高 云,刁亞萍,林長光,劉亞軒,郭長明,雷明剛,童 宇,黎 煊
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機械通風(fēng)樓房豬舍熱環(huán)境及有害氣體監(jiān)測與分析
高 云1,2,刁亞萍1,林長光3,劉亞軒3,郭長明3,雷明剛2,4,童 宇1,2,黎 煊1,2
(1.華中農(nóng)業(yè)大學(xué)工學(xué)院,武漢 430070;2. 生豬健康養(yǎng)殖協(xié)同創(chuàng)新中心,武漢 430070; 3. 福建光華百斯特生態(tài)農(nóng)牧發(fā)展有限公司,三明 365106; 4.華中農(nóng)業(yè)大學(xué)動物科技學(xué)院動物醫(yī)學(xué)院,武漢 430070)
樓房養(yǎng)豬模式提高了養(yǎng)殖密度,節(jié)約了土地資源,同時也帶來了養(yǎng)殖企業(yè)對飼養(yǎng)環(huán)境的關(guān)注。該文以樓房豬舍為監(jiān)測對象,采用無線傳感網(wǎng)絡(luò)多點部署的方法連續(xù)24 h監(jiān)測不同樓層豬舍的溫?zé)岘h(huán)境和有害氣體等環(huán)境因子參數(shù)分布,對比和分析不同樓層間以及同一樓層內(nèi)不同位置間熱環(huán)境和有害氣體分布的差異性。以每樓層動物所需通風(fēng)率為基準(zhǔn),將通風(fēng)情況劃分為欠通風(fēng)、合適通風(fēng)和過通風(fēng)3種水平,結(jié)果顯示中間層(保育豬1960頭,10.8±1.9 kg)欠通風(fēng)造成溫濕度指標(biāo)THI(temperature and humidity index)平均值達27.9,接近舒適區(qū)上限28.06。受頂層輻射和底層保溫影響,頂層(生長豬940頭,51±4.4 kg)溫度最大值比底層(生長豬955頭,40±3.6 kg)高2.8 ℃,頂層晝夜溫度最大差值達11.6 ℃。底層濕度高,相對濕度達85.7%。夏季通風(fēng)條件下,各樓層內(nèi)的CO2和NH3濃度遠低于最高濃度限值,欠通風(fēng)豬舍CO2和NH3分布不均,且較難排出,其中NH3濃度受豬舍內(nèi)尿液排出方式影響。各樓層溫?zé)岷陀泻怏w環(huán)境差異性顯著,同一層豬舍不同位置環(huán)境存在差異。該研究為優(yōu)化樓房養(yǎng)豬機械通風(fēng)設(shè)計,提高樓房養(yǎng)豬環(huán)境控制水平提供理論依據(jù)。
溫度;濕度;通風(fēng);樓房豬舍;熱環(huán)境;有害氣體;THI;差異性分析
自2014年1月1日《畜禽規(guī)模養(yǎng)殖污染防治條例》[1]實施起,環(huán)保政策密集出臺,養(yǎng)殖用地日見緊張。為了節(jié)約養(yǎng)豬用地,全國各地樓房養(yǎng)豬正在興起。樓房養(yǎng)豬作為一種新興的養(yǎng)豬模式,既節(jié)約用地,也便于進行生物安全管理,同時由于不同樓層豬舍有高低落差,方便污水污糞的集中處理。國內(nèi)的樓房養(yǎng)豬是順應(yīng)國內(nèi)緊縮養(yǎng)殖用地的政策出現(xiàn),國外鮮有相關(guān)研究報道。樓房養(yǎng)豬不同于平房養(yǎng)豬,由于缺少閣樓等建筑結(jié)構(gòu),在豬舍內(nèi)的機械通風(fēng)系統(tǒng)設(shè)計上,無法采用屋頂風(fēng)機和屋頂進風(fēng)口等通風(fēng)結(jié)構(gòu),目前大部分樓房豬舍使用縱向通風(fēng)設(shè)計。另外,不同樓層與外部環(huán)境的熱交換情況有一定差異,如頂層熱輻射,底層地板保溫等影響,可能導(dǎo)致相同面積,相似的通風(fēng)系統(tǒng)條件不同樓層中的環(huán)境控制效果有差異,從而對養(yǎng)豬生產(chǎn)造成較大的影響。因此有必要弄清不同樓層豬舍內(nèi)部環(huán)境的規(guī)律,并針對不同樓層特點在豬舍通風(fēng)系統(tǒng)設(shè)計以及運行方式上做進一步的調(diào)整和優(yōu)化。
