梁 超,尹歡歡,李保明,王朝元
蛋雞舍熱濕環(huán)境參數(shù)全年逐時(shí)動(dòng)態(tài)預(yù)測(cè)模型
梁 超1,2,3,尹歡歡1,李保明1,2,3,王朝元1,2,3※
(1. 中國(guó)農(nóng)業(yè)大學(xué)水利與土木工程學(xué)院,北京 100083;2. 農(nóng)業(yè)農(nóng)村部設(shè)施農(nóng)業(yè)工程重點(diǎn)實(shí)驗(yàn)室,北京 100083;3. 北京市畜禽健康養(yǎng)殖環(huán)境工程技術(shù)研究中心,北京 100083)
準(zhǔn)確預(yù)測(cè)蛋雞舍內(nèi)溫度和相對(duì)濕度參數(shù)動(dòng)態(tài)變化是精準(zhǔn)調(diào)控舍內(nèi)熱濕環(huán)境的重要條件。然而,現(xiàn)有預(yù)測(cè)模型通常未能考慮濕簾降溫效率的變化及其對(duì)舍內(nèi)熱濕環(huán)境的影響。針對(duì)此問(wèn)題,該研究通過(guò)分析濕簾降溫效率變化規(guī)律和舍內(nèi)熱、濕平衡關(guān)系,構(gòu)建了蛋雞舍內(nèi)溫、濕度全年逐時(shí)動(dòng)態(tài)變化預(yù)測(cè)模型,并進(jìn)行了現(xiàn)場(chǎng)驗(yàn)證、案例展示和討論分析。結(jié)果表明:1)蛋雞舍內(nèi)溫、濕度模擬值與實(shí)測(cè)值變化趨勢(shì)一致,舍內(nèi)溫度的平均預(yù)測(cè)誤差為0.67 ℃,舍內(nèi)相對(duì)濕度的平均預(yù)測(cè)誤差為3.1%;2)因圍護(hù)結(jié)構(gòu)熱惰性而引起蛋雞舍內(nèi)溫度的延遲(夏季無(wú)延遲,冬季1 h)和衰減(夏季0.3 ℃,冬季1.02 ℃)均較?。?)若不考慮濕簾降溫效率的動(dòng)態(tài)變化,如設(shè)為80%定值時(shí),模擬的溫度誤差為1.4 ℃,相對(duì)濕度誤差為5.4%,模型預(yù)測(cè)精準(zhǔn)度降低。該研究可為蛋雞舍建筑設(shè)計(jì)與熱濕環(huán)境調(diào)控提供理論指導(dǎo),以提高蛋雞生產(chǎn)性能。
溫度;濕度;蛋雞舍;熱濕環(huán)境;濕簾;降溫效率;圍護(hù)結(jié)構(gòu)
適宜的舍內(nèi)環(huán)境是蛋雞生長(zhǎng)發(fā)育的必要條件,關(guān)系現(xiàn)代蛋雞品種優(yōu)良遺傳潛力能否充分發(fā)揮。其中,熱濕環(huán)境參數(shù)是影響蛋雞健康、生產(chǎn)性能以及蛋品質(zhì)量的重要因素[1-5]。舍內(nèi)溫度較高時(shí)會(huì)導(dǎo)致料蛋比增加、產(chǎn)蛋率下降,而溫度較低時(shí)蛋雞抵抗力會(huì)顯著下降[6-9]。舍內(nèi)濕度與溫度耦合則會(huì)影響雞只體熱調(diào)節(jié),進(jìn)而影響生產(chǎn)性能,例如,低溫高濕環(huán)境下容易誘發(fā)雞的呼吸道疾病,高溫高濕環(huán)境會(huì)加劇熱應(yīng)激而導(dǎo)致死淘率升高[10-13]。因此,通過(guò)模型精準(zhǔn)預(yù)測(cè)蛋雞舍內(nèi)溫、濕度的全年動(dòng)態(tài)變化及規(guī)律,有助于有效保障和精準(zhǔn)調(diào)控舍內(nèi)環(huán)境,以實(shí)現(xiàn)健康高效生產(chǎn)。
根據(jù)圍護(hù)結(jié)構(gòu)得熱量的不同計(jì)算方法,可將現(xiàn)有蛋雞舍熱濕環(huán)境參數(shù)預(yù)測(cè)模型分為穩(wěn)態(tài)模型和非穩(wěn)態(tài)模型2類。穩(wěn)態(tài)模型法是將圍護(hù)結(jié)構(gòu)得熱簡(jiǎn)化為二維穩(wěn)態(tài)傳熱,進(jìn)而全面分析蛋雞舍各環(huán)節(jié)的得熱量以實(shí)現(xiàn)舍內(nèi)熱濕環(huán)境參數(shù)的模擬預(yù)測(cè)。Cooper等[14]基于熱平衡分析并結(jié)合自然通風(fēng)、熱浮升力和太陽(yáng)輻射等因素影響,建立了可預(yù)測(cè)畜禽建筑內(nèi)部平均逐時(shí)溫度的穩(wěn)態(tài)模型。Zhao等[15]構(gòu)建了籠養(yǎng)蛋雞舍通風(fēng)量和熱負(fù)荷預(yù)測(cè)的穩(wěn)態(tài)數(shù)值模型,可以用于優(yōu)化雞舍環(huán)境條件和管理方案,Wang等[16]在該模型的基礎(chǔ)上系統(tǒng)分析了中國(guó)不同氣候區(qū)雞舍圍護(hù)結(jié)構(gòu)的最低熱阻值。