Air Supply Angle Research Articles

Optimizing kitchen ventilation with an integrated stove air supply-exhaust system for reducing PM2.5 intake fraction and enhancing energy efficiency

Ensuring good ventilation is crucial for reducing the pollution caused by cooking activities in the indoor environment. Among them, fume exhaust devices as a vital component of kitchen ventilation, and their performance is particularly critical. Merely increasing the air volume of exhaust devices to remove fumes not only leads to the higher energy consumption of exhaust fans, but also has limited practical effect on reducing pollution. For improving the ventilation condition and reducing the energy consumption of supply and exhaust fan, a new ventilation system for kitchen with integrated stove air supply-exhaust (ISASE) was developed in this study. Firstly, the orthogonal experiment was utilized for arranging different combination schemes of five influencing factors, including the emission rate, exhaust flow, upper air supply angle, upper and lower air supply velocities. Then, the effect of ISASE in reducing the intake fraction of PM2.5 under each scheme was studied by using the computational fluid dynamics method. The energy consumption of this system under different ventilation schemes was investigated with on-site testing. Finally, performance-gaining rate was proposed by introducing intake fraction reduction rate and energy consumption growth rate to quantitatively evaluate the performance advantage of ISASE. Polynomial fitting was also used to explore the energy-saving effect of ISASE at high emission rate. The results showed that at low, medium, and high emission rates, the intake fraction of PM2.5 was reduced by 65.0%–85.2%. However, the energy consumption of ISASE merely increased by 7.4%–16.8% compared with traditional integrated stove without air supply conditions. Its maximum performance-gaining rate reached 0.49–0.66. The energy-saving rate of ISASE was 46.7% compared with traditional integrated stove without air supply when the same intake fraction was achieved at high emission rate. The practical schemes of ISASE at different emission rates were given in this study, which optimized the working performance of integrated stove and provided a useful reference for its innovative design.

Research on low energy joint optimization of dynamic thermal environment coupled with passenger cabin and air conditioning systems

This study establishes a model for the coupling of passenger compartment and air-conditioning systems. The model takes human thermal comfort as the evaluation index, which can achieve dynamic data exchange during the transient calculation process, and control the air-conditioning systems with the core goal of reducing energy consumption. The optimal air supply angle and air distribution ratio were analyzed using this model. When the external environment changes, the air supply parameters corresponding to the lowest energy consumption are analyzed based on the air conditioning system with optimal air supply angle and air distribution ratio. The results show that the best direct blowing position is the neck. When the air distribution ratio of the driver's left air outlet is 25 %, the overall thermal comfort value of the dummy is the best. The overall thermal comfort of the dummy was maintained at the optimal value with an air speed of 8 m/s for dynamic external environments, but this air speed was not the lowest energy consumption. Subsequently, under the premise of maintaining the comfort of the dummy, the fitted curves of the air supply speed that minimizes the energy consumption are obtained by comparing the energy consumption under different air supply speeds.

Improving kitchen thermal comfort in summer based on optimization of airflow distribution

To quantitatively analyze the comfort of kitchen environment, this paper presents a thermal comfort analysis method for kitchen with air-conditioned range hood. It corrects the deficiency in the original comfort formula involving humidity, thereby reasonably quantifying the impact of the cooling airflow from air-conditioning, including humidity, on kitchen thermal comfort. By adjusting the structural parameters of the air conditioning system, the airflow distribution in the kitchen space during summer has been optimized, thereby further enhancing its thermal comfort. This method employs Fluent analyses and its User-Defined Functions (UDF) to analyze the indoor flow field, temperature, humidity, and the distribution of PMV-PPD within the kitchen equipped with air-conditioned range hood. Additionally, experimental data are applied to validate the accuracy and effectiveness of the simulation model. The results indicate that under high temperature climate conditions in summer, air-conditioned range hood significantly enhances the thermal comfort of kitchen environment during cooking. Moreover, optimal thermal comfort for both the kitchen space and local respiratory area of the human body is achieved when the air supply angle is set at 45°, the air conditioning outlet flow rate is 5.5 m3/min and the air supply temperature is set at 21 °C. Compared to the initial operating conditions, Human thermal sensitivity weighted PMV decreased by 98.17 %, and the weighted PPD decreased by 82.07 %. This study provides valuable insights for the design and operation of air-conditioned range hoods, contributing to improved thermal comfort and energy efficiency in residential kitchens.

