3: Ventilation
- Page ID
- 18015
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 3.1: Pressure Terms
- This page explains key pressure terms in HVAC systems: static pressure (resistance to airflow), velocity pressure (force from moving air), and total pressure (sum of static and velocity pressures). It emphasizes the importance of managing these pressures for effective air circulation and notes the necessity of testing pressures throughout the system for accurate evaluation.
- 3.2: Fans and Blowers
- This page explains the function of fans, or air-handler units, used to circulate treated air in buildings. It distinguishes between single-phase motors for smaller applications and three-phase motors for larger systems. Additionally, it categorizes fans into two types: axial fans, which pull air parallel to their axis, and centrifugal fans, which draw air at a right angle, highlighting their specific advantages and applications.
- 3.3: Axial Fan
- This page discusses axial fans, which are designed for low air volume movement under low static pressure, similar to airplane propellers. It describes variants like tubeaxial and vaneaxial fans, noting their efficiency and design features. These fans typically use single-phase AC motors and operate quietly, making them suitable for noise-sensitive areas, though they are inefficient for large volumes of air.
- 3.4: Centrifugal Fan
- This page discusses centrifugal fans, highlighting their effectiveness in moving large air volumes through duct systems with higher pressure than axial fans. They intake air at a 90-degree angle, which is then accelerated towards the exhaust vent. While they can be noisier and vary in drive mechanisms, they are ideal for scenarios where noise isn't a priority and excel in overcoming static pressure in ductwork, ensuring efficient air movement.
- 3.5: Fan Substitutions
- This page discusses important considerations when changing HVAC fan motors, highlighting three factors: airflow doubles with speed increase, static pressure increases by the square of speed, and electrical power consumption varies with the cube of speed. These relationship impacts electrical demand and underscores the importance of adhering to electrical circuit and device ratings to avoid overloading.
- 3.6: Dampers
- This page discusses dampers used in air system ductwork for regulating airflow. They can be controlled manually or remotely, consisting of a U-channel frame and sheet-metal blades driven by a motor. The two main types are opposed blade dampers and parallel blade dampers. Motor-driven dampers have actuators with springs that return the blades to a default position during power loss, closing outside dampers and opening return dampers.
- 3.7: Self Test 3
- This page discusses a self-test that can be taken multiple times, with an interactive online element linked for access. It also mentions that users of print, PDF, or eBook formats should visit the link for the quiz, while quiz questions are available at the end of the book for offline use.
Thumbnail: Ventilation Shafts (Unsplash License; Mitchell Luo via Unsplash)