Ventilation And Air Conditioning Research Articles

Characteristics, sources, and improvement measures regarding fine particulate matter in subway station office and the VAC system.

In order to study the characteristics and transport path of PM2.5 in the subway station office, three different types of typical subway station were selected for sampling and analysis. The PM2.5 of mechanical air duct and VAC (ventilation and air conditioning system) were tested simultaneously. Both the particulate matter in the station office and VAC exhibit highly enriched characteristics of metal elements. The mass balance equation with elemental Fe as the tracer element is established firstly in subway station, and the transport path of PM2.5 in the work area is revealed: if the work area is obviously under positive pressure compared to the station hall, metal-enriched fine particles come from the VAC system; otherwise, the particles come both from the VAC system and air infiltration from the station hall. The contribution of air infiltration to metal-enriched fine particles can reach 50%. Finally, following an investigation into the source of fine particles in the office, the measures to improve air quality are proposed and validated.

Multi-objective optimization of a CO2/H2O capture-based ventilation and air conditioning system

Developing energy-efficient ventilation and air-conditioning (VAC) strategies is pivotal for achieving green buildings’ triple merits of high indoor air quality (IAQ), low CO2 emission, and low energy consumption. While adsorption-based carbon capture technologies show promising potential in improving IAQ and reducing AC energy consumption by directly removing excess CO2/H2O and recirculating post-captured air in buildings, current studies lack in-depth investigation into simultaneously maximizing CO2 removal capacity and minimizing AC energy consumption. This trade-off, hindering the broad application of this technology, is rendered by the intricate interplay between indoor conditions, system configuration, and more importantly, the adsorbent materials. To circumvent this trade-off, this study proposes an NSGA-II-based multi-objective optimization model on a solar-driven CO2/H2O capture-based VAC system for optimizing its techno-energetic performances. This analysis maps the green buildings’ merits into five constrained objectives and fully optimizes them by considering a wide spectrum of decision parameters. This analysis automatically optimized the trade-off between conflicting objectives for both studied adsorbents to various extents. While maintaining the same IAQ level, a 74% and 59% improvement in maximal captured CO2 mass can be achieved for Mg-MOF-74 and Zeolite13X. Compared with Mg-MOF-74, Zeolites 13X performed 55% worse in maximal CO2 removal, but 82% better in maximal energy-saving potential due to higher cyclability, stability, and lower specific energy consumption. Additionally, the proposed multi-objective optimization framework could be applied to other adsorbent materials and capture methods to guide the optimal design of CO2/H2O capture-based VAC systems for green building development.

Heating, Ventilation and Air Conditioning Design for Commercial Complex Buildings: Theory and Method Based on Inverse Problem

Scientific and technological progress and innovation help the design industry, which plays an important role in sustainable development. It willimprove the operation efficiency of enterprises and explore a blue sea forenterprise. In essence, design should be the process of deriving the optimalscheme from different schemes or imaginary scenes. Based on this, thispaper proposes an overall optimization method for Heating, Ventilation andAir Conditioning (HVAC) design. Compared with the traditional designmethod, under certain constraints, it can obtain the optimal design schemethat maximizes the value of the designed product. This study provides newinverse problem ideas and methods for HVAC designers, and providessolutions for enhancing the value of HVAC design products.

Extraction of key parameters and simplification of sub-system energy models using sensitivity analysis in subway stations

Energy consumption of subway stations has become a focus of scientific research. For energy modeling, complete coverage of inputs makes it difficult to collect information for large-scale engineering application. To this consideration, this study conducted sensitivity analysis (SA) to determine key inputs and simplify energy model of subway stations. Firstly, four commonly-used SA methods (PEAR, SPEA, Morris and Sobol) were compared. Secondly, according to sensitivity indices, key inputs were extracted for ventilation and air-conditioning (VAC), lighting (LIGHT) and vertical transport (TRANS) model. For VAC model, the most important factors are humidity and temperature of the outside air and mechanical fresh air volume, contributing 40%, 33% and 11% of the change on energy simulation results, respectively. For LIGHT model, lighting power density of the hall exerts the greatest impact, with 50% of the change. For TRANS model, key parameters include train departure density and number of passengers, contributing 45% and 32% of the change, respectively. These outcomes provide guidance for engineers in the field of energy-saving operation for subway stations. Eventually, simplified VAC and TRANS energy models were investigated. Results indicate that CV-RMSE for simplified models are within 7.6%. The simplification greatly reduces the workload of data collection and model simulation.

