On laminar convective cooling performance of hybrid water-based suspensions of Al2O3 nanoparticles and MEPCM particles in a circular tube

2011 ◽  
Vol 54 (11-12) ◽  
pp. 2397-2407 ◽  
Author(s):  
C.J. Ho ◽  
J.B. Huang ◽  
P.S. Tsai ◽  
Y.M. Yang
Keyword(s):  
Circular Tube ◽  
Al2o3 Nanoparticles ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Water Based

An experimental investigation of heat transfer characteristics of water based Al2O3 nanofluid operated shell and tube heat exchanger with air bubble injection technique

2017 ◽  
Vol 6 (4) ◽  
pp. 83 ◽  
Author(s):  
Gaurav Thakur ◽  
Gurpreet Singh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Al2o3 Nanoparticles ◽  
Air Bubbles ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger ◽  
Air Bubble ◽  
Transfer Characteristics ◽  
Water Based ◽  
Shell And Tube

The thermal performance of shell and tube heat exchangers has been enhanced with the use of different techniques. Air bubble injection is one such promising and inexpensive technique that enhances the heat transfer characteristics inside shell and tube heat exchanger by creating turbulence in the flowing fluid. In this paper, experimental study on heat transfer characteristics of shell and tube heat exchanger was done with the injection of air bubbles at the tube inlet and throughout the tube with water based Al2O3 nanofluids i.e. (0.1%v/v and 0.2%v/v). The outcomes obtained for both the concentrations at two distinct injection points were compared with the case when air bubbles were not injected. The outcomes revealed that the heat transfer characteristics enhanced with nanoparticles volumetric concentration and the air bubble injection. The case where air bubbles were injected throughout the tube gave maximum enhancement followed by the cases of injection of air bubbles at the tube inlet and no air bubble injection. Besides this, water based Al2O3 nanofluid with 0.2%v/v of Al2O3 nanoparticles gave more enhancement than Al2O3nanofluid with 0.1%v/v of Al2O3 nanoparticles as the enhancement in the heat transfer characteristics is directly proportional to the volumetric concentration of nanoparticles in the base fluid. The heat transfer rate showed an enhancement of about 25-40% and dimensionless exergy loss showed an enhancement of about 33-43% when air bubbles were injected throughout the tube. Moreover, increment in the heat transfer characteristics was also found due to increase in the temperature of the hot fluid keeping the flow rate of both the heat transfer fluids constant.

Conjugate heat transfer simulation of turbine blade high efficiency cooling method with mist injection

2014 ◽  
Vol 228 (15) ◽  
pp. 2738-2749 ◽  
Author(s):  
Yuting Jiang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
Ping Dong ◽  
Jie Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Mist Cooling ◽  
The Impact

The idea of utilizing a finely dispersed water-in-air mixture has been proven to be a feasible technique to produce very high cooling rates. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the Mark II transonic high pressure turbine stator which is cooled by internal convection through radial round pipes, and different turbulence models and transition models are employed to analyze the influence on results. On the basis of it, the mist cooling is simulated under typical gas turbine operating conditions for internal convective cooling to discuss the improvement of cooling performance. Though the results indicate that mist cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer, the cooling capacity is limited by inadequate evaporation of mist. Considering the distribution of thermal stress and mist evaporation, a compound cooling blade of film cooling with trailing edge ejection is acquired which is modified from the blade of Mark II internal convective cooling; the effects of various parameters including mist concentration and mist diameter on the improvement of cooling performance are investigated, meanwhile the impact of curvature on cooling efficiency and mist trajectory is analyzed finally.

Flow and Convective Heat Transfer Characteristics of Nanofluids With Various Shapes of Alumina Nanoparticles

2009 ◽  
Author(s):  
Kyo Sik Hwang ◽  
Hyo Jun Ha ◽  
Seung Hyun Lee ◽  
Hyun Jin Kim ◽  
Seok Pil Jang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Flow Regime ◽  
Convective Heat ◽  
Circular Tube ◽  
Al2o3 Nanoparticles ◽  
Heat Transfer Characteristics ◽  
Laminar Flow Regime ◽  
Transfer Characteristics

This paper is to investigate flow and convective heat transfer characteristics of nanofluids with various shapes of Al2O3 nanoparticles flowing through a uniformly heated circular tube under fully developed laminar flow regime. For the purpose, Al2O3 nanofluids of 0.3 Vol.% with sphere, rod, platelet, blade and brick shapes are manufactured by a two-step method. Zeta potential as well as TEM image is experimentally obtained to examine suspension and dispersion characteristics of Al2O3 nanofluids with various shapes. To investigate flow characteristics, the pressure drop of Al2O3 nanofluids with various shapes are measured. In order to investigate convective heat transfer characteristics, the effective thermal conductivities of Al2O3 nanofluids with various shapes, the temperature distribution at the tube surface and the mean temperature of nanofluids at the inlet are measured, respectively. Based on the experimental results, the convective heat transfer coefficient of Al2O3 nanofluids with various shapes is compared with that of pure water and the thermal conductivity of Al2O3 nanofluids with various shapes. Thus, the effect of nanoparticles shape on the flow and convective heat transfer characteristics flowing through a uniformly heated circular tube under fully developed laminar flow regime is experimentally investigated.

