| Heating furnace is one of the heat consuming equipment widely used in crude oil transportation and petroleum refining industry.Its energy consumption level is very important to the economic development of industrial production.It is not enough to evaluate the performance of heating furnace from the perspective of energy conservation to meet the needs of scientific theory research and social production application.Therefore,the research on exergy transfer process of heating furnace from the perspective of energy quality is of great significance to energy saving and consumption reduction of heating furnace.Application in the oil industry's most popular form of tube type heating furnace as the research object,the mathematical model on the basis of the regional method,monte carlo method is used for heating furnace for solving all the regional radiation exchange area,avoiding the complex multiple integral calculation,through the main variable correction method to solve the area energy balance equations to determine the temperature distribution in the hearth;The flue gas temperature and tube wall temperature under different blackness of furnace wall and different convective heat transfer coefficient were calculated.The results show that when the blackness of the furnace wall increases from 0.6 to 0.9,the average temperature of the furnace tube wall increases,and the maximum temperature increases by 11?.When the convective heat transfer coefficient decreases from 85.9W/m~2·K to 63.41W/m~2·K,the average temperature of the furnace tube wall decreases,and the maximum temperature decreases by 10.4?.By establishing the exergy balance model of the heating furnace energy system,and based on the evaluation criteria of exergy analysis,it is concluded that the highest proportion of exergy loss in the heating furnace system is exergy loss in the heat transfer process,and the exergy loss in each link of the heating furnace is as follows: Exergy loss in heat transfer > cooling exergy loss in combustion products > exergy loss in combustion reaction > exergy loss in heat dissipation >exergy loss in smoke exhaust > incomplete combustion exergy loss.After analyzing the influencing factors of exergy efficiency of heating furnace,it was found that excess air coefficient,smoke exhaust temperature and outer surface temperature of furnace body were inversely proportional to exergy efficiency.The exergy transfer model of the tubular heating furnace was established based on the principle of 1-N type heat exchange chain,and the reduction rate of exergy flow density in the heat transfer process was calculated according to the evaluation criteria of exergy transfer.The results showed that exergic potential of radiant furnace tube was larger than that of others in the heat transfer process of heating furnace.The influences of blackness of furnace wall and convective heat transfer coefficient on exergic transfer of radiant furnace tube under steady-state conditions were deeply discussed.As the blackness of the furnace wall increased from 0.6 to 0.9,the highest exergy flow density of the outer wall of the furnace tube increased from 46.3k W/m~2 to 68 k W/m~2,and the highest exergy flow density of the inner wall of the furnace tube increased from 30.51 k W/m~2 to 43.22 k W/m~2.As the convective heat transfer coefficient decreased from 85.9W/m~2·K to 63.41W/m~2·K,the highest exergy flow density of the outer wall of the furnace tube decreased from 68 k W/m~2 to49.5k W/m~2,and the highest exergy flow density of the inner wall of the furnace tube decreased from 43.22 k W/m~2 to 29.64 k W/m~2.The exergy transfer calculation software of tubular heating furnace was developed with the help of Visual Basic platform,which can realize the calculation of radiation heat transfer,convection heat transfer,exergy analysis and exergy transfer of heating furnace,providing theoretical basis and technical support for the scientific energy saving and efficient operation of heating furnace in engineering. |
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