Simulation And Experimental Investigation On Heat-recovery Type Air-Cooled Screw Chiller

In this paper, a steady state simulation model of a heat recovery type air cooled screwchiller was created. The performance for heat recovery type R134a air cooled screwchiller under variable operating ambient and variable loads was predicted by using somecommercial software and a FORTRAN program which was compiled by the author. Theunit performance impact of heat recovery rate (capacity) and heat recovery hot wateroutlet temperature was investigated.In order to verify the correctness of the mathematical model, the experiments werecarried out on one modified 90TR air cooled chiller. And the experiments were carried outwhen the loads are 100% (35C ambient), 75% (31.5C ambient), 50% (28C ambient), and25% (24.5C ambient). During the testing, the heat recovery hot water flow rate was fixedand the inlet water temperature was adjusted to achieve the same 50C outlet watertemperature. The simulation results are compared with the experimental results, and it isshown that the simulation results are basically consistent with experimental date.Experimental and simulated results have shown that the cooling capacity of theheat recovery type air cooled chiller will decrease and the power consumption willincrease comparing to standard air cooled chiller. Both discharge pressure and condensingtemperature will increase if heat recovery rate increases while the hot water outlettemperature is fixed, but the cooling capacity and power input of the heat recovery typeair cooled chiller will change little. When the hot water outlet temperature increases, thecooling capacity and COP will significantly decrease. For example, at full load and above25% heat recovery rate, the cooling capacity will decline around 25 kW which is about8 10% of the total capacity when the hot water outlet temperature is increased by 5℃(starts from 45C outlet temperature). And the cooling COP will also decrease around0.3 0.4 which is about 10 15%.Finally, the IPLV (Integrated Part Load Value) performance analysis was made. Theresults showed that the heat recovery can improve the annual overall system efficiencyunder most of the operating conditions because of the extra recovered heat energy. But ifoutlet water temperature higher than 55C and heat recovery rate lower than 30%, the heatrecovery may not be cost effective.