Xie等[17-18]分別基于能質(zhì)平衡分析和深度學(xué)習(xí)建立了豬舍內(nèi)溫、濕度動(dòng)態(tài)預(yù)測(cè)模型,并結(jié)合實(shí)測(cè)數(shù)據(jù)確定了模型參數(shù),實(shí)現(xiàn)了豬舍內(nèi)溫、濕度變化規(guī)律的預(yù)測(cè)。然而,上述模型均未考慮濕簾系統(tǒng)降溫效率變化及其增濕作用對(duì)舍內(nèi)熱濕環(huán)境預(yù)測(cè)的影響。實(shí)際上,濕簾系統(tǒng)是蛋雞舍中最廣泛應(yīng)用的降溫方式[19-23],降溫效率的大小受過(guò)簾風(fēng)速以及濕簾材質(zhì)、結(jié)構(gòu)參數(shù)等因素影響明顯而變化范圍可達(dá)30%~95%[24-27]。
非穩(wěn)態(tài)模型法主要基于民用建筑能耗模擬軟件(包括DOE-2、EnergyPlus、TRNSYS、DeST等)進(jìn)行預(yù)測(cè)分析[28],充分考慮了圍護(hù)結(jié)構(gòu)的非穩(wěn)態(tài)傳熱特性。Bantle等[29]用DOE-2軟件對(duì)雞舍的全年能耗進(jìn)行了模擬,結(jié)果與實(shí)際能耗吻合度較高。王美芝等[30]用DeST模擬了不同通風(fēng)量和圍護(hù)結(jié)構(gòu)下肉牛舍的冬季舍溫。李琴等[31]用DeST模擬了控制舍內(nèi)相對(duì)濕度為70%時(shí)全國(guó)各氣候區(qū)兔舍內(nèi)對(duì)應(yīng)的溫度變化和所需通風(fēng)量。Ahachad等[32]用TRNSYS模擬了雞舍內(nèi)部溫度和冷負(fù)荷的變化,表明通風(fēng)、雞舍形狀和朝向、雞只數(shù)量是影響冷負(fù)荷的主要因素。但是,上述研究沒(méi)有模擬舍內(nèi)濕度變化,也未考慮濕簾降溫效率動(dòng)態(tài)變化及其影響。這主要是因?yàn)樯鲜鲕浖际腔诿裼媒ㄖ攸c(diǎn)開(kāi)發(fā),然而民用建筑較少采用濕簾降溫系統(tǒng),無(wú)法準(zhǔn)確考慮其對(duì)舍內(nèi)熱濕環(huán)境的影響。此外,蛋雞舍建筑與民用建筑在建筑形式、內(nèi)部產(chǎn)熱產(chǎn)濕、通風(fēng)需求等多方面也存在很大差異,導(dǎo)致相關(guān)參數(shù)設(shè)置受到了一定限制。
綜上可知,現(xiàn)有研究通常對(duì)蛋雞舍溫度和通風(fēng)量進(jìn)行模擬,缺少對(duì)濕度的動(dòng)態(tài)預(yù)測(cè),且未能考慮濕簾降溫效率動(dòng)態(tài)變化對(duì)舍內(nèi)熱濕環(huán)境的影響。因此,本研究在對(duì)濕簾降溫效率變化規(guī)律分析的基礎(chǔ)上,利用MATLAB軟件構(gòu)建蛋雞舍內(nèi)溫、濕度全年逐時(shí)動(dòng)態(tài)變化預(yù)測(cè)模型,通過(guò)現(xiàn)場(chǎng)測(cè)試進(jìn)行模型驗(yàn)證,并對(duì)該模型進(jìn)行案例展示與分析討論,以期為現(xiàn)代蛋雞舍建筑設(shè)計(jì)與環(huán)境調(diào)控提供理論指導(dǎo)和可靠工具借鑒。
蛋雞舍的濕簾系統(tǒng)通常和風(fēng)機(jī)配套使用以實(shí)現(xiàn)降溫,如圖1所示。
降溫效率是反映濕簾降溫效果優(yōu)劣的主要指標(biāo),且通常為非定值[24-27],因此在蛋雞舍熱濕環(huán)境參數(shù)模擬預(yù)測(cè)時(shí)需掌握降溫效率的變化規(guī)律。理論上,濕簾降溫基于直接蒸發(fā)冷卻原理,可近似視為等焓降溫加濕過(guò)程。針對(duì)濕簾等直接蒸發(fā)冷卻技術(shù),有學(xué)者通過(guò)分析其傳熱傳質(zhì)過(guò)程獲得了降溫效率的數(shù)學(xué)模型[33]
式中為降溫效率,%;為空氣密度,kg/m3;為過(guò)簾風(fēng)速,m/s;c為空氣定壓比熱容,J/(kg·℃);為濕簾比表面積,m2/m3;為空氣與濕簾材料表面的水之間的換熱系數(shù),W/(m2·℃);為濕簾厚度,m。
由式(1)可知,降溫效率與過(guò)簾風(fēng)速以及濕簾厚度、比表面積和換熱系數(shù)密切相關(guān),其中換熱系數(shù)還與濕簾材料、結(jié)構(gòu)以及使用過(guò)程的臟堵情況、濕潤(rùn)程度有關(guān)。蔣毅[34]將比表面積與換熱系數(shù)的綜合影響考慮為體積換熱系數(shù)h,通過(guò)試驗(yàn)擬合了濕簾常用纖維紙的體積換熱系數(shù)h=12.283 050.69922。將該系數(shù)代入式(1),可得
