Heat exchangers serve to transfer energy from a hot stream to a cold stream as efficiently as possible. Efficiency is measured here as the heat transfer area required. The larger the heat transfer area required, the less efficient is the heat exchanger. Currently, there are two main configurations of heat exchangers: the counter-current and co-current heat exchangers.
In counter-current heat exchangers, the hot and cold fluid flow in opposite directions in the heat exchanger. This is in contrast to the co-current heat exchanger where the hot and cold fluids flow in the same direction along the length of the heat exchanger.
Comparing the co-current and counter-current heat exchangers, one would find that the temperature difference between the hot and cold fluid in the counter-current heat exchanger is maintained at a larger value compared to the co-current heat exchanger for a large part of the heat exchanger’s length. This could enable a higher efficiency for heat transfer, and thus a smaller heat transfer area. In the case of the co-current heat exchanger, the temperature difference between the hot and cold fluid decreases along the length of the heat exchanger from the inlet to the outlet, which resulted in a decrease in heat transfer efficiency and a larger heat transfer area.
Another feature of the counter-current heat exchanger is that the outlet temperature of the cold fluid could be higher than that of the hot fluid. This is not possible with the co-current heat exchanger.
Collectively, the counter-current heat exchanger is able to maintain a larger temperature difference between the hot and cold fluid along a large part of the heat exchanger compared to the co-current heat exchanger. This enables a higher efficiency for heat transfer and results in a smaller heat transfer area and smaller equipment size. More importantly, the counter-current heat exchanger allows the heating of the cold fluid to a temperature higher than the outlet temperature of the hot fluid, which is a feature absent in the co-current heat exchanger. Overall, the counter-current heat exchanger is more efficient compared to the co-current heat exchanger, and is more widely used in the chemical process industry.
Category: chemical engineering, environmental engineering,
Tags: heat transfer, counter-current, co-current, heat exchanger, heat transfer area, efficiency,
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