Research And Cryogenic Test On Mock Up Tank Insulation System Of Independent Type B LNG Carrier

Liquefied natural gas(LNG)carriers are of great importance to the transport vehicles for transnational natural gas trade,during the navigation of LNG carriers,the huge temperature difference between the inside and outside of the cargo tank will lead to a constant heat flux from external environment into cold liquid cargo and result in the loss of liquid cargo.In the meantime,the vaporized cargo gas will make tank pressure increase and may become a threat to the safety of navigation.So the thermal insulation performance of the cargo tank insulation system is of great importance to LNG carriers.The boil off rate(BOR)is the key parameter to evaluate the insulation performance of LNG carriers,so doing research and cryogenic test on the insulation performance and BOR of new type LNG carrier is vital to examine the insulation technology and insulation system design of new LNG carriers.In this paper,an independent type B LNG carrier mock up tank with 47.823 cubic meters was chosen as the research target,and study focused on the insulation performance of mock up tank was mainly conducted.(1)Firstly,for the insulation material of mock up tank,its effectove thermal conductivity was measured under cryogenic conditions by using a special test unit.(2)A simplified heat transfer model and a convection calculation method of mock up tank were established.And the BOR calculation under different conditions was done by the combination of theoretical calculation and Fluent.(3)Building the cryogenic test system and completed the selection of test equipment,arrangement design and insulation of sensors,design of piping system and test procedures,design of data collecting and controlling system and finally the BOR correction principles.(4)During the cryogenic test,data of temperature distribution and BOR of mock up tank was obtained,and after BOR correction and uncertainty calculation,the final BOR of independent type B LNG carrier was obtained to verify if it have met the original design requirement of BOR.The relevant achievement could be concluded as follow:(1)By the use of the special test unit,the effective thermal conductivity of insulation material from cryogenic condition to normal temperature had a range of 0.0139~0.025 W/(m·K).(2)A complete cryogenic test system of mock up tank was built,including the mock up tank system,cryogenic pipe system and data collecting and controlling system.(3)According to the final results of cryogenic test of mock up tank,the BOR value calculated by Fluent was closer to the BOR result obtained in the test,and the insulation performance of independent type B LNG carrier has met the original design BOR requirement of 0.1%/d.