由式(2)和降溫效率的定義可求得經(jīng)濕簾降溫加濕后的空氣干球溫度t(℃)和含濕量d(kg/kg)
式中t為舍外空氣濕球溫度,℃;d為舍外空氣在飽和狀態(tài)下的含濕量,kg/kg;為水的汽化潛熱,J/kg。
根據(jù)熱力學(xué)第一定律可知,規(guī)模化蛋雞舍內(nèi)熱平衡方程如式(5)所示
式中t是蛋雞舍內(nèi)空氣溫度,℃;為時(shí)間,s;為蛋雞舍空間體積,m3;Q為蛋雞顯熱產(chǎn)熱量,W;Q為圍護(hù)結(jié)構(gòu)得熱量,W;Q為蛋雞舍供暖系統(tǒng)的供熱量,由于蛋雞舍內(nèi)通常無(wú)取暖設(shè)備,因此可忽略不計(jì),W;Q為蛋雞舍燈光、設(shè)備等發(fā)熱量,因發(fā)熱量較小可忽略不計(jì),W;Q為通風(fēng)排熱量,W。
國(guó)內(nèi)規(guī)?;半u舍飼養(yǎng)模式主要為疊層籠養(yǎng)[35],籠養(yǎng)蛋雞總產(chǎn)熱量Q可參考國(guó)際農(nóng)業(yè)和生物系統(tǒng)工程委員會(huì)(CIGR)指南,按式(6)計(jì)算[36]
式中Q為蛋雞總產(chǎn)熱量(即顯熱量Q與潛熱量Q之和,其中潛熱量Q以水汽的形式散發(fā)到雞舍內(nèi),將在全年逐時(shí)濕度預(yù)測(cè)模型中予以考慮),W;為雞只總質(zhì)量,kg;為產(chǎn)蛋量,kg/d。
進(jìn)而,蛋雞顯熱產(chǎn)熱量Q可根據(jù)蛋雞總產(chǎn)熱量Q計(jì)算,如下式[36]所示
蛋雞舍圍護(hù)結(jié)構(gòu)得熱量Q的計(jì)算,如式(8)所示
式中為圍護(hù)結(jié)構(gòu)的傳熱系數(shù),W/(m2·℃);為圍護(hù)結(jié)構(gòu)面積,m2;t為舍外綜合溫度,℃,可通過(guò)式(9)獲得
式中為舍外太陽(yáng)輻射強(qiáng)度,W/m2;ρ為圍護(hù)結(jié)構(gòu)外表面對(duì)太陽(yáng)輻射的吸收系數(shù);h為圍護(hù)結(jié)構(gòu)外表面換熱系數(shù),W/(m2·℃);ρ和h可參考《民用建筑熱工設(shè)計(jì)規(guī)范》[37]取值。
通風(fēng)排熱量Q可按下式計(jì)算
式中為通風(fēng)質(zhì)量流量,kg/s;t為經(jīng)濕簾降溫后的空氣溫度,濕簾開(kāi)啟時(shí)用式(3)計(jì)算,濕簾未開(kāi)啟時(shí)即為舍外空氣干球溫度t。
另外,上述公式涉及的舍外空氣溫度、濕度、太陽(yáng)輻射強(qiáng)度等參數(shù),將從建筑模擬軟件DeST的中國(guó)各地區(qū)典型年逐時(shí)氣象數(shù)據(jù)獲取,它由中國(guó)氣象局氣候數(shù)據(jù)中心和清華大學(xué)根據(jù)數(shù)十年歷史氣象數(shù)據(jù)共同研發(fā)[38]。
將式(3)和式(6)~(10)代入式(5)即可獲得蛋雞舍內(nèi)溫度動(dòng)態(tài)變化預(yù)測(cè)模型,如式(11)所示。從而,基于MATLAB搭建模型和編寫(xiě)程序,并以1 h為時(shí)間步長(zhǎng),可計(jì)算蛋雞舍內(nèi)全年逐時(shí)(即8 760 h)變化的溫度值。
根據(jù)質(zhì)量守恒原理可知,規(guī)?;半u舍內(nèi)濕平衡方程如式(12)所示
式中d為舍內(nèi)空氣含濕量,kg/kg;W為雞只產(chǎn)濕量,kg/s;W為舍內(nèi)各表面散濕量,kg/s,可忽略不計(jì);W為通風(fēng)排濕量,kg/s。
雞只產(chǎn)濕量W可根據(jù)雞只潛熱產(chǎn)熱量Q獲得
式中為水蒸氣的汽化潛熱,J/kg。
通風(fēng)排濕量W可按下式計(jì)算獲得
式中d為經(jīng)濕簾加濕后的空氣含濕量,濕簾開(kāi)啟時(shí)用式(4)計(jì)算,濕簾未開(kāi)啟時(shí)即為舍外空氣含濕量d。
將式(4)和式(13)~(14)代入式(12)即可獲得蛋雞舍內(nèi)濕度動(dòng)態(tài)變化預(yù)測(cè)模型,如式(15)所示。從而,基于MATLAB搭建模型和編寫(xiě)程序,并以1 h為時(shí)間步長(zhǎng),可計(jì)算蛋雞舍內(nèi)濕度的全年逐時(shí)動(dòng)態(tài)變化值。
