Effect of micro-fin tube geometry parameters on evaporator material savings

Abstract

A Performance Evaluation Criteria (PEC) analysis is presented that explores the influence of the micro-fin tube geometry on the required material volume. The analysis was done using a local flow boiling model, which can quantify the effect of fin parameters and the tube diameter. The PEC was done while requiring that the compared surfaces satisfy the same heat duty and pressure drop. The following tube parameters and ranges were explored: tube diameter (3 mm ≤ Do ≤ 6 mm), fin base thickness (0.12 mm ≤ tbf ≤ 0.29 mm), helix angle (6° ≤ α ≤ 30°), fin apex angle (11° ≤ β ≤ 22°), total number of fins (43 ≤ nf ≤ 70), and the fin height (0.11 mm ≤ e ≤ 0.3 mm). The tube that provided the smallest material requirements within the examined parameter ranges had: Do = 3 mm, tbf = 0.12 mm, α = 6°, β = 11°, nf = 43, and e = 0.3 mm. In general, small Do and tbf and large nf and e provided the best performance and work to minimize the required material volume to provide a given heat duty and pressure drop. The helix and the fin-tip apex angles were found to have very little influence on the performance for the examined range of parameters and angles associated with the lowest production cost should be chosen.