Natural Air Circulation Research Articles

Natural air circulation in an open circuit

Natural air circulation in an open circuit

Passive Design Strategy of Vertical Housing for Optimizing Energy Efficiency

Abstract Passive design is crucial for sustainable building, maximizing comfort while minimizing energy use and environmental impact. It optimizes heating, cooling, ventilation, and lighting through natural energy sources like sunlight and wind, promoting responsible energy consumption. As the Indonesian economy continues to grow, urbanization rates in major cities are rapidly increasing, leading to urban sprawl. One proposed solution is densification through vertical housing construction. However, a concern with vertical housing is the energy consumption for thermal and lighting comfort, particularly in Indonesia’s tropical climate. Passive design presents an effective energy efficient solution for optimizing comfort in vertical housing. This study explores various passive design strategies based on six basic principle. Firstly, it presents local climatic conditions. Then, it discusses lessons learned from traditional buildings and modern buildings. Finally, it introduces a passive design method for high-rise housing, focusing on six points: massing and orientation, building envelope, passive cooling, thermal mass storage, natural air circulation and daylighting. The study presents results and potential recommendations for passive design to optimize energy efficiency.

Analysis of flow heat transfer characteristics of helium-xenon gas mixtures during natural circulation

Helium-xenon(He-Xe) gas mixture is a commonly used cooling medium in fourth-generation advanced reactor systems. The thermal conductivity of a passive waste heat system is related to the safety and reliability of the reactor system. Therefore, it is crucial to explore the passive characteristics of the helium-xenon gas mixture. The passive waste heat removal characteristics of a helium-xenon gas mixture are influenced by the flow and heat transfer characteristics of the mixture. However, existing research on the flow and heat transfer characteristics of helium-xenon gas mixture mainly focuses on single tube bundles and plate bundles with fixed flow rates and high Reynolds numbers. However, existing research on the flow and heat transfer characteristics of the He-Xe mixtures mainly focuses on single tube bundles and plate bundles with fixed flow rates and high Reynolds numbers, and most empirical formulas apply to Reynolds numbers greater than 10000. However, the natural circulation flow rate under the influence of gravity varies with the variation of heating power, and in most operating conditions, the Reynolds number is less than 10000. Due to the lack of research on the convective heat transfer characteristics of the He-Xe mixtures at low Re, this paper investigates the flow and heat transfer characteristics of the He-Xe under natural circulation conditions. A three-dimensional model of the natural circulation circuit was established using numerical calculation methods. Comparing the numerical simulation results of natural air circulation with empirical formulas, it was found that the error was less than 20 %. This proves that the SST k-ω turbulence model can be used to study the flow and heat transfer characteristics of He-Xe gas mixtures in natural circulation. On this basis, natural cycle numerical simulations of He-Xe mixtures with different mixing ratios were carried out at a heat flux of 5000 W/m2, as well as natural cycle numerical simulations of 40 g/mol He-Xe gas mixture at different heating powers, to study the effects of heating power and He-Xe mixing ratio on the natural cycle heat transfer characteristics of the He-Xe gas mixture. The existing He-Xe gas mixture flow heat transfer equation was modified, and the error of the modified Nu empirical equation was less than 12 %, which can be used for the development of the passive waste heat export system program for subsequent He-Xe gas-cooled fast reactors.

Openings As an Important Aspect of Traditional Market Design Font

Traditional markets are known as one of the pillars of people’s economic state, and because of that, they need to be developed properly. Despite that, traditional markets nowadays have a negative stigma which is dirty and smelly. To increase the interest of residents, many factors can be used such as adjusting and improving traditional market facilities. Design elements can help in solving this problem by adding openings and adjusting market structure modules. This paper aims to provide more information about the effect of market openings and modules on air circulation (odor) in the market. The method used in this research is a literature study, namely by collecting data related to solutions to counteract the smelly market through articles, journals, and books. The existence of an opening is to provide natural air circulation into a room, also the sunlight helps eradicate bacteria inside the humid room. The arrangement of the modules is also important so the odor of each segment does not mix. The existence of traditional markets must be maintained and developed so that it is necessary to overcome the bad smell in the current market because it can affect and have an impact on the interest of visitors to come to traditional markets.

