As an important issue of energy-saving technology, heat storage material receives great attention of scientists in various countries and turns into an active field. To study and look for PCM with high thermal storage density, appropriate phase-transition temperature and good repetitiveness is the key of phase change heat storage. While study energy transfer in the phase change process of matters, we also should pay attention to their physical and chemical changes. Filter phase change heat storage materials according to project and product requirements, choose appropriate additive formulation and make cross-checking test to verify whether their physicochemical property maintains good repetitiveness after repeated use. For widely used hydrous salt phase change heat storage materials, the major problems now lies in their exothermic processes where relatively serious surfusion and phase separation exist and influence heat release stability and service lives of phase change heat storage materials. Compared with exothermic process, thermal storage process is much more stable. So phase change heat storage materials experiment and theoretical research mainly focus on exothermic process. An effective approach to resolve undercooling and phase separation problems is to add nucleating agent and thickener. 
    Heat pipe is a kind of element having high heat transfer property. It can transmit a lot of heat to a long distance through its small cross-sectional area without external motive power. Its working temperature range is -273℃to 1000℃. Heat pipe has many advantages that other heat transfer technologies do not have: excellent heat transfer efficiency and reliability, isolation, low resistance, small volume, controllability and so on. Therefore, heat pipe and heat pipe exchanger have been effectively applied in wider and wider fields. With the rapid development of industries, conflicts between increasing energy consumption and energy crisis are increasingly severe. With good property, heat pipe receives sufficient attention in the aspects of energy saving and new energy development. Heat exchanger being made up of heat pipes is used to recycle waste heat, which is applied in industry to save energy. 
    Now, study on application of heat pipe exchanger in the world has made achievements in recycling waste heat of industrial exhaust, heat dissipation of electronic components and instruments, in natural energy and chemical engineering and steps into the stage of finalized production and standardization. In refrigeration air conditioner industry, heat pipe and heat pipe exchanger better shows its superiority because of the small temperature difference between cold liquid and hot liquid, allowing them to be one of the foundation of reality technology which realizes low energy consumption, high efficiency, cold and heat source diversity, going green air-condition of refrigeration air conditioner. They are greatly promising in realizing the harmony between man and nature and sustainable development. 
    Based on experiments, study on thermal storage property and heat release property of hydrous salt crystal phase change material—barium hydroxide (Ba(OH)2•8H2O) under a relatively high temperature of 70℃～85℃ in the low temperature range where thermal storage temperature is relatively vacant. At the same time, design a multifunctional energy-saving heat pipe heat exchanger with latent heat storage by making use of PCM made from experiments, and making heat pipe as heating element.