Numerical Simulation of Natural Ventilation in Large-Scale Industrial Workshops Based on Orthogonal Test Design

In this paper, orthogonal test design method and the CFD method were used to study the different building envelopes, and the outdoor environment of natural ventilation effect of single span of high temperature industrial workshop. Firstly, 18 ventilation models of workshop with heat source were constructed with orthogonal test design. Secondly, 18 ventilation models of workshop with heat source were simulated with CFD method. Finally, the order of the influencing factors on the ventilation of workshop was obtained through multiple index range analysis of the orthogonal experiment results according to the average temperature inside the workshop. Then the optimal combination of the best ventilation effect was selected. The research results can provide effectively theoretical basis for the future industrial plant ventilation design and optimization.

Some Experimental Results on Internal Fire Whirls in a Vertical Shaft

Earlier studies on burning a pool fire in a vertical shaft model indicated that appropriate sidewall ventilation provision is a key factor for the onset of an internal fire whirl. Experiments on burning a pool fire inside a real-scale shaft model of 9 m tall were performed to further investigate the swirling motion. The full-scale modeling burning tests were carried out at a remote site in China. Four different ventilation openings were arranged. Results of onsetting of internal fire whirls for the four tests will be reported.

Numerical Analysis of the Flow and Heat Transfer in the Sub-Channel of Supercritical Water Reactor

Research activities are ongoing for High performance light water reactor (HPLWR) with square double rows fuel assembly to develop nuclear power plants with the purpose to achieve a high thermal efficiency and to improve their economical competitiveness. However, there is still a big deficiency in understanding and prediction of heat transfer in supercritical fluids. This paper evaluates three-dimensional turbulent flow and convective heat transfer in a single-phase and steady-state sub-channel of HPLWR by using general computational fluid dynamics code, Ansys 14 Fluent. The major concern using supercritical water as work fluid is the heat transfer characteristics due to large variations of thermal properties of supercritical water near pseudo-critical line. In order to ensure the safety of operation in High performance light water reactor (HPLWR), heat transfer deterioration (HTD) must be avoided. Numerical results prove that the RNG k-e model with the enhanced near-wall treatment obtained the most satisfactory prediction and lead to satisfactory simulation results. The HPLWR Square fuel assembly has many square-shaped water rods, Out of four types of sub-channels; three sub-channels SC-1, SC-2 and SC-3 are investigated (adjacent to the side of the moderator flow channels (SC-1) (moderator tube and assembly gap), central sub-channels formed by four fuel rods (SC-2), adjacent to the corner of the moderator tube (SC-3). Since coolant flow distribution in the fuel assembly strongly depends on the gap width between the fuel rod and water rod, fuel rod pitch to diameter ratio 1.1–1.4 with 8mm diameter are considered for simulation. Sub-channel analysis clarifies that coolant flow distribution becomes uniform when the gap width is set to 1.0 mm. was less than 620°C. Effects of various parameters, such as boundary conditions and pitch-to-diameter ratios, on the mixing phenomenon in sub-channels and heat transfer are investigated. The effect of pitch-to-diameter ratio (P/D) on the distributions of surface temperature and heat transfer coefficient (HTC) in a sub-channel, it was found that HTC increases with P/D 1.1 first and then decreases with increasing P/D ratio. Apart from the basic geometry sub-channel, a square sub-channel with a wire-wrapped rod inside has been chosen to investigate the “wire effect”.

Meshless Local Petrov-Galerkin Method for Heat Transfer Analysis

A meshless local Petrov-Galerkin (MLPG) method is proposed to obtain the numerical solution of nonlinear heat transfer problems. The moving least squares scheme is generalized, to construct the field variable and its derivative continuously over the entire domain. The essential boundary conditions are enforced by the direct scheme. The radiation heat transfer coefficient is defined, and the nonlinear boundary value problem is solved as a sequence of linear problems each time updating the radiation heat transfer coefficient. The matrix formulation is used to drive the equations for a 3 dimensional nonlinear coupled radiation heat transfer problem. By using the MPLG method, along with the linearization of the nonlinear radiation problem, a new numerical approach is proposed to find the solution of the coupled heat transfer problem. A numerical study of the dimensionless size parameters for the quadrature and support domains is conducted to find the most appropriate values to ensure convergence of the nodal temperatures to the correct values quickly. Numerical examples are presented to illustrate the applicability and effectiveness of the proposed methodology for the solution of heat transfer problems involving radiation with different types of boundary conditions. In each case, the results obtained using the MLPG method are compared with those given by the FEM method for validation of the results.

