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Testing and Balancing HVAC Air and Water Systems
Thoroughly revised, this book provides the reader with an understanding of the principles and practices of testing and balancing (TAB) heating, ventilating, and air conditioning (HVAC) air and water systems. For the novice and the experienced testing and balancing technician, it is a field reference book of procedures, equations, and information tables. Divided into five parts, Part I has general and specific balancing procedures for constant air volume systems, variable air volume systems, return air systems, and fans and fan performance. Part II covers testing and balancing fume hood systems and cleanrooms, commissioning HVAC systems, centrifugal pumps and pump performance, analog and digital controls and water balancing procedures using flow meters, system components, and temperatures. Part III covers fans, pumps, air distribution, water distribution, motors, electrical, fluid flow, psychrometrics, refrigeration, and instrument usage and care. Part IV includes equations and tables. New to this edition, Part V has information and additional test and balance procedures and graphics for chapters 1-7 and 13-14. TAB Data and Test forms are in the new addendum as well. • Provides the readers with revised information about the principles and practices of testing and balancing (TAB) heating • Represents a field reference guide for both the novice and experienced testing and balancing technician • Includes a new section with information and additional test and balance procedures and graphics
eBook
Severe Covid-19
Patients with severe Covid-19 should have close monitoring for the need for endotracheal intubation; intubated patients should receive lung-protective ventilation. Data from randomized, controlled trials support a reduction in mortality with the use of dexamethasone and a reduction in time to clinical recovery with the use of remdesivir.
Journal Article
Seasonal Variation of Air Purifier Effectiveness and Natural Ventilation Behavior: Implications for Sustainable Indoor Air Quality in London Nurseries
This study investigates the seasonal effectiveness of high-efficiency particulate air (HEPA) purifiers and window-opening behaviors in three London nurseries, using continuous indoor and outdoor PM2.5 monitoring, window state and air purifier use, and occupant questionnaire data collected from March 2021 to February 2022. Of the approximately 40–50 nurseries contacted, only three agreed to participate. Results show that HEPA purifiers substantially reduced indoor particulate matter (PM2.5), with the greatest effect observed during the heating season when windows remained closed for longer periods. Seasonal and behavioral analysis indicated more frequent and longer window opening in the non-heating season (windows were open 41.5% of the time on average, compared to 34.2% during the heating season) driven by both ventilation needs and heightened COVID-19 concerns. Predictive modeling identified indoor temperature as the main driver of window opening, while carbon dioxide (CO2) had a limited effect. In addition, window opening often increased indoor PM2.5 under prevailing outdoor air quality conditions, with mean concentrations rising from 2.73 µg/m3 (closed) to 3.45 µg/m3 (open), thus reducing the apparent benefit of air purifiers. These findings underscore the complex interplay between mechanical purification and occupant-controlled ventilation, highlighting the need to adapt indoor air quality (IAQ) strategies to both seasonal and behavioral factors in educational settings.
Journal Article
The role of real-time, on-site, whole-genome sequencing of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) in guiding the management of hospital outbreaks of coronavirus disease 2019 (COVID-19)
We aimed to demonstrate the role of real-time, on-site, whole-genome sequencing (WGS) of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) in the management of hospital outbreaks of coronavirus disease 2019 (COVID-19).
This retrospective study was undertaken at our institutions in Sydney, New South Wales, Australia, between July 2021 and April 2022. We included SARS-CoV-2 outbreaks due to SARS-CoV-2 δ (delta) and ο (omicron) variants. All unexpected SARS-CoV-2-positive cases identified within the hospital were managed by the infection control team. An outbreak was defined as 2 or more cases acquired on a single ward. We included only outbreaks with 2 or more suspected transmission events in which WGS was utilized to assist with outbreak assessment and management.
We studied 8 outbreaks involving 266 patients and 486 staff, of whom 73 (27.4%) and 39 (8.0%), respectively, tested positive for SARS-CoV-2 during the outbreak management. WGS was used to evaluate the source of the outbreak, to establish transmission chains, to highlight deficiencies in infection control practices, and to delineate between community and healthcare acquired infection.
Real-time, on-site WGS combined with epidemiologic assessment is a useful tool to guide management of hospital SARS-CoV-2 outbreaks. WGS allowed us (1) to establish likely transmission events due to personal protective equipment (PPE) breaches; (2) to detect inadequacies in infection control infrastructure including ventilation; and (3) to confirm multiple viral introductions during periods of high community SARS-CoV-2 transmission. Insights gained from WGS-guides outbreak management directly influenced policy including modifying PPE requirements, instituting routine inpatient SARS-CoV-2 surveillance, and confirmatory SARS-CoV-2 testing prior to placing patients in a cohort setting.
