1、果蔬太陽能干燥脫水裝置設計摘要：根據廣式涼果的干燥特性，設計開發了一套小型全天候太陽能干燥設備，并對該設備進行應用 試驗研究，對比分析不同涼果在研制的干燥設備中的實際應用結果，與傳統的自然日曬干燥、熱風干 燥相比的優勢，尋找設備干燥涼果最佳工藝條件，對工廠的實際運作起指導作用。（1）該小型裝置特點是利用對V型太陽能集熱板進行改造，使之成為既可輸送熱風，也可實現 儲存熱量于熱水中，該設備由集熱板，干燥室，小型風機，儲熱水箱，蛇行風管，水泵，溫濕度感應 器，小型換熱器，自動控制閥門及空氣過濾裝置組成，有完整的一套集熱收集太陽能系統和熱風干燥 系統。白天干燥過程中，風從集熱器底部經加熱后進入干燥室干

2、燥，排出的熱風經鼓風機重新進風， 當干燥室內溫度過高時，自動控制閥將打開，水由集熱器加熱收集熱量儲存于保溫水箱中：夜間當溫 度感應器感應干燥室內部溫度過低，由控制閥中斷集熱器進風11,風由水箱中蛇形風管由水加熱進入 干燥室，之后類似于白天干燥過程；白天重新開始時，控制單元驅動控制閥關閉蛇形風管進風II,打 開集熱器進風II,又開始集熱板熱風干燥過程，儲熱水箱又可開始儲存熱能，周而復始，實現連續干 燥操作；氣候條件不佳時，可利用水箱中的電熱絲.加熱水，通過蛇形風管實現熱風干燥過程。該太陽 能連續供熱式干燥設備，能連續供熱、全天候工作、成本低、結構簡單、干燥效率且熱利用效率高。（2）試驗中采用的自

3、主研制太陽能干燥設備，空氣對流方式為自然對流和強制對流方式，研究了 樣品的干燥特性，在達到干燥要求的情況下，自然對流干燥時間需14h,強制對流干燥所需時間為1211, 遠遠低于傳統口曬干燥（50h）,自然對流干燥整個干燥過程樣品的平均Deff值為1.39X10-6m-/s,強 制對流干燥過程中樣品的平均Deff值為1.26X10-6m-/s,兩種干燥方式干燥的水分擴散能力都比較均 勻。（3）干燥設備自然對流干燥和強制對流干燥兩種干燥方式下，以干濕梅作為試驗樣品，研究樣品 的理化品質及感官特性，試驗結果表明，隨著濕基濕含量的降低，處于不同層的梅子成品時的總糖、 總酸和鹽含量均有不同程度的增加，在

4、樣品色澤方面，非酶褐變使各層樣品的L*值和a值上升，但 對于b值而言，果皮果肉在干燥過程中趨勢相反（果皮b值下降，果肉b值上升），達到出廠產品 品質要求。通過對干燥設備不同干燥方式不同物料層，樣品理化及感官特性的研究，試驗結果表明， 自然對流方式通過適當的調整物料層的位置，對于樣品的品質會有一定程度的提高，而強制對流方式 由于干燥相對比較穩定，不需要通過調整物料層的位置來提高樣品的品質。（4）太陽能干燥設備不同干燥方式下的應用研究表明，相對于自然口曬干燥、溫室、烘箱干燥等 傳統干燥方式，太陽能干燥設備存在明顯優勢，干燥時間明顯縮短，最多可以縮短76%,設備干燥總 效率為63.4%,干燥過程環保

5、節能；干燥環境高溫低濕，產品品質干燥效率和生產成本均有不同程度 的提高，可以滿足包括梅子等熱敏性物料。在內的多種農產品的干燥要求。（5）樣品干燥至目標水分含量時，自然口曬大約需要5011,溫室干燥約為30h,烘箱熱風干燥需 要12h,自制太陽能干燥設備自然對流方式及強制對流干燥方式耗時分別為14h和12h.強制對流、 烘箱干燥、自然對流、溫室干燥與自然口曬干燥在12h內濕含量分別降至58.08%、57.08%、60.21%、 64.32%、69.22%。在干燥到相同的濕基濕含量（最終產品）的時候，五種干燥方式干燥產品水分活度 均到達儲藏要求，產品品質均達到了產品出廠的要求，綜合而言，太陽能干燥

