scholarly journals Numerical Simulation on Heat Transfer Characteristics of Water Flowing through the Fracture of High-Temperature Rock

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaohu Zhang ◽  
Zhaolun Wang ◽  
Yanhua Sun ◽  
Chun Zhu ◽  
Feng Xiong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Velocity ◽  
Aperture Size ◽  
Heat Transfer Characteristics ◽  
Fracture Roughness ◽  
Rock Temperature ◽  
The Heat Transfer Coefficient

Deep geothermal resources are becoming an increasingly important energy source worldwide. To achieve the optimal efficiency of this resource, the heat transfer characteristics between flowing water and rock need to be further studied. Using the stereotopometric scanning system 3D CaMega, the fracture geometry data of five cuboid granite rocks were obtained to determine the effects of fracture roughness on the heat transferability of rock. A 3-D model was built based upon the scanned geometry data to assess the effects of rock temperature, water velocity, and roughness, and aperture size of fracture surface on the heat transfer coefficient. The simulation tests show that water velocity has the most noticeable effect, followed by aperture size and rock roughness. On the other hand, the initial rock temperature has the least influence. A new heat transfer coefficient was proposed considering aperture size, water flow velocity, and rock fracture roughness. The calculated values of Reynolds, Prandtl, and Nusselt numbers obtained using this coefficient are in good agreement with the numerical simulation results. This study provides a reference for enhancing the heat transfer coefficient to benefit the exploitation of heat energy of hot dry rock.

Numerical Analysis on Heat Transfer Characteristics of Looped Minichannel Using Phase-Change VOF Method

2013 ◽  
Author(s):  
Hajime Onishi ◽  
Motoya Kawamura ◽  
Yukio Tada ◽  
Akira Takimoto
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Film Condensation ◽  
Film Boiling ◽  
Heat Transfer Characteristics ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

This study develops a numerical simulation of liquid-vapor two phase flows accompanied with the phase change. In the developed simulation, the VOF (Volume of Fluid) method is adopted for tracking the liquid-vapor interface and the temperature recovery method for estimating mass transfer due to the phase change. Firstly, the numerical simulation is performed for film-boiling and film-condensation problems for validating the evaporation (boiling) and condensation calculation. The numerical result for the film-boiling problem is in good agreement with the Berenson’s semi-empirical correlation in terms of the heat transfer coefficient. Moreover, the numerical results for the film-condensation problem are also in good agreement with the theoretical analysis by Nusselt in terms of the film growth rate and the heat transfer coefficient. These have confirmed the reliability of the developed simulation. Then, the developed simulation is applied to investigate the heat transfer characteristics of the heat transport device with a pump-driven looped minichannel. The result reveals a new interesting feature of the minichannel heat device.

scholarly journals Analysis of the Thermal Characteristics of a Composite Ceramic Product Filled with Phase Change Material

Buildings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 217 ◽  
Author(s):  
Joanna Krasoń ◽  
Przemysław Miąsik ◽  
Lech Lichołai ◽  
Bernardeta Dębska ◽  
Aleksander Starakiewicz
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Thermal Characteristics ◽  
Ceramic Product ◽  
Change Material ◽  
The Heat Transfer Coefficient

The article presents a comparative analysis carried out using three methods, determining the heat transfer coefficient U for a ceramic product modified with a phase change material (PCM). The purpose of the article is to determine the convergence of the resulting thermal characteristics, obtained using the experimental method, numerical simulation, and standard calculation method according to the requirements of PN-EN ISO 6946. The heat transfer coefficient is one of the basic parameters characterizing the thermal insulation of a building partition. Most often, for the thermal characteristics of the partition, we obtain from the manufacturer the value of the thermal conductivity coefficient λ for individual homogeneous materials or the heat transfer coefficient U for the finished (prefabricated) partition. In the case of a designed composite element modified with a phase change material or other material, it is not possible to obtain direct information on the above parameter. In such a case, one of the methods presented in this article should be used to determine the U factor. The U factor in all analyses was determined in stationary conditions. Research has shown a significant convergence of the resulting value of the heat transfer coefficient obtained by the assumed methods. Thanks to obtaining similar values, it is possible to continue tests of thermal characteristics of partitions by means of numerical simulation, limiting the number of experimental tests (due to the longer test time required) in assumed different partition configurations, in stationary and dynamic conditions.

