“…Eight years later, it was reintroduced by Wei et al [14] with the thermal resistance improved up to 0.09°C/ Wcm 2 . Recently, DL-MCHSs were continuously investigated by other groups of authors such as Hung et al [15][16][17], Leng et al [18][19][20], Lin et al [21], Rajabifar et al [22], Wu et al [23], and Zhai et al [24]. The channel inlets of the upper layer of a DL-MCHS were designed on the top of the channel outlets of the lower layer; therefore, the temperature in the lower-layer-outlet region would be reduced compared to that of the single layer leading to the temperature on the bottom wall being more uniform.…”