Browsing by Author "Madan, K."

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    Effect of RIBS/FINS and Aspect Ratio on Flow Boiling Characteristics in Conventional Channels
    (American Society of Mechanical Engineers (ASME), 2024) Madan, K.; Sathyabhama, A.
    In this work, experiments are conducted with conventional rectangular channels of two different aspect ratios (AR =w/d) for the horizontal boiling flow conditions at atmospheric pressure. Distilled water was used as the working substance. The heat transfer coefficients (HTC) were measured for mass fluxes and heat fluxes ranging from 85.94 kg/m2-s to 343.77 kg/m2-s and 10 kW/m2 to 100 kW/m2, respectively, and at inlet subcooled temperatures of 303 K, 313 K, and 323 K. Visualization of the boiling phenomenon was done using a high-speed camera for the two channels under similar conditions. The results show that the AR has a dominant effect on the HTC. At low heat flux values, higher HTC was noticed for the channel of higher AR (AR=1.25) whereas, at high heat flux conditions, the HTC is higher for the channel of lower AR (AR =0.2). With an increase in inlet subcooled temperature, the HTC decreased for both channels due to increased thermal boundary layer thickness and reduced bubble formation. Further, the channel of AR=1.25 with ribs/fins performed better than the smooth channel due to the high bubble nucleation rate. © 2023 by ASME.
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    Modelling of Subcooled Boiling in Corrugated Pipes
    (Springer Science and Business Media Deutschland GmbH, 2023) Madan, K.; Singh, K.; Sathyabhama, A.
    This paper presents a numerical investigation of subcooled flow boiling heat transfer in sinusoidal-corrugated vertical pipes using RPI wall boiling with Eulerian–Eulerian two-phase flow model. Numerical studies are performed for different values of corrugation length and wall heat flux at a constant mass flux, operating pressure and temperature which are representative of steam generation in nuclear reactors. The numerical results are also compared with the smooth/flat pipe in terms of wall temperature, heat transfer, pressure drop and volume fraction (vf) of vapour. The results showed that onset of nucleate boiling is delayed in the case of corrugated pipes as compared to the flat pipe. It is also observed that the vf of vapour at the outlet of flat pipe is higher as compared to corrugated pipes. Overall heat transfer is increased in corrugated pipes due to enhanced mixing which eventually improved convective heat transfer. However, improvement in the heat transfer is at the cost of pressure drop. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.