SOCIALIZATION OF THERMAL COMFORT STANDARDS AT SMKN 4 SOUTH TANGERANG

Vocational High School (SMK) is a formal education unit that provides education that prepares students to work in specific fields. Students can continue their vocational education after completing their education at the junior high school level. SMK Negeri 4 South Tangerang is one of the 4th Vocational High Schools in the City of South Tangerang, specializing in Building Modeling and Information Design, Health Services, Animation, and Visual Communication Design. SMKN 4 South Tangerang is located on Jalan Sumatra-Tidore, Jombang Village, Ciputat District, South Tangerang City, Banten Province, with a land area of 4,562 m2. Currently, SMK Negeri 4 South Tangerang uses a natural air circulation system with openings in each class; then, each class uses a fan for artificial air circulation. There are four types of building comfort: thermal comfort, space comfort, and audio comfort. Space comfort is related to the comfort of movement space and relationships between spaces. Meanwhile, thermal comfort is an essential part of building comfort because room temperature influences the feeling of comfort. This is because every human being has sensors on their skin that work when there are hot or cold temperatures. Thermal comfort conditions that comply with standards will help the teaching and learning process be streamlined at SMK Negeri 4 South Tangerang. So that SMK Negeri 4 South Tangerang has thermal comfort that meets standards, Budi Luhur University organizes Community Service activities to socialize the achievement of thermal comfort at SMK Negeri 4 South Tangerang. The method of implementing activities uses the concept of Problem Solving. At the same time, the Problem-Solving concept uses input stages, problem-solving processes, and output. The aim of socializing the achievement of thermal comfort is so that the management of SMK Negeri 4 South Tangerang knows how to achieve thermal comfort standards so that students at the School are comfortable when carrying out the teaching process.

Theoretical study of a double-slope solar still with solar air heater condenser

Despite their limited water production and efficiency, double-slope solar stills are an appropriate solution for water scarcity in hot arid regions. Numerous studies have focused on enhancing the effectiveness of double-slope solar stills. In this context, this study introduces a double-slope solar with a solar air heater condenser (DSSS-SAHC). The back cover of a conventional double-slope solar still was replaced by a glass air heater in order to recover the still’s thermal losses in heating air. The transient performance of the DSSS-SAHC was investigated numerically under real weather conditions and compared to the performance of a conventional double-slope solar still (CDSSS) with the same aspects. The impact of various weather and operation factors on the DSSS-SAHC performance was investigated at air flows of 0.01 and 0.1 kg/s to account for both natural and forced air circulation, respectively. The results revealed an increase of about 15% and 6% in the thermal efficiency of the DSSS-SAHC over that of the CDSSS, respectively, at air flows of 0.1 and 0.01 kg/s despite the DSSS-SAHC distillate was insignificantly greater than that of the CDSSS at both air flows. In addition, the water distillate of the DSSS-SAHC increased as the solar irradiance increased, the ambient wind and ambient temperature had contrary effects on the efficiency, and the initial saline water level had a negligible impact on the overall performance

Improvement in the environmental, exergy, energy, and economic performance of hemicylindrical solar still integrated with a built in active condenser: Experimental investigation

