System, apparatus, and methods are disclosed for reductant dosing in an exhaust aftertreatment system. The heat pipe has a middle U-shaped portion and two L-shaped portions at two sides of the U-shaped portion, respectively. If the brightness of the surface of the object to which texture mapping is performed is I, then among the coordinates to be read to access texture fdata, the U coordinate is calculated as U=a*I+b, and the V coordinate is determined from V=d. This limits the employability of biometric methods to the supplier’s particular system. Average cell size of the polystyrene foam is equal to or less than 60 m.