[PDF] Airflow In Ducts eBook

Author :
Publisher :
Page : 52 pages
File Size : 15,79 MB
Release : 2017
Category :
ISBN :

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This study tests the performance of a variable airflow small-diameter duct heating, ventilation, and air conditioning (HVAC) system in a new construction unoccupied low-load test house in Pittsburgh, Pennsylvania. The duct system was installed entirely in conditioned space and was operated from the winter through summer seasons. Measurements were collected on the in-room temperatures and energy consumed by the air handler and heat pump unit. Operation modes with three different volumes of airflow were compared to determine the ideal airflow scenario that maximizes room-to-room thermal uniformity while minimizing fan energy consumption. Black felt infrared imagery was used as a measure of diffuser throw and in-room air mixing. Measured results indicate the small-diameter, high velocity airflow system can provide comfort under some conditions. Solar heat gains resulted in southern rooms drifting beyond acceptable temperature limits. Insufficient airflow to some bedrooms also resulted in periods of potential discomfort. Homebuilders or HVAC contractors can use these results to assess whether this space conditioning strategy is an attractive alternative to a traditional duct system. The team performed a cost analysis of two duct system configurations: (1) a conventional diameter and velocity duct system, and (2) the small-diameter duct system. This work applies to both new and retrofit homes that have achieved a low heating and cooling density either by energy conservation or by operation in a mild climate with few heating or cooling degree days. Guidance is provided on cost trade-offs between the conventional duct system and the small-diameter duct system.

Author : Fridolin P. Mechel
Publisher :
Page : 64 pages
File Size : 40,58 MB
Release : 1965
Category : Air ducts
ISBN :

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Several studies of the interaction between air flow and airborne sound in a duct were made. Three projects were investigated: (1) The excitation of boundary layer distortions in a laminar boundary layer by simulated oscillatory flexural waves was investigated. Results show boundary layer waves are excited whenever the phase velocity of the flexure wave is in the instability range of the phase velocity of boundary layer waves. (2) The propagation of a pressure pulse wave front and the acoustic impedance of porous absorbers are examined in ducts with air flow. Measurements prove the sound energy of the wave front is directed towards the walls and the absorber impedance becomes nonlinear when the absorber is penetrated by the flow. (3) the effect on the acoustic radiation impedance of an orifice with flow discharge restricted by fences and diaphragms was investigated. The acoustic resistance was shown to increase at low frequencies due to the restrictions.

Author : Charles Nehme
Publisher : Charles Nehme
Page : 30 pages
File Size : 24,58 MB
Release : 2023-01-19
Category : Technology & Engineering
ISBN :

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HVAC duct is a system of metal or flexible tubes that are used to distribute heated or cooled air throughout a building. They are typically made of sheet metal, fiberglass, or plastic and come in a variety of sizes. They are connected to registers, diffusers, and grilles, which help to regulate the air flow and temperature. Duct sizing is the process of ensuring that the right size of ducts and fittings is used in a ventilation system. This process involves calculating the air volume, velocity and pressure drop of the system, and then selecting the appropriate size of ducts and fittings to accommodate that air volume, velocity and pressure drop. The first principle of HVAC duct design is selecting the right size and type of components. The size and type of components are determined by the desired airflow, static pressure, and other criteria. Proper sizing helps to ensure that the system can adequately heat or cool the space. The components should also be selected based on the desired sound level, ease of installation, and other design considerations. HVAC Ductwork book, HVAC Rectangular Duct, HVAC Duct Design

Author : Y. Chartier
Publisher : World Health Organization
Page : 132 pages
File Size : 23,17 MB
Release : 2009
Category : Medical
ISBN : 9241547855

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This guideline defines ventilation and then natural ventilation. It explores the design requirements for natural ventilation in the context of infection control, describing the basic principles of design, construction, operation and maintenance for an effective natural ventilation system to control infection in health-care settings.

Author : Kevin Douglas Weaver
Publisher :
Page : pages
File Size : 27,94 MB
Release : 2012
Category :
ISBN :

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Airflow pressure losses through rigid metallic and non-metallic flexible ducts were studied and recommendations to improve the rating of flexible ducts were made as part of this study. The testing was done in compliance with ASHRAE Standard 120-1999, Methods of Testing to Determine Flow Resistance of HVAC Air Ducts and Fittings (ASHRAE 1999). Duct sizes of 6", 8", and 10" were tested in a positive pressure, blow-through configuration. An As-Built Test Protocol expands the test configurations specified by Standard 120-1999. Results of the current tests extend the existing ASHRAE/ACCA data for flexible duct which does not include pressure loss data for flexible ducts that are compressed beyond approximately 4%. The data from this study exhibit higher pressure drops than prior ACCA or ASHRAE data. Some configurations exhibit over ten times the pressure loss found in rigid duct or fully stretched flexible duct of the same diameter.