Heating, Ventilation, And Air Conditioning Design Research Articles

U-Net architecture for high-resolution thermal image segmentation: Enhancing CFD models in smart HVAC design

This paper presents an enhanced U-Net architecture for accurately segmenting high-resolution thermal images to facilitate the design of intelligent Heating, Ventilation, and Air Conditioning (HVAC) systems using Computational Fluid Dynamics (CFD) models. Indoor thermal comfort for occupants will improve under the same energy load by imposing comfort demands. Segmented data is fed into CFD simulations using a U-Net variant for thermal imagery. Integrating the segmented thermal data into the CFD simulations increases the model’s accuracy by 15 % for segmentation and 20% for prediction when compared to a traditional U-Net architecture. Experimental findings demonstrate the potential to achieve energy savings of up to 25 % in the simulated scenario by using the trained and validated model on a dataset of 1,500 high-resolution thermal images of various building styles. Compared to existing methods, the proposed method saves 30% in total simulation time for complex building models. Deep learning enables building the next generation of HVAC systems by pushing the boundaries of energy-efficient and environmentally friendly buildings. This study shows that advanced computer vision can be leveraged to create more innovative and sustainable built environments, leading to drastic improvements in energy efficiency.

Advancing energy recovery ventilators with phase change materials for cooling load reduction and heat exchange efficiency improvement

Efforts to reduce building energy emissions and achieve net-zero carbon scenarios globally have increasingly focused the building sector on improving energy efficiency. Heating, ventilation, and air conditioning (HVAC) systems play a vital role in providing comfortable indoor environments but significantly contribute to energy consumption and greenhouse gas emissions. Energy recovery ventilators are efficient active systems that prevent unnecessary indoor heat loss and gain, regardless of outdoor climate, making them excellent technologies for achieving zero energy. In a hot and humid summer climate, such as in Korea, it is crucial to enhance the efficiency of energy recovery ventilators and reduce cooling energy consumption. A Green HVAC design aimed at reducing the energy consumption of active systems to near zero was proposed by applying phase change material-based modules with high heat storage performance to energy recovery ventilators. The phase change material module is stabilized with high thermal conductivity aluminum packing and is configured as a mesh-type structure to amplify heat exchange efficiency with air. Compared to the energy recovery ventilator, the application of the module demonstrated a reduction in supply air temperature by an average of 2.6 °C in high-temperature outdoor. During the effective operating period, a continuous indoor intake temperature reduction effect was observed, and the sensible heat exchange efficiency showed a 21.32 % improvement with the module using n-octadecane. Phase change material modules that can enhance ventilation and improve energy efficiency in high-temperature environments can be proposed as a technology to achieve Green HVAC.

HVAC Design Optimization for Pharmaceutical Facilities with BIM and CFD

Building Information Modeling (BIM) has been widely used in the past decade to enhance the design quality of Heating, Ventilation, and Air Conditioning (HVAC) systems. However, in specialized areas such as pharmaceutical facilities, HVAC design has traditionally relied on Computer-Aided Design (CAD) drawings. This conventional approach does not allow for the simulation of temperature distribution or the verification of system efficiency, which may lead to design failures. To address these challenges in pharmaceutical facilities, this study proposed a BIM-based approach for optimizing HVAC design with Computational Fluid Dynamics (CFD). By employing CFD to simulate the dynamic airflow conditions of pharmaceutical clean rooms, the effectiveness of HVAC systems can be verified. A case study of a clean room HVAC design is presented to demonstrate the workflow. The results of the case study indicated that the pharmaceutical temperature requirements were met within 1 °C during the design optimization simulation, and there was a 95% match in the 72 h temperature mapping test during site validation. The results confirmed that using CFD with BIM not only successfully simulates the design intentions of indoor air quality but also suggests HVAC system optimization for the required clean room design. The findings of this paper contribute to the body of knowledge on overcoming the limitations of the traditional CAD-based HVAC design process and provide valuable insights on optimizing HVAC design with BIM and CFD technologies.

