Air Volume Flow Research Articles

Investigating droplet emission during speech interaction

AbstractConversations (normal speech) or professional interactions (e.g. projected speech in the classroom) have been identified as situations which increase individuals’ risk of exposure to respiratory viruses (including SARS-CoV-2) due to the high production of potentially infectious droplets. The few studies addressing this topic contain several methodological and linguistic limitations. This paper describes and validates an original combination of various methods, aimed at providing a global understanding of the complex physiological mechanisms underlying droplet emission during speech production. Twenty-one French speakers produced pseudowords and sentences under different phonetic conditions (e.g. loud vs normal intensity). In Experiment 1, we measured the airflow volume and airflow velocity exhaled from the mouth during speech. In Experiment 2, we measured the airflow velocity exhaled from different positions in the space around the mouth. In Experiment 3, we measured the number and size of expelled droplets. In all experiments, participants were asked to produce pseudowords and sentences under different phonetic conditions in an interactive setting. To validate our methodology, we tested the impact of voice intensity on the physiological measurements. We found that pseudowords and sentences spoken with loud intensity generated increased airflow volume and velocity compared to those spoken with normal intensity. Additionally, the number of droplets was higher for pseudowords spoken with loud intensity compared to normal intensity. From a methodological point of view, our study went beyond previous research by using multiple measures characterising droplet emission during speech. Furthermore, we applied an innovative experimental design, considering droplet emission in an interactive linguistic setting.

Optimization of ventilation and dust removal parameters in plateau extra-long tunnel inclined shaft based on orthogonal numerical simulation test method

Ventilation and dust removal system in the inclined shaft of the plateau long tunnel is an important component for ensuring safe excavation. The arrangement of wind tube and the volume of air flow have a significant impact on the movement of dust. In order to address the issues of poor ventilation and severe dust pollution in the inclined shaft of plateau long tunnels, this study establishes a dust generation and transportation model for the face of the inclined shaft based on the determination of dust source parameters and their physicochemical characteristics during the excavation process. The results indicate that the particles are predominantly spherical with an approximate diameter of 4 μm at a magnification of 500 times. The dust in high-altitude inclined shafts exhibits poor wettability, with a hydrophobic tendency during the excavation phase, making a ventilation dust removal scheme appropriate. After determining the physical parameters corresponding to the elevation of the inclined shaft, a series of orthogonal numerical simulations involving 3 factors at 5 levels were conducted. Analysis of range and variance revealed that optimal dust control is achieved when the air duct height is 5.725m, the distance from the working face is 21m, and the exit wind speed is 29.71m/s. Comparative analysis confirmed the rationality of the ventilation dust removal scheme under the optimal combination of ventilation parameters. This provides guidance for engineering and environmental management in similar construction scenarios.

Dry fractionation of sunflower press cake as tool to improve its technofunctional properties

Depending on the oil production technology, at least 60% of the oilseeds input such as sunflower, pumpkin or canola remain as by-product, which is usually denoted as press cake (PC) and contains a significant amount of fiber and protein. Its further valorization in food requires knowledge on the technofunctional properties of the press cake and on possibilities for improving its value. Aim of the current study was to evaluate the effect of two separation techniques, namely targeted sieving and air classification, on composition, and physical as well as technofunctional properties of fractions of sunflower press cake previously milled to < 1.0 mm or < 2.0 mm. It is evident for both separation techniques that fines fractions obtained by using smaller sieves or lower air volume flow showed an increased protein content, with a protein enrichment factor of up to 1.47. Using PC < 2.0 mm as raw material, protein separation efficiency, a combined measure for protein content and yield, was higher after separation by air classification. Whereas protein solubility was not affected by the particle size distribution of the separated fractions, emulsion activity and emulsion stability were improved especially for the small particle fractions separated from PC < 2.0 mm.

