final report on the multiport dryer - Argonne National Laboratory

26to produce paper at a higher rate with the same number of dryers. In the lattercase,Average Condensing Heat Transfer Coefficient (W/m 2 K)2500020000150001000050000System Pressure = 170 kPa - 620 kPaQuality = 0.10 - 0.80Multiport Dryer - Present ExperimentsConventional Dryer with Spoiler BarConventional Dryer without Spoiler Bar20 25 30 35 40 45 50Mass Flux (kg/m 2 s)Fig. 13. Average condensing heat transfer coefficients ofmultiport and conventional cylinder dryerscurrent experimental data show that multiport cylinder dryers can potentially increasepaper drying or production rates by as much as 20% when compared with spoiler bartechnology, and by as much as 90% when compared with existing technology withoutspoiler bars (see Fig. 14). These increases were estimated by using an overall heattransfer coefficient of 256 W m 2 K (45 Btu hr ft 2o F) for the conventional cylinderdryers without spoiler bars and the best overall heat transfer coefficient of 328 W m 2 K(58 Btu hr ft 2o F) for the conventional cylinder dryers with spoiler bars. Productionrate increases were estimated with results from the single-tube, nonrotating test channelfor multiport cylinder dryers and average results from the engineering literature forconventional cylinder dryers with and without spoiler bars. Some of the practicaleffects of a prototype or full-scale model multiport cylinder dryer are not yet known.Therefore, there is a need to conduct MD performance tests in a full-scale, rotating testdryer to evaluate the concept under prototypical condition. Consequently, theseincreased production rate estimates should be viewed as idealized target levels.• Uniform dryer surface temperature can be attained because multiport dryer technologyprovides a highly uniform distribution of cylinder-wall temperature, which is the resultof high condensing heat transfer coefficients, together with condensing heat transfer