Field experiment and simulation of hot air curtain for cold protection in subway aisle in severe cold regions

Harbin Subway is the northernmost subway line in China. In winter, outdoor temperature can reach −37.7 °C. Cold protection has emerged as a critical priority for subway operations in the region. In this paper, taking the aisle of a typical island station in Harbin as the research object, long-term and short-term field experiment on the thermal environment of the aisle were carried out. The field test data of the station and the full-scale model were used to conduct numerical simulations on the effect of supply air temperature, speed, and angle on the aisle environment. The modified PET temperature scale and average power consumption during the operation of the hot air curtain were used to evaluated the cold protection solutions of the air curtain. The results revealed that the average temperature of the cross-sections in the aisle without cold protection measures dropped by 5.4 °C–6.3 °C from its initial level after the train left the station. Without increasing average power consumption, changing the supply air angle of hot air curtain can improve the thermal environment in the aisle. Considering the three aspects of cold protection effect, passenger thermal comfort and power consumption, this paper recommends that the cold protection solution for aisles with a length less than or equal to 76.7 m, L-shaped and similar layouts is 35 °C for the supply air temperature, 9 m/s for the wind speed, and the range of the difference between the supply air angle and the aisle inclination angle is 6° <θ-α < 11°.

Simulation analysis and optimization of containerized energy storage battery thermal management system

The air-cooling system is of great significance in the battery thermal management system because of its simple structure and low cost. This study analyses the thermal performance and optimizes the thermal management system of a 1540 kWh containerized energy storage battery system using CFD techniques. The study first explores the effects of different air supply angles on the heat transfer characteristics. Second, the evaluation indexes of heat removal efficiency, air exchange efficiency, temperature and velocity uniformity coefficient are used to select the optimal air supply angle by the Topsis method. Then, the return air vent position is optimized based on the optimal air supply angle, and the optimal solution is obtained. Research indicates that increasing the air supply angle enhances air mixing within the container and simultaneously decreases the battery pack surface temperature. With a 90° air supply angle, the maximum temperature reduces to 33.58 °C, a 19.52 % reduction compared to 30°. The temperature difference across each battery surface also drops by 16.02 % to 3.46 °C. Adjusting the position of the return air vent further improves temperature uniformity and air flow distribution within the battery compartment. When the air supply angle is 90° and the return air vent evenly distributed at Z = 0.85 m next to the fire door, an optimal uniform temperature distribution is achieved. This reduces the maximum surface temperature by 16.47 %, from 36.67 °C to 30.63 °C and decreases the average temperature difference to 3.0 °C, 21.4 % lower. Thus, the present method effectively enhances the performance of the containerized energy storage battery thermal management system.

Performance of local supply-exhaust ventilation around stove with numerical simulation in a residential kitchen

A large number of fine particulate matters (PM2.5) are generated during cooking, which have negative impacts on kitchen environment. This study proposed a novel ventilation strategy of local supply-exhaust ventilation around stove (LSEVAS) for improving air quality in a residential kitchen during cooking. Five factors affecting the performance of LSEVAS were explored with orthogonal design and computational fluid dynamics (CFD). Evaluation indexes including PM2.5 mass concentration in breathing zone (CB), capture efficiency (CE) of fume exhaust device and intake fraction (IF) of occupant were also analyzed. The performance of LSEVAS was also identified without air supply condition in kitchen in terms of these above evaluation indexes. Results show that the emission rate and exhaust air volume were the most significant factors, followed by the upside air supply angle, upside air supply speed and downside air supply speed. The CB in LSEVAS was reduced by 83%, 60% and 66% than without air supply condition under low, medium and high emission rates, respectively. The CE was improved by 1.8%, 13.9% and 14.5%, respectively. The IF value was decreased by one order of magnitude. Furthermore, with increasing of upside and downside air supply speed, the ability of air supply airflow in preventing the escape of PM2.5 became stronger, while the core concentration distribution of PM2.5 was gradually closer to breathing zone of occupant. It means that the novel local ventilation strategy proposed in this study is effective in improving cooking environment in the residential kitchen.

