Question

In order to heat air it is important to increase the area of contact between the air and the surface gathering the heat

Answer 1

Yes it is correctly true.

Heat from source escape from its surface area and disappears in surrounding atmosphere.

For example take a candle

ignite it

You'll feel More heat near to it as compared to little bit far.

This means heat spreads in atmosphere with respect to distance from source.

thus it is better if surface area between air and surface gathering heat.