ABSTRACT In this paper, an experimental study is performed to investigate the effect of utilizing an internal condenser (IC) on augmenting the performance of a hemicylindrical type solar still (HSS). The proposed SS body is divided by a metal basin into two chambers; the upper chamber for evaporation and the bottom for condensation and located on the under of the basin absorber. Salt water is heated by solar radiation and then evaporated. Some of the produced vapor is condensed on the surface transparent cover, while the rest is naturally circulated to the condensation chamber to be condensed there. Hence, the novelty in the current work is utilizing the IC with natural air circulation in HSS instead of forced circulation and evaluate its effects on the thermal, thermodynamic, economic, and environmental performance based on energy, exergy, exergoeconomic (EXC), enviroeconomic (ENC), exergoenvironmental (EXE), and exergoenviroeconomic (EEC) parameters. For comparison, the traditional SS without an IC (HSS-C) is also tested. Depending on energy, exergy, cost, EXC, EXE, and EEC, the modified HSS with an IC (HSS-M) demonstrated outstanding performance. Comparing HSS-M to HSS-C, the daily water yield is increased by roughly 99.9%, while costs have decreased by 46.6%. Utilizing an IC increases the energy and exergy efficiency of HSS-C by around 60.4 and 51.9%, respectively. Based on energy and exergy approaches, the CO2 net emissions reduced annually for HSS-M by approximately 104.9%. The use of ICs has been successful in improving the energy, efficiency, economic, and environmental performance of HSS.

Numerical investigations on roof ventilator turbine performance characteristics using ANSYS

Rooftop wind turbine ventilators are natural air circulation systems that employ a rotating blade to remove stale air from a building, improving the indoor air quality and saving money in the process. The effectiveness of a roof ventilator turbine depends heavily on its construction. By varying the diameter of the turbine blades (500, 670, and 690 mm), this CFD study modeled and examined three distinct designs for wind-driven ventilation devices. This numerical analysis was further developed to compute the presentation of a rotating ventilator by analyzing the pressure, turbulence kinetic energy, and velocity of the airflow related with the ventilator at variant designs. To investigate the viability of a numerical approach to modeling the many aspects of a ventilator flow, a computational fluid dynamics (CFD) analysis was conducted utilizing the conventional k- turbulence model with the multiple reference frame meshing method. The proposed design of a 690 mm ventilator blade for a rooftop turbine was found to perform better than two alternative designs using computational fluid dynamics (500 and 670 mm turbine blade diameter). The trend lines appear to be in virtuous contract with formerly available data, signifying that mathematical modelling could be a useful and cost-efficient tool for the design, growth, and performance evaluation of a wind-driven rotational ventilation system in the future.

Design of a Multi-Tubular Catalytic Reactor Assisted by CFD Based on Free-Convection Heat-Management for Decentralised Synthetic Methane Production

A simple reactor design for the conversion of CO2 methanation into synthetic methane based on free convection is an interesting option for small-scale, decentralised locations. In this work, we present a heat-management design of a multi-tubular reactor assisted by CFD (Ansys Fluent®) as an interesting tool for scaling-up laboratory reactor designs. The simulation results pointed out that the scale-up of an individual reactive channel (d = 1/4′, H = 300 mm) through a hexagonal-shaped distribution of 23 reactive channels separated by 40 mm allows to obtain a suitable decreasing temperature profile (T = 487–230 °C) for the reaction using natural convection cooling. The resulting heat-management configuration was composed of three zones: (i) preheating of the reactants up to 230 °C, followed by (ii) a free-convection zone (1 m/s air flow) in the first reactor section (0–25 mm) to limit overheating and, thus, catalyst deactivation, followed by (iii) an isolation zone in the main reactor section (25–300 mm) to guarantee a proper reactor temperature and favourable kinetics. The evaluation of the geometry, reactive channel separation, and a simple heat-management strategy by CFD indicated that the implementation of an intensive reactor cooling system could be omitted with natural air circulation.

MODELING STUDY OF NATURAL AIR CIRCULATION IN HOTEL & RESORT BUILDING

The planning and design of a Hotel & Resort should be in accordance with the climate and location of the construction. In Indonesia, especially in areas that have cool air and are far from air pollution and noise pollution, they have a tropical climate, so Tropical Architecture is very suitable for planning and designing Hotels & Resorts, but it is possible to plan and design Hotels & Resorts with other architectural characteristics. Modeling studies can also be called modeling design and information about buildings, which is a field of science that examines development planning, development implementation, and maintaining and repairing if there is damage in a building. Activities from these fields of science are studying design drawings of houses, offices, buildings, and so on. In addition, this field of science does not only study building design, but this field of science will learn how to calculate the cost budget plan which is often referred to as RAB. Air circulation modeling has several sub-specifics, namely Planning Plan, building view, section view, Air Flow Scheme, and air circulation calculation. The building modeling method here uses an application called Autocad and SketchUp, then for the calculation of the natural air circulation using the ACPH (Hourly Air Exchange System) method. . Building 1 has a building area of ​​approximately 1486.7 M2 2 floors, building 2 has a building area of ​​461 M2 1 floor, and the hotel room area has a building area of ​​940.56 M2.

