Water Spray Rate Research Articles

Study on pressurization characteristics of single-screw steam compressor with water spray cooling under fluctuating heat source operating conditions

For a water-injected single-screw steam compressor (SSSC), the performance of the compressor is significantly affected by the water spray rate. However, the precise relationship between the water injection parameters and the operating parameters of the heat source under fluctuating heat source operating conditions (FHSOC) has not been elucidated. This paper introduces a constructed thermodynamic analysis model for the wet compression process under FHSOC aiming to explore the impact of fluctuating heat source parameters such as inlet steam temperature (IST) and inlet steam dryness (ISD) on the thermodynamic performance parameters of the compressor. The operational performance of the SSSC is then analyzed and compared under two distinct conditions: optimal water spray rate (OWSR) and fixed water spray rate (FWSR). The results demonstrate that when the IST of the SSSC increases within the range of 375 K–400 K, there is an initial decline followed by an increase in both the leakage rate and volumetric efficiency. Simultaneously, displacement and power consumption decrease, while adiabatic indicated efficiency and OWSR increase. Within this range, an optimal synergy is observed between IST and water spray parameters enabling the compressor to exhibit superior lubrication, sealing, and pressurization performance. On the other hand, when the ISD increases within the range of 0.92–1, the total heat transfer in the compression chamber decreases, and the leakage, OWSR, displacement, power consumption, adiabatic indicated efficiency, and volumetric efficiency all show varying degrees of increase. Regarding the volumetric efficiency corresponding to the OWSR, the impact of ISD on volumetric efficiency surpasses that of IST to a significant degree.

The temperature effect and system equilibrium of preparing powdered activated coke sorbent in a rapid carbonization-activation two-step process

ABSTRACT In this study, a rapid carbonization-activation two-step process for preparing powdered activated coke (PAC) sorbent is proposed. Shengli lignite is utilized as the feedstock to prepare PACs through this process, employing various combinations of carbonization and activation temperatures. The pore structure, surface functional groups, yield and SO2 adsorption properties of the PACs are comprehensively analyzed. Additionally, Aspen Plus software is employed to calculate the system equilibrium of this process. Results demonstrate that the performance of the prepared PAC is predominantly influenced by the activation temperature. Despite variations in carbonization temperature, consistent performance and yield are achieved as long as the activation temperature remains constant. Through the experimental design, the optimum combination of carbonization temperature and activation temperature of the two-step process is optimized, that is, the carbonization temperature is 750°C, and the activation temperature is 950°C. The SBET of the PAC prepared under optimal condition is 550 m2/g, and its SO2 adsorption capacity is 116.58 mg/g, which are both higher than that of the other ACs. The system equilibrium indicates that the optimal parameters for PAC preparation can be achieved by employing a water and air spray technique between the combustion zone and activation zone, with a water spray rate of 1.70 (kg/kg coal for combustion) and an air spray rate of 2.75 (kg/kg coal for combustion). In addition, the maintenance of system equilibrium necessitates the combustion of a certain amount of gas to elevate the temperature through the injection of a specific quantity of air into the carbonization step, with an air spray rate set at 11.00 (kg/kg coal for combustion).

Study on control of upstream smoke propagation in road tunnels by using a side-wall sprinkler system

Side-wall sprinkler systems used for fire suppression in road tunnels have been found to redistribute the longitudinal air flow within the tunnel, with the most notable feature being an acceleration of the airflow near the ceiling. The present work is driven by the motivation of utilizing the acceleration effect to block the upstream smoke propagation in cases when the ventilation rate is sub-critical. A nozzle prototype that has practical applications in road tunnels was selected for a side-wall water spray system in a 300 m road tunnel, and a total of 60 cases were modelled using the CFD code FDS (version of 6.7.3) to investigate its smoke blocking effect. Experiments and correlations in the literature have validated the accuracy of the FDS method. The confinement velocity reduction rate, which is determined as the reduction of the ventilation rate required to stop the smoke front point at a given position, was found to be positively affected by both the water spray rate and the ventilation rate and was successfully correlated using dimensionless momentums of these two factors. By comparing the confinement velocity reduction rates with the increases in the ceiling velocity in the absence of tunnel fire, utilization efficiencies of the spray-induced accelerations were further obtained.

