Chapter 14, Problem 17Q

To determine

To Explain:

Goose down sleeping bags and parkas are often specified as so many inches or centimetres of loft, the actual thickness of the garment when it is fluffed up.

Explanation of Solution

Introduction:

An insulating material's resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value - the higher the R-value, the greater the insulating effectiveness.

The loft value is similar to R value of insulator. The thickness of conductor is proportional to loft value. When garment is fluffed up, the is bounded inside the garment’s structure. As we know, the thermal conductivity of air is low. Therefore, it makes the garment as good insulator.The thermal conduction rate varies inversely with thickness. As the garment is thick which means it has low thermal conduction rate and body loses heat at a slow rate.