Heat and Mass Transfer Drying Cotton in Drum Drier

Transcription

1 Heat and Mass Transfer Drying Cotton in Drum Drier Mardono B., Parpie A., Kayumo A., Djuraea N P.G. Professor, Tashkent Institute of Tetile and Light Industry, Tashkent, Uzbekistan Professor, Tashkent Institute of Tetile and Light Industry, Tashkent, Uzbekistan Dotoral student, Tashkent Institute of Tetile and Light Industry, Tashkent, Uzbekistan Senior Researher, Researh Institute of Mehanis and Earthquake Resistane of Strutures, Tashkent, Uzbekistan ABSTRACT: Determination of the regularity of the heat and mass ehange proess of drying raw otton along the length of the drum dryer by eperimental means is diffiult due to the partiular design of the installation. In the artile, the regularities of the hange in the heat and moisture onditions of raw otton and the temperature of the drying agent along the length of the drying drum are determined using the results of eperimental and theoretial studies. KEYWORDS: Raw otton, Drying, Drying regime, Dryer humidity, Heat transfer, Heat apaity, Heating, Drying agent. I. INTRODUCTION Moisture in the mass of raw otton is a omple proess, for the study of whih requires a large amount of eperimental and theoretial work. Raw otton refers to a multiomponent thermodynami medium, the strutural struture of whih essentially depends on the type of tehnologial impat. Therefore, diret analysis of the state of raw otton from the iewpoint of ontinuous medium mehanis is diffiult; here approahes and a onept are needed, as applied to enironments that hae parameters that depend on the type and nature of the proessing of raw otton. The seletion of moisture from the mass of raw otton essentially depends on the formation and deelopment of moisture-ehange proesses in its omponents, the nature of the drying agent and the drying regime. The intensifiation of the drying proess of raw otton is determined by the patterns of heat and material transport inside the body (internal heat and mass transfer) and between the body surfae and the enironment (eternal heat and mass transfer). To properly understand the mehanisms of these proesses under thermal ation, a thermophysial model of raw otton, desribing heat and mass-transfer proesses between the omponents (fiber and seed) and the thermal agent (heated air), should be deeloped []. The mehanism of drying porous materials, whih an be lassified as raw otton, is analyzed in detail in []. II. LITERATURE SURVEY The proess of drying raw otton is determined by the amount and intensity of moisture taken from it. In this ase, the mehanism for drying wet heese is mainly determined by the form of moisture binding to the material and the drying regime, or by the onditions of eaporation of moisture with the surfae of the raw material into the enironment. For the pratial implementation of the drying proess, arious installations and equipment are used, the desriptions of whih are presented in [3, 4]. In partiular, the main parameters and operating priniple of drying drums are gien. As indiated in [3-5], in pratial onditions, the filling of the dryer essentially depends on the operating mode of the dryer. The tasks of drying large quantities of raw otton are most suitable for dryer designs with a apaity of kg/h and more than % or more and moisture remoal, and therefore these types of dryers are urrently the basis for the further deelopment of drying tehnology in the otton industry. This irumstane requires the improement of eisting and the deelopment of new alulation tehniques for determining the main parameters of the drying drum. In the literature, there are arious approimate alulation formulas establishing the relationship between the initial humidity Copyright to IJARSET 63

2 and the final one. At the same time, it is assumed that the geometri data of the dryer, the thermo physial parameters of raw otton and the laws of heat ehange proesses between the oolant and raw otton are assumed to be known. III. METHODOLOGY We establish the origin of oordinates in the initial setion of the drum and diret the ais along its ais and denote by t t () and t () the temperatures of the oolant and the raw otton in an arbitrary setion of the drum. We selet the element d ( м ), from the zone of interation of the raw material with the heat arrier, with the olume dv D d / 4, assuming a temperature uniformly distributed oer the ross setion of the drum and determine the hourly heat onsumption for the seleted element [4] where dq KTdV KTD d / 4 () - is the total olumetri oeffiient of heat transfer kdj/(m h grad), the number K takes into aount a part of the olume of the dryer oupied by the blades, whih will hae a lower olume oeffiient of heat transfer, D - the diameter of the drum, m, T - the aerage temperature differene between the drying agent and raw otton in the olume of the element dv ( t t ) ( t t ) () T T ( t, t ) t t ln t t where t, t - respetiely, the initial and final temperatures of the oolant and raw otton (in Kelin). Denote by W the produtiity of the dryer by moisture (kg/h). Then aording to [4] dq dw( q q ) where q - heat onsumption for eaporation of kg moisture [4], kdj/(kg eaporation of wet) q q t ) ( t 73) ( t 73) ; ( q - heat onsumption for heating kg raw otton in setion, kdj/(kg eaporation of wet): P q q( t ) ( t t ) ; W - Speifi heat of raw otton in kdj/(kg grad): - с. w, (3).6 w where,, 549 and 4, 868 aordingly the speifi heat of absolutely dry raw otton and raw water absorbed by otton-raw otton kdj/(kg grad), w - is the initial moisture ontent of raw otton, %. Taking () into aount, we redue () to the form dw q q ) KTD d / 4 ( By supplying q and q, we obtain a differential equation for determining the amount of eaporated moisture in an arbitrary setion of the drying drum dw KT ( t, t ) D (4) d 4[ q ( t ) q ( t )] Copyright to IJARSET 63