2019年7月在河北邯鄲某蛋種雞場(chǎng)進(jìn)行了現(xiàn)場(chǎng)試驗(yàn),以驗(yàn)證該模型的準(zhǔn)確性。試驗(yàn)蛋雞舍為東西走向,長(zhǎng)100 m、寬12 m、檐高5 m。舍內(nèi)蛋雞飼養(yǎng)密度為19.6只/m2,周齡為55周,質(zhì)量為1.5 kg,產(chǎn)蛋量為50 g/(d·只)。圍護(hù)結(jié)構(gòu)主體為夾心彩鋼板,彩鋼板單板厚度為0.5 mm,夾心泡沫板厚150 mm。內(nèi)部為四列五走道布置形式,采用四疊層籠養(yǎng)模式,且呈上下各兩層分布。16臺(tái)風(fēng)機(jī)安裝在西側(cè)山墻,濕簾安裝在東側(cè)山墻以及南北兩側(cè)墻,濕簾均為7090型且高1.75 m、長(zhǎng)9 m、厚0.15m。
蛋雞舍內(nèi)溫濕度使用HOBO U23-001(精度:±0.2 ℃,±2.5%)進(jìn)行連續(xù)測(cè)量,每5 min 采集存儲(chǔ)1次。如圖2所示,溫濕度監(jiān)測(cè)點(diǎn)設(shè)在中間、兩側(cè)走道且靠近雞只活動(dòng)區(qū)域,其中豎直方向均勻布置2個(gè)測(cè)點(diǎn),水平方向均勻布置4個(gè)測(cè)點(diǎn),另外濕簾以及風(fēng)機(jī)附近各布置1個(gè)測(cè)點(diǎn),合計(jì)26個(gè)測(cè)點(diǎn)。每臺(tái)風(fēng)機(jī)的風(fēng)速使用熱線風(fēng)速儀(精度:3%讀數(shù))測(cè)量,風(fēng)速與表面積乘積可求出每臺(tái)風(fēng)機(jī)的風(fēng)量,并在控制柜安裝風(fēng)機(jī)運(yùn)行監(jiān)測(cè)裝置實(shí)時(shí)監(jiān)測(cè)各風(fēng)機(jī)的運(yùn)行狀態(tài),從而實(shí)時(shí)得到舍內(nèi)通風(fēng)量。在雞舍屋頂安裝氣象站以連續(xù)監(jiān)測(cè)舍外溫濕度(精度:±0.2 ℃,±2.5%),且溫濕度傳感器采用錫紙包裹以避免太陽(yáng)直射的影響。在東側(cè)墻以及屋頂安裝太陽(yáng)總輻射傳感器(精度:2%讀數(shù))以連續(xù)監(jiān)測(cè)舍外太陽(yáng)總輻射強(qiáng)度,每1 h采集存儲(chǔ)1次,其他朝向墻體的太陽(yáng)輻射強(qiáng)度用朝向修正系數(shù)進(jìn)行修正[16]。此外,該試驗(yàn)雞舍的濕簾運(yùn)行狀態(tài)主要由舍內(nèi)溫度反饋控制,當(dāng)舍內(nèi)溫度高于28 ℃時(shí)濕簾開(kāi)啟,低于28 ℃時(shí)濕簾關(guān)閉。
將上述測(cè)量獲得的通風(fēng)量、圍護(hù)結(jié)構(gòu)、氣象等數(shù)據(jù)輸入本文構(gòu)建的預(yù)測(cè)模型中,可計(jì)算獲得試驗(yàn)雞舍內(nèi)逐時(shí)溫、濕度。由于試驗(yàn)舍內(nèi)溫、濕度分布存在一定的不均勻性,通過(guò)統(tǒng)計(jì)26個(gè)測(cè)點(diǎn)平均值來(lái)代表舍內(nèi)溫、濕度的實(shí)測(cè)值。將舍內(nèi)溫濕度預(yù)測(cè)值與舍內(nèi)、外溫濕度實(shí)測(cè)值進(jìn)行對(duì)比,結(jié)果如圖3所示。
由圖3可以看出,舍內(nèi)溫、濕度模擬值與實(shí)測(cè)值變化趨勢(shì)一致,溫度的平均預(yù)測(cè)誤差為0.67 ℃,相對(duì)濕度的平均預(yù)測(cè)誤差為3.1%。誤差可能來(lái)源于圍護(hù)結(jié)構(gòu)和濕簾因使用年限較長(zhǎng)而導(dǎo)致物性參數(shù)預(yù)估存在一定偏差,以及受到滲風(fēng)、噴霧消毒、噴水、清掃、清糞、人員進(jìn)出等生產(chǎn)活動(dòng)的影響??傮w而言,上述誤差在可接受范圍內(nèi),表明蛋雞舍熱濕環(huán)境參數(shù)動(dòng)態(tài)變化預(yù)測(cè)模型的準(zhǔn)確性得到驗(yàn)證。
為了更好地理解本文構(gòu)建的預(yù)測(cè)模型,這里進(jìn)行案例展示和應(yīng)用分析。假設(shè)某一長(zhǎng)100 m、寬10 m、檐高5 m的蛋雞舍。模型中將不同地區(qū)的圍護(hù)結(jié)構(gòu)材料、尺寸、飼養(yǎng)密度、通風(fēng)量等參數(shù)設(shè)為相同,以便于模型展示和結(jié)果對(duì)比。飼養(yǎng)密度設(shè)定為25只/m2,雞只質(zhì)量設(shè)定為1.5 kg。夏季通風(fēng)量設(shè)定為45 m3/s,冬季為7.5 m3/s,春、秋季為23.5 m3/s。圍護(hù)結(jié)構(gòu)采用150 mm夾心彩鋼板,濕簾面積設(shè)定為90 m2,濕簾開(kāi)啟及關(guān)閉由舍內(nèi)溫度控制,當(dāng)溫度大于等于28 ℃時(shí)開(kāi)啟濕簾,小于28 ℃時(shí)關(guān)閉濕簾。這里以武漢和哈爾濱2個(gè)地區(qū)為例進(jìn)行展示,結(jié)果如圖4和5所示。
