# 查看完整版本 : thermodynamics question

poi098 2017-9-25 20:00

in a closed rigid container with water inside under a process:
*With specific enthalpy of 2000kj/kg in wjole process
*In initial state 30 bars
*in final state 10 bars

(i)Determine the initial state of water

(ii)Find the initial temperature , quality and specific volume of water

bjj123 2017-9-26 09:07

1. 查表
2. 近似公式  : hpt = hft + vft ( P - P sat T )

lightspeed2020 2022-2-9 15:51

[quote]原帖由 [i]bjj123[/i] 於 2017-9-26 09:07 AM 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=468421462&ptid=26950598][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]

1. 查表
2. 近似公式  : hpt = hft + vft ( P - P sat T )

lightspeed2020 2022-2-14 08:36

topochu 2022-2-14 11:28

sylim 2022-3-1 06:34

[quote]原帖由 [i]lightspeed2020[/i] 於 2022-2-14 08:36 AM 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=545515565&ptid=26950598][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]

sylim 2022-3-1 06:37

[quote]原帖由 [i]lightspeed2020[/i] 於 2022-2-9 03:51 PM 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=545341103&ptid=26950598][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]

[[i] 本帖最後由 sylim 於 2022-3-1 07:11 AM 編輯 [/i]]

sylim 2022-3-1 06:39

rhwlam 2022-3-14 08:23

In a closed rigid container with water inside under a process:
* With specific enthalpy of 2000 kJ/kg in the whole process
* Initial state: 30 bars
* Final state: 10 bars

(i) Determine the initial state of water

Saturated steam.

(ii) Find the initial temperature, quality and specific volume of water

Steam table:
[url=https://www.engineeringtoolbox.com/saturated-steam-properties-d_101.html]Properties of Saturated Steam - SI Units (engineeringtoolbox.com)[/url]

Initial temperature: 99.6 deg C (checked from the table above)

Quality of water (xc):
h = xc * hl + (1 - xc) * hs
2000 = xc * 417.5 + (1 - xc) * 2675 (checked from the table above)
xc = 675 / 2257.5 = 0.299

Specific volume (V):
V = xc * Vl + (1 - xc) * Vs
V = 0.299 * 0.001 + (1 - 0.299) * 1.69 Vs is from the table above; and Vl is for water liquid that 1 cm^3 = 1 g stands for a specific volume of 0.001 m^3/kg.)
V = 1.18 m^3/kg

[[i] 本帖最後由 rhwlam 於 2022-3-14 12:30 PM 編輯 [/i]]

Porky_Pig 2022-3-14 23:12

[quote]原帖由 [i]sylim[/i] 於 2022-3-1 06:37 AM 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=546050422&ptid=26950598][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]

Thermodynamics的中文翻譯是「熱動力學」而非「熱力學」，「力學」是mechanics，「動力學」是dynamics或者是kinetics。

Chemical thermodynamics的entropy只是慨念，不會進行任何計算。物理學的統計力學（statistical mechanics）才會以statistics的方式去計算entropy。