Development of analytical models for the natural circulation behavior of a full-scale PWR fuel assembly

During a loss-of-coolant accident in spent fuel pools, the fuel assembly will be exposed to the air environment and decay heat will be removed through the natural circulation of air. In this study, the Darcy-Forchheimer model was revised based on experiment to predict the pressure drop of the fuel assembly. Based on the ideal gas hypothesis, this paper also established analytical prediction models to estimate the natural circulation flow rate and the maximum cladding temperature of the fuel assembly. The model can accurately prediction of the flow rate of the fuel assembly under different heating powers. Through this model, it is found that with the increase of heating power, the natural circulation flow of air first increases and then decreases, and reaches the maximum when the power is about 2000 W. Meanwhile, lowering the environment temperature can significantly reduce the maximum cladding temperature of the fuel assembly.

Experimental study on the natural circulation behavior of a full-scale PWR fuel assembly

During a loss-of-coolant accident in spent fuel pools, the fuel assembly will be exposed to the air environment and decay heat will be removed through the natural circulation of air. There are few experimental studies on the natural circulation behavior in the spent fuel pool. In this study, a natural circulation experiment in a full-size PWR fuel assembly was carried out by replacing the fuel rods with electrical heating rods. The temperature distributions at eight different heights as well as air flow rate were obtained during the heating-up process of the fuel assembly. When the temperature difference between the fuel assembly and the environment is less than 150 °C, the flow rate increases as the temperature difference increase. But after the temperature difference exceeds 150 °C, the flow rate no longer changes with the temperature difference. The results of this study can be used to verify the system codes and CFD models.

Investigation into the effect of changing the size of the air quality and stream to the trombe wall for two different arrangements of rectangular blocks of phase change material in this wall

This paper transiently simulates a room with a Trombe wall on the side of the room. For this, COMSOL software has been used for simulation and numerical analysis. The wall consists of 4 rectangular blocks of PMC and 4 cement blocks with similar dimensions. The arrangement of PMC blocks and cement blocks is one in between. By moving the cement block and PCM block, two arrangements were obtained, both of which were analyzed. Also, the dimensions of air inlet and outlet between 10 and 30 cm have been changed and their effect on PCM freezing time has been studied. Finally, the freezing stages of PCM during the night for different hours of sunset have been studied. Also, the temperature and air velocity counters in the room along with the temperature and the volume fraction of PCM in the wall have been analyzed. The results of this study showed that the use of PCM causes air flow in the room for more hours during the night, so that natural air circulation can be used for both arrangement of cement blocks and PCM for up to 12 h. Also, increasing the dimensions of the inlet has caused the air velocity in the room to increase and the outlet temperature of the wall to decrease.

Analysis of Energy Management and Battery Sizing in an Off‐Grid Hybrid Solar Thermoelectric Generation System

Herein, the main aim is to analyze the idea of utilizing the thermal energy generated during the operation of a solar photovoltaic panel. The rise in temperature of the solar panels and the surrounding environment results in the reduction of the generated energy and ultimately the efficiency of solar panels. This thermal energy can be utilized to generate electrical energy by installing thermoelectric generators at the backside of the solar panel. The electrical energy generated through a thermoelectric generator depends on the temperature difference at its surface, which could be formed through any cooling mechanism such as natural air or cold water circulation. The electrical energy generated from the solar panels and thermoelectric generator can be integrated as a hybrid source, resulting in an enhancement of the overall efficiency of the system. On the other hand, designing a proper energy storage mechanism can enhance the efficiency and overall sustainability of the proposed idea. The results show that in doing so, not only does the solar panel temperature decrease resulting in the increase of its efficiency but utilizing the thermal losses by the hybrid solar thermoelectric generation system can enhance the energy generation up to 31.89% at a temperature difference of 34.4 °C.

