干燥速率速率曲线的测定实验

干燥速率速率曲线的测定实验 实 验 名 称: 干燥速率曲线测定实验 学 院: 化学学院 专 业: 化学工程与工艺 班 级: 化工 班 姓 名: 学 号: 序号: 同组者姓名: 指 导 教 师: 日 期: intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 一、实验目的 1(熟悉常压洞道式(厢式)干燥器的构造和操作; 2(测定在恒定干燥条件(即热空气温度、湿度、流速不变，物料与气流的接触方式不变)下的湿物料干燥曲线和干燥速率曲线; 3(测定该物料的临界湿含量X; 0 4(掌握有关测量和控制仪器的使用方法。 二、基本原理 当湿物料与干燥介质相接触时，物料面的水分开始气化，并向周围介质传递。根据干燥过程中不同期间的特点，干燥过程可分为两个阶段。 第一个阶段为恒速干燥阶段。在过程开始时，由于整个物料的湿含量较大，其内部的水分能迅速地达到物料表面。因此，干燥速率为物料表面上水分的气化速率所控制，故此阶段亦称为表面气化控制阶段。在此阶段，干燥介质传给物料的热量全部用于水分的气化，物料表面的温度维持恒定(等于热空气湿球温度)，物料表面处的水蒸汽分压也维持恒定，故干燥速率恒定不变。 第二个阶段为降速干燥阶段，当物料被干燥达到临界湿含量后，便进入降速干燥阶段。此时，物料中所含水分较少，水分自物料内部向表面传递的速率低于物料表面水分的气化速率，干燥速率为水分在物料内部的传递速率所控制。故此阶段亦称为内部迁移控制阶段。随着物料湿含量逐渐减少，物料内部水分的迁移速率也逐渐减小，故干燥速率不断下降。 恒速段的干燥速率和临界含水量的影响因素主要有:固体物料的种类和性质;固体物料层的厚度或颗粒大小;空气的温度、湿度和流速;空气与固体物料间的相对运动方式。 恒速段的干燥速率和临界含水量是干燥过程研究和干燥器的重要数据。本实验在恒定干燥条件下对毛毡物料进行干燥，测定干燥曲线和干燥速率曲线，目的是掌握恒速段干燥速率和临界含水量的测定方法及其影响因素。 ?干燥速率的测定 dW',W'U,, (7-1) Sd,S,, 2式中:—干燥速率，kg /(m?h); U 2 —干燥面积，m，(实验室现场提供); S intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision —时间间隔，h; ,, —时间间隔内干燥气化的水分量，kg。 ,W',, ? 物料干基含水量 G',Gc' (7-2) X,Gc'式中:—物料干基含水量，kg水/ kg绝干物料; X —固体湿物料的量，kg; G' —绝干物料量，kg。 Gc' ? 恒速干燥阶段，物料表面与空气之间对流传热系数的测定 (t,t),dQ'dW'w Uc,,, (7-3) SdrSdr,,twtw Uc,rtw (7-4) ,,t,tw 2式中:—恒速干燥阶段物料表面与空气之间的对流传热系数，W/(m??); , 2—恒速干燥阶段的干燥速率，kg/(m?s); Uc —干燥器内空气的湿球温度，?; tw —干燥器内空气的干球温度，?; t —t?下水的气化热，J/ kg。 rtww ? 干燥器内空气实际体积流量的计算 由节流式流量计的流量公式和理想气体的状态方程式可推导出: 273，t V,V， (7-5) tt0273，t0 3V式中:—干燥器内空气实际流量，m/ s; t t —流量计处空气的温度，?; 0 3V—常压下t?时空气的流量，m/ s; 0t0 t—干燥器内空气的温度，?。 2，,P (7-6) V,C，A，t000, ,2,Ad (7-7) 004 式中:C—流量计流量系数，C=0.67 00 intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 2 A—节流孔开孔面积，m; 0 d—节流孔开孔直径， d=0.050 m; 00 ΔP—节流孔上下游两侧压力差，Pa; 3 ρ—孔板流量计处时空气的密度，kg/m。 t0 三、实验装置 1(装置 空气用风机送入电加热器，经加热的空气流入干燥室，加热干燥室中的湿毛毡后，经排出管道排入大气中。随着干燥过程的进行，物料失去的水分量由称重传感器和智能数显仪表记录下来。实验装置如图1所示。 图1 干燥装置图 1-风机 2-可移动实验框架 3-旁路阀 4-气路管道 5-差压传感器 6-不锈钢孔板流量计 7-电加热管 8-风量均布器 9-支杆 10、11-湿球、干球温度传感器 12-可视门 13-精密 称重传感器 14-蝶阀3 15-蝶阀2 16-蝶阀1 17-总电源空气开关 18-仪表电源开关 19-变频器电源开关 20-风机电源切换开关 21-电加热管停止按钮 22-干球温度手自 动切换开关及手动调节旋钮 23-干球温度自动调节仪 24-指示灯 25-电加热管启动按钮 26-加热管电压指示 27-智能风量控制仪 28-智能多路液晶显示仪 29-变频器 (1)风机电源切换开关:有三个位:直接、停止、变频分别为风机电源由电网直接 提供、风机停止和风机电源由变频器提供。 (2)智能多路液晶显示仪的1~3通道分别为:空气流量、湿球温度、称重重量。 (3)风机电源切换开关:为3位开关，当开关打到左边位置时为直接电源给风机供intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 电;当开关打到中间位置时为停止位置;当开关打到右边位置时为变频器输出电源给 风机供电。相应上面的指示灯指示的是直接风机供电时的风机电源指示。 (4)风量控制:可通过仪表实现自动控制及调节旋钮实现手动风量控制，但风量不 3得低于50m/h，否则会因为风量过小而使烧坏加热管。控制方法是:1)手动控制时， 将风量手自动切换开关打到手动位置，通过调节手动旋钮即可对变频器输出控制，从 而控制风机风量;2)自动控制时，将手自动切换开关打到自动位置，这时可通过仪表 对变频器输出控制，从而也实现了对风机风量的控制。 2(主要设备及仪器 (1) 鼓风机:MY250W，250W (2) 电加热器:4.5KW (3) 干燥室:180mm×180mm×1250mm (4) 干燥物料:湿毛毡 (5) 称重传感器:YZ108A型，0,300g。 