arp_1998
========

V\. D\. Arp, R\. D\. McCarty and D\. G\. Friend, "Thermophysical Properties of Helium\-4 from 0\.8 to 1500 K with Pressures to 2000 MPa", NIST Technical Note 1334 \(revised\) \(1998\)

`Source record <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/arp_1998.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.6028/nist\.tn\.1334 <https://doi.org/10.6028/nist.tn.1334>`__

**Source kind:** fit

**Recorded technique:** A compilation of correlations for the thermodynamic and transport properties of helium\-4 and the computer program that evaluates them\. The viscosity is Steward and Wallace's \(1971\) correlation below 100 K and, above 110 K, Maitland and Smith's \(1971\) dilute\-gas correlation of experimental data plus an excess term \(section 4\.2\)\.

**Materials in structured entries:** He

**Dataset quantities:** None recorded.

**Contents:** 0 datasets; 1 formula.

Curation notes
--------------

Identity VALIDATED\_WITH\_WARNINGS by the library; the library's record names Arp alone, the title page \(pdf page 3\) all three authors\.

THE DILUTE VISCOSITY \(section 4\.2\.2, Eq\. 8\)\: eta\_o\(T\) = 196 T^0\.71938 exp\(12\.451/T \- 295\.67/T^2 \- 4\.1249\), in ug/\(cm s\) \(= 0\.1 uPa s\), T in K\. It is Maitland and Smith's correlation, used 'for all T \> 110 K'; between 100 K and 110 K the program averages it linearly with Steward's dilute values\. The equations are given for 100\-300 K and used unchanged above 300 K, where only the excess term is frozen at its 300 K form \(section 4\.2\.3\); the tables run to 1500 K\. optmat takes Eq\. \(8\) over 110\-1500 K\.

UNCERTAINTY\: 'The uncertainty of the viscosity for T \> 100 K is estimated to be maximum of \+\-10 percent' \(section 4\.2\.3\), for the correlation as a whole, dilute gas and dense fluid alike; no separate figure is given for the dilute gas\.

REPRODUCED\: CoolProp 8\.0\.0's helium viscosity \(reference key Arp\-NIST\-1998\) at 1e\-6 mol/m^3 equals Eq\. \(8\) to 1\.1e\-11 from 110 K to 900 K \(computed 2026\-09\-30\)\. At 105 K it also equals Eq\. \(8\), without the program's 100\-110 K average\. CoolProp reports the whole value as its 'critical' contribution, not its 'dilute' one; optmat takes the total at vanishing density\.

**Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets
--------

No datasets are recorded.

Formulas
--------

arp\_1998/eq8
~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "eq8",
     "material": "He",
     "equation": "Eq. (8), section 4.2.2",
     "printed": "eta_o(T) = 196 T^0.71938 exp(12.451/T - 295.67/T^2 - 4.1249)",
     "variable": "T in K; eta_o in ug/(cm s), 1 ug/(cm s) = 1e-7 Pa s",
     "range": "T > 110 K (Maitland and Smith); used to 1500 K",
     "coefficients": {
       "a": "196",
       "b": "0.71938",
       "c": "12.451",
       "d": "295.67",
       "e": "4.1249"
     },
     "check": "CoolProp 8.0.0 equals it to 1.1e-11, 110-900 K (tests/test_transport.py)."
   }

Corrections
-----------

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the :doc:`review register </register>` for the checks and decisions.