Temperature Measurements of a Gold Nanosphere Solution in Response to Light-Induced Hyperthermia

Gold nanospheres (GNSs), biocompatible nanoparticles that can be designed to absorb visible and near-infrared light, have shown great potential in induced thermal treatment of cancer cells via Plasmonic Photothermal Therapy (PPTT) [3]. In this study, light induced heating of a water-based dispersion of 20 nm diameter GNSs was investigated at their plasmon resonance wavelength (λ = 520 nm). Temperature changes of the solution at the point of light irradiation were measured experimentally. A heat transfer model was used to verify the experimental data. The effect of two key parameters, light intensity and particle concentration, on the solution’s temperature was investigated. The experimental results showed a significant temperature rise of the GNS solution compared to de-ionized water. The temperature rise of GNS solution was linearly proportional to the concentration of GNS (from 0.25–1.0 C, C = 1×1013 particles per ml) and the light intensity (from 0.25 to 0.5 W cm−2). The experimental data matches the modeling results adequately. Overall, it can be concluded that the hyperthermic ablation of cancer cells via GNS can be achieved by controlled by the light intensity and GNS concentration. A novel component of this study is that a high power lamp source was used instead of a high power laser. This means that only low cost components were used in the current experimental set-up. Moreover, by using suitable filters and white light from the high power lamp source, it is possible to obtain light in many wavelength bands for the study of other nanoparticles with different plasmon wavelength ranges. The current results represtent just one example in this versatile experimental set-up developed. It should be noted, however, the plasmon resonance wavelength used in this study is not within the therapeutic window (750–1300 nm) [13]. Therefore, the GNSs used in this experiment are only applicable to the surface induced thermal treatment of cancer cells, for instance, in the skin.

Modeling on n-Heptane Pool Fire Behavior in an Altitude Chamber

Airplane as one of the important transport vehicles in our life, its safety problem related to in-flight fire has attracted a wide-spread attention. The combustion behavior of the cabin fire in flight shows some special characteristics because of the high-altitude environment with low-pressure and low oxygen concentration. A low-pressure chamber of size 2 m×3 m×2 m has been built to simulate high-altitude environments, where multiple static pressures for pool fire tests can be configured in the range between standard atmospheric pressure 101.3KPa and 30KPa. Two different sizes of pool fires were tested. Then corresponding modeling were conducted by a LES code FDS V5.5 to examine the mechanism of pressure effect on the n-Heptane pool fire behavior. The burning of liquid fuel was modeled by a Clausius-Clapeyron relation based liquid pyrolysis model. The modeling data was validated against the experimental measurements. The mass burning rate of free-burning pool fire decreases with the decreasing of pressure, which was observed from the modeling to be due to the reduction of flame heat feedback to the fuel surface. Under low pressure, the fire plume temperature increases for the same burning rate. The mechanism of pressure effect on fire behavior was analyzed based on the modeling data.

Optimisation of Conjugate Elliptical Cooling Channels With Internal Heat Generation

This paper presents the development of the three-dimensional flow architecture of conjugate cooling channels in forced convection with internal heat generation within the solid for an elliptical cooling channel configuration. The main objective was to optimise the configuration in such a way that the peak temperature was minimised subject to the constraint of the fixed global volume of solid material. The cooling fluid was driven through the channels by the pressure difference across the channel. The structure had three degrees of freedom as design variables: elemental volume, channel hydraulic diameter and channel-to-channel spacing. The shape of the channel is allowed to morph to determine the best configuration that gave the lowest thermal resistance. A gradient-based optimisation algorithm was applied in order to search for the best optimal geometric configuration that improved thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. The effect of porosities, applied pressure differences and heat generation rate on the optimal geometry was reported. There are unique optimal design variables for a given pressure difference. Results obtained show that the effects of dimensionless pressure drop on minimum thermal resistance were consistent with those obtained in the open literature.

The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

Characteristics of Flame Bases for V-Gutters Stabilized Premixed Flames

The objective of this work is to investigate the flame stabilization mechanism and the impact of the operating conditions on the characteristics of the steady, lean premixed flames. It’s well known that the flame base is very important to the existence of a flame, such as the flame after a V-gutter, which is typically used in ramjet and turbojet or turbofan afterburners and laboratory experiments. We performed two-dimensional simulations of turbulent premixed flames anchored downstream of the heat-conducting V-gutters in a confined passage for kerosene-air combustion. The flame bases are symmetrically located in the shear layers of the recirculation zone immediately after the V-gutter’s trailing edge. The effects of equivalence ratio of inlet mixture, inlet temperature, V-gutter’s thermal conductivity and inlet velocity on the flame base movements are investigated. When the equivalence ratio is raised, the flame base moves upstream slightly and the temperature gradient dT/dx near the flame base increases, so the flame base is strengthened. When the inlet temperature is raised, the flame base moves upstream very slightly, and near the flame base dT/dx increases and dT/dy decreases, so the flame base is strengthened. As the V-gutter’s thermal conductivity increases, the flame base moves downstream, and the temperature gradient dT/dx near the flame base decreases, so the flame base is weakened. When the inlet velocity is raised, the flame base moves upstream, and the convection heat loss with inlet mixture increases, so the flame base is weakened.

Modeling the Temperature Distribution in the Contact Area of a Moving Object in the Case of Linear Friction Welding

This paper describes the results of the mathematical and computer modeling efforts of heat generation in the contact area of a moving object on an infinite plane with friction. The distribution of contact pressure with a linear approximation was obtained. The heat equations for a nonlinear volume heat source were solved. It is shown, that at the initial stages of the linear friction welding (LFW) process temperature distribution is non-elliptical with two hot spots appearing near the edges of the moving specimen. Then as the process progresses these two spots expand and move to the center of the specimen. The results of the mathematical and the numerical modeling in ANSYS APDL software are in good quantitative agreement.