Evaluation of large language models (LLMs) on the mastery of knowledge and skills in the heating, ventilation and air conditioning (HVAC) industry

Large language models (LLMs) have shown human-level capabilities in solving various complex tasks. However, it is still unknown whether state-of-the-art LLMs master sufficient knowledge related to heating, ventilation and air conditioning (HVAC) systems. It will be inspiring if LLMs can think and learn like professionals in the HVAC industry. Hence, this study investigates the performance of LLMs on mastering the knowledge and skills related to the HVAC industry by letting them take the ASHRAE Certified HVAC Designer examination, an authoritative examination in the HVAC industry. Three key knowledge capabilities are explored: recall, analysis and application. Twelve representative LLMs are tested such as GPT-3.5, GPT-4 and LLaMA. According to the results, GPT-4 passes the ASHRAE Certified HVAC Designer examination with scores from 74 to 78, which is higher than about half of human examinees. Besides, GPT-3.5 passes the examination twice out of five times. It demonstrates that some LLMs such as GPT-4 and GPT-3.5 have great potential to assist or replace humans in designing and operating HVAC systems. However, they still make some mistakes sometimes due to the lack of knowledge, poor reasoning capabilities and unsatisfactory equation calculation abilities. Accordingly, four future research directions are proposed to reveal how to utilize and improve LLMs in the HVAC industry: teaching LLMs to use design tools or software in the HVAC industry, enabling LLMs to read and analyze the operational data from HVAC systems, developing tailored corpuses for the HVAC industry, and assessing the performance of LLMs in real-world HVAC design and operation scenarios.

Thermal comfort and indoor air quality in hospitals in the subtropics: Analysis of operating rooms and waiting rooms conditions

The indoor air quality should provide adequate temperature and humidity levels, free from harmful pollution concentration. Proper heating, ventilation and air-conditioning (HVAC) system management is crucial in hospitals to prevent transmission of contaminated air and diseases. To verify whether healthcare facilities meet standard criteria for thermal comfort and indoor air quality, a field investigation in waiting and operating rooms was conducted in six hospitals in Brazil, in the summer. Thermal comfort parameters, carbon dioxide (CO2) concentration and differential air pressure were collected in loco. The results demonstrated that CO2 concentration was over 1,000 ppm in four waiting rooms, and no positive pressure was guaranteed in the operating room. The medical staff showed different thermal sensation variations in zone 1 (around the operating table) and zone 2 (remaining space around zone 1). In conclusion, most operating rooms had significant contamination risks and did not provide thermal comfort conditions to occupants. Due to improper HVAC design or high occupational density, air change rates were insufficient to guarantee adequate air renewal in the waiting rooms. There is an opportunity to improve the operation and maintenance process to provide healthy and comfortable environments in healthcare facilities, reducing nosocomial infections, especially during pandemic times.

Investigating the impact of HVAC and Sanitizer system design on the transmission of SARS-CoV-2 in Hospital Isolation Units

The COVID-19 pandemic has presented unprecedented challenges to healthcare facilities worldwide. Hospital isolation units have played a crucial role in the management of COVID-19 patients. However, the transmission of the virus within these units can lead to severe consequences for patients, healthcare workers, and the broader community. This research proposes a framework to evaluate the impact of HVAC (Heating, Ventilation, and Air Conditioning) and sanitizer system design on the transmission of SARS-CoV-2 in isolation unit at Saniat Rmel Hospital in Tetouan Morocco by using computational fluid dynamics (CFD) and the realizable k−ϵ turbulence model. Furthermore, the study investigates the effect of different inlet air velocities on the dispersion of airborne viral particles in the isolation unit. The results indicate that the air change rate plays a critical role in the spread and concentration of pathogens in the isolation unit. It was determined that the high inlet air velocity can lead the particles fluid including the virus reaches the exhaust port in a short time, in addition, it can facilitate the distribution of sanitizer throughout an isolation unit, which could potentially reduce the concentration of the virus. The outcome suggests that the placement and orientation of the air conditioner combined with the sanitizer system have a significant impact on the movement characteristics of fluid particles within the enclosed environment.

