Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Author: search.filters.author.Nayak, U.V.Subject: search.filters.subject.Heat transfer characteristics

Search Results

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Carbonated aqueous media for quench heat treatment of steels
    (Springer New York LLC barbara.b.bertram@gsk.com, 2016) Nayak, U.V.; Pranesh Rao, K.M.P.; Pai, M.A.; Prabhu, K.N.
    Distilled water and polyalkylene glycol (PAG)-based aqueous quenchants of 5 and 10 vol.% with and without carbonation were prepared and used as heat transfer media during immersion quenching. Cooling curves were recorded during quenching of an inconel 600 cylindrical probe instrumented with multiple thermocouples. It was observed that the vapor stage duration was prolonged and the wetting front ascended uniformly for quenching with carbonated media. The cooling data were analyzed by determining the critical cooling parameters and by estimating the spatially dependent probe/quenchant interfacial heat flux transients. The study showed significantly reduced values of heat transfer rate for carbonated quenchants compared to quenchants without carbonation. Further, the reduction was more pronounced in the case of PAG-based carbonated quenchants than carbonated distilled water. The results also showed the dependence of heat transfer characteristics of the carbonated media on polymer concentration. The effect of quench uniformity on the microstructure of the material was assessed. © 2016, ASM International.
  • No Thumbnail Available
    Item
    Heat transfer during quenching of inconel probe in non-edible vegetable oils; Wärmeübertragung während des Abschreckens der Inconel-Sonde in nicht essbaren Pflanzenölen
    (Carl Hanser Verlag Kolbergerstrasse 22 Munchen D-81679, 2018) Nayak, U.V.; Prabhu, K.N.
    Non-edible vegetable oils of Karanja and neem were used as quench media in the present investigation. The cooling characteristics of quenchants were obtained using Inconel 600 alloy probe and were compared with that of a fast-quenching mineral oil quench medium. Spatiotemporal heat flux was estimated using inverse heat conduction method. Heat removed from the probe during quenching showed higher and faster heat extraction by karanja oil quench medium compared to the mineral oil. Heat transfer characteristics of neem oil were comparable with the mineral oil. Rewetting time and temperature of vegetable oils were found to be higher than that of the mineral oil. © Carl Hanser Verlag GmbH & Co. KG
  • No Thumbnail Available
    Item
    Quench cooling performance-hardness correlation for AISI 1045 and 1090 steels
    (ASTM International, 2019) Nayak, U.V.; Prabhu, N.
    Heat transfer and microstructure evolution during quenching of AISI 1045 and 1090 steels in vegetable oils was investigated. To simulate the industrial quench heat treatment, reference probes made of medium and high carbon steels were quenched, and heat flux transients were estimated by taking into account the phase transformation. The cooling curves obtained with reference probes made from AISI 1045 and AISI 1090 steels showed kinks indicating enthalpy change accompanied with phase transformations during continuous cooling. This was reflected in the estimated heat flux curves. The section thickness effect on heat flux transients was examined by using probes of diameters 25 mm and 50 mm. The cooling rates measured at various locations across the section diameter of reference probes were related to the hardness using the quench factor technique. The heat transfer characteristics of the quench media, the evolved microstructure, and the resulting hardness were in complete agreement. © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
  • No Thumbnail Available
    Item
    The effect of nanocoatings on critical heat flux (CHF) under pool boiling conditions
    (ASTM International, 2021) Reddy, S.; Prabhu, K.N.; Nayak, U.V.
    The effect of nanomaterial coating on heat transfer characteristics of a copper substrate during pool boiling with distilled water (>99.9 %) was studied. The peak on the pool boiling curve between nucleate and transition boiling is termed the critical heat flux. Multi-walled carbon nanotubes and graphene were used to obtain coatings on the copper substrate. Experiments were carried out at atmospheric pressure. The results showed enhanced critical heat flux for the coated substrates. Graphene-coated copper showed the highest critical heat transfer characteristics compared with that on bare and multi-walled carbon nanotube-coated substrates. The study has significant implications for the enhancement of heat transfer during quench heat treatment. © © 2021 by ASTM International.