Analysis of energy-saving for ventilation and air-conditioning system of subway stations with platform screen doors

Under the background of rapid urbanization and carbon neutralization, energy-saving operation of subway stations has become a widespread concern in China. This study focused on energy-saving measures and potentials for Platform Screen Door (PSD) subway stations in various climates. To this end, theoretical-based white-box model was innovatively established and validated. Then Ventilation and Air-Conditioning (VAC) energy was extensively simulated to systematically analyze energy-saving potentials of five common measures, including mechanical fresh air supply, PSD airtightness, station temperature, Coefficient of Performance (COP) of chiller, Energy Efficiency Ratio (EER) of terminal equipment. Results show that operation measure with the greatest energy-saving potential is increasing air-conditioning temperature, with 16.9–21.0% of energy-saving potential. Besides, cancelling mechanical fresh air supply, improving COP of chiller, and improving EER of terminal equipment can bring about 11.6–20.3% of energy-savings for stations in different climate regions, whereas enhancing airtightness of PSD exerts the slightest impact on the VAC energy use, with merely 5% of energy-saving potential. Suggestions were proposed quantitatively according to effectiveness and priority of the measures, and economic benefits were discussed preliminarily. The outcomes of this study not only provide information support for governors to formulate specifications, but also provide reference for operators to take effective measures.

Energy benchmarking analysis of subway station with platform screen door system in China

The energy consumption of Ventilation and Air Conditioning (VAC) systems in subway stations has attracted much attention, aiming to figure out energy-saving potentials and improve energy efficiency. Benchmarking is a useful method to evaluate energy performance of VAC systems during the operational stage. This study describes the development of an energy benchmarking model for the analysis of VAC energy consumption in subway stations with platform screen door systems in a variety of climate regions in China. Firstly, the Constraint Value (CV) and Leading Value (LV) of VAC energy use were simulated using a validated theoretical energy model, which represent the “general” and “superior” level of the VAC energy use, respectively. Results show that, for the 2,520 simulated cases, CV ranges from 184 to 859 × 103 kWh/year and LV ranges from 178 to 529 × 103 kWh/year, with different ranges for cold, hot-summer cold-winter, and hot-summer warm-winter region. Next, the simulated values of CV and LV were applied to establish an energy benchmarking model using the ordinary least square approach. For each climate region, the regressive energy benchmarking models for CV and LV were established and validated by cross-validation. Results show that R2 are 0.753–0.903 and MBE of the test set are 2.1–7.1%, indicating a good fit for the regressive benchmarking models. In order to further test their application, the regressive models were then applied to existing subway stations. Finally, the impacts of service-related variables, i.e. number of passengers, train departure density, and tunnel length, on the CV and LV were discussed. The proposed energy benchmarking model and analysis provide a convenient and effective tool for operators and managers to evaluate VAC energy consumption status and assess energy-saving potentials for subway stations.

A high-fidelity building performance simulation test bed for the development and evaluation of advanced controls

We present an open-source building performance simulation test bed, the Advanced Controls Test Bed (ACTB), that interfaces high-fidelity Spawn of EnergyPlus building models, with advanced controllers implemented in Python. The ACTB leverages the Building Optimization Testing and Alfalfa platforms for managing simulations, providing an external clock, a representational state transfer (REST) application programming interface (API), and key performance indicators for evaluating the effectiveness of control strategies. The REST API allows the development of external controllers programmed in languages such as Python, which provides flexibility and a rich choice of scientific libraries for designing control sequences. We present three test cases based on the U.S. Department of Energy's Reference Small Office Building to demonstrate the ACTB's capabilities: (a) rule-based controls compliant with ASHRAE Guideline 36 control sequences; (b) an economic model predictive control implemented using do-mpc; and (c) a deep Q-network reinforcement learning agent implemented using OpenAI Gym. Abbreviations: ACTB: Advanced Controller Test Bed; AHU: Air Handling Unit; AI:Artificial Intelligence; API: Application Programming Interface; BEM: Building EnergyModeling; BSS: Best Subset Selection; DOE: Department of Energy; DQN: Deep-QNetwork; EKF: Extended Kalman Filter; FMI: Functional Mock-up Interface; FMU:Functional Mock-up Unit; FSS: Forward Stepwise Selection; HVAC: Heating; Ventilationand Air Conditioning; KPI: Key Performance Indicator; LTI: Linear Time-Invariant; MBL: Modelica Buildings Library; MHE: Moving Horizon Estimator; MPC: ModelPredictive Control; N4SID: Numerical Subspace State-Space System Identification; REST: Representational State Transfer; RL: Reinforcement Learning; ROM: Reducedorder model

Concentration profile and water level effect on the evaporation in the spent nuclear fuel storage pool using a diffusion approach