通常用來衡量豬舍環(huán)境的參數(shù)指標(biāo)包括熱環(huán)境和有害氣體參數(shù)等。熱環(huán)境指標(biāo)主要以溫度和濕度參數(shù)為主,另外還包括熱輻射、大氣壓、光照等[2]。有害氣體指標(biāo)主要有CO2、NH3、H2S,其中CO2是一種溫室氣體[3-7],常用作計算通風(fēng)率的示蹤氣體[8-12]。比如在美國國家空氣排放監(jiān)測研究(NAEMS)項目中,Heber等[13-14]連續(xù)2 a監(jiān)測了15棟豬舍的溫濕度、有害氣體(包括CO2、NH3、H2S等)、通風(fēng)率、外部氣候、靜壓差、光照、動物和工人的活動等。除此以外,顆粒物、臭氣、VOC、病菌的濃度和排放率也常作為豬舍內(nèi)的環(huán)境監(jiān)測指標(biāo)[15-18]。根據(jù)行業(yè)內(nèi)的標(biāo)準(zhǔn)和共識,豬舍內(nèi)CO2、NH3和H2S的職業(yè)衛(wèi)生最高質(zhì)量濃度分別不超過9 819.3,19.0和15.2 mg/m3[19-21],從豬的健康角度,CO2不應(yīng)超過3 024.3 mg/m3,NH3不應(yīng)超過8.4 mg/m3[21]。豬舍內(nèi)的CO2主要產(chǎn)生于動物的呼吸和糞便的分解,其排放量與豬的生理階段和體重,進食成分相關(guān)[22-23];NH3主要來源于尿液中的尿素快速水解[24],其排放量與品種和生長階段、氣候變化、糞便處理方式、豬舍結(jié)構(gòu)都密切相關(guān)[25-28]。H2S由糞便分解產(chǎn)生,目前在國內(nèi)集約化豬舍內(nèi)的質(zhì)量濃度普遍不高,多數(shù)在0.2 mg/m3以下[29],遠低于對動物有害水平。
為了監(jiān)測豬舍內(nèi)的環(huán)境參數(shù),從20世紀(jì)90年代中期開始,計算機和傳感器等技術(shù)在豬舍環(huán)境監(jiān)測系統(tǒng)中大量采用。數(shù)字式溫濕度傳感器給畜禽舍內(nèi)溫濕度測量提供了便利條件。有害氣體濃度的測量從化學(xué)分析法[30-32],發(fā)展到光聲多氣體監(jiān)測、傅里葉變換紅外光譜、氣相色譜-質(zhì)譜[33-34]等氣體分析方法。便攜式有害氣體傳感器也從電化學(xué)傳感器發(fā)展為紅外或激光氣體傳感器。電化學(xué)氣體傳感器短期測量數(shù)據(jù)準(zhǔn)確,但長期使用易受其他氣體影響。紅外或激光氣體傳感器具有長期穩(wěn)定的特點,但價格較為昂貴。在測量數(shù)據(jù)傳輸方面,通信網(wǎng)絡(luò)也由RS-485,CAN總線發(fā)展為以太網(wǎng)TCP/IP協(xié)議,組網(wǎng)也由有線發(fā)展為WIFI、Zigbee等無線網(wǎng)絡(luò)[35-37]。無線傳感器網(wǎng)絡(luò)在精確監(jiān)測豬舍內(nèi)部環(huán)境的同時,還具有良好的兼容性,能與豬舍內(nèi)環(huán)境調(diào)控設(shè)備集成為完整系統(tǒng)[38-40],以確保豬舍內(nèi)通風(fēng)系統(tǒng)的有效運行。
為了掌握不同樓層豬舍內(nèi)部環(huán)境的規(guī)律,本文基于無線傳感器環(huán)境監(jiān)測網(wǎng)絡(luò),采用在樓房豬舍內(nèi)多點布置無線傳感器的方法,對不同樓層的豬舍進行24 h監(jiān)測,測量每樓層內(nèi)的溫濕度,CO2和NH3濃度,進行差異性分析,計算溫濕度指標(biāo)THI。為了考察豬舍內(nèi)通風(fēng)環(huán)境在較熱氣候條件下的運行情況,監(jiān)測選擇在春夏交替氣候條件下(室外氣溫為17.3~31.5 ℃)進行,以期掌握多樓層豬舍內(nèi)部的環(huán)境特征,為優(yōu)化多樓層養(yǎng)豬通風(fēng)系統(tǒng),改善多樓層養(yǎng)豬的內(nèi)部環(huán)境提供理論依據(jù)。
1.1.1 無線傳感網(wǎng)絡(luò)監(jiān)測系統(tǒng)結(jié)構(gòu)
現(xiàn)代集約化豬場的豬舍面積逐步增大,多點部署傳感器測點才能有效監(jiān)測豬舍內(nèi)存在環(huán)境不均衡現(xiàn)象。本文采用在一層豬舍內(nèi)多點均勻部署無線傳感器測點的方式,來測量豬舍內(nèi)部環(huán)境分布。每個無線傳感器測點集成有溫、濕度,CO2和NH3傳感器。
無線傳感網(wǎng)絡(luò)(WSN,wireless sensor network)監(jiān)測系統(tǒng)結(jié)構(gòu)如圖1所示,包括無線傳感器測點(數(shù)據(jù)采集前端)、中繼(或中轉(zhuǎn)節(jié)點)、網(wǎng)關(guān)(邊緣路由器)、路由器、PC機(數(shù)據(jù)存儲和信息監(jiān)控)、應(yīng)用終端(信息管理)。
