Document: NRC Regulatory Guide
Document ID: f4c5fb1d-efb9-4168-9804-5ad3f6f64d06
Document Type: regulatory_guide
Title: Reporting Procedure for Mathematical Models Selected To Predict Heated Effluent Dispersion in Natural Water Bodies
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML0037/ML003739535.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.4
CFR Part: 
CFR Title: 

Content:
eat flux. As discussed in Appendix A, the surface heat flux is taken to be proportional to the product of a surface heat exchange coefficient K and the difference between the actual temperature of the water surface T. and its equilibrium temperature e. The above boundary condition then becomes D3 ;3=I aX3 3=0 = K@,s - e) (B-20) Equations (B-14), (3-17), and (&-20) describe the temperature field in the presence of a thermal discharge. In the absence of a discharge, the equations would be identical in form, with the ambient temperature T.' replacing the general temperature T. Note that the difference Ta Te is the excess temperature defined in Appendix A. If the assumptions are made that (I) the spatial gradients of ambient temperature are small compared with those existing in the priesence of the discharge, and (2) the heat exchange coefficient and the equilibrium temperature are the same with or without the discharge, then the following equation may be written to describe the excess temperature: + !T = (Dj a) at i axj a. axJ (B-2 I) with the surface boundary condition d. Planetaiy Rotation A simple scale analysis can provide an estimate of the importance of rotational effects for a particular tispersion problem. Theoretically, a parcel of water with 8TeI D3 x-o 3X3 .0 = K(T. - T,) = KTe (B-22) The form of Eq. (B-22), with the ambient temperature replacing the equilibrium temperiture, is 4.4-13 identical to that dimcussed in Section 3c of Appendix A. This form is preferred by many workers because of the practical difficulty of obtaining the equilibrium temperature. It should be noted, however, that this simpler form depends upon the validity of the two assumptions given above. 5. techn.a. fr Solving On H ydrodem aWd Thermodynamic Equatiow The mathematical form of the hydrodynamic and thermodynamic equations that govern thermal dispersion having been discussed, it is desirable to review the methods most frequently applied to solve those equations For the most part,