Determining the coefficient of performance of a refrigeration system

Claim 1

A method for reducing the coefficient of performance to a design value from measured temperature conditions of a vapor compression type refrigeration system of the type having series arranged compressor, condenser and evaporator units and an electric motor for driving said compressor unit, said system further having a condenser water supply line and evaporator chilled water supply and return lines, said method comprising the steps of: storing a value (CWF) for the chilled water flow through said condenser; sensing the condenser water supply temperature (T con ), sensing the evaporator water supply and return temperatures (T chw ,in and T chw ,out), sensing the power input (φ) to said motor; calculating the cooling load (Q c )* from the expression Q c =CWF*(T chw ,in -T chw ,out); storing the manufacturers' performance data for said system comprising the condenser supply water design (T con ,D) and the evaporator return water design temperature (T chw ,D); storing a value (α temp ) which is the ratio of the required change in condenser temperature to a unit change in chilled water temperature to maintain the same rated chiller capacity; calculating the equivalent temperature (T r ) which compensates for variation from the given design temperatures from the expression T.sub.r =(T.sub.con -T.sub.con,D)/α.sub.temp -(T.sub.chw -T.sub.chw,D), storing experimentally determined coefficients b 1 , b 2 , and b 3 for the quadratic expression βcap=b.sub.1 +b.sub.2 *T.sub.r +b.sub.3 *(T.sub.r).sup.2 wherein β cap is the ratio of the available capacity (CAP) at the actual chilled water and condenser water conditions to the design capacity (CAP D ); calculating said β cap and said CAP; calculating the part-load ratio Γ load from the expression Γ load =Q c /CAP, storing experimentally determined coefficients a 1 , a 2 and a 3 for the quadratic expression δ.sub.pow =a.sub.1 +a.sub.2 *Γ.sub.load +a.sub.3 *(Γ.sub.load).sup.2 wherein δ pow is a fraction of full-load power, calculating the full-load power (PFL) from the expression PFL=φ*δ pow ; and calculating said COPA from the expression COPA=CAP/PFL.

Claim 2

A method for reducing the coefficient of performance to a design value from measured temperature conditions of a vapor compression type refrigeration system of the type having series arranged compressor, condenser and evaporator units and an electric motor for driving said compressor unit, said system further having a condenser water supply line and evaporator chilled water supply and return lines, said method comprising the steps of: storing a value (CWF) for the chilled water flow through said condenser; sensing the condenser water supply temperature (T con ), sensing the evaporator water supply and return temperatures (T chw ,in and T chw ,out), sensing the power input (φ) to said motor; calculating the cooling load (Q c )* from the expression Q c =CWF*(T chw ,in -T chw ,out); storing the manufacturers' performance data for said system comprising the condenser supply water design (T con ,D) and the evaporator return water design temperature (T chw ,D); storing a value (α temp ) which is the ratio of the required change in condenser temperature to a unit change in chilled water temperature to maintain the same rated chiller capacity; calculating the equivalent temperature (T r ) which compensates for variation from the given design temperatures from the expression T.sub.r =(T.sub.con -T.sub.con,D)/α.sub.temp -(T.sub.chw -T.sub.chw,D), storing experimentally determined coefficients b 1 , b 2 , and b 3 for the quadratic expression βcap=b.sub.1 +b.sub.2 *T.sub.r +b.sub.3 *(T.sub.r).sup.2 wherein β cap is the ratio of the available capacity (CAP) at the actual chilled water and condenser water conditions to the design capacity (CAP D ); calculating said β cap and said CAP; calculating the part-load ratio Γ load from the expression Γ load =Q c /CAP, storing experimentally determined coefficients a 1 , a 2 and a 3 for the quadratic expression δ.sub.pow =a.sub.1 +a.sub.2 *Γ.sub.load +a.sub.3 *(Γ.sub.load).sup.2 wherein δ pow is a fraction of full-load power, calculating the full-load power (PFL) from the expression PFL=φ*δ pow ; and calculating said COPA from the expression COPA=CAP/PFL.