Transient Heat Transfer in a Packed-Bed Elliptic Cylindrical Reactor: A Finite-Volume Approach

This work aims to develop a transient three-dimensional mathematical model using the elliptic cylindrical coordinate system, to predict heat transfer in a elliptic cylindrical packed fixed bed reactor. The model considers variable thermo physical properties and a parabolic temperature profile at the fluid inlet. The governing equation is solved using the finite volume method. Results of temperature profile along the reactor are presented and discussed at different moments.It was verified that the maximum heat transfer rate inside the reactor occurs near the extreme region close to minor semi-axis of the ellipse; the higher temperatures at the reactor surface are also in this region, along the entire height of the bed; the steady-state regime is reached at t = 4.5 s of process, presenting after this time interval,small axial temperature gradients and high radial gradients along of the reactor bed; the parabolic temperature profile give to the bed a predominance of radial temperature gradients, and the radial porosity profile favours a higher heat transfer rate at reactor surface.

Investigation of Thermoelectric Power Generation Module on Waste Heat Recovery in a Downdraft Gasifier

In this study, the thermoelectric power generation (TEG) module is used to recover waste heat from a downdraft gasifier. The performance and optimal operating temperature of TEG module are studied at different locations on the surface wall of catalyst reactor. The simulation model of downdraft gasifier is performed by using the Fire Dynamics Simulator (FDS), its appropriate for the low-speed, thermally-driven flow simulation with an emphasis on incomplete combustion process. The results demonstrate that the simulation temperature of catalyst reactor surface is around 200°C~300°C which is used to convert heat into electricity by TEG module. In summary, the TEG modulus power per unit area can reach 857W/m2 with temperature difference of 140°C and output power attain at least 2.04kW if TEG modulus is applied on the improved downdraft gasifier system (IDGS).

On-Chip Power Generation: Microfluidic-Based Reactor for Catalytic Combustion of Methanol

In this paper, a batch of microfluidic-based reactors with integrated micropillars was fabricated on silicon wafer with standard optical lithography and deep reactive-ion etching (DRIE) technique. A Bosch process of DIRE was used to obtain ∼ 85 μm etching depth and undulating sidewall profiles on the surface of those micropillars. Such structures boost surface-area-to-volume-ratio as well as enhance heat and mass transfer coefficients. Platinum (Pt) nanoparticles (NPs) stabilized by poly-acrylate sodium in a water-ethonal-based suspension were deposited on the reactor surface using a surface-selective infiltration method. By introducing methanol vapor/air gas mixture into the reactors, stable catalytic combustion of methanol over Pt NPs starting from room temperature can be achieved.

Analysis of RESCUE External Reactor Cooling Experiments Using RELAP5 Mod3.3 and ASTEC V2.0 Codes

Safety margin of the in-vessel retention strategy is given by the difference between thermal load acting on inner reactor surface and coolability limit (in terms of critical heat flux) on outer reactor surface. In order to study the two-phase flow in external reactor vessel cooling loop and heat transfer from curved reactor wall, the RESCUE-2 (Representative loops for External System Cooling Understanding Experiments) experimental facility was erected in CEA Cadarache in France. The facility consists of electrically heated simulator of reactor vessel with an ellipsoidal lower head and cooling loop that enables natural circulation of coolant around the reactor wall. In the frame of SARNET 2 project (Severe Accident Research Network of Excellence, 7th EU Framework Programme) several experiments devoted to external reactor vessel cooling phenomena with certain relevance to VVER-440/V213 reactors, were performed on this facility. The heat flux profile generated by electrical heaters in these experiments was based on the results that were obtained by using ASTEC code for this reactor design. The results of two RESCUE-2 experiments are used in this paper for benchmarking of RELAP 5 Mod.3.3 code and ASTEC V2.0 code.