Numerical Simulation Of Thermal Load Of Water And Wastewater System In C919 Airplane

The water and waste water system is an indispensable airborne system on the civil trunk airplane.Its stable operation is closely related to ensuring the water supply for passengers and aircrew on board.Its main components include a clean water tank,a waste water tank,the clean water supply pipeline,the waste water transport pipeline and the discharge pipeline and so on.Because the water supply pipeline is often laid close to the airplane's skin,the water tank and wastewater tank are both located in the pressurized area at the tail of the aircraft without temperature control.In cold weather or in the state of cruise,the pipeline filled with water is at risk of ice block problem or even cracking.At present,the research on anti-icing of this system is still at the initial stage in China.Aiming at this problem,the thermal load analysis of aircraft water and wastewater system are carried out in this paper.The main research work is detailed as follow.1)Numerical simulation is used for transient calculation of pipeline cooling process in the water and waste water cabin in cruise state or staying on ground respectively.The dangerous positions A(cruising)and B(staying)with the fastest cooling speed in the pipeline were determined.The proportion of convection and radiation heat transfer,respectively accounted for 67% and 33%,of total heat transfer at position A were quantitatively calculated.Convection and radiation heat transfer contribute respectively 83% and 17% of total heat transfer at position B.2)For two basic working conditions,the influence of Mach number,cabin exhaust flow rate,cabin exhaust temperature on pipeline heat transfer in cruise state and the influence of environment temperature on pipeline heat transfer when staying on ground were studied.The comparison shows that the Mach number is the most influential factor in the cruising state: the total heat flux increases by 37.19% when Mach number drops by 0.12.On the ground,when environment temperature decreases from 233.15 K to 243.15 K,the total heat flux increases by 28.35%.According to the above research,two innovative advances have been made in this paper:1)The proportion of convection and radiation heat transfer in different positions of water and waste water system is revealed,and curve of the thermal load variation at the position with the fastest cooling speed is obtained.2)The influence of multiple factors on the pipeline heat transfer is studied and the most influential factor as well as corresponding effect law is determined.