Optimize Heat Exchanger Design to Save Money

Heat exchangers are valuable equipment for wide variety of industrial applications right from oil industry, air conditioning and refrigeration to power generation, food processing and many others. These thermal equipments are often designed to deliver better efficiency in terms of heat transfer rate with minimal manufacturing, installation and operating costs. As such, engineers look for a heat exchanger design that is optimized to perform well in the specified conditions. The term heat exchanger is generally used for equipment that undergoes a heat transfer process by using service fluids. Depending on the purpose i.e. heating or cooling, heat exchangers are also known as coolers, heaters, evaporators, condensers or radiator.

The thermal-hydrodynamic design of these heat exchangers is usually performed through numerical techniques and the step-by-step technique is one the widely popular methods. The popularity of this technique within design engineers is primarily because it helps them achieve the optimization goals, specifically for shell and tube heat exchanger as compared to conservative design attained by Kern or Bell-Delaware techniques. The step-by-step technique is also successful in designing air cooled heat exchangers.

Surface condenser (water cooled shell and tube heat exchanger) Source: Wikipedia

The concept behind this step-by-step technique is to divide the heat exchanger into smaller increments and each increment is considered as a separate heat exchanger. The exit operating conditions for one increment like temperature, pressure and vapor quality are considered as inlet conditions for the next increment. The same procedure is followed until the final exit operating conditions are achieved. With this method, accumulating error is less as compared to other methods.

Following are the two major advantages of step-by-step technique for heat exchanger design:

1. The nonlinear fluid temperature along the flow path is avoided and as such the effect of potential temperature difference can be eliminated

2. The method considers the change in physical and thermal properties with changing temperature, which is beneficial to finalize the heat exchanger design that consists of fluids undergoing large temperature differences at both ends.

The two major benefits mentioned above plays an important role in optimizing the heat exchanger design since the final surface area required for optimum heat transfer can be ascertained. This directly helps in minimizing the overall cost of manufacturing the thermal equipment.

The concept behind this step-by-step technique is to divide the heat exchanger into smaller increments and each increment is considered as a separate heat exchanger. The exit operating conditions for one increment like temperature, pressure and vapor quality are considered as inlet conditions for the next increment. The same procedure is followed until the final exit operating conditions are achieved. With this method, accumulating error is less as compared to other methods.

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