Theoretical and Experimental Analysis of Desiccant Wheel Performance for Low Humidity Drying System

Transcription

1 Recent Researces Power Systems and Systems Science eoretical and Analysis of Desiccant Weel Performance for Low Humidity Dryg System RI SUYONO, SOHIF MA, MUHAMMAD YAHYA, MUHD. HAFIZ RUSLAN, AZAMI ZAHARIM & KAMARUZZAMAN SOPIAN Solar Energy Researc Institute Universiti Kebangsaan Malaysia UKM Bangi, Selangor MALAYSIA Abstract:- e dryg process is fluenced by tree ma factors temperature, flow rate and umidity, resultg te dryg process of ot air required accordance wit te caracter of materials wit low umidity, so it can speed up te dryg process. Malaysia is located sout East Asia region tat as a sufficiently ig temperature and umidity, so it requires a process to reduce moisture te air. e system is tegrated solar dryer wit a desiccant weel is designed to produce dry air. e system consists of evacuated tube collector (solar water eater collector), eat excanger, desiccant weel, blower, ot water pumps and ot water tank. o e system produces air wit a temperature of absolute umidity 58.0 C wit kg HO/ kgdry.air is system is capable of evaporatg water kg HO/r. Wit temperatures and umidity are controlled ten te system can perform sensitive dryg material to eat, but also wit a low umidity can reduce te dryg time. Key-Words:- desiccant weel, temperature and umidity, water evaporation. Introduction Dryg process prciple is to vaporize te water te dried material. is process is fluenced by temperature, umidity and air velocity dryer. In te process of dryg air required to eat and dry so tat dryg time can be sortened, but te air temperature must be adjusted to te properties of dried material []. Desiccant weel is widely used to lower te umidity of air te coolg system [], desiccant weel as a good ability to absorb water air [3]. In te process of air troug two desiccant weel tat is latent and sensible state, were addition to te air becomes dry, te air will also experience an crease temperature [40-0]. Notg tat te use of desiccant weel te process of dryg is considered appropriate. Low temperature and dry air are good for dryg foodstuffs []. System usg desiccant weel dryer for dryg sensitive materials suc as products, vegetables and erbs, wit temperature and umidity are low / controlled te dryg of products suc as vegetables to mata color, texture, aroma and nutrients of dried material []. Dryg System e system is designed for dryg a commercial scale. e system consists of solar collector (evacuated tube) wit a 3:3 wide m, 0.6 m area eat excanger 0.5m tick, desiccant weel maximum.500 cfm flow rate and blowers wit a maximum flow rate of.500 cfm. o operate te tool at nigt or wen tere is no sun used electrical air eater for eatg regeneration process. Dryer system uses a eat source of te evacuated tube collector te form of ot water, ten poured to ot water eat excanger to eat te air. Flow rate tis experiment was made at te 99.6 cfm /,59.5 m 3 / for bot processes (regeneration and deumidification), mean ratio between te regeneration of te desiccant weel and deumidification :. Fig. Scematic Diagram of Solar Desiccant Dryg System. ISBN:

2 Recent Researces Power Systems and Systems Science 3 Analitycal Metod is system uses solar energy as eat sources, eat energy from te sun transferred to te water troug te eat pipe evacuated tube. Hot water flowed to te eat excanger to eat air and water tat as passed troug a eat excanger and te eat flow is reduced to te ot water tank and ten flowed back to te collector wit ot water pump, so tis process takes place contuously trougout te process. Hot air generated by te eat excanger is used for te regeneration desiccant weel. is paper will only discuss te performance of desiccant weel and te estimated dryg process, wile te collector performance, eat excangers and oter components not discussed. Desiccant weel operatg system tere are two processes, namely te process of regeneration and deumidification [0]. is process is called regeneration or recovery process is te process of dryg silica gel desiccant tat as been wet wile due process of deumidification. Wile te deumidification process is te process of water absorption te air so te air will become drier and te temperature is creased []. o detere te desiccant weel performance will be evaluated effectiveness deumidification and regeneration process (Sensible and latten), and te adiabatic effectiveness [4]. 3. Deumidification process Sensible/termal d d. () m Latten d d. () m From te equation above, te temperature and absolute umidity of air wic as passed te deumidification process can be calculated by te followg equation: d. d d. d (4) (3) 3. Regeneration Process Equation for te process of regeneration can be written as follows: Sensible / termal reg 8 (5) m Latten m d 8 (6) m us te temperature and absolute umidity of air tat as passed troug te process of regeneration can be written wit te followg equation: out d out d () (8) Adiabatic efficiency can be calculated by te followg equation: ( ) ( ) adiabatic (9) 3.3. Dryg estimate In te analysis of te dryg time will be calculated teoretically wit te assumption tat ideal dryg process, and not discuss te nature of te material te dryg process. Decrease water content te dried material was calculated eac 30-ute tervals until te material is dried acieve te desired water content. In tis analysis, will look for reduction water content te dried material usg pick-up efficiency equation [3]. out W p (0) vt( ) If, as t as W m o m ten, mo mt p () vt ) ( as m t m vt( ) ) () o ( as p ISBN:

