Documentation-only fixes

doc/engineering-reference/src/simulation-models-encyclopedic-reference-002/cooling-towers-and-evaporative-fluid-coolers.tex

@@ -350,7 +350,7 @@ \subsubsection{Tower Heat Rejection}\label{tower-heat-rejection}
 
 Approach is the approach temperature (\(^{\circ}\)C) which is equal to the outlet water temperature minus the inlet air wet-bulb temperature
 
-FRair is the air flow rate ratio (actual air flow rate divided by design air flow rate)
+FRair is the ideal fan power ratio, computed as the cube of the air flow rate ratio (actual air flow rate divided by design air flow rate)
 
 FRwater is the water flow rate ratio (actual water flow rate divided by design water flow rate)
 

doc/engineering-reference/src/surface-heat-balance-manager-processes/inside-heat-balance.tex

@@ -792,6 +792,8 @@ \subsubsection{TARP Algorithm}\label{tarp-algorithm}
 
 The comprehensive natural convection model, accessed using the keyword ``TARP,'' correlates the convective heat transfer coefficient to the surface orientation and the difference between the surface and zone air temperatures (where $\Delta$T = Surface Temperature - Air Temperature).~ The algorithm is taken directly from Walton (1983).~ Walton derived his algorithm from ASHRAE literature which can be found in the ASHRAE Handbook (for example , the  ASHRAE Handbook of Fundamentals 2001, Table 5 on p.~3.12) which gives equations for natural convection heat transfer coefficients in the turbulent range for large, vertical plates and for large, horizontal plates facing upward when heated (or downward when cooled).~~ A note in the text also gives an approximation for large, horizontal plates facing downward when heated (or upward when cooled) recommending that it should be half of the facing upward value.~ Walton adds a curve fit as a function of the cosine of the tilt angle to provide intermediate values between vertical and horizontal.~ The curve fit values at the extremes match the ASHRAE values very well.
 
+\textbf{Note:} Surface orientation in EnergyPlus is defined by the outward-pointing normal, i.e., the normal directed away from the zone interior. Under this convention, a floor is a \emph{downward facing} surface (its outward normal points down) and a ceiling is an \emph{upward facing} surface (its outward normal points up). The conditional cases below use this convention, which is opposite to the physical orientation referenced in the ASHRAE description above. As noted in the source code, callers passing surface tilt into the routine for interior heat balance use the negative of $\cos(\text{Tilt})$ to account for this.
+
 For no temperature difference OR a vertical surface, the following correlation is used:
 
 \begin{equation}
@@ -800,15 +802,15 @@ \subsubsection{TARP Algorithm}\label{tarp-algorithm}
 
 It should be noted that h is zero when the temperature difference is zero.
 
-For ($\Delta$T \textless{} 0.0 AND an upward facing surface)~ OR~ ($\Delta$T \textgreater{} 0.0 AND an downward facing surface), an enhanced convection correlation is used:
+For ($\Delta$T \textless{} 0.0 AND an upward facing surface, e.g., a ceiling cooler than the zone air)~ OR~ ($\Delta$T \textgreater{} 0.0 AND an downward facing surface, e.g., a floor warmer than the zone air), an enhanced convection correlation is used:
 
 \begin{equation}
 h = \frac{{9.482{{\left| {\Delta T} \right|}^{\frac{1}{3}}}}}{{7.238 - \left| {\cos \Sigma } \right|}}
 \end{equation}
 
 where $\Sigma$ is the surface tilt angle.
 
-For ($\Delta$T \textgreater{} 0.0 AND an upward facing surface)~ OR~ ($\Delta$T \textless{} 0.0 AND an downward facing surface)], a reduced convection correlation is used:
+For ($\Delta$T \textgreater{} 0.0 AND an upward facing surface, e.g., a ceiling warmer than the zone air)~ OR~ ($\Delta$T \textless{} 0.0 AND an downward facing surface, e.g., a floor cooler than the zone air), a reduced convection correlation is used:
 
 \begin{equation}
 h = \frac{{1.810{{\left| {\Delta T} \right|}^{\frac{1}{3}}}}}{{1.382 + \left| {\cos \Sigma } \right|}}

doc/input-output-reference/src/overview/group-fans.tex

@@ -685,7 +685,7 @@ \subsubsection{Inputs}\label{inputs-3-014}
 
 \paragraph{Field: Balanced Exhaust Fraction Schedule Name}\label{field-balanced-exhaust-fraction-schedule-name}
 
-This field is optional. If it is not used, then all the exhaust air flow is assumed to be unbalanced by any simple airflows, such as infiltration, ventilation, or zone mixing. Unbalanced exhaust is then modeled as being provided by the outdoor air system in the central air system. The modeling of unbalanced will reduce the flow rates at the zone's return air node by the flow rate that is being exhausted and will ensure that the outdoor air flow rate is sufficient to serve the exhaust. If this field is used, then enter the name of a schedule with fractional values between 0.0 and 1.0, inclusive. This fraction is applied to the exhaust fan flow rate and the model tracks the portion of the exhaust that is balanced. Balanced exhaust is then modeled as being provided by simple airflows and does not impact the central air system return air or outdoor air flow rates. For example, if a kitchen zone with an exhaust fan is designed to draw half of its make up air from a neighboring dining room and the other half from the outdoor air system, then a schedule value of 0.5 could be used here. This input field must be blank when the zone air flow balance is enforced. If user specifies a schedule and zone air flow balance is enforced, then EnergyPlus throws a warning error message, ignores the schedule and simulation continues.
+This field is optional. If it is not used, then all the exhaust air flow is assumed to be unbalanced by any simple airflows, such as infiltration, ventilation, or zone mixing. Unbalanced exhaust is then modeled as being provided by the outdoor air system in the central air system. The modeling of unbalanced will reduce the flow rates at the zone's return air node by the flow rate that is being exhausted and will ensure that the outdoor air flow rate is sufficient to serve the exhaust. If this field is used, then enter the name of a schedule with fractional values between 0.0 and 1.0, inclusive. This fraction is applied to the exhaust fan flow rate and the model tracks the portion of the exhaust that is balanced. Balanced exhaust is then modeled as being provided by simple airflows and does not impact the central air system return air or outdoor air flow rates. For example, consider a kitchen zone with an exhaust fan designed to draw 70\% of its make-up air from a neighboring dining room (via zone mixing or infiltration) and the remaining 30\% from the central outdoor air system. Because this field specifies the \emph{balanced} fraction (i.e., the portion supplied by simple airflows rather than the central OA system), a schedule value of 0.7 would be used here. This input field must be blank when the zone air flow balance is enforced. If user specifies a schedule and zone air flow balance is enforced, then EnergyPlus throws a warning error message, ignores the schedule and simulation continues.
 
 \subsubsection{Outputs}\label{outputs-3-007}