孔板流量计算公式.pdf

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1、孔板流量计的测定与计算在孔板流量计的前后端测出压差后可按以下两种方法进行计算；（一）、可按公式计算出瓦斯流量。计算公式：Q=Kb(Δh)1/2δ混pδT（1）Q纯=Q混X式中：Q——抽放的瓦斯混合量，m3/min；混Q——抽放的瓦斯纯量，m3/min；纯K——实际孔板流量特性系数，计算见（2）式；b——瓦斯浓度校正系数，计算见（3）式；δp——气压校正系数，计算见（4）式；δT——温度校正系数，计算见（5）式；Δh——在孔板前后端所测之压差，mmH2O；X——混合气体中瓦斯浓度，%。K=189.76a20mD（2）式中：a0——标准孔板流量系数；m=（d21/D）m——截面比；D

2、——管道直径，米；d1——孔板直径，米；b=[1/（1－0.00446X）]1/2（3）δ1/2p=（PT/760）（4）式中：PT——孔板上风端测得的绝对压力，mmHg；PT=测定当地压力（mmHg）+[该点管内正压（正）或负压（负）（mmH2O）]/13.6760——标准大气压，mmHg；δT=293°/（273°+t°）1/2（5）式中：t°——瓦斯管内测点温度，℃；293°——标准绝对温度，℃；四寸管路d1=49.50mmD=98.28mm则：m=0.2536查（表一）得a0=0.6327K=0.3001六寸管路d1=74.68mmD=151.20mm则：m=0.2439

3、查（表一）得a0=0.6294K=0.6718（二）、在计算过程中为加快计算速度，可把公式中的各项数值表格化，查表得出b、δp、δT。瓦斯浓度校正系数b值表二；瓦斯浓度0123456789(%)01.0001.0021.0041.0071.0091.0111.0141.00161.0191.021101.0241.0261.0281.0311.0321.0351.0381.0401.0431.045201.0481.0501.0531.0561.0581.0601.0631.0661.0681.071301.0741.0771.0801.0821.0851.0881.0911.0

4、951.0971.100401.1031.1061.1091.1131.1161.1191.1221.1251.1281.131501.1341.1371.1411.1441.1481.1511.1541.1581.1621.164601.1681.1721.1761.1791.1821.1861.1901.1941.1981.202701.2061.2101.2141.2201.2221.2251.2291.2341.2381.243801.2471.2511.2561.2601.2631.2691.2741.2781.2831.287901.2921.2971.3021.30

5、81.3131.3181.3241.3281.3341.3391001.344气压校正系数δp值表三；压力压力压力压力压力δpδpδpδpδp(mmHg)(mmHg)(mmHg)(mmHg)(mmHg)1500.4442900.6174300.7525700.8667100.9671550.4522950.6234350.7565750.8707150.9701600.4583000.6294400.7615800.8747200.9731650.4663050.6334450.7655850.8787250.9771700.4723100.6394500.7695900.881

6、7300.9801750.4803150.6434550.7745950.8867350.9841800.4883200.6494600.7786000.8897400.9871850.4933250.6544650.7826050.8927450.9901900.5003300.6594700.7866100.8967500.9931950.5063350.6634750.7916150.9007550.9972000.5133400.6694800.7946200.9037601.0002050.5193450.6744850.7996250.9077651.0032100.

7、5253500.6784900.8036300.9107701.0062150.5323550.6834950.8076350.9147751.0092200.5383600.6895000.8116400.9187801.0132250.5443650.6935050.8156450.9227851.0162300.5503700.6985100.8196500.9257901.0192350.5563750.7025150.8236550.9287951.0232400.56