Applied Mechanics and Materials Vols. 789-790

Abstract: Volatile organic compounds (VOCs) are gases with low calorific values produced from the painting or drying process whose stable combustion cannot be ensured by direct combustion. In this study, a novel plasma-dump combustor was proposed to remove the VOCs. The combustor is combined the concept of a plasma burner, a dump combustor and a 3D matrix burner. Therefore, it can achieve high destruction with low input energy and stable flame at low temperature.The toluene was used as a representative VOC. The toluene reduction characteristic was examined according to the total gas feed, toluene concentration, dump injector position, and 3D matrix heat accumulator. The toluene decomposition efficiency was 99.5%, and the energy efficiency was 447.2 g/kWh was at the optimum operating conditions.

Abstract: In this paper, the differential quadrature method (DQM) is applied to evaluate the multi-dimensional inverse heat conduction problem (IHCP). The DQM is employed to discretize space domain, and the forward difference method is employed to discretize time domain. Three examples show that the numerical method is accurate. When the noise is added to the exact temperature, the DQM is still a stable and accurate method. Our numerical results are compared with other literatures and show that the method achieves higher accuracy than other methods. Therefore, a simple, convenience, and stable method for evaluate inverse problem is obtained.

Abstract: A quasi one-dimensional engine cycle, the simulation program was developed to predict the simple heat transfer during combustion stroke in a spark ignition engine (SIE) of ethanol-gasoline blended fuels. A two-zone heat release model was utilized to model the combustion process inside the combustion cylinder by using high order iteration method (HIM) in combustion equation. The fuel, air and burned gas properties throughout the engine cycle were calculated by using variable specific heats. The transient heat flux inside the combustion chamber due to the change in the cylinder gas temperature and pressure during combustion was determined by using the constant of heat rate from enthalpy heat rate coefficient. The program was written in MATLAB. The results of this paper such as the average heat flux cycles of the burned gas during the combustion and showing the emissions of at during the combustion process by high iteration method. Based on these results, it was concluded that the fundamental thermodynamic properties of the fuel, air, and combustion product species were in agreement with previously published results to within the scatter of those results typically less than 1% form references 1%. The combustion products were calculated by the high order iteration methods by around 1% from the old methods.

Abstract: This paper outlines a novel numerical methodology to compute the LMTD correction factor for a shell-and-tube heat exchangers. Although the presented methodology can be extended to other shell-and-tube heat exchangers, the analysis presented is this paper concerns the one shell pass and two tube pass configuration, namely 1-2 shell-and-tube heat exchanger. The correction factor is compute by means of an association of e-NTU and LMTD approaches proposed by Kays and London (1998). An analysis of the convergence of the solution provided by the numerical methodology is confronted against results from an analytical solution available in the literature to compute the LMTD correction factor for infinite number of baffles. Numerical results shows that, as the number of baffles is increased, the numerical solution approaches the analytical solution available in the literature. The presented numerical methodology allows the direct computation of the LMTD correction factor for a determined arrangement, giving a new perspective on the project and sizing of shell-and-tube heat exchangers, since typically the analytical solution is applied for all arrangements.

Abstract: Natural convection flow of air and molten gallium in square and elbow-shaped enclosures is studied by a two-dimensional numerical scheme developed by the lead author. The dependence of the flow field and Nusselt number (Nu) on the Rayleigh (Ra) and Prandtl (Pr) numbers is examined in both enclosures. Results are obtained with sufficiently large Rayleigh numbers to observe transition from steady to damped or undamped oscillatory, and chaotic flow. Constant and oscillatory heat transfer rates are compared in both enclosures for air (Pr=0.71) and molten gallium (Pr=0.024).

Abstract: In process of thermal vacuum test of spacecraft, the molecular contamination can have severe effects on performance and reliability of optical payload. In this article, we analyzed the contamination transport mechanism, simplified boundary conditions and input parameters based on physical understanding. We employed the Direct Simulation Monte-Carlo method to simulate the return flux of molecular contamination scattered by residual gas molecules in thermal vacuum tests of solar array and whole satellite. The results of simulation show that the return flux cannot be ignored, and its highest value would be 0.004. This would help the contamination control of spacecraft design, manufacture, test, and on-orbit operation.

Abstract: This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, S_N of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U₀ is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, R_e to evaluate the differences of S_N. The significance of center recirculation zone investigation affected by differences R_e also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U₀. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all S_N after x/D = 0.3 plane towards the outlet of a burner.

Abstract: The turbulent and thermal mixing in a vertically oriented T-junction is investigated numerically using ANSYS FLUENT software. By taking account the buoyancy forces, a steady state three-dimensional turbulent flow is considered with a Reynolds number of 0.4×10⁵ at the cold inlet and 3.3×10⁵ at the hot entrance. The k-ε standard model with standard wall function is chosen to provide closure for the Reynolds stress tensor. The numerical results presented in the form of velocity vectors field and contours of temperature distribution gave a good prediction of the dynamic and the thermal fields namely in the mixing region where a reversed flow is captured.

Abstract: In Peru, jaggery making process has low energy efficiency and it is due to low heat transfer coefficients for natural convection linked to the sugar cane movement generated by the heat exchange between the sugarcane juice and the combustion gases. This low heat transfer coefficients are caused by improper heat exchangers designs. In this work, is performed an experimental analysis that consist in supplie heat to a pot containing sugarcane juice using a hot plate of constant electrical power. This study consist in identify boiling regimes and estimate the heat transfer coefficients linked to natural convection boiling, measuring: (i) the temperature at the bottom of the pot (ii) the temperature at the bottom level of sugarcane juice (iii) the temperature at middle level of sugarcane juice (iv) the temperature at free surface of sugarcane juice (v) rate of water evaporated. The method of linear regression and the correlation of Rohsenow were used for obtaining the values of the heat transfer coefficients ranging from 4088.6 W/m²°C to 12592.8 W/m²°C with power input ranging from 700W to 1300W.

Abstract: To get the low temperature transformation product of austenite, study of cooling behavior of coil is essential. Temperature distribution profile of the hot strip coil has been determined by using finite volume method (FVM) vis-à-vis finite difference method (FDM). It has been demonstrated that FVM offer greater computational reliability in estimation of contact pressure distribution and hence the temperature distribution for curved and irregular profiles, owing to the flexibility in selection of grid geometry and discrete point position, Moreover, use of finite volume concept allows enforcing the conservation of mass, momentum and energy, leading to enhanced accuracy of prediction.