Every summer, parents are warned not to leave children or pets in the car with the air conditioner off and windows rolled up. The interior of the car can quickly become much hotter than outside and lead to heat stroke or heat death. In humans, heat stroke occurs when the core body temperature reaches 40°C. Heat death occurs when the core body temperature reaches approximately 41°C. Heat transfer, Q,, from the air to a person can be modeled by:
where h is the heat transfer coefficient and A is the surface area of the person.
(a)Approximate how many minutes it would take to reach heat stroke and heat death in a closed car on a hot, sunny, clear day for a 13 kg toddler given the following assumptions and data
• The air inside the car heats up to 65°C instantaneously.
• The initial temperature of the person is 37°C.
• Surface area of the child is 0.70m2.
• Heat capacity of the human body is approximately 3.6kJ/(kg.°C).
• The person does not sweat.
• The heat transfer coefficient, h, is 15W/(m2.°C).
(b) Repeat the question for an 80 kg adult (surface area of 2.0m2).
(c) Times of 10–15 minutes are realistic for heat death for a child.2 How does your calculated answer compare? What are some weaknesses of the above model? How would improvements to the model affect the calculated time?