Numerical simulation of natural ventilation with passive cooling by diagonal solar chimneys and windcatcher and water spray system in a hot and dry climate

The overuse of fossil fuels has become a major challenge in recent decades. Since mechanical ventilation systems are responsible for the largest proportion of the energy usage in the buildings, this study aims to come up with a green initiative for resolving the dire consequences of energy consumption. Here, for the first time, we work on an approach in which we aim to assess and enhance the evaporative cooling rate of a passive method during a summer day in a multi-story building in a hot and dry climate. In this regard, the windcatcher is coupled with three solar chimneys, and a water spray system (WSS) which is located at the entrance of the windcatcher to decrease the temperature and raise the humidity of the air entering each floor. A combination of wind-catcher, solar chimney, and water spray system is adopted to provide natural air circulation in the absence of wind. Indeed, we employ Radiation, Turbulent, and Discrete Phase Models to simulate the proposed system by CFD. The effect of different variables such as temperature, droplet diameter, and thermal comfort factors are studied. Temperature, velocity, and other airflow profiles are analyzed using ANSYS FLUENT software. The study highlighted that adding WSS leads to a roughly 6–12 °C reduction in the temperature; moreover, relative humidity will rise by 80% on the third floor. Accordingly, adding WSS can improve the system’s efficiency and satisfy the thermal comfort conditions in the absence of wind.

Energy-saving performance of respiration-type double-layer glass curtain wall system in different climate zones of China: Experiment and simulation

The development of energy-saving technologies for buildings is an important means of achieving carbon neutrality. The respiration-type double-layer glass curtain wall (RDGCW) is a kind of enclosure structure with natural air circulation and a shading function. The RDGCW provides energy saving, and it is being widely promoted and used in China. However, there is still a lack of relevant research on the energy-saving effects and operating strategies of the RDGCW throughout the year. In response, this paper describes experimental evaluation and numerical simulation. First, the energy-saving effects in an office building using an RDGCW in Tianjin during the winter were studied experimentally, and the real-time temperature changes in the RDGCW and the room were measured with high accuracy under different operating strategies. Second, because the temperature distribution and energy consumption in a room is affected by the air flow in the RDGCW and by outdoor meteorological parameters in a complex manner, this investigation developed a coupled model on the basis of TRNSYS and CONTAM. The simulation results were in good agreement with the experimental results. Third, the verified model was used to evaluate the annual energy-saving effects of the RDGCW under dynamic outdoor meteorological conditions in Tianjin. When the optimal operating strategy was adopted, the energy-saving effect of the RDGCW in comparison with single skin façade (SSF) reached 32.8% under summer conditions and 38.3% under winter conditions. Finally, the RDGCW system in typical cities (Changchun, Shanghai, Guangzhou, Kunming and Tianjin) in five climate zones in China was simulated for the whole year. Under the optimal strategy, the RDGCW achieved good energy-saving effects. The energy saving was 27.7–49.2% in summer and 25.6–46% in winter, in comparison with SSF.

Effects of meteorological conditions on the air quality in deep open - pit mines in Vietnam

Air quality in open - pit mines is the big concern relating to the occupational safety and healthy, as well as the surrounding environment. In the past years, management of the air quality in open - pit mines is challenge due to the limit of science and technology in the assessment of the effects of meteorological conditions and toxics in open - pit mines. Therefore, this study assessed the effects of meteorological conditions on the air quality in deep open - pit mines. The air velocity distribution and the dispersal mechanism of the air quality were evaluated at the Coc Sau open - pit coal mine (Vietnam) based on the measured and simulated datasets. Two fixed stations were set up in the ground to monitor the wind direction, wind speed and the temperature to evaluate the stable of the actual ozone layer based on the Pasquill ozone layer. The datasets were also used to analysis and 3D simulate to understand the air pollution mechanism in the Coc Sau open - pit coal mine. On the other hand, the change of the temperature in vertical was measured to determine the to determine the existence of a temperature inversion layer. It is considered as the main reason for the air quality reduction and the natural air circulation in deep open - pit mines. The findings indicated the existence of the temperature inversion layer and they are useful for proposing the artificial ventilation in deep open - pit mine, aiming to improve the air quality in open - pit mines. The 3D simulations also revealed that the high dust and gas concentrations in open - pit mines are due to the stable of the ozone layer.

Impacts of adding porous media on performance of double-pass solar air heater under natural and forced air circulation processes

This paper presents an experimental work on two trapezoidal double-pass solar air heaters (DPSAH) having double glass covers under natural and forced air circulation conditions to investigate their performances by adding packed beds above the absorber surface on one them for target of comparison. The DPSAH-1 has been operated with adding porous medium, whereas DPSAH-2 has been operated without adding porous medium. Experiments for each model have been performed in winter and compared under identical conditions. The results demonstrate that DPSAH-1 considerably enhances the system performance as compared to DPSAH-2. Results also indicate that the higher efficiency has been obtained when the systems are operated under natural convection. The peak efficiencies of DPSAH-1 and DPSAH-2 have been obtained equal to 87% and 82% for natural convection case and 81% and 67% for forced convection case for lower air mass flowrate, respectively. A considerable temperature difference has been found with natural process as compared to forced process. The advancement in performance of DPSAH-1 confirms that the adding porous medium and types of air circulation have considerable impact on heat transfer rate. Therefore, it can be concluded that DPSAH-1 is better than DPSAH-2, particularly for forced convection case including the applications that needs high temperatures and vice-verse.

A Study of Concept Design Massing Generator for Urban Houses in Jakarta

This paper presents the study of application massing configuration in typical urban houses in Jakarta. The study is aimed to present architectural project examples by architectural firm Studio Arsitektropis based on operative and conditional design strategies. The results showed that the operative and conditional design strategies could facilitate and become a quick design tools to produce the massing design concept, which emphasizes the sustainable aspect of natural lighting and air circulation; stack effect ventilation. The steps of study are as follows: (1) to study spatial verbs of massing design concept, (2) to study conditional design of architectural elements, and (3) to apply these studies into the conceptual design process within the practice of Studio Arsitektropis housing works in Jakarta.

СИСТЕМА ОХЛАЖДЕНИЯ ИМПУЛЬСНОГО РЕАКТОРА ПЕРИОДИЧЕСКОГО ДЕЙСТВИЯ

The paper proposes the configuration and composition equipment of the cooling system of the designed periodic pulsed reactor (PPR) of high power. The special features of the PPR are a small flow section, a large heating of the coolant in the power pulse and the impossibility of useful use of thermal energy in the periodic mode of operation. Liquid lithium is proposed as a coolant and heat is discharged through air heat exchangers (AHE). The goal was to achieve compactness and low power consumption, the ability to work with frequent stops and optimize the operation of equipment in pulse modes. For this purpose, high-temperature AHE with a small heat exchange surface and forced air cooling are used, the circulation circuit is divided into two parts - the reactor circuit and the AHE circuit with two circulation pumps and a common drain tank. The separation of the circuit allows to independently perform the operations of starting, stopping and heating the circuits in a periodic mode. The drain tank limits the composition of the equipment exposed to temperature pulses. Numerical studies of the temperature regime of the coolant in the equipment of the PDR cooling system are carried out. The calculations were performed using the TURBOFLOW code in two-dimensional terms for all the main elements of the equipment. Quasi-stationary (nominal and partial power levels) and pulse modes of operation are considered. Calculated characteristics for forced and natural air circulation are obtained. The limits of the air circulation modes under the conditions of non-freezing of the coolant are determined. The obtained values of the maximum temperatures of the coolant: in the pulsed mode is 750 °C, in the quasi-stationary mode - 490 °C with an average power of 15 MW, air flow of 150 m3/s and the size of the AHE in the plan of 5×5 m, 100 panels of 1.08×0.025×5 m.