Simple Analytical Model for Counter-flow Rotary Heat Exchangers

A simple analytical model is presented for counter-flow rotary heat exchangers. The model is based on an approximate analytical solution of simplified governing equations, which are valid for arbitrary rotation speeds and flow rate ratios. A resulting effectiveness equation was compared with a set of tabular data from the literature and with the results from a numerical model. The results showed that the model was accurate for small and moderate NTU values, giving a maximum relative error of ca. 4~9% for NTU = 5 and 3~7% for NTU = 3. The error increased with increasing NTU values as the model could not predict strong nonlinear temperature profiles in cases of large NTUs. The model was applied to a plastic rotary heat exchanger and it was predicted that a plastic heat exchanger would yield the same effectiveness as a metal heat exchanger by increasing its rotation speed.