A heat pump dryer can be used to dry papayas, here are some suggested temperature settings:

1. In the initial stage, set the temperature at 40-50 degrees Celsius. This helps to preserve the quality of the papaya, while also preventing over drying.
2. Then, gradually increase the temperature to 60-65 degrees Celsius. This speeds up the drying process and ensures that the papaya is completely dry.
3. Finally, lower the temperature to 30-40 degrees Celsius so that the papaya cools down. This prevents the papaya from going bad during storage.

It is important to note that heat pump dryer temperature settings may vary between different makes and models. Therefore, it is best to refer to the instructions in the instruction manual or consult the technical support of the manufacturer to ensure the best drying results and the safety of the equipment.