bioactive ingredients in functional drinks or foods.

Modeling and optimization of spray drying process parameters using artificial neural network and genetic algorithm for the production of probiotic (Lactiplantibacillus plantarum) finger millet milk powder

AbstractConsumers have been more inclined towards functional food due to various health issues. Non‐dairy‐based probiotic milk could be the potential alternative to fulfill consumer demand. Spray drying of functional health drinks could enhance the shelf life and reduce the transportation cost of developed food powder. The current study was focused on the modeling and optimization of spray‐drying process parameters using an artificial neural network (ANN) coupled with a genetic algorithm (GA). The data so obtained using ANN‐GA was also compared with the data obtained using response surface methodology (RSM) coupled with desirability function (DF). The results indicated that the ANN model was better at predicting the response parameters compared to the RSM model with a higher correlation coefficient (R) of .9997, .9994, .9964, and .9992 for training, testing, validation, and all datasets, respectively. The optimum conditions obtained using RSM‐DF were 160.41°C of inlet air temperature, 33.77% of maltodextrin content, and 138.79 mL/h of feed rate while that for ANN‐GA were 160.87°C, 20%, and 200 mL/h. The RSM‐DF method proved to be better for the optimization of response parameters. Therefore method selection for modeling and optimization of process and response parameters must be based on fulfilling the specific criteria.Practical ApplicationsNon‐dairy milk production has gained popularity in the area of research and product development. Various process protocols have been reported to produce high‐quality non‐dairy milk to fulfill the demand for a vegan diet. However, nutrient bioavailability, longer shelf life, product stability, and consumer acceptability are hard to obtain from cereal‐based non‐dairy milk. The current study contributes to produce spray‐dried milk powder followed by fermentation at optimum drying conditions with good quality and stability. The process has been modeled and optimized in the study using advanced statistical tools such as ANN‐GA and RSM‐DF. They can effectively predict the quality parameters and determine the optimal conditions for new experimental data.

Design and analysis of earth-air heat exchanger integrated into the building ventilation system

This experimental study intent to design and to analyse the passive cooling effect of an Earth-Air Heat Exchanger (EAHE) integrated into the building ventilation system. For hot climate regions, ground thermal inertia can be used as a passive cooling strategy in the building ventilation where the air supply comes from outside with hot temperature. The proposed EAHE device consists of two main-components; a water tank and a PVC hose as a heat-exchanger between air and water in the tank. Fresh air from outside with a flow rate of 5.63 kg. min-1 is blown through a 2 ½-inch PVC hose, and cooled by the low water-soil temperature before being distributed into the room. To analyze the effectiveness of the passive cooling effect, measurements are performed for several parameters; inlet and outlet air temperature of ventilation ducts and indoor-outdoor air temperature using a multichannel thermocouple data logger for 48 hours of measurement time. The results present that the EAHE device can reduce the air temperature to a maximum of 10.6 °C. This proposed EAHE device presents good performance as a passive cooling technique for a building ventilation system, especially during the day.

Effect of Inlet Air Temperature and Quinoa Starch/Gum Arabic Ratio on Nanoencapsulation of Bioactive Compounds from Andean Potato Cultivars by Spray-Drying

Nanoencapsulation of native potato bioactive compounds by spray-drying improves their stability and bioavailability. The joint effect of the inlet temperature and the ratio of the encapsulant (quinoa starch/gum arabic) on the properties of the nanocapsules is unknown. The purpose of this study was to determine the best conditions for the nanoencapsulation of these compounds. The effects of two inlet temperatures (96 and 116 °C) and two ratios of the encapsulant (15 and 25% w/v) were evaluated using a factorial design during the spray-drying of native potato phenolic extracts. During the study, measurements of phenolic compounds, flavonoids, anthocyanins, antioxidant capacity, and various physical and structural properties were carried out. Higher inlet temperatures increased bioactive compounds and antioxidant capacity. However, a higher concentration of the encapsulant caused the dilution of polyphenols and anthocyanins. Instrumental analyses confirmed the effective encapsulation of the nuclei in the wall materials. Both factors, inlet temperature, and the encapsulant ratio, reduced the nanocapsules’ humidity and water activity. Finally, the ideal conditions for the nanoencapsulation of native potato bioactive compounds were determined to be an inlet temperature of 116 °C and an encapsulant ratio of 15% w/v. The nanocapsules obtained show potential for application in the food industry.

