at the openings 23 is streams having a thickness t fig1 the value for the dimension t should be within the range of 2h to 5h the heated liquid entering the inlet 21 passes through the tow 15 and is divided into substantially equal portions which pass back through the tow 15 at the openings 23 the chamber 22 completely fills with liquid under pressure this pressure forces the liquid through the openings 23 and the tow 15 at a high velocity as shown in fig3 the tow heater 10 is mounted over a vat 30 containing a heated liquid 31 such as water spaced pairs of driven rolls 32 and 33 feed the tow 15 through the tow heater 10 at a uniform speed with the rolls 33 being driven at a higher peripheral speed than the rolls 32 to thereby stretch or draw the tow by adjusting the speed of the rolls 33 relative to the speed of the rolls 32 and thereby adjusting the tension applied to the tow in the chamber the draw ratio can be adjusted the speed of the rolls 32 and 33 will determine the dwell or residence time of the tow in the chamber i e the time that it takes a point on the tow to pass through the chamber since it is not known at what point the tow stretches in the chamber.