Synthesis and Analysis of Nanoporous Material Using Microchannel

2011 ◽  
Author(s):  
Mikyung Lim ◽  
You Kyoung Seo ◽  
Seung S. Lee ◽  
Young Kyu Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Flow Boiling ◽  
Synthesis Method ◽  
Synthesis Process ◽  
Synthesis Rate ◽  
Nanoporous Material ◽  
Sio2 Substrate

Recent small electronic equipments with various functions require extreme increase of heat transfer rate per unit surface. Current small electronic equipments’ cooling abilities have limitation with its heat transfer rate. Boiling is one of the solutions for this problem since it can be applied by using microchannel and flow boiling. Also, it has much higher heat transfer coefficient than large-scale cooling system. However, boiling is not easily initiated and surface temperature often reaches high temperature even without boiling which could burn the electronic equipment. To enhance boiling, one of the best methods is coating nanoporous material on the surface. Synthesis characteristics of nanoporous material depend on both the temperature and concentration condition. Therefore, the accurate condition for the synthesis process is required but, the current synthesis method cannot control both temperature and concentration also wastes both time and resources. This research suggests a way of synthesizing nanoporous material using microchannel which can obtain accurate control of variables and save the resources. Microchannel reactor for nanoporous material synthesis is designed with channel on the SiO2 substrate. Cu-BTC solution passes through the microchannel and nanoporous material is coated on SiO2 substrate. Through time and temperature variable experiment, the procedure of growth of nanoporous material is observed within time change and transformation of crystalline structure of nanoporous material is obtained by temperature change. Most importantly, this method provides much higher synthesis rate and uniformity than the current synthesis method. The experiment on the effect of width of microchannel on synthesis rate was also performed. This has important meaning since it can be applied to the other materials which can be synthesized in microchannel and could increase their synthesis rate too. Synthesis in microchannel provides high reproducibility and helps to accomplish accurate analysis. Moreover, synthesis of nanoporous material in the microchannel is easier to fabricate and easier to be applied in the cooling system using the flow boiling. Therefore, synthesis in microchannel can make a significant improvement in cooling system of small equipments, and it contributes to miniaturization of electronic equipments.

The Effect of Hot-Streaks on HP Vane Surface and Endwall Heat Transfer: An Experimental and Numerical Study

2005 ◽  
Author(s):  
T. Povey ◽  
K. S. Chana ◽  
T. V. Jones ◽  
J. Hurrion
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Numerical Study ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Wall Heat Transfer ◽  
Hot Streak ◽  
End Wall

Pronounced non-uniformities in combustor exit flow temperature (hot-streaks), which arise because of discrete injection of fuel and dilution air jets within the combustor and because of end-wall cooling flows, affect both component life and aerodynamics. Because it is very difficult to quantitatively predict the affects of these temperature non-uniformities on the heat transfer rates, designers are forced to budget for hot-streaks in the cooling system design process. Consequently, components are designed for higher working temperatures than the mass-mean gas temperature, and this imposes a significant overall performance penalty. An inadequate cooling budget can lead to reduced component life. An improved understanding of hot-streak migration physics, or robust correlations based on reliable experimental data, would help designers minimise the overhead on cooling flow that is currently a necessity. A number of recent research projects sponsored by a range of industrial gas turbine and aero-engine manufacturers attest to the growing interest in hot-streak physics. This paper presents measurements of surface and end-wall heat transfer rate for an HP nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular transonic rotating turbine facility. Measurements were conducted with both uniform stage inlet temperature and with two non-uniform temperature profiles. The temperature profiles were non-dimensionally similar to profiles measured in an engine. A difference of one half of an NGV pitch in the circumferential (clocking) position of the hot-streak with respect to the NGV was used to investigate the affect of clocking on the vane surface and end-wall heat transfer rate. The vane surface pressure distributions, and the results of a flow-visualisation study, which are also given, are used to aid interpretation of the results. The results are compared to two-dimensional predictions conducted using two different boundary layer methods. Experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ Farnborough, a short duration engine-size turbine facility. Mach number, Reynolds number and gas-to-wall temperature ratios were correctly modelled. It is believed that the heat transfer measurements presented in this paper are the first of their kind.

