Mechanical Ventilation And Air-conditioning Research Articles

Multiphysical design for optimised ventilation and noise attenuation in ducts: an approach using metamaterials

Noise generation and propagation through mechanical ventilation and air conditioning (MVAC) ducts have been increasingly investigated since commercial solutions allow sensible noise attenuation while reducing the duct section. So, a commercial silencer forces the MVAC power to rise to overcome the flow resistance, increasing the noise source. For this reason, this study focuses on soundproofing ventilation ducts through acoustic metamaterials with no inner duct section decreasing. A crucial part of this study falls into the multiphysical interaction between acoustics and fluid dynamics, which is a phenomenon that may result in a challenging analytical model. In conditions of flowing motion, the wave vector has been modelled according to the Lighthill model: the component of the velocity rotor potential becomes significant, influencing the soundproofing performance due to the metamaterial placed at the edge of the inner surface of the duct. FEM analysis helped design a series of samples which then have been tested experimentally in static conditions. Once the numerical method is calibrated, further multiphysical numerical analysis are used to implement the sound insulation properties of the metamaterial-based filter through dynamic flow conditions. Guidelines for multiphysical setup for wave-based simulation are drawn, and preliminary experimental results are presented.

On the Necessity for Improving Water Efficiency in Commercial Buildings: A Green Design Approach in Hot Humid Climates

Water, a fundamental and indispensable resource necessary for the survival of living beings, has become a pressing issue in numerous regions worldwide due to scarcity. Urban areas, where the majority of the global population resides, witness a substantial consumption of blue water, particularly in commercial buildings. This study investigates the potential for enhancing water efficiency within an ongoing high-rise office building construction situated in a tropical climate. The investigation utilizes the green building guidelines of leadership in energy and environmental design (LEED) through a case-study-based research approach. Strategies included using efficient plumbing fixtures (such as high air–water ratio fixtures and dual-flush toilets), the selection of native plants, implementing a suitable irrigation system, introducing a rainwater harvesting system (RWHS) and improving the mechanical ventilation and air conditioning (MVAC) system. The results showed a 55% reduction in water use from efficient fixtures, a 93% reduction in landscaping water needs and a 73% overall water efficiency with a RWHS from the baseline design. Additionally, efficient cooling towers and the redirection of condensed water into the cooling tower make-up water tank improved the overall water efficiency to 38%, accounting for the water requirements of the MVAC system. The findings of this study can contribute to more sustainable and water-efficient urban development, particularly in regions facing water scarcity challenges. The significance of these findings lies in their potential to establish industry standards and inform policymakers in the building sector. They offer valuable insights for implementing effective strategies aimed at reducing blue water consumption across different building types.

Assessment of Indoor Air Quality Performance in a Building at Kemaman, Terengganu

Violations of IAQ regulations can lead to sick building syndrome (SBS), which manifests as symptoms like respiratory difficulties, eye irritation, skin issues, and headaches. Monitoring IAQ is crucial for ensuring the well-being of occupants and preventing health issues and reduced productivity. Compliance with IAQ regulations is necessary to avoid legal concerns and penalties. The study aims to evaluates IAQ in accordance with the Department of Occupational Safety and Health (DOSH) Malaysia's Industry Code of Practice on Indoor Air Quality (ICOP 2010), which provides guidelines and acceptable limits for physical and chemical contaminants on the impact on occupants' health and comfort in Bangunan Persekutuan Kemaman, a government office building in Terengganu, Malaysia. Objective and subjective measurements were collected to assess physical parameters, chemical contaminants, and ventilation performance indicators. The data revealed that the airflow, relative humidity, and light intensity in the building did not meet the ICOP 2010 standards, indicating the need for repair and maintenance of the mechanical ventilation and air-conditioning (MVAC) system. The subjective survey completed by occupants indicated symptoms such as drowsiness, fatigue, and headaches, which are associated with poor IAQ. The study concludes that improvements are necessary to ensure compliance with IAQ regulations and recommends further research on the relationship between air temperature, relative humidity, and older building designs.

Sick building syndrome in air-conditioned museum

ABSTRACT Exposure to indoor contaminants in air-conditioned buildings can cause serious health effects to their occupants. The failure to control indoor air contaminants is one of the factors that contribute to poor indoor air quality (IAQ) and is a major contributor to sick building syndrome (SBS) symptoms. This study aims to investigate the relationship between the maintenance of mechanical ventilation and air conditioning (MVAC) that is installed in museums towards IAQ and SBS. Data were collected through site visits and observations with a combination of field measurements and a questionnaire survey. The field measurements results show that several locations in the museums were in a state of heat discomfort. The recorded measurement of air velocity was very low and the average level of HCHO concentrations are above the permissible level. The correlation test between the satisfaction level of MVAC maintenance on IAQ and SBS also shows significant relationships, indicating that MVAC maintenance in the museum affects the comfort and health of the occupants.