圖1 多環(huán)境因子無線傳感網(wǎng)絡(luò)監(jiān)測系統(tǒng)結(jié)構(gòu)
無線傳感器測點由CC2530控制模塊、傳感器模塊(包括溫、濕度,CO2和NH3傳感器),無線收發(fā)模塊,供電電源管理模塊組成,采用8 800 mAh/7.4 V的鋰電池供電,在每5 min采樣1次的情況下,可供整個網(wǎng)絡(luò)連續(xù)工作4×24 h。每次采樣設(shè)置3 min傳感器預(yù)熱時間,采樣間隙測點進入PM2低功耗模式,電流僅為8A。中繼通過網(wǎng)關(guān)將采集數(shù)據(jù)轉(zhuǎn)換為IPv4協(xié)議數(shù)據(jù),由內(nèi)部局域網(wǎng)或者Internet外網(wǎng)傳輸至PC機。PC機上安裝的基于Visual Studio 2012(Microsoft,美國)的軟件平臺開發(fā)的專用數(shù)據(jù)采集軟件,從網(wǎng)絡(luò)內(nèi)抓包獲取數(shù)據(jù),并將數(shù)據(jù)存儲到SQL server數(shù)據(jù)庫,實現(xiàn)信息存儲和管理功能。
1.1.2 監(jiān)測傳感器及儀器
無線傳感器測點上搭載的溫、濕度傳感器(AM2302,奧松電子,廣州),紅外CO2傳感器(SRH-1,四方光電,武漢),電化學(xué)NH3傳感器(4NE-NH3-100,楚環(huán),東莞)均為數(shù)字式傳感器。電化學(xué)傳感器放置于商業(yè)豬舍內(nèi)短期監(jiān)測數(shù)據(jù)穩(wěn)定,連續(xù)監(jiān)測超過3個月衰減嚴(yán)重。由于本監(jiān)測為短期監(jiān)測,在監(jiān)測前進行預(yù)監(jiān)測試驗,連續(xù)測量72 h監(jiān)測數(shù)據(jù)準(zhǔn)確。
監(jiān)測期間用于輔助測量和對比的儀器還包括:溫濕度測量儀,CO2測量儀BM-80-CO2和NH3測量儀AP-S-NH3-J,雙口壓差計SDMN5。各傳感器及手持式測量儀器參數(shù)如表1所示。監(jiān)測前,所有傳感器及儀器均返廠重新標(biāo)定,保證測量數(shù)據(jù)的準(zhǔn)確性。
表1 傳感器和測量儀器參數(shù)
從2017年5月11日到21日對福建光華百斯特生態(tài)農(nóng)牧發(fā)展有限公司下屬的現(xiàn)代化樓房豬舍進行監(jiān)測。為了盡量不影響豬舍的正常生產(chǎn),并分析不同樓層機械通風(fēng)系統(tǒng)內(nèi)部環(huán)境的規(guī)律,數(shù)據(jù)監(jiān)測選擇在基本滿載運行且豬只的品種較為統(tǒng)一的二棟1層(底層)、四棟5層(中間層)、一棟7層(頂層)豬舍分別進行24 h監(jiān)測,樓房位置平面圖如圖2所示。3間豬舍的飼養(yǎng)面積相同,長90 m×寬15 m,頂高3.5 m,中間無隔斷,單一走廊寬1 m,刮糞池深0.8 m,半漏縫地板占總豬圈面積的2/3,地板、吊頂和墻壁均為水泥表面。
圖2 樓房豬舍位置平面圖
二棟1層有生長豬955頭(40±3.6 kg);四棟5層有保育豬1960頭(10.8±1.9 kg);一棟7層有生長豬940頭(51±4.4 kg),品種均為長白豬和大白豬。自動料線喂料時間為每天上午。8:00-10:00,下午14:00-16:00。采用人工清糞和刮糞機相結(jié)合,刮糞板自動清理時間為每天16:00-17:00,人工打掃豬欄時間為每天07:00-9:00和15:00-16:00。
測量前期使用氦氣球搭載無線傳感器測點對每棟樓外部環(huán)境進行了預(yù)測量,發(fā)現(xiàn)4棟樓外部環(huán)境差異很小。表2所示為3層豬舍監(jiān)測期間的外部天氣情況。因測量時間為第1天09:00到第2天09:00,因此取第1天白天外部天氣的最大值和第1天夜間至第2天白天外部天氣的最小值為監(jiān)測期間外部溫度范圍,1層外部氣溫為17.8~30.5 ℃,5層外部氣溫為17.3~31.5 ℃,7層外部氣溫為17.6~29 ℃。3層豬舍在試驗期間外部氣溫范圍近似。
表2 舍外天氣
注: 依據(jù)福建省尤溪縣氣象局統(tǒng)計結(jié)果。
Note: According to statistical results from the weather bureau of Youxi County , Fujian Province.
