FLUENT材料模型中的NISTRealGas模型

2016-09-04 by:CAE仿真在線來源:互聯網

FLUENT的材料模型里面有個NIST Real Gas模型,這個材料模型給與常用制冷劑有關的仿真計算帶來了莫大的方便。下面簡單介紹一下這個模型的使用。

從事制冷、空調、壓縮機等行業的人對REFPROP這個制冷劑數據庫軟件應該都不陌生。REFPROP是Refrigerant Properties兩個單詞的縮寫,這個軟件是由美國國家標準技術研究所NIST(National Institute of Standards and Technology)開發的,軟件中包含了幾乎所有常用制冷劑(R600,R134a等等)的材料模型。所謂NIST Real Gas模型,就是從REFPROP7.0中導入的制冷劑材料模型。

REFPROP7.0中包含了39種純制冷劑熱動力學和傳輸特性信息,并且能提供這些制冷劑混合物的特性信息。下表是所有的材料名稱。

Table 8.16.1:Hydrocarbons and Refrigerants Supported by REFPROPv7.0


1butene	acetone	ammonia	argon	benzene	butane

dodecane	cis-butene	c4f10	c5fl2	co	co2
(c12.fld)	(c2butene.fld)

cos	cyclohexane	cyclopropane	deuterium	heavy water	decane
	(cyclohex.fld)	(cyclopro.fld)	(d2.fld)	(d2o.fld)

dimethylether	ethane	ethanol	ethylene	fluorine	h2s
(dme.fld)

helium	heptane	hexane	hydrogen	ibutene	ihexane

ipentane	isobutene	krypton	methane	methanol	n2o

neon	neopentane	nf3	nitrogen	nonane	octane
	(neopentn.fld)

oxygen	parahydrogen	pentane	propane	propylene	propyne
	(parahyd.fld)			(propylen.fld)

r11	r113	r114	r115	r116	r12

r123	r124	r125	r13	r134a	r14

r141b	r142b	r143a	r152a	r21	r218

r22	r227ea	r23	r236ea	r236fa	r245ca

r245fa	r32	r365mfc	r41	rc318	sf6

so2	trans-butene	toluene	water	xenon
	(t2butene.fld)

FLUENT中要使用NIST Real Gas模型時,可輸入text commant進行激活。具體操作步驟如下:

1.輸入激活NIST Real Gas Model的命令:

define/user-defined/real-gas-models/nist-real-gas-model

use NIST real gas? [no] yes

如果需要一種以上的制冷劑,則以上命令改為:

define/user-defined/real-gas-models/nist-multispecies-real-gas-model

use multispecies NIST real gas? [no] yes

回車后對話平臺會列出可用的pure制冷劑的清單:

1butene.fld acetone.fld ammonia.fld argon.fld benzene.fld butene.fld c12.fld c2butene.fld c4fl0.fld c5fl2.fld co.fld co2.fld cos.fld cyclohex.fld cyclopro.fld d2.fld d2o.fld decane.fld dme.fld ethane.fld ethanol.fld ethylene.fld fluorine.fld h2s.fld helium.fld heptane.fld hexane.fld hydrogen.fld ibutene.fld ihexane.fld ipentane.fld isobutan.fld krypton.fld methane.fld methanol.fld n2o.fld neon.fld neopentn.fld nf3.fld nitrogen.fld nonane.fld octane.fld oxygen.fld parahyd.fld pentane.fld propane.fld propylen.fld propyne.fld r11.fld r113.fld r114.fld r115.fld r116.fld r12.fld r123.fld r124.fld r125.fld r13.fld r134a.fld r14.fld r141b.fld r142b.fld r143a.fld r152a.fld r218.fld r21.fld r22.fld r227ea.fld r23.fld r236ea.fld r236fa.fld r245ca.fld r245fa.fld r32.fld r365mfc.fld r41.fld rc318.fld sf6.fld so2.fld t2butene.fld toluene.fld water.fld xenon.fld

2.從列出的清單中選擇自己需要的制冷劑:

如果上一步選擇的是一種制冷劑,則系統會提示選擇一種制冷劑。在提示后輸入制冷劑data file名稱。這里注意輸入內容要包括雙引號""、材料名稱(如r125)以及擴展名.fld
select real-gas data file [""] "r125.fld"
如果上一步選擇的是多制冷劑,則系統會先讓你輸入制冷劑種類數量:
Number of species [] 3
然后分別輸入制冷劑data file:
select real-gas data file [""] "nitrogen.fld" select real-gas data file [""] "co2.fld" select real-gas data file [""] "r22.fld"
然后FLUENT會從數據庫中Load制冷劑數據,并在對話平臺報告相關信息:

/usr/local/Fluent.Inc/fluent6.2/realgas/lib/r125.fld Opening "/usr/local/Fluent.Inc/fluent6.2/realgas/ultra/librealgas.so"...Setting material "air" to a real-gas... Matl name: "R125" : "pentafluoroethane!full name" : "354-33-6"Mol Wt: 120.021 Critical properties: Temperature : 339.173 (K) Pressure: 3.6177e+06 (Pa) Density: 4.779 (mol/L) 573.582 (kg/m^3) Equation Of State (EOS) used:Helmholtz Free Energy (FEQ)EOS:"FEQHelmholtz equation of state for R-125 of Lemmon and Jacobsen (2002)." EOS Range of applicability Min Temperature: 172.52 (K) Max Temperature: 500 (K) Max Density: 1691.1 (kg/m^3) Max Pressure: 6e+07 (Pa) Thermal conductivity Range of applicability Min Temperature: 172.52 (K) Max Temperature: 500 (K) Max Density: 1691.1 (kg/m^3) Max Pressure: 6e+07 (Pa) Viscosity Range of applicability Min Temperature: 172.52 (K) Max Temperature: 500 (K) Max Density: 1692.3 (kg/m^3) Max Pressure: 6e+07 (Pa)

3.FLUENT默認為制冷劑是在氣體狀態下,如果你的運算是在液體狀態下進行,則需要輸入命令更改制冷劑狀態:

define/user-defined/real-gas-models/set-phase Select vapor phase (else liquid)?[no]
通過以上幾步就激活了NIST Real Gas模型。
另外使用NIST Real Gas模型還有以下方面需要注意:
1.NIST Real Gas模型激活后FLUENT的Material對話框將不能打開,將不能對材料模型做任何修改。因此在激活該模型之前要對計算所涉及到的固體材料提前設好。
2.使用NIST Real Gas模型時其他流體材料模型將無法使用,比如,無法將空氣或水也加入計算中。
3.進出口邊界只能設為Pressure-inlet, mass flow-inlet, and pressure-outlet幾種。
4.不能使用多相流模型。
5.如果是較低版本的FLUENT,則只能在選用了Coupled Solver時才能激活NIST Real Gas模型。
掌握了這些就可以使用NIST Real Gas模型了。如果還有疑問可以查閱ANSYS FLUENT的幫助文件。下面是幫助信息的鏈接:
https://www.sharcnet.ca/Software/Fluent12/html/ug/node336.htm#refprop-fluids