In solar energy, air-conditioning, refrigeration, automotive, computer, desalination, pharmaceutical and food industries, and energy recovery applications, various types of polymer heat exchangers are used. Because of their ability to resist fouling and corrosion, the use of polymers in some applications offers substantially reduced weight, costs, water consumption, volume, space, and maintenance costs, which can make these heat exchangers more competitive in some applications over metallic heat exchangers. Because of the low thermal conductivity, usually, polymers are not considered as a material to construct heat exchangers, except for specific applications; but when the material properties of polymers and the research development on the polymer matrix composites (PMCs), these materials have considerable potentials to be used in the construction of heat exchangers in several applications. In addition, plastics are much simpler to shape, form, and machine; plastics have smooth surface which lower wettability resulting in dropwise condensation with higher heat transfer coefficient. ASTM (American Society for Testing and Materials) and ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) codes dictate minimal property requirements for materials used in this type of heat exchangers dependent on applications: thermal conductivity, specific heat capacity, maximum operating temperature, thermal expansion coefficient, density, ultimate tensile strength, and tensile modulus. A list of some commonly used polymers and their material properties are given in Table 13.1.1–6