3層豬舍均采用負壓縱向通風(fēng)模式。由圖3可知,1層、5層豬舍通風(fēng)設(shè)計完全相同,每側(cè)墻開窗4扇,共8扇,每扇尺寸為長0.8 m,寬0.3 m;每側(cè)墻各有4臺30英寸風(fēng)機(Munters EM30,蒙特,北京);兩側(cè)端墻共裝有9臺50英寸風(fēng)機(Munters EM50);兩側(cè)墻各裝有長30 m,寬2.3 m濕簾。其中,5層樓房豬舍的濕簾用塑料紙密封沒有使用。7層通風(fēng)系統(tǒng)同為縱向通風(fēng),安裝方法稍有不同。兩側(cè)墻對稱安裝有4臺風(fēng)機50英寸(Munters EM50)和12臺30英寸風(fēng)機(Munters EM30);一側(cè)端墻裝有5臺50英寸風(fēng)機(Munters EM50);另一側(cè)端墻裝有長15 m,寬2.3 m濕簾,側(cè)墻開窗在監(jiān)測期間全部關(guān)閉。7層和1層、5層的通風(fēng)系統(tǒng)稍有不同,7層內(nèi)氣流縱向穿過整個豬舍,1層和5層氣流從樓層中部進入,兩端墻排出,與1層、5層對比,7層多4臺30英寸風(fēng)機。理論上氣流在1層、5層中移動距離為7層的一半,環(huán)境分布應(yīng)較7層均勻,但是實際環(huán)境均勻性還與通風(fēng)率大小相關(guān)。監(jiān)測期間,根據(jù)工作人員經(jīng)驗結(jié)合舍內(nèi)環(huán)境溫度判斷控制舍內(nèi)機械設(shè)備的運行,并未同時全部開啟所有設(shè)備。
每個豬舍的測量時間均為從第1天的上午9:00至第2天的上午09:00。1層、5層、7層豬舍測量時間分別為2017年5月13-14日,17-18日和19-20日。由于育肥豬體高通常小于1 m,所有無線測點的安裝高度距離地面1.2 m,盡量接近豬生活區(qū)同時防止豬咬壞。由于1層、5層豬舍走廊在樓層中間,通風(fēng)系統(tǒng)基本對稱,采用不對稱放置無線傳感器測點于走廊兩側(cè)的豬生活區(qū)中,盡可能多地獲取縱向不同位置的環(huán)境參數(shù)。7層豬舍走廊緊靠側(cè)墻,因此傳感器測點均勻放置于縱向豬生活區(qū)中,并保證傳感器網(wǎng)絡(luò)測點距離端墻的最小距離相同。每個無線測點每5 min自動測量一組溫、濕度、CO2和NH3數(shù)據(jù)并發(fā)送,每組測量連續(xù)讀取傳感器數(shù)據(jù)6次取平均值。舍內(nèi)外壓差每小時人工測量1次。各層豬舍通風(fēng)設(shè)備及無線測點的部署位置如圖3所示。
圖3 3個樓層傳感器測點布置平面示意圖
計算每樓層所需通風(fēng)率,對采集到的數(shù)據(jù)進行統(tǒng)計學(xué)分析和THI計算,分為4個步驟。
1)計算每樓層所需通風(fēng)率。根據(jù)美國豬舍建筑及設(shè)備手冊(MWPS-8),前保育豬(5.4~13.6 kg)夏季所需通風(fēng)率為每頭117.99×10-4m3/s,生長豬(34.0~68.0 kg)夏季所需通風(fēng)率為每頭353.96×10-4m3/s。各樓層所需通風(fēng)率計算方法為單頭豬所需通風(fēng)率×樓層豬頭數(shù)。1層豬舍所需通風(fēng)率為353.96×10-4m3/s×955 =33.80 m3/s,5層豬舍所需通風(fēng)率為117.99×10-4m3/s×1 960 =23.13 m3/s,7層豬舍所需通風(fēng)率為353.96×10-4m3/s×940 = 33.27 m3/s。
2)計算每樓層環(huán)境參數(shù)包括平均值(±標(biāo)準(zhǔn)差)、最小值、最大值、最大差值和同期最大差值在內(nèi)的統(tǒng)計學(xué)參數(shù)。每5 min采樣1次,取所有測點的所有該參數(shù)采樣值的平均值為該參數(shù)的平均值。對每個測點的每個環(huán)境參數(shù)測量數(shù)據(jù)取15 min平均值,取所有測點同一環(huán)境參數(shù)全天中15 min均值的最大值為該參數(shù)最大值,取15 min均值中的最小值為最小值,取該參數(shù)最大值和最小值的差值為最大差值。以15 min平均值為基準(zhǔn),每15 min計算7個測點同一參數(shù)的最大值和最小值之差作為同期差值,全天24 h內(nèi)同期差值的最大值即為同期最大差值,同期最大差值反映了同一時刻環(huán)境分布的不均勻性。
3)進行差異性分析。使用SPSS軟件(SPSS 22.0,IBM,美國)逐次檢驗任意2樓層同一參數(shù)均值組間水平的差異性是否顯著。檢驗不同樓層溫度、濕度、CO2、NH3濃度的數(shù)組間的方差齊性,當(dāng)數(shù)組間方差齊時,使用LSD法;當(dāng)數(shù)組間方差不齊時,使用Tamhane’s T2法。檢驗同一樓層的7個部署測點的溫度、濕度、CO2、NH3濃度的數(shù)組間的差異性分析。
4)THI計算。取溫、濕度15min平均值計算環(huán)境中THI,評判豬舍環(huán)境的舒適性。采用文獻[41]中THI計算公式,見式(1)。結(jié)合汪開英[42-43]研究得到的THI標(biāo)準(zhǔn),THI<28.06為舒適區(qū);THI>28.06,豬只可能會出現(xiàn)熱應(yīng)激反應(yīng);THI>28.94時為過熱區(qū),豬只出現(xiàn)明顯的熱應(yīng)激反應(yīng)。
式中、分別為舍內(nèi)空氣的干球溫度(℃)和濕球溫度(℃),濕球溫度可由環(huán)境溫度和相對濕度通過焓濕圖求得,公式在相對濕度大于30%時成立。本監(jiān)測中豬舍所在地區(qū)平均海平面高度190 m,大氣壓取為98.7 kPa。
