Experimental Study On Preparation And Heat Transfer Performance Of Porous Stainless Steel Heat Exchanger Tube

304 stainless steel pipe is widely used in boiling heat transfer equipment due to its excellent corrosion resistance.The heat transfer efficiency has a great impact on the production efficiency of reboiler,porous surface tube can improve the boiling heat transfer coefficient effectively as well as lower boiling superheat required,which brings huge potential for further performance of the reboiler.Carbon steel pipe and copper alloy tube are commonly used in industry,and the surface porous tube of stainless steel is rarely seen,thus the development of stainless steel porous surface tube has important value in scientific and engineering files.This paper mainly from the following two aspects:(1)Determination of the best sintering process of porous heat exchanger tubes on stainless steel surface:In order to determine the sintering process parameters of porous layer on the surface of stainless steel,sintering experiments were carried out at different sintering temperatures by changing the powder type,particle size and the sintering atmosphere.The experiment results show that the sintering atmosphere is the key factor to the sintering structure and properties of base metal,vacuum sintering can ensure the sintering process going smoothly;With the increment of sintering temperature and holding time,the bonding strength of sintered structure increased,but the porosity shows a sharp decline;The particle size is not the main factor affecting the porosity,however,with the increasing of particle size,equivalent diameter of the pore will increase,while the sintered structure obtained from powder which mixing the particle size is able to get the sintered structure with wide distribution of pore equivalent diameter;The heat transfer test shows that sintered porous tube can effectively improve the boiling heat transfer coefficient and reduce the boiling temperature difference.The sintering process parameter was finally determined:keeping for about 15 minutes under the sintering temperature of 1000?1020? with vacuum sintering,it will obtain a sintered structure of 30%?60%porosity with the shear bond strength no less than 1.5KN/mm;(2)Analysis of heat transfer performance of sintered porous tube for industry:For the methanol aqueous solutionr solutions has smaller surface tension,it was chosed as boiling test medium.Results show that:Under the same temperature difference,the boiling heat transfer coefficients of the double enhanced tube reach 1.6?2 times of the light pipe;Under the same total temperature difference,the heat flux density of the double side strengthened tube is 1.4?1.6 times of the light pipe.The results show that the sintered porous tube can improve the heat transfer performance effectively.