A convolutional neural network to control sound level for air conditioning units in four different classroom conditions

Air conditioning units (ACUs) are widely used in educational areas like classrooms in order to ensure the occupant’s well-being and to control CO2 concentration (by ventilating using fresh outdoor air). However, the noise level of these ACUs can disrupt the learning environment. Consequently, we propose an approach based on machine learning that is able to distinguish between the different acoustic situations in a classroom, and to dynamically adjust the air volume flow accordingly. To this end, the present algorithm was trained with sound recordings in four different scenarios in a classroom. Both Mel spectrogram and Cochleagram are considered and applied for the task of training the convolutional neural networks (CNN) model, thus enhancing published works in the literature, which only considered the Mel spectrogram. Results show how the Cochleagram is pre-eminent to handle the CNN model training over the Mel spectrogram. Accordingly, we use the Cochleagram for the CNN model training, which is subsequently used for detecting the current situation in the room and adapting the ACU operation to this situation. The results show that running ACUs in high mode provides a learning environment with low CO2 concentration and high noise. Instead, controlling ACU based scenario predictions made by the CNN model provides a good learning environment with adequate CO2 concentration and acceptable noise level. Our results demonstrate the effectiveness of using sound classification as a trigger for ventilation control, with the CNN model achieving a good accuracy rate in sound recognition. This underscores the potential of integrating advanced machine learning techniques into building management systems to foster environments that adapt to the needs of their inhabitants automatically. The results of the present work are useful for improving the comfort of the occupants through dynamic ACUs adjustments based on acoustical situations.

Experimental and numerical research on a C-type heat exchanger in duct air conditioner under non-uniform airflow

The indoor unit of duct air conditioner typically employs an A-type heat exchanger (HX), but non-uniform airflow within the duct significantly degrades heat transfer performance. The current study proposes a C-type HX to accommodate the non-uniform airflow better. Experiments are conducted to compare the C-type and A-type HXs under varying conditions, including air volume flow rate, air velocity non-uniformity, inlet air temperature, and condensing temperature. Results indicate that as the non-uniformity of inlet air velocity increases, the heat transfer capacity of A-type HX decreases obviously. In contrast, the C-type is insensitive to the non-uniform air velocity distribution, which consistently outperforms the A-type in terms of heat transfer capacity throughout various operating conditions. Additionally, a numerical model is developed to compare the local parameters of the two HX types. The C-type demonstrates a more uniform outlet air temperature and exhibits a heat transfer capacity that is 19.1% higher than the A-type, while maintaining the identical heat transfer area and size parameters.

Energy efficient heating and ventilation of a factory hall by monitoring the indoor air climate

Background Different usage scenarios and design guidelines were considered when planning a factory building and its ventilation system. Accordingly, it often makes sense to analyze the actual operating conditions again during subsequent operations in order to optimally adapt the air supply to the respective conditions in terms of demand-responsive ventilation. The aim is to ensure good indoor air quality and thermal comfort while significantly reducing energy consumption. Methods For this purpose, in addition to the sensors in the building management system, approximately 120 wireless sensors were installed in the occupied areas to measure the air temperature, operating temperature, humidity, and CO2. In this way the spatial and temporal distributions of temperature, humidity, and CO2 in the hall were visualized and evaluated to reduce the volume flows of the ventilation systems. The recorded data and findings were used to optimize ventilation systems by gaining a deeper understanding of indoor air flow. Results As part of the investigation, a considerable reduction in the air volume flows and thus the required energy consumption of the air handling units was achieved while maintaining the same thermal comfort. It was shown that the temperature field and indoor air quality were not negatively affected by the change in the air volume flow over a wide range. Conclusions This was made possible by the well-designed ventilation system, which achieves a low-pulse, slightly stratified indoor airflow, and a structural envelope with very good thermal insulation.

