D. Tech. Engineering: Mechanical. / Discusses the main objective of the study is to carry out a theoretical and experimental study of a water-to-water CO2 heat pump system and improve its performance by optimizing its working parameters and conditions. The optimization process will be based on South African conditions.Specific objectives to meet the required goal are: 1. Carry out the installation and experimental analysis of a water to water CO2 heat pump system.2. Evaluate the reliability of the system using statistical means through regression analysis and create relationship models between the input and output parameters of the system.3. Execute a thermodynamic analysis of the selected system and evaluate the most important factors that affect its energy efficiency, then identify and evaluate possible system improvements and optimum operating conditions. 4. Compare available heat pump related kinematic and mathematical models and evaluate the best model to describe the operations in the system under local operating conditions. Suggest further improvements to the models and evaluate these too.5. Perform computer modelling and simulations to analyse the CO2 heat pump system,supplement the measurements from the test rig and compare the results.