Study On The Heat Exchange Processes And The Growth And Decay Processes Of Shore Ice In Nenjiang (Qiqihar Section)

In the middle and high latitudes of China,river ice,lake ice and reservoir ice often occur in winter.The growth and decay processes of ice cover will interfere with the surrounding agricultural engineering and ecological environment.In the Nenjiang River?Qiqihar section?,there will be fixed shore ice growing along the coast in winter.Analysis of the evolution characteristics of the shore ice and the heat exchange processes can provide reference and help for the future shore protection project and water ecosystem.This study explores the mechanism of climate change in response to the long-term coastal ice and ice data of Nenjiang?Qiqihar section?,and analyzes the evolution trend of shore ice under temporal and spatial changes.In the winter of 2016?-2?017,the prototype experiment of shore ice production and elimination was carried out in Nenjiang?Qiqihar section?,and the ice evolution trend,the ice?water?temperature field change process,the ice temperature response temperature lag mechanism and the ice water heat flux conduction characteristics were obtained.Through the simple degree-day method and the traditional degree-day method to fit the production and elimination process of the shore ice of Nenjiang?Qiqihar section?,a reasonable ice thickness prediction model was selected.The low temperature laboratory was used to explore the static ice model test to reproduce the wild ice layer production and elimination process.Method and key parameters,and analyzed the heat exchange process between gas-ice-water.I hope this paper can provide reference and help for the thermodynamic study of shore ice?static ice?.The conclusions are as follows:?1?The temperature in Nenjiang?Qiqihar section?has gradually warmed up?0.35 ?/decade?;the wind speed shows a gradual decrease?0.19 m/s/decade?;from the ice data from 1983 to 2013,it was found that the freezing period of the river ice was not shortened year by year.The freezing period was 125 d-165 d,and the average freezing period was 149 d;both winter shore ice and river ice have a uniform growth first,and after reaching the limit ice thickness,they remain unchanged for a short time,and then accelerate the evolution of melting;under the ice,the water flows slowly,mainly by thermodynamics,and the ice thickness grows faster,which is similar to static ice.The ice thickness of the shore ice?92-127 cm,average: 106.8 cm?is larger than that of the river ice?79-117 cm,average: 101.3 cm?;the simple degree-day method?stefan formula?is used to link the cumulative temperature and ice thickness growth process.The average ice thickness growth coefficient a of Nenjiang?Qiqihar Section?bank is 2.29 cm·?^-0.5·d^-0.5;the ice thickness can be rapidly calculated by using this growth coefficient and temperature data.?2?Through the 2016?-2?017 prototype test,it was found that: in the Nenjiang River?Qiqihar section?,the winter ice layer grows at a rate of 1 cm/d;when it grows to about 85 cm,it maintains a fluctuation above and below this thickness,and then rapidly melts at a rate of 1.2 cm/d;affected by the increase in solar radiation intensity,the ice layer has already undergone ablation before the temperature has returned to normal temperature;during the freezing period,the vertical ice temperature field?0-100 cm?is in inverse temperature distribution,and the vertical?0-160 cm?water temperature is between 0 ?-0.6 ?;the temperature of the ice layer at different depths at the same time has a hysteresis in response to temperature changes?depth: 0 cm⁵0 cm,lag time: 1.74 h-16.79 h?;the ice temperature change during the freezing period has a good correlation with the temperature change.With the increase of ice thickness?0-50 cm?,the correlation coefficient decreases gradually;the ice layer heat flux is 0-115 W·m^-2,while the heat flux of the water layer is only 0-3.4 W·m^-2;the application of the simple degree-day method and the traditional degree-day method can describe the ice thickness growth process in the study area.According to the fitting effect of the two on the early stage of ice formation,it is recommended to use the simple method to compare the Nenjiang?Qiqihar section?;the shore ice growth process was calculated,and the ice growth coefficient a was 3.3 cm·?^-0.5·d^-0.5.?3?Based on the in-situ observation data of the Nenjiang shore ice,the initial attempt to explore the feasibility and method of recreating the prototype shore ice production and elimination process in the indoor model test.In this study,the indoor simulation test of the static ice production and elimination process was carried out and the key parameters were determined.According to the similarity of the model test,the key parameters to be considered in the indoor model test were the geometric scale C_l,the temperature scale C_T,and the time scale Ct.And laboratory correction coefficient C_?;by establishing the similarity criterion of freezing degree,the similarity principle is used to derive:?C_l/C_??2 = C_TC_t;based on the process of solar radiation variation in prototype test,the indoor simulation test is compensated by reasonable illumination,under the condition of determining C_l =1:9 and C_T=1.5:1,the correction coefficient C_? alpha of the test room is 0.55,the ice thickness growth coefficient is 1.76,and the time ratio is Ct=1:37.5;based on the same parameters in the model test,the ice surface was compensated for illumination at the later stage of ice thickness growth.Compared with no light,the illumination compensation could better simulate the process of field ice production,no light ice thickness growth coefficient ? is 1.96-1.98,light ice thickness growth coefficient ? is 1.74-1.75,approximate to the prototype value ??1.76?behind the scale of the model;according to the process of prototyping temperature and solar radiation,temperature control curves were designed based on the same cumulative negative temperature principle to compensate for reasonable lighting.The result that both the ice thickness growth coefficient and the ice thickness growth and elimination process were similar to the prototype was obtained;in the future research,it is necessary to further improve the theory of illuminating heat transfer to achieve the purpose of simulating solar radiation in the field.?4?Through the indoor heat exchange model test of shore ice?static ice?,the influencing factors of heat exchange process between air-ice-water are analyzed.It is found that under the same cooling conditions,water with lower initial water temperature is more likely to form stable ice surface;the vertical ice temperature is also in inverse temperature distribution,and the vertical water temperature and the adjacent water layer temperature gradient are slightly larger than the prototype test;in the indoor test,different ice layers respond to temperature changes with hysteresis.Because the ice layer is thin,the surface of the ice layer is smooth,and the maximum temperature lag time is only 0.25 h;the ice layer heat flux(0^-200 W·m^-2)is greater than the heat flux in the prototype test ice layer;after the indirect illumination is turned on,the ice temperature responds to the light to a greater extent than the temperature response;under the ice frosting condition,the growth rate of the ice layer thickness is smaller than the ice thickness growth rate under the smooth condition of the ice surface;in the future,it is still necessary to further investigate the effects of wind speed,water depth,microbes in the water,river environment and underwater soil on the heat exchange process of shore ice?static ice?.