The Effect of Hot-Streaks on HP Vane Surface and Endwall Heat Transfer: An Experimental and Numerical Study

2005 ◽  
Vol 129 (1) ◽  
pp. 32-43 ◽  
Author(s):  
T. Povey ◽  
K. S. Chana ◽  
T. V. Jones ◽  
J. Hurrion
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Numerical Study ◽  
Guide Vane ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Gas Temperature ◽  
Hot Streak

Pronounced nonuniformities in combustor exit flow temperature (hot-streaks), which arise because of discrete injection of fuel and dilution air jets within the combustor and because of endwall cooling flows, affect both component life and aerodynamics. Because it is very difficult to quantitatively predict the effects of these temperature nonuniformities on the heat transfer rates, designers are forced to budget for hot-streaks in the cooling system design process. Consequently, components are designed for higher working temperatures than the mass-mean gas temperature, and this imposes a significant overall performance penalty. An inadequate cooling budget can lead to reduced component life. An improved understanding of hot-streak migration physics, or robust correlations based on reliable experimental data, would help designers minimize the overhead on cooling flow that is currently a necessity. A number of recent research projects sponsored by a range of industrial gas turbine and aero-engine manufacturers attest to the growing interest in hot-streak physics. This paper presents measurements of surface and endwall heat transfer rate for a high-pressure (HP) nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular transonic rotating turbine facility. Measurements were conducted with both uniform stage inlet temperature and with two nonuniform temperature profiles. The temperature profiles were nondimensionally similar to profiles measured in an engine. A difference of one-half of an NGV pitch in the circumferential (clocking) position of the hot-streak with respect to the NGV was used to investigate the affect of clocking on the vane surface and endwall heat transfer rate. The vane surface pressure distributions, and the results of a flow-visualization study, which are also given, are used to aid interpretation of the results. The results are compared to two-dimensional predictions conducted using two different boundary layer methods. Experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ Farnborough, a short-duration engine-sized turbine facility. Mach number, Reynolds number, and gas-to-wall temperature ratios were correctly modeled. It is believed that the heat transfer measurements presented in this paper are the first of their kind.

scholarly journals EFFECT OF OIL ON HEAT TRANSFER OF MIXED REFRIGERANT BOILING IN EVAPORATOR TUBES IN REFRIGERATION MACNINES

2019 ◽  
pp. 88-93
Author(s):  
Alexey Vasilievich Ezhov ◽  
Sergey Sergeevich Ivanov ◽  
Aleksandr Bukin ◽  
Vladimir Grigorievich Bukin
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Boiling ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pipe Length ◽  
Heat Transfer Coefficients

The paper presents the results of an experimental study of the effect of oil on the heat transfer rate at boiling of mixed refrigerant R406A. Since the air conditioning system is not a pure refrigerant, but a mixture of oil with a concentration of up to 8%, such an amount of oil affects both hydrodynamics and heat exchange in the evaporators. The experimental work covers the entire range of regime parameters typical for these systems. There is shown the process of changing oil concentration in the pipe, as the working fluid boils, proving that most of the oil pipe does not impair the heat exchange in the course of two-phase flow boiling. Different modes of refrigerant R406A boiling dynamics have been defined, and each mode is given a quantitative assessment in terms of the effects of the oil and explaining of this effect on the fluid flow and heat transfer based on visual observations and the experiment results. The main factor of the effect is the freon-oil foam, which increases the proportion of the wetted surface in the wave and stratified modes and the heat transfer rate to 30%. A comparison of the heat transfer coefficients both in the cross section and along the pipe length has been performed, showing that the maximum change in heat transfer occurs in the upper part of the surface due to developing a dry wall on it and wetting it with freon-oil foam. A comparison of the heat transfer rate of pure refrigerant R406A has been done; the presence of oil in it shows that the effect of oil is complex and ambiguous. Calculation and criterion dependences for calculation of heat transfer coefficients in different modes have been proposed.