從動物頭數(shù)來看,5層保育豬的頭數(shù)(1960頭)遠大于1層(955頭)和7層(940頭)生長豬頭數(shù),但所需通風(fēng)率5層(23.13 m3/s)小于1層(33.80 m3/s)和7層(33.27 m3/s)。由于所需通風(fēng)率與動物的代謝發(fā)熱量,水蒸氣排放量,CO2排出量綜合相關(guān)[44],實際在3個樓層環(huán)境對比時,不以動物的頭數(shù)和質(zhì)量作為對比的依據(jù),而以實際通風(fēng)水平是否達到該層動物熱、濕、CO2排放所需的通風(fēng)率為依據(jù),將各樓層的通風(fēng)情況統(tǒng)一劃分為欠通風(fēng)、合適通風(fēng)和過通風(fēng)3種通風(fēng)水平。對比在不同通風(fēng)水平下各樓層內(nèi)的環(huán)境參數(shù)。
參考美國豬舍建筑及設(shè)備手冊(MWPS-8),依據(jù)豬舍內(nèi)風(fēng)機開啟情況,實際進氣口面積和舍內(nèi)外靜壓差對監(jiān)測期間每樓層的實際通風(fēng)率進行計算,各樓層通風(fēng)情況如表3所示。
表3 3個樓層的通風(fēng)情況
注: A風(fēng)機,Munters EM30,30英寸風(fēng)機,根據(jù)風(fēng)機的損耗和維護情況,通常將風(fēng)機的效率設(shè)定為70%,下同,靜壓差為0時,通風(fēng)率為3.75 m3·s-1×70%= 2.625 m3·s-1;為25 Pa時,通風(fēng)率為3.17 m3·s-1×70%=2.219 m3·s-1;B風(fēng)機,Munters EM50,50英寸風(fēng)機,靜壓差為0 時,通風(fēng)率為11.70 m3·s-1×70%=8.19 m3·s-1;25 Pa通風(fēng)率為10.57 m3·s-1×70%=7.399 m3·s-1;總進風(fēng)口面積=開窗面積+濕簾面積。
Note: Fan A, Munters EM30, 30 inch fan, according to service life and maintenance of fan, normally the efficiency of fans is set to 70%, the same as below, ventilation rate under a static pressure difference of 0 is 3.75 m3·s-1×70%=2.625 m3·s-1; the ventilation rate under 25 Pa is 3.17 m3·s-1×70%=2.219 m3·s-1; Fan B, Munters EM50, 50 inch fan, ventilation rate under a static pressure difference of 0 is 11.70 m3·s-1×70%=8.19 m3·s-1; ventilation rate under 25 Pa 10.57 m3·s-1×70%=7.399 m3·s-1; total inlet area =open window areas + evaporative pad areas.
圖4為監(jiān)測24 h期間3個樓層的實際運行通風(fēng)率與所需通風(fēng)率對比,二棟1層白天過通風(fēng),夜間欠通風(fēng);總體上四棟5層連續(xù)24 h欠通風(fēng),夜間21:00-06:00欠通風(fēng)嚴(yán)重;一棟7層白天過通風(fēng),夜間合適通風(fēng)。1層、5層的通風(fēng)系統(tǒng)相同,操作運行方式不同,通風(fēng)率差異較大。在監(jiān)測期間外部溫度范圍相似,7層的整體通風(fēng)運行情況優(yōu)于1層、5層,其中的通風(fēng)運行情況最差。
圖4 各時段3個樓層的實際通風(fēng)率
3個樓層豬舍的環(huán)境參數(shù)的統(tǒng)計學(xué)分析指標(biāo)如表4所示。5層溫度最小值、平均值均高于其他樓層,尤其是夜間的最低溫度高于其他樓層1.7 ℃以上。5層豬舍由于欠通風(fēng)致使舍內(nèi)熱量較難排出,對舍內(nèi)溫度影響較大。7層的通風(fēng)情況優(yōu)于其他樓層,舍內(nèi)同期最大差值最小為2.1 ℃,溫度均勻性較好,但受白天層頂輻射影響,在外部最高溫度(29 ℃)略小于其他樓層(30.5和31.5 ℃)的情況下白天溫度最大值為3層中最高(34.5 ℃)比1層高出2.8 ℃,舍內(nèi)溫度最大差值高達11.6 ℃,晝夜溫差大。1層白天溫度最大值較其他樓層低2 ℃以上,舍內(nèi)7個測點的最大差值最低,晝夜溫差小,與1層直接和樓底地面接觸,地面熱阻大的特性相符。該層舍內(nèi)同期最大差值最高,表明溫度均勻性差。從濕度數(shù)據(jù)來看,1層的相對濕度最大值(85.7%)、最小值(40.3%)、平均值(56.6%)均高于其他樓層,可能受樓底濕度影響較大。
表4 3個樓層綜合環(huán)境因子測量數(shù)據(jù)
注: 同列中指標(biāo)不同字母表示差異顯著(<0.05),標(biāo)有相同字母表示差異不顯著(>0.05)。
Note: Different letters at the same column of each index indicate significant differences (<0.05), same letters indicate no significant difference (>0.05).
