Multiscale study of thermal conductivity of boron nitride nanosheets/paraffin thermal energy storage materials

•Effects of layer number and size of h-BN on TC are studied.•TC of the encased h-BN is lower than that of the suspended one.•TC of composites is controlled by TC of h-BN and ITR at n ≤ 15 and by the aspect ratio of h-BN n ˃ 15.•A high layer number of h-BN with a high size results in a high TC of composites.