四、实验步骤与注意事项 1、实验步骤 1)(打开仪表控制柜上的仪表电源开关，开启仪表。 2)(打开仪表控制柜上的风机电源开关，开启风机，这时加热管停止按钮灯亮。 3)(按下加热管启动按钮，启动加热管电源，刚开始加热时，打开加热管电源开关，可通过仪表实现自动控制及调节旋钮实现手动控制干球温度。其方法是:(1)手动控制时，将手自动切换开关打到手动位置，通过调节手动旋钮即可对加热管电压实现控制，从而控制干球温度;(2)自动控制时，将手自动切换开关打到自动位置，这时可通过仪表对加热管的电压进行控制，从而也实现了对干球温度的控制。干燥室温度(干球温度)要求恒定在70?。 4)(将毛毡加入一定量的水并使其润湿均匀，注意水量不能过多或过少。 5)(当干燥室温度恒定在70?时， 一定在老师的指导下或由老师将湿毛毡十分小心地 悬挂于称重传感器下的托盘上。放置毛毡时应特别注意不能用力下拉，因称重传感器是 非常精密的仪器，且其测量上限仅为300克，稍微的力均会完全损坏称重传感器导致不 能再使用。 6)(记录时间、毛毡和剩余水的重量(即为重量显示仪的读数)，每分钟记录一次数据;每两分钟记录一次干球温度和湿球温度。 intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 7)(待毛毡恒重时，即为实验终了时，按下停止按钮，停止加热，注意保护称重传感器，一定在老师的指导下或由老师非常小心地取下毛毡。 8)(等20分钟后，当干球温度降到30度左右时关闭风机电源、关闭仪表电源，清理实验设备。 2、注意事项 1)(必须先开风机，后开加热器，否则加热管可能会被烧坏。 2)(特别注意传感器是非常精密的仪器，且其负荷量仅为300克，放取毛毡时必须十分小心，绝对不能下拉或用力上提，否则会完全损坏称重传感器导致不能再使用。 33)(风量不得低于50m/h，否则会因为风量过小而烧坏加热管。 五. 原始实验数据(附页) intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 六(数据处理 本实验中:托盘质量m=28.6g 1 毛毡绝干质量Gc’=12.70g 2毛毡干燥面积S=287.84 m 以时间t=2min时为例计算: 固体湿物料的量G’=(82.0-28.6)g=53.4g=0.0534kg 物料干基含水量X=(G- Gc’)/ Gc’=(0.0534-0.0127)/0.0127=3.205kg ΔW’=0.0545-0.0534=0.0011kg -42干燥速率U=ΔW’/(S*Δt)=0.0011/(287.84*10*1/60)=2.293 kg /(m?h) 以此方法计算得到下表: 时间/min 质量/g 固体湿物料的物料干基含水量时间间隔内干燥干燥速率U/kg /,, 2量G’/kg X/kg 气化的水分量Δ?h) (m W’/ kg 1 83.1 0.0545 3.291 0 0 2 82.0 0.0534 3.205 0.0011 2.293 3 80.8 0.0522 3.110 0.0012 2.502 4 80.7 0.0521 3.102 0.0001 0.208 5 80.1 0.0515 3.055 0.0006 1.251 6 78.7 0.0501 2.945 0.0014 2.918 7 77.9 0.0493 2.882 0.0008 1.668 8 77.4 0.0488 2.843 0.0005 1.042 9 76.3 0.0477 2.756 0.0011 2.293 10 74.7 0.0461 2.630 0.0016 3.335 11 74.3 0.0457 2.598 0.0004 0.834 12 73.7 0.0451 2.551 0.0006 1.251 13 72.3 0.0437 2.441 0.0014 2.918 14 71.5 0.0429 2.378 0.0008 1.668 15 70.8 0.0427 2.362 0.0002 0.417 16 69.9 0.0418 2.291 0.0009 1.876 17 68.6 0.0405 2.189 0.0013 2.710 18 68.1 0.0400 2.150 0.0005 1.042 19 67.8 0.0397 2.126 0.0003 0.625 20 66.3 0.0382 2.008 0.0015 3.127 21 65.1 0.0374 1.945 0.0008 1.668 intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 22 64.5 0.0368 1.898 0.0006 1.251 23 63.7 0.0360 1.835 0.0008 1.668 24 62.4 0.0347 1.732 0.0013 2.710 25 61.8 0.0341 1.685 0.0006 1.251 26 61.4 0.0337 1.654 0.0004 0.834 27 60.0 0.0333 1.622 0.0004 0.834 28 58.5 0.0318 1.504 0.0015 3.127 29 58.3 0.0316 1.488 0.0002 0.417 30 57.5 0.0308 1.425 0.0008 1.668 31 56.1 0.0294 1.315 0.0014 2.918 32 55.3 0.0286 1.252 0.0008 1.668 33 55.1 0.0284 1.236 0.0002 0.417 34 53.6 0.0289 1.276 0.0005 1.042 35 52.4 0.0277 1.181 0.0012 2.502 36 52.2 0.0275 1.165 0.0002 0.417 37 51.5 0.0268 1.110 0.0007 1.459 38 50.0 0.0253 0.992 0.0015 3.127 39 49.5 