课程设计,列管式换热器设计
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设计(论文)题目: 列管式换热器的设计
目 录 1 前 言························································3 2 设计任务及操作条件··············································3
3 列管式换热器的工艺设计·········································3 3.1换热器设计方案的确定··········································3 3.2 物性数据的确定················································4 3.3 平均温差的计算················································4 3.4 传热总系数K的确定············································4 3.5 传热面积A的确定··············································6 3.6 主要工艺尺寸的确定············································6 3.6.1 管子的选用·················································6 3.6.2 管子总数n和管程数Np的确定··································6 3.6.3 校核平均温度差tm及壳程数Ns·································7 3.6.4 传热管排列和分程方法········································7 3.6.5 壳体内径··················································7 3.6.6 折流板····················································7 课程设计 2 3.7 核算换热器传热能力及流体阻力··································7 3.7.1 热量核算···················································7 3.7.2 换热器压降校核·············································9 4 列管式换热器机械设计············································10
4.1 壳体壁厚的计算················································10 4.2 换热器封头选择················································10 4.3 其他部件······················································11 5 课程设计评价·····················································11 5.1 可靠性评价····················································11 5.2 个人感想······················································11 6 参考文献··························································11 附表 换热器主要结构尺寸和计算结果·······························12
1 前 言 换热器(英语翻译:heat exchanger),是将热流体的部分热量传递给冷流体的设备,又称热交换器。换热器是化工、石油、动力、食品及其它许多工业部门的通用设备,在生产中占有重要地位。在化工生产中换热器可作为加热器、冷却器、冷凝器、蒸发器和再沸器等,应用更加广泛。换热器种类很多,但根据冷、热流体热量交换的原理和方式基本上可分三大类即:间壁式、混合式和蓄热式。 列管式换热器工业上使用最广泛的一种换热设备。其优点是单位体积的传热面积、处理能力和操作弹性大,适应能力强,尤其在高温、高压和大型装置中采用更为普遍。 列管式换热器主要有以下几个类型:固定管板式换热器、浮头式换热器、U形管式换热器等。 设计一个比较完善的列管式换热器,除了能满足传热方面的要求外,还应该满足传热效率高、体积小、重量轻、消耗材料少、制造成本低、清洗维护方便和操作安全等要求。 列管式换热器的设计,首先应根据化工生产工艺条件的要求,通过化工工艺计算,确定换热器的传热面积,同时选择管径、管长,确定管数、管程数和壳程数,课程设计 3 然后进行机械设计。 2 设计任务及操作条件 2.1 设计题目:用水冷却甲苯的列管式换热器设计 2.2 设计任务及操作条件 某生产过程中,用循环冷却水冷却柴油。 1、甲苯入口温度: 80 ℃,出口温度: 50 ℃ 2、甲苯流量: 33125 kg/h,压力: 0.4~0.6 MPa 3、循环冷却水压力: 0.4~0.6 MPa,入口温度: 30 ℃,出口温度: 40 ℃ 已知甲苯的有关物性数据:密度ρ1=867kg/m3;定压热比容cp,1=1.85kJ/(kg·℃);热导率λ1=0.126W/(m·℃);黏度μ1=3.75×10-4 Pa·s 3 列管式换热器的工艺设计
3.1 换热器设计方案的确定 甲苯入口温度80℃,出口温度50℃,冷却水入口温度30℃,出口温度40℃。壳体和管束壁温差较大,且考虑到冷却水易结垢,需要清洗,故选用浮头式换热器。冷却水走管程,甲苯走壳程。因逆流时的平均温度差最小,传热推动力大,可节省冷却介质的用量,操作无特殊要求,故流动方式选逆流。选用φ25×2.5的碳钢管,管内流速设为ui=1.5m/s。 3.2 物性数据的确定 定性温度:可取流体进口温度的平均值。 壳程甲苯的定性温度:6525080T℃
管程冷却水的定性温度:3524030T℃ 壳程甲苯65℃物性数据: 密度 ρ1=867kg/m3; 定压热比容 cp,1=1.85kJ/(kg·℃); 热导率 λ1=0.126W/(m·℃); 黏度 μ1=3.75×10-4 Pa·s 管程冷却水35℃时物性数据:查《化工原理》附表可知 密度 ρ2=994.3kg/m3; 定压热比容 cp,2=4.174kJ/(kg·℃); 热导率 λ2=0.62W/(m·℃); 课程设计 4 黏度 μ2=7.43×10-4 Pa·s 3.3 平均温差的计算 1、对于逆流换热过程,其平均温差可按式(3-1)进行计算:
2121lntttttm
(3-1) 式中,Δt1、Δt2分别为大端温差与小端温差。当Δt1/Δt2<2时,可用算术平均值:
221tttm
Δt1=80-40=40℃ Δt2=50-30=20℃ Δt1/Δt2=2
℃△△△△△85.282040ln2040ln2121tttttm
3.4 传热总系数K的确定 用式(3-2)进行K值核算。
(3-2) 式中:-给热系数,W/m2·℃; R-污垢热阻,m2·℃/W; δ-管壁厚度,mm; λ-管壁导热系数,W/m·℃; 下标i、o、m分别表示管内、管外和平均。 A0=4d02=4×252=490.63mm2
Ai=4di2=4×202=314.16mm2
K=1++++100000RddRddd
dmiiii课程设计 5 40.402216.31463.4902AAAoimmm2 查《化工原理》附表可知 Rsi=5.16×10-4 m2·℃/W Rso=1.72×10-4 m2·℃/W λ=50 W/m·℃ 管程Re=μdu=00743.00.3994.512.00=40146.6
管程传热系数i可由公式(3—3)计算 i=Red23.00i0.8)cp(n (3—3)
冷却水被加热,取n=0.4 i=0.0232.002.60×40146.60.8×)(2.6000743.007.140.4=412.6W/(m2·℃)
假设取壳程传热系数为600W/(m2·℃) 用公式(3—4)对K计算
K=1++++100000RddRddd
dmiiii (3—4)
式中:-给热系数,W/m2.℃; R-污垢热阻,m2.℃/W; δ-管壁厚度,mm; λ-管壁导热系数,W/m.℃; 下标i、o、m分别表示管内、管外和平均。
20.006.41225.0020.0025.0000516.00225.005025.00025.00000172.060011K
=179.5W/m2.℃ 3.5 传热面积A的确定 换热器的传热量Q=Whcph(T1-T2)=33125×1.85×(80-50)=1.84×106kJ/h=511kw 68.9885.285.179511000KQAmt△m
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