Fin heat transfer modeling and its impact predictions of efficiency and condensation in gas-fired boilers

In conventional and high-efficiency boilers it is important to understand where water from the products of combustion may condense onto the heat exchanger surface. The usual fin modeling approach is inadequate because ir predicts no circumferential preference for condensation, whereas spatial effects have been observed. Two alternative approaches for modeling fin hear transfer are explored: one method is based on a generalization of observed ti-ena's in local convective heat transfer coefficients, and the other on a semiempirically motivated variation in convective flow temperature. Temperature distribution and fin efficiency predictions are compared to the conventional fin modeling approach. The alternative fin heat transfer models described in this study both predict more extensive condensation on the portion of the fin within the wake of the robe. Furthermore, both models predict fin efficiencies below those obtained using an assumption of constant hear transfer coefficient and convective temperature.