6、設備干燥效果最佳。綜上分析可以知道，利用自制廣式涼果小型太陽能全天候干燥設備研究溫室、自然對流和強制對 流等干燥方式與傳統熱風干燥與自然口曬干燥的差異，本試驗為小型太陽能全天候干燥設備對工廠的 加工生產中的實際應用提供理論依據。太陽輻射具有分散性和斷續性的特點，是太陽能利用中最大的困難。如何有效地收集蓄積太陽能, 對太陽能的利用效率有著非常重要的影響。太陽能在建筑采暖和農業口光溫室的應用中，太陽墻是太 陽能收集和蓄積的關鍵技術，是實現太陽能-建筑-體化的重要組成部分，也是世界各國學者普遍研究 和關注的課題。因此，太陽墻的研究有著非常重要的意義。本文綜合分析了國內外“太陽墻”的研究 現狀，集多孔

7、介質復合Ti-ombe墻和太陽能多孔集熱墻優點為一體，設計了一種多孔介質太陽墻，并 采用數值模擬的方法對多孔介質太陽墻的傳熱機理及應用進行了研究。從簡化的角度出發，建立描述多孔介質太陽墻傳熱與流動特性的一維數學模型，對作為媒質 的空氣在多孔墻內的流動，以及與多孔墻之間的換熱機理進行了初步的研究。結果表明:多孔墻能收集 與蓄積太陽能，并加熱空氣;降低多孔墻入I I空氣速度，能夠提高空氣的溫度;在保證所需的太陽輻射 吸收率的條件下，增大多孔墻的孔隙率與滲透率，能夠提高空氣的溫度;當多孔固體材料采用金屬與非 金屬材料時，出II空氣溫度有著較大的差別。當多孔骨架材料采用鋁時，空氣的溫升幅度較大，出II

8、 空氣溫度高，而采用巖石，空氣的溫升幅度較小。在實際應用中，應合理選擇滲透率和多孔骨架材料, 盡可能地降低初投資。基于對多孔墻的熱分析，為降低多孔墻與環境之間的輻射與對流換熱損失，從結構上對多孔 墻進行改進，設計了一種新型的多孔太陽墻系統。在多孔墻的集熱面與環境之間設玻璃蓋板，形成玻 璃通道。利用玻璃通道的“溫室效應”降低熱損失和收集熱空氣。在多孔墻內側通道內設有風機，在 風機的作用下，室外空氣流入多孔墻，與多孔墻進行熱交換后，被加熱到一定的溫度，用于冬季的供 暖。基于1維穩態Navier-Stoke方程、飽和多孔介質Bruikinaii-Foichlieuner Extended Darcy

9、模型和能量 雙方程模型，對這種設有風機并附加玻璃通道的新型的多孔太陽墻系統內的傳熱與流動特性進行數值 模擬。結果表明:風機的設計對系統內溫度場和流場有較大的影響;降低空氣入11流速，可減小空氣流 動阻力，提高多孔墻的集熱效率;附加玻璃通道的多孔太陽墻可減小長波輻射損失，并具有收集熱空氣 的作用。因此，它具有較高的集熱效率。設計了一種多孔蓄熱墻-溫室系統。將溫室北墻設計為由“半透明”的等徑、均勻的多孔球堆 枳而成的多孔墻，能吸收和蓄積太陽能，加熱溫室空氣，而且能夠主動地調節溫室內的熱環境。將溫 室與多孔蓄熱墻結合起來，充分發揮兩者的作用。從而提高了溫室的太陽能利用效果。借助帶內熱源 的飽和多孔介

10、質能量雙方程模型和Biinkiiiaii-Foiclilieunei- Extended Darcy模型以及k-。紊流模型，對 該太陽能溫室系統的傳熱與流動特性進行預測。在此基礎上，進一步模擬分析了孔隙率分層多孔墻對 溫室系統特性的影響。結果表明:溫室系統的入11參數和多孔墻的結構對溫室內的溫度場、流場和壓力 場有較大的影響。因此，針對一定結構的溫室系統，應根據溫室熱環境的要求，合理地設計多孔墻本 體，調節風機的運行工況。設計了兩種通風方式下的多孔太陽墻采暖系統。采用飽和多孔介質Biiiilaiian-Forclilieuner Extended Daicy模型、帶內熱源的能量雙方程模型以及k