Gravity Influence on Heat Transfer Rate in Flow Boiling

2012 ◽  
Vol 24 (3) ◽  
pp. 203-213 ◽  
Author(s):  
Coen Baltis ◽  
Gian Piero Celata ◽  
Maurizio Cumo ◽  
Luca Saraceno ◽  
Giuseppe Zummo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Boiling

scholarly journals Modelling of Automobile Radiator by Varying Structure and Materials

2020 ◽  
Vol 9 (2) ◽  
pp. 652-656
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Internal Combustion Engines ◽  
Cooling System ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Automotive Application ◽  
Simple Modification ◽  
Engine Cooling

Radiators used in the automotive application are a class of heat exchangers whose main purpose is to cool the coolant coming from the internal combustion engines. These coolants flow through tubes covered with fins that facilitate a faster way of heat transfer to the surrounding more efficiently. With the increase in efficiency of the engine cooling system it directly helps in the longevity of the engine in other words, the life of the internal combustion engine increases multifold times. Upon investigating we found different shapes that can be used to optimize the radiators efficiency. There are several other ways to improve the efficiency of a radiator. And these can be achieved by improving the surface area of the radiator, improving airflow through it, improving coolant property which flows through these tubes covered with fin all around and at last using alternate materials that prove to be more efficient than the present ones that are being used. The demand of the current times of climate change and energy crisis have paved way for improved heat transfer rates and designing radiators in smaller dimensions and sizes at the same time being more efficient than the previous generation of radiators. With the above conditions in mind, it has been found out that with a simple modification of changing the existing rectangular-shaped radiators into spiral-shaped ones thereby improving efficiency to improved levels, which finds its use in the current generation of vehicles which are benefitting from the improved rate of heat transfer taking place. The spiral radiator of copper tube used here is wound in two coils connected centrally. Spiral tubes of the radiator have circumferential fins. In this type of configuration, heat transfer rate will increase because of having a circumferential fin across the length of the spiral tube through which water flows. These design considerations have been done keeping in mind the major aims to achieve for this type of design and they are improving heat transfer rate and achieving compactness of shape of radiator. We also did Computational Fluid Dynamics or CFD Analysis to test the material properties for the application of heat transfer and how it fares against old materials.

Computational Fluid Dynamics Simulation Based Comparison of Different Pipe Layouts in an EATHE System for Cooling Operation

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Kamal Kumar Agrawal ◽  
Rohit Misra ◽  
Mayank Bhardwaj ◽  
Ghanshyam Das Agrawal ◽  
Anuj Mathur
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Capital Investment ◽  
Cooling System ◽  
Temperature Drop ◽  
Dynamics Simulation ◽  
Helical Coil ◽  
Ansys Fluent ◽  
Passive Technique

Earth air tunnel heat exchanger (EATHE) is a capable and quite simple passive technique which may be utilized for space cooling/heating using the constant temperature of underground subsoil. However, it could not gain much attraction as a heating/cooling system as it requires larger trench lengths to accommodate longer pipes. Larger trench lengths involve huge excavation cost and a sufficiently large piece of land. The length of the trench needed can be reduced substantially by adopting a proper pipe layout. In the present study, the performance of U-shaped, slinky-coil, and helical-coil pipe layouts of an EATHE system is compared numerically using ANSYS FLUENT 15.0. Results reveal that the temperature drop and heat transfer rate per unit trench length are higher in the slinky-coil pipe layout than in U-shaped and helical-coil pipe layouts. After 12 h of continuous operation, the effectiveness of the EATHE system with U-shaped, slinky-coil, and helical-coil pipe layouts is obtained as 0.60, 0.80, and 0.78, respectively. The study reveals that the selection of pipe layout for the EATHE system mainly depends on temperature drop EATHE is capable of giving, heat transfer rate, pumping power required, and ease of fabrication and installation as all these factors directly affect the initial and recurring capital investment for the EATHE system.

scholarly journals Influence of Heat Sink on the Mold Temperature of Gypsum Mold Used in Injection Molding

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 701
Author(s):  
Chung-Chih Lin ◽  
Kun-Chen Chen ◽  
Hon-Chih Yeh
Keyword(s):  
Heat Transfer ◽  
Injection Molding ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Cooling System ◽  
Mold Temperature ◽  
Thermal Circuit ◽  
Molded Part ◽  
Gypsum Mold

Gypsum molds have been developed as an alternative for the Rapid tooling (RT) method used in injection molding. However, the poor capability of the heat delivery forces the gypsum mold to operate under a high-risk condition, and distortion of the molded part becomes apparent. The goal is to investigate the effect of a heat sink on the reduction of the gypsum mold temperature and to establish a methodology for the heat sink design. The methodology used the advantage of the electrical circuit concept to analyze the mold temperature. The heat transfer of a mold was modeled using an equivalent thermal circuit. After all the components on the circuit were determined, the heat transfer rate could then be calculated. Once the heat transfer rate was known, the mold temperature could be easily analyzed. A modified thermal circuit considering transverse heat conduction was also proposed, which estimated the mold temperature more accurately. The mold temperature was reduced by 16.8 °C when a gypsum mold was installed with a 40 mm thick heat sink in a parallel configuration. Moreover, the reduction of the mold temperature improved the deflection of the molded part from 0.78 mm to 0.54 mm. This work provides a quick approach to analyze the mold temperature based on the thermal circuit concept. As the cooling system of the mold was modularized analytically, important properties of the cooling system in the heat transfer process were revealed by analyzing the thermal circuit of the mold, for example, the heat transfer rate or the mold temperature.