3 Recent Researces Power Systems and Systems Science e decrease te per time period m m vt( ) (3) t. n o. n ( as p ) n 0 65 mc p v G a (4) ( ) ( ) emperature ( o C) eoretical 4 Result and Discussion Overall performance of desiccant weel is strongly fluenced by te air used te process of regeneration and te air tat goes to te process of deumidification. e more ot and dry air tat is used prses regeneration and air enterg te deumidification process, te air generated te deumidification process will be more ot and dry because te desiccant weel operation occurs Sensible and latten. Sensible process occurs because te process is valid isoterm process. 4. Deumidification Process Deumidification process on tis system produces te appropriate temperature and umidity for te dryg process. In teoretic temperature deumidification process cog average 33.9 o C wit let air temperature 6 o C regeneration process will result air temperature 58.8 C, tis process can be seen figure. Experiment results sow tat te deumidification process te same conditions produce 58.0 o C air temperature, tis dicates tat te results approaced teritic experiment, te results can be seen Figure 3. Sensible effectiveness of tis system an average of 0.3 is sown Figure ime () Fig.3 eoretical and experimental sensible deumidification ime () Fig.4 Deumidification Sensible In teoretic absolute umidity at te let air regeneration process and te absolute umidity kg HO /kg dry.air air deumidification process kg HO /kg dry.air 004 kg HO /kg dry.air will result air by absolute umidity of te air 00 kg HO /kg dry.air wile te experiment is 0.06 kg HO /kg dry.air. From te results of tese experiments is known latten effectiveness tis system an average of 093. is process can be seen Figure 5 and emperature ( o C) d..d.out. Absolute Humidity (kgho/kgdry.air) eoretical 30 5 ime () Fig. Sensible process of desiccant weel 0.0 ime () Fig.5 eoretical and experimental latten deumidification ISBN:

4 Recent Researces Power Systems and Systems Science ime () Fig. 6. Deumidification Latten Absolute Humidity (kgho/kgdry.air) eoretical ime () Fig.8 eoretical and experimental latten regeneration 4. Regeneration Process Regeneration process aims to dry te silica gel desiccant weel order to function aga as a deumidifier. Regeneration process te cog air is ot and dry air, and air tat as been used for te regeneration temperature becomes lower and wetter. In tis system teoretic regeneration process will produce air wit an average temperature of 4 o C and experiment results sow tat air temperature 39.8 o C, absolute umidity of air wic as been used for te regeneration process will also crease, te teoretic average 00 kg HO /kg dry.air, and experiment results 0.08 kg HO /kg dry.air,, it can be seen Figure and 8. Sensible effectiveness Regeneration average of, wile te regeneration latten effectiveness tis system 089, can be seen Figure 9 and 0. Several process conditions on te desiccant weel Sensible depicted Figure, wile te adiabatic effectiveness desiccant weel can be seen Figure is an average of ime () Fig.9 Regeneration sensible effectiveness ime () Fig.0 Regeneration Latten emperature ( o C) eoretical ime () Fig. eoretical and experimental sensible regeneration Absolute Humidity outlet (kgho/kgdry.air) Deumidification Regeneration Absolute Humidity let (kg Ho /kg dry.air ) Fig. Absolute umidity at deumidification and regeneration process. ISBN:

5 Recent Researces Power Systems and Systems Science Nomenclature ime () Fig. Adiabatic desiccant weel effectiveness 4.3 Dryg Estimate e results of experiments on tis system dicates dry air flow rate,684.6 kg dry.air /r, let air absolute umidity dryg camber average of 0.06 kg HO /kg dry.air, assug a 55% dryg efficiency of te system is capable to evaporate of water te dried material kg HO /jam. If it is assumed tat te material is dried weigg 00 kg wic as a moisture content of 80% itial and fal moisture content of 3% or te fal weigt of 0.3 kg of material. us tis system sould to evaporate water te dried material as muc as 89. kg HO, ten by usg equation (3) can be predicted dryg time. ours. 5 Conclusion In tis study te desiccant weel is used for te dryer system. From te results obtaed tat te desiccant weel suitable for te dryer system. Experiment results deumidification process on tis system produces an average air temperature 58.0 o C by absolute umidity 0.06 kg HO /kg dry.air, Sensible effectiveness 0.3 wereas te average effectiveness latten In te process of regeneration tis system teoretic Sensible eat generatg temperature of 4 o C and experiment results of 39.8 o C, latten a teoretic process produces 0.0 kg HO /kg dry.air, and te results of experiments 0.08 kg HO /kg dry.air. Sensible effectiveness, wile te regeneration effectiveness latten 089. Wit a flow rate of air to te dryg camber,684.6 kg dry.air /r, let air absolute umidity dryg camber average of 0.06kg HO /kg dry.air, and assug 55% efficiency of dryg, ten te system is expected to evaporate water te dried material kg HO /r. d. Deumidification sensible effectiveness d Mass air flow rate for deumidification process (kg dry.air /r) d Mass air flow rate for regeneration process (kg dry.air /r) Mimum value of eiter mass flow rate (kg dry.air /r) Dry bulb temperature of air to deumidification process ( o C) Dry bulb temperature or air out from deumidification process ( o C) Dry bulb temperature of air to regeneration process ( o C) 8 Dry bulb temperature of air out from regeneration process ( o C) Absolute umidity of air to deumidification process ( o C) Absolute umidity of air out from deumidification process ( o C) Absolute umidity of air to regeneration process ( o C) 8 Absolute umidity of air out from regeneration process ( o C) Absolute umidity of air enterg te dryg camber (%) out Absolute umidity of air leavg te dryg camber (%) as Absolute umidity of te air enterg te dryer at te pot of adiabatic saturation (%) s Dry matter content (%) t Dryg time (seconds) V Volumetric airflow rate (m3/s) W Weigt of water evaporated from te product (kg) WAC Water absorption capacity Density of air (kg/m3) c Heat collection efficiency p Pick-up efficiency s Dryg system efficiency G Dry air Mass air flow rate (kg /r) a dry.air ISBN:

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