Demonstration of a one-way flow of a rarefied gas induced through a pipe without average pressure and temperature gradients

A simple experiment is performed to demonstrate that a one-way flow of a rarefied gas can be induced through a pipe without average pressure and temperature gradients by devising the shape of the pipe. A one-way flow is found to be induced through a pipe consisting of two circular pipes of different diameters connected and heated at their joint in the middle part of the pipe. The flow is from the thinner pipe to the thicker. In a pipe of a uniform diameter, no one-way flow is induced even when it is heated at a position away from the middle of the pipe.