Experimental investigation of dryout of propane in uniformly heated single vertical mini-channels

Abstract

a b s t r a c tThis article presents dryout results of propane in single vertical circular minichannels made of stainless steel with internal diameters of 1.70 mm and 1.224 mm. The heat flux is increased in steps up to occurrence of dryout. The effects of different parameters such as mass flux, saturation temperature, vapour quality and internal diameter on the dryout are investigated. The results show that the dryout heat flux increases with the increase in mass velocity, with the decrease of vapour quality and with the increase of internal diameter. Almost no effect of saturation temperature on dryout heat flux is observed. Generalised CHF correlations developed for macro and micro scale from the literature are also compared with the experimental results.

Dryout characteristics of natural and synthetic refrigerants in single vertical mini-channels

“…They reported, that the critical heat flux increases with increasing mass flux while no effect of varying saturation temperature was observed. Based on their experimental data they proposed a correlation for prediction of CHF, which is also a modified version of Katto-Ohno correlation [7] and gave good predictions as confirmed by other authors [10,3]. Ali and Palm [10] reported on dryout tests with R134a in vertical, single stainless steel tubes (1.224 and 1.70 mm inside diameter and 220 mm heated length) at two operating pressures corresponding to 27 and 32°C saturation temperatures at mass flux of 50-600 kg/m 2 s. They noticed that dryout heat flux increases with increasing mass flux, decreases with reducing tube diameter while remains almost unaffected with varying operating pressure.…”

“…It should also be mentioned that in almost all cases heat transfer coefficient was strongly influenced by heat flux and system pressure whereas vapor quality and mass flux effects were almost insignificant. The details for parametric effects on heat transfer can be seen in previous publications [4,3].…”

“…Flow boiling in these compact channels offers many potential advantages like, ability to cope with high heating/cooling demands (enhanced surface area per unit volume of the fluid), less fluid inventory, uniform surface temperature, compactness in size, reduced material and overall weight, etc. Furthermore as heat transfer coefficient (HTC) increases with increase in applied heat flux local hot spots can also be managed/tolerated [2][3][4]. However, with small channels the channel layout has to be done with care to avoid pressure drop increase compared to larger scale channels.…”

“…Maqbool et al [3] conducted dryout experiments with propane in resistively heated vertical tubes (1.7 and 1.224 mm inside diameter and 245 mm heated length) with 100-500 kg/m 2 s mass flux and for three saturation temperatures (23, 33 and 43°C). They observed similar parametric effects like Ali and Palm [10] (both used the same experimental setup).…”

“…This study is based on a large database collected from recent and previous studies conducted at Royal Institute of Technology KTH, Sweden [9,3,4,11,12]. The combined database involves seven refrigerants, four test sections and had 72 data-points.…”