Heat Transfer Experiments of Ethylene Glycol-Water Mixture in Multi-Port Serpentine Meso-Channel Heat Exchanger Slab

Abstract

In past few years, narrow diameter flow passages (≤3 mm) have attracted huge research attentions due to their several advantageous features over conventional tubes (≥6 mm) especially from the view points of higher heat transfer, lesser weight, and smaller device size. Several classifications of narrow channels, based on sizes, are proposed in the open literature from mini to meso and micro (3 mm to 100 μm). The meso- and micro-channels have not yet entered into the HVAC and automotive heat exchanger industries to the expected potentials to take the above-mentioned advantages. The reasons may be the limited availability of experimental data on pressure drop and heat transfer and the lack of consolidated design correlations as compared to what is established for compact heat exchangers. While a number of studies available on standalone single straight channels, works on multi-channel slab similar to those used as typical thermal heat exchanger core elements are inadequate, especially the research on multichannel serpentine slab are limited in the open literature. The 50% ethylene glycol and water mixture is widely used in heat exchanger industry as a heat transfer fluid. Studies of pressure drop and heat transfer on this commercially important fluid using narrow tube multi-channel slab is scarce and the availability of experimental data is rare in the open literature. Conducting research on various shapes of meso- and micro-channel heat exchanger cores using a variety working fluids are a definite needs as recommended and consistently urged in ongoing research publications in this promising area. Under present long-term project, an automated dynamic single-phase experimental infrastructure has been developed to carryout the fluid flow and heat transfer research in meso- and micro-channel test specimens and prototype microchannel heat exchanger using a variety of working fluids in air-to-liquid crossflow orientation. In the series, experiments have been conducted on 50% ethylene glycol and water solution in a serpentine meso-channel slab having 68 individual channels of 1 mm hydraulic diameter to obtain the heat transfer data and the general pressure drop nature of the test fluid. Current paper presents the heat transfer characteristics of ethylene glycol-water mixture and the Reynolds number effects on pressure drop, heat transfer rate, test specimen NTU and effectiveness, overall thermal resistance, and the Nusselt number.