A Study on the Influence of Mobile Fans on the Smoke Spreading Characteristics of Tunnel Fires

Mobile fans, as flexible and convenient new longitudinal ventilation and smoke extraction equipment for tunnels, demonstrate more significant effectiveness in an emergency response to tunnel fires compared to traditional smoke extraction methods. This study employs computational fluid dynamics simulation methods, selecting two fire scenarios to investigate the effects of fan inclined angles and fan airflow volumes on the longitudinal temperature distribution and smoke back-layering length in tunnels. The results indicate that when using mobile fans for longitudinal ventilation in tunnels, at a lower fan airflow volume, the temperature distribution along the longitudinal axis is nearly symmetrical. The fire source and the fan installed in the upstream are within a certain range, and it is more effective to use the horizontal angle for longitudinal ventilation. As the fan airflow volume increases, the back-layering length significantly decreases (210,000 m3/h &lt; V &lt; 270,000 m3/h). However, as the fan flow volume continues to increase (270,000 m3/h &lt; V &lt; 300,000 m3/h), the reduction in the back-layering length becomes less pronounced, the smoke spread distance of the latter is only 11% of that of the former. Therefore, selecting appropriate fan airflow volumes and fan inclined angles them can effectively enhance the performance of tunnel smoke extraction systems. Moreover, by comparing with traditional fans, we find that mobile fans provide an alternative effective strategy during firefighting by allowing adjustments in distance from the fire source and fan inclination angles, enhancing fire suppression effectiveness while reducing energy losses. The research findings can serve as a reference for tunnel fire prevention design.

Bionic microstructure design of cross flow fan for high aerodynamic and low noise performances

In this paper, a novel approach was introduced for cross flow fan design by incorporating bionic microstructures on the blade surface. Two types of bionic microstructures, riblet and convex hull, were constructed and studied to achieve high aerodynamic efficiency and low noise design. Numerical simulations were conducted to understand the influence of bionic microstructures on the fan’s aerodynamic and acoustic performance, and the impact of design parameters on these performances was investigated. After printing the bionic microstructure fan samples, the experimental tests were carried out. The flow field and sound field data of the fans with bionic microstructures and the original fan were compared. The results demonstrated that both riblet and convex hull microstructures effectively improved the fan’s aerodynamic performance by reducing turbulent kinetic energy on the blade surface. Additionally, the microstructures inhibited boundary layer separation on the suction surface of adjacent blades, which contributed to reducing vortex noise. However, the pressure gradient formed near the convex hull and the edge of the small-diameter riblet resulted in deterioration in the noise of the corresponding fan. By optimizing the diameter and spacing of the riblet microstructure, the best noise reduction performance was achieved for the riblet fan. The optimized fan showed a 5.3% increase in maximum air volume flow rate and a 2.4 dB(A) reduction in noise. Overall, the cross flow fan design method based on bionic microstructures has valuable application potential in improving the aerodynamic and acoustic performance of various rotating machinery.

A multiphase flow model of water droplets dielectrophoretic-induced air dehumidification phenomena

Air humidity in indoor spaces plays a critical role in human comfort and health. Dehumidification systems are used for building humidity controls, but they can take significant energy consumption, especially in geographic locations with high outdoor humidity and warm climates. Consequently, there is a growing demand for innovative dehumidification processes that consume minimal energy. Dielectrophoretic air dehumidification represents one such promising approach. However, it has not garnered significant attention due to the absence of engineering models and simulation tools capable of evaluating its performance and limitations at large-scale airflows. A new numerical multiphase CFD model, which is also experimentally validated, is developed in a customized Reacting Foam solver based on OpenFOAM® version 9. The newly developed model seeks to decrease substantial energy consumption and lower costs by leveraging the dielectrophoretic phenomenon to regulate moisture levels in the air. The solver integrates a hybrid Eulerian-Lagrangian framework to track the droplet's trajectory and growth rate while solving the continuum equations for the moist air. An electrospray produces electrically charged droplets, which grow during their in-flight trajectories as water vapor condenses onto their surfaces. The role of electrostatic forces in promoting vapor condensation within a high-gradient electrical field is investigated, and the dielectrophoretic vapor nucleation process on charged water droplets is discussed. The CFD model was validated against results from the literature and from proof-of-concept experiments conducted by the authors, which showed a 2 % air dehumidification with a single electrospray and airflow rate of 5 cubic feet per minute. The simulation results indicated that augmenting the number of electrically charged spray droplets increased the dehumidification of the air to 25 %. The initial mean droplet diameter, the orientation of the injector and relative humidity significantly influence the assessment of dehumidification. Scaling up this approach to larger airflow volumes is identified as a potential future research direction.

