Quantifying errors in coupled ε-NTU method and development of divisional ε-NTU method for reliable and accurate design of energy exchangers

In coupled energy exchangers, where heat and mass transfer rates are interdependent due to the phase change energy associated with moisture transfer, the classical ϵ-NTU method can lead to significant errors in estimating performance. The coupled ϵ-NTU method can be used to mitigate these errors and uses modified non-dimensional parameters called the effective heat and mass capacity ratios. While more accurate than the classical ϵ-NTU method, it still has significant errors in estimating performance under certain operating conditions. The coupled ϵ-NTU method is compared to a numerical model to evaluate the performance of a liquid-to-air membrane energy exchanger (LAMEE). The operating conditions for which the coupled ϵ-NTU method is reliable are identified to help designers make informed choices. It was also found that the errors in estimating the total energy transfer are within 5 % when Cr* (specific heat capacity ratio of solution-to-air) > 4; however, when Cr* is less than 1, the errors in the coupled ϵ-NTU method are high. To overcome the limitations of the coupled method, the divisional ϵ-NTU method is proposed. It relies solely on algebraic equations and accurately predicts sensible and latent heat transfer with an error of less than 5 % under all operating conditions compared.