Conferences (International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics)http://hdl.handle.net/2263/332012024-03-28T21:05:41Z2024-03-28T21:05:41ZNumerical investigation of condensation inside an inclined smooth tubeNoori, Rahim Abadi S.M.A.Meyer, Josua P.Dirker, Jacohttp://hdl.handle.net/2263/624782022-04-08T22:47:14Z2017-01-01T00:00:00ZNumerical investigation of condensation inside an inclined smooth tube
Noori, Rahim Abadi S.M.A.; Meyer, Josua P.; Dirker, Jaco
In this paper the effect of inclination angle on the
condensation heat transfer coefficient, pressure drop and flow
regime inside a smooth tube was investigated numerically. The
working fluid was R134a at a saturation temperature of 40°C.
The Volume of Fluid (VOF) multiphase flow formulation was
utilized to solve the governing equations. Simulations were
conducted at a heat flux of 5 kW/m2, at mass fluxes of 100 –
600 kg/m2.s, and the inclination angles were varied from
vertical downward to vertical upward. The simulation results
were successfully validated with the experimental data. The
results showed that an optimum downward inclination angle of
between -30° and -15° exists, for the heat transfer coefficients.
It was also found that the effect of inclination angle on the
pressure drop and void fraction became negligible at high mass
fluxes and vapour qualities.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
2017-01-01T00:00:00ZExperimental studies on steam condensation in horizontal and vertical microtubesSadaghiani, A.K.Motezakker, A.Kosar, A.http://hdl.handle.net/2263/624772022-04-08T22:47:14Z2017-01-01T00:00:00ZExperimental studies on steam condensation in horizontal and vertical microtubes
Sadaghiani, A.K.; Motezakker, A.; Kosar, A.
Microchannels have increasingly been used in the industry to miniaturize heat transfer equipment, improve energy efficiency, and minimize heat transfer fluid inventory. A fundamental understanding about condensation in microscale will yield far reaching benefits for the automotive and HVAC&R industries. In this study, the effect of microchannel diameter and orientation on condensation heat transfer is investigated. Steam is used as the working fluid, microtubes with inner diameters of 500 and 900 μm inner diameters, in horizontal and vertical orientations were used. The working fluid was pumped into the vapor generator from the reservoir after passing through a micro- filter. Saturated vapor was generated via electrical heating and was then led into the condensing section. Flow condensation occurred in the microtubes. The condensate leaving from the outlet of the condensing section was cooled in the cooler before flowing through the micro flow-meter. It was found that the condensation heat transfer coefficient increased with mass flux, heat flux, and vapor quality, while pressure drop increased with the mass flux and vapor quality. At low mass fluxes, it was found that the channel orientation had a considerable effect on heat transfer coefficient, while this difference diminished as mass flux increased. As mass velocity increased, differences in heat transfer coefficient are reduced.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
2017-01-01T00:00:00ZAnalysis of the energetics and stability of liquid droplets on textured surfaces with square micropillarsRahman, M.A.Goswami, A.http://hdl.handle.net/2263/624762022-04-08T22:47:14Z2017-01-01T00:00:00ZAnalysis of the energetics and stability of liquid droplets on textured surfaces with square micropillars
Rahman, M.A.; Goswami, A.
Numerous studies have established that roughening a hydrophobic surface can induce superhydrophobic properties on that surface. The suspended wetting state (Cassie-Baxter state) on a microtextured surface tends to collapse to a wetted state (Wenzel state) due to external stimulations. Multiple metastable Cassie-Baxter wetting state, separated by an energy barrier from Wenzel state, may also exist. In this study, 3D droplet models are developed to numerically investigate the shapes and energies of CB droplets residing on rough surfaces patterned with square pillars. A normalized form of droplet energy is used to compare the relative stabilities of metastable states. The sequence of stable droplet configurations with increasing droplet volume is analyzed for different isotropic wetting cases. Analysis reveals that wetting configuration with the most number of pillars at the drop-base suspends the biggest with higher stability compared to other configurations . In order to explore droplet energetics on distinct substrates, the pillar width and spacing are varied in simulations. For the the same drop-base area, the substrate that gives the least value of solid-fraction at the drop-base, characterized by its pillar width and spacing, suspends the biggest droplet as the most stable CB droplet compared to others.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
2017-01-01T00:00:00ZA study on heat transfer characteristics of fibonacci spiral microchannel heat sinkHsu, Cheng-HsingJiang, Jui-ChinDang, Hung-SonNguyen, Thi-Anh-TuyetChang, Ching-Chuanhttp://hdl.handle.net/2263/624732022-04-08T22:47:14Z2017-01-01T00:00:00ZA study on heat transfer characteristics of fibonacci spiral microchannel heat sink
Hsu, Cheng-Hsing; Jiang, Jui-Chin; Dang, Hung-Son; Nguyen, Thi-Anh-Tuyet; Chang, Ching-Chuan
A study on a Fibonacci spiral microchannel heat sink was carried out in the present work to predict thermal resistance and pressure drop of the model. The Computational Fluid Dynamics software (ANSYS Fluent 14) and Taguchi method were used to simulate and optimize the parameters of the Fibonacci spiral microchannel heat sinks. In addition, the Minitab 17 software was also used to analyze the simulated data. The result shows that the optimal design parameters can give good agreement of the overall thermal resistance and pressure drop (with the values 0.715/Wm², 15.53kPa, respectively.) were achieved for the design of the Fibonacci spiral micro-channel heat sink.
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
2017-01-01T00:00:00Z