• Energy Research

In this paper, an open-source toolbox that can be used to accurately predict the distribution of the major physical quantities that are transported within a proton exchange membrane (PEM) fuel cell is presented. The toolbox has been developed using the Open Source Field Operation and Manipulation (OpenFOAM) platform, which is an open-source computational fluid dynamics (CFD) code. The base case results for the distribution of velocity, pressure, chemical species, Nernst potential, current density, and temperature are as expected. The plotted polarization curve was compared to the results from a numerical model and experimental data taken from the literature. The conducted simulations have generated a significant amount of data and information about the transport processes that are involved in the operation of a PEM fuel cell. The key role played by the concentration constant in shaping the cell polarization curve has been explored. The development of the present toolbox is in line with the objectives outlined in the International Energy Agency (IEA, Paris, France) Advanced Fuel Cell Annex 37 that is devoted to developing open-source computational tools to facilitate fuel cell technologies. The work therefore serves as a basis for devising additional features that are not always feasible with a commercial code.

A shear usage of electronic mobile devices during gaming, Web browsing and high-power consuming applications, the portable devices get considerably hot enough to be damaged. Previously, active cooling methods adopted to cool the electronic devices had some limitations.

Heat pipes spanning the 300°C to 500°C temperature range are still under research and development stage. Monel/water heat pipes have been previously explored as an option for operation up to 300°C. Life tests of up to 30000 hours have shown good compatibility at 250°C. The author explores the performance of a heat pipe using a different copper/nickel alloy with water as the working fluid at temperatures above 280°C. The performance of these water heat pipes at the upper limit of their operational temperature range in the horizontal position is highlighted and compared against numerical calculations of the heat pipe boiling limit. The use of these heat pipes in the context of thermal storage applications is also briefly explored.

Abstract It is one of the main causes of conductor overheated fusing failure that the poor contact between conductors and the connecting clamp. In late October 2012, a typical case of that was discovered and dealt with by a power plant in Jilin, China. The project investigates the formation mechanism and development of the failure by laboratory tests combined with simulation method. The investigation indicates that there are two main characteristics of the infrared thermal image when conductors and clamps are poorly contacted—the temperature of the conductor is higher than that of the clamps, and the thermal image of the conductor shows it’s heat-producing like a equidistant helix. The characteristic thermal images provide some practical significance to determine and eliminate the equipment defects timely in inspection routines, thus improving the system reliability.

In this paper, a viscous fluid flowing past a rotating isothermal cylinder with heat transfer is studied and simulated numerically by the lattice Boltzmann method (LBM). A numerical strategy for dealing with curved and moving boundaries of second-order accuracy for both velocity and temperature fields is proposed and presented. The numerical strategy and method are validated by comparing the present numerical results of flow without heat transfer with those of available previous theoretical, experimental and numerical studies, showing good agreements. On this basis, the convective heat transfer performance in such rotational boundary environments is further studied and validated; the numerical results are reported in the first time. The effects of the peripheral-to-translating-speed ratio, Reynolds number and Prandtl number on flow and heat transfer are discussed in details.

Abstract Experiments have been conducted to investigate the overall thermal performance of a rectangular channel implemented with an elongated pedestal array. The staggered pedestals were elongated transversely (perpendicular to flow direction) in order that the jet flow from between the pedestals impinges at the center of the pedestals in downstream row. The average heat transfer of the pedestal and endwall surfaces were measured by the lumped capacitance method and transient liquid crystal method, respectively. The pressure drop across the pedestal arrays was measured. The heat transfer coefficients were measured over the Reynolds number range from 6000 to 25,000. Four test sections were designed to evaluate the effect of geometric parameters, i.e. major axis to minor axis ratio D/d = 5.0 and 8.0, X/d = 0.8–1.2, S/d = 1.175–1.5. Conclusions were drawn as the elongated pedestal array provided considerably high heat transfer enhancement. However, the overall thermal performance was compromised by a very high pressure drop across the pedestal array.

To speed up the thermal response rate of the latent heat storage system, this research draws on the ideas of bionics and proposes two methods to enhance the performance of heat storage and heat transfer during phase change process. First, a biomimetic, double-gradient porous ceramic was applied to assemble phase change material (PCM) D-mannitol. The optimized gradient pore structure ensures that the composite possesses higher effective thermal conductivity, and better uniformity of phase interface evolution, with reasonable heat storage density. Numerical simulation predicts a 226 % increase in effective thermal conductivity comparing with the pure D-mannitol. Then, two kinds of carbon-based nanoparticles were added to further reinforce the heat transfer performance. Results found that graphite nanoparticles provide the most significant enhancement in the effective thermal conductivity of the composite material under the premise of ensuring a higher heat storage density. In conclusion, the effective thermal conductivity of the final composite achieves 3.33-fold increase due to the collaboration of the double gradient pore framework and the additive graphite nanoparticles. Accordingly, the overall heat transfer rate could be raised by 4.2 times, comparing with the pure PCM sample. This work demonstrates that the bidirectional gradient pore skeleton has significant advantages in heat storage and transfer over the single pore and unidirectional gradient pore.