A method for determining flow velocity in a flow path, comprises defining a flow path for a fluid, the fluid flowing in a downstream direction that is opposite an upstream direction. A thermally-conductive element is exposed to the flow path. A known amount of heat is applied to a first portion of the thermally-conductive element and a sensed temperature is sensed at a second portion of the thermally-conductive element downstream of the first portion. The known amount of heat and the sensed temperature are used to determine a flow velocity of the fluid in the flow path.