Abstarct: Reciprocating compressors find wide variety applications in industrial and domestic purposes such as power plants, refineries, refrigeration systems and CNG Fuel stations. These compressors use a huge amount of energy, thus reciprocating simulation is crucial for not only for the reduction of wasting energy but also the reduction of maintenance costs. According to previous research, one and zero dimensional (thermodynamic) simulation is accurate and economical method for reciprocating compressor modelling. Reciprocating compressors with accessory devices were simulated in this thesis. In the present study, thermodynamic simulation (zero-dimensional) is used to investigate reciprocating natural gas compressor with suction and discharge chambers. To this end, three control volumes including compressor cylinder, suction, and discharge chambers with equivalent mass and energy equations are investigated. Natural gas as a working fluid was simulated baxsed on ideal and real gas model. Natural gas thermodynamic properties were calculated with the AGA8 equation of state. Results show that single-stage reciprocating compressor power consumption for real gas model was predicted more than ideal gas model. But power consumption per unit mass flow for the real gas model is lower than the ideal gas model. Computer simulation for two-stage natural gas reciprocating compressor shows that intermediate pressure for real gas model is lower than the ideal gas model. Moreover, power consumption per unit mass flow for the real gas model is lower than the ideal gas model. Double-acting reciprocating compressor study shows that entropy generation per unit mass flow is much lower than that single-acting reciprocating compressor. Finally, single stage reciprocating compressor with valves faults were investigated baxsed on ideal gas model. Results show that, suction valve fault leads to premature opening of the suction valve and a delay in the opening of the discharge valve. But discharge valve fault leads to a delay in the suction valve opening angle premature opening of the discharge valve. Furthermore, results show that suction and discharge temperatures increase for suction valve fault. In addition, with discharge valve fault, discharge chamber temperature increases but its value is lower than the suction valve fault. As a results, suction and discharge temperatures monitoring is an effective method for compressor valve fault diagnosis.