Journal Article
Analytical Model of the Frictional Heating in a Railway Brake Disc at Single Braking with Experimental Verification
A one-dimensional thermal problem of friction was formulated, taking into account the contact pressure increase at the beginning of the process. The obtained solution to this problem allows for the quick calculation of the transient temperature distribution in a railway brake disc during single braking application. In order to validate the developed model, the experimental tests were performed for two friction pairs consisting of the cast iron brake disc and pads comprising two composite materials. Theoretical results were compared with the data measured by thermocouples embedded in the brake disc during the full-size dynamometer tests. The maximum temperature values found based on the analytical solution are convergent with the corresponding empirical data. The consistency of the results obtained for two friction couples demonstrates the usefulness of the proposed computational model.
Journal Article
Thermal Performance Analysis of Borehole Heat Exchangers Refilled with the Use of High-Permeable Backfills in Low-Permeable Rock Formations
It is well known that the operation of a Borehole Heat Exchanger (BHE) can thermally induce groundwater convection in aquifers, enhancing the thermal performance of the BHE. However, the effect on the thermal performance of BHEs installed in low-permeable rock formations remains unclear. In this study, two BHEs were installed in a silty sandstone formation, one backfilled with high-permeable materials and the other grouted with sand–bentonite slurry. A Thermal Response Test (TRT) showed that the fluid outlet temperature of the high-permeable-material backfilled BHE was about 2.5 °C lower than that of the BHE refilled with sand–bentonite slurry, implying a higher thermal efficiency. The interpreted borehole thermal parameters also show a lower borehole thermal resistance in the high-permeable-material backfilled BHE. Physical model tests reveal that groundwater convective flow was induced in the high-permeable-material backfilled BHE. A test of BHEs with different borehole diameters shows that the larger the borehole diameter, the higher the thermal efficiency is. Thus, the thermal performance enhancement was attributed to two factors. First, the induced groundwater flow accelerates heat transfer by convection. Additionally, the increment of the thermal volumetric capacity of the groundwater stored inside a high-permeable-material refilled borehole stabilized the borehole’s temperature, which is key to sustaining high thermal efficiency in a BHE. The thermal performance enhancement demonstrated here shows potential for reducing reliance on fossil-fuel-based energy resources in challenging geological settings, thereby contributing to developing more sustainable geothermal energy solutions. Further validation in diverse field conditions is recommended to generalize these findings.
Journal Article
Evaluation of Nano Fluids with Minimum Quantity Lubrication in Turning of Ni-Base Superalloy UDIMET 720
This article focuses on turning superalloy Udimet 720, which is difficult to work with, using different coolant/lubricant methods. The study includes delivering Graphene and Multi-Walled Carbon Nanotubes nanopowders homogeneously dispersed in vegetable oil to the cutting area with the minimum quantity lubrication (MQL) method. Experiments at different cutting speeds and feed rates were repeated in four different cutting environments. Compared to dry turning, the cutting zone temperature of the cutting fluid delivered to the cutting zone by MQL methods decreased. In addition, thanks to the nanopowders, it formed an oil film by better penetrating the cutting tool-chip interface and reducing the cutting tool’s wear. With the reduced cutting tool wear, the cutting tool could maintain its form for a longer period of time, so better quality surfaces were obtained on the workpiece surface. As a result of the study, it was found that cutting zone temperature improved by 30%, tool wear by 51.8% and surface roughness by 43.9%.
Journal Article
Residential Air Source Heat Pump Water Heater Performance Testing and Feasibility Analysis in Cold Climate
As new energy-efficient technologies emerge, space and water heating systems are continuously evolving. The latest generation of heating, ventilation, and air conditioning (HVAC) systems in Canada and other countries is shifting away from natural gas heating to cleaner electrical options, such as air-source heat pump water heaters (ASHPWH). While many studies focus on reducing space heating, research on the effectiveness of ASHPWHs in cold climates is limited. This study aims to fill that knowledge gap by analyzing the performance of ASHPWHs in typical home applications across various climates in Canada. An experimental setup was constructed, and TRNSYS modeling was employed to evaluate the techno-economic and environmental performances of these systems in comparison to existing natural gas and conventional electric water heating systems. The findings of this research indicate that ASHPWHs possess the capability to substantially decrease greenhouse gas (GHG) emissions when compared to conventional natural gas-fired water heaters. Despite this significant environmental benefit, ASHPWHs may not be the most cost-effective option due to the prevailing natural gas pricing structure. Nevertheless, there is potential for these systems to become more economically viable in the future, particularly if an appropriate level of carbon pricing mechanisms is implemented.
Journal Article