Investigation of the heat transfer in a square microchannel with Al2O3-H2O nanofluids

2015 ◽  
Vol 82 (11) ◽  
Author(s):  
Ridho Irwansyah ◽  
Julian Massing ◽  
Christian Cierpka ◽  
Christian J. Kähler
Keyword(s):  
Heat Transfer ◽  
Thermal Damage ◽  
Power Demand ◽  
Cooling Systems ◽  
Microelectronic Devices ◽  
Square Microchannel ◽  
Heat Loads

AbstractThe progressing miniaturisation and increasing power demand of microelectronic devices require efficient cooling systems to avoid thermal damage. Future cooling systems have to be capable of dealing with heat loads of more than 200 W/cm

Numerical Simulation of Temperature Field on Different Surface Structure of Bicycle Brake Pairs

2014 ◽  
Vol 697 ◽  
pp. 235-238
Author(s):  
Gang Wu ◽  
Can Chao Huang ◽  
Hong Ling Qin ◽  
Chun Hua Zhao
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Surface Structure ◽  
Surface Structures ◽  
Temperature Fields ◽  
Transfer Model ◽  
Pair Model ◽  
Layer Composite ◽  
Positive Effect ◽  
Heat Loads

Using the basic principle of heat transfer, tribology and numerical simulation, a two-dimensional heat transfer model of the three-layer composite brake pair materials were established. The temperature fields of brake pairs during the process of friction were analyzed. Applied given heat loads at different time node on the brake pair model, the temperatures of different bicycle brake pairs were compared and analyzed. Results show that the improved surface structures of brake pair have positive effect on decreasing the temperature of contact areas than that of ordinary surface structure.

scholarly journals An analytical method to estimate temperature distribution of typical radiant floor cooling systems with internal heat radiation

2021 ◽  
pp. 014459872199800
Author(s):  
Xiaolong Wang ◽  
Wenke Zhang ◽  
Qingqing Li ◽  
Zhenqiang Wei ◽  
Wenjun Lei ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Internal Heat ◽  
Single Layer ◽  
Heat Radiation ◽  
Transfer Model ◽  
Cooling Systems ◽  
Average Temperature ◽  
Floor Surface ◽  
Floor Structure

Radiant floor cooling systems are increasingly used in practice. The temperature distribution on the floor surface and inside the floor structure, especially the minimum and average temperature of floor surface, determines the thermal performance of radiant floor systems. A good temperature distribution of the floor structure is very important to prevent occupant discomfort and avoid possible condensation in summer cooling. In this study, based on the heat transfer model of the single-layer homogeneous floor structure when there is no internal heat radiation in the room, this paper proposes a heat transfer model of single-layer floor radiant cooling systems when the room has internal heat radiation. Using separation variable methods, an analytical solution was developed to estimate temperature distribution of typical radiant floor cooling systems with internal heat radiation, which can be used to calculate the minimum temperature and the average temperature of typical composite floor structure. The analytical solution was validated by experiments. The values of the measured experiments are in a good agreement with the calculations. The absolute error between the calculated and the measured floor surface temperatures was within 0.45°C. The maximum relative error was within 2.31%. Prove that this model can be accepted. The proposed method can be utilized to calculate the cooling capacity of a typical multi-layer composite floor and will be developed in the future study for design of a typical radiant floor cooling system.

scholarly journals Economic justification of the choice of the thermal protection of buildings

2018 ◽  
Vol 196 ◽  
pp. 04078
Author(s):  
Elena Malyavina ◽  
Anastasya Frolova
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Thermal Protection ◽  
Transfer Resistance ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Heat Protection ◽  
The Cost