Combustion and Heat Transfer in 300MW Oxy-Fired CFBB

2011 ◽  
Vol 354-355 ◽  
pp. 369-375
Author(s):  
Chun Bo Wang ◽  
Xiao Fei Ma ◽  
Jiao Zhang ◽  
Jin Gui Sheng ◽  
Hong Wei Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Particle Diameter ◽  
External Heat ◽  
Transfer Model ◽  
Heat Transfer Characteristics ◽  
Operation Condition ◽  
Transfer Capability ◽  
The Heat Transfer Coefficient

A combustion and heat transfer model in oxy-fired CFBB was set. Particle diameter, voidage of the bed ,etc, was analyzed with 30%, 50%, and 70% oxygen. Take a 300MW CFBB for example, the heat transfer characteristics in furnace were numerical simulated. In the sparse zone, heat transfer coefficient is proportional to oxygen concentration at the same voidage of the bed; under the same operation condition, the heat transfer coefficient in CFB increases with the voidage of the bed at first, then it decreases. It was found the heat transfer capability decrease due to the higher concentration of oxygen. It is necessary to set an external heat exchanger to keep a normal combustion

An Empirical Study on Heat Transfer Characteristics of CuO/Base Oil Nanofluid Flow in a Tube With Coiled Wire Inserts

2010 ◽  
Author(s):  
M. A. Akhavan-Behabadi ◽  
M. Saeedinia ◽  
S. M. Hashemi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Constant Heat Flux ◽  
Wire Diameter ◽  
Heat Transfer Characteristics ◽  
Nanofluid Flow ◽  
Base Oil ◽  
The Heat Transfer Coefficient

In the present study, an experimental investigation has been carried out to study the heat transfer characteristics of CuO/Base oil nanofluid flow inside horizontal oiled wire inserted tubes (roughed tubes) under constant heat flux. The nanofluids with CuO nanoparticles weight fraction ranging from 0 to 2% are prepared. The oiled wires with different wire wire diameteres and different oil pitches are used as inserts inside a horizontal plain copper tube. The nanofluid flowing inside the tube is heated by electrical heating coil wrapped around it. The convective heat transfer characteristis of the prepared nanofluids are measured during laminar fully developed flow inside horizontal plain and roughed tubes under constant heat flux. The effect of different parameters such as mass velocity, wire wire diameter, oil pith, nanofluid particles concentration and heat flux on heat transfer coefficient is studied. The heat transfer coefficient is increased when a roughed tube is used instead of a plain tube. Moreover, at the same flow conditions, by increasing of wire wire diameter and decreasing of oil pitch, the heat transfer performance is improved. Observations also show that by using nanofluid instead of base fluid, the heat transfer coefficient increases and this increase grows at higher nanoparticles concentrations. As a result, it an be concluded that increasing of wire wire diameter, decreasing of oil pitch and increasing the concentration of nanoparticle, contribute to the enhancement of heat transfer coefficient.

Numerical Simulation of Heat Losses between a Partition Plate and the Wall of the Head of a Plastic Heat Exchanger

2010 ◽  
Vol 297-301 ◽  
pp. 650-655
Author(s):  
Rita Aguilar Osorio ◽  
Keith Cliffe
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Polyvinylidene Fluoride ◽  
Plastic Shell ◽  
Tube Heat Exchanger ◽  
Heat Exchanger Design ◽  
The Heat Transfer Coefficient

For this research it was considered that the heat exchanger was affected by leakage in the head across the partition plate and the wall between the tube passes. Leakage was a problem in the plastic shell and tube heat exchanger, because it was difficult to seal the partition plate to the head of the exchanger. The material used for manufacturing the heat exchanger was polyvinylidene fluoride, PVDF. In order to predict the amount of flow leaking through the clearances of the tube passes, a numerical simulation was carried out using the computational Fluid Dynamics CFD Fluent Software. To obtain the percentage of the heat loss across the 4 tube passes, different clearance sizes between the partition plate and the wall of the head of the exchanger were analysed. For the smaller clearance size of 0.2 mm the heat transfer coefficient was reduced up to 15%. These results suggest that the flow mass bypassing the head between tube passes affect the results of the heat transfer coefficient and confirm the experimental observation, that its performance was affected by leakage between tube passes. This research served as an extension of the preliminary plastic heat exchanger design.