11、-。紊流模型對采暖系統內的傳熱與流動特性 進行計算、分析和比較。結果表明，多孔太陽墻采暖系統的送排風方式，對采暖房內的溫度場、流場 有很大的影響，它直接影響到系統的保溫作用，對多孔墻的熱利用率有較大的影響。因此，在實際應 用中，應合理地設計多孔太陽墻采暖系統，提高多孔墻的熱利用率，從而降低多孔墻的熱價。對局部和斜坡地板送風式多孔太陽墻采暖系統內的傳熱與流動進行了數值模擬，得到了兩種 系統內的溫度分布、流場分布。分析了架空地板的結構、地板送風I I尺寸對采暖房內溫度場和流場的 影響;分析了建筑南墻對室內溫度的影響。結果表明:采用地板送風方式，能夠保證采暖房內均勻的溫 度場和流場;采用斜坡式地板送

12、風方式，更有利于保證各送風I I流量分布均勻。在實際應用中，應注意 建筑承重墻的隔熱，防止“熱蝕”現象發生。針對多孔墻的結構特點，采用描述填充結構的多孔介質模型，進一步分析了多孔墻的結構特 性。結果表明:增大顆粒直徑和孔隙率能夠降低系統的阻力。這一結果提供了優化多孔墻的結構參數。設計了多孔太陽墻測試系統，該系統能用于測試多孔太陽墻系統的阻力，多孔墻的吸收率和體積 換熱系數等特性參數。但由于太陽輻射的模擬是一個難點，因此，為了精確測試多孔墻的熱性能，還 需對測試系統進行改進。關鍵詞：太陽能干燥，強制對流，溫室干燥Fruit and vegetable solar drying dehydrati

13、on unit designABSTRACT: In tlus paper, a small scale solar drying equipment was designed based on tlie study of diymg characteristics of preserved Suits of “Study of Drying Cliaiacteristics of Preserved FruifThe test and applied reseaich of tlie solar drying equipment was studied and the application

14、 of die results of diSeient preserved fruits in tlie development of the solar diying equipment were analyzed compared to the tiaditional natuial sun drying, hot air diying. The optmnim conditions fbr drying preseived fruits under tlie solar diying equipment was to be find out and tlie advantages of

15、tlie diying equipment was also to be find out. The actual operation of tlie solai- equipment for plants was mvestigated.The chaiacteristics of tlie small scale solar diying devices is tlie reform of the Vplate solai- collectors, making it not only transported hot aii; but also stored heat in water.

16、The device was comprised of heat collector, drying room, small fan. water storage tank, blast pipe, pumps, temperature and humidity sensors, small heat exchangers, control valves and air filter. And it composed of a complete set of system to collect solar energy and hot air diymg system.Diymg proces

17、s duiiiig the daytime, the hot air was blew into the diying cliamber from tlie bottom of die collector. Hot air discliaiged from tlie chaiuber was sent back mto the chamber by tlie blower. When tlie diying cliamber temperature was too lugli tliaii desire, tlie automatic contiol valve opens to stored

18、 heat to the water tank by the heatmg collectors.Diymg process duiing the nighttune, when the teniperatuie sensor sensed tliat the mtenial temperatuie of the diying room was too low, the control valve uilet of the collector was intemipted, hot air blew from the pipe m the water tank mto tlie drying

19、chamber. The drying process was similar to tlie daytune diying process.When tlie second day started, tlie contiol valve uilet of the collector opened, collector plates began daytime drying process. The process was recycled to achieve continuous diying operation.Duiing poor weather conditions, tlie w

20、ater in the water tank was heated by tlie electiic, tlie control valve uilet of the collector was iiitermpted, hot ail blew from the pipe in die water tank mto tlie drying chamber.The diying process was similar to the daytime diying process. The advantage of tlie solar diying equipment was continuou