0.0248 0.953 0.0005 1.042 40 49.6 0.0249 0.961 0.0001 0.208 41 48.0 0.0233 0.835 0.0016 3.335 42 47.3 0.0226 0.780 0.0007 1.459 43 49.0 0.0243 0.913 0.0017 3.544 44 46.7 0.0227 0.787 0.0016 3.335 45 45.7 0.0217 0.709 0.0010 2.085 46 45.6 0.0216 0.701 0.0001 0.208 47 45.5 0.0215 0.693 0.0001 0.208 48 44.5 0.0205 0.614 0.0010 2.085 49 44.0 0.0200 0.575 0.0005 1.042 50 44.2 0.0202 0.591 0.0002 0.417 51 44.0 0.0200 0.575 0.0002 0.417 52 43.2 0.0192 0.511 0.0008 1.668 53 43.3 0.0193 0.520 0.0001 1.503 54 43.2 0.0192 0.512 0.0001 0.208 intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 2.图表制作 ?根据上表以干基含水量X为纵坐标，以t/min为横坐标，可得到如下曲线图可 以作得干燥曲线图: ?根据上表以X为横坐标，以U为纵坐标可作得干燥速率曲线: intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision 由上图可知，物料的临界湿含量X=1.10 0 七、结果分析与讨论 由图可以看出，实验所得结果不是很理想，主要原因可能是实验仪器自动加热装置存在损坏，所以使得实验数据出现一定的误差。 八、思考题解答 1.毛毡含水是什么性质的水分, 答:毛毡含水有自由水和平衡水，其中干燥除去的为自由水。 2.实验过程中干、湿球温度计是否变化,为什么, 答:干球温度是变化的。干球温度是指空气温度，由于空气流量是不稳的，干燥 温度是在70?上下波动的。 湿球温度也是在变化的。由于失水量是在变化的，同时干球温度也是变化的。 3.恒定干燥条件是指什么, 答:在间歇干燥实验中，用大量的热空气干燥少量的湿物料，空气的温度、湿度、 气速及流动方式都恒定不变。 4.如何判断实验已结束, 答:毛毡恒重，即重量显示仪的读数不变。 但实际试验中不可能出现恒定不变 的情况，会有上下的小浮动。 intensive development. (5) have different emphasis: for development, "with development, the emphasis on" way, from space, multiple groups from a single radiation-belt open development. Spatial structure of 2, the prominent cultural city protection elements on the development of the whole city and culture series supporting role, with natural landscapes and green for the background, according to the combined city, urban Group organization structure, set up a decentralized development patterns, building ... Three rivers: the Yangtze, jinsha River and minjiang rivers, cities in three rivers based on development along the Yangtze River, city on the River, River in the city. Multiple groups: the relatively compact area layout, each district consists of multiple groups, and the area has both integrated urban functions, and have their own characteristics and perimeter formation Li Zhuang, Li Zhuangdong characteristic tour area and Hong Kong in group, consists of 17 groups. Band: modern features gathering along the Yangtze River belt. Dvn group in the upper reaches of the jinsha River along the river continues to the East to South stream groups, layout along the city's main commercial, business, administrative, cultural and creative research and development in science and education function of modern service and port equipment manufacturing, liquor, and other features and modern industry. 2.5-2 spatial planning figure 2.6 in Yibin city, Central City urban development vision vision