小型稻谷干燥機——風運動提升部分的設計

購買設計請充值后下載，資源目錄下的文件所見即所得，都可以點開預覽，資料完整，充值下載可得到資源目錄里的所有文件?！咀ⅰ浚篸wg后綴為CAD圖紙，doc,docx為WORD文檔，原稿無水印，可編輯。具體請見文件預覽，有不明白之處，可咨詢QQ:12401814 科技論文及翻譯Experiment research on grain drying process in the heat pump assisted fluidized bedsJing Yang，Li Wang，F(xiàn)iXiang，Lige Tong，andHua Su MechanicEngineering School，University of Science and Technology Beijing，Beijing 100083，ChinaAbstract：A heat pump assisted fluidized bed grain drying experimental system was developedBased on this systema serial of experiments was performed under four kinds of air cycle conditionsAccording to the experimental analysis，an appropriate drying mediumair cycle for the heat pump assisted fluidized bed drying equipment was decidedwhich is difierent from the commonly usedheat pump assisted drying systemThe experimental results concerning the drying operation perform ance of the new system show that the averaged coefi cient of perform ance fCOP1 can reach more than 25The economical evaluation was perform ed and the power consumption for removing a kilogram water from grains was about 0485 kWhkg(H，0)，which shows its reasonable commercialefi ciency and great application potentiality in future markeKey words：heat pump，fluidized bed，grain，drying，air recycle1 IntroductionNowadays there 1s an urgent need for the development of high capacity and high quality grain drying equipment in the agriculture of China1As the society and agriculture develop quickly，it is of important practical value to develop the efi cient，energy saving， nonpollution and even movable drying equipment to match the mechanization harvestry 2Traditional methods of drying involve the direct combustion of fossil fuel together with controlled ventilationSuch methods are obviously ineficient，with efficiencies never exceeding 20 ，not to mention the fact that expensive primary energy is depleted only to produce low grade heat3The traditional drying methods have been prevailing domestically up to now,not only for grain drying，but also for other matedals such as wood，cement，ceramics and medicine etcAs the power supply structure improved greatly by the hydropower and nuclear power development policy of the government of China，the research on the heat pump assisted drying system is of special meanings，due to the fact that a portion of power usually can supply more than 2 portions of heat energy for drying by using a heat pumpRecently there are quite a few scholars48findin their interests in heat pump assisted drying area and the great potentiality in future for heat pump applications in drying areaHowever the researches9，1 0mostly concentrate on the low temperature heat pump with the hot medium temperature lower than 55。CThere was still a blank in the high temperature heat pump assisted drying system with temperatures above 70。C and especially for the system with grain drying and heat pump working together,which is the great motivation of the present paperBesides the gassolid fluidized beds have obtained widely applications in drying area with so obvious advantages such as high gassolid contact surface，high heat and mass transferrates，easy to be mechanically operated，usually with great continuous production capability and high quality of drying due to its uniform temperature field11，121This paper combined the both