Research on U-tube Heat Exchanger with Shape-stabilized Phase Change Backfill Material

Fluent software was used to simulate the heat transfer performance of the U-tube heat exchangers with backfill materials of shape-stabilized phase change materials (PCMs) and crushed stone concrete in this paper. The shape-stabilized PCMs refer to a mixture of decanoic acid and lauric acid that the mass concentration of decanoic acid is 60% with10% silica and 6% expanded graphite. It makes the shape-stabilized PCM has the coefficient of thermal conductivity of 1.528 W/(m
• K) and the latent heat of 109.2 kJ/kg. After the simulation of the time for 12 hours, the heat exchange for unit borehole depth of backfilling with shape-stabilized PCM is 1.23 times of the heat exchange for unit borehole depth of backfilling with crushed stone concrete. And the influence radius of backfill materials of shape-stabilized PCM is 0.9 times of the influence radius of backfill materials of crushed stone concrete. So under same area of buried pipes region the shape-stabilized PCM backfill can get heat exchange is 1.37 times of crushed stone concrete backfill. In addition, the heat conductivity coefficient of PCMs has great influence on heat pump coefficient.