plate 10 adjacent to the other one of the side edges of the thermal conduction plate 10 the pipe assembly 30 101 b 102 b has multiple pipes the pipes are separately formed in or mounted on the thermal conduction plate 10 and of at least two different gauges and each pipe has a pipe inlet 31 and a pipe outlet 32 with further reference to fig6 10 the pipes may have different interior diameters to define the at least two different gauges or may have different morphology of interior surfaces of the pipes for instance the pipes may have a smooth interior surface 301 a zigzag interior surface 302 a ragged interior surface 303 or a grid embedded interior surface 304 to form the different gauges a pipe assembly 30 101 b 102 b having three pipes may have two pipes having a same gauge and one that is different alternatively the pipes may each be formed to have non identical gauges the pipe inlet 31 of each pipe is securely mounted with one of the distribution outlets 22 and the pipe outlet 32 of each pipe is securely mounted with one of the collection inlets 42 thus a passage of each pipe communicates with the distribution tank 20 101 a 102 a and the collection tank.