21、s heatmg, low cost, simple stmcture, lugli diymg and thermal efficiency.Ail- convection of tlie solar diymg equipment included natural convection aiid foicedconvection. And the diying chaiacteristics of tlie sample were studied in die solai drying equipment. Diying tune of die process of natural con

22、vection required to 14h to attain tlie diying requirement, wliile the process of forced convection diying tune requued 12h, for below the traditional tlie process of sun diying wliich lequued 5Oh. Durmg diying process of the saiuple. tlie Deff value was 1.39 x 10-6nr/s under the natuial convection,

23、wliile tlie Deff value was 1.26 x 10-6 m2/s under die forced convection for the drying process of the saiuple. The Devalue of two drying processes could unprove that the capacity of tlie water of tlie sample spread evenly.Chemical quality and sensory chaiacteristics of tlie plum samples were investi

24、gated under two diying metliods of the solar equipment. The experunent results showed tliat witli lower moisture content of the samples, the sugar content, acid content and the salt content of tlie sample mcreased at different layers of tlie diying room.For the color of the sample, the value of L* a

25、nd the value of a increased caused by non-eiizyiuatic browning. The peel and the pulp of tlie sample had tlie opposite tiend during the drying process for the value of b. The b value of peel decreased wliile tlie b value of pulp increased. All the experiment value was according to tlie foctoiy produ

26、ct quality reqiiuements.Chemical quality and seiisoiy cliaiacteristics of tlie plum samples were uivestigated in different layers of the solai- diyiiig equipment. Results show that appropriate adjustments to tlie location of materials were recommended dming natuial convection to miprove the quality

27、of the products. For the quality of products were relatively stable dming forced convection drying process, it had no needs for adjusting the position to miprove the quality of tlie sample.The reseaich of solar diying equipment under diffeient drying metliods showed that solar diyiiig device has obv

28、ious advantages compaied to natuial sun drying, greeiiliouse drying, oven drying. The diying tune of solar diying device was shortened up to 76%. while tlie total efficiency of the solar drying equipment was up to 63.4%.The diyiiig process under solar drying equipment was enviiomnental protection an

29、d energy conseivation. The drying enviioimient was with lugli temperature and low humidity. The product quality and diying efficiency was some kind of iiicreasiiig while tlie costs decreased in vaiying degrees. The equipment could meet the drying requuement of varieties of agricultural products.Samp

30、les were diied to taiget water content under different diymg methods, tlie natuial sun diymg took about 50h, while gieenliouse drying and oven drying took about 30h and 12h icspectively. Diyiiig tune of solar diying equipment under natuial convection and forced convection needed 14h and 12h respecti

31、vely. The moistuie content witluii 12h undeiibiced convection drying, oven drying, natural convection drying, natural suii diying and gieenliouse diymg were reduced to 58.08%, 57.08%, 60.21%, 64.32%, 69.22% respectively. The water activity of diied product which was dried to tlie same water content

32、imder five different diymg metliods reached tlie storage requuements and tlie product quality met the requuements of the factory. In all, the solar drying device obtained the best diymg effect.Fully aware of the analysis could be known tliat greenhouse diymg, natural convection and forced convection

33、 drying were investigated by using tlie self-made solar diymg equipment. The difference aiuong solai- drying equipment, tiaditional hot air drying and natural sun drying were also investigated. The test results provided theoretical basis fbr practical application of tlie selfniade solar diyiiig equi

34、pment to the factoiy production.The cliaiacteristics of discontmuity and disperse of solar radiation give a gieat difficulty in solar energy applications. The absoiption and storage of solar radiation has unpoitant effect on tlie utilization efficiency of solar energy. In heating builduigs and green

35、houses, the solar wall is a key part to mcoiporate tlie utilization of solar energy witli tlie building, and also subject studied by researchers at home and abroad. So. it is very important to study tlie solar wall. In this paper, actualities of investigations on solai wall at home and abroad aie an

36、alyzed. A new porous solar wall is designed by using the excellences of the porous composite Trombe wall and tlie porous absoiption solai wall. In addition, based on numerical simulation, tlie application and heat tiansfer performances of tlie porous solai- wall aie studied.For simplification, one-d

