An Aerodynamic Investigation of a Centrifugal Compressor for HCFC123

The experimental investigation of a centrifugal compresso r is carried out to improve HCFC123 compression performance. A CFCll c ompressor applying HCFC123 shows a lowered adiabatic head rise, efficie ncy, and volume flow. Another CFC!l compressor with HCFC123 and a modifie d impeller shows a result comparable to the CFCll compression case. A tan dem impeller is designed to cover the volume flow increase for HCFC1Z3. T he performance of this impeller is sufficient to absorb the volume flow inc rease and additionally some efficiency improvement is obtained. INTRODUCTION Although CFCll is widely used for centrifugal chillers, its production will be stopped because of its high ozone-depleting potential. As the HCFC1Z3 is the best possible subsutitution refrigerant fo r CFCll, the development program for a HCFC123 centrifugal chiller was p lanned and implemented. During the program, testing was carried out to o btain the character of a 300 RT CFCll centrifugal chiller filled with HC FC123, As a result, we experienced a decrease in capacity of ten odd per cen t and an energy consumption increase between 5 and 10%, The direct cause of this performance degradation was presumed to be the difference in the rmodynamic properties of CFCll and HCFC123. The theoretical compression work and volume flow rate, per unit refrigerating capacity of HCFC123, are higher than those of CFCll. The heavier molecular weight of HCFC123 was considered to cause this degradation in compressor performance leading to overall lower chiller performance. Akitani and Nakaya [1] experimented with CFCll and HCFC 123 in the same compressor. They concluded that an HCFC123 compre ssor with a CFCll compressor performance level could be realized by an app ropriate impeller design. With this background, an aerodynamic investigatio n was made to improve the compressor performance for HCFC123. The aim o f this investigation is not only to improve energy consumption, but to d evelop a compact machine. HCFC123 compression performances with a CFCll im peller and with a modified impeller are presented, The performance with a tandem impeller