Optimal supply air temperature with respect to data center operational stability and energy efficiency in a row-based cooling system under fault conditions

This is the first study of data center row-based cooling strategies under fault conditions. An optimal supply air temperature (SAT) for row-based cooling is proposed to ensure energy efficiency and operational reliability. The appropriate SAT for emergency operation is determined by evaluating how long the allowable IT equipment's inlet air temperature (IAT) can be maintained by only running the fan of the computer room air handling (CRAH) unit when the chilled water supply is interrupted. Three cases with SAT values of 20 °C, 22 °C, and 24 °C are evaluated in a numerical analysis, and the maintenance potential of the IAT is assessed by analyzing 600 s of transients from the time of cooling failure. In all cases, the IAT is almost the same as the SAT under normal cooling, but in cooling failure, the time to reach downtime beyond the allowable IAT is 246s in Case 1, 133s in Case 2, and 85s in Case 3. Response strategies to cooling failure include increasing uninterruptible power supply (UPS) capacity and applying a thermal buffer tank. The study concludes that it is reasonable to set the SAT of row-based cooling to 22 °C or lower and to install a thermal buffer tank in the chilled water system for effective downtime delay. These results are based on a rack power density of 7 kW/rack.

Process development for pilot-scale spray drying of ultrasmall iron (oxyhydr)oxide nanoparticles

In manufacturing iron (oxyhydr)oxide nanoparticles, drying is often necessary to increase stability or to enable granulation and tableting. Lyophilization is a simple drying method, although it is characterized by high energy consumption and high cost. This study aims to demonstrate that spray drying is a suitable alternative for preparing iron (oxyhydr)oxide nanoparticles. A Design of Experiment approach was used varying the inlet air temperature, feed flow rate, and feed concentration. Especially a low feed flow rate was beneficial for low residual moisture (< 7%) and high yield (> 80%). The process was subsequently transferred to pilot scale at a feed flow rate of 2.3 kg/h. The nanomaterial had comparable properties and efficacy to the freeze-dried product. However, about 15% lower yield and 35% lower energy consumption were found for spray drying the nanoparticles. This study shows that spray drying is a suitable alternative to freeze drying for iron (oxyhydr)oxide nanoparticles.

Thermo-economic assessment of air conditioner utilizing direct evaporative cooling: A comprehensive analysis

As concerns regarding energy consumption and environmental impact continue to grow, the need for efficient and sustainable cooling technologies becomes increasingly significant. Among various alternatives, direct evaporative cooling (DEC) has emerged as a promising solution due to its energy-efficient operation and low environmental footprint. This paper aims to provide a comprehensive thermo-economic assessment of a 5.25 kW capacity split air conditioner (SAC) integrated with direct evaporative cooling, focusing on evaluating its performance, energy consumption, coefficient of performance(COP), and economic viability. A numerical model is developed to determine the reduction in the condenser inlet air temperature due to direct evaporative cooling. The ambient temperature (30–45 ⁰C), relative humidity (20–80 %), and evaporator temperature (3–12 ⁰C) are taken as the design variables. Box–Behnken design (BBD) technique of response surface methodology is applied for multi-objective optimization. The COP, total cost rate (TCR), and total exergy destruction (E˙D,t) are set as the objective functions. Cooling capacity, life period, operation time, interest rate, maintenance factor, and electricity cost are taken as constants. The thermoeconomic optimization evolved maximized COP enhancement of 68.94 %, and reduction in TCR and ED,t by 26.12 % and 57.23 %, respectively. The water consumption to energy saving ratio varies from 5.5 to 9.8 L/kWh for different months of the cooling season. The thermoeconomic performance and sustainability of DECSAC is observed to significantly improve compared to conventional SAC specifically in hot-dry climates. The simple payback of the proposed system ranges between 1.21 to 2.99 years depending upon the operating conditions.

Direct Numerical Simulation of a Reacting Turbulent Hydrogen/Ammonia/Nitrogen Jet in an Air Crossflow at 5 Bar

The article aims to analyze the fluid dynamics and combustion characteristics of a non-premixed flame burning a fuel mixture derived from ammonia partial decomposition injected in an air crossflow. Nominal pressure (5 bar) and inlet air temperature (750 K) conditions are typical of micro-gas turbines. The effects of strain on the maximum flame temperature and NO generation in laminar non-premixed counter-flow flames are initially explored. Then, the whole three-dimensional fluid dynamic problem is investigated by setting up a numerical experiment: it consists of a Direct Numerical Simulation, based on accurate transport, chemical, and numerical models. The flow topology of the specific reacting jet in crossflow configuration is described in terms of its main turbulent structures, like shear layers, ring, and horse-shoe vortices, as well as of its leeward recirculation region anchoring the flame. The reacting region is characterized by providing instantaneous spatial distributions of temperature, heat release, and some transported chemical species, including NO, and calculating the Flame Index to identify non-premixed and premixed combustion local conditions. The latter is quantified by looking at the distribution of the volume fraction associated with a certain Flame Index versus the Flame Index and at the distribution of the average values of both the Heat Release Rate and NO versus the Flame Index and the mixture fraction.

