Modulation Without Unload Compressor Assessment

Detailed Description

The final output is calculated package power and airflow at the requested point. The model follows a power law between no-load and full-load power. When used as a helper inside the load/unload model, the without unload flag is false and the curve is anchored by the maximum modulating power floor instead.

Power and Airflow Fractions

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Power-law relationship between airflow fraction and power.

\begin{equation}\label{eq:mod-without-unload-power-from-airflow} P = (P_{FL} - P_{NL})f_Q^m + P_{NL} \end{equation}

\begin{equation}\label{eq:mod-without-unload-airflow-from-power} Q = Q_{FL}\left(\frac{f_PP_{FL} - P_{NL}}{P_{FL} - P_{NL}}\right)^{1/m} \end{equation}

For helper mode, the power floor is the maximum modulating power and the high anchor is the maximum package power:

\begin{equation}\label{eq:mod-without-unload-helper-power-from-airflow} P = (P_{max} - P_{max,mod})f_Q^m + P_{max,mod} \end{equation}

\begin{equation}\label{eq:mod-without-unload-helper-airflow-from-power} Q = Q_{FL}\left(\frac{f_PP_{FL} - P_{max,mod}}{P_{max} - P_{max,mod}}\right)^{1/m} \end{equation}

Symbols

\(P\)	Calculated package power \([\unit{ \kilo\watt}]\)
\(Q\)	Calculated airflow \([\unit{ \acfm}]\)
\(P_{FL}\)	Full-load package power \([\unit{ \kilo\watt}]\)
\(Q_{FL}\)	Full-load airflow \([\unit{ \acfm}]\)
\(P_{NL}\)	No-load package power \([\unit{ \kilo\watt}]\)
\(P_{max}\)	Maximum package power in helper mode \([\unit{ \kilo\watt}]\)
\(P_{max,mod}\)	Maximum modulating power floor \([\unit{ \kilo\watt}]\)
\(f_P\)	Fraction of full-load power \([\unit{ \unitless}]\)
\(f_Q\)	Fraction of full-load airflow \([\unit{ \unitless}]\)
\(m\)	Modulation exponent \([\unit{ \unitless}]\)

Modules
	Modulation Without Unload Formula
	Power-law relationship between airflow fraction and power.

Files
file	modulation_without_unload_compressor.h
	Modulating compressor assessment model declarations.