由圖4可以看出,武漢地區(qū)蛋雞舍在冬季基本能夠滿足熱濕環(huán)境要求,舍內(nèi)溫度大部分位于10~25 ℃之間。但是,在夏季特別是7、8月時(shí),舍內(nèi)溫度大部分高于28 ℃且相對(duì)濕度高于80%,高溫高濕環(huán)境將會(huì)影響雞只健康和降低生產(chǎn)性能。這主要是因?yàn)槲錆h為高溫高濕氣候條件而導(dǎo)致夏季時(shí)濕簾降溫效果相對(duì)較差。因此,在以武漢為代表的夏熱冬冷地區(qū),可考慮在夏季高溫季節(jié)適宜增大通風(fēng)量(特別是籠間風(fēng)速)等措施以更好滿足蛋雞舍內(nèi)熱濕環(huán)境要求。
由圖5可以看出,哈爾濱地區(qū)蛋雞舍在夏季基本能夠滿足熱濕環(huán)境要求,舍內(nèi)溫度主要位于12~27 ℃之間。但是,冬季受低溫氣候條件影響使舍內(nèi)溫度通常低于13 ℃,甚至經(jīng)常性達(dá)到零度以下,而將影響蛋雞健康和生產(chǎn)性能。因此,在以哈爾濱為代表的嚴(yán)寒地區(qū),需要綜合考慮適宜的飼養(yǎng)密度,增強(qiáng)圍護(hù)結(jié)構(gòu)保溫性能,在滿足舍內(nèi)空氣質(zhì)量條件下適度降低通風(fēng)量,甚至額外增加供熱設(shè)備等措施,以滿足舍內(nèi)良好的熱濕環(huán)境要求。
本文所建立的預(yù)測(cè)模型將圍護(hù)結(jié)構(gòu)傳熱過(guò)程簡(jiǎn)化為穩(wěn)態(tài)傳熱,實(shí)際上它因熱惰性而屬于非穩(wěn)態(tài)傳熱,對(duì)蛋雞舍內(nèi)溫度可能存在衰減和延遲的影響。為了評(píng)估其對(duì)預(yù)測(cè)模型的影響,這里將以DeST軟件的非穩(wěn)態(tài)模擬結(jié)果作為參照來(lái)進(jìn)行對(duì)比分析。此外,由于DeST軟件主要面向民用建筑而無(wú)法設(shè)置濕簾,對(duì)比分析時(shí)DeST模型和本文預(yù)測(cè)模型中均沒(méi)有考慮濕簾。假設(shè)北京某一蛋雞舍長(zhǎng)100 m,寬10 m,檐高5 m,圍護(hù)結(jié)構(gòu)主體采用150 mm厚夾心彩鋼板。飼養(yǎng)密度為20只/m2,雞只質(zhì)量設(shè)定為1.5 kg,產(chǎn)蛋量為50 g/(d·只)。夏季通風(fēng)量設(shè)置為40 m3/s,冬季通風(fēng)量設(shè)置為9 m3/s。
同一設(shè)置條件下,DeST軟件與本文預(yù)測(cè)模型的夏季(僅展示7月份)模擬值的對(duì)比結(jié)果如圖6a所示,冬季(僅展示1月份)模擬值的對(duì)比結(jié)果如圖6b所示。
圖6a可知,預(yù)測(cè)模型模擬獲得的夏季舍內(nèi)溫度值與DeST模擬值無(wú)顯著差異,平均誤差僅為0.36 ℃,且變化規(guī)律幾乎一致。此外,可以看出預(yù)測(cè)模型與DeST軟件的兩舍內(nèi)溫度曲線幾乎重合,沒(méi)有延遲。這表明,夏季時(shí)蛋雞舍圍護(hù)結(jié)構(gòu)的非穩(wěn)態(tài)傳熱可近似為穩(wěn)態(tài)傳熱。
圖6b可知,相比于夏季,預(yù)測(cè)模型與DeST軟件模擬的冬季舍內(nèi)溫度值相差更大一些,平均誤差為1.02 ℃,表明冬季時(shí)蛋雞舍圍護(hù)結(jié)構(gòu)熱惰性對(duì)舍內(nèi)熱環(huán)境起到一定的穩(wěn)定作用。此外,可以看出兩溫度曲線存在1 h左右的延遲,但遠(yuǎn)低于民用建筑圍護(hù)結(jié)構(gòu)的延遲時(shí)間(10 h甚至更長(zhǎng))[39],表明冬季時(shí)蛋雞舍建筑圍護(hù)結(jié)構(gòu)的延遲作用也很小。
綜上可知,蛋雞舍圍護(hù)結(jié)構(gòu)非穩(wěn)態(tài)傳熱過(guò)程簡(jiǎn)化為穩(wěn)態(tài)傳熱的誤差較?。ㄋp和延遲均較?。?,而這與民用建筑的相關(guān)結(jié)果差別較大。主要原因是蛋雞舍的高養(yǎng)殖密度導(dǎo)致其通風(fēng)換氣次數(shù)(夏季100次/h,冬季5次/h)遠(yuǎn)大于民用建筑(夏季10次/h,冬季0.5次/h)[39],而通風(fēng)換氣可在瞬間完成換熱且熱量占比很大,從而削弱了圍護(hù)結(jié)構(gòu)的衰減和延遲作用。
