水平蛇形地埋管与土壤换热数值计算模型与实验结果对比分析以及变系统加热量对水平蛇形地埋管换热性能的影响

采用热响应实验方法,在系统流量相同的前提下,改变热响应实验的加热量运行埋深2.2m层的水平蛇形地埋管系统。还建立了与实验工况之一条件一致的水平蛇形地埋管与土壤换热耦合数值计算模型,利用CFD软件求解,比较分析埋深为2.2m层水平蛇形地埋管与土壤换热数值计算工况和实验工况,发现数值计算结果与实验结果吻合较好,从而证明实验结果是可用的。比较在相同流量不同加热量的实验工况下单独开启2.2m层水平蛇形地埋管与土壤换热数进出口水温、土壤平均传热系数K随时间的变化,得出一定的变化规律和参考数据。

Hot deformation behavior of spray forming LSHR alloy using constitutive equation and processing map

Flow behaviors of spray forming low solvus high refractory (LSHR) alloy were investigated using hot compression tests performed on a Gleeble?3500 thermal mechanical simulator at temperatures of 1020?1150 °C and strain rates of 0.0003?1.0 s?1. The constitutive equation was established, power dissipation (η) maps and hot processing maps were plotted. The microstructure evolution and dislocation distribution of domains with different values of η in power dissipation maps were also observed. The results show that the flow stress increases with decreasing temperature and increasing strain rate. The activation energy of the spray forming LSHR alloy is 1243.86 kJ/mol. When the value of η is 0.36 at the strain of 0.5, the domain in the processing map shows characteristics of typical dynamic recrystallization (DRX) and low dislocation density. According to the microstructure evolution and processing maps, the optimum processing condition for good hot workability of spray forming LSHR alloy can be summed up as:temperature range 1110?1150 °C; strain rate range 0.01?0.3 s?1.

A high-top version of IAP-AGCM:Preliminary assessment and sensitivity IAP-AGCM

Extending the atmospheric model top to high altitude is important for simulation of upper atmospheric phenomena,such as the stratospheric quasi-biennial oscillation.The high-top version of the Institute of Atmospheric Physics Atmospheric General Circulation Model with 91 vertical layers(IAP-AGCML91)extends to the mesopause at about 0.01 hPa(~80 km).The high-top model with a fully resolved stratosphere is found to simulate a warmer stratosphere than the low-top version,except near the South Pole,thus reducing its overall cold bias in the stratosphere,and significantly in the upper stratosphere.This sensitivity is shown to be consistent with two separate mechanisms:larger shortwave heating and larger poleward stratospheric meridional eddy heat flux in the hightop model than in the low-top model.Results indicate a significant influence of vertical resolution and model top on climate simulations in IAP-AGCM.

Variable mass and thermal properties in three-dimensional viscous flow: Application of Darcy law

This article concentrates on the properties of three-dimensional magneto-hydrodynamic flow of a viscous fluid saturated with Darcy porous medium deformed by a nonlinear variable thickened surface.Analysis of flow is disclosed in the neighborhood of stagnation point.Features of heat transport are characterized with Newtonian heating and variable thermal conductivity.Mass transport is carried out with first order chemical reaction and variable mass diffusivity.Resulting governing equations are transformed by implementation of appropriate transformations.Analytical convergent series solutions are computed via homotopic technique.Physical aspects of numerous parameters are discussed through graphical data.Drag force coefficient,Sherwood and Nusselt numbers are illustrated through graphs corresponding to various pertinent parameters.Graphical discussion reveals that conjugate and constructive chemical reaction parameters enhance the temperature and concentration distributions,respectively.

Influence of the Main Technological Variables of Cyclical Mechanic-Thermal Processing on the Strain Hardening of Steel Parts

The main objective of the present work was to determine the influence of the most important technological variables of CMTP （cyclical mechanic-thermal processing） on the strain hardening in the surface layers of steel parts. For this, it was designed a full factorial plan at two levels of five independent variables that include the whole processing in two and three cycles, the cold-forming degree and force during the plastic deformation （burnishing）, and the temperature and time at the given temperature during the aging. Each cycle is composed of plastic deformation at room temperature plus aging. As dependent variables, the degree and penetration depth of strain hardening were evaluated. Based on the appropriately used set of experimental data, it had been fitted an exponential model for each dependent variables and also a two-degree polynomial fitting of in-depth evolution of microhardness profile was obtained. The amount of cycles and the cold-forming degree are the technological variables of CMTP that influence the most on strain hardening, although other variables also are significant. The microhardness profile highlights that during the CMTP, the strain hardening decreases from the outer bound to the transition zone of the surface layers, where it disappears.

Study of Cycle Output Improvement by Work-Fluid Including Phase Change Material

This paper deals with the output improvement of heating and cooling cycle by using the work-fluid including phase change material.The experimental study is carried out by heat exchange between work-fluid and heat transfer surface.The work-fluid is flown to a high temperature or a low temperature heat transfer surface from the narrow path.In order to increase the amount of the heat transmission,a trace of Diethylether(boiling point 34.8 ℃),as a phase change material(PCM),is added to the work-fluid.The parameters of the experiment are additive amount of PCM,the rotational speed of the displacer piston and the temperature of heat transfer surface.It is clarified that the increasing of engine cycle output is brought by the PCM addition.The effect of PCM addition is evaluated by output ratio which is defined from the experimental cycle output data.The requirements for acquiring the increasing effect of output by adding PCM are clarified.