Predicting Job Satisfaction of Malaysian Mechanical Ventilation and Air Conditioning Maintenance Personnel in the Oil and Gas Sector

Oil and gas industry pose a higher risk of operational hazards for the maintenance personnel who are least exposed to job satisfaction measures especially in the field of mechanical ventilation and air conditioning (MVAC). This study discussed current trends in the demographics of maintenance personnel in Malaysia's oil and gas maintenance sector. 50 MVAC employees (n=50) from a Malaysian oil and gas company completed a questionnaire survey as a part of this study. The set of questions was related to intrinsic and extrinsic motivation that can help achieve employees' job satisfaction. The results indicated that the general element in M = 4.26 is at the highest level with M = 4.15, and the extrinsic element is at M = 4.15. The reliability of Cronbach Alpha of each component was 0.937, 0.902, and 0.899. The warrior experience and the significant values of 0.027, 0.049, and 0.019 were essential predictors of overall job satisfaction. The findings from this study offer an up-to-date overview of employees' inner and outer motivation to continue improving work performance.

Fabrication of Duct Cleaning Setup

In the world of globalization and modernization where air conditioning system acts as the pulse of every modern infrastructure, in which air supply plays a prominent role in cooling. The duct systems work as nerves of these air conditioning units. Also, its maintenance is required for greater efficiency to prevent damage. Our research focuses on the non-destructive techniques to clean the dust, fungi, foreign particles and it also detects flaws, cracks, and corrosion inside the ducts. The technique if used on a regular basis, we can increase the efficiency and life of ducts and the cooling units. This research involves a wirelessly controlled robot powered by batteries, having wheeled and wall tire system for movement inside different cross-sectional ducts. The prime objective is to clean the ducts by a cleaning probe attached to the robot, different probes like scrubber, dust, fungi, and bacteria from ducts. Helping to provide the healthy conditioned air supply to the chambers. The robot equipped with infra-red cameras for the live view of inside the ducts. As dust, fungi, bacteria and corrosion affects the efficiency, the cleaning probe provides the removal of these impurities. The simple design of robot makes it more convenient and useful for varying cross section ducts and helps to build its bond at consumer ends. Indoor Air Quality (IAQ) has become public concern recently. Air ducting is used in Mechanical Ventilation and Air Conditioning (MVAC) system to deliver air to the building occupants. Without proper maintenance of the ducting system, it will affect the IAQ of overall building. Monitoring air ducting is the preliminary step to get real view inside the ducting. This study focused on the development of the Mechanical Ducting Robot to monitor the ducting and data collection at real time.

Numerical simulation of bioaerosol particle exposure assessment in office environment from MVAC systems

Bioaerosol (i.e. biological aerosol) exposures in the office environment are associated with a wide range of health effects. The potential bioaerosol emission from mechanical ventilation and air conditioning (MVAC) systems can endanger the building occupants in office, especially as over 90% of commercial buildings in Hong Kong that are equipped with MVAC systems, due to the microbial growths inside MVAC systems, such as cooling coils and mixing chamber, were reported. This study evaluated the exposure risk of the bioaerosol emission from the MVAC systems to the building occupants. A two-phase flow computational fluid dynamics approach was adopted to simulate the emission, dispersion, deposition, and exhaustion of bioaerosol particles from the MVAC systems in a typical office cubicle by altering the ventilation strategies with four ventilation rates, four emission concentrations, and two microorganism species. The results reported that about 5% contribution of concentration level from the MVAC system including the ventilation rate is sufficient to dilute the biocontainment. This study suggested the importance of the maintenance strategies of MVAC systems for minimizing bioaerosol exposures in offices.

Development of Mechanical Robot for Ducting Monitoring in Mechanical Ventilation and Air Conditioning (MVAC) System

ndoor Air Quality (IAQ) problem mostly comes from improper maintenance of ducting. Monitoring of ducting were not widely practices since the awareness to maintain it will need consideration of budget. This paper examines the development of mechanical robot that can moveable across ducting to monitor ducting condition. The device expected to collect data such as Temperature (°C),, Relative Humidity (RH), gas pollutant and picture inside ducting. The result from this kind of monitoring should be a guide for proper maintenance activity. It also can predict necessary time and duration for duct cleaning. In conclusion, the mechanical robot data analysis that captured from ducting will be compared to the IAQ standard to create safe indoor air to the user or building occupants.

