Optimization Of Operating Parameters And Load Allocation Schemes Of Refrigeration Plants

Nowdays, vapor compression and absorption refrigerating units are two leading cooling units. Firstly, exergy analysis method was used to establish the black box models of these two units'major equipments. The programs which were used to calculate exexgy loss and exergy efficiency were compiled by VB. The primary energy consumption and economic efficiency of these two type coolers were compared in this paper. Cooling supply cost per cooling capability was used as an index to compare the economic efficiency of them. Analyses of the composition and influence factors of cooling supply cost were presented and its derived formulas were given.Because the exergy analysis method can't guide designers to cut down the initial investment, the pinch point temperature differences analysis method was introduced to optimum the cooler's operating parameters. This method has achieved success in the optimization of large-scale heat exchange unit.Minimizing the sum of the initial investment and operating cost was employed as program's objective. Condenser and evaporator's pinch point temperature difference were used as control variables.The main program included four blockettes: property calculation, pinch point temperature calculation, condenser and evaporator's heat transfer calculation and COP calculation. Then the relation curves of the changes of pinch point temperature difference to COP and to initial investment were obtained through calculations. These curves showed that reducing pinch point temperature can raise COP, but cooler's initial cost increased simultaneously.So the problem of payback period for increased initial cost was analysed here.Then the optimum pinch point temperature differences of the coolers which were given cooling capability and COP were obtained by this program.The pinch point temperature differences analysis method mentioned above was aimed at the optimization of single cooling unit's operating parameters based on the given cooling load. In fact, coolers operated at part load at the most times. Furthermore, many air conditioning systems use more than one cooler. So it's important to establish optimum capability allocation scheme and load sharing strategy. In this paper, the Integrated Part Load Value was introduced to evaluate the single cooing unit's part-load performance. Load-frequency method was employed to calculate total cost of the air conditioning system with multi chillers. Program, aimed at reducing annual operating cost, was complied by Excel to obtain the system's optimum capacity allocation scheme and load sharing strategy. Lastly, calculations and analyses of the variable chilled water flow system's performance were given.The results showed that the variable chilled water flow system's energy consumption is less than constant flow system's.Furthermore, the advantages of the variable flow system are more obvious when coolers operating at the low load frenquency.