Optimization of Air Supply Conditions for Large Space Radiant Air Conditioning Based on Response Surface Analysis

In large spaces, the comfort control of radiant air conditioning systems still has deficiencies. Mainly reliant on traditional parameter control methods, the interaction effects of diverse operating conditions are not taken into account, and the control results are still in need of optimization. To improve indoor air conditioning comfort control and address gaps in existing research, the response surface analysis method combined with numerical simulation is applied to determine the optimal air supply conditions for large-space radiant air conditioning. With the real model as a reference, simulations are carried out in Airpak, selecting four factors: supply air temperature, supply air humidity, air supply volume, and air supply angle for the response surface design. Discussions on interaction effects are carried out based on the simulated results of various scheme designs, determining eight groups of air supply schemes with the highest comfort. The research concludes that the response surface analysis method, considering the interactive effects of impacting factors, can lead to the strategy of high comfort and reasonable air supply conditions. Additionally, a set of recommendations are proposed for future practical application and promotion.

Personalized kitchen air supply for reducing individual thermal discomfort and cooking pollution intake

High ambient temperature and cooking activities that produce pollutants and waste heat usually make the indoor air quality and thermal environment of residential kitchen unfavorable in summer. Personalized kitchen air supply (PKAS) could be applied to relieve the thermal discomfort and cooking pollution intake of cooking staff. This paper investigated a personalized air supply method of residential kitchen in summer. The residential kitchen was depicted in computational fluid dynamics simulation by realizable k-ε model and discrete ordinate radiation model to reflect the complex thermal characteristics of stove. Based on orthogonal analysis, exhaust rate, exhaust outlet baffle width, and supply air angle were significant factors affecting the concentration of pollutant in kitchen space, whereas exhaust rate and air supply rate were significant factors affecting the intake fraction. Single-factor analysis was further conducted to find better parameter configurations of PKAS for pollutant control. Then, thermal comfort experiments with and without air supply were carried out. When the air supply volume was 280 m³/h and the air supply temperature was 21 °C, the thermal discomfort of subjects can be effectively improved against an uncomfortable condition of 30 °C background temperature, 80 % relative humidity, and a localized heat source intensity of 4.5 kW. The result of this paper can provide valuable information to develop PKAS for better thermal discomfort improvement and cooking pollutants control.

Mitigation of airborne transmission of COVID virus between occupants in a confined room with an air purifier

This study evaluated the effect of ventilation rate and air supply angle of an air purifier using computational fluid dynamics to determine the dispersion of airborne COVID virus exhaled by an infected person. The risk of infection for an occupant was determined based on the virus concentration in the active area and accumulated particle dose within the breathing zone by varying the ventilation parameters. The air purifier was found to provide a local dilution and would block the development of an expiratory jet for a short time to reduce transmission risk. Compared to the case without an air purifier, the maximum reductions were 94.27% in the accumulated dose and 53.2% in the particle count concentration. In the breathing area, the larger air supply angle (90° &gt; 60° &gt; 30°) is better when the ventilation rate was 27.0 m3/h and 40.5 m3/h. Otherwise, 60° air supply angle is preferable where the ventilation rate was 54.0 m3/h. Assessing the results with the grey relational analysis revealed that the relational degree for particle count concentration was greater by varying the ventilation rate than by varying the air supply angle. However, the relational degree according to the accumulated dose was greater by varying the air supply angle than by increasing the ventilation rate. These findings may provide an important control strategy to effectively mitigate the risk of infection in a confined room by using an air purifier.