Dust Collection by a Fiber Bundle Electret Filter in an MVAC System

Electret filters are composed of thin, electrically charged fibers that are often utilized in industrial fields that require high collection efficiency with low flow resistance. A bundle-type electret filter in the Mechanical Ventilation and Air-Conditioning (MVAC) system of a Metro-subway was characterized in this study. The particle penetration and pressure drop parameters were examined under a filtration velocity ranging from 0.5 to 2.5 m/s. Particle penetration increased significantly in the early stages of filtration, but then became steady. The filter quality, which is a useful index of the filtration performance incorporating pressure drop and filtration efficiency, was evaluated for the test filters. The fiber bundle filter demonstrated a higher filter quality than the mechanical filter or the general panel-type electret filter with a small drop in pressure even at a high filtration velocity. In addition, the three dimensional structure and high electrostatic charge of the fiber bundle filter woul...

Energy saving potential for a high-rise office building

Within the context of this study, a walk-through energy audit was performed for a typical office building in Hong Kong. The focus of energy saving opportunities was mainly on mechanical ventilation and air conditioning (MVAC) and lighting. The emphasis was mainly on more energy-efficient equipment, a better control of the equipment, indoor air quality and human behaviour. Among others, the measures considered to reduce MVAC energy were replacing the air-cooled reciprocation chillers with water-cooled centrifugal chillers; installing variable speed drives (VSDs) for the secondary chilled water pump motors; maintaining the indoor air quality within reasonable limits while monitoring the indoor CO2 concentration to adjust the fan speed of primary air-handling units (PAUs) by VSDs and re-adjusting the temperature setpoint to use less energy for air conditioning; and encouraging environmentally friendly human behaviour within the built environment, especially in hot and humid countries such as Hong Kong. The measures to reduce lighting energy were mainly replacing the lamps with energy-efficient lamps and preventing over-illumination. The results led to the conclusion that an annual saving of around 48% of MVAC and 62% of lighting energy is possible for this building. The measures discussed are also applicable to other similar office buildings in Hong Kong or similar areas, especially to old buildings. Considering that a tremendous amount of electrical energy is consumed by office and other commercial buildings, any measures to reduce the energy use in these sectors will contribute significantly to the reduction of CO2 emissions and preservation of the environment.

Simulation of ventilated facades in hot and humid climates

The Hong Kong climate is sub-tropical with hot and humid weather from May to September and temperate climate for the remaining 7 months period. A mechanical ventilation and air-conditioning (MVAC) system is usually operated to avoid the high temperatures resulting in high peak cooling loads. The facade design has a significant influence on the energy performance of office buildings. This work evaluates different ventilated facade designs in respect to energy savings. Thermal building simulations (TRNSYS) were linked to nodal airflow network simulations (COMIS) for detailed ventilated double-skin facade performance. In order to validate the model, simulations were carried out for an office building in Lisboa; the results were compared with measured data from the same building. The simulation results of surface and air temperatures show good agreement with the measurements. The results of the study can be used to reduce surface temperatures by using different materials for the roller blind that is positioned in the cavity of the double-skin facade. The results can further be used to reduce the high peak cooling loads during the summer period. This may result in significant energy savings and a reduction in the system's cooling capacity. It proved that a careful facade design can play an important role in highly glazed buildings and provides potential for energy efficiency.

Survey of Airborne Bacterial Genus at a University Campus

Indoor airborne bacterial concentrations were measured at different locations in a university campus in Hong Kong where there was a Mechanical Ventilation and Air-conditioning (MVAC) system. Total bacterial counts were enumerated for both indoor and outdoor areas at specific time intervals. Information on temperature, relative humidity, number of occupants, and carbon dioxide levels were recorded simultaneously. Those parameters were correlated with total bacterial counts and each identifiable genus. Although, the number of genera for Gram-negative bacteria was higher than Gram-positive bacteria, the most abundant airborne genera found were Gram-positive bacteria especially Micrococcus and Staphylococcus. The indoor-to-outdoor ratios for the two predominant Gram-positive genera were greater than one, indicating that the source of the bacteria was indoors. There was a correlation between total bacterial counts with temperature, but the correlation was not significant. Pseudomonas had a correlation with relative humidity, but the correlation was not significant. The study also found that the total bacterial counts and a few genera including Staphylococcus and Pseudomonas, had a strong correlation with ventilation.

Thermal Environmental Interference with Airborne Bacteria and Fungi Levels in Air-Conditioned Offices

Indoor airborne bacteria and fungi levels can be selected as indicators of a healthy indoor environment. This study investigated the relationships between the airborne bacteria levels, fungi levels, and thermal environmental parameters, i.e., air temperature and relative humidity, in some offices with a Mechanical Ventilation and Air-Conditioning (MVAC) system operating. A total of 101 samples were collected from two typical Hong Kong air-conditioned office premises. There was evidence that the operation of the MVAC system would have significant influence on both of the indoor airborne bacteria and fungi levels. The results showed that no significant difference in airborne bacteria and fungi levels was observed between offices having similar thermal environments ( p > 0.05). However, significantly higher airborne bacteria and fungi levels were found in the same office during non-office hours when the air-conditioning system was shut down ( p<0.03). It was also reported that the airborne bacteria and fungi levels would be correlated with the thermal environmental parameters in some offices ( p<0.0001).

