How to solve this problem when Aspen economic evaluation was performed? It said "Temperature difference is insufficient to perform the heat transfer."
Without more information, its not possible to answer your question.
Insufficient temperature difference can impede heat transfer efficiency. Other factors influencing heat transfer include material conductivity, surface area, medium nature, material thickness, insulation presence, fluid velocity, and temperature profile. Considering these factors alongside temperature difference provides a comprehensive understanding of heat transfer efficiency.
In heat transfer, besides a sufficient temperature difference, factors like thermal conductivity, surface area, and distance also affect the rate. Thus, temperature difference alone doesn't determine heat transfer effectiveness.