advantages of heat pump and fluidized bed to develop a new type of graindrying experimental systemBased on this system，aserial of experiments was perform ed under different conditionsAccording to the experimental analysis，an appropriate drying mediumair cycle for the new type heat pump assisted fluidized bed drying equipment was decidedwhich is different from the traditional heat pump assisted drying systemTh e research results also show the optimistic future and the potential market competition ability of this new equipment2 Experiment In a drying system with a heat pump and a fluidized bed togetherthere are three material flows：the grain flow，the refrigerant flow and the dry ing mediumAir flowThis air flow relates the grain flow to be dried and the refrigerant flow of the heat pump together and become the medium transferring the moisture and heat between the both，in which the flow ratetemperaturevelocitv and humidity of the air influence the working condition of the heat pump，whereas the working condition of the heat pump also afects the temperature and humi dity of the air and further influences the drying processHere the air circulation jn the systemis vital not only to the working performance of the heat pump and the dry ing process but also to the final structure of the whole equipmentHence the experimental system was designed as shown in figure 1which includes mainly four parts：fluidized bed drying room，heat pump，tube connection and several valvesThis system can realize four types of air circulation by adjusting difierent valvesType one：close valves 1，2，4，5 and open valves 3，6，7，in which the air discharged from the fluidized bed flows only through the evaporator of the heat pump and then the condenser where it is heated and finally into the fluidized bedperforming a close circuit circulationType two：close valves 2，3，6 and open valves 1，4，5，7，in which the air discharged from the fluidized bed flows directly through the condenser and then into the fluidized bedperformi ng a close circulation，and the air from circumstance flows through the evaporator of the heat pumpType 3：close valves 1，3，5 and open valves 2，4，6，7，in which the air discharged from the fluidized bed flows completely through the evaporator and then into the ambientwhereas the ambient air is absorbed through the condenser by the ventilator and then flows into the fluidized bedperforming an open circulationType 4：open all the valves and adjusting their turndown ratioin which the air discharged from the fluidized bed splits into two parts，one mixing with some ambient air flows into the evaporator and then into the ambient，the other mi xing with the ambient air flows into the condenser and then into the fluidized bed，performing an half close and half open air circulation3 Parameter measurements and principlesIn this experiment，the parameters need to be measured are the temperatures at the inlet and the outlet of the fluidized bed and the evaporator and the condenser,the flow quantities of the air through the evaporator，the condenser and the fluidized bed respectively，the high and the low pressures of the refrigerantAll the temperature measurements adopted digital temperature sensors which were calibrated by the liquid in the glass therm ometer from 0 to l 00。