Question

When is a heat exchanger classified as being compact? Do you think a double- pipe heat exchanger can be classified as a compact heat exchanger?

Short answer

Answer: No, a double-pipe heat exchanger is not typically classified as a compact heat exchanger due to its simple design and lower A/V ratio compared to the compact heat exchanger threshold value.

Step-by-step solution

Understand Compact Heat Exchangers

A heat exchanger is considered compact if it has a large heat transfer surface area (A) per unit volume (V) of the heat exchanger. Typically, a heat exchanger is defined as compact if its A/V ratio is greater than or equal to 700 m^2/m^3.

Characteristics of Compact Heat Exchangers

Compact heat exchangers have the following main features: 1. High heat transfer coefficient (h): Compact heat exchangers have high h values due to the large surface area available for heat transfer. 2. Efficient use of space: Due to their size and heat transfer capabilities, compact heat exchangers are used in applications where space is limited, such as automotive, aerospace, and electronics cooling. 3. Complex designs: Compact heat exchangers often have intricate designs to maximize the surface area available for heat transfer, such as finned surfaces or compact plate/frame structures.

Double-Pipe Heat Exchangers

A double-pipe heat exchanger consists of two concentric pipes, with one fluid flowing through the inner pipe and another fluid flowing through the annular space between the inner and outer pipes. The heat exchange occurs between the two fluids across the walls of the pipes.

Determine if a Double-Pipe Heat Exchanger is Compact

To evaluate if a double-pipe heat exchanger can be classified as a compact heat exchanger, we must compare its A/V ratio to the threshold value of 700 m^2/m^3. The surface area available for heat transfer in a double-pipe heat exchanger primarily consists of the outer surface of the inner pipe and the inner surface of the outer pipe. However, generally, double-pipe heat exchangers have a lower A/V ratio due to their relatively simple design and do not have additional features to increase their heat transfer surface area, such as fins or complex geometries. Therefore, a double-pipe heat exchanger most likely cannot be classified as a compact heat exchanger. In conclusion, a double-pipe heat exchanger is not typically classified as a compact heat exchanger due to its simple design and lower A/V ratio compared to the compact heat exchanger threshold value.