FLUENT材料模型中的NISTRealGas模型

2016-09-04 by:CAE仿真在线来源:互联网

FLUENT的材料模型里面有个NIST Real Gas模型,这个材料模型给与常用制冷剂有关的仿真计算带来了莫大的方便。下面简单介绍一下这个模型的使用。

从事制冷、空调、压缩机等行业的人对REFPROP这个制冷剂数据库软件应该都不陌生。REFPROP是Refrigerant Properties两个单词的缩写,这个软件是由美国国家标准技术研究所NIST(National Institute of Standards and Technology)开发的,软件中包含了几乎所有常用制冷剂(R600,R134a等等)的材料模型。所谓NIST Real Gas模型,就是从REFPROP7.0中导入的制冷剂材料模型。

REFPROP7.0中包含了39种纯制冷剂热动力学和传输特性信息,并且能提供这些制冷剂混合物的特性信息。下表是所有的材料名称。

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模型时,可输入text commant进行激活。具体操作步骤如下:

1.输入激活NIST Real Gas Model的命令:

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

use NIST real gas? [no] yes

如果需要一种以上的制冷剂,则以上命令改为:

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

use multispecies NIST real gas? [no] yes

回车后对话平台会列出可用的pure制冷剂的清单:

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.从列出的清单中选择自己需要的制冷剂:

如果上一步选择的是一种制冷剂,则系统会提示选择一种制冷剂。在提示后输入制冷剂data file名称。这里注意输入内容要包括双引号""、材料名称(如r125)以及扩展名.fld
select real-gas data file [""] "r125.fld"
如果上一步选择的是多制冷剂,则系统会先让你输入制冷剂种类数量:
Number of species [] 3
然后分别输入制冷剂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会从数据库中Load制冷剂数据,并在对话平台报告相关信息:

/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默认为制冷剂是在气体状态下,如果你的运算是在液体状态下进行,则需要输入命令更改制冷剂状态:

define/user-defined/real-gas-models/set-phase Select vapor phase (else liquid)?[no]
通过以上几步就激活了NIST Real Gas模型。
另外使用NIST Real Gas模型还有以下方面需要注意:
1.NIST Real Gas模型激活后FLUENT的Material对话框将不能打开,将不能对材料模型做任何修改。因此在激活该模型之前要对计算所涉及到的固体材料提前设好。
2.使用NIST Real Gas模型时其他流体材料模型将无法使用,比如,无法将空气或水也加入计算中。
3.进出口边界只能设为Pressure-inlet, mass flow-inlet, and pressure-outlet几种。
4.不能使用多相流模型。
5.如果是较低版本的FLUENT,则只能在选用了Coupled Solver时才能激活NIST Real Gas模型。
掌握了这些就可以使用NIST Real Gas模型了。如果还有疑问可以查阅ANSYS FLUENT的帮助文件。下面是帮助信息的链接:
https://www.sharcnet.ca/Software/Fluent12/html/ug/node336.htm#refprop-fluids