Experimental and simulation study of the effect of temperature and air supply on energy performance of a temperature-controlled ventilated double-layer Trombe wall

To study the energy performance of the temperature-controlled ventilated double-layer Trombe wall system (TCVD-TW) during winter and summer seasons, experiments and simulations were conducted in an experimental room in Qingdao where the system was installed. The experimental results demonstrate that the rooms equipped with this system exhibit favourable temperature performance in both winter and summer, with a positive impact on indoor humidity during the summer. The simulation results show that the performance of TCVD-TW is mainly affected by the supply air temperature, air volume flow rate, and indoor cooling and heating setpoints. For winter operating mode, the optimal supply air temperature setting should be 1°C higher than the heating setpoint. When the supply air temperature was set to 19℃(with a heating setpoint of 18 °C) and 21 °C (with a heating setpoint of 20 °C), the energy efficiency increased by 35.96 % and 32.38 %, respectively. When the supply air volume flow rate was set to 234 m3/h, the energy efficiency increased by 35.09 % (with a heating setpoint of 18 °C) and 30.27 % (with a heating setpoint of 20 °C), respectively. For summer operating mode, the optimal supply air temperature setting should be 1 °C lower than the cooling setpoint. When the supply air temperature was set to 25 °C (with a cooling setpoint of 26 °C), the energy efficiency improved by 33.62 %. When the supply air volume flow rate was set to 156 m3/h, the energy efficiency increased by 31.18 %. The experimental and simulation results of this study provide data support for the application of TCVD-TW.

A novel dual-wheel air-conditioning system operating strategy in different seasons

The application of solid desiccant air-conditioning systems can significantly reduce building energy consumption. Previous studies have focused on innovating the integration of solid desiccant air-conditioning systems (DACS) to improve dehumidification performance in summer. In this paper, a novel DACS is proposed, which can humidify the supply air in winter based on satisfying the dehumidification demands in summer. It can satisfy the year-round humidity requirements of domestic housing with significant savings in humidification costs. Furthermore, the operating strategy of the novel DACS is proposed, particularly for winter humidification conditions. It is adaptable as well as cost-effective compared to traditional operating strategies. The dehumidification/humidification capacity of the core component, polymer desiccant wheel, and the variation of temperature rise/temperature drop are investigated under different variations of parameters, including air temperature, air humidity, air volume flow rate, and wheel speed. The results show that with the increase of supply air mass flow from 0.6 kg/s to 1.9 kg/s, the power consumption of the system only increases by 9.5 kW. In winter, when the supply air temperature decreases from 8 °C to 1 °C, the power consumption increases by 7.2 kW, but in summer, when the temperature of the supply air increases by 7 °C, the power consumption of the system decreases by 7.0 kW. The power consumption of the system varies greatly when the humidity of the supply air is less than 17 g/kg, conversely, the power consumption of the system showed a negative trend. The analysis demonstrates the effective performance of the proposed system under varying climatic conditions.

Prediction of airflow temperature in coal mining face under the influence of multiple heat sources coupling: Numerical simulation and verification

With the development of coal resources to the deep, the mine heat damage has become increasingly serious. In this work, we proposed a comprehensive airflow temperature prediction model considering the coupling effect of multiple heat sources in coal mining face. The model was then discretized and a coupled solution simulator was developed independently. Finally, we conducted field test to verify the simulation results, and carried out a multi-factor sensitivity analysis affecting the thermal environment of coal mining face. The results show that:(i) The maximum relative error of prediction results is less than 4 %, which verifies the reliability of the prediction model. (ii) Heat dissipation from electrical equipment, surrounding rock and hot airflow leakage of gob area account for 43.8 %, 28.8 % and 17.4 % of the total heat load, which are the main causes of heat damage. (iii) The maximum airflow temperature in coal mining face increases in a parabolic trend with average advance speed. (iv) As the original rock temperature increases, the thermal environment of coal mining face deteriorates rapidly. (v) Cooling the inlet airflow or increasing the airflow volume can alleviate the high temperature problem. This research can provide guidance for the treatment of deep mine heat damage.

