| Energy plays an important role in human development and progress.With the development of economy and environment in people's life,the energy consumed in buildings has become the main subject of social energy consumption,together with transportation and industry.China's building energy consumption has reached 35%of total energy consumption at the end of 2018,in which the main energy consumption(i.e.,air conditioning and heating energy consumption)accounts for more than 60%of the total building energy consumption.The energy conservationin buildingdesign,the energy saving equipment,and the efficient energy supply systems in buildings are three important ways to reduce the energy consumption of air conditioning and heating systems.More and more attention has been paid to the use of energy-efficient building supply systems.The heat source tower heat pump air conditioning system,using the coolant below freezing point to transfer low temperature potential energy to high temperature potential energy,has high efficiency and a wide application prospect in energysaving.Previous studies mainly focused on the methods to improve system energy efficiency,but ignored the corrosive effect of coolants in the heat source tower on equipment.Therefore,this paper investigated the preparation and characteristics of new coolants in heat source tower heat pump air conditioning systems.The research work of this paper is mainly as follows:(1)By mastering the type and performance of the coolants and exploring the performance requirements of the coolants in the heat pump air conditioning system,the chemical raw materials such as sodium acetate trihydrate,magnesium chloride hexahydrate and ethylene glycol which have been widely used in the heat exchange field on the market were selected and dissolved in water according to different ratios.Six new kinds of coolants suitable for the heat source tower heat pump air conditioning system were prepared,and the thermal characteristics were tested and analyzed.(2)By the static and dynamic corrosion test methods,the corrosion behavior of the new coolants to the metal materials used in energy tower systems(copper H65,aluminum 3003 and 20#steel)has been studied in detail.In the static corrosion tests,the corrosion weight loss method and the polarization curve test method were used to investigate the corrosion properties of the developed 6 kinds of coolants to the metal materials used in energy tower systems(copper H65,aluminum 3003 and 20#steel).In the dynamic corrosion tests,the corrosion weight loss method was used to study the corrosion behavior of the metal materials used in energy tower systems(copper H65,aluminum 3003 and 20#steel)in different coolants(YH6830,BL3500 and HG3500)under different temperatures and velocities of f low.(3)The stress corrosion of 4340steel in the developed coolants containing Cl~-ion has been studied.The stress corrosion tendency of 4340steel in the high temperature water containing oxygen and Cl~-ion has been investigated and the related main influencing factors have been discussed in detail.The results indicate that the main failure mode of the 4340steel under tensile stress in the high temperature water containing oxygen and Cl~-ion is the oxygen induced stress corrosion under the combining actions of the loads and corrosive medium.Removing oxygen from the solution can effectively inhibit the oxygen induced stress corrosion and prolongs the life time of the 4340steel.(4)By the polarization curve test method,the inhibiting properties of the inhibitors on the corrosive behavior of the developed coolants used in energy tower systems have been studied.The inhibition effects of benzotriazole on copper H65 in coolant YH6830,cinnamic acid on aluminum 3003 in coolant BL3500,UHCI on 20#steel in coolant HG3500 have been investigated in detail.The related inhibition efficiency of these inhibitors has been obtained and the inhibition mechanisms have been analyzed and discussed. |
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