Realization of rule-based automated design for HVAC duct layout

In the traditional process of pipeline design, a designer typically creates a general layout of pipeline based on their experience, and then calculates whether the hydraulic calculation of pipeline meets the requirements. This method of design is both time-consuming and labor-intensive. Furthermore, the results are often suboptimal and prone to errors, which creates a lot of waste of human and material resources. The objective of this paper is to propose a computer-aided method for completely automating the heating, ventilation and air conditioning (HVAC) duct system design process. This method incorporates all the necessary design processes, such as duct selection and hydraulic calculation, and introduces a rule-based divide-and-conquer method to the pipe routing design (PRD). The research assesses the practical effect of this piping design algorithm in a BIM environment using varied building scenarios. The findings show that the proposed method is capable of meeting the design requirements of actual projects. The automatic piping design technique presented in this paper can significantly reduce labor costs associated with HVAC design while eliminating calculation errors and compressing the design timeline for most of the complex projects to within 5 min.

Assessment methodology for dynamic occupancy adaptive HVAC control in subway stations integrating passenger flow simulation into building energy modeling

Heating, ventilation, and air conditioning (HVAC) systems in subway stations are often pre-scheduled to non-discriminatorily control large areas, ignoring uneven and dynamic thermal demand. Although building energy modeling (BEM) contributes to optimizing HVAC design and operation, it is limited in investigating dynamic occupancy adaptive HVAC control strategies in large open subway stations. This research formalized an integrated thermal control methodology (ITCM) that integrates passenger flow simulation and BEM to assess the dynamic occupancy adaptive HVAC control strategies for subway stations. To evaluate the applicability and effectiveness of ITCM, we developed a prototype coupling AnyLogic and EnergyPlus and carried out a simulation-based case study using a Hong Kong subway station. Based on the case study, we identified that ITCM enables subway station development and management teams to assess the comprehensive dynamic occupancy adaptive HVAC control strategies (e.g., decomposed thermal zones considering the layouts of diffusers and variable air volume boxes) in a timely and consistent manner. In addition, the case study results show that adaptive control with ceiling diffusers could save between 1.8% and 24.4% of cooling energy without considerably sacrificing thermal comfort.

Numerical investigation of airborne infection risk in an elevator cabin under different ventilation designs

Airborne transmission of SARS-CoV-2 via virus-laden aerosols in enclosed spaces poses a significant concern. Elevators, commonly utilized enclosed spaces in modern tall buildings, present a challenge as the impact of varying heating, ventilation, and air conditioning (HVAC) systems on virus transmission within these cabins remains unclear. In this study, we employ computational modeling to examine aerosol transmission within an elevator cabin outfitted with diverse HVAC systems. Using a transport equation, we model aerosol concentration and assess infection risk distribution across passengers' breathing zones. We calculate the particle removal efficiency for each HVAC design and introduce a suppression effect criterion to evaluate the effectiveness of the HVAC systems. Our findings reveal that mixing ventilation, featuring both inlet and outlet at the ceiling, proves most efficient in reducing particle spread, achieving a maximum removal efficiency of 79.40% during the exposure time. Conversely, the stratum ventilation model attains a mere removal efficiency of 3.97%. These results underscore the importance of careful HVAC system selection in mitigating the risk of SARS-CoV-2 transmission within elevator cabins.

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.

The Impact of Heating, Ventilation, and Air-Conditioning Design Features on the Transmission of Viruses, Including SARS-CoV-2: Overview of Reviews.