豬舍內(nèi)CO2濃度主要產(chǎn)生于動物的呼吸和糞便的分解,靠通風(fēng)系統(tǒng)排出,各樓層內(nèi)的CO2濃度遠低于健康限值(3 024.3mg/m3)及最高濃度限值(9 819.3 mg/m3)。根據(jù)文獻[45],保育豬的CO2排放量為每頭0.86 kg /d,生長豬CO2排放量為每頭2.67 kg /d。估算每樓層CO2總排出量約為1層(2.67 kg/d×955=2 549.9 kg/d)>7層(2.67 kg/d×940=2 509.8 kg/d)>5層(0.86 kg/d×1 960= 1 685.6 kg/d)。受欠通風(fēng)影響,5層在總排出量最低的情況下,CO2濃度平均值、最大值、最大差值、同期最大差值均高于其他樓層,CO2分布不均勻,且較難排出。
豬舍內(nèi)NH3濃度主要來源于尿液中的尿素快速水解[24],受樓層豬舍排尿系統(tǒng)布置及通風(fēng)情況影響較大。各樓層使用尿管排尿,其中2-7層各尿管匯總后從2層排出,每層尿管在舍內(nèi)匯集處敞開,導(dǎo)致多層尿液中散發(fā)出的NH3經(jīng)尿管開口處擴散至2-7層豬舍內(nèi),因此5層和7層NH3濃度較高,而1層為單獨排尿管,尿液通過封閉尿管流出舍外,NH3濃度較低。監(jiān)測期間各樓層豬舍普遍NH3濃度不高,基本低于健康限值(8.4mg/m3),遠低于最高濃度限值(19.0mg/m3)。受欠通風(fēng)影響,5層NH3濃度最大值、最大差值、同期最大差值均高于其他樓層,NH3分布不均勻。7層的NH3濃度平均值略高于5層,但最大值、最大差值、同期最大差值均低于5層,均勻性較5層優(yōu),與通風(fēng)水平相符。由于1層尿液單獨排出不受其他樓層尿液影響,故NH3濃度最小。
對不同樓層之間的全天環(huán)境參數(shù)平均值進行差異性分析,結(jié)果如表4所示。不同樓層的均值除了1層與7層CO2濃度差異性不顯著(>0.05),其他不同樓層間均值差異性顯著(<0.05)。表5為每樓層各測點位置全天的環(huán)境參數(shù)均值及測點間參數(shù)差異性分析。同樓層相鄰位置測點出現(xiàn)某些參數(shù)差異性顯著,某些參數(shù)差異性不顯著,各測點位置間環(huán)境參數(shù)異差性情況各異,如1層中1#與2#的溫、濕度差異性不顯著(>0.05),但是CO2和NH3濃度差異性顯著(<0.05)。結(jié)果顯示溫、濕度場,CO2和NH3濃度場由于產(chǎn)生源頭和變化的誘因各不相同引起在同樓層豬舍內(nèi)測點間差異性及分布情況各異。其中同層中溫、濕度分布場受通風(fēng)率,氣流方向,豬散熱及呼吸,外部環(huán)境等影響較大。而CO2濃度場受動物呼吸排出量,通風(fēng)率,氣流方向影響較大,NH3濃度場受糞尿排放方式,溫度,通風(fēng)率,氣流方向等影響[45]。
表5 3個樓層7個測點的環(huán)境因子的均值差異性分析
注: 同一行標(biāo)有不同字母表示差異顯著(<0.05),標(biāo)有相同字母表示差異不顯著(>0.05),下同。
Note: Different letters marked at the same row indicate significant differences (<0.05), same letters indicate no significant difference (>0.05), the same as below.
