The invention relates to the use of a layer consisting of a composition comprising a copolyamide of formula X/10.T/Y for transporting a heat transfer fluid in a vapor compression circuit, wherein: X represents either the residues of an aliphatic amino acid comprising between 8 and 18 carbon atoms, or a lactam, or the unit X1.X2 representing the residues resulting from the condensation of an aliphatic diamine comprising between 6 and 18 carbon atoms and a (cyclo)aliphatic diacid comprising between 6 and 18 carbon atoms; 10.T represents the residues resulting from the condensation of a decanediamine and terephthalic acid; and Y represents the residues resulting from the condensation of an aliphatic diamine comprising between 9 and 14 carbon atoms and an aromatic diacid, Y being different from the unit 10.T; the molar proportion of 10.T units being higher than 0%.