Shell and Tube Heat Exchanger Efficiency

- Jul 08, 2018-

Why counter flow heat exchangers are more efficient
It is common knowledge amongst heat exchanger designers that a counter flow heat exchanger installation is more efficient than the parallel flow alternative, but for others it may be somewhat mysterious. In this article, we will explain what countercurrent is and why it is more efficient than parallel streaming.
What is counter flow?
First, we need to understand that the difference between counter flow and parallel flow. As a brief description; the term refers to the relationship between the flow directions of the hot fluid and the cold fluid. By parallel flow, the fluid travels through the heat exchanger in the same direction, where as a counter flow installation will have the fluids flowing against each other in opposite directions.

                                                 Counter Flow Heat Exchanger


The figure above shows a shell and tube heat exchanger. In a counter flow setting, the fluid travels in the opposite direction along the heat exchanger. In the chart above, the cold fluid highlighted in blue travels from right to left, while the warm fluid (shown in red and amber) travels left to right. This distributes heat more evenly across the heat exchanger and allows for maximum efficiency. In theory, the cold fluid can exit the heat exchanger at a temperature above the temperature of the hot fluid outlet, but in practice this is difficult to achieve.

                                                     Parallel Flow Heat Exchanger


In a parallel flow setup, both the hot fluid and cold fluids are travelling in the same direction as each other. On the diagram above they both flow from right to left. This will still cool the hot fluid down by a considerable amount but is not as efficient as the counter flow system.

The benefit
The efficiency obtained with a counter flow system depends on several factors, including flow rate and temperature (these factors affect their own efficiency), but it will be most noticeable in a larger cooler.
Using one of our smaller coolers, such as 2542 (5" diameter x 600mm long), the performance may be only 1% or 2%, but with a larger cooler, such as our 2862 model (8" diameter x 1727mm long) Performance can be increased by 10% when using a counter flow installation At Thermex, we always design a cooler with a counterflow configuration, so it is important to install the heat exchanger correctly.