管道热损失的计算.xls

第二根管道保温材料的热阻 m℃/W Rb2= 0.777第二根从保温层外表面到沟内空气的热阻m℃/W Rw2= 0.065第二根管道从热媒到沟内空气的总热阻 m℃/W ∑R2= 0.849从地沟内空气到室外空气的热阻 m℃/W ∑R0= 0.339地沟内空气温度℃ tgo= 50.7则地沟内管道的总散热损失 W Q= 10841.1当地沟通风时,保证其内的温度为℃ tgo、= 35.0则通风系统的通风排热水量为 W Q、= 10610.1管道热损失计算备注Rn=1/(3.14×αn×dn) (此项热阻相对其它数值很小,可忽略)Rb=ln(dw/dn)/(2×3.14×λg)(此项热阻相对其它数值很小,可忽略)Rb=ln(dz/dw)/(2×3.14×λb)αw=11.6+7×v0.5Rw=1/(3.14×dz×αw)dngo=4×Fngo/Sngo可近似取12 W/m2℃Rngo=1/(3.14×αngo×dngo)dwgo=4×Fwgo/o=ln(dwgo/dngo)/(2×3.14×λgo)当土壤温度10~40℃,中等湿度土壤取1.2~2.5W/m℃可取12~15W/m2℃H=h+λt/αkRt=ln(2×H/dz+[(2×H/dz)2-1]0.5/(2×3.14×λt)主要是阀门、补尝器、支座的损失地沟敷设取0.20ΔQ=(t-tdb)×(1+β)×l/(Rn+Rg+Rb+Rw+Rngo+Rgo+Rt)∑R1=Rn1+Rg1+Rb1+Rw1∑R2=Rn2+Rg2+Rb2+Rw2∑R0=Rngo+Rgo+Rttgo=(t1/∑R1+t2/∑R2++tdb/∑R0)/(1/∑R1+1/∑R2++1/∑R0)Q=(tgo-tdb)/R0按设计规定要求不高于40 ℃Q、=[(t1-tgo、)/∑R1+(t2-tgo、)/∑R2++(tgo、-tdb)/∑R0]×(1+β)×L