Dashboard Oven

Objective

Glass being a poor conductor conducts heat slowly and releases heat slowly thereby trapping it  much longer in an enclosed space – enough to bake cookies on a hot day.

Outcome

Students will comprehend the amount of radiant heat to be battled by air conditioners inside a glass building in order to cool occupants.

Requirements

A car parked nearby, infrared thermometer, tray, aluminium foil, readily available cookie dough.

Prerequisites

• A conceptual knowledge of heat transfer processes.
• Knowledge of how to conduct temperature measurement using infrared thermometer.

Procedure

Step 1. On a hot sunny day around 11 AM, take students to a car parked nearby , which is exposed to direct sunlight.

Step 2. Place the aluminium foil on the tray.

Step 3. Place cookie dough’s on the foil.

Step 4. Place the tray on the dashboard, beneath the windshield.

Step 5. With the help of an infrared thermometer, note the temperature reading of the tray for every 30 minute interval for 3 hours.

Step 6. After 3 hours, the cookies are ready to be served!

Step 7. Discuss 

• How the car can be compared to a glass building?
• Glass being a poor conductor of heat, conducts heat slowly but once heat enters such an enclosed space, it makes it very difficult for heat to get dissipated
• Air within the enclosed space which also takes time to heat up, once it is heated, needs vents to dissipate
• In the absence of which, the space undergoes greenhouse effect and ‘cooks’ the occupants
• HVAC systems therefore in a glass building have to consume enormous energy to cool such spaces
• When prevention of this amount of heating by building better thermal sensible buildings is a better route.

Table

Time Interval	Temperature (℃)
Initial time
30 mins
30 mins
60 mins
90 mins
120 mins
150 mins

References

Fairconditioning’s Building Physics presentation: