Flow boiling in horizontal flattened tubes: Part II – Flow boiling heat transfer results and model

A numerical study of condensation heat transfer and pressure drop in horizontal round and flattened minichannels

“…Quibén et al [13,14] [15] experimentally studied saturated flow boiling and critical heat flux (CHF) in small flattened tubes with an equivalent diameter of 2.2 mm using R134a and R245fa at T sat =304.15 K. For mass fluxes higher than 200 kg/m 2 s, similar heat transfer coefficients were found for flattened and round tubes. The heat transfer correlation for round tubes could predict the data of flattened tubes well with a mean absolute error lower than 20%.…”

Thermal Energy Processes in Direct Steam Generation Solar Systems: Boiling, Condensation and Energy Storage – A Review

“…They assessed the validity of existing two-phase heat transfer and pressure drop correlations for a range of local temperature and pressure measurements obtained for DSG in a PTC test rig (DISS facility in Almeria, Spain) by Lobón et al (2014) The facility consists of 13 parabolictrough collectors connected in series, with a total length of 700 m where the collector tubes have an inner diameter of 25 mm. The tested correlations for heat transfer were those of Gungor and Winterton (1986), Shah (1982), and Wojtan et al (2005b), whereas for the pressure drop the Lockhart and Martinelli (1949), Grönnerud (1972), and Quibén et al (2009) correlations were used. The temperature and pressure gradient profiles predicted by the correlations had an RMSE of <2.10% and <0.57%, respectively, when compared with the measurements.…”

Simultaneous Effects of Flattening Tube and Adding Nanoparticles on Boiling Heat Transfer

“…To predict the heat transfer coefficient in flattened tubes, Kim et al [16] and Quibén et al [19] proposed new correlations based on their experimental data. The reported geometrical parameters and the used refrigerant in [13,16] are different from the ones covered in this study.…”

“…This specific tube profile yields lower hydraulic diameter according to its lower cross-sectional area to internal perimeter ratio. There are some studies in the literature that reported the privileges of flattened channels for the sake of heat transfer enhancement [16][17][18][19][20][21]. Wilson et al [17] carried out an experimental investigation on condensation heat transfer of R134a and R410a inside different flattened tubes.…”

“…Enhancement of heat transfer and decrease in refrigerant charge were observed while the tube profile became flat. Quiben et al [19] performed a comprehensive investigation on flow boiling heat transfer for four flattened copper channels with two different heights of 2 and 3 mm made from primary round tubes with 8 and 13 mm inner diameter. R22 and R410a were selected as working fluids.…”