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