Different heat contents

Different specific heats

Different atomic structure

Different temperatures

Aluminium

Steel

Brass

Copper

Thermal resistance

Thermal coefficient

Thermal conductivity

Heat transfer coefficient

Better insulation should be put over pipe and better one over it.

Inferior insulation should be put over pipe and better one over it.

Both may be put in any order.

Whether to put inferior one over pipe or the better one would depend on steam temperature

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TxT

TxTxT

1/T