A wheel assembly includes a housing, a wheel, and a thermal conductive assembly. The wheel is disposed inside of an enclosure of the housing, and includes a first surface, a second surface, and a wavelength conversion layer formed on a coating area of the first surface and configured to convert wavelength of a light beam. The thermal conductive assembly includes a thermal conductive structure and a thermal conductive tube. The thermal conductive structure corresponds to an edge contour of the wheel and is disposed adjacent to an outer edge of the wheel. The thermal conductive tube is coupled to the thermal conductive structure and partially protrudes to an exterior of the housing for conducting heat generated by the wheel from the thermal conductive structure to the exterior of the housing. The distance between the thermal conductive structure and the outer edge of the wheel falls within 1-50 mm.