scholarly journals Physical and numerical simulation of the thermal and mechanical characteristics of stationary flows in the gasair paths of piston engines

2019 ◽  
Vol 21 (5) ◽  
pp. 22-28
Author(s):  
L. V. Plotnikov ◽  
Yu. M. Brodov ◽  
B. P. Zhilkin ◽  
A. M. Nevolin ◽  
M. O. Misnik
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Sections ◽  
Experimental Studies ◽  
Hydraulic Systems ◽  
Reciprocating Engines ◽  
The Heat Transfer Coefficient ◽  
Exhaust Systems

Thermomechanical perfection of intake and exhaust systems largely determine the efficiency of the working process of reciprocating engines (ICE). The article presents the results of numerical simulation and experimental study of the heat transfer of gas flows in profiled gas- air systems of ICEs. A description of the numerical simulation technique, experimental setup, configurations of the studied hydraulic systems, measuring base and features of the experiments are given. On the basis of numerical modeling, it has been established that the use of profiled sections with cross sections in the shape of a square or a triangle in exhaust systems of an ICEs leads to a decrease in the heat transfer coefficient by 5-11%. It is shown that the use of similar profiled sections in the intake system of reciprocating engines also leads to a decrease in the heat transfer coefficient to 10 % at low air flow rates (up to 40 m/s) and an increase in the heat transfer coefficient to 7% at high speeds. Experimental studies qualitatively confirm the simulation results.

scholarly journals Convective Bubbly Flow of Water in an Annular Pipe: Role of Total Dissolved Solids on Heat Transfer Characteristics and Bubble Formation

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1566 ◽  
Author(s):  
M. M. Sarafraz ◽  
M. S. Shadloo ◽  
Zhe Tian ◽  
Iskander Tlili ◽  
Tawfeeq Abdullah Alkanhal ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Bubble Diameter ◽  
Nucleate Boiling ◽  
Heat Transfer Characteristics ◽  
The Heat Transfer Coefficient

Formation of bubbles in water inside an annulus pipe in a flow boiling regime was experimentally investigated. The effect of various variables, such as total dissolved solid materials (TDS) in terms of mass fraction, flow rate of water, and applied heat flux (HF) on the heat transfer coefficient (HTC) and bubble behavior of water, was experimentally investigated. A regression formula was fitted to estimate the average bubble diameter at various TDS values, with accuracy of <4.1% up to heat flux of 90 kW/m2. Results show that the presence of TDS materials can increase the contact angle of bubble and bubble diameter, and also promotes the HTC value of the system. However, flow rate of water suppressed bubble generation, and increased the heat transfer coefficient due to the renewal of the thermal boundary layer around the boiling surface. Likewise, it was identified that forced convective and nucleate boiling heat transfer mechanisms contribute to the flow of boiling water, and heat flux is a key parameter in determining the mechanism of heat transfer. In the present study, heat flux of 15 kW/m2 at 50 °C was the heat flux in which onset of nucleate boiling was identified inside the annulus pipe. The contact angle of water at TDS values of 300 mg/L and 1200 mg/L was 74° and 124°, respectively, showing the improvement in heat transfer characteristics of water due to the presence of TDS materials.

scholarly journals Heat transfer characteristics of molten salt flowing in steam generator

2021 ◽  
pp. 225-225
Author(s):  
Shiquan He ◽  
Linhao Wei ◽  
Jianfeng Lu ◽  
Weilong Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Molten Salt ◽  
Steam Generator ◽  
Inlet Temperature ◽  
Heat Transfer Characteristics ◽  
Shell And Tube ◽  
Double Pipe ◽  
The Heat Transfer Coefficient

The paper respectively investigated the heat transfer characteristics of molten salt flowed in shell-and-tube and double-pipe steam generator. The shell-and-tube steam generator had seven tubes and molten salt flowed outside the tubes, while the double-pipe steam generator had two concentric tubes and molten salt flowed in the annular duct formed by two tubes. Inlet temperature of molten salt ranged from 270?C to 420?C. The experimental results showed the effect of temperature on heat transfer coefficient was more significant in the double-pipe steam generator compared to the shell-and-tube steam generator. The heat transfer coefficient firstly increased and then decreased as the increase of temperature. Further numerical study was conducted and the results showed, in the shell-and-tube steam generator, the flow is disturbed by the tube bundle and the boundary layer near the inner wall is deformed, so the temperature of molten salt cannot obviously affect the heat transfer. In the double-pipe steam generator, an opposite flow was generated in the near cooled wall region by the buoyancy force. When the inlet temperature was below 315?C, the velocity of the opposite flow was quite low. In this stage, the heat transfer coefficient increased with the increase of temperature. When the inlet temperature continues to rise to 390?C, the opposite flow was enhanced and a stable layer with low velocity formed between the mainstream and the inner cooled wall, resulting increase of heat transfer resistance and impairment of heat transfer coefficient.

