| COPECH | coefficient of performance for electrical driven chiller | ( ) |
| COPGCH | coefficient of performance for gas driven chiller | ( ) |
| COPHCP | coefficient of performance for hybrid chiller plant | ( ) |
| Ec | electrical energy cost | (EGP) |
| Gc | natural gas cost | (EGP) |
| Ic | Initial cost per chiller | (EGP) |
| NECH | number of electrical driven chillers | (chiller) |
| NGCH | number of gas driven chillers | (chiller) |
| Pcomp | centrifugal compressor power | (kW) |
| Ppump | solute pump power | (kW) |
| Qcc | cooling capacity | (TR) |
| t | time | (hr) |
| T | temperature | (˚C) |
| Tc | total running cost, (Ec + Gc + Wc) | (EGP) |
|
| natural gas volume flow rate | (m3/hr) |
| Wc | water cost | (EGP) |