The COVID-19 or SARS-CoV-2 outbreak was declared a pandemic by the World Health Organization in March 2020. Almost 2 years later (early February 2022), the World Health Organization reported over 383 million cases of the disease caused by the virus, with over 5.6 million deaths worldwide. Debate regarding the routes of transmission was substantial early in the pandemic; however, airborne transmission emerged as an important consideration. Infectious airborne agents can spread within the built environment through heating, ventilation, and air-conditioning (HVAC) systems. Multiple features of HVAC systems can influence transmission (eg, ventilation, filtration, UV radiation, and humidity). Understanding how HVAC features influence airborne transmission is critical to mitigate the spread of infectious agents. Given the airborne transmission of SARS-CoV-2, an overview of reviews was conducted to understand what is already known from the scientific literature about how virus transmission may be affected by HVAC design features in the built environment. Ovid MEDLINE and Compendex were searched from inception to January 2021. Two reviewers independently screened the titles, abstracts, and full text of potentially relevant reviews, using a priori inclusion criteria: systematic reviews examining the effects of HVAC design features on virus transmission. Two reviewers independently assessed the methodological quality using AMSTAR2. Searching identified 361 citations, of which 45 (12.5%) were potentially relevant and 7 (2%) were included. Reviews were published between 2007 and 2021 and included 47 virus studies. Two earlier reviews (2007 and 2016) of 21 studies found sufficient evidence that mechanical ventilation (airflow patterns and ventilation rates) plays a role in airborne transmission; however, both found insufficient evidence to quantify the minimum mechanical ventilation requirements. One review (2017) of 9 studies examining humidity and indoor air quality found that influenza virus survival was lowest between 40% and 80% relative humidity; the authors noted that ventilation rates were a confounding variable. Two reviews (2021) examined mitigation strategies for coronavirus transmission, finding that transmission decreased with increasing temperature and relative humidity. One review (2020) identified 14 studies examining coronavirus transmission in air-conditioning systems, finding that HVAC systems played a role in virus spread during previous coronavirus outbreaks. One review (2020) examined virus transmission interventions in public ground transportation, finding ventilation and filtration to be effective. Seven reviews synthesizing 47 studies demonstrated a role for HVAC in mitigating airborne virus transmission. Ventilation, humidity, temperature, and filtration can play a role in the viability and transmission of viruses, including coronaviruses. Recommendations for minimum standards were not possible owing to few studies investigating a given HVAC parameter. This overview examining HVAC design features and their effects on the airborne transmission of viruses serves as a starting point for future systematic reviews and identifying priorities for primary research.

Public Health Issue of Indoor Dilution Ventilation for Disease Prevention Versus PM2.5 in Intake Air in Auditoriums of Premier Engineering Institutes in India.

Background: Dilution ventilation by enhancing fresh air intake has been prescribed to reduce airborne infection spread during the COVID-19 pandemic. This is all the more important in assembly spaces like auditoriums. Premier technology institutes have large campuses with large auditoriums for academic and cultural events in India. These institutes serve as role models for society, where gatherings are essential, but there is also the possibility of transmission of all airborne respiratory infections, including tuberculosis, into the community. The fresh air taken in should also be filtered for pollution to prevent other lung issues.Aims: Fresh air intake and filtration have been studied in order to understand whether the outside air supplied indoors is filtered for PM2.5, which is a major ambient polluter in India.Settings and design/methods: In this study, the Right to Information Act of 2005 has been used to obtain first-hand information from the institutes with respect to the heating, ventilation, and air conditioning (HVAC) systems in their auditoriums. Twelve of the 19 institutes fall in cities with non-attainment of ambient air quality standards.Results: Eleven out of all those had recently integrated fresh air supply, and six replied in the negative. Only one out of all of them had appropriate filters.Conclusion: This study highlights the need for a possible trade-off between the use of air conditioners for thermal comfort + assumed protection against PM2.5, which is the switching off of air conditioners and manually opening up windows and using fans for ventilation. Indian HVAC design for gathering spaces, especially educational institutes, needs to factor in fresh air for dilution ventilation as well as PM2.5 filtration.

The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: A systematic review of ultraviolet radiation.

