Which of the following methods would significantly improve the energy efficiency of an air conditioning or refrigeration system?

Lowering the condensing temperature and raising the evaporating temperature enhances the overall efficiency of an air conditioning or refrigeration system. This approach maximizes the system's capacity to absorb heat from the environment it is cooling while minimizing the amount of energy required to reject heat.

When the condensing temperature is lowered, the refrigerant requires less energy to condense back into liquid form, making the process more efficient. Conversely, raising the evaporating temperature allows the refrigerant to absorb more heat from the environment, increasing the cooling capacity of the system. Together, these changes result in a more favorable pressure and temperature difference, leading to reduced energy consumption and improved operational efficiency.

In contrast, other options either do not provide significant improvements or could worsen the system's performance. For example, lowering the evaporating temperature and raising the condensing temperature (as mentioned in one of the other choices) would create a less efficient cycle, increasing energy consumption rather than decreasing it. Decreasing the refrigerant charge could lead to reduced cooling efficiency and potential system malfunction. While increasing airflow across the condenser can help disperse heat more effectively, it may not address the core thermodynamic principles that fundamentally enhance energy efficiency.