What is the term used for a system that utilizes pumps and fans for heat transfer?

The term for a system that utilizes pumps and fans for heat transfer is an active system. In the context of refrigeration and heat transfer, an active system relies on mechanical means, such as pumps and fans, to enhance the movement of heat. This mechanical intervention allows for more efficient and controlled heat transfer compared to systems that depend solely on natural processes.

Active systems are designed to facilitate the circulation of fluids (in the case of refrigerants) or air to achieve desired temperature changes, making them essential in refrigeration, heating, and ventilation applications. The use of pumps helps in moving refrigerants through the system while fans assist in the distribution of air or fluids, directly impacting performance and efficiency in thermal management.

In contrast, passive systems do not incorporate mechanical devices for heat transfer; instead, they rely on natural convection and conduction processes. Natural systems also function solely on natural phenomena without mechanical assistance. Hybrid systems, as the name suggests, combine elements of both active and passive systems but are not defined primarily by the use of pumps and fans. Thus, the defining feature of active systems is the use of pumps and fans, making it the correct choice.