PCDD/Fs emissions in a large-scale hazardous waste incinerator under different operation conditions: Effective reduction strategies and an applicable correlation

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) emissions from hazardous waste incinerators (HWIs) have emerged as a great threat to environmental safety and human health, resulting in urgent effective control of the high emissions. In this study, the emission characteristics of chlorobenzenes (CBzs), PCDD/Fs from a large-scale HWI in China were studied under different conditions (inhibitor injection; feeding waste component). The total concentrations of CBzs and PCDD/Fs in stack gas from the HWI ranged from 2.18 to 22.94 μg/Nm3 and 0.98–18.53 ng/Nm3, respectively. Increased chlorine content of feeding waste led to increased PCDD/Fs concentrations, especially PCDDs. The inhibition efficiency of NH4H2PO4 with thiourea and Ca(OH)2 is 42.2% and 9.4% respectively. 2,3,4,7,8-PeCDF (30.7%–44.2%) and 1,3-DiCBz (61%–83%) was the dominating congener of I-TEQ values and CBzs concentration under all conditions, respectively. Furthermore, the relationship among PCDD/Fs, CBzs, traditional pollutants (carbon dioxide, sulfur dioxide, nitric oxide, hydrogen chloride, and particulate matter), and operational parameters were analyzed under six conditions to predict PCDD/Fs by indicators. Results indicated that PeCBz (r = 0.764), HCBz (r = 0.814), and quench tower water spray rate (r = −0.796) present strong correlations with I-TEQ values. Considering the effect of multicollinearity, the multiple regression model with PeCBz and water spray rate of quench tower as indicator variables (R2 = 0.801) has the best fitting effect, with an average absolute relative difference between measured and predicted I-TEQ of 34.8%. The study not only reveals the effects of hazardous waste composition and air pollution control devices (APCDs) parameters on PCDD/Fs emission characteristics, but also provided an accurate prediction method for PCDD/Fs emissions.

Design Space Approach for the Optimization of Green Fluidized Bed Granulation Process in the Granulation of a Poorly Water-Soluble Fenofibrate Using Design of Experiment.

In the pharmaceutical industry, the systematic optimization of process variables using a quality-by-design (QbD) approach is highly precise, economic and ensures product quality. The current research presents the implementation of a design-of-experiment (DoE) driven QbD approach for the optimization of key process variables of the green fluidized bed granulation (GFBG) process. A 32 full-factorial design was performed to explore the effect of water amount (X1; 1–6% w/w) and spray rate (X2; 2–8 g/min) as key process variables on critical quality attributes (CQAs) of granules and tablets. Regression analysis have demonstrated that changing the levels of X1 and X2 significantly affect (p ≤ 0.05) the CQAs of granules and tablets. Particularly, X1 was found to have the pronounced effect on the CQAs. The GFBG process was optimized, and a design space (DS) was built using numerical optimization. It was found that X1 and X2 at high (5.69% w/w) and low (2 g/min) levels, respectively, demonstrated the optimum operating conditions. By optimizing X1 and X2, GFBG could enhance the disintegration and dissolution of tablets containing a poorly water-soluble drug. The prediction error values of dependent responses were less than 5% that confirm validity, robustness and accuracy of the generated DS in optimization of GFBG.

Experimental investigation of water absorption and penetration in clay brick masonry under simulated uniform water spray exposure

In this study, we performed an experimental investigation of water absorption and penetration in clay brick masonry exposed to cyclic water spraying by employing a newly developed test setup. Several parameters, including brick absorption properties and different mortar joint profiles, were investigated. The specimens were exposed to a uniform water spray rate ranging between 1.7 and 3.8 l/m2/h, and water absorption and dampness patches on the non-exposed backside (the protected side) of the specimens monitored continuously. The results indicate that the amount of absorbed water is highly dependent on the water absorption coefficient and absorption capacity of the bricks, whereas the mortar joint profiles do not influence water absorption. The first dampness patches on the specimens' backside appeared in the vicinity of the head joint, and the time until the first patch appeared correlated well with water content levels. Accordingly, the first visible dampness patches appeared on the specimens' backside at water content levels corresponding to 50%–60% of full saturation level. Additionally, the specimens' backside reached 90% dampness at water content levels corresponding to 95% of full saturation level. As a feature attributed to the absence of known defects and zero differential air pressure, no measurable amounts of penetrated water could be collected at the specimens’ backside. The newly developed test setup might facilitate verification of moisture simulations and provide a basis for rational decision-making concerning clay brick masonry design and maintenance.