Experimental study on thermal characteristics of thermosyphon with water condenser and LTES condenser in parallel (TWCLC)

Since the servers' workload of the data center varies over time, the cooling system needs to be adjusted according to the on-demand cooling load. Thermosyphon integrated system is efficient in meeting the time-varying cooling load, and thermal energy storage is one of the important methods to eliminate the overheating load. To deal with the time-varying cooling load, a novel integrated thermosyphon with water condenser and latent thermal energy storage (LTES) condenser in parallel (TWCLC) is developed and experimentally studied. The effects of refrigerant filling ratio and inlet conditions on thermal performance are analyzed. With the increase of the refrigerant filling ratio ranging from 52.1 % to 80.2 %, the cooling capacity of TWCLC decreases. The LTES condenser enhances and then weakens the cooling capacity of TWCLC, by a maximum of 18.1 % improvement compared with the water-cooled thermosyphon. The subcooling temperature of the TWCLC is lower than that of the water-cooled thermosyphon; the superheating temperature is always zero. The water flow rate and water temperature have little effect on the cooling capacity of TWCLC. But it could not start up in due course with inlet cold water temperature higher than 16 °C. With the increases of the inlet air temperature and air flow rate, the cooling capacity of the evaporator side increases due to the common function of the water condenser and LTES condenser.

Numerical Simulation of Fluid-Solid Coupling Heat Transfer in Excavating Roadway

Heat damage is an urgent problem to be solved in deep mining. The relevant factors in the excavation roadway significantly affect the cooling effect in the roadway. In this paper, the fluid-solid coupling heat transfer model of excavating roadway is established using numerical simulation, and the influence of inlet air temperature, wind speed, original rock temperature and surrounding rock thermal conductivity on roadway temperature is studied. The results show that the larger the initial rock temperature, the higher the airflow temperature in the roadway, and the greater the decrease of the airflow temperature after ventilation. The lower the inlet air temperature, the more significant the decrease in the airflow temperature in the roadway after ventilation, and the airflow temperature in the roadway gradually stabilizes with the extension of the ventilation time. The greater the wind speed, the lower the airflow temperature in the roadway, and the more significant the decrease of the airflow temperature in the roadway after ventilation. When the wind speed reaches a specific value, the cooling effect of ventilation is minimal. The higher the thermal conductivity of the surrounding rock, the higher the outlet temperature simultaneously.

Modelling, validation and analysis of preheating strategy of fuel cell vehicle during Subzero cold start

The rapid cold start capability of fuel cell vehicles in low-temperature environments is one of the key factors restricting their commercialization. Reasonable and effective strategies are crucial to improving the low-temperature cold start capability of fuel cell vehicles. In this paper, a cold start model of fuel cell system is established, and the model is verified based on the cold start experiment of a hybrid fuel cell vehicle. The necessity of the coolant preheating strategy in the cold start is analyzed, and the important role of the coolant preheating strategy in helping the fuel cell system to start quickly at -10°C and below is demonstrated. Furthermore, the effects of air inlet temperature, air inlet flow rate, and external heater power on the cold start performance are investigated. The results show that when the air inlet temperature rises from -13°C to 65°C, the start time is shortened from 279 s to 234 s (reduced by 16.13 %). And at low air inlet temperatures, the lower flow rate of air can significantly reduce the temperature difference and maintain uniformity of temperature inside the stack, while at a higher temperature, the higher air flow rate causes the temperature of the cell stack to rise rapidly. For heating power, the start time is shortened from 421 s to 126 s (reduced by 70.07 %) when the heating power is increased from 3 kW to 11 kW. However, it will cause a larger temperature difference between the inlet and outlet of the coolant, which is not conducive to the uniform distribution of the temperature inside the stack. Thus, the start time can be shortened by increasing the air inlet temperature, air inlet flow rate, and heating power with the consideration of the temperature difference that the stack can withstand. The model developed by this study provides an effective way to analyze the fuel cell system during cold start, which is useful for the development of control strategies in the future.