37、uneiisioiial niatlieniatic model is used to describe die heat tiansfer and flow in the porous solar wall. The flow and heat transfer in the porous wall witli tlie air as heat tiansfer medium are uivestigated prunaiily. To reach such conclusions, tlie porous wall can collect and store solar energy, a

38、nd heat air; The ak teniperatuie will increase with a decrease in die uilet velocity; On die premise of demand for solai- radiation collection, the ak temperature will increase witli an increase in die porosity and permeability of die porous wall; There are different results when metal and nomnetal

39、aie used as die inateiial of the porous matrix, respectively. The increase speed of tlie air temperature is quicker when aluminum is used as tlie material of die porous wall. Iii contiast, tlie uiciease speed of tlie ak temperature becomes slower when rock is used as the material of tlie porous wall

40、. Consequently; the permeability aiid material of the porous wall should be caiefiilly selected to reduce tlie cost of tlie porous solai- wall.Based on the tliernial analysis, the structure of the porous solar wall is unproved aiid a new porous solai wall is designed to reduce convection and radiati

41、on heat exchanges between the porous wall aiid the ambient. The glass plate is located between the porous wall aiid die ambient to form a glass duct, which can reduce heat losses and collect hot air by using Hgieeiiliouse efiectiveM. Additionally; the fail is located in tlie duct neai- the inside su

42、iiace of tlie porous wall. Under the action of the faiL tlie ambient air flows mto the porous wall aiid exclianges heat with tlie porous wall. Then the ail is heated to certain value to demand for heatmg m winter. Based on die two-dimensional steady Navier-Stokes equations, Bruikmaii-Forclilieuner E

43、xtended Darcy model and energy hvo-equation model for saturated porous medium, the flow aiid heat tiaiisfer in the new porous solar wall system witli glass duct and foil aie smiulated. The results show tliat tlie design of tlie fail has significant nifluence on tlie flow field aiid temperature field

44、, tlie flow resistance will decrease aiid tlie thermal efficiency of porous wall will uiciease witli a decrease m tlie inlet velocity; tlie porous wall with the glass duct can decrease lengtli-wave radiation aiid collect hot ak. So the new porous solar wall system can obtain a higher thermal efficie

45、ncy as compaied with a conventional one.A new greeiiliouse with heat-storage porous wall is designed, in which tlie noitli wall is a heat-storage porous wall. Equal diameter, uniform and senutraiispaient porous balls aie used as tlie material of tlie porous solai- wall, wliich can collect aiid store

46、 solar energy to heat tlie air in the gieenliouse, and condition die tliernial envkoimient in tlie greeiiliouse. Their effect both can be exerted fully by combinnig tlie gieeiiliouse witli the heat-storage porous wall, which causes the luglier solar energy utilization efficiency. Based on Bruikiiiai

47、i-Forclihemier Extended Darcy model and energy two-equation model witli mtenial heat source for satuiated porous medium k-E turbulent model, tlie flow and heat transfer cliaracteristics of solar gieeiiliouse system aie simulated. Additionally, the influence of tlie porous wall witli layered porosity

48、 on the cliaracteristics of tlie greeiiliouse is also analyzed by numerical smiulation fiutlier. The results show tliat the mlet paiaineters of tlie gieeiiliouse aiid the stiuctuie of the porous wall have gieat effect on tlie temperanue field, die flow field aiid tlie pressure field. So, for a certa

49、in stiuctuie of tlie gieeiiliouse. tlie porous wall should be designed and tlie foil operation should be also conditioned reasonably accordmg to the adniued tliernial envkoimient in tlie greeiiliouse.Two kuids of new solar heatmg systems with a new porous heat storage wall aie designed, wliich have

50、different ventilation patterns. Based on k-E turbulent model, Brnikmaii-Forcliliemiei- Extended Daicy model and energy two-equation model for saturated porous medium, tlie coupled heat tiansfer and flow cliaracteristics in tlie new solar heatmg system aie simulated, analyzed and compaied. The result

51、s show tliat ventilation pattern has great eSect on temperature field aiid flow field, which also has important uifluence on the insulation of tlie heating system and die theniial efficiency of tlie porous heat storage wall. Thus in real applications, tlie solar heating system with porous heat storage wall should be designed properly in order to mcrease the tliernial efficiency of porous solar wall and decrease die heatmg price for porous simul