| The sharp decline in energy and the worsening of the environment makes people realize the importance of energy conservation and environmental protection, all kinds of energy consumption of existing society, occupied a high proportion of heat exchange equipment. In view of the countries to the present status of high energy consumption and heat exchanger is widely used in industrial production, it is imperative to improve the heat transfer performance of heat exchanger. Tube and shell heat exchanger due to simple structure, large range of select material, adapt to high temperature and high pressure, low cost, is widely used in chemical, oil, energy, power, hospital, food, metallurgical department etc. Steam condensation is a kind of with phase change convection heat transfer process, in order to obtain higher heat transfer efficiency, and must taking the relationship between the design of heat exchanger and energy saving and reducing consumption into account. For the tube condensing heat exchanger, the process of steam flow in pipe, flow state of dropwise condensation change into film condensation,because of the condensate liquid film is formed in interior wall. And with the thickening of liquid film, which causes the thermal resistance increase and the heat transfer deterioration. Explore the tube side strengthening heat transfer in a tube condensing heat exchanger, how to reduce the section length of film condensation, utmost to maintain steam in a section of higher heat transfer coefficient or high efficiency in heat flow type has a important significance for tube and shell heat exchanger in improving the overall heat transfer, but also can help solve the defects of inefficient for tube and shell heat exchanger.This paper used condensation heat transfer test-bed with self-designed and built, and experimental study was carried on the tube and shell heat exchanger with intermediate drainage structure. The heat exchanger use water as cyclic fluid, by adjusting the different steam inlet pressure and controlling the condensate export temperature of the heat exchanger, and experimental study on process of condensation heat transfer for this kind of new type high efficiency tube and shell heat exchanger. A simulation software Fluent was used to simulate the distribution of heat exchanger shell side fluid of temperature and velocity and the condensation heat transfe for tube side fluid of condensation liquid and steam.Studies show that under this circumstance of formation stable liquid seal and drainage,with the increase open number of discharge pipe, the heat exchange amount, condensation heat transfer coefficient and the total heat transfer coefficient can be improved, but the heat transfer temperature difference decrease with the increase in the open number of discharge pipe; more leakage amount, more distinct trend of strengthening the heat exchangerperformance,more relieve heat transfer deterioration for heat exchanger caused by the fluid exists.Experiments confirmed that, different cooling water flow rate, corresponding to different number of the open discharge pipe, the inlet steam pressure of 0.17 Mpa, the temperature of 115.3 ℃ and cooling water flow of 0.058 kg/s, when you start the two discharge tube, the most obvious effect in improving the heat exchanger heat transfer deterioration, heat transfer coefficient increased 1.38%, the total heat transfer coefficient rises 2.82%; Steam inlet pressure is 0.17 Mpa, the temperature of 115.3 ℃ and cooling water flow of 0.06 kg/s, when you start the three discharge tube, the most obvious effect in improving the heat exchanger heat transfer deterioration, heat transfer coefficient increased1.66%,the total heat transfer coefficient rises 3.59%.Corresponding comparison was carried between experimental value and simulation value through the numerical simulation, the cooling water flow rate of 0.18 m/s, in situation of open 0, 1, 2, tube leakage respectively, the error range of the simulation value and experiment value is 12.4% ~ 13.9%; When cooling water inlet velocity of 0.18 m/s, 0.19m/s, 0.20 m/s, open a discharge tube, the error range of the simulation value and experiment value is 11.8% ~ 13.1%.In this paper, the experimental study and numerical calculation establishes the test basis for the future research and design of high-performance tube condensing heat exchanger and has a certain valuable for reference. |
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