Distribution of benzene and formaldehyde in tractor cabin: Effects of components, ventilation conditions, and vent positions

Tractor cabin is a relatively closed microenvironment in which operator is exposed to various pollutants that can adversely affect human health. In this study, the distribution of benzene and formaldehyde inside tractor cabin was investigated using computational fluid dynamics (CFD) method and verifying its effectiveness with field measurements. The effects of pollution source, ventilation, and vent position on the distribution of pollutants were discussed by using the validated CFD model. The results indicated that the areas with high concentration of pollutants are mostly distributed in the corners, and the ceiling contributes the most to its emission. The concentration difference of benzene and formaldehyde in the driver’s breathing area can reach a maximum of 20% by adjusting the air supply angle. It can also be reduced by 3.9% and 4.3% for every 1 m s−1 increase in air supply speed when the airflow angle emitted from the vent was 90°. In the common vent locations, the vent arranged on the front ceiling has the best pollutant reduction effect. This study provided a reliable CFD simulation method for benzene and formaldehyde distribution, offered a theoretical basis for the selection of ventilation conditions and the design of internal layout in tractor cabins for improving air quality. It also suggested that then environment and air quality of non-road mobile machinery cabs should be paid more attention in the future.

Case Study: Impacts of Air-Conditioner Air Supply Strategy on Thermal Environment and Energy Consumption in Offices Using BES-CFD Co-Simulation.

Due to energy constraints and people's increasing requirements for indoor thermal comfort, improving energy efficiency while ensuring thermal comfort has become the focus of research in the design and operation of HVAC systems. This study took office rooms with few people occupying them in Wuhan as the research object. The EnergyPlus-Fluent co-simulation method was used to study the impact of 12 forms of air distribution on the thermal environment and air-conditioner energy consumption. The results indicate that 3 m/s supply air velocity and 45° supply air angle are more suitable for the case model in this study. The EnergyPlus-Fluent co-simulation method used in this paper provides a reference for the study of indoor environments in offices with few people occupying them.

The analysis and optimization of thermal sensation of train drivers under occupational thermal exposure.

Prolonged exposure of train drivers to thermal discomfort can lead to occupational safety and health (OSH) risks, causing physical and mental injuries. Traditional method of treating human skin as a wall surface fail to observe accurate skin temperature changes or obtain human thermal comfort that adapts to the thermal environment. This study employs the Stolwijk human thermal regulation model to investigate and optimize the thermal comfort of train drivers. To minimize the time-consuming design optimization, a pointer optimization algorithm based on radial basis function (RBF) approximation was utilized to optimize the train cab ventilation system design and enhance drivers' thermal comfort. The train driver thermal comfort model was developed using Star-CCM+ and 60 operating conditions were sampled using an Optimal Latin Hypercube Design (Opt LHD). We analyzed the effects of air supply temperature, air supply volume, air supply angle, solar radiation intensity and solar altitude angle on the local thermal sensation vote (LTSV) and overall thermal sensation vote (OTSV) of the train driver. Finally, the study obtained the optimal air supply parameters for the Heating Ventilation and Air Conditioning (HVAC) in the train cabin under extreme summer conditions, effectively improving the thermal comfort of the driver.

Differentiated Control of Large Spatial Environments: Air Curtain Grid System

Large public buildings (LPBs) are the main energy consumers in cities, and the air conditioning system contributes a large part. Supply air allocation by partition can avoid excessive regulation of the system. In spatially interconnected LPBs, thermal coupling relationships exist between different subzones. The convective heat transfer to the non-occupied zone increases the actual cooling/heating capacity of the air conditioning area. This paper applies the air curtain as an airflow barrier indoors, and the air curtain grid system (ACGS) is created by the combined operation of multiple air curtains, which aims to reduce the convective heat exchange between adjacent subzones. The computational fluid dynamics (CFD) model is established and simulated. The main conclusions are as follows: (1) For the scenarios addressed in this paper, the combination of a 60° diffuser air supply angle and 2 m/s air curtain velocity can reduce the convective load from the adjacent space by more than 50%. (2) It is recommended to install incomplete air curtains indoors, and a 50% air curtain coverage ratio can reduce 52% of the heat exchange. (3) The mathematical model of air infiltration/exfiltration under the combined operation of multiple air curtains is established and verified in ACGS. This paper provides a new approach to the air conditioning partition control of LPBs.

