Heat and moisture transfer in wall-to-floor thermal bridges and its influences on the insulation performance

The moisture modifies the characteristics of heat transfer in building envelopes. Multiple factors, including the distinct hygric properties of various material, gravity, etc., affect the moisture content, resulting in a non-uniform distribution of water vapour in different parts of the envelope (e.g. column, beam, the main part of exterior walls). Usually, the more water vapour in a material, the higher the thermal conductivity, resulting in more heat transfers here. Moreover, condensation easily occurs where there is wet, marking such parts have risks both on structural safety and mould growth. The wall-to-floor thermal bridge (WFTB) occupies the largest area among all kinds of thermal bridges that formed by frame structures. In this study, we aimed to quantify the influence on heat loss through WFTB when the moisture transfer in envelopes is considered. The average apparent thermal resistance of WFTB (R TB, ave) was defined to access the insulation performance of WFTB in practical application. The results of transient numerical simulation indicated that when the moisture transfer is considered, the insulation performance of building envelopes decreases significantly, while the adverse effect of WFTB on heat insulation becomes less pronounced. The results indicated that the measures of insulation for WFTB should be reconsidered when the moisture transfer is considered.

3D transient numerical simulation of a helical roots air compressor for FCVs

Oil-free helical Roots air compressors which have great application potential in air circulation systems for high-power fuel cell systems, such as commercial fuel cell vehicles (FCVs), have the advantages of active adaptation, low cost, large flow rate and high reliability. In this study, a three-dimensional transient numerical simulation model of a helical Roots air compressor was established by considering all leakage clearances. In this study, hexahedral structured dynamic grids were generated in the working chamber and the rotating angle was updated at an increment of 1° to ensure the mesh quality of the entire solving domain. The accuracy of the simulation model was validated using experimental data, and the maximum deviation was less than 4.0%. Based on the simulated results, the pressure field and variation of the pressure field with the rotation angle are presented. It shows that the pressure fluctuation at the discharge side was larger than that at the suction side. The influence of various leakage clearance on the volumetric efficiency was analyzed comparatively. Additionally, the flow field characteristic of clearance was revealed. It is found that the rotor tip clearance was the major factor for the reduction of volumetric efficiency when the size was larger than 0.12 mm instead of the interlobe clearance. It is suggested that more attention should be paid to control the clearance size to ensure the performance of helical Roots air compressors.

Coupled Structural-Rheological Numerical Analysis of Injection Mold

The production of injection molds is an important industry for manufacturing of plastic parts. Considering that time to market reduction is important, it becomes fundamental the use of numerical simulation to reduce design errors. The objective of this work is the presentation of an algorithm for the connection between Moldflow and ANSYS to import loads and then the study of the differences on the approaches studying the tool behavior when considering quasi-static or transient numerical simulation. From this work it was possible to have an overview of where each kind of simulation approach could be used.

Numerical Simulation Study on the Front Shape and Thermal Stresses in Growing Multicrystalline Silicon Ingot: Process and Structural Design

In this paper, a transient numerical simulation method is used to investigate the effects of the two furnace configurations on the thermal field: the shape of the melt–crystal (M/C) interface and the thermal stress in the growing multicrystalline ingot. First, four different power ratios (top power to side power) are investigated, and then three positions (i.e., the vertical, angled, and horizontal positions) of the insulation block are compared with the conventional setup. The power ratio simulation results show that with a descending power ratio, the M/C interface becomes flatter and the thermal stress in the solidified ingot is lower. In our cases, a power ratio of 1:3–1:4 is more feasible for high-quality ingot. The block’s position simulation results indicate that the horizontal block can more effectively reduce the radial temperature gradient, resulting in a flatter M/C interface and lower thermal stress.