Which type of exchanger incorporates one or more coils of tubing inside a shell?

The correct answer is helical exchangers. A helical heat exchanger is designed with one or more coils of tubing inside a shell, which allows for effective heat transfer between two fluids. The helical design promotes a continuous flow path, enhancing turbulence and improving the overall heat transfer efficiency. The coils are arranged in a helical pattern, which maximizes the surface area for heat exchange and minimizes pressure drop.

In contrast, spiral heat exchangers consist of two spirally coiled channels that allow for counterflow heat exchange but do not typically use one or more coils of tubing in a single shell. Plate heat exchangers utilize thin plates stacked together to create channels for fluid flow, making them distinct in design and operation from helical exchangers. Double tube heat exchangers consist of one tube inside another, where one fluid flows through the inner tube and another through the outer space, without the helical arrangement that characterizes the correct answer.

Understanding these differences highlights why helical heat exchangers are specifically identified by their use of coiled tubing within a shell configuration, making them effective for various applications in thermal management systems.