目前很多研究中通常將濕簾降溫效率簡(jiǎn)化為定值80%[40-41],而實(shí)際上它隨很多因素(比如過(guò)簾風(fēng)速)變化[24-27]。為了說(shuō)明降溫效率的變化對(duì)蛋雞舍內(nèi)溫濕度預(yù)測(cè)的重要性,仍以第2節(jié)現(xiàn)場(chǎng)測(cè)試的邯鄲某雞舍為研究對(duì)象,將降溫效率取為定值80%和變值(即式(2))分別對(duì)舍內(nèi)溫濕度進(jìn)行模擬預(yù)測(cè),并與現(xiàn)場(chǎng)實(shí)測(cè)值進(jìn)行對(duì)比分析。這里選取7月28日的對(duì)比結(jié)果進(jìn)行展示,如圖7所示。
圖7可以看出,夜晚時(shí)舍內(nèi)溫度較低而關(guān)閉濕簾,從而變降溫效率和定降溫效率所模擬獲得的舍內(nèi)溫濕度基本一致。白天時(shí)(特別是中午及下午)舍外氣溫升高、太陽(yáng)輻射變強(qiáng)而開(kāi)啟濕簾,此時(shí)變降溫效率與定降溫效率模擬獲得的舍內(nèi)溫濕度將不一致。定降溫效率模擬時(shí),舍內(nèi)溫度值與實(shí)測(cè)值最大相差1.4 ℃(大于0.67 ℃),舍內(nèi)相對(duì)濕度值與實(shí)測(cè)值最大相差5.4%(大于3.1%),均大于變降溫效率模擬時(shí)的誤差。由此可以說(shuō)明,模擬預(yù)測(cè)蛋雞舍內(nèi)溫濕度時(shí),需考慮濕簾降溫效率隨過(guò)簾風(fēng)速等因素變化的實(shí)際情況,以提高預(yù)測(cè)精度。
本文基于濕簾降溫效率數(shù)學(xué)模型以及舍內(nèi)熱濕平衡方程,構(gòu)建了可考慮濕簾降溫效率變化規(guī)律的蛋雞舍內(nèi)溫、濕度全年逐時(shí)動(dòng)態(tài)變化預(yù)測(cè)模型,并通過(guò)現(xiàn)場(chǎng)測(cè)試驗(yàn)證了模型的準(zhǔn)確性,最后對(duì)模型進(jìn)行了案例展示與討論分析,主要結(jié)論如下:
1)蛋雞舍內(nèi)溫、濕度模擬值與實(shí)測(cè)值變化趨勢(shì)一致,溫度的平均預(yù)測(cè)誤差為0.67 ℃,相對(duì)濕度的平均預(yù)測(cè)誤差為3.1%,表明該模型能夠較好地預(yù)測(cè)蛋雞舍內(nèi)熱濕環(huán)境參數(shù)的動(dòng)態(tài)變化。
2)蛋雞舍因圍護(hù)結(jié)構(gòu)熱惰性而引起舍內(nèi)溫度的延遲(夏季無(wú)延遲,冬季1 h)和衰減(夏季0.36 ℃,冬季1.02 ℃)均較小。這主要是因?yàn)榈半u舍通風(fēng)換氣次數(shù)大,可在很短時(shí)間內(nèi)完成換熱,從而削弱了圍護(hù)結(jié)構(gòu)蓄熱的衰減和延遲效果。
3)若不考慮濕簾降溫效率的變化規(guī)律,將降低蛋雞舍內(nèi)溫濕度全年逐時(shí)預(yù)測(cè)模型的精準(zhǔn)度。降溫效率設(shè)為定值80%時(shí),蛋雞舍內(nèi)溫度值的預(yù)測(cè)誤差可達(dá)1.4 ℃,相對(duì)濕度的預(yù)測(cè)誤差可達(dá)5.4%。
本文構(gòu)建的蛋雞舍熱濕環(huán)境參數(shù)全年逐時(shí)動(dòng)態(tài)變化預(yù)測(cè)模型,將可為蛋雞舍的建筑設(shè)計(jì)和熱濕環(huán)境調(diào)控提供理論指導(dǎo)和工具參考。
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Hourly model for predicting year-round temperature and relative humidity of the environment in laying hen houses
Liang Chao1,2,3, Yin Huanhuan1, Li Baoming1,2,3, Wang Chaoyuan1,2,3※
(1.,,100083,; 2.,,100083,; 3.,100083,)
