heated and unheated regions along the length of the solid cartridge heater this allows the dryer system to be very versatile in meeting certain process or application requirements where more or less drying capacity is required in specific intervals or in specific areas along the width of the dryer in the embodiment shown in fig3 two isolated elongated thin recesses 31 are located towards the outside wall of the air distribution plenum 15 to function as thermal insulators between the air passages 19 and the outside of the air distribution plenum 15 by creating a barrier for heat transfer from the air passages 19 to the outside walls of the air distribution system the elongated thin recesses 31 improve the overall efficiency of the invention and maintain a reduced external surface temperature of the air distribution system 13 in the embodiment shown in fig4 and 5 the air distribution system 13 is manufactured with end plates 32 and 33 and gaskets 34 and 35 to effectively seal off the inlet cavity 20 air passages 19 and orifice chambers 25 from the outside of the air distribution system 13 one of the end plates the heater bulkhead end plate 32 is manufactured with a threaded port.