scholarly journals Exhaust Gases Cleaning Technology for Vessels

2020 ◽  
Vol 9 (6) ◽  
pp. 1085-1091
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rational Design ◽  
Solid Particles ◽  
Cfd Modeling ◽  
Sulfur Oxides ◽  
The Heat Transfer Coefficient

The present investigation aims to propose results of development of an effective system for the purification of exhaust gases that are emitted to the environment by ship power plant from sulfur oxides (SOx ) and solid particles. Numerical simulation of a combined scrubber with vortex plate based on the developed theoretical approach was performed. Mathematical model of aerohydrodynamic and heat-mass transfer processes contains five interconnected modeling blocks. There was investigated the influence of the scrubber’s geometric characteristics onto the quality of its work. As a result, for the elements of vortex plate the rational design parameters were determined (the angle of blades installation for the swirls =60-90, the ratio between internal and outer radius of the swirls R1 /R2=0,6-0,7). The interaction of gas aerosol with water foam was studied during numerical simulation. It was done with consideration of hydrodynamic regime on the surface of a vortex plate. As a result, for the scrubber rational design and operating parameters were formulated (inlet flow velocity V=18-25 m/s, the height of foam layer H=70-150 mm, inlet dust concentration 40-50 g/cub.m of the gas to be cleaned, cross-sectional area of the purification unit up to 2 sq.m). Computer-based solid-body scrubber model was created during numerical simulation. CFD modeling of the main hydrodynamic processes based on this model was carried out. It was done for all developed structural solutions for scrubber elements. The main results obtained during CFD modeling of the scrubber operation make it possible to analyze the technology of its use and to achieve a reduction in energy costs while maintaining the quality of gas cleaning. The developed theoretical model of a scrubber gives an ability to simulate the flow of a gas-dust stream considering all changes that were done in the geometry of the scrubber. The very model can also be used to optimize the scrubber’s design depending on the type of production and parameters of the gas to be contaminated. During research works there was formulated a conclusion about the necessity to take into consideration the uneven distribution of the field of velocity when modeling the process of gas purification and cooling inside a scrubber. In order to determine the efficiency of heat transfer process inside the scrubber, heat transfer coefficients were found out. They were compared with characteristics of a traditional scrubber’s model based on a perforated plate. Calculation data have shown an excess of the heat transfer coefficient of the vortex plate by 5-7%. It was stated also that the value of the heat transfer coefficient depends on average velocity and moisture content of the gas to be supplied. The rational design and operational parameters of the scrubber obtained on the models made it possible to develop a pilot industrial model of the scrubber and method of engineering calculation. During experimental studies of the scrubber, new scientific results were obtained. They allow one to establish the technological range of irrigation density values, at which the maximum efficiency of trapping solid particles and sulfur oxides (SOx ) is ensured. Experiments were carried out that reveal the relationship between the angle of blades installation of the swirl and the height of the installation of the baffle plate onto the efficiency of foaming and total resistance of the vortex plate.

Heat Transfer Characteristics of Fuel Based Emulsions With Alcohol Additives

2010 ◽  
Author(s):  
Hiroshi Yamasaki ◽  
Kei Suzuki ◽  
Shigeki Furukawa ◽  
Ming-Chia Lai
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Point ◽  
Water Droplet ◽  
Transition Point ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
The Heat Transfer Coefficient

Experimental study has been conducted to study the heat transfer characteristics of the hydrocarbons as the base fuel and water emulsions. The focus is mainly paid on the effect of the ambient emulsion temperature and alcohol additives on the boiling and its inception of fine water droplet dispersed in the emulsions. Heat transfer was measured using an electrically heated horizontal thin Pt wire. It is concluded that there is the transition point in the heat transfer coefficient, which is just above the boiling point of emulsified component of water. The heat transfer of water in fuel emulsions and effect of alcohol additives on it were also revealed.

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