Numerical investigation on the stability of tunnel smoke stratification under the effect of water spray and longitudinal ventilation

Tunnel smoke stratification has been reported to exist in the vicinity of a fire source, even under moderate ventilation conditions, which is of importance for occupant evacuation. To understand the effects of a water spray on its stability, a two-layer thermal flow model was built, and a series of scenarios considering different ventilation rates, water spray rates and smoke temperatures were numerically investigated. The ability of the Fire Dynamic Simulation (FDS) tool to predict such a two-phase problem was determined by validating against experimental and zone model data found in the literature. Then the tracer method was adopted to closely observe the smoke and droplet interactions in the two-layer model used in this paper. General effects of the ventilation flows and water spray on the maximum smoke logging distance and its corresponding horizontal displacement were observed. It was found that increasing the ventilation rate promotes the horizontal displacement but weakens the maximum downward distance, while increasing the water spray rate boosts the movements in both directions. Models based on nondimensional analysis for predicting the smoke displacements and the heat loss due to water spray were obtained. The observation of droplets indicates that a water spray globally blocks the horizontal smoke movement, and the upstream part of the water spray contributes 56.7% of the total downward drag forces. This work is helpful in revealing some of the underlying mechanisms behind the interactions of water spray and smoke stratification in the presence of longitudinal ventilation.

Investigation of electronic controlled direct water injection for performance and emissions of a diesel engine running on sunflower oil methyl ester

Among alternative fuels with low emission profiles used in diesel engines, biodiesels are renewable, biodegradable and non-toxic, but cause higher NOx emission than diesel fuelled engines. In this study, direct water injection (DWI) with electronical control is used for reducing NOx emissions from a diesel engine running on sunflower oil methyl ester (SOME). DWI is applied during compression stroke through a separate water injector on cylinder head. Using 20% SOME blend (B20) as fuel the effects of water ratios, 40%, 60%, 80%, and 100% (W100), on performance, combustion and emissions are investigated. As water is injected directly into diesel engines running on B20 blend, slight decline in engine performance parameters compared to B20 blend. And, to distinguish the effect of DWI and B20 blend, standard engine data (diesel fuel) are presented in accompany. Besides, with direct water injection, a distinctive reduction (56%) in NOx emissions and increases in HC, CO, and smoke emissions are observed, compared to B20 blend results. It has been found that the ignition delay period is shortened using B20 blend, while prolonged in direct water injection case at the same operating conditions. Since it is possible to achieve a significant reduction in all direct water injection rates compared to standard NOx values, it would be optimal to keep the water spray rate around W80 for all engine parameters. As a result, utilizing direct water injection on diesel engines running on biodiesel blends has been found a useful tool to reduce NOx emissions.

Pressure-equalised façade systems: Evaluation of current watertightness test standards used to assess the performance of enclosure components

Watertightness test standards are used to evaluate enclosure components in terms of water penetration resistance. Currently, there is a wide variety of watertightness tests in use for façades elements and wall systems; however, none of them specifically addresses and evaluates the drainage capacity in pressure-equalised façade systems. In addition, recent research has revealed many inconsistencies in the possibility of these test standards to represent all possible conditions that can occur under different operating conditions, varying building configurations and at different locations. As such, the three main variables for water penetration testing (water spray rate, pressure differential and duration of the pressure application) have been called into question. Nonetheless, these studies do not bring up the protocols and other technical specifications incorporated in the test standard procedures. Furthermore, neither are concerns raised about the influence that these other parameters might have on the outcomes of the watertightness test, which is the aim of this research. To this end, the article provides a critical review of current watertightness tests standards from around the world in the first section. Thereafter, a thorough comparison of the information incorporated in the protocols of the test standards has been carried out. The evaluation and discussion of the test parameters and technical specifications incorporated in the tests standards is undertaken based on the state of the art and laboratory experiments of three mock-ups with pressure-equalised façade systems, where the water management capacity of the system is assessed. As a result of this research work, a guideline was prepared for the establishment of test procedures when developing new watertightness standards for pressure-equalised façade systems.

Prototype of horizontal bio-trickling air scrubber (HBAS) for ammonia removal in swine farm

Modelling of Bio-Trickling Air Scrubber (HBAS) system is one of the methods to treat biological odor and gas emission in air treatment of manufacturing facility management. A cheaper way of efficient gas elimination is using sprinkling water in the direction of air flow in the media microbial adhesion. Samples of ammonia gas was continuously collected throughout swine production for 20 weeks. The experimental systems consisted of six different conditions by varying the amount of scrubbed water, the space between water spray and media, and the amount of media materials. Microorganism species in media, which affected to ammonia removal, were also classified. The results indicated that the highest efficiency of ammonia removal was 51.9% at the experimental condition as follows: 1) water spray rate of turn on: turn off - 60 : 30 seconds, 2) distance between water spray and media of 1 meter, and 3) a half of media microbial adhesion area. The treated ammonia concentration was lower than the standard value of the chemical in working atmosphere as determined by the American Conference of Governmental Industrial Hygienist (ACGIH TLV), giving ammonia not more than 25 ppm. Additionally, media bio-scrubber could classify five bacteria species (Brachybacterium sp., Micromonospora sp., Methylobacterium sp., Rhodococcus rubber and Cellulosimicrobium sp.), which ammonia was used as a natural resource. The main mechanism in gas removal was proposed by the liquid adsorption, whereas the microorganism adhering to the media did not affect in statistical signification. Improvement of removal efficiency could be achieved by an increase of gas retention time in the system and the space between water spray and media.

