Air Conditioning & Ventilation Basics

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Questions and Answers

Match the following techniques with their purpose in reducing cooling loads:

Insulate Wall, Insulate roof = Reducing Radiative Gain Internal Blinds = Reducing Direct Gain SUN-SHADING DEVICES (brise soleil) = Reducing Conductive Gain SHADING COEFFICIENT = Reducing Indirect Gain

Match the following formulas with their respective heat gain calculations:

QS = No: of people x Sensible heat gain per person x CLF = Heat Gain from People (Sensible Heat) QL = No: of people × Latent heat gain per person = Heat Gain from People (Latent Heat) Q = Btu/hr × Ballast factor × CLF = Heat Gain from Lighting SHADING COEFFICIENT = 1.0 for 1/8 inch (3mm) thick clear glass = Shading Coefficient Calculation

Match the following with their definitions:

Shading Coefficient (SC) = A measure used to quantify the solar heat gain of glass Conductive Gain = Heat gain through walls and roofs Radiative Gain = Heat gain from solar radiation Indirect Gain = Heat gain from internal loads

Match the following with their role in thermal comfort:

Air Temperature = Influences the sensation of warmth or coolness Relative Humidity = Affects the perception of temperature Air Movement = Influences the evaporation of sweat and heat loss Conditioning Strategies = Methods to achieve thermal comfort Signup and view all the answers

Match the following with their purpose in reducing cooling loads:

SUN-SHADING DEVICES (brise soleil) = Reducing Direct Gain Internal Blinds = Reducing Indirect Gain Insulate Wall, Insulate roof = Reducing Conductive Gain SHADING COEFFICIENT = Reducing Radiative Gain Signup and view all the answers

Match the following formulas with their respective units:

QS = No: of people x Sensible heat gain per person x CLF = Btu/hrt QL = No: of people × Latent heat gain per person = Btu/hr Q = Btu/hr × Ballast factor × CLF = Watts SHADING COEFFICIENT = 1.0 for 1/8 inch (3mm) thick clear glass = Dimensionless Signup and view all the answers

Match the following with their effects on thermal comfort:

High Air Temperature = Increases heat gain Low Relative Humidity = Increases evaporation of sweat Low Air Movement = Reduces heat loss High Shading Coefficient = Increases solar heat gain Signup and view all the answers

Match the following with their methods to reduce cooling loads:

Insulate Wall, Insulate roof = Passive Design Strategy SUN-SHADING DEVICES (brise soleil) = Active Design Strategy Internal Blinds = Building Orientation Strategy SHADING COEFFICIENT = Window Shading Strategy Signup and view all the answers

Match the following with their heat gain calculations:

QS = No: of people x Sensible heat gain per person x CLF = Heat Gain from Occupants QL = No: of people × Latent heat gain per person = Heat Gain from Lighting Q = Btu/hr × Ballast factor × CLF = Heat Gain from Equipment SHADING COEFFICIENT = 1.0 for 1/8 inch (3mm) thick clear glass = Heat Gain from Windows Signup and view all the answers

Match the following with their thermal comfort parameters:

Air Temperature = Thermal Comfort Parameter Relative Humidity = Thermal Comfort Parameter Air Movement = Thermal Comfort Parameter SHADING COEFFICIENT = Thermal Comfort Factor Signup and view all the answers

Study Notes

Air Conditioning & Ventilation Overview

Air conditioning adjusts air properties, particularly temperature and humidity, to enhance comfort.
Key components influencing thermal comfort include air temperature, humidity, mean radiant temperature, air movement, metabolic rate, and clo value.

Passive and Active Systems

Passive Systems utilize natural forces (e.g., cross ventilation, thermal mass, night ventilation).
Active Systems require energy input (e.g., Mechanical Ventilation and Air Conditioning (MVAC), radiant cooling).

Passive Design Principles

Building Orientation: Positioning buildings to optimize solar exposure and wind patterns.
Building Form: Design shapes that facilitate natural ventilation and reduce heat absorption.
Shading Elements: Incorporate architectural features to mitigate direct solar gain.
Building Materials: Select materials with appropriate thermal resistance and insulation properties.
Window Characteristics: Use windows that enhance natural light while minimizing heat gain.
Vegetation: Utilize landscaping elements, both exterior and interior, to provide cooling effects.
Daylighting: Maximize natural light penetration while reducing reliance on artificial lighting.

Thermal Comfort Research

Studies by Houghten and Yagloglou, conducted in 1927, identified three key parameters for assessing thermal comfort:
- Dry bulb temperature (DBT)
- Wet bulb temperature (WBT)
- Air velocity

Internal Gains and Heat Transfer

Solar Gain: The increase of heat from solar radiation through windows and other elements.
Internal Gain: Heat produced within a space from occupants, lighting, and equipment.
Cooling Load Calculations:
- Sensible heat gain from occupants, calculated as ( Q_s = \text{No. of people} \times \text{Sensible heat gain/person} \times \text{CLF} ).
- Latent heat gain follows a similar formula, focusing on moisture.

Shading and Heat Gain

Sun-shading devices, such as brise soleil, lower solar heat gain and reduce glare.
The Shading Coefficient (SC) quantifies the heat gain of glass in comparison to standard clear glass.

Reducing Cooling Loads

Strategies to minimize conductive heat gain include:
- Insulating walls and roofs to improve thermal performance.

Cooling Load from Lighting

Lighting heat gain is computed using the formula ( Q = \text{Btu/hr} \times \text{Ballast factor} \times \text{CLF} ), where the ballast factor varies by type of lighting.

Key Formulas

Sensible Heat Gain Equation:
- ( Q_{\text{sensible}} = \text{Number of people} \times 75 \text{W/person} )
Latent Heat Gain Equation:
- ( Q_{\text{latent}} = \text{Number of people} \times 55 \text{W/person} )

These study notes summarize critical insights on air conditioning systems, ventilation strategies, and thermal comfort considerations, important for building design and environmental control.

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Description

Learn about the principles of air conditioning and ventilation, including passive and active systems that enhance thermal comfort by adjusting temperature, humidity, and air movement.