Flow boiling of ammonia in vertical small diameter tubes: Two phase frictional pressure drop results and assessment of prediction methods

Abstract

a b s t r a c tTwo phase pressure drops were measured for ammonia at a wide range of test conditions in two sizes of vertical mini channels. The test sections were made of stainless steel (AISI 316) tubes with internal diameter of 1.70 mm and 1.224 mm and a uniformly heated length of 245 mm. Experiments were conducted at three saturation temperatures of 23 C, 33 C and 43 C, the heat flux ranging from 15 to 355 kW/m 2 and the mass flux ranging from 100 to 500 kg/m 2 s. The effect of the heat flux, the mass flux, the vapour quality, the saturation temperature and the internal diameter on the two phase pressure drop are presented in this article. Some generalized two phase pressure drop correlations suggested for macro and micro scale channels are examined by comparing them with our experimental data. None of the examined correlations agreed well with the test data. A new correlation (modified form of Tran et al. correlation) is proposed which is able to predict the experimental data with MAD of 16% and 86% of the data is within AE30% range.

3D numerical investigation on flow boiling characteristics in large length-to-diameter ratio microchannel

“…The reliable of VOF model with Lee phase change model in predicting flow boiling characteristics in microchannel has been validated by a lot of studies. In this paper, the validate calculation of our two phase flow boiling model are performed for a stainless steel circular tube with D h =1.224mm, L=245mm and uniform heat flux by comparing the numerical results with empirical correlation [18][19][20] at G=100kg/(m 2 •s), q=10341~30750W/m 2 , T sat =316.15K and θ=19.3º [21]. As Table 3 shows, the relative errors of ammonia flow boiling pressure drop between present results and empirical correlation provided by Maqbool et al [18] are within 15.9%.…”

“…In this paper, the validate calculation of our two phase flow boiling model are performed for a stainless steel circular tube with D h =1.224mm, L=245mm and uniform heat flux by comparing the numerical results with empirical correlation [18][19][20] at G=100kg/(m 2 •s), q=10341~30750W/m 2 , T sat =316.15K and θ=19.3º [21]. As Table 3 shows, the relative errors of ammonia flow boiling pressure drop between present results and empirical correlation provided by Maqbool et al [18] are within 15.9%. And the relative errors of ammonia flow boiling heat transfer coefficient between the numerical results and empirical correlation proposed by Cooper [19] and recommended by Maqbool et al [20] are within 18.98%.…”