CThe hot spherical wind velocity meter was used to measure the flow velocity and then to get the flow quantityThe power of the compressor was calculated based on its phase current measured by a multimeterThe refrigerant pressures were measured by elastic tube manometersThe performance parameters of the system can be calculated based on these measured parameters by following formulaeThe air flow quantity：v=(u/N) A3600,m3/h；The refrigerating output from the evaporator：Qe=VcairC（toe-tie）/3600,KW ；The heating output from the condenser：Qe=VcairC（toe-tie）/3600,KW；The compressor power：P=3IpVp=(I1+I2+I3)220/1000,KW；The coeficient of the performance(COP)of theheat pump：COP=QC/PThe flow rate of refrigerant：X=cP/W,kg/s The theoretical refrigerating output from the evaporator：LQe=Xqe,KW；The theoretical heating output from the condenserLQc=xqc, KW；The theoretical coefi cient of the performance ofthe heat pump：LCOP= LQc/pHere the theoretical cycle refers to the ideal thermodynamic cycle corresponding to the high and low pressures measured in the experiment4 Experimental results and analysis41 Efects of air circulation typeIn order to get the effect from different air circulations on the drying process，we conducted four types of air circulation experimentskeeping all the other conditions the same，such as the air flow quantity and the inlet temperatures etcand found that the temperature at the inlet of the fluidized bed is the highest in type 2，that in type l is the lowest and that in type 3 is slightly higher than that in type l，that in type 4 is between that in types 2 and 3This is because in type 2，the air circulates only through the condenser and the heat wasted is comparatively small resulting in the high temperature at the outlet of the condenserThe humidity of the air at the inlet of the fluidized bed was also higher，since the air discharged from the fluidized bed did not remove its moistureHowever,in fact the connection tube was not closely sealed，therefore there was some fresh air from ambient flowed into the condenserThat is like such a circulation：close valves 36 and open all the other valvesin which the air discharged from the fluidized bed，mi xing with the ambient air flowed through the condenser and then into the fluidized bed，meanwhile some air from the fluidized bed flowed into the ambient through the interspacebetween the fluidized bed and its blastcapIn this experiment system1 0一20 fresh air was estimated mi xing into the flow in air circulation between the condenser and the fluidized bedHence type 2 with a certain fresh air ratio can be chosen as the best air circulation used in the following experiments42 Efects of air flow quantity through the evaporator Two experiments were performedIn one experiment1 00 k2 grains were put into the fluidized bed with a moisture of about 25 fits denominator contains no water)，and then the system was started and the airflow through the evaporator was kept relatively low at about 500 m hThe performances of the heat pump are shown in figures 2-4In the other experiment，the system was started firstly and the airflow through the evaporator was kept high at about 2500 m3h after the temperature at the outlet of the condenser reached about 70。