Impact of Intra-Phenotypic Nasal Vestibular Variation on Local Airflow Dynamics.

Many individuals with healthy normal nasal anatomy and function exhibit a prominent notch indentation at the junction of the ala and sidewall, specifically around the anterior-superior region of the unilateral nasal vestibule up to the internal nasal valve. This study evaluates the influence of various sizes of notched indentations at the anterior nasal airway on local airflow pattern. A retrospective study involving 25 healthy individuals, each exhibiting at least one unilateral notched indentation (40 total airways). Each individual's notched indentation was quantified after subject-specific three-dimensional nasal airway reconstruction from radiographic images. Computational fluid dynamics modeling was used to simulate nasal inspiratory airflow in each nasal airway at 15 L/min. Localized airflow distributions passing through the inferior, middle, and superior regions were calculated at 15 cross sections. Notched indentation size ranged 1.75-86.84 mm2 (average = 22.37 mm2). At the anterior airway, notched size significantly correlated with inferior airflow volume (R = 0.32, p = 0.04) but not in the middle (R = 0.21, p = 0.20) or superior (R = 0.06, p = 0.70) regions, whereas middle and superior regional resistance values were significantly correlated with notched size (middle: R = 0.54, p < 0.001; superior: R = 0.41, p = 0.009). Medially, resistance at the middle region significantly correlated with notched size (R = 0.56, p < 0.001). At the posterior airway, airflow distributions through the inferior, middle, and superior regions demonstrated weak correlation with notched size (inferior: R = 0.24, p = 0.14, middle: R = 0.24, p = 0.13; superior:R = 0.03, p = 0.83), whereas resistance was significantly correlated in the middle and inferior regions (middle: R = 0.56, p < 0.001;inferior: R = 0.43, p = 0.006). Anterior nasal airway notched indentation size had significantly stronger influence on localized airflow volume through the anterior-inferior airway than other regions of the nasal passage. N/A Laryngoscope, 2024.

Investigating the efficacy of foam-based dust particle capture for dust elimination in ore pass unloading: A similar experimental study

Dust pollution arising from ore unloading poses significant concerns for occupational health. The foam-based dust particle capture presents a promising solution for dust suppression due to enhanced wettability, broader dust capture area, and stronger adhesion. This study designed a similar experiment platform to investigate how unloading conditions and foam parameters influence airflow dynamics and dust migration. The results indicate that airflow intensity and dust source are pivotal factors affecting dust concentration. Additionally, applying foam at the unloading port on the first level or the ore bin proves effective. Foam-dust interaction duration and airflow intensity are crucial determinants of dust suppression efficacy. Furthermore, the study reveals that the foam has a dual effect on dust control: while it efficiently captures dust particles to mitigate pollution, it can also disrupt airflow unfavorably. This research offers valuable insights into optimizing the spatial arrangement and quantitative application parameters of foam equipment.

Effect of air volume flow rates on pyrolysis temperatures and flue gas compositions to control smoldering smoke generation

