Faculty Publications
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Item Experimental analysis on exergy studies of flow through a minichannel using Tio2/Water nanofluids(Elsevier Ltd, 2018) Narendran, G.; Bhat, M.M.; Akshay, L.; Arumuga Perumal, D.A.The present study involves an experimental investigation on rectangular minichannel heat sink for processor cooling of a workstation. The thermal dissipation power of the corresponding system is 25 W. The heat sink is directly in contact to the processor core and subjected to continuous increase in heat flux to the sink depending on the system loading. Water and TiO2 nanofluid with volume fraction of 0.10%, 0.15%, 0.21% and 0.25% is used as the cooling fluid in the experiments with different volume flow rates with a pulsating pump in the range of 210–400 ml/min respectively. The observations were performed with the sink in both horizontal and vertical position in which heat sink is allowed to reach two different temperature limits of 40 °C and 55 °C above which it is subjected to cooling. The Increase in minichannel efficiency was noticed when flowrate increased from 210 ml/min to 280 ml/min with an increment of 53%, but it started to reduce when flow rate approaches 360 ml/min. The outlet exergy and pumping power increases as the flow rate increases to a limit. Furthermore, decrease in efficiency was noticed beyond flow rate of 360 ml/min and the highest outlet exergy was found at a flow rate of 360 ml/min for about 147.52 W. Additionally, exergy analysis is performed for pure fluid under different flow conditions were examined. Further the effect of nanofluid on pressure drop subjected to pulsating flow for varying volume concentrations is also presented. © 2018 Elsevier LtdItem Experimental investigations of a low heat rejection (LHR) engine powered with Mahua oil methyl ester (MOME) with exhaust gas recirculation (EGR)(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) Kulkarni, P.S.; Godiganur, G.; Ramesh, M.R.; Banapurmath Nagaraj, N.R.; Khandal, S.V.Continued effort has been made by several researchers to reduce the dependency on fossil fuels by using suitable alternative and renewable fuels such as biodiesels for energy harvesting and vehicular applications. Alternative fuels can partially or totally replace fossil fuels in diesel engine applications and address tailpipe emissions as well, which lead to global warming. Performance of compression ignition (CI) engines fueled with biodiesel can be further improved with low heat rejection engine facility by suitably utilizing the heat rejected from the engine and thereby improving the thermal efficiency. Present work combustion surfaces of piston, valves and cylinder head were coated with ceramic material, making the engine fully adiabatic, also known as a low heat rejection (LHR) engine. Experiments were conducted on an LHR engine using diesel and Mahua oil methyl ester (MOME) to determine its performance with and without exhaust gas recirculation (EGR). An attempt has been made to compare the performance and emissions characteristics of a CI engine operated on MOME with and without ceramic coating, and the effect of an EGR system developed in-house. EGR was varied from 0 to 20% in steps of 5%. The LHR engine yielded increased brake thermal efficiency (BTE), reduced emissions of smoke, HC[Hydro Carbon] and CO, and increased NOx with MOME when compared to an uncoated engine. As EGR rate increased the BTE and NOx were slightly reduced whereas the HC, CO and smoke were increased. At 10% EGR, 25.96% BTE, 59 HSU smoke, 46 ppm HC, 0.163% volume CO and 1048 ppm NOx were reported. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.Item Thermodynamic irreversibility and conjugate effects of integrated microchannel cooling device using TiO2 nanofluid(Springer, 2020) Narendran, G.; Gnanasekaran, N.; Arumuga Perumal, A.P.Thermal management is highly essential for the latest electronic devices to effectively dissipate heat in a densely packed environment. Usually, these high power devices are cooled by integrating micro scale cooling systems. Most of the works reported in the literature majorly concentrate on microchannel heat sink in which the characteristics of friction factor and enhancement of heat transfer are analyzed in detail. However, due to the advent of compact electronic devices a crucial investigation is required to facilitate an amicable environment for the neighboring components so as to improve the reliability of the electronic devices. Henceforth, in the present study a combined experimental and numerical analysis is performed to provide an insight to determine the performance of a copper microchannel integrated with aluminium block using TiO2 nanofluid for different particle configurations. Needless to say, the present study, which also focuses on entropy generation usually attributed to the thermodynamic irreversibility, is very much significant to design an optimum operating condition for better reliability and performance of the cooling devices. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item Experimental Investigation on Heat Spreader Integrated Microchannel Using Graphene Oxide Nanofluid(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Narendran, G.; Gnanasekaran, N.; Arumuga Perumal, D.A.Thermal design consideration is highly essential for efficient heat dissipation in advanced microprocessors which are subjected to conjugate heat transfer under high heat flux with a minimal area for cooling. Generally, these multicore processors develop a localized high density heat flux referred to as hotspot. The effective use of microchannel in order to mitigate the hotspot is found in literature; however, the flow induced hotspot still exist due to maldistribution of flow inside the microchannel. Henceforth, the present study provides an experimental insight on laminar forced convection in a parallel microchannel heat sink accompanied with 1.2 mm thin copper heat spreader with a surface area of 30 mm2 to effectively migrate the maldistribution flow induced