Rarefied gas flows through a curved two-dimensional channel, caused by pressure or temperature gradients, are investigated numerically by the use of a macroscopic equation of convection-diffusion type. The equation, which was derived systematically from the BGK model of the Boltzmann equation and diffuse-reflection boundary condition in a previous paper, is valid irrespective of the degree of gas rarefaction when the channel width is much shorter than the scale of variations of physical quantities and curvature along the channel. Special attention is focused on variants of the Knudsen compressor that can produce a pressure raise by the effect of the change of channel curvature and periodic temperature distributions without any help of moving parts.