Laying hen house is an important part of livestock industries, particularly with an intensification scale of over 70% in China. Appropriate indoor temperature and relative humidity are also critical to the health of birds, production performance, and egg quality, further fully exploiting the excellent genetic features of modern laying hens. An automatic control system is, therefore, necessary to precisely predict the dynamic changes of indoor temperature and relative humidity for laying hen houses. An evaporative cooling pad system is the most popular used to increase the accuracy of the prediction model in laying hen houses in summer. However, most currently-used prediction models usually fail to consider the cooling variation of the evaporative cooling pad system. Particularly, it is also lacking to consider the humidified impact on the indoor temperature and relative humidity in laying hen houses. In this study, a novel hourly model was created to predict the annual indoor temperature and relative humidity, as well as its variation in laying hen houses. A mathematical model of cooling efficiency was also adopted to consider the quantitative influence of the evaporative cooling pad system on the indoor thermal and humid environment. A field experiment was then conducted to verify the model in Handan, Hebei Province of China in July 2019. Twenty-six points of indoor temperature and relative humidity were set for the field measurement. A hot-wire anemometer was utilized to monitor the airflow rate of exhaust fans. Meanwhile, an outdoor meteorological station was installed on the roof to continuously record the climatic parameters. Moreover, two cases were carried out in Wuhan City and Harbin City of China to evaluate the performance of the prediction model, thereby analyzing the influence of different climate conditions on the indoor environment of laying hen houses. Finally, the prediction model was used to clarify the difference of heat transfer in the steady and dynamic state for the building envelope on the indoor thermal and humid environment of laying hen houses. The accuracy of the prediction model was obtained between the constant and variable evaporative cooling efficiencies. The results demonstrated that the predicted values of indoor temperature and