C 100 kg grains with a moisture of 27 were put into the fluidized bedThe heat pump performances are shown in figures 5-7The air flow through the condenser is about the sameof 1 650 m3h for both experimentsFigure 2 Pressure variation of the refrigerant in the dry ing process at v=soo mahFigure 3 Performance of the heat pump in the drying process at v=5oo mahFigure 4 COPoftheheatpump atv=5ooIll3，l1Figure 5 Pressure variation of the refrigerant in the drying process at v=25oo mahIn figures 3，4 and 6，7，the theoretical results are all calculated from the ideal refrigeration circulation respectively coresponding to the high and low pres。sures of the refrigerant in figures 2 and 5The comparison between figures 3 and 6 shows that the heat output from the condenser greatly increases by in creasing the air flow through the evaporator and the COP is much closer to the idea1 value in figure 7 than that in figure 4Thus the airflow quantity through the evaporator is very important to the performance of the heat pumpIn fact，the growing of the air flow quantity through the evaporator greatly enhances the heat transfer rate between the air and the surface of the evaporator resulting the worldng medium in it absorb more heat at the same temperature differenceTh e theoretical analysis also show that as the airflow increases further,the heat absorbed by the evaporator will reach its peak and then level offFigure 6 Performance of the heat pump in the drying process atv,=25oom3hFigure 7 COP of the heat pump at v=2soo m3h43 Drying process of the heat pump assisted fluidized bed grain dryerFigure 8 shows the temperature variations at the inlet and the outlet of the fluidized bed during the drying process under the same condition to the experiment at Ve=2500 m hIt shows that both the temperatures rise gradually with timeAt such temperature variation，the wheat drying process is shown in figure 9，which displays the wet moisture(the fraction of the water quantity contained in the grains to its total quantity)and dry moisture(the fraction of the water quantity contained in the grains to its absolute dry quantity)variations of wheat wifh drying timeW e can see that it takes about 60 min for the wheat to drv from a wet moisture of 21-3 to 13 Figure 8 Temperature variations at the inlet and outlet of the fluidized bed during the drying process at v,=2500m3hFigure 9 W heat moisture variations during the dry ingprocess at v,=2500 m3h44 Economical evaluationThe factors afecting the commercial eficiency of the drying system are the drying time，the COP and power consumption of the heat pumpHowever the drying time mainly depends on the air temperature at the inlet of the fluidized bedIn order to analyze the com ercial efficiency of the systemwe assume that the wheat is continuously dried bv the system as it was done by the most dryers in industry，the temperature at the inlet of the fluidized bed is about 70。