Merge remote-tracking branch 'firemodels/master' into ht3d

Manuals/FDS_User_Guide/FDS_User_Guide.tex

@@ -3450,13 +3450,13 @@ \section{HVAC Systems}
 
 As described in the Technical Reference Manual, the HVAC pressure solution is not directly coupled to the FDS pressure solution. Rather there is implicit coupling using the wall boundary condition for HVAC vents. At times this can result in stability problems. There are two methods of attempting to resolve this.
 
-The first method is the keyword {\ct HVAC\_PRES\_RELAX} on the {\ct MISC} line with a default value of 0.5. At each time step FDS evaluates the average pressure in the FDS gas cells adjacent to nodes connecting the FDS domain to the HVAC network. The node pressure at time step n+1 is taken as:
+The first method is the keyword {\ct HVAC\_PRES\_RELAX} on the {\ct MISC} line with a default value of 1.0. At each time step FDS evaluates the average pressure in the FDS gas cells adjacent to nodes connecting the FDS domain to the HVAC network, $P_{FDS}$. The node pressure at time step n+1,$P_{node}^{n+1}$ , is taken as:
 \be
-P_{node}^{n+1}=P_{FDS} \; (1-{\ct HVAC\_PRES\_RELAX}) \; + \; P_{node}^n \; {\ct HVAC\_PRES\_RELAX}
+P_{node}^{n+1}=P_{node}^n \; (1-{\ct HVAC\_PRES\_RELAX}) \; + \; P_{FDS}^{n+1} \; {\ct HVAC\_PRES\_RELAX}
 \ee
-Setting this parameter closer to 1 reduces the sensitivity of the HVAC solution to short, transient pressure changes in the FDS domain; however, doing so will also result in the HVAC solution lagging for longer duration pressure changes.
+Setting this parameter closer to 0 reduces the sensitivity of the HVAC solution to short, transient pressure changes in the FDS domain; however, doing so will also result in the HVAC solution lagging for longer duration pressure changes. 
 
-The second method is setting the keyword {\ct HVAC\_LOCAL\_PRESSURE} on the {\ct MISC} line. When set, this will cause FDS to use the {\ct ZONE} pressure at a vent plus the stagnation pressure of any flow normal to the vent to determine the pressure boundary condition for a node connected to the FDS domain rather than the {\ct ZONE} pressure plus the the pressure derived from the local value of $\cH$. Note this means a sealed room must have a {\ct ZONE} assigned to it.
+The second method is setting the keyword {\ct HVAC\_LOCAL\_PRESSURE} on the {\ct MISC} line. When set, this will cause FDS to use the {\ct ZONE} pressure at a vent plus the stagnation pressure of any flow normal to the vent to determine the pressure boundary condition for a node connected to the FDS domain rather than the {\ct ZONE} pressure plus the the pressure derived from the local value of $\cH$. 
 
 \subsection{HVAC Duct Parameters}
 \label{info:HVACduct}
@@ -3572,7 +3572,7 @@ \subsection{HVAC Node Parameters}
 
 It is permissible to have individual {\ct VENT} lines for an HVAC system span multiple meshes.
 
-Note that a {\ct VENT} being used for an HVAC system should not have a {\ct CTRL\_ID} or {\ct DEVC\_ID}. If you need to turn on or off a {\ct VENT} connected to an HVAC system, use a damper in the duct connected to {\ct VENT}.
+Note that a {\ct VENT} being used for an HVAC system must be present throughout the simulation. The {\ct VENT} should not have a {\ct CTRL\_ID} or {\ct DEVC\_ID}. This also includes the solid surface it is attached; i.e., any {\ct OBST} the {\ct VENT} is attached to also needs to be present throughout the simulation. If you need to turn on or off a {\ct VENT} connected to an HVAC system, put a damper in the duct connected to {\ct VENT}.
 
 \subsection{HVAC Fan Parameters}
 \label{info:HVACfan}

Source/read.f90

@@ -15110,7 +15110,7 @@ SUBROUTINE GET_QUANTITY_INDEX(SMOKEVIEW_LABEL,SMOKEVIEW_BAR_LABEL,OUTPUT_INDEX,O
 
       IF (OUTPUT_QUANTITY(ND)%CELL_L_REQUIRED .AND. (HVAC_MASS_TRANSPORT .NEQV. .TRUE.)) THEN
          WRITE(MESSAGE,'(5A)')  'ERROR: Output QUANTITY ',TRIM(QUANTITY),' in DUCT_ID ',TRIM(DUCT_ID),&
-         ' requires HVAC_MASS_TRANSPORT to be set on MISC'
+         ' requires HVAC_MASS_TRANSPORT to be active.'
          CALL SHUTDOWN(MESSAGE) ; RETURN
       ENDIF