Theoretical And Experimental Research On Heating Performance The Injecting Heater With Tapered Mixing Space

At present, energy demand is rising dramatically for human life and industrial production. But fossil resources are being exhausted. Facing this contradiction, saving energy and reducing consumption is imminent in thermal power plants. It is one of the important task of energy saving and emission reduction to reduce exergy loss of lower pressure surface heat exchanger in the low-pressure of feed water heater system and to enhance operation efficiency and thermal economy. In the process of the heat exchanger for the low-pressure feed water heater system in thermal power plant, the heating performance is been restriction on the variable condition operation characteristic of the system. Therefore, the development and research a new heater, which has high heating efficiency, high heat transfer coefficient, suitable for low-pressure feed water heater system of variable condition characteristics. It can not only save energy, and has important academic value and industrial application foreground.The injection heater application in the low-pressure feed water heater system is restricted by the variable load operation in thermal power plants. So better matching ability of variable load operation, better heating performance and lower exergy loss of the two-phase mixing are the starting point. Based on the study of injection heater at home and aboard, this paper presents the injection heater with tapered mixing space and determines the model of boost pressure and heating. And this paper presents the best axial size expression of the tapered mixing space and the exergy efficiency analysis model of the device. The size of the device is determined by the conditions of laboratory and application in the thermal power plant. The ejector & heating performance and exergy efficiency of the injection heater are studied by theoretical and experimental analysis. Based on theoretical and experimental research of the injection heater with tapered mixing space, this paper presents the ejection heater system by multistage boost by EEDM and similarity criteria for replacing the surface heat exchanger feed water system. The comparative analysis of the alternatives feasibility and changes of thermal economy in 660MW and 300MW units have been done.The results of the study indicate that the best axial length of the tapered mixing space is related to the density ratio and velocity ratio of the two-phase flow. The best axial length and the mixing space throat have a linear relation.The injection ability of the device is better. It can be used in the last stage feed water heater and could stabilize operation. The change of the steam mass with variable condition is littler at the fixed steam pressure in the experiment. Improving the steam pressure and inlet temperature is conducive to the outlet water temperature rise. At the steam pressure 0.2 MPa the outlet water temperature rise is 50℃or above, and largest outlet water temperature reaches 106℃or above. The device can completely achieve enthalpy rise of various levels low-pressure heaters and water temperature requirements into the deaerator in thermal power plants.Based on the theoretical and experimental analysis, the exergy efficiency of the device is related to inlet water pressure and temperature, steam pressure and injection coefficient. The theoretical calculation and experiment results differ less than15% and laws are consistent.Combined with theoretical and experimental analysis, the application feasibility of the injection heater with tapered mixing space, which uses in 300MW units or above, has been determined by EEDM and similarity criteria. The thermal economy of 660MW unit can improve 0.246% and the thermal economy of 300MW unit can improve greatly 0.22% by using the ejection heater system with multistage boost.