C which wasobtained in the experimentIn such assumptions，we can obtain that the drying time needed for wheat to dry from its wet moisture of 20 t0 13 is about 35min，which is deduced from another experiment2and will not be presented hereAccording to the known parameters mentioned above and the heatpump power consumption in figure 6，including the blower power consumption in the system，the averaged power consumption of the system is gotten (about 55 kW)during the drying processConsidering the capability of the fluidized bed is about 100 kg，we can conclude its totally power consumption per unit grain output is about 00321 kW hkg or that per unitwater removed from the grain is 0458 kW hkg(H20)5 Conclusions(1)Th e appropriate air cycle for drying grain is that the air discharged from the fluidized bed directly flows into the condenser of the heat pump with 10 一20 flesh air where it is heated and then flows into the fluidized bed to form a circulation(2)The airflow through the evaporator is very important to the perform ance of the heat pumpThe higher the flow quantity，the beaer the perform ance ofthe heat pump(3)Th e economical evaluation shows that if the system working at continuous state，its power consumption for removing a kilogram water from the grains is about 0485 kWhkg(H2O)and shows great potentiality in the future marketNomenclatureV,Ve,Vc:Th e flow quantities for the fluidized bed，the evaporator and the condenser,respectively；u:The air velocity at the measured pointms；N:Th e number of the measured points；A：Th e tube across area，m ；Qe,Qc:Th e refrigerating and heating outputs of the heat pump，kW ；rair:Th e air density，kgm ；C:Th e air specific heat capacity，kJ(kg。c)；toe,tie:Th e temperatures at the inlet and the outlet of the evaporator，。C：toc,tic:Th e temperatures at the inlet and the outlet of the condenser,。C：Ip:Th e averaged phase current of the compressor,A;Vp:Th e phase voltage，V；X：Th e mass flow rate of refrigerantkgs；c：Th e compressor efficiency，about 09 here；W：Th e theoretical compressor work per unit masskJkg；LQe,LQc: Th e theoretical refrigerating and heating output of the heat pump，kW ；qe,qc:Th e refrigerating and heating outputs from theoretical cycle per unit mass refrigerant，kJkg；COP,LCOP:Th e practical and theoretical coefficients of the perform ance of the heat pumpReferences1XHZhu and WCGuo，The situation and development of the grain drying equipment in our countryJI AgricFood Mach(in Chinese)，No4，1998，P22JYang and LWang，Heat Pump Assisted Fluidized Bed Grain Drying Technology Research (in Chinese) R，Technical Report Submitted to Educational Department of China (00020)，University of Science and Technology Beijing，20023 Manuel SV Almeida，CMarcio，Gouveia，Suzana RZdebsky,an d Jose Alberto RParise，Performan ce an alysis of a heat pump assisted drying system J，Int Energy Res，14(1990)，p3974RKLei and JMBunn，Evaluation of a solar-driven absorption heat pump J，TransASAE，37(1994)，No4，p13095YZhang，QsLiu，and YCLi，Development and application of heatpump technologyJI Energy Eng(in Chinese)，2001，No4，p326GC Gao，JF Wang，and YE Feng，F(xiàn)urther studying on the perform ance of heat pump drying unitsJ，F(xiàn)ood Sci(in Chinese)，16(1995)，No5，P597XDLi and JMa，Brief introduction to hot pump drying technologyJ，ChemEngDes(in Chinese)，7(1 997)，No6，p408KMYu and QWang，Development and its application foreground of heat pump drying technologyJ，Energy Techno1(in Chinese)，21(2000)，No1，p_369BHWang and XZWang，Heat pump drying unitsJ，ChemWorld(in Chinese)，38(1997)，No7，p343l0Y Ma，JHZhang，and YI Ma，Th e optimal analysis of the drying heat pump system J，Acta EnergySoL Sin(in Chinese)，2 l(2000)，No2，p208llXLHuai，LWang，and XZNi，Heat and mass transfer during granular materials dryingJ， UnivSciTechno1Beijing(in Chinese)，20(1998)，No5，p484l2XLHuai，LWang，and ZY Qu，Mathematical model for the drying process of granular materials in a fluidized bedJI UnivSciTechno1Beijing，7(2000)，No4，p296關于用帶有熱泵輔助流化床在谷粒烘干過程中的實驗研究Jing Yang，Li Wang，F(xiàn)iXiang，Lige Tong，and Hua Su摘要：一種熱泵輔助流動床谷物干燥實驗系統(tǒng)已經開發(fā)。