Thermal management research for a 2.5 MWh energy storage power station on airflow organization optimization and heat transfer influential characteristics

Most of the thermal management for the battery energy storage system (BESS) adopts air cooling with the air conditioning. However, the air-supply distance impacts the temperature uniformity. To improve the BESS temperature uniformity, this study analyzes a 2.5 MWh energy storage power station (ESPS) thermal management performance. It optimizes airflow organization with louver fins and simulates its heat transfer behavior. To improve the flow rate distribution along the airflow passage, the air-supply organization of louver fins for the overhead air conditioner is optimized. It indicates that the air-supply angle (A) for louver fins and the battery spacing (D) impacts greatly on BESS thermal management performance. The air supply optimal organization with the A of 90° and the D of 18mm was determined, of which the average temperature (TA) rise of the battery can be reduced by 18%, and the temperature difference (TD) is decreased by 23%. Furthermore, a multi-parametric sensitivity analysis is conducted, and the different heat-flow parameter influential sequence for the TA and TD are revealed. The air supply volume flow rate (L) and the air supply temperature (AST) has a significant effect on the TA reduction, and the AST shows significance on the TD decreasing. When AST is reduced to 290 K, the TA rise of batteries decreased by 71%. When the L is increased 10 times, the TA rise of batteries decreased by 227%. When the AST is decreased to 290 K, the TD is reduced by 39%. When the L for air supply is increased by 10 times, the TD will increase by 28%. In this research, the louver fins are firstly adopted for orifices air supply organization to improve thermal field uniformity for BESS.

Study on the Effect of Pressurized Air Supply Outlet Setting on the Effect of Anteroom Smoke Control

In the selection of smoke control system, the Technical standard for smoke management systems in buildings (GB51251-2017), Article 3.1.1, paragraph 2, makes strict requirements for the setting of mechanical pressurized air supply outlets in anterooms, in order to study the influence of different setting methods of supply outlets on the smoke control effect of anterooms, the wind speed of the anteroom doorway section and the smoke flow in the anteroom are researched for different settings of the location of outlet and air supply angle with the help of Pyrosim. The results show that the effect of anteroom smoke control is not only related to the wind speed of the doorway section, but also related to the air velocity distribution at each point of the doorway section; at the same time, the air supply angle also has some influence on it.

STUDY OF SELECTED BURNER PARAMETERS ON THE GAS-AIR MIXTURE COMBUSTION

The study of the combustion of a gas-air mixture using burners opens possibilities for further research, in which it is possible to modify the parameters of existing burners (geometry, method combustion air distribution, ...). Flame length can be influenced by changing some of the burner parameters to achieve the best possible conditions in the combustion chamber. The topic of the article is to study the effect of changing burner parameters on the length and nature of the flame in the combustion chamber. For this, an existing burner simulation model was modified. The properties of the proposed changes were investigated using the ANSYS simulation software. Simulation confirmed the suitability of the proposed system for reducing the flame length and intensifying the mixing of gaseous media. Also, the results show that the effect of changing the angle of combustion air supply along the longitudinal axis of the burner significantly affects the mixing of the fuel and, consequently, the nature of the flame with the combustion products.

Comparative analysis and parametric study of an innovative artificial air column ventilation mode in a high-speed railway station

With the rapid development of high-speed railways, the air distribution and thermal comfort in the waiting halls of high-speed railways have attracted more attention. In this study, three ventilation schemes (artificial column attached ventilation (ACAV), nozzle outlet air supply (NOAS), and artificial column attached ventilation with nozzle outlet air supply (AVNOAS)) were compared by applying numerical methods. Five evaluation indices which can objectively assess indoor airflow organization and thermal environment were used in this study. Under identical air volumes, the average air temperature of AVNOAS was 26.80 °C. Compared with ACAV and NOAS, the ADPI of AVNOAS was raised by 5.35% and 26.42% respectively, and the RWI of AVNOAS was smaller, indicating that AVNOAS should be recommended for application in the waiting halls of high-speed railways. To optimize the ventilation performance of AVNOAS, further studies were discussed in terms of the air-supply angle and the proportion of air volume distribution (PAVD). The thermal environment of Case 1–3 (θ = −15°) is better than those under other air-supply angles. When the PAVD of AVNOAS was 2:1, a better thermal environment was created in high-speed railway stations. The results of the present study intended to support the application of this innovative attached ventilation in high-speed railway stations.

