| The thermal performance of the cargo containment systems(CCSs)not only causes the change of the temperature field and the boil off rate(BOR)of CCSs,but also is directly related to the economy and safety of the LNG carrier transportation.According to the cryogenic characteristics of LNG carrier,a novel expanded water-repellent perlite has been developed for the CCSs,which is a kind of treated insulation materials by coating hydrophobic membrane onto the surface of itself to change the physical performances.Moreover,the thermal conductivity of thermal insulation is directly related to long-distance transport and storage of LNG.Therefore,a double-sided guarded hot plate apparatus(GHP)is specifically designed and fabricated for the measurement of thermal conductivity of insulation specimens operated down to liquid nitrogen temperature.Experiments to determine the thermal conductivity of expanded water-repellent perlite are carried out to build a database of the thermal conductivity of the insulation materials used in CCSs.Meanwhile,the influences of thermal performance attenuation of the expanded water-repellent perlite on the variation of the temperature field and the BOR of CCSs are discussed.The main research works are as follows:Firstly,expanded water-repellent perlite conformed to GTT112 k is prepared by optimizing the ratio of hydrophobic agent.The mechanism of hydrophobic and swelling of expanded perlite is analyzed.the change of the particle sizes and the density of the perlite are analyzed during theexpansion process based on the heat transfer theory.Secondly,a double-sided GHP is specifically designed,fabricated and constructed for the measurement of thermal conductivity of insulation specimens operated down to liquid nitrogen temperature(-196℃),at different controlled pressures from 0.005 Pa to 0.105 MPa.The specimens placed in this apparatus are 300 mm in diameter at various thicknesses ranging from 4 mm to 40 mm.The apparatus is different from traditional GHP in terms of the total structure layout and heating method.The measurement methods of the temperatures,the input power,the meter area and the thickness of the specimens are given.The structure design,measurement methods,data acquisition system and uncertainties for the measurement are also discussed in this paper.In addition,the water absorption of the expanded water-repellent perlite are compared with that of the ordinary expanded perlite,which is not damaged or damaged.an experimental study has been carried out to measure and evaluate the thermal conductivity of the expanded water-repellent perlite for the LNG CCS under the density,water contents and breakage ratios at various temperatures,which contribute to build an experimental database used in CCS.Then,the back propagation neural network model and the generalized regression neural network model are used to analyze the influence weight of the temperature,moisture content and breakage ratio on the thermal conductivity of the expanded water-repellent perlite.The neural network correlation coefficient R,root mean square error,the mean square error and the error mean value are used to determine the sensibility of the two different expanded water-repellent perlite.Furthermore,the physical model and heat transfer model of the CCSs of LNG carrier are established,and the numerical simulation is carried out by ANSYS software to obtain the temperature field distribution and BOR value.The main works are as follows:(1)The heat transfer behaviors for the cargo tank containment system are analyzed.(2)The accuracy of themathematical model is verified by comparing the results of the finite element model with the experimental data.(3)Base on the thickness of different insulation layers and adiabatic performance degradation,the law of temperature field distribution and BOR of the cargo containment system is analyzed,which can provide the references for the design of LNG cargo tank insulation structure. |