基于這系統(tǒng)，在四種不同的空氣周期條件下進行了一系列的實驗。根據實驗分析，為熱泵輔助流動床烘干設備制定了一個適當?shù)母稍锟諝饨橘|循環(huán)，它完全不同于普通使用的帶有烘干系統(tǒng)的熱泵。關于新系統(tǒng)的烘干操作系統(tǒng)性能的實驗結果表明：平均性能系數(shù)超過2.5。進行經濟評估，從谷粒中去除一千克水的消耗能量大約是0.485kw.h/kg，它顯示合理的經濟效益和在在未來的市場上有著巨大應用潛力。關鍵字：熱泵，流化床，谷物，烘干，空氣循環(huán)1.引言現(xiàn)在，在中國農業(yè)里急需發(fā)展高容量和高質量的谷粒烘干設備1.隨著社會和農業(yè)快速地發(fā)展，為了匹配機械化收割，提高效率、節(jié)能、不污染和甚至可移動的烘干設備有著重要的實際價值2。傳統(tǒng)的烘干方法涉及到連同控制空氣流通的直接石化燃氣的消耗。這種方法的效率明顯不高，效率從來不超過20%，更不用說：昂貴的基本能量大大減少，它僅僅來生產低階段的熱量3。到目前為止，傳統(tǒng)的烘干方法在國內很流行，不僅為谷粒烘干而且為其它材料例如木材、水泥、陶瓷和藥等等。因為中國政府氫能和核能的發(fā)展政策大大地提高了電源結構，關于帶有熱系統(tǒng)的熱泵研究具有特殊的意義，由于一部分動力通常能提供大于2%由熱泵烘干的熱能量。近來相當多的學者4-8對促進干旱地區(qū)的熱泵有興趣并且發(fā)現(xiàn)：在干旱地區(qū)熱泵在未來具有很大的應用潛力。然而，研究者9,10大部分關注低于55適中的溫度的低溫熱泵。對帶有溫度超過70烘干系統(tǒng)的熱泵仍然是一片空白，尤其是帶有谷物烘干和熱泵一起工作的系統(tǒng)，它對目前的論文具有很大的動力。除此之外，由于它具有明顯地優(yōu)勢例如數(shù)量大地氣固接觸面、高的熱量、質量轉移率、容易機械操作、由于它有一致的溫度通常有著連續(xù)產量能力和高的烘干質量，氣固流化床在干旱地區(qū)獲得廣泛地應用11，12.論文結合熱泵和流化床兩者優(yōu)勢發(fā)展了一種新的烘干實驗系統(tǒng)。基于這種系統(tǒng)，在不同的條件下執(zhí)行了一系列的實驗。根據實驗分析，執(zhí)行了為帶有流化床的烘干設備的一種適中的烘干的中等空氣周期，它完全不同于帶有烘干系統(tǒng)的傳統(tǒng)熱泵。研究結果也表明：未來很樂觀并且這種新設備具有市場競爭潛力。2實驗在有熱泵和流化床的烘干系統(tǒng)里，有三種材料流動：谷物流動，制冷流動，烘干適中空氣流動?？諝饬鲃影压任锪鲃雍蜔岜玫闹评淞鲃勇?lián)系在一起并且變成兩者之間轉移濕度和熱度的工具，流速、溫度和空氣的速度和濕度影響熱泵的工作條件，然而熱泵的工作條件也影響空氣的速度和濕度并且進一步影響烘干過程。在這一點上系統(tǒng)的空氣流通是至關重要的，不僅對熱泵的工作性能和烘干有影響而且對整個設備最終結構有影響。因此按照圖一設計了實驗系統(tǒng)，它主要包括了四部分：流化床烘干室、熱泵、管聯(lián)接和幾個閥門。圖一：帶有熱泵輔助流化床谷物烘干實驗系統(tǒng)的電路原理圖這系統(tǒng)通過調整不同的閥門能實現(xiàn)四種類型的空氣流通。類型一：關閉閥門1，2，4，5同時打開閥門3，6，7，從流化床釋放的空氣僅僅通過熱泵的蒸發(fā)器然后通過它被加熱的冷凝器最終流入流化床，它叫閉合的電路循環(huán)。類型二：關閉閥門2，3，6同時打開閥門1，4，5，7，從流化床釋放的空氣直接通過蒸發(fā)器然后流向流化床。它叫閉合循環(huán)。類型三：關閉1，3，5同時打開2，4，6，7，從流化床釋放的空氣完全通過蒸發(fā)器然后流進周圍的空氣，然而通過通風設備周圍空氣被冷凝器吸收然后流入流化床。它叫開放循環(huán)。類型四：打開所有的閥門并且調整降低的比率，從流化床釋放的空氣分成兩部分，混合著周圍空氣的一部分流入蒸發(fā)器然后流入周圍空氣；混合周圍空氣的另一部分流入冷凝器然后流入流化床，它叫半閉半開的空氣循環(huán)。3參數(shù)測量和公式 在這個實驗中，必須測量的參數(shù)：流化床、蒸發(fā)器和冷凝器的出口和進口的溫度，通過蒸發(fā)器、冷凝器和流化床各自的流動空氣的數(shù)量，制冷劑的高壓和低壓。所有溫度測量采納數(shù)字溫度傳感器，它是從0到100通過液體用玻璃溫度計來校準的。熱的球形風速儀表被用來測量流速然后得到流數(shù)量。基于外用表測量的階段氣流來測量壓氣機的動力。用彈性管壓力計測量制冷壓力。通過下列公式這些測量參數(shù)可以計算系統(tǒng)的性能參數(shù)。空氣流數(shù)： v=(u/N) A3600,m3/h來自蒸發(fā)器的制冷輸出功率： Qe=VcairC（toe-tie）/3600,KW來自冷凝器的熱輸出功率： Qc= VcairC（toc-tic）/3600,KW壓縮機功率：P=3IpVp=(I1+I2+I3)220/1000,KW熱泵的性能指數(shù)：COP=QC/P;制冷劑的流量：X=cP/W,kg/s來自蒸發(fā)器的理論制冷輸出功率：LQe=Xqe,KW來自冷凝器的理論熱輸出功率：LQc=xqc, KW熱泵的理論性能指數(shù)：LCOP= LQc/p;在此，理論周期指的是理想的熱力學周期，它相應于在試驗中測量的高壓和低壓。4.實驗結果和分析4.1空氣流通類型的效應為了獲得從在干燥過程中不同空氣循環(huán)的效應，我們進行了四種類型的空氣流通實驗.保持所有其他條件相同，如空氣流動量和入口溫度等。并發(fā)現(xiàn)，型號2在流化床入口的溫度是最高的，型號1中是最低的，而且，型號3略高于在型號1，型號4在型號2和型號3之間。這是因為， 在型號2中空氣流通只能通過冷凝器并且余熱比較少地造成在冷凝器出口處的高溫?？諝庀鄬穸仍诹骰踩肟谝草^高，因為空氣從流化床排出沒有去掉其水分。然而事實上，連接管并不完全密封，因此，有一些新鮮的空氣從環(huán)境中流入冷凝器。這就是像這樣一個循環(huán)：關閉閥門3,6和開放的所有其他閥門.其中的空氣排出流化床，與流經冷凝器的空氣混合，然后進入到流化床，同時一些流化床里的空氣通過流化床及其風帽之間空隙流入周圍環(huán)境。在這個實驗系統(tǒng)，在冷凝器和流化床之間估計有1 0 一20 的新鮮空氣混合到流動的空氣流通之中。因此，具有一定的新鮮空氣的比例的型號2可以作為最佳的空氣流通在下面的實驗中使用。4.2通過蒸發(fā)器的空氣流量效應我們進行了兩個實驗，在一項實驗中，含水分約25 的1 00千克谷物放入到流化床（其母體不包含水分）。然后系統(tǒng)啟動和通過蒸發(fā)器氣流保持相對較低的速度約以500米/小時。熱泵的工作情況是顯示數(shù)字2-4。在令一個實驗中，該系統(tǒng)首先啟動和氣流保持以高約2500 立方米/小時的速度通過蒸發(fā)器。在冷凝器出口處的溫度達到約70度后將水分含量為27 的100公斤放入到流化床。熱泵的工作情況是顯示數(shù)字5-7 。這兩個實驗中，氣流都是以相同的1 650立方米/小時的速度通過冷凝器。圖2制冷劑在以500立方米/