relative humidity were consistent with the field measured ones. Specifically, the overall average error of indoor temperature was 0.67 ℃, and the average error of indoor relative humidity was 3.1%. It was found that there was no temperature delay in summer and only one hour delay in winter. Temperature attenuation presented 0.36 ℃ in summer and 1.02 ℃ in winter, indicating a negligible effect due to the thermal inertia of the enclosure. The variation of dynamic cooling efficiency was contributed to the higher accuracy of the prediction model in the evaporative cooling pad system. For example, the predicted error of temperature reduced from 1.4 ℃ to 0.67 ℃, and the error of relative humidity from 5.4% to 3.1%, when the cooling efficiency was fixed at 80%. Consequently, this finding can provide potential theoretical guidance for building design and thermal environment control of laying hens houses, and further improve the production performance of laying hens.
temperature; humidity; laying hen house; thermal environment; evaporative cooling pad; cooling efficiency; envelope
10.11975/j.issn.1002-6819.2021.08.026
S26
A
1002-6819(2021)-08-0229-07
梁超,尹歡歡,李保明,等. 蛋雞舍熱濕環(huán)境參數(shù)全年逐時(shí)動(dòng)態(tài)預(yù)測(cè)模型[J]. 農(nóng)業(yè)工程學(xué)報(bào),2021,37(8):229-235.doi:10.11975/j.issn.1002-6819.2021.08.026 http://www.tcsae.org
Liang Chao, Yin Huanhuan, Li Baoming, et al. Hourly model for predicting year-round temperature and relative humidity of the environment in laying hen houses[J].Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(8): 229-235. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2021.08.026 http://www.tcsae.org
2020-12-17
2021-03-11
國(guó)家重點(diǎn)研發(fā)計(jì)劃(2017FYD0701602、2017YFE0122200);博士后創(chuàng)新人才支持計(jì)劃(BX20180363);國(guó)家現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系(CARS-40)
梁超,博士,副教授,碩士生導(dǎo)師,研究方向?yàn)檗r(nóng)業(yè)建筑節(jié)能減排。Email:liangchao@cau.edu.cn
王朝元,博士,教授,博士生導(dǎo)師,研究方向?yàn)樵O(shè)施畜禽養(yǎng)殖過(guò)程與環(huán)境控制。Email:gotowchy@cau.edu.cn
中國(guó)農(nóng)業(yè)工程學(xué)會(huì)高級(jí)會(huì)員:王朝元(E041200616S)