Preparation And Characterization Of PVDF-based Heat Conductive Hollow Fiber And Its Heat Exchanger

Heat exchanger is one of the most basic equipment which is used to transforming and using energy in the industrial production process. Common metal heat exchangers have the disadvantage of poor corrosion resistance, poor pollution resistance, high cost and large weight; Graphite, ceramics and other materials heat exchanger have the disadvantage of fragile, bulky, poor thermal conductivity and low heat transfer efficiency; Though the heat exchanger which is made of expensive rare metal material is able to adapt to most working conditions, it has the disadvantage of high cost, be difficult to promote and be used only under certain conditions; Plastic heat exchangers has the shortcomings of bulky, thick pipe wall used to heat transfer, large thermal resistance, poor heat transfer, aging of plastic and a narrow temperature range. The key to increase the heat transfer performance of heat exchanger is improving thermal performance of heat conduction.To enhance heat transfer effects and expand the temperature range of using plastic heat exchanger, PVDF which has good temperature resistance is used as matrix and filled with graphite modification to prepare composite materials hollow fiber which has the advantage of small diameter, thin wall and good thermal conductivity in this paper. Also, using the thermal conductivity material to prepare shell and tube hollow fiber heat exchanger. The focus of study is formulation of composite materials, the influence and regularity of preparation conditions on the hollow fiber mechanical and thermal properties. Testing of "water - water" heat exchanging was made by using self-made heat conductive hollow fiber heat exchanger to research the influence and regularity of the heat exchanger performance by changing the fluid flow and flow.The results show that adding graphite and coupling agent, the thermal stability of complexes is increasing: the melting point of pure PVDF is 176℃, the melting point increased by adding graphite to 178℃, the melting point increased by adding graphite and the coupling to 178℃; Graphite played the role of nucleation by adding coupling agent, and promoted the crystallization of PVDF. When the graphite content is 9% and 15%, the optimal amount of coupling agent are 12% and 15%; when the content is less than 3%, the tensile strength and elongation of hollow fiber are as increasing as the increasing of graphite content; when the content is more than 3%, the tensile strength and elongation of hollow fiber are as decreasing as the increasing of graphite content.Through the testing of "water - water" heat exchanging, proving that adding graphite is helpful to improve thermal conductivity of PVDF-based heat conductive hollow fiber heat exchanger to a certain extent, But when the graphite content of more than 15%, the heat transfer performance of the hollow fiber is worse than that prepared by pure PVDF on the contrary. When the content of graphite is 3%, the heat transfer effect is the best; appropriately increasing the flow of fluids is helpful to improve the heat transfer effect; when the cold fluid goes though the tube of heat exchanger, the effect of heat transfer is better.The results show that graphite modified PVDF-based hollow fiber heat exchanger has the advantage of corrosion resistance, low cost, small size, light weight, easily handling and installation, the filling rate of heat conductive material in unit volume is high, anti pollution, high thermal conductivity, wide temperature range (at 120℃for long-term use).