Darrel LongOng Xin JieTeo Zheng Jie
Team
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Energy Efficiency(Ventilation)
1Lesson 1 Introductory Lecture
Lesson Objectives
Lesson 1 Introductory Lecture 2
Thermal Energy Transfer
Lesson 1 Introductory Lecture 3
Conduction
Definition:Transmission of molecular movement/thermal energy
through an object or between objects in direct contact
Magnitude of heat flow depends on• Area of section perpendicular to heat flow direction• Thickness of object(s)• Difference in temperature• Conductivity of material
Lesson 1 Introductory Lecture 4
Convection
Definition:Heat transfer from the surface of a solid body to a fluid
(gas or liquid) or the inverse through a cycle
Magnitude of heat flow depends on• Area of contact• Viscosity and velocity of the fluid• Difference in temperature between solid and fluid• Whether the fluid flow is laminar or turbulent
Lesson 1 Introductory Lecture 5
Radiation
Definition:Thermal energy that can be transmitted through space
from one body to another
Emission wavelength spectrum depends on:• Nature and on the temperature of the surface of the
body
Amount of radiant heat flow depends on:• Temperatures of emitting and receiving surfaces• Emissivity and absorptivity of these surfaces
Lesson 1 Introductory Lecture 6
Conduction, Convection and Radiation
Lesson 1 Introductory Lecture 7
CHALLENGE:Can you identify the processes of conduction, convection and radiation here?
• The higher the temperature, the more energy these atoms and molecules have, and the faster they move, hence occupying more space
RECAP:Hot objects occupy more space than cold objects despite having the same weight
As hot air takes up more space than cold air, hot air has a lower density hot air will rise, cold air will sink
Hot Air and Cold Air
Lesson 1 Introductory Lecture 8
Hot Air and Cold Air
APPLICATION• Where should ‘openings’ in a house be positioned?
• In the bottom and top of the house• Bottom for cool air to flow in• Top for hot air to rise out of
Lesson 1 Introductory Lecture 9
Cross-Ventilation
• Relies on wind to force cool exterior air into the building through an inlet (window, door, etc.) and to force warm interior air out of the building through an outlet (window, door, etc.).
Lesson 1 Introductory Lecture 10
Cross-Ventilation
Benefits:• Passive cooling; reduced reliance on air-conditioning• Allows for lighting of area
Case Study:• Edgedale Green in Punggol East• Carpark block• Sides of lift lobby
Lesson 1 Introductory Lecture 11
The End
• Any questions?
12Lesson 1 Introductory Lecture