Smoking is an important process unit operation used for preservation, as well as flavor, color and texture modifications of many foods. Currently, wood pyrolysis temperatures in industrial smoke generators cannot be systematically adjusted, thus process outcomes can only be controlled by varying smoke exposure time and environmental conditions in the adjacent product chamber. In this study, we investigated changes in pyrolysis temperature and flue gas composition in a redesigned smoldering smoke generator in which air intake could be adjusted. Air volume flow rates were set at 5.6 m³/h, 7.7 m³/h, 10.2 m³/h, 12.1 m³/h and 15.7 m³/h. Ember bed temperatures and flue gas compositions were determined as a function of these rates. Mean ember bed temperatures were affected by both the air volume flow rate as well as the smoke generation time i.e. a higher volume flow rate and/or a longer smoke generation time increased mean ember bed temperatures. Increasing air volume flow rates also led to decreases in oxygen concentration and increases in carbon monoxide concentration. Furthermore, frequential supply of fresh wood chips from the storage container to the site of the pyrolysis led to an increase in oxygen concentration, which decreased again upon ignition. The results suggest that - contrary to current practice - smoke composition and amount may be altered by controlling the pyrolysis process itself, thereby providing new possibilities to modify quality attributes of smoked foods such as meat, seafood or dairy products.

Co-flotation of effluents from detergent and marble processing industries in Denver and dispersed air flotation systems

Suspended solids in the marble processing wastewater (MPWW) have the potential to pollute receiving media. Likewise, detergent production wastewater (DPWW) needs treatment prior to discharge as they include surfactants and others. Flotation and its modifications are common for separation purposes in various engineering solutions. To increase flotation performance by changing the surface tension some collector and frother chemicals, surfactants are utilized. Detergents are among important surfactants and they may act as both frother and collector in flotation. Therefore, the purpose of this study was to determine the effectiveness of DPWW in co-flotation with MPWW. Two effluents were mixed at varying ratios and dispersed air (DISP) and Denver (DEN) flotation co-treatment were applied to the mixtures. Volume ratio, time and air flow rate on treatment performance were investigated. Turbidity, solids, COD, phosphate removals were achieved at varying levels when the flotation was applied to the mixture. The highest treatment performance was achieved at 90%MPWW-10%DPWW mixture. 10 min flotation time and 2 L min−1 air flow rate for the DEN system, and 20 min and 6 L min−1 for the DISP system were recommended. Under these conditions turbidity, SS, COD, phosphate and alkalinity residuals (and removal efficiencies) were 2400 NTU(82%), 1720 mg.L−1(89%), 313.6 mg.L−1(10%), 20 mg.L−1(20%) and 600 mg.L−1CaCO3(92%) in the DEN system, respectively. Whereas, in the DISP system, under the same conditions, final values of 1880 NTU(86%), 1540 mg.L−1(91%), 262 mg.L−1(17%), 21 mg.L−1(20%) and 470 mg.L−1(94%) were obtained, respectively. The highest SludgeSS concentration increased up to 19300 mg.L−1 in the 90%–10% mixture. In all samples, dewaterable sludge was obtained. By this study, co-flotation of these two effluents was recommended. Within SDGs, this approach will replace frother chemical usage. The process performance can further be enhanced via flotation modifications and technology can be developed as further study.

Bionic noise reduction design of axial fan impeller

Fans are integral equipment widely employed in both industrial settings and daily life. However, a persistent challenge in fans design lies in the inherent conflict between aerodynamic performance and noise levels. Improving aerodynamic efficiency often results in a compromise of acoustic performance. To tackle this issue, we employed the bionic design method to craft a novel axial fan impeller featuring a bionic curved hub and bionic serrated leading edges. The impact of structural optimization on the aerodynamic and acoustic properties of the impeller, as well as the influence of optimization parameters on these properties, were systematically investigated through numerical simulations. The bionic impeller was then fabricated using 3D printing, and the aerodynamic and noise performance of the impeller were experimentally evaluated by integrating it into an external air conditioner. Comparison of the flow field and sound field data between the optimized and prototype impellers revealed noteworthy outcomes. The curved wall at the bionic hub’s tail effectively diminished the pressure gradient on the hub surface, directing the airflow toward the rear end of the hub. This design enhancement significantly reduced the turbulent area behind the prototype impeller’s hub. Additionally, under the appropriately designed, the bionic serrated structure could effectively reduce the contact area between the blade’s leading edge and incoming flow. This led to the dispersion of stress concentrations and the inhibition of strong turbulence generation. Notably, the experimental results indicated a 3.7% increase in air volume flow rate and a 2.3 dB reduction in noise for the optimized impeller compared to the prototype. This successful mitigation of the trade-off between aerodynamic performance and noise level underscores the effectiveness of our bionic design approach.