In the spent nuclear fuel storage pool (SFSP) of GA Siwabessy Multipurpose Reactor (GAS-MPR), there are three status of pool water level with unknown effect of water level on evaporation rate. This study aims to determine the effect of pool water level on the evaporation rate in the SFSP, so that it can be a consideration in minimizing the evaporation rate. A prediction of water evaporation rate can be explained as a diffusion model through a stagnant gas film. A numerical method, 4th order Runge-Kutta was used to describe the concentration profile of water and air over a SFSP column to the top of the pool. The effect of the water level can be explained then. The various distance of the water to the pool top at constant water temperature and constant air temperature shows a result that the evaporation rate is decreasing while the distance of the water to the pool top is increasing. The investigation results conclude that the closer of the liquid-water surface to the gas-air flow, increases the evaporation rate. This approach can be applied in a SFSP that has an abundant amount of water, the water temperature remained constant by operation of the water-cooling system, air temperature, pressure, and relative humidity remained constant as well by the operation of ventilation and air conditioning (VAC) system. Those constant conditions were stated as normal operation in SFSP of GAS-MPR. In the case of abnormal conditions such as the VAC not operating or the water-cooling system not operating, there will be dynamics of pool water and air temperatures which require further modeling research.

Radiation noise control of a 90° rectangular elbow in ventilation and air conditioning systems

The elbow noise is an important part of indoor radiated noise of ventilation and air conditioning (VAC) systems. A technique to reduce the radiated noise of the elbow by adding guide vane is proposed. The models of elbow with/without guide vane were established respectively. Based on the experimental verification, the influence of the guide vane on the flow field of the elbow and the indoor radiated sound field is analyzed. The radiated noise of the elbow was predicted by LES simulation and FW-H equation. The results show that after adding the guide vane, the maximum resistance loss of the elbow can be reduced by about 17%, and the radiation noise can also be significantly reduced in the frequency range of 10–1000 Hz. However, the local turbulent dissipation slightly increases in the elbow due to the guide vane, causing an increase in the peak sound pressure level in the low frequency range of 10–200 Hz. In addition, in the proper position of the guide vane, the influence of elbow radiated noise on standing, sitting and lying posture is also significantly reduced. The maximum radiated total sound pressure level at the design point is reduced by about 5 dB.

Sub-system energy model based on actual operation data for subway stations

With the continuous expansion of the subway scale, the amount of energy consumed by subway stations has become a great concern for both governments and researchers. Despite of enormous energy use, there is a lack of energy model to evaluate the actual energy performance and energy conservation potential of subway stations. This paper concentrates on the establishment of a sub-system energy model based on theoretical analysis and actual operation data, with the aim to evaluate the operational energy conservation potential of the subway stations. This sub-system model is composed of models for ventilation and air-conditioning (VAC) system, lighting system, vertical transport system and station devices. With the help of this model, the energy consumption of the station can be calculated by inputting several parameters which are easy to obtain in actual projects, such as train departure density, temperature and humidity of the indoor and outdoor air, passenger flow of the subway station, etc. The model is validated via the field test and ventilation simulation in a station located in Zhejiang Province, China. And then, the model is applied to evaluate the current operation condition and several energy-saving measurements of 6 subway stations. The most notable significance of this model is that it can calculate the energy consumption of each system using actual operation data. Therefore, it serves as an effective model to analyze the energy conservation potential of changing operation pattern or adopting energy-saving technologies, which gives guidance to the energy-saving retrofit in actual projects.

Energy Consumption of the VAC System for Subway Stations: A Model Based on Theoretical Analysis and its Engineering Application

With the continuous expansion of the subway scale, the amount of energy consumed by subway stations has become a concern, among which the energy consumption of ventilation and air-conditioning (VAC) system takes a large proportion. There are many former studies concentrated on this topic. However, the problems of previous studies are obvious, such as time-consuming and unclear practical meaning of the energy model. This study has proposed a model based on theoretical analysis and focused on the energy model of the VAC system for underground subway stations. The energy model consists of the model for the cooling load and the energy efficient ratio. In this model, basic station information and environmental parameters should be tested and inputted. Then with the help of simple simulation tools, Subway Thermal Environment Simulation Software (STESS), the energy consumption of the station can be fast estimated by the model proposed in this paper. This model can be applied to determine the energy-saving potential of changing operation pattern and adopting energy-saving technologies, which gives guidance to the energy-saving retrofit of the station.