Respiratory viruses are capable of transmitting via an aerosol route. Emerging evidence suggests that SARS-CoV-2 which causes COVID-19 can be spread through airborne transmission, particularly in indoor environments with poor ventilation. Heating, ventilation, and air conditioning (HVAC) systems can play a role in mitigating airborne virus transmission. Ultraviolet germicidal irradiation (UVGI), a feature that can be incorporated into HVAC systems, can be used to impede the ability of viruses to replicate and infect a host. We conducted a systematic review of the scientific literature examining the effectiveness of HVAC design features in reducing virus transmission—here we report results for ultraviolet (UV) radiation. We followed international standards for conducting systematic reviews and developed an a priori protocol. We conducted a comprehensive search to January 2021 of published and grey literature using Ovid MEDLINE, Compendex, and Web of Science Core. Two reviewers were involved in study selection, data extraction, and risk of bias assessments. We presented study characteristics and results in evidence tables, and synthesized results across studies narratively. We identified 32 relevant studies published between 1936 and 2020. Research demonstrates that: viruses and bacteriophages are inactivated by UV radiation; increasing UV dose is associated with decreasing survival fraction of viruses and bacteriophages; increasing relative humidity is associated with decreasing susceptibility to UV radiation; UV dose and corresponding survival fraction are affected by airflow pattern, air changes per hour, and UV device location; and UV radiation is associated with decreased transmission in both animal and human studies. While UV radiation has been shown to be effective in inactivating viruses and reducing disease transmission, practical implementation of UVGI in HVAC systems needs to consider airflow patterns, air changes per hour, and UV device location. The majority of the scientific literature is comprised of experimental, laboratory-based studies. Further, a variety of viruses have been examined; however, there are few studies of coronaviruses and none to date of SARS-CoV-2. Future field studies of UVGI systems could address an existing research gap and provide important information on system performance in real-world situations, particularly in the context of the current COVID-19 pandemic. This comprehensive synthesis of the scientific evidence examining the impact of UV radiation on virus transmission can be used to guide implementation of systems to mitigate airborne spread and identify priorities for future research.Trial registration PROSPERO 2020 CRD42020193968.

Parametric-based design optimization of air distribution system in panelized construction

The heating, ventilation, and air conditioning (HVAC) system is generally the most time-consuming and costly of the mechanical, electrical, and plumbing systems to install, accounting for 25%–45% of the total project cost. In addition, HVAC systems are typically designed in an ad hoc manner, leading to errors, project delays, and cost overruns. A modularized HVAC system is a promising alternative that addresses these challenges through a comprehensive design that includes specific locations of vents, air terminals and ducts on panelized walls and/or floors for ease of manufacture and efficiency of assembly. In this context, this paper proposes an integrated design model comprising the following components: (i) parametric analysis to determine potential locations of air terminals for a high-performance system designed to maximize occupant comfort; (ii) HVAC design optimization to develop optimal air distribution system layout, which can reduce manual error and drafting time, based on design constraints; and (iii) reduced variation in detailed design (e.g., precise locations of supply diffusers) for efficient construction and off-site coordination of the ducting system. Four case studies are implemented to validate the effectiveness of the proposed model. The results reveal that the cost and time for air distribution system installation can be reduced by 23.9% and 21.3%, respectively.

A Comprehensive Evaluation Method for Air-Conditioning System Plants Based on Building Performance Simulation and Experiment Information

During the design stage of an HVAC (heating, ventilation, and air conditioning) system in a construction project, designers must decide on the most workable design scheme for the plant room in the building based on the evaluation of multiple aspects related to system performance that need to be considered, such as energy efficiency, economic effectiveness, etc. To solve this problem, this paper proposes a comprehensive evaluation method for the plant rooms of centralized air-conditioning systems in commercial buildings. This new method consists of two analyses used in tandem: Building Performance Simulation (BPS) models and a collection of real HVAC design cases (the carried-out design solutions). The BPS models and a knowledge of the reduction approach based on Rough Set (RS) theory are used to generate data and weight factors for the indices of energy efficiency; and the real design cases are employed with a heuristic algorithm to extract the compiled empirical information for other evaluation items of the centralized HVAC system. In addition, this paper also demonstrates an application in an actual case of a building construction project. By comparing the expert decision-making process and the evaluation results, it is found that they are basically consistent, which verifies the reasonability of the comprehensive evaluation method.

The Role of HVAC Design and Windows on the Indoor Airflow Pattern and ACH

The purpose of heating, ventilation, and air conditioning (HVAC) systems are to create optimum thermal comfort and appropriate indoor air quality (IAQ) for occupants. Air ventilation systems can significantly affect the health risk in indoor environments, especially those by contaminated aerosols. Therefore, the main goal of the study is to analyze the indoor airflow patterns in the heating, ventilation, and air conditioning (HVAC) systems and the impact of outlets/windows. The other goal of this study is to simulate the trajectory of the aerosols from a human sneeze, investigate the impact of opening windows on the number of air changes per hour (ACH) and exhibit the role of dead zones with poor ventilation. The final goal is to show the application of computational fluid dynamics (CFD) simulation in improving the HVAC design, such as outlet locations or airflow rate, in addition to the placement of occupants. In this regard, an extensive literature review has been combined with the CFD method to analyze the indoor airflow patterns, ACH, and the role of windows. The airflow pattern analysis shows the critical impact of inflow/outflow and windows. The results show that the CFD model simulation could exhibit optimal placement and safer locations for the occupants to decrease the health risk. The results of the discrete phase simulation determined that the actual ACH could be different from the theoretical ACH as the short circuit and dead zones affect the ACH.