A discussion on potentials of saving energy use for commercial buildings in Hong Kong

A typical commercial building was selected for a detailed study of energy use by mechanical ventilation and air-conditioning (MVAC) systems. Data from preliminary building energy auditing were analyzed and compared with the energy use of other similar buildings. Correlation relationships between the building envelope heat gain and the electrical energy use for MVAC system with key parameters were derived with approaches similar to the Princeton Scorekeeping Method (PRISM). Further, the energy simulation program TRACE 600 was used to justify the results. A total of 20 energy-saving measures were investigated for possible use in local commercial buildings. The results provided are useful for engineers in designing energy-efficient commercial buildings or generating new design concepts for better MVAC systems.

Development of ANN-based models to predict the static response and dynamic response of a heat exchanger in a real MVAC system

This paper presents a systematic approach to develop artificial neural network (ANN) models to predict the performance of a heat exchanger operating in real mechanical ventilation and air-conditioning (MVAC) system. Two approaches were attempted and presented. Every detailed components of the MVAC system have been considered and we attempt to model each of them by one ANN. This study used the neural network technique to obtain a static and a dynamic model for a heat exchanger mounted in an air handler unit (AHU), which is the key component of the MVAC system. It has been verified that almost all of the predicted values of the ANN model were within 95% - 105% of the measured values, with a consistent mean relative error (MRE) smaller than 2.5%. The paper details our experiences in using ANNs, especially those with back-propagation (BP) structures. Also, the weights and biases of our trained-up ANN models are listed out, which serve as good reference for readers to deal with their own situations.

Optimization of MVAC systems for energy management by evolutionary algorithm

Energy management in existing building services installations is an essential focus of contemporary facilities management. The subway company that is one of the major utilities services in Hong Kong Special Administrative Region has considered better energy management schemes in its subway stations to reduce the running cost. In the past few years some feasible measures in the mechanical ventilation and air conditioning (MVAC) systems were implemented, however the engineering decisions were supported by trial‐and‐error or imprecise estimation. Improvement to this process would be possible if numerical optimization methods were to be used. An evolutionary algorithm coupled with an external plant simulation programme was applied to determine the optimum conditions of the essential parameters of the MVAC systems. For the centralized MVAC systems under study, the developed optimization and simulation model was found useful in appraising the energy management opportunities for effective design and facilities management.

Numerical studies of airflows induced by mechanical ventilation and air-conditioning (MVAC) systems

Numerical studies of airflows induced by mechanical ventilation and air-conditioning (MVAC) systems

Numerical studies of airflows induced by mechanical ventilation and air-conditioning (MVAC) systems

Indoor air flows induced by mechanical ventilation and air-conditioning (MVAC) systems are simulated by the technique of computational fluid dynamics (CFD). Examples are taken to illustrate the capability of the technique. These include the evaluation of basic ventilation system designs, ventilation systems in an enclosed car-park, spot cooling system, air-conditioning system with chilled ceiling, cold air distribution system, effect of casual heat gain on the air diffuser induced air flow and the underfloor air supply system. Evaluation of the performances of the mechanical systems in those buildings are performed. Physical experiments in air-conditioned spaces reported by Sakamoto and Matsuo; and by Murakami and Kato are also simulated to assess how good are the predicted results.

00/01573 Simulation on energy use for mechanical ventilation and air-conditioning (MVAC) systems in train compartments

00/01573 Simulation on energy use for mechanical ventilation and air-conditioning (MVAC) systems in train compartments

Simulation on energy use for mechanical ventilation and air-conditioning (MVAC) systems in train compartments

Unlike the conventional automotive, modem railway trains are designed with non-openable windows; and a mechanical ventilation and air-conditioning (MVAC) system is installed in each train compartment for better indoor air quality as well as to provide a thermally comfortable environment. The ventilation rate is no doubt a critical element in the design of a MVAC system, especially in Hong Kong where the daily passenger load is extremely heavy. Earlier studies illustrated that carbon dioxide can be controlled at 1000 ppm by increasing the ventilation rate to 25.2 m 3 h −1; however, it will also lead to an increase in energy consumption. In this paper, the electrical energy consumption at various ventilation rates was studied, and the cost of maintaining a low carbon dioxide level was estimated. These provide solid information for the local railway companies to improve the air quality inside the train compartments.