3 Equation (4) is integrated if the temperatures of the oolant t and raw otton t are known as a funtion of the ariable. To determine these temperatures, we use the stationary heat ondution equations for the oolant and raw otton, taking into aount the heat ehange proesses between them, as well as with the drum wall. dt ( t t ) ( t t ) l (5) d dt ( t t ) ( t t ) l (6) d where - - the speifi heat of the heat arrier, kdj/(kg grad), and in the drum, - the flow rate of the oolant and raw otton - the heat transfer oeffiient between the oolant and the raw otton kdj/(kg se grad), - the heat transfer oeffiient between the oolant and the drum wall kdj/(kg m with eaporation of wet), - the heat transfer oeffiient between the raw otton and the drum wall, kdj/(kg m eaporation of wet), l and l - the length of setions of the ontour of the drum ross-setion ontating with the drum wall m, whih are alulated by the formulas, l ml, l ( m) l, l D/ - the length of the ontour of the ross-setion of the drum, m - the portion of the ontour along whih only the oolant with the drum wall is ontated, t - the drum wall temperature (in Kelin). The final moisture ontent of the raw otton is determined through the initial moisture w, the amount of eaporated moisture in the setion L ( L - the length of the drum, m) and the apaity of the drum by the dried raw otton P, kg/h aording to the formula P w W ( L) w (7) W ( L) P IV. RESULTS AND DISCUSSION In the alulations, the alue of the total olumetri heat ehange oeffiient was used in [4]. To determine the oeffiients,, we used the results of the alulations gien in [4], where it is ustomary: D 3, L m,, w 9% t 573 K, t 78 K, P kg/h, m, 65,, 5 m/s. The influene of nonlinearity in the dependene (3) on the speifi heat from humidity was not taken into aount and aepted ( 9), kdj/(kg grad). The flow rate of raw otton was alulated using the formula 4P / D ( - density of raw otton). The drum wall temperature is adopted t 68 K. The oeffiients,,, as well as the density of raw otton ( hene, the flow rate of raw otton) were determined from the oinidene of the results of alulations for the alues of the total amount of eaporated moisture W in the drying drum and the final moisture alulated in []. In [] they were equal: w %, W 8kg/h, 6 kg/m 3. For other alues of humidity and produtiity, the results of [6, 7], obtained eperimentally by the method of the full fator eperiment of the FFE type 3, arried out on a SB- dryer at the temperature of the drying agent T, С (<T<), produtiity P, т/h (3,5<P<) for wet otton W, % (,5<W<,3). The subjet of the study was otton raw arieties С-654, II industrial grade. Using the regression equations obtained For raw otton moisture: W = -3,36 +,45W +,984П +,4Т -,6WТ; For the moisture ontent of the fiber: W =,434П +,5T +,7656W +,545ПW-,34TW -,9554; For the humidity of seeds: W =,356П+,688T+,65W-,573ПW-,3TW-3,5796; Copyright to IJARSET 63

4 For the heating temperature of the fiber: T =,5987П +,4369T +,9696W-,794ПT-,4ПW-,946TW-,85; for the heating temperature of the seeds: T =,9T-,3669П-,934W +,498ПT +,8657ПW -,63TW -,866ПTW +,338 alues are determined aboe the indiated parameters,,, and are gien in the table. In the numerator there are alulated, in the denominator, eperimental data. Table. Changes in humidity and the temperature of heating of raw otton, depending on the performane of the drying drum W 5%, t C =,9 kdj/(kg se grad); =,7 kdj/(kg m with eaporation of wet), =, kdj/(kg m with eaporation of wet); P ( t / h) T (K) / / 39 T (%),6,,78,36,5,46,87,,7,,5,94 W (%) 9,58/ 9,9/,7/,5/,8/,/,4/,7/,96/,6/,56/,86/ 9,8 9,8,,6,8,,4,7,9,,5,8 W (%),4,,3,,5,5,5, , kdj/ (m h grad) It an be seen from the table that, theoretially, ertain results and eperimental results are within the limits of the allowed error alues. It an be seen that the heat transfer oeffiients between the oolant and the raw otton, between the oolant and the drum wall, between raw otton W 5% and the drum wall, with the raw otton moisture t C and the temperature of the drying agent, do not depend on the performane of the drum. 3, kdj/ 9 (m h grad) Produtiity, t / h Fig.. Changes in the olume oeffiient of heat transfer depending on the produtiity of the drying drum From the analysis of the graph of the hange in the total olumetri heat transfer oeffiient depending on the produtiity of the drying drum, presented in Fig.. it follows that with an inrease in the produtiity of the drying drum from 4 to t/h the olume heat transfer oeffiient inreases from 65 to 8 kdj/(m h grad) and then dereases to kdj/(m h grad). In Fig. shows the temperature ariation of heated air and the fiber-seed miture T =mt +(-m)t (where m is the fration of the fiber in the miture) along the length of the drying drum with the raw otton moisture W 5% and Copyright to IJARSET 633