Clothing Comfort- Physiological Status and Psychological Status

Clothing Comfort- Physiological Status and Psychological Status

Using long-term measurements of airflow, electrical power, indoor temperature, and CO2-concentration for evaluating sizing and performance of an all-air HVAC system in an office building - a case study

Monitoring performance of heating, ventilation, and air-conditioning (HVAC) during building operation enables to evaluate the appropriateness of the system’s design. Such insights can help to reduce energy consumption while ensuring satisfying indoor conditions in the monitored building. Additionally, such insight can help to improve future HVAC design. The aim of this paper is to present a case study demonstrating how HVAC engineers can evaluate whether the monitored air-handling units (AHUs) were appropriately sized and performed as intended based on design requirements regarding energy-efficiency, thermal conditions, and indoor air quality (IAQ). Three months of measurements of airflow, electrical power, indoor temperature, and CO2-concentrations were collected from an office building with six AHUs. The results showed that three of the AHUs were appropriately sized and satisfied the thermal condition, IAQ and energy-efficiency requirements. The remaining three AHUs were apparently appropriately sized and satisfied IAQ requirements, but they did not satisfy the required energy-efficiency and thermal conditions. The applied approach seemed to be suitable for supporting building operating managers for on-going performance monitoring as it was able to identify discrepancies from intended performance. But it remains the task for the operating personnel to identify the cause of the identified discrepancies.

Evaluation of HVAC Design Parameters in High-Performance Hospital Operating Theatres

Unidirectional flow air-conditioning systems are suitable for achieving indoor air quality required in high-performance operating rooms (organ transplants, cardiac surgery, aorta, orthopedic, burns, etc.). This paper analyzes indoor environmental conditions and technical and hygienic requirements for the design of heating, ventilation, and air-Conditioning (HVAC) systems for high-performance operating theatres. The main standards applicable to this type of operating rooms were compiled. Standard UNE 100713:2015, ASHRAE Standard 170-2017, and the European pre-norm EN 16244 were analyzed. A case study shows the lack of uniformity in design criteria and their ranges of values, which generates different design approaches. It was concluded that using these standards applicable to high-performance operating rooms leads to very different indoor environmental conditions for patients and medical personnel—air velocity profiles, air movement pattern, temperature, relative humidity gradients, and pressure stratification. Computational fluid dynamics (CFD) studies have been shown to detect areas of haven that favor microbiological load accumulation. In this way, it is possible to define cleaning protocols to attend these anomalies in a preventive way.

Effects of Recent Climate Change on Hourly Weather Data for HVAC Design: A Case Study of Osaka

The current design weather data used for heating, ventilation, and air conditioning (HVAC) design in Japan was created using an old data period. New design weather data should be created to reflect recent local climate change. Based on our previous proposal of creating design weather data with two weather indices (dry-bulb temperature and enthalpy) for HVAC design, design weather data for Osaka was created using more recently-measured weather data (period: 2001~2015) from the Japan Meteorological Agency (JMA) in this study. The effect of recent climate change on the design weather data created with eight proposed methods was found. It showed the change in weather elements for cooling design clearly trends to warmer and drier weather, with more solar radiation and lower enthalpy, while the trends in heating design are less clear, mainly showing higher enthalpy. Furthermore, the difference in the peak load for the heating and cooling designs using the new and old design weather data was compared. The comparison showed that the minimum difference in peak load for the heating design was found using the mean daily dry-bulb temperature as the first and second indices; for the cooling design, the minimum difference in peak load was found using mean daily enthalpy as both the first and second indices.