Effects of granulation process variables on the physical properties of dosage forms by combination of experimental design and principal component analysis

The current study was to understand how process variables of high shear wet granulations affect physical properties of granules and tablets. The knowledge gained was intended to be used for Quality-by-Design based process design and optimization. The variables were selected based on the risk assessment as impeller speed, liquid addition rate, and wet massing time. Formulation compositions were kept constant to minimize their influence on granules properties. Multiple linear regression models were built providing understanding of the impact of each variable on granule hardness, Carr's index, tablet tensile strength, surface mean diameter of granules, and compression behavior. The experimental results showed that the impact of impeller speed was more dominant compared to wet massing time and water addition rate. The results also revealed that quality of granules and tablets could be optimized by adjusting specific process variables (impeller speed 1193 rpm, water spray rate 3.7 ml/min, and wet massing time 2.84 min). Overall desirability was 0.84 suggesting that the response values were closer to the target one. The SEM image of granules showed that spherical and smooth granules produced at higher impeller speed, whereas rough and irregular shape granules at lower speed. Moreover, multivariate data analysis demonstrated that impeller speed and massing time had strong correlation with the granule and tablet properties. In overall, the combined experimental design and principal component analysis approach allowed to better understand the correlation between process variables and granules and tablet attributes.

Numerical study on performance improvement of air-cooled condenser by water spray cooling

Water spray cooling is an efficient way to enhance heat transfer of the air-cooled condenser (ACC) of power generating unit under high ambient temperatures. Taking the air-cooled 300 MW power generating unit as object, the flow and temperature fields of ACC with water spray cooling were analyzed by numerical simulation with experimental validation. Based on the air flow field inside ACC cell, an improved water spray nozzles arrangement was proposed to enhance the cooling capacity. The inlet air temperature and back pressure of turbine were compared with that under the original nozzles arrangement. The water consumptions including that of water droplets pre-cooling evaporation in air flow, liquid film evaporation on the finned tube bundles, and drainage of redundant water were obtained. The influences of water spray rate, spray direction and nozzles distance on cooling performance were investigated. The results showed that the improved nozzles arrangement is expected to provide efficient cooling performance and significant reduction in back pressure of the objective power generating unit. The improved nozzles arrangement with upward spray direction and nozzles distance of 0.8 m can be applied to the design of water spray system in ACC. In addition, the obtained redundant drainage water under various ambient conditions provided the evidence for spray water rate optimization.

Simulation on deacidification performance of waste incinerator flue gas by rotating spray drying

The models describing the mass transfer and chemical reaction of flue-gas−slurry drops in the deacidification tower of waste incineration plants are established. The internal dynamics are simulated and the effects of flue-gas inlet velocity, stoichiometric ratio, drop size and water spray rate, on deacidification performance, are evaluated. Results show that simulated desulphurisation and dechlorination rates are 58.97% and 99.99% and the removal rate of HCl is greater than SO2. A high-temperature zone is found in the upper part of central axis, whereas low-temperature zones are observed at the right wall and bottom. Flow field is characterized with complex recirculation zones, wherein the recirculation zone emerged on the upper-right entrains a small part of drops towards the right wall. Approximately 60% of the total removal amount of SO2 and 90% of HCl are absorbed in the upper part. Slurry drops completely evaporate in 5 s after entering the deacidification tower. The deacidification performance is improved with the increase in stoichiometric ratio and water spray rate, as well as the decrease in inlet gas velocity and drop size. Excellent deacidification performance is expected under flue-gas inlet velocity of 7.1 m/s, drop size of 50–70 μm, and water spray rate of 600 L/h.