New Afton Mine diesel and battery electric load-haul-dump vehicle field test: Heat and dust contribution study

ABSTRACT The New Afton Mine and CanmetMINING conducted a joint study to better understand the environmental and performance impacts of battery- and diesel-powered mobile equipment. The two main objectives were to: (1) determine if battery electric and diesel load-haul-dump vehicles (LHDs) could perform equivalent duties, and (2) gather environmental information for determining the ventilation airflow requirements for battery-powered vehicles. The study focused on the effects of the LHDs on heat and dust generation and energy consumption in a ramp and in a production level. For the production environment tested, respirable crystalline silica concentrations were the driver to assess the battery-powered LHD airflow volume. The potential to reduce this volume was identified in the controlled air streams and conditions tested. However, it depended on the scenario and the dust generation and suppression mechanisms. One scenario evaluated environmental conditions under a reduced airflow (50% less than the diesel LHD). For this mine site, area contaminants levels exceeded limits; therefore, the potential for savings was less than 50%. For the scenarios tested, the battery electric and diesel LHDs were able to move equivalent amounts of material in a similar time.

Potential Regenerative Impact of Implementation of Cultural Vernacular Elements (Rowshan) in Jeddah, Saudi Arabia

The present study aims to explore rowshans as essential vernacular architectural elements in designing houses in very hot-dry climates such as Jeddah, Saudi Arabia, to determine their most significant effects on air movement, ventilation, and mitigating cooling loads. A comprehensive combination of building performance simulation and computational fluid dynamics (CFD) analysis was used to model a room with six different sizes of rectangular openings and quantify rowshans’ potential as passive elements in providing occupants with comfort and reducing energy use. Analysis of the passive element revealed the thermal performance and natural ventilation in single-family homes for the Jeddah climate, created by outdoor and indoor temperature, airspeed, and pressure differences in the room model, were improved, lowering sensation temperature for inhabitants’ comfort. The results highlight the beneficial effects of rowshans in lowering a house’s temperature during the daytime: from November to April, at noon, indoor air temperature (IAT) could reach a 15% to 22% reduction in the north orientation. The findings also show that rowshans with 5 × 5 cm opening grids can keep the air volume flow rate within an acceptable range and keep the room in the comfort zone range for 42.3% of hours annually, equal to 3704 h. An implication of these results is the possibility of establishing housing design criteria that can enhance efficiency and thermal comfort conditions, lower the cost of operations, provide occupants with satisfaction, and reduce emissions to regenerate the environment, leading to affordability and sustainability in the Jeddah region.

Experimental study of a novel in-tube spray evaporative condenser for geothermal power generation

To enhance the efficiency of medium to low-temperature geothermal power systems, we designed a novel in-tube spray evaporative condenser. Experimental setups for single-tube heat exchange were devised, examining both water-water and working fluid-water configurations. The study analyzed the impact of air volume and hot water flow rate on heat transfer. Economic comparisons were made in laboratory conditions among the novel evaporative condenser, traditional evaporative condenser, water-cooled condenser, and air-cooled condenser. Results indicated: (1) The novel evaporative condenser exhibited 1.5–1.7 times higher heat flux density and 2.0–2.7 times higher mass transfer coefficient, indicating superior heat transfer performance compared to the traditional one. (2) Variations in hot water flow rate within a certain range had minimal impact on condenser performance when the condenser size was constant, providing valuable insights for condenser selection and structural design. (3) Both total power and water consumption of the novel evaporative condenser were lower than the other three types. Its daily operating cost was approximately 3/4 of the traditional evaporative condenser, 1/2 of the air-cooled condenser, and 1/4 of the water-cooled condenser, demonstrating superior economic feasibility.