Thermal spray fabrication of porous heat exchangers and heat pipes

多伦多大学先进涂层技术中心（CACT）利用热喷涂技术开发高效热交换器和热管。热交换器的效率可以通过在热交换器管的表面粘接多孔钢丝网、穿孔板或金属泡沫来提高，从而增加传热面积。CACT开发了一种粘合技术，使用电弧喷涂方法将金属网、泡沫和穿孔板粘合到管道上。我们将在各种应用中使用高效热交换器，包括废热回收、燃气加热器和工业烤箱。热管是一种广泛用于将热量从一个地方快速传递到另一个地方的装置。传统的热管是由中空的铜管组成的，铜管的内表面有一层多孔层，通常是由烧结一层铜粉制成的，铜粉的作用是充当饱和挥发性液体的灯芯。烧结芯易碎，限制了热管的尺寸和形状。我们使用火焰喷射系统将铜或铝粉喷射到铜基板上，并充分降低颗粒速度和温度，使颗粒仅部分相互融合，从而形成多孔芯。能够同时喷射皮肤和多孔灯芯将彻底改变热管的制造，使热管变得非常薄，表面弯曲，覆盖非常大的区域。***本方案用于换热器和热管用多孔介质的传热和流体流动的实验研究。该项目的长期目标是利用热喷涂技术开发紧凑型热交换器和热管。这将大大降低制造成本，允许新的设计和传热设备的形状，并促进能源效率和废热回收。***本研究的短期目标是：***1)测量通过金属泡沫、穿孔板和金属丝网的对流换热。***2)测量具有复杂内部结构的激光烧结金属通道的对流换热。***3)建立通过各种多孔介质的流动模型。***4)使用这些模型来优化热交换器的设计，并根据各种应用进行扩展。***5)开发制造不同形状和尺寸的热交换器的制造技术。***6)观察毛细管驱动流体通过热喷涂铜芯或铝芯的流动情况。***7)测量浸渍在热喷涂技术制成的多孔层中的液体沸腾时的传热。***8)开发热喷涂金属热管的传热模型，并利用它们来优化设计

The Centre for Advanced Coating Technology (CACT) at the University of Toronto has used thermal spray technology to developing high efficiency heat exchangers and heat pipes. Heat exchanger efficiency can be improved by bonding porous wire meshes, perforated sheets, or metal foams to the surface of heat exchanger tubes, increasing the area for heat transfer. CACT has developed a bonding technique, using a wire-arc spray coating method, to bond metal meshes, foams and perforated sheets to tubes. We will use high-efficiency heat exchangers for a variety of applications, including waste heat recovery, gas heaters and industrial ovens.***Heat pipes are devices that are widely used for rapid transfer of heat from one location to another. A conventional heat pipe consists of a hollow copper tube that has a porous layer on its inner surface, usually made by sintering a layer of copper powder, which acts as a wick that is saturated with a volatile liquid. Sintered wicks are fragile and limit the size and shape of the heat pipe. We have formed porous wicks by spraying copper or aluminum powder using a flame spray system onto a copper substrate and decreasing particle velocity and temperature sufficiently so that the particles fuse only partially with each other. The abilty to spray both the skin and porous wick will revolutionize the manufacture of heat pipes and will allow them to be made very thin, with curved surfaces, and covering very large areas. ***This proposal is for an experimental study of heat transfer and fluid flow in porous media used for heat exchangers and heat pipes. The long term objective of this project is to develop compact heat exchangers and heat pipes using thermal spray technology. This will greatly reduce manufacturing costs, allow new designs and shapes for heat transfer equipment, and promote energy efficiency and waste heat recovery. ***The short term objectives of the study are:***1) Measure convective heat transfer through metal foams, perforated sheets and wire meshes.***2) Measure convective heat transfer in laser sintered metal channels with complex internal structures. ***3) Develop models for flow through a variety of porous media.***4) Use the models to optimize design of heat exchangers and scale them for a range of applications.***5) Develop fabrication techniques for making different shapes and sizes of heat exchangers.***6) Observe capillary driven fluid flow through thermally sprayed copper or aluminum wicks.***7) Measure heat transfer due to boiling of liquids impregnated in porous layers made by thermal spray techniques.***8) Develop models for heat transfer in thermally sprayed metal heat pipes and use them to optimize designs.**