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Ceramic Microchannel Heat Exchangers Seminar Report
A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. .The goal of enhancing heat transfer while minimizing pressure drops and reducingthe size and volume of energy conversion/thermal management systems has beenthe subject of intensive research for more than four decades. But growing energydemands, the need for increased energy efficiency and materials savings, spacelimitations for device packaging, and increased functionality and ease of unithandling have created revolutionary challenges for the development of highperformance, next-generation heat and mass exchangers. Current heat exchanger designs rely heavily on fin-and- tube or plate heat exchanger designs, often constructed using copper and aluminum. The strive for heat exchangers that are more compact and highly efficient has led to the development of microchannel heat exchangers.
The innovative microchannel heat and mass exchangers appear to be the mostpromising way to meet these challenges in thermal management. When properlydesigned and utilized, microchannels can distribute the flow precisely among thechannels, reduce flow travel length, and establish laminar flow in the channelswhile achieving high heat transfer coefficients, high surface area-to-volume ratios,and reduced overall pressure drops. These are among the major advantages ofmicrochannels for use in a diverse range of industries.
Recent developments in material sciences, in particular advances in ceramics and ceramic matrix composites open opportunities for new heat exchanger designs. Ceramic materials offer potentially significant advantages compared to metal alternatives. A major advantage is the capability to operate at very high temperature. Ceramics are also much more tolerant to harsh chemical environments than metals. Because the oxide ceramics can tolerate strongly oxidizing environments, it may be possible to remove certain fouling deposits by intermittently introducing oxygen to burn deposits. The performance of counterflow heat exchangers can be improved with low thermal conductivitymaterials that impede axial wall conduction. For ceramic microchannel heat exchangers thelow value of conductivity has negligible effect on its performance
CERAMICS AND CERAMIC MATRIX COMPOSITES
Solis materials used in heat exchangers can be divided into four categories- polymers, metals, ceramics and carbonaceous materials. Doubtlessly the most widely adopted material is metal due to its high thermal conductivity. Instead of depending upon monolithic materials composite materials can also be employed. Composite materials offer engineers an ability to create a limitless number of new material systems having unique properties that cannot be obtained using a single monolithic material. This approach to construction holds tremendous promise for future heat exchanger designs rather than selecting a single material, multiple materials may be selected and then tailored to meet the specific requirements of the application. Composite materials are constructed of two or more materials, commonly referred to as constituents, and have characteristics derived from the individual constituents. The constituent that is continuous and which is often, but not always, present in the greater quantity in the composite istermed the matrix. The second constituent is referred to as the reinforcing phase, or reinforcement, as it enhances or reinforces the properties of the matrix.
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