Distance Of Heat Source Research Articles

Investigation of thermal plume and thermal stratification flow in naturally ventilated spaces with multiple heat sources

Natural ventilation driven by thermal buoyancy is an energy-efficient approach to reduce indoor air temperature. In practice, there are generally many heat sources in most naturally ventilated buildings. Therefore, the motion of the thermal plume and the effect of multiple equidistant distributed point heat sources on the stratified flow were studied in this paper. The formula for calculating the thermal stratification height of multiple heat sources was derived and validated. The influences of heat source spacing, heat source surface emissivity and other factors on thermal stratification flow were analysed. In addition, the discrete threshold of multiple plumes was obtained, which could be used to estimate whether the thermal plume is independent. Moreover, the variation in the effective entrainment coefficient of multiple plumes with the heat source distance was analysed. These results can provide a reference for designing natural ventilation for buildings with multiple heat sources and creating a suitable indoor environment.

Welding Characteristics of Laser-MIG Hybrid Welding of Arc-Welded Aluminum Profiles for High-Speed Trains.

To expand the application of laser-MIG hybrid welding in the arc-welded aluminum alloy profile manufacturing for high-speed trains, the laser-MIG hybrid welding characteristics of 4 mm thick A6N01S-T5 arc-welded aluminum profiles were studied in this work. The welding parameters were optimized using the orthogonal test; the microstructure and properties of the joints were analyzed. The results showed that the optimal welding parameters were: welding speed 1.0 m/min, laser power 2.7 kW, arc current 200 A, spot diameter 0.8 mm, heat source distance 3 mm, and defocusing amount 0 mm. The columnar crystals and dense dendrites were observed near the fusion line and in the weld center, respectively, and the grains in the heat-affected zone were slightly coarse. The microhardness of the softening zone in the heat-affected zone was the lowest. The average tensile strength of the joints was 212 MPa, about 86% of the base metal. The samples fractured in the heat-affected zone, and the fractures showed typical plastic fracture characteristics. The results showed that laser-MIG hybrid welding has good applicability and feasibility for the arc-welded profile welding manufacturing.

Arc Characteristics and Welding Process of Laser K-TIG Hybrid Welding

The Q235 steel plate butt joint was successfully welded by the laser K-TIG hybrid welding method. The effects of hybrid welding process parameters such as welding current, the distance between heat sources, laser power, laser defocusing amount, and welding speed on the coupled arc profile and welding process stability were studied. The results indicated that the laser deflects the K-TIG arc, and the deflection angle becomes smaller as the arc current increases. After K-TIG generates small holes, if the laser beam acts on the bottom of the keyhole, the welded depth can be further increased; however, the laser power has little effect on the welded depth. The distance between heat sources is the main factor affecting the state of laser-arc coupling. Optical microstructures of welded joints showed that the grains in the arc zone were coarser than those in the laser zone, and there are more columnar crystals in the fusion zone. The microhardness of the weld center is significantly higher than that of the base metal, up to 220 HV. At the same time, the change of tensile strength of the weld under the influence of a single parameter was analyzed, and it was found that tensile properties of the weld first increased and then decreased with the increase of K-TIG arc current I, heat source distance D, and welding speed V, respectively. With the increase of laser power P, it first decreased and then increased, and with the increase of laser defocusing amount δf, it showed a downward trend.

Analytic temperature field solution of dual laser welding heat sources and application in static recrystallization

The explicit temperature function of dual laser welding was presented, and the effect of welding pass distance and heat source distance on the thermal history was analyzed. There was excellent correlation between analytically solved and finite element method (FEM)-predicted dual laser welding temperature field. The analytical temperature function is applied to study the static recrystallization kinetics upon dual laser welding of nanobainite steel. By calculation, the optimal welding process parameters can be obtained when the static recrystallization fraction takes the maximum value. The corresponding temperature is above the martensite transus temperature and is appropriate to produce sufficient plastic strain in the austenite grains.

Characteristics of heat transfer with different dimensionless distance in an enclosure

In this paper, the influence of different dimensionless distance on heat transfer characteristics in a rectangular enclosure is studied using lattice Boltzmann method (LBM). It is shown that the relation between the Rayleigh number (Ra) and the Nusselt number (Nu) using LBM is in promising agreement with that of the previous experimental data by Corvaro and Paroncini [Appl. Therm. Eng. 28 (2007) 25]. It is found that the characteristic of heat transport is closely related to the dimensionless distance of heat source. Special attention is paid to investigate the relation between Ra and Nu. Some relations between Ra and Nu for different dimensionless distance are approximately established in natural convection. It is further found that the heat transport is enhanced with the increase of dimensionless distance.

The Study of Temperature vs Time Dependence on the Irradiated Surface Side during Wood Burning Process

Article discusses effect of environmental condition on heat transfer from wood sample during burning process. The aim of the paper is to characterize temperature vs time dependence of irradiated wood surface as a function of heat source distance , total heat transfer coefficient and thermal diffusivity . From temperature vs time dependence on the irradiated side is possible to compute heat ignition temperature of wood as one of the most important characteristics of wood burning. All measured values of studied parameters are in very good agreement with table values.

The Utilization of Heat Pipe on Cold Surface of Thermoelectric with Low-Temperature Waste Heat

Thermoelectric (TE) modules are a thermo-element device that can harness the heat and convert it into electrical energy. As an electrical generator system, TE has several advantages i.e not noisy, easy maintenance, relatively small, lightweight and environmentally friendly because it does not produce pollution. In this paper, the research about the performance of TE modules that used for electric generator has been done. TE modules utilize low temperature waste-heat from a solar cell that simulated with a combination of a bulb and a collector plate. TE modules which tested are single and double modules, in which for double modules, connectivity Thermal-Series was used. Parameters of performance such as output power generated are determined by measuring the temperatures difference and the voltages difference at the test module as well as using several equations. The results show that the distance of heat source and load applied will greatly affect the performance of thermoelectric generator (TEG) modules. The results showed that the number of modules and loading will greatly affect the performance of TEG modules. The use of heat pipes generate a far greater power 4-6 times on the single TE Module (0.84 mW) than without heat pipe (0.14 mW), and a double TE modules that uses heat pipe will became 4 times larger (1.48mW) than without heat pipe (0.37mW).