A large number of factors influence the economically feasible heat transfer resistance of the building enclosing structures. First of all, it is the cost of insulation and heat for the building heating in the cold season. As shown by studies, it is not enough for air-conditioned buildings. The result depends on the mode of the building operation in time and the heat load on the heating and cooling systems. Therefore, in addition to these significant factors of economic feasibility of the thermal protection level, there are the cost of electricity for the production of cold for cooling the building, the cost of the building heating and cooling systems and the cost of connection to power supply networks. The got result is important to convey to the professional community in a clear and compact form. In the present work the buildings of administrative and office purpose are considered, the working day of which lasts from 9-00 to 18-00 hours with different specific heat supply from 0 to 80 W/m2 on the estimated area during working hours. Generalization of the research results is made on the basis of specific heat protection characteristics of the building, which is a product of the overall heat transfer coefficient of the building and the compactness coefficient. The total heat transfer coefficient of the building characterizes the heat losses and the heat inflows to the building through the enclosing structures, and the compactness coefficient can serve as an indicator of the surface area of the building, which is covered with insulation. For these buildings provision has been made for identification of the areas of the total discounted cost combination for all of the above components and the specific heat protection characteristics of the building relating to the feasibility of the specified level of the thermal protection.

scholarly journals Thermal Analysis of Cornea Heated with Terahertz Radiation

2019 ◽  
Vol 9 (5) ◽  
pp. 917
Author(s):  
Wenquan Liu ◽  
Yuanfu Lu ◽  
Rongbin She ◽  
Guanglu Wei ◽  
Guohua Jiao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Terahertz Radiation ◽  
Thermal Effects ◽  
Thermal Damage ◽  
Treatment Approach ◽  
Thz Radiation ◽  
Beam Radius ◽  
Corneal Tissue ◽  
Temperature Distributions

We numerically investigate the thermal effects in a cornea illuminated by terahertz radiation. By modifying the bioheat and Arrhenius equations, we studied the heat-transfer and temperature distributions in the corneal tissue, and evaluated the potential thermal damage. The influence of the beam radius and power density are discussed. We also estimated the effective cornea-collagen shrinkage region, and evaluated the degree of thermal damage in the cornea. We expect this work to open up a novel effective and safe thermal-treatment approach based on THz radiation for cornea reshaping in the field of ophthalmology.

scholarly journals Active magnetocaloric heat pipes provide enhanced specific power of caloric refrigeration

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Lena Maria Maier ◽  
Patrick Corhan ◽  
Alexander Barcza ◽  
Hugo A. Vieyra ◽  
Christian Vogel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipes ◽  
Heat Transfer Fluid ◽  
Specific Power ◽  
Cooling Power ◽  
Cycle Frequency ◽  
Cooling Systems ◽  
Cooling Unit ◽  
Order Of Magnitude ◽  
Almost All

Abstract Today almost all refrigeration systems are based on compressors, which often require harmful refrigerants and typically reach 50% of the Carnot efficiency. Caloric cooling systems do not need any detrimental fluids and are expected to reach 60–70% of the Carnot limit. Current caloric systems utilise the active magnetocaloric regeneration principle and are quite cost-intensive, as it is challenging to achieve large cycle frequencies and thus high specific cooling powers with this principle. In this work, we present an alternative solution where the heat transfer from the heat exchangers to the caloric material is predicated on condensation and evaporation of a heat transfer fluid. Using thermal diodes, a directed heat flow is generated. Thereby we were able to build a cooling unit achieving a specific cooling power of 12.5 W g−1 at a cycle frequency of 20 Hz, which is one order of magnitude larger than the state-of-the-art.