Study on mechanical vapor recompression system with wet compression single screw compressor

The mechanical vapor recompression (MVR) is a highly energy-efficient process, in which the compressor is the core unit. In order to improve the compressor efficiency the distilled water is atomized and injected into the compressor to cool down the overheated vapor during compression. The performances of the system with water injection compressor were tested and compared with a common compressor without water injection. Four groups of tests with different water spray rate were analyzed experimentally. The tests show that without water injection, the temperature difference increases sharply with frequency rising. It also shows that the values of compression ratio and evaporation capacity increase with the frequency increasing, and the values vary with the spray flow rate: the higher the flow rate, the larger the values. The values for the situations with water injection are closer to each other with the increas of the water spray rate while the situation without water injection is much lower. Specific moisture extraction rate, abbreviated as SMER is a parameter which reflects the removal water from the feed per kilowatt hour. With spray flow rate of 300kg/h the SMER is 34kg/kWh at frequency of 20Hz while the value is 25kg/kWh without water injection.

Experimental study on cooling performance of air conditioning system with dual independent evaporative condenser

Evaporative condenser is an energy efficient and environmentally friendly air conditioning equipment. This paper proposed an air conditioning system using dual independent evaporative condenser and investigated the cooling performance. Many factors, such as evaporator water inlet temperature, compressor frequency, air dry-bulb temperature, air velocity and water spray rate, which influenced the cooling performances of air conditioning system with evaporative condenser have been investigated. The results indicated that cooling capacity and coefficient of performance (COP) increased significantly with the increasing of evaporator water inlet temperature (12–25 °C), the air velocity (2.05–3.97 m s−1) and the water spray rate (0.03–0.05 kg m−1 s). However, COP decreased with the increasing ambient air dry-bulb temperature (31.2–35.1 °C) and the compressor frequency (50–90 Hz). Furthermore, the heat transfer coefficient (K0) was 232–409 W m−2 K−1 in different air velocity and water spray rate.

Controlled Cooling of Hot Rolled Steel Channels by Water Spraying on the Final Cooling Bed

The objective of this research is to design an effective and relatively simple method for controlled cooling of hot rolled steel channels by water spraying on the final cooling bed after continuous cast steel billets passing through reheating furnace and sequential rolls to form channels. The need for this research arose as the channels were being cooled by forced air draft and natural convection which brought the temperature of the channels to about 270°C (518°F) at the shear stand. Steel at this temperature is too hot for convenient handling by the operators. Additional cooling by water spraying would be an acceptable solution but such cooling should be designed to enable an acceptable microstructure to be developed in the channel, as the microstructure of steel is strongly affected by nonequilibrium cooling through the eutectoid range: the mechanical properties of steel are a consequence of the microstructure. The approach followed in this investigation was first to develop a finite element method (FEM) to determine the temperature profiles in the channel subjected to cooling by water spraying and natural convection and arrive at suitable water spray rates to bring the temperature of the channel at the shear stand to levels suitable for convenient handling. PATRAN was used for preprocessing and ABAQUS for processing and post processing. Next, laboratory experiments were conducted to determine the microstructure and hardness of channels at the spray rates found suitable through FEM, to suggest the water spray rate most suitable for providing a temperature convenient for handling and for developing a desirable microstructure.

Proposed method for calculating water penetration test parameters of wall assemblies as applied to Istanbul, Turkey

Water penetration of a building envelope assembly is typically assessed on the basis of the degree of watertightness (i.e. lack of water ingress) of the components of the assembly when subjected to simulated driving rain conditions. Test standards provide the magnitude and extent of these test conditions as suggested by the test parameters, i.e. the water spray rates and pressure differences and the dwell time over which these are to be applied. Such conditions would presume to simulate driving rain and wind conditions of locations spread over a broad geographical area. For example, the water spray rate suggested for use in watertightness performance tests in EN 12155—Curtain walling–watertightness–laboratory test under static pressure—is considered appropriate for simulating driving rain and wind conditions for locations across Europe. However, test parameters should be based on the expected driving rain intensities and wind pressures that are likely to occur for a specific climate and a given return period. It might also be based on the building type (e.g. high or low-rise building), or even on the location on the building facade. Hence, a method is required for calculating water penetration test parameters for specific buildings located in a specific climate. The purpose of this paper is to propose a method for calculating water penetration test parameters. A survey of existing methods is first provided that focuses on the quantification of driving rain on buildings and thereafter, calculation of water penetration test parameters. The merits and drawbacks of these methods are then discussed. Based on this review, a method for calculating test parameters is proposed and is applied to developing water penetration test parameters for Istanbul, Turkey. A comparison of test parameters calculated from the proposed method with those given in existing Turkish standards TS EN 12155–Curtain walling–watertightness–laboratory test under static pressure—and TS ENV 13050—Curtain walling–watertightness–laboratory test under dynamic condition of air pressure and water spray—related to Istanbul, indicated that the water spray rate given in the TS standards is higher than spray rates calculated from the proposed method for return periods of 5, 10 and 30 years.