Which of the following factors can affect the performance of a refrigeration system?

The performance of a refrigeration system is indeed influenced by ambient temperature. Ambient temperature refers to the surrounding environmental temperature in which the system operates. When the ambient temperature is high, the refrigeration system has to work harder to remove heat from the refrigerated space, as it is trying to maintain a lower temperature than that of the environment. This can lead to increased energy consumption and potentially strain on system components, decreasing efficiency and overall performance. Proper design and placement of the refrigeration system can mitigate some of these challenges by optimizing the exposure to temperature variations.

The other factors, while they might also influence the overall effectiveness of a refrigeration unit, do not directly relate to the immediate conditions under which the system operates in the way that ambient temperature does. For instance, refrigerant efficiency pertains to the effectiveness of the refrigerant used, compressor size relates to the capacity of the system to handle cooling loads, and the type of insulation impacts heat retention and loss, but the ambient temperature presents an ongoing challenge that the system must continually manage.