Effect of Turbulent Intensity and Axial Gap on Turbine Heat Transfer Using Steady and Harmonic Models

2013 ◽  
Author(s):  
Sridhar Murari ◽  
Sunnam Sathish ◽  
Ramakumar Bommisetty ◽  
Jong S. Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Pressure Coefficient ◽  
Heat Transfer Characteristics ◽  
Complex Flow ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Loads

The knowledge of heat loads on the turbine is of great interest to turbine designers. Turbulence intensity and stator-rotor axial gap plays a key role in affecting the heat loads. Flow field and associated heat transfer characteristics in turbines are complex and unsteady. Computational fluid dynamics (CFD) has emerged as a powerful tool for analyzing these complex flow systems. Honeywell has been exploring the use of CFD tools for analysis of flow and heat transfer characteristics of various gas turbine components. The current study has two objectives. The first objective aims at development of CFD methodology by validation. The commercially available CFD code Fine/Turbo is used to validate the predicted results against the benchmark experimental data. Predicted results of pressure coefficient and Stanton number distributions are compared with available experimental data of Dring et al. [1]. The second objective is to investigate the influence of turbulence (0.5% and 10% Tu) and axial gaps (15% and 65% of axial chord) on flow and heat transfer characteristics. Simulations are carried out using both steady state and harmonic models. Turbulence intensity has shown a strong influence on turbine blade heat transfer near the stagnation region, transition and when the turbulent boundary layer is presented. Results show that a mixing plane is not able to capture the flow unsteady features for a small axial gap. Relatively close agreement is obtained with the harmonic model in these situations. Contours of pressure and temperature on the blade surface are presented to understand the behavior of the flow field across the interface.

Thermal Fluid-Structure Coupling for Atmospheric Entries

2011 ◽  
Author(s):  
Ojas Joshi ◽  
Pe´ne´lope Leyland
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Thermal Response ◽  
Space Vehicle ◽  
Structural Components ◽  
Fluid Structure ◽  
Coupling Techniques ◽  
Heat Loads ◽  
Transfer Mechanisms

This paper deals with the modeling of aero-thermal aspects of a space vehicle during its entry phase into an atmosphere. We treat the numerical coupling techniques between the external and internal aero-thermo-dynamics (ATD) produced by the interaction of ATD fields with the structural components. The thermal properties induced within the structure via heat transfer mechanisms of convection, conduction and radiation is taken into account presenting multi-disciplinary coupling between the aero-thermo-dynamics, the heat loads and the structural thermal response.

Visualization of Convective Boiling Heat Transfer in Single Micro-Conduits With Different Shapes of Cross Sections

2005 ◽  
Author(s):  
Tzu-Hsiang Yen ◽  
Masahiro Shoji ◽  
Fumio Takemura ◽  
Yuji Suzuki ◽  
Nobuhide Kasagi
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Cross Sections ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Flow Patterns ◽  
Transfer Coefficients ◽  
Convective Boiling ◽  
Heat Transfer Coefficients ◽  
Square Microchannel

Visualization experiments of convective boiling in transparent single micro conduits with the same hydraulic diameter but different cross sections are carried out with simultaneous measurement of local heat transfer coefficients and pressure losses. Two different cross sections with the same similar hydraulic diameters are applied: A circular microtube of 210μm in diameter and a square microchannel of 214μm × 214μm cross section. ITO/Ag thin film of 100 nm is sputtered on the outer surface of the conduits for the direct joule heating. The convective boiling shows some periodic variation of different flow patterns in both square and circular conduits. These flow patterns include bubbly, plug, slug, annular and capillary flows. The capillary flow pattern is the independent liquid droplets moving in the flow direction and very rarely observed in conventional tubes. The reason of such variation of flow patterns is that confined spaces limit the bubble growth in radial direction. So the nucleation bubble grows in both upstream and downstream and makes the flow pattern varies radically. The square microchannel conduit has more simple flow pattern variation, more nucleation bubbles and larger local heat transfer coefficients at lower vapor quality. It is due to that corners of the square microchannel act as helps nucleation cavities. Corners also promotes the formation of liquid film and the contact line between liquid and wall, which can stabilize the flow field. Local heat transfer coefficients decrease with increasing local vapor qualities. Local heat transfer coefficients increase with increasing boiling number but have their maximum value when boiling number reaches critical value. Such peculiar heat transfer characteristics can also be explained by the visualization results.

Sign in / Sign up

Export Citation Format

Share Document