scholarly journals An experimental study on cooling performance of a car radiator using Al2O3 - ethylene glycol/water nanofluid

2020 ◽  
pp. 179-179
Author(s):  
Serdar Mert ◽  
Halit Yaşar ◽  
Ufuk Durmaz ◽  
Adnan Topuz ◽  
Alper Yeter ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Cooling Power ◽  
Inlet Temperature ◽  
Al2o3 Nanoparticles ◽  
Water Mixture ◽  
Cooling Performance ◽  
Air Inlet ◽  
Vehicle Engine ◽  
Original Case ◽  
Engine Coolant

Nanofluids have high thermal conductivity and can be used as vehicle engine coolant. In this article, the effects of Al2O3 nanoparticles to an engine coolant were experimentally investigated and the results were compared with the results of the original coolant including 50% ethylene glycol and 50% water mixture. The nanofluid was prepared by adding 0.5% Al2O3 nanoparticles by volume. The inlet temperature of the coolant was held constant at 95 Celsius. The tests were carried out at the air inlet temperatures between 23.4-28.6 ?C, the air velocity between 1.7-4.3 m/s, the cooling power between 2.5-15 kW and the cooling fluid flow rates between 10-25 L/min. The results show that nanoparticles increase the cooling performance of the engine radiator. By using Al2O3 nanoparticles, cooling power of the radiator has increased up to 17.46% compared to original case.

scholarly journals A Comparative Study on Cooling Performance of Hot Oil and Molten Salt Media for Industrial Heat Treatment

2019 ◽  
Author(s):  
K.M. Pranesh Rao ◽  
K. Narayan Prabhu
Keyword(s):  
Comparative Study ◽  
Surface Temperature ◽  
Molten Salt ◽  
Eutectic Mixture ◽  
Heat Extraction ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Cooling Stage ◽  
The Media ◽  
Two Stages

Abstract The present work presents a comprehensive comparative study on the cooling performance of hot oil and molten KNO3- NaNO2-NaNO3 eutectic mixture quench media. The study was conducted using a cylindrical Inconel probe of 16? and 60mm length. Cooling curves at different locations in the probe were acquired using thermocouples- DAQ system. The temperature data was recorded in PC and was subsequently used to calculate spatially dependent transient heat flux at the metal quenchant interface. The heat extraction mechanism in hot oil and NaNO2 eutectic mixture was different. Quench heat transfer occurred in two stages namely boiling stage and convective cooling stage during quenching in molten NaNO2 eutectic mixture. In the case of hot oil, apart from these two stages, third stage of cooling namely vapor blanket stage was observed. A detailed study was conducted to compare magnitude and uniformity of heat extraction during each stage of quenching. Molten salt offered higher cooling rate and more spatial uniform cooling as compared to hot oil quench media. The non-uniformity in surface temperature during boiling stage in Inconel probe was 10 times lower in molten salt medium as compared to that observed in hot oil medium. However, the non-uniformity in surface temperature during convective cooling stage in both the media were comparable. Based on the distribution of characteristic cooling time (t85) calculated in quenched Inconel probe, higher and uniform hardness distribution is predicted in steel parts quenched in molten NaNO2 eutectic mixture media as compared.

Experimental Study on Comparison of Cooling Effectiveness Between Steam and Air for a Gas Turbine Nozzle Guide Vane

2012 ◽  
Author(s):  
Wei Wang ◽  
Jianmin Gao ◽  
Xiaojun Shi ◽  
Liang Xu ◽  
Zhao Wang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Guide Vane ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Cooling Method ◽  
Nozzle Guide ◽  
Mass Flow Ratio

An experimental investigation of the cooling performance for a gas turbine vane with internal passages is conducted on a linear turbine cascade consisting of three nozzle guide vanes with a chord length of 126mm and a blade height of 83 mm. Measurements of temperature and static pressure distribution are implemented on the center guide vane, which is internally cooled by air or steam flowing radially through five smooth channels. The main objective of this investigation is to receive more information on the temperature of vane surface, and to compare the cooling effectiveness between air and superheated steam. The experiments are performed for a variety of exit Mach numbers, exit Reynolds number, coolant-to-mainstream mass flow ratio, and coolant-to-mainstream temperatures ratio. The experimental results show, that at coolant-to-mainstream mass flow ratio 0.08 and coolant-to-mainstream temperatures ratio 0.61, the average surface temperature of steam cooled vane decreases about 25% and the corresponding average cooling effectiveness is 52%, while for the air cooled vane, it is 18% and 42%, respectively. Therefore the coolant steam has much better cooling performance than air. Furthermore, the cooling effectiveness at the middle chord region of vane is much higher than that at the leading and trailing region, as is expected. Consequently, this leads to great temperature gradient and thermal stresses at the leading and trailing region, where the internal convective cooling method has insufficient cooling ability. Therefore, besides convective cooling method, more complicated cooling configuration may be necessitated.

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