用每15 min溫濕度均值計算每測點位置在監(jiān)測期間的THI,如圖5所示,THI在28.94之上為過熱區(qū),在28.06以下為舒適區(qū)。5層通風(fēng)運行情況最差,1#和2#測點(靠近一側(cè)端墻風(fēng)機區(qū)域)從第1天11:00至第2天09:00時間段內(nèi),連續(xù)12 h以上THI>28.06。幾乎全部測點在15:00-20:00時間段THI>28.06,平均值27.9±0.8接近舒適區(qū)上限。通過2.1小節(jié)中的分析得知7層通風(fēng)運行最優(yōu),該層下午時段12:00-18:00間大部分測點位置處于THI>28.06,13:00-16:00時段2#、5#、7#測點(豬舍中部大部分位置)THI>28.94。1層只有在15:00-18:00時間段內(nèi)1#和2#測點THI值(靠近一側(cè)端墻風(fēng)機區(qū)域)超出適宜范圍,其余測點THI值均在適宜范圍內(nèi)。
圖5 3個樓層的THI指標(biāo)
表6中為3個樓層的THI指標(biāo)分析。5層的THI指標(biāo)最差,平均值接近舒適區(qū)上限。1層不同測點測得THI最大差值最高為7.1,但由于1層的5個測點測得的THI均未超過熱應(yīng)激區(qū)域指標(biāo),平均值較低為24.9,環(huán)境舒適性仍然較5層和7層優(yōu)?,F(xiàn)場豬舍工作人員證實1層豬舍為3層豬舍中豬死亡率最低。
表6 3個樓層的THI指標(biāo)分析
3個樓層的不同測點間的THI差異性分析如表7所示。
表7 每樓層不同測點THI指標(biāo)差異性分析
同一樓層多個不同部署測點間的THI均值差異性顯著,如1層的1#與3#-7#的THI均值差異性顯著(<0.05),5層的1#與2#-4#的THI均值差異性顯著(<0.05),7層的1#與2#-3#的THI均值差異性顯著(<0.05)。各樓層環(huán)境舒適性分布不均且無規(guī)律。
根據(jù)以上分析,通風(fēng)水平是影響豬舍內(nèi)部環(huán)境的主要因素,其次為樓層差異。豬舍夏季通風(fēng)時必需保持實際通風(fēng)率不小于設(shè)計通風(fēng)率。樓層豬舍的頂層受太陽輻射影響較大,需要增加頂層屋頂?shù)谋睾头垒椛浯胧?。底層受地面保溫性的影響,在高溫天氣下舍?nèi)溫度不高;但地底濕氣導(dǎo)致舍內(nèi)濕度大,可采用加大通風(fēng)率的方法排出空氣中多余水分。
本文采用無線傳感網(wǎng)絡(luò),部署7個無線測點分別對樓房豬舍的頂層、中間層和底層的熱環(huán)境和有害氣體分別進行連續(xù)24 h監(jiān)測,對數(shù)據(jù)進行分析并計算溫濕度指標(biāo)(THI),結(jié)論如下:
1)對比每樓層實際通風(fēng)率與所需通風(fēng)率(每樓層實際豬頭數(shù)í夏季每頭豬所需通風(fēng)率),將通風(fēng)情況劃分為欠通風(fēng)、合適通風(fēng)和過通風(fēng)3種水平。5層(中間層)欠通風(fēng)嚴(yán)重, THI指標(biāo)整體偏高,平均值(27.9±0.8)接近舒適區(qū)上限。7層(頂層)通風(fēng)最優(yōu)但受輻射影響,白天溫度最大值比底層高2.8 ℃,晝夜最大溫差達11.6 ℃。1層(底層)通風(fēng)較7層差,較5層優(yōu),但保溫性好濕氣大,溫度整體較低,晝夜溫差較小,相對濕度高達85.7%,由于溫度較低THI均值為24.9,環(huán)境為3層中最佳。影響THI指標(biāo)的2個主要因素分別為通風(fēng)水平和樓層差異。
2)夏季通風(fēng)條件下,各樓層內(nèi)的CO2和NH3濃度遠低于最高濃度限值。5層在3個樓層中估算CO2總排出量最低(1 685.6 kg/d),但其受欠通風(fēng)影響舍內(nèi)CO2濃度均值最高且濃度分布不均。由于各樓層使用尿管排尿,尿液基本不在舍內(nèi)停留,各樓層豬舍NH3濃度普遍不高。1層豬舍尿液通過封閉尿管排出舍外,尿管在舍內(nèi)沒有開口,NH3濃度最低??傮w來說,CO2受通風(fēng)水平影響大,NH3濃度則受通風(fēng)和尿排出方式兩者影響較大。
3)從環(huán)境分布來看,不同樓層間溫?zé)岷陀泻怏w環(huán)境存在差異,不同樓層的均值除了1層與7層CO2濃度差異性不顯著(>0.05),其他不同樓層間均值差異性顯著(<0.05)。同一層豬舍不同測點位置環(huán)境也存在差異,如1層中1#與2#的CO2和NH3濃度差異性顯著(<0.05)。
本文通過對集約化樓房豬舍環(huán)境的溫濕度、CO2、NH3的監(jiān)測結(jié)果分析,深入了解樓房豬舍養(yǎng)殖生產(chǎn)過程中存在的環(huán)境控制問題,幫助找出樓房養(yǎng)豬機械通風(fēng)設(shè)計及操作運行情況存在的不足,為提高樓房養(yǎng)豬環(huán)境控制水平提供理論依據(jù)。
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Monitoring and analysis of thermal environment and harmful gases in mechanically ventilated multistory pig buildings
Gao Yun1,2, Diao Yaping1, Lin Changguang3, Liu Yaxuan3, Guo Changming3, Lei Minggang2,4,Tong Yu1,2, Li Xuan1,2
(1430070; 2430070,; 3365106,; 4430070,)
With the intensive introduction of policies and acts for environmental protection, the farming land shortage situations for domesticated animals are increasingly serious. Innovational multistory pig buildings are introduced to save land resources and thus increase breeding intensities. The following awareness and concerns towards air qualities of animal occupant zones on each floor are being raised among pig producers. In this paper, a wireless sensor network for collecting environmental factors was used to monitor the thermal environments and harmful gases of three representative floors in multistory pig buildings, which were the top floor (7thfloor), the middle floor (5thfloor) and the ground floor (1stfloor). According to the heads of animals and their weights on these representative floors, the ventilation situations were determined to be the less-ventilated, the well-ventilated and the over-ventilated levels by comparing the actual ventilation rates with the floor’s desired ventilation rates. Therefore, the differences of indoor environments between various floors and between multi-locations on the same floor were analyzed with respect to each floor’s ventilation levels, which eventually revealed the practices of indoor environment in multistory pig buildings. The monitoring was conductedfrom the 11thto 21stMay 2017 inFujian province, located in southern China. Seven wireless