Energy consumption of subway stations in China: Data and influencing factors

Subway transportation systems are in rapid development and energy consumption in subway stations is becoming more and more significant. The present paper aims to reveal the electricity consumption of subway stations for non-traction purpose, and data from 341 subway stations in 5 cities in different climate zones in China have been statistically integrated and analyzed. The results demonstrate that the average annual electricity consumption ranges 1.8–2.3 million kWh in underground non-transfer stations. Electricity consumption per unit floor area is taken as the benchmark to evaluate the energy performance with an annual average value of 131–144 kWh/m2 in each city. The VAC (ventilation and air conditioning) system and lighting system are found in dominant positions of the total electricity consumption, accounting for about 46% and 27% respectively in City A. Influencing factors of the energy consumption are also analyzed, including floor area, annual passengers, CDD (cooling degree days), service year, PSD (platform screen door) system, platform type and number of entrances. These factors are compared and classified into three categories according to the degree of influence on energy consumption. The current information provides references for understanding the energy consumption level and establishing energy consumption standards for subway stations.

A study of fresh air control in subway stations

This paper examines the energy consumption problems in the subway station Ventilation and Air-Conditioning (VAC) systems in a typical city, as well as identifying the fresh air-cooling load reduction as a key to energy savings. The two components of the fresh air in the stations, which are “mechanical fresh air” provided by VAC system and “unorganized fresh air” generated by piston effect, are analysed through network simulations and field measurements. The results indicate that the unorganized fresh air is sufficient to meet the demand, except for high-traffic times in the future phase. Based on the discussion, the current VAC systems in most part of China cannot sufficiently control the volume of mechanical fresh air. Accordingly, an improved system with the completely sealed fresh air damper and a matched fresh air controlling method is proposed, and the method is verified by field tests. The study informs the readers about the ways to achieve energy saving in subway stations through the control effective usage of the fresh air.

Implementation of Energy Efficiency Strategies in Cooling Towers—A Techno-Economic Analysis

This paper depicts the results of a detailed energy audit, analysis, and implementation of energy efficient operations and maintenance strategies in a large commercial mall in Kuwait. Initially, the cooling towers (CTs) operated only at high speed, and on a typical summer day, nearly one-fourth of the make-up water was used for self-cooling of air. The study based on measured data and analysis, for a period of one year, revealed that the use of variable frequency drive (VFD) could reduce the water wastage for self-cooling of air by as much as 75% and overall water consumption by 18.6% while keeping the cooling system performance at the design level. An optimization model was developed, suitable exclusively for arid climatic conditions. Implementation of various energy efficient operation and maintenance strategies (EEO&MS) with ventilation and air-conditioning (VAC), and lighting systems obtained an overall reduction of 9879 MWh/y, equivalent to a percentage reduction of 11.7% in the annual energy consumption and a 345 kW in peak power demand. The study estimated an economical benefit of 19,958 KD/y for the owners and to the Ministry of Electricity and Water, in addition to a considerable environmental benefit of deduction in CO2 emissions by 6990 t/y.

Numerical Simulation and Experimental Study of the Drag Reduction of 90° Elbows for Ventilation and Air Conditioning Tubes in An Arc Form

Ventilation and air conditioning (VAC) tubes and technologies have been widely applied in modern architecture. In tube systems, local drag generally accounts for 40% of the total drag losses. Thus, optimizing the existing system components is extremely important in improving energy utilization, saving energy, and reducing emissions. Among the local drag components of the systems, 90° elbows are essential. In this study, the drag reduction of 90° elbows in an arc form is numerically simulated and experimentally studied. Factors influencing drag losses are analyzed. Several optimal design schemes for such components are given, and the effect of drag reduction of various optimization schemes is verified by experiments.The optimized elbows can effectively reduce local drag opposite VAC tubes by 9%–10%.

Indoor Air Contaminant Adsorption By Palm Shell Activated Carbon Filter – A Proposed Study

Indoor air contaminant is a public issue. High Volatile Organic Compound (VOC), Carbon monoxide (CO), Carbon dioxide (CO 2 ), and particulate matter is becoming main issue that needs to solve. Therefore, this study focus on improving indoor air quality by using activated carbon (AC) for Ventilation and Air-Conditioning (VAC). It investigated because AC is widely explored but developing AC as a filter for VAC is not developed yet. The AC prepared by physical and chemical activation process and combination both of process and it was activated by H 3 PO 4 and NaOH. Characterization and analysis process are consists of water content, ash content, bulk density, adsorption capacity, iodine number and indoor air filtering analysis. Treated activated carbon potential in achieving higher surface area of the structure to the range of 950 to 1150 m 2 /g for gas phase application. The higher surface area will adsorb more air pollution. Maintained properties of activated carbon such as hardness, density, pore, extractable ash, particle size (12 by 40 mesh) and pH are becoming the main concern in achieving high quality of activated carbon.