The device has a refillable reservoir that holds the naphtha liquid. The fuel moves into a glass fiber burner, which absorbs the fuel and allows it to burn slowly without producing a flame. Oxygen reaches the burner through the holes on the cap at the top of the device. As the fuel is burned, heat is conducted to the metal casing of the device.

Question

When the hand warmer is tested, it becomes too hot and uncomfortable to hold. How could the device be modified to solve this problem?
A.
by replacing the glass fiber burner with a material that does not soak up liquid fuel
B.
by attaching a covering to reduce the amount of oxygen entering the device
C.
by increasing the size of the fuel reservoir so that it can store more liquid fuel
D.
by using a fuel that is more flammable than naphtha so that the fuel can be used faster

Answer 1

To address the issue of the hand warmer becoming too hot and uncomfortable to hold, the best modification would be:

B. by attaching a covering to reduce the amount of oxygen entering the device.

This option would limit the oxygen supply to the burner, thereby reducing the rate of combustion and, consequently, the heat produced. The other options would not effectively solve the overheating problem:

• A would prevent the liquid fuel from being absorbed and likely stop the device from functioning properly.
• C would actually allow the device to burn for a longer period, potentially increasing the heat output over time.
• D would result in a quicker burn and likely make the overheating problem worse, rather than resolving it.

Thus, adding a covering to reduce the oxygen supply is the most effective modification to solve the overheating issue.