sensor nodes were deployed on the top, ground and middle floors respectively. Each floor was monitored over 24 hours, from 9 am of the first day to the same 9 am of the next day. The results were summarized as follows: 1) Ventilation levels had a crucial impact on thermal environments.The less-ventilated levels of the 5th floor made the temperature-humidity indexes (THIs) higher than those of other floors, with an average value of 27.9 ± 0.8 close to the upper limit of comfort zone, 28.06. The radiation effects on the top floor increased the maximum temperature value of this floor to 34.5 ℃, 2.8 ℃ higher than that of the ground floor, with a highest day-night temperature difference up to 11.6 ℃. The temperature of the ground floor was kept in a comfortable range with a smaller day-night temperature difference due to the better thermal insulation of its floor, whereas the relative humidity was increased to a maximum of 85.7% by the moisture from the underlying surface, which was integrated to an average THI of 24.9. 2) The overall concentrations of CO2and NH3on each floor, under the summer ventilation conditions, were far less from the upper concentration limits. The maximum value, average value, maximum difference, and the same time maximum difference of the CO2concentrations on the 5thfloor were higher than those of other floors, contrasting with the lowest approximated CO2emission of 1685.6 kg/d among those of three floors, which was due to its less-ventilated levels in 24 hours. The constitution of the buildings’ urinary collecting duct system influenced the NH3concentrations dominantly, the lowest concentrations of NH3on the ground floor benefited from the isolation of its urinary ducts from other floor’s system. 3) The difference analyses between average environmental factors of various floors and between the environmental factors of different locations on the same floor were conducted. Highly significant differences (<0.05) were found in most environmental factors of different floors except there was no significant difference of CO2concentrations between the 1stfloor and the 7thfloor. The significant differences (<0.05) were found in some environmental factors between different locations on each floor, while no significant differences (> 0.05) existed among other factors. Mechanically ventilated multistory pig buildings are innovative in China at present. To gain a deep understanding of animal occupant zone environments in multistory pig buildings, and further help to find design flaws of mechanical ventilation systems and disadvantages of operation strategies, the monitoring and analysis of thermal environments and harmful gases have been carried out in the multistory pig buildings during pig production, which would build up the theoretical basis and principles to improve environmental control levels of multistory pig buildings.
temperature; humidity; ventilation; multistory pig building; thermal environment; toxic gases; THI; difference analysis
2017-10-09
2018-01-16
“十三五”國家重點研發(fā)計劃項目(2016YFD0500506);現(xiàn)代農(nóng)業(yè)技術(shù)體系(CARS-35);福建省科技重大專項(2012NZ0003-3);中央高校自主創(chuàng)新基金(2662017PY086)
高云,女,湖北武漢人,副教授,博士,主要從事農(nóng)業(yè)智能檢測與控制方面的研究。Email:angelclouder@mail.hzau.edu.cn。中國農(nóng)業(yè)工程學(xué)會會員:高云(E041700006M)
10.11975/j.issn.1002-6819.2018.04.029
TP391
A
1002-6819(2018)-04-0239-09
高 云,刁亞萍,林長光,劉亞軒,郭長明,雷明剛,童 宇,黎 煊. 機械通風(fēng)樓房豬舍熱環(huán)境及有害氣體監(jiān)測與分析[J]. 農(nóng)業(yè)工程學(xué)報,2018,34(4):239-247.doi:10.11975/j.issn.1002-6819.2018.04.029 http://www.tcsae.org
Gao Yun, Diao Yaping, Lin Changguang, Liu Yaxuan, Guo Changming, Lei Minggang, Tong Yu, Li Xuan. Monitoring and analysis of thermal environment and harmful gases in mechanically ventilated multistory pig buildings[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(4): 239-247. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2018.04.029 http://www.tcsae.org