Experimental Study On Flow And Heat Transfer Characteristics Of Passive Residual Heat Removal Heat Exchanger

With the increasing of environmental pollution and energy shortage, countries around the world pay more and more attention to the clean and efficient nuclear energy, meanwhile, the security problem become the first thing to consider when we use nuclear energy. The passive residual heat removal system(PRHRS)is proposed under this circumstance and the passive residual heat removal heat exhanger(PRHR HX) is the key equipment to remove core decay heat in any emergencies.Knowing the thermalhydraulic phenomena ralated to PRHR HX is important to design the PRHRS, hence it is necessary to conduct researches about flow and heat transfer characteristic of PRHR HX.The experiment,based on the working environment of PRHR HX, studied the flow and heat transfer characteristic inside and outside the horizontal plain tube of 300 millimeters, when the two phase deionized water of high temperature and high pressure inside the tube flow through the tank filled with boiling water. This paper mainly studied the change of research objects including wall temperature inside and outside the tube, two-phase flow pattern inside the tube, pressure of test section, the cooling power and coefficient of heat transfer inside and outside the tube with the increasing of dryness, and analyzed the influence of pressure and mass velocity on them. Conditions with different pressure and different mass velocity including were compared.The results show that, keeping the other parameters constant, all the research objects are proportional to mass velocity and the dryness. Wall temperature, cooling power and the coefficient of heat transfer outside the tube are proportional to pressure, but on the contrary pressure drop and coefficient of heat transfer inside the tube varies inversely with pressure. Within the experiment condition, cooling power changes in the range of 5.9kW~12.4kW. Coefficient of heat transfer outside the tube in the boiling bank changes in the range of 3.8~5.88kW/(m2·K). Coefficient of heat transfer inside the tube changes in the range of 7.5~63kW/(m2·K). On the basis on classic formulas, experimental correlation for pressure drop, cooling power and coefficient of heat transfer applied to PRHR HX were obtained by a mulitivariable linear regression analysis. Under all experimental conditions, there are three kinds of flow pattern,including wave flow, slug flow and annular flow. With the increasing of dryness, different conditions have different flow pattern transition process. The transition is from slug flow to annular flow under the low pressure and high mass velocity, or from slug flow to wave flow under high pressure and low mass velocity.