关于P88例题5-1中,如何查水蒸气热力性质图和表,计算得到以下四组数据: (习题5中的求解类似)
12343214.5/,2144.2/,191.84/,195.3/h kJ kg h kJ kg h kJ kg h kJ kg ====
(1) 1h
在课本P86中,如图5-3,
点1为过热蒸汽,114,400p MPa t C ==︒,故查附录14中
3,400p MPa t C ==︒时,13133231.6/, 6.9231/()h kJ kg s kJ kg K == 5,400p MPa t C ==︒时,15153196.9/, 6.6486/()h kJ kg s kJ kg K == 利用内插法,求得
114,400p MPa t C ==︒时,11?/,?/()h kJ kg s kJ kg K ==
(2) 2h
由图5-3,知点1和点2的熵一样,故
21?/()s s kJ kg K ==
点2为湿饱和蒸汽,由饱和水与饱和蒸汽组成,在条件为20.01p MPa =时,即可通过点2 的熵2s 反求出该点的干度:
2''(1)''(''')s xs x s s x s s =+-=+-,得?x =
再利用干度求出该点的焓2h :
2''(1)''(''')h xh x h h x h h =+-=+-
(其中:'0.6493/(),''8.1505/(),
'191.84/,''2584.4/s kJ kg K s kJ kg K h kJ kg h kJ kg ==== )
(3) 3h
在图5-3中,点3为饱和水,在条件为20.01p MPa =,查附录13,得3191.84/h kJ kg =。
(4) 4h
点3与点4重合,两者的熵一样,即430.6493/()s s kJ kg K ==
,而点4为未饱
和水,该点的压强为14p MPa =,故查附录14,40.6493/()s kJ kg K = 介于0.5709-0.8294之间,故利用内插法, 计算出3MPa 时,40.6493/()s kJ kg K = 所对应的43h 同理,5MPa 时,40.6493/()s kJ kg K = 所对应的45h 再利用内插法计算出,4MPa 时所对应的4h。