Status of the Development of a Vapor Chamber with Phase Change Material Based Wick Structure
A traditional vapor chamber operates very similar to a heat pipe, and usually consists of a sintered wick structure, a working fluid in saturation state, and an envelope that serves as mechanical structure. These devices are typically used in high heat flux applications, where effective heat spreading is crucial. The Phase Change Material (PCM) vapor chamber is based on similar principles, except that the design has been altered with innovative features to support thermal storage requirements. The PCM vapor chamber consists of a packed bed of microencapsulated PCM particles surrounded by a two phase working fluid. The microencapsulated PCM particles serve two functions. First, they act as a highly effective thermal storage medium. Second, the packed microencapsulated PCM particles serve as a wick structure for capillary pumping of the two phase working fluid for effective liquid return. In comparison to the traditional approach of designing PCM heat sinks, the PCM vapor chamber eliminates the need for embedding high thermal conductivity metal fins or carbon foams to transfer heat into bulk PCM, which typically consumes at least 50% of the system mass. In addition, the PCM vapor chamber can serve as either a stand alone thermal capacitor or a dual thermal capacitor/heat exchanger capable of heat transfer from surface to surface. This paper describes the novelty of the concept and the status of the development of the vapor chamber with PCM based wick structure.