Experimental Study and High Speed Visualization of Flow Boiling Characteristics in Silicon Microgap Heat Sink

2012 ◽  
Author(s):  
Tamanna Alam ◽  
Poh Seng Lee ◽  
Christopher R. Yap ◽  
Liwen Jin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
High Speed ◽  
Flow Boiling ◽  
Gap Size

Flow boiling in microgap heat sink is very attractive for high-performance electronics cooling due to its high heat transfer rate and easy fabrication process. In absence of thermal interface material between the active electronic component and a microgap cold plate, significant reduction in interface thermal resistance and enhancement in heat transfer rate can be achieved. In earlier studies by these authors, encouraging results have been obtained using microgap heat sink as it can potentially mitigate flow instabilities, flow reversal and maintain uniform wall temperatures over the heated surface. So, more work should be carried out to advance the fundamental understanding of the two-phase flow heat transfer associated with microgap heat sink and the underlying mechanisms. In this study, local flow boiling phenomena in different microgap sizes have been investigated experimentally. Experiments are performed in silicon based microgap heat sink having microgap depth ranging from 80 μm to 500 μm, using deionized water with 10 °C subcooled inlet temperature. The effects of mass flux and heat flux on heat transfer coefficient and pressure drop characteristics are examined by using different mass fluxes ranging from 400 kg/m2s to 1000 kg/m2s and effective heat flux varying from 0 to 100 W/cm2. Apart from these experimental investigations, simultaneous high speed visualizations are conducted to observe and explore the mechanism of flow boiling in microgap. Confined slug and annular boiling are observed as the two main heat transfer mechanisms in microgap. Moreover, experimental results show that flow boiling heat transfer coefficients are dependent on gap size, and the lower the gap size, higher the heat transfer coefficient.

EXPERIMENTAL AND PERFORMANCE ANALYSIS OF SOLAR REFRIGERATION SYSTEM USING NANO FLUIDS

2019 ◽  
Vol 14 (2) ◽  
Author(s):  
Sivakumar M ◽  
Mahalingam S ◽  
Ranjithkumar V
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solar Energy ◽  
Electric Power ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Refrigeration System ◽  
Vapour Compression ◽  
Solar Refrigeration

In today’s world refrigeration systems play a vital role to fulfil the human needs. A continuous research is being carried out by many researchers in order to improve the performance of these systems. Presently used, vapour compression refrigeration system does not work efficiently due to shortage of electric power. This study covers a broad overview of solar photovoltaic technology, which uses easily available solar energy for refrigeration purpose. It includes a motor, a compressor, an inverter and battery, a photovoltaic controller and panels. This can be done by converting solar energy in to electricity by means of photovoltaic devices, which can be utilized by the electric motor to drive vapour compression refrigeration system. The main objective of the study is managing the shortage of electric power, in living environments by using a cooling system coupled to a solar installation. In this solar refrigeration system, when conventional refrigerants like (R22, HFCR134a, R600, etc.) are used it leads to low thermal conductivity, heat transfer rate and COP level and some of the other impacts are acid rain, melting of glaciers, sea level raising, health impacts, atmospheric pollution, ozone depletion, which is very hazardous to the environment. To avoid these threats, one of the ways is to use nanofluids which are not harmful to the environment. The usage of nanofluids results in high thermal conductivity, heat transfer rate and give better COP level. The following three nanofluids Al2o3, Zro2, Cu2o have been already used in the refrigeration system. Some of the properties of given nanofluids will be changed to innovate new nanofluids. The innovated nanofluids will be used in refrigeration system and the same will be compared with other nanofluids like R22, R134a, R290, and R600a. Even though Al2o3, Zro2, Cu2o gives good results, the new nanofluids have been innovated for better results.

Sign in / Sign up

Export Citation Format

Share Document