Performance augmentation and machine learning-based modeling of wavy corrugated solar air collector embedded with thermal energy storage: Support vector machine combined with Monte Carlo simulation

At present, artificial intelligence methods have been effectively utilized for predicting the complex performance of storage-based solar thermal technologies for cooling/heating applications. It is crucial to have accurate energy storage-based sustainable system estimation, which would contribute to increased operational time, thus maximizing the overall efficiency of solar energy-based storage systems. Hence, this work introduces a comparative experimental investigation and support vector machine (SVM) modeling on a wavy corrugated solar air collector (WCSAC) with and without using a paraffin wax storage container. Experiments on the WCSAC were performed under three air flow rates of 0.540, 1.68, and 3.72 kg/min and two paraffin layer thicknesses of 2 cm and 4 cm, respectively. Moreover, improved SVM models implemented in MATLAB software are developed for predicting the thermal performance parameters; including air temperature ratio, average air temperature, convective heat transfer coefficient, and energy efficiency for the WCSAC. The optimal solution of the SVM modeling is developed by incorporating the Karush-Kuhn-Tucker conditions and several kernel functions. In addition, a sensitivity analysis is also conducted to explore the significance of model input parameters (air inlet temperature, time, solar irradiance, air flowrate, PCM layer thickness) on the output parameters prediction using the Monte Carlo simulation technique. The experimental results presented that the daily energy efficiencies of the WCSAC equipped with 4 cm paraffin layer thickness are 24.0 %, 20.39 %, and 16.37 % higher than that of the WCSAC without PCM at airflow rates of 3.72, 1.68, and 0.54 kg/min, respectively. Moreover, the connective heat transfer coefficient of the WCSAC with PCM is more than 1.20 times that yielded with the WCSAC without PCM. Additionally, the SVM simulations showed that the optimal solution of the SVM model is developed by incorporating the Karush-Kuhn-Tucker conditions and Lagrangian function kernel function, which revealed a superior accuracy with the highest coefficient of determination of 0.990 and 0.950 for training and test processes, respectively.

Experimental study of the influence of pad angle on the thermal performance of a direct evaporative cooling system

One of the most important parts of direct evaporative cooling systems is the cooling pad. Pads vary in materials and construction features. The parameters studied in the performance of the pads are air speed, pad thickness, geometrical characteristics, and its configuration and the provided water flow rate. The performance of the pads is usually determined through saturation efficiency, pressure drop, temperature drop and humidity increase in the treated air, evaporation and water consumption, cooling capacity, coefficient of performance, and heat and mass transfer coefficients. Since the geometry and how to place the pad in the evaporative cooling system is one of the most important issues related to the performance of such systems, the present work experimentally investigates the amount of cooling and evaporation of the direct evaporative cooling system under 5 different angles of placement of the cellulose pad in relation to the vertical position. It includes angles of 0^circ, 5^circ, 10^circ, 15^circ, and 20^circ in 5 different air speeds, 2 different inlet water flow rates, 2 inlet air temperatures, and 2 different inlet water temperatures. Results show that the lowest output temperature, highest air relative humidity, highest coefficient of performance (about 12% more than 0^circ), highest saturation efficiency, and highest evaporation rate are obtained in the case of a 15^circ of cooling pad placement angle.

Investigation of a Solar-Powered Evaporative Cooling System under Tunisian Climate

The demand for cooling continues to increase in line with environmental changes and a greater desire for human comfort. In north Africa and middle eastern countries, and particularly in Tunisia, cooling constitutes a big problem as it is recommended for human and animal breeding. This study aimed to analyze the performance and suitability of an evaporative cooling system powered by solar energy and to assess the economic and environmental impact under Tunisian weather conditions. Numerical modeling and simulations were performed, revealing the effects of inlet air temperature and relative humidity on system performances. An experimental study based on the construction of an evaporative cooling prototype formed by environmentally friendly and locally available components was also performed. This study showed the dependence of the process performances on the humidity and temperature of the ambient air. The obtained results revealed that the efficiency of the evaporative cooler exceeds 90%, with maximum efficiency being reached at a high wet-bulb depression, while minimum efficiency was observed when the dry air has a high relative humidity and a low dry-bulb temperature. Experimental results showed that, for input temperatures ranges between 36 and 47 °C and relative air humidity between 15 and 50%, a direct humidifier produces air with a temperature range between 25 and 29 °C and humidity range between 55% and 85%. Thus, evaporative cooling is feasible and suitable under Tunisian climate conditions during the hot season.