Flow boiling heat transfer characteristics of carbon dioxide in a horizontal tube

Carbon dioxide local heat transfer coefficients during flow boiling in a horizontal circular smooth tube

“…For all plots it results q % 10 kW/m 2 . Very similar trends have been observed experimentally by Yun et al [11] and Oh et al [16]: they explain their experimental results in terms of partial dryout of liquid film at very low vapor quality (0.3 Ä 0.4) and dominance of nucleate boiling. Taking into account that the heat transfer process depends on the liquid and vapor phase distributions, an accurate analysis of the flow regimes corresponding to the experimental points is necessary to understand the experimental values and trends.…”

“…Besides, compared to the flow pattern map of Cheng et al [22,23], in our experiments the transition from slug to stratified-wavy/annular flow regime seems to take place at slightly higher values of vapor quality and the transition from stratified-wavy and annular flow regime seems to occur for slightly higher mass flux. [16].…”

“…Regarding the absolute values, a good agreement has been observed in most cases, even if some discrepancies have been found; for example, differently from our study, Yun et al [11] observed: an influence of the heat flux on heat transfer coefficients only for low vapor quality (up to 0.3 Ä 0.4); the heat transfer coefficients increasing with the rise of mass flux for vapor qualities above 0.5 and the decrease with the increase of evaporating temperature at high vapor quality. About the work by Oh et al [16], even if a limited range of vapor qualities was investigated, important differences in the absolute values can be noticed for G = 200 kg/m 2 s, t sat = À7.8°C and q = 10.1 kW/m 2 probably due to the slightly greater inner diameter. From the comparison with Cho and Kim [15] and Yoon et al [17], it can be observed that the heat transfer coefficients presented in this work are greater even if we used an inner diameter lower.…”

“…Besides it seems that the interpretation of the trends of experimental points is still opened. In particular, the influence of mass flux, evaporating temperature, heat flux and vapor quality on the heat transfer coefficients is not completely cleared and some contradictions appears in the data as it is evident comparing some works [9][10][11][12][13][14][15][16][17].…”

Pressure Drop and Boiling Heat Transfer Characteristics of R410A in Macro-Scale and Mini-Scale Channels

“…When the mass flux increases, the flow velocity increases, which raises both of two components. This effect of mass flux on the two-phase pressure drop was well observed in various studies including the single-mini/conventional-channel and multi-port tubes [4,8,[15][16][17][18][19].…”