Decision-making analysis of air supply strategies for high rack cold stores

The thermal performance of a high rack cold store is related to the quality of fresh fruit and vegetable preservation. As the complex air supply strategies, a comprehensive evaluation of the thermal and airflow performance needs more than one demand. Therefore, the Z-score method was used to evaluate the thermal and airflow performance of the high rack cold store in this paper. The Z-score considered the energy utilization coefficient, non-uniformity coefficient and Air Diffusion Performance Index (ADPI). Firstly, a numerical simulation model of a high rack cold store was developed and validated. The effects of air supply form, air supply angle and air supply velocity on thermal performance and flow properties were then investigated. The velocity, temperature and pressure distribution were analyzed. Based on the previous data, the air supply strategies of the high rack cold store were evaluated with the proposed Z-score method, and the results proved that it could be utilized as the multi-indicator comprehensive analysis method for the high rack cold store. The cooling effect and the thermal uniformity of the vertical wall attached ventilation was excellent in a high rack cold store. When the air supply angle is −90°, the high rack cold store has a more uniform and reasonable temperature field. Considering the energy consumption of fans, the optimal air supply velocity was 11.7 m·s−1. Those results could provide a reference for the design of air supply form in the high rack cold store.

Dust dispersion law and high-pressure air curtain control technology of crossheading during the process of ore unloading

In order to solve the problem of dust pollution in the crossheading caused by ore pass unloading, this paper studied the dust diffusion rule in the crossheading by numerical simulation, established the prediction model of dust concentration in the crossheading, proposed the high-pressure air curtain to control the dust pollution in the crossheading, and determined the dust control parameters of the high-pressure air curtain. The results show that the dust diffusion velocity in the horizontal direction is higher than that in the vertical direction; Discharge height and ore size have a great influence on the mean dust concentration in the crossheading, under the allowable conditions of mine production, the discharge height should be reduced and the ore size should be increased as much as possible; The Sparrow Search Algorithm (SSA)-Extreme Learning Machine (ELM) model can better predict the mean dust concentration in the crossheading of the numerical simulation results of this paper; The inclination of high-pressure air curtain decreases with the increase of air supply angle under the action of impact airflow. When the air supply speed and angle of the high-pressure air curtain are 35 m/s and 30° respectively, the dust removal efficiency of each section in the crossheading can reach 87.3%.

Performance analysis of air curtains on indoor environment and dehumidification energy consumption in a low humidity plant

ABSTRACT The purpose of this study is to evaluate the effect of air curtains on indoor environment and dehumidification energy consumption for different air supply angle and velocity. The numerical investigation is conducted in a low-humidity plant located in the atmospheric boundary layer. The standard k-epsilon turbulence model is used in the simulation study. The optimum air supply angle and velocity are evaluated based on temperature and humidity distribution. The simulation cases range in air supply angle from 0° to 20° and velocity from 6 m/s to 14 m/s, which is studied by means of orthogonal experiments. Simulation results show that air curtain can reduce the average indoor temperature of the plant by up to 3.9°C and reduce the average moisture content by up to 86.6%. The energy saving assessment of the dehumidification rotor system shows a parabolic variation in energy consumption with increasing air velocity at a certain air supply angle. The optimum energy consumption occurs in the range of 9–11 m/s for air supply velocity. When air supply velocity is over 11 m/s, the airflow exchange is enhanced by air curtain at the plant opening, resulting in higher energy consumption from air leakage for dehumidification.