FDS Source: Fix issue 13862. Missing ABS for duct velocity in UPDATE_HVAC_MASS_TRANSPORT

Author: drjfloyd

Manuals/FDS_User_Guide/FDS_User_Guide.tex

@@ -3916,7 +3916,7 @@ \subsection{Louvered HVAC Vents}
 \subsection{HVAC Mass Transport}
 \label{info:hvacmasstransport}
 
-FDS can account for the time delay of species and enthalpy transport through HVAC networks by discretizing individual HVAC ducts. This can by done using either \ct{N_CELLS} on an HVAC duct input or by setting \ct{HVAC_MASS_TRANSPORT_CELL_L}. The input \ct{N_CELLS} divides the length on the duct into \ct{N_CELLS} uniform segments. The parameter \ct{HVAC_MASS_TRANSPORT_CELL_L} defines a cell length that is applied to all ducts in an input file unless overridden by \ct{N_CELLS}. IF specified, the number of cells for a duct is taken as the nearest integer of the duct \ct{LENGTH} divided by \ct{HVAC_MASS_TRANSPORT_CELL_L}. The current HVAC solver does not account for heat loss in the HVAC network.
+FDS can account for the time delay of species and enthalpy transport through HVAC networks by discretizing individual HVAC ducts. This can by done using either \ct{N_CELLS} on an HVAC duct input or by setting \ct{HVAC_MASS_TRANSPORT_CELL_L} on \ct{MISC}. The input \ct{N_CELLS} divides the length on the duct into \ct{N_CELLS} uniform segments. The parameter \ct{HVAC_MASS_TRANSPORT_CELL_L} defines a cell length that is applied to all ducts in an input file unless overridden by \ct{N_CELLS}. When specified, the number of cells for a duct is the duct \ct{LENGTH} divided by \ct{HVAC_MASS_TRANSPORT_CELL_L} rounded to the nearest integer (minimum of 1 cell). The current HVAC solver does not account for heat loss in the HVAC network.
 
 If a duct is discretized, then all other ducts in that ductrun must also be discretized. There is no requirement that the same cell size be used for all ducts in a ductrun. A ductrun is any collection of interconnected HVAC components where a path exists between two components via traversing ducts in the ductrun.
 
@@ -12577,7 +12577,7 @@ \section{\texorpdfstring{{\tt MISC}}{MISC} (Miscellaneous Parameters)}
 \ct{H_F_REFERENCE_TEMPERATURE}                  & Real         & Section~\ref{info:enthalpy}             & $^\circ$C  & 25.               \\ \hline
 \ct{HUMIDITY}                                      & Real         & Section~\ref{info:humidity}             & \%         & 40.               \\ \hline
 \ct{HVAC_LOCAL_PRESSURE}                         & Logical      & Section~\ref{info:HVAC}                 &            &  \ct{T}          \\ \hline
-\ct{HVAC_MASS_TRANSPORT_CELL_L}                & Logical      & Section ~\ref{info:hvacmasstransport}   &            & \ct{F}           \\ \hline
+\ct{HVAC_MASS_TRANSPORT_CELL_L}                & Real          & Section ~\ref{info:hvacmasstransport}   & m          &                   \\ \hline
 \ct{HVAC_PRES_RELAX}                             & Real         & Section ~\ref{info:HVAC}                &            & 1.0               \\ \hline
 \ct{HVAC_QFAN}                                    & Logical      & Section ~\ref{info:HVAC_QFAN}           &            & \ct{F}           \\ \hline
 \ct{IBLANK_SMV}                                   & Logical      & Section~\ref{info:SLCF}                 &            & \ct{T}           \\ \hline

Source/hvac.f90

@@ -3510,17 +3510,18 @@ SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
    MASS_FLUX = DU%RHO_D * DU%VEL(NEW)
 
    ! Set up of CFL and sub time step
-   DT_CFL = DU%DX/(2*DU%VEL(NEW)) ! CFL for Godunov pure upwinding scheme
+   DT_CFL = ABS(DU%DX/(2*DU%VEL(NEW))) ! CFL for Godunov pure upwinding scheme
    N_SUBSTEPS = MAX(1,CEILING(DT/DT_CFL))
    DT_DUCT = DT/REAL(N_SUBSTEPS,EB)
 
+   ! Set upwind face indices and allocate flux arrays
+   ALLOCATE(ZZ_F(0:DU%N_CELLS,N_TRACKED_SPECIES))
+   ALLOCATE(CPT_F(0:DU%N_CELLS))
+   ALLOCATE(CPT_C(DU%N_CELLS))
+   ALLOCATE(RHOCPT_C(DU%N_CELLS))
+   ALLOCATE(RHOZZ_C(DU%N_CELLS,N_TRACKED_SPECIES))
+
    SUBSTEP_LOOP: DO NS = 1,N_SUBSTEPS
-      ! Set upwind face indices and allocate flux arrays
-      ALLOCATE(ZZ_F(0:DU%N_CELLS,N_TRACKED_SPECIES))
-      ALLOCATE(CPT_F(0:DU%N_CELLS))
-      ALLOCATE(CPT_C(DU%N_CELLS))
-      ALLOCATE(RHOCPT_C(DU%N_CELLS))
-      ALLOCATE(RHOZZ_C(DU%N_CELLS,N_TRACKED_SPECIES))
 
       ! Populates upwind face variables, accounting for direction of flow (i.e. includes relevant node value as first/last face)
       IF (DU%VEL(NEW)>0._EB) THEN
@@ -3556,13 +3557,14 @@ SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
          DU%CP_C(NC) = HGAS / DU%TMP_C(NC)
       ENDDO DU_UPDATE_LOOP
 
-      DEALLOCATE(RHOZZ_C)
-      DEALLOCATE(ZZ_F)
-      DEALLOCATE(CPT_F)
-      DEALLOCATE(CPT_C)
-      DEALLOCATE(RHOCPT_C)
-
    ENDDO SUBSTEP_LOOP
+
+   DEALLOCATE(RHOZZ_C)
+   DEALLOCATE(ZZ_F)
+   DEALLOCATE(CPT_F)
+   DEALLOCATE(CPT_C)
+   DEALLOCATE(RHOCPT_C)
+   
 ENDDO DUCT_LOOP