hot spot. The present experimental study provides a profound insight about the hotspot and migration of hotspot to safe zones; as a result, not only the performance of the multi core microprocessor is highly improved but also the reliability of neighboring components is well secured. © 2019, © 2019 Taylor & Francis Group, LLC.Item Investigation on novel inertial minichannel to mitigate maldistribution induced high temperature zones(Elsevier Ltd, 2022) Narendran, G.; Gnanasekaran, G.Axial conduction in channels depends on inlet velocity and thermal conductivity of the working fluid. In the case of parallel channels, axial conduction depends on heat sink configuration and inlet velocity. That at increased flow rates, the parallel channel generates flow maldistribution and develops localized high temperature zones in the heat sink. Effective use of heat sink configuration to mitigate axial conduction is found in the literature; however, the axial conduction effects are not suppressed in the parallel channels. Henceforth, the present study provides experimental and numerical insight to evaluate the potential of ribs and inertial based spillway channels to overcome the above mentioned problems in parallel channels. Especially, four different heat sink concepts were designed using copper material; normal channel, ribbed channel, ribbed inclined, and ribbed lifted. In which normal channel is experimented with and used as a reference, while the remaining channel types were investigated numerically. The factors such as maldistribution, thermal resistance, and pressure drop are considered to evaluate the impact of the ribs on inlet velocity. The ribbed inclined channel was found to perform better than other types and developed a 33 % lower center channel velocity than the normal channel. The temperature near the exit of the ribbed inclined channel was observed to be more even and the entire width of the minichannel was maintained at 47 °C, this trend was not noticed using other configurations. © 2022 Elsevier LtdItem Experimental investigation on additive manufactured single and curved double layered microchannel heat sink with nanofluids(Springer Science and Business Media Deutschland GmbH, 2023) Narendran, G.; Mallikarjuna, B.; Nagesha, B.K.; Gnanasekaran, N.For the latest high density compact devices, thermal management is crucial for their effective heat dissipation and system reliability. In literature, microchannel heat sink has been established as one of the advanced heat transfer techniques to fulfill the cooling demands of high power electronic applications. However, maldistribution in microchannels causes flow induced high temperature zones (FITZ) which reduces the electrical performance owing to electrical-thermal instability of the integrated chips. One way to mitigate the FITZ is by allowing more coolant inlets in these zones. In the current study, this is achieved by redesigning double layer microchannel heat sink (DMCHS) specific to the FITZ of I-type microchannel configuration using additive manufacturing (AM). Two AM microchannels were tested, one is a single layer microchannel heat sink (MCHS) and another one is a curved double layer microchannel (C-DMCHS). The curved channels were introduced in the bottom channels of C-DMCHS to mitigate FITZ compared to conventional DMCHS. AM microchannels are compared for Nusselt number and friction factor characteristics with the conventional straight channels, and heat treated AM microchannels. From experimental observation, Ti64 3D printed microchannel with Graphene oxide (GO-0.12%) nanofluid developed 75.4% more pressure drop than the Ti64 heat treated microchannel. The results additionally show that the C-DMCHS delivered 26.5% lower FITZ temperature than MCHS. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Item A smart and sustainable energy approach by performing multi-objective optimization in a minichannel heat sink for waste heat recovery applications(Elsevier Ltd, 2023) Narendran, G.; Jadhav, P.H.; Gnanasekaran, N.Minichannel heat sink is widely used in waste heat recovery systems for their compactness and ability to recover heat effectively from high heat flux applications. However, the heat recovery efficiency is constrained by the flow configurations resulting in flow maldistribution. Numerous neural network combined evolutionary algorithms have been used to reduce pressure drop and flow maldistribution factors in the literature. But it is very challenging to assign appropriate weights to these parameters with no physical significance between them for optimization studies. To overcome this, TOPSIS-based optimization studies have been used in the current work to reduce the flow maldistribution factor (ϕ) and increase the Nusselt number (Nu) with ribs and inclined structures. Four Minichannel designs are studied to assess the channel heat recovery efficiency from small-scale incinerators using water and Graphene oxide (GO) nanofluid for three different volume fractions of GO-0.02%, GO-0.07%, and GO-0.12%. The motive is to determine an optimal nanofluid volume fraction and a suitable Minichannel configuration for the given heat flux. The TOPSIS method handles five criteria, including the combination of weightage for the maldistribution factor and Nusselt number. For criteria I ((ϕ)min: (Nu)max = 0.0:1.0) maximum weightage is given to heat transfer, the ribbed channel has gained a higher performance score for GO-0.07% nanofluid volume fraction. For criteria V ((ϕ)min: (Nu)max = 1.0:0.0) maximum weightage is given to maldistribution reduction, the ribbed inclined channel has gained with significantly higher performance score for all the studied nanofluid volume fractions. Further, the study is extended to determine the heat recovery efficiency, and it is found that with the increase in mass flow rate and nanofluid volume fraction, the heat recovery efficiency increases significantly. In particular, the maximum heat recovery efficiency of 66% was obtained for ribbed Minichannel using GO-0.12% nanofluid. © 2023 Elsevier Ltd