scholarly journals Influence of non-steady transient heat flux on flow boiling heat transfer and pressure drop in horizontal pipes

2022 ◽  
Vol 182 ◽  
pp. 121927
Author(s):  
W.J. Van den Bergh ◽  
J. Dirker ◽  
C.N. Markides ◽  
J.P. Meyer
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Horizontal Pipes ◽  
Flow Boiling Heat Transfer ◽  
Transient Heat Flux

Effect of Inlet Restriction on Flow Boiling Heat Transfer in a Horizontal Microtube

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
YanFeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Mass Fluxes ◽  
Flow Boiling Heat Transfer ◽  
Low Mass

Flow boiling heat transfer in a horizontal microtube with inlet restriction (orifice) under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two microtubes with smaller diameters are assembled at the inlet of main microtube to achieve the restriction ratios of 50% and 20%. The experimental measurement is carried out at mass fluxes ranging from 160 to 870 kg/m2·s, heat fluxes varying from 6 to 170 kW/m2, inlet temperatures of 23 and 35 °C, and saturation pressures of 10 and 45 kPa. The effects of the orifices on two-phase pressure drop, critical heat flux (CHF), and flow boiling heat transfer coefficient are studied. The results show that the pressure drop caused by the orifice takes a considerable portion in the total pressure drop at low mass fluxes. This ratio decreases as the vapor quality or mass flux increases. The difference of normal critical heat flux in the microtubes with different orifice sizes is negligible. In the aspect of flow boiling heat transfer, the orifice is able to enhance the heat transfer at low mass flux and high saturation pressure, which indicates the contribution of orifice in the nucleate boiling dominated regime. However, the effect of orifice on flow boiling heat transfer is negligible in the forced convective boiling dominated regime.

scholarly journals Flow boiling heat transfer capabilities of R134a low GWP substitutes inside a 4 mm id horizontal smooth tube: R600a and R152a

2020 ◽  
Author(s):  
Giovanni A. Longo ◽  
Simone Mancin ◽  
Giulia Righetti ◽  
Claudio Zilio
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Internal Diameter ◽  
Critical Comparison ◽  
Flow Boiling Heat Transfer ◽  
Experimental Values

AbstractR134a was recognized as probably one of the most important refrigerants of the two past decades. Among the proposed alternative fluids, there are certainly isobutane (R600a) and R152a. This article presents about 200 new heat transfer coefficient and pressure drop data obtained during flow boiling of R152a and R600a inside a smooth copper tube having an internal diameter of 4 mm. Three saturation temperatures were considered for each refrigerant, from 5 °C to 20 °C. Furthermore, for each temperature studied, the heat flux was varied between 15 and 30 kW m−2 and the refrigerant mass flux from 100 to 400 kg m−2 s−1. After presenting the new data, a critical comparison was proposed between the performance of these refrigerants and R134a. Finally, some classic correlations available in the literature have been implemented. The deviations between the calculated and experimental values were reported and commented.

Flow Boiling of R134a and R245fa in a 1.1 mm Diameter Tube

2013 ◽  
Author(s):  
Emily A. Pike-Wilson ◽  
Mohamed M. Mahmoud ◽  
Tassos G. Karayiannis
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Experimental Conditions ◽  
Local Flow ◽  
Flow Boiling Heat Transfer ◽  
Vapour Quality

New refrigerants are required for cooling systems due to the fact that refrigerants like R134a are about to be phased out. This paper presents a comparison between the flow boiling heat transfer and pressure drop results of refrigerants R245fa and R134a. The experiments with R245fa were conducted in a vertical cold drawn stainless steel tube with an inner diameter of 1.1 mm and heated length of 150 mm. Experimental conditions include: mass flux range 100–400 kg/m2s, heat flux range 10–60 kW/m2, pressures of 8 and 10 bar and 1.9 and 2.5 bar for R134a and R245fa corresponding to saturated temperatures 31 °C and 39 °C and exit vapour quality range 0–0.95. The data for R134a were obtained earlier using the same experimental facility at the same experimental conditions and with the same test tube. The results demonstrated that refrigerant properties have a significant effect on heat transfer and pressure drop. The pressure drop of R245fa is higher by up to 300% compared to that of R134a at similar conditions. In addition, the effect of mass flux and heat flux on the local flow boiling heat transfer coefficient was different. Heat transfer coefficients of R245fa showed a greater dependence on vapour quality. The agreement with past heat transfer correlations is better with R134a than with R245fa.

Study on Subcooled-Forced Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture

1999 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Manabu Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Liquid Layer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Superheated Liquid ◽  
Flow Boiling Heat Transfer

Abstract The effect of solid particle introduction on subcooled-forced flow boiling heat transfer and a critical heat flux was examined experimentally. In the experiment, glass beads of 0.6 mm diameter were mixed in subcooled water. Experiments were conducted in a range of the subcooling of 40 K, a velocity of 0.17–6.7 m/s, a volumetric particle ratio of 0–17%. When particles were introduced, the growth of a superheated liquid layer near a heat trasnsfer surface seemed to be suppressed and the onset of nucleate boiling was delayed. The particles promoted the condensation of bubbles on the heat transfer surface, which shifted the initiation of a net vapor generation to a high heat flux region. Boiling heat trasnfer was augmented by the particle introduction. The suppression of the growth of the superheated liquid layer and the promotion of bubble condensation and dissipation by the particles seemed to contribute that heat transfer augmentation. The wall superheat at the critical heat flux was elevated by the particle introduction and the critical heat flux itself was also enhanced. However, the degree of the critical heat flux improvement was not drastic.

scholarly journals Characteristics of Flow Boiling Heat Transfer and Critical Heat Flux in a Vertical Tube with a Wire Coil.

2001 ◽  
Vol 67 (653) ◽  
pp. 128-134
Author(s):  
Keishi TAKESHIMA ◽  
Terushige FUJII ◽  
Nobuyuki tAKENAKA ◽  
Hitoshi ASANO ◽  
Takamitsu KONDO
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Flow Boiling Heat Transfer ◽  
Wire Coil

Flow Boiling Heat Transfer, Pressure Drop, and Flow Pattern for CO2 in a 3.5mm Horizontal Smooth Tube

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Chang Yong Park ◽  
Pega Hrnjak
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer

Abstract C O 2 flow boiling heat transfer coefficients and pressure drop in a 3.5mm horizontal smooth tube are presented. Also, flow patterns were visualized and studied at adiabatic conditions in a 3mm glass tube located immediately after a heat transfer section. Heat was applied by a secondary fluid through two brass half cylinders to the test section tubes. This research was performed at evaporation temperatures of −15°C and −30°C, mass fluxes of 200kg∕m2s and 400kg∕m2s, and heat flux from 5kW∕m2 to 15kW∕m2 for vapor qualities ranging from 0.1 to 0.8. The CO2 heat transfer coefficients indicated the nucleate boiling dominant heat transfer characteristics such as the strong dependence on heat fluxes at a mass flux of 200kg∕m2s. However, enhanced convective boiling contribution was observed at 400kg∕m2s. Surface conditions for two different tubes were investigated with a profilometer, atomic force microscope, and scanning electron microscope images, and their possible effects on heat transfer are discussed. Pressure drop, measured at adiabatic conditions, increased with the increase of mass flux and quality, and with the decrease of evaporation temperature. The measured heat transfer coefficients and pressure drop were compared with general correlations. Some of these correlations showed relatively good agreements with measured values. Visualized flow patterns were compared with two flow pattern maps and the comparison showed that the flow pattern maps need improvement in the transition regions from intermittent to annular flow.

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