Research On The Cold Proof Design Of The Upper Facilities Of Polar Ships

Polar ship is a special ship sailing in the extreme environment.The upper facilities are easy to freeze and ice,which cause great harm to the safety of equipment and personnel.Considering the reliability of polar environmental protection and cold protection measures,electric tracing is usually used for the upper facilities of polar ships.Due to the inapplicability of existing codes,there are serious unreasonable heating quantity.The accurate and reliable prediction model of convection heat transfer coefficient is of great significance to the calculation of heat balance of upper facilities,which can guide the more reasonable design of tracing heat and cold,effectively improve the cold resistance capacity of polar ships and accelerate the process of polar exploration and development in China.Based on the theory of hydrodynamics and heat transfer,the complex polar ship upper facilities are simplified into flat,treading and circular tube components.The convection heat transfer coefficient of different components is studied and analyzed by combining theoretical analysis,indoor experiment and numerical simulation.The theoretical analysis of the heat transfer theory of flat and circular tube members is made,and the difference between the two heating modes is clarified.The existing convection heat transfer theory of constant wall temperature heating method is not suitable for the electric tracing and cold proof design of polar ships.Due to the complex geometry of the stepping member,there is still no theoretical and empirical formula for the convection heat transfer coefficient.A platform for convection heat transfer is built in the low temperature laboratory,which can simulate the polar environment.The accurate measurement of the convection heat transfer coefficient is realized in the wind speed range of 0～15m/s and the temperature range of-40～0℃.The influence of wind speed is more significant.The prediction model of the convection heat transfer coefficient of flat plate and step is obtained based on the fitting of experimental data.The increase of wind speed and temperature also increase the convective heat transfer coefficient of the circular tube.When the temperature is higher than-30℃,the wind speed is the main factor affecting the convection heat transfer of the circular tube;When the temperature is lower than-30℃,the influence of temperature on convection heat transfer of circular tube increases significantly,and the influence of wind speed remains unchanged.The convection heat transfer coefficients of three components under experimental conditions are calculated by fluent finite element software.The numerical simulation of the high wind speed which can not be achieved under the experimental conditions is carried out,and the applicability of the model in the range of 0～40 m/s is verified.Based on the numerical simulation,the prediction model of convection heat transfer coefficient of circular tube in temperature range of-40～-30℃ and temperature range of-30～0℃ is obtained;The average error between the calculated results and the measured results of the prediction model is 8.9%.The model of heat transfer coefficient prediction and the developed software can realize the fast calculation of heat balance,which can provide a useful reference for the design of electric tracing and cold proof for the upper facilities of polar ship.