5 Temperature, К Температура, К Temperature, К Temperature, К Temperature, К Temperatureра, К the temperature of the drying agent t C as a funtion of the drying apaity drum, where m=,35. The alues of the parameters,,, are taken from Table. T = mt + (-m) T (m) =,35. P 4 kg/h P 6 kg/h P 8kg/h P kg/h P kg/h P 4 kg/h Fig.. Changes in the temperature of the drying agent () and raw otton () along the length of the drumа The analysis of the graphs presented in Fig. shows that the air temperature along the drum length for all alues of the drum's performane pratially dereases nearly linearly. The temperature of raw otton along the length of the drum Copyright to IJARSET 634

6 Moisture of raw otton, % Moisture of raw otton, % Moisture of raw otton, % Moisture of raw otton, % Moisture of raw otton, % Moisture of raw otton, % first rises sharply, and then there is a slight derease. This is eplained by the fat that in the initial setion of the drying drum the raw otton is intensiely heated, reahing a ertain temperature the drying proess begins, and some of the heat is arried away by the oolant instead of moisture. P=4 kg/hour P=6 kg/hour P=8 kg/hour P= kg/hour P= kg/hour P=4 kg/hour Fig.3. Changes in the moisture ontent of raw otton along the length of the drying drum Copyright to IJARSET 635

7 Analogous ures for the moisture ontent of raw otton along the length of the drum are shown in Fig.3. It an be seen that with the inrease in drum produtiity, the amount of moisture etration dereases. So, for eample, at P = 4 kg / h, moisture etration is about 5%, at P = 4 kg / hour,5%. V. CONCLUSION AND FUTURE WORK The regularities of the hange in the olume oeffiient of heat ehange, the temperature of the drying agent and raw otton, as well as the humidity of raw otton along the length of the drum are determined for different apaities of the drying drum for wet otton. For effetie use of the drying drum by olume, it is reommended to operate the drying drum at apaities of 8- t/h on wet otton. This also ontributes to an inrease in the uniformity of drying of raw otton omponents at suh produtiity [8]. It is established that the reommended drying regimes based on the temperature of heating of raw otton at the eit of the drying drum is erroneous, sine the analysis of the temperature of heating of raw otton along the length of the drying drum showed that this inde eeeds by 8 C than at the output, whih leads to a sharp deterioration in the quality parameters of the fiber. Moisture remoal along the length of the drying drum desribes a one ure, whih means that in the initial setions of the installation the heat is epended on heating the raw otton, and then a gradual derease in humidity begins. The analysis of the ures shows that with a derease in drum apaity, the final moisture ontent dereases and an aelerate the proess of moisture etration from the drum. The obtained results an be used in the deelopment of optimal drying regimes in eisting plants, depending on the initial moisture ontent of raw otton, the produtiity of the dryer on wet otton, and in the deelopment of new tehnology and tehnology for drying plants for raw otton REFERENCES [] Parpie A.P, Mardono B., Usmonkulo A.K., «Heat and mass-ehange proesses in raw otton and its omponents», Tashkent. 9 p. 3. [] Lyko A.V., «Theory of drying», State Energy Publishing House. 47 p. 95. [3] Lebede G.D., «Calulation and design of drying plants», M.-L. State Energy Publishing House. 38 p [4] Miroshnihenko G.I., «Fundamentals of designing mahines for primary otton proessing», M. Mashinostroenie. 486 p. 97. [5] Uldyako A.I. «Drying of raw otton», M. Mashinostroeniye [6] Kayumo A.H., «The influene of drying regimes in the moisture of raw otton and its omponents», Journal of Tetile Siene & Engineering. pp [7] Parpiye A.P., Kayumo A.H., Pardaye H., «Effet of temperature of the steady-state heating omponents of the otton-seed at the drying proess», European siene reiew. Vol.7-8. pp [8] Parpiye A.P., Kayumo A.H., «Analytial reiew of the applied temperature in the proess of drying raw otton», Sientifi and Tehnial Journal of FerPI, Vol., pp Copyright to IJARSET 636