上盖棉被下铺毛毯最保暖

如果家里有棉被和毛毯,冬天怎么盖才最保暖呢?盖被子的顺序对保暖效果是有影响的:上盖棉被、下铺毛毯的“夹心盖法”最为保暖;其次是先盖一层棉被,再在棉被上盖一层毛毯;先盖毛毯,再盖棉被不如前两者暖和。专家分析:人体在不断散发热量,如果热量扩散得太快会觉得很冷,控制扩散的速度,则能起到保暖作用。棉被和毛毯其实都有蓄热效果,所以身下铺毛毯、上面盖被子,可以达到上下双重锁温的效果。如果先盖被子再在上面盖毯子,也会很保暖,是因为被子比较蓬松。

超高压含硫气井井筒内天然气水合物解堵技术

为了安全、高效、经济地解除超高压气井井筒中的天然气水合物(以下简称水合物)堵塞,利用自主研发的固体自生热解堵剂在井筒内发生化学反应所释放出的热量来溶解水合物并防止其再次生成,通过调节解堵剂加量,来实现生热时间和生热量可调,进而将形成的化学自生热解堵技术在四川盆地超高压含硫气井的解堵作业中进行了应用。研究结果表明:①采用自主研发的固体化学自生热解堵剂,通过调整加量,可以实现生热峰值温度(34.2~88.5℃)、生热时间(24.2~884.0 min)可调,并且反应产物中包含有水合物抑制剂,能够抑制水合物再次生成;②随着解堵剂浓度增大,热传递速率加快,使解堵剂周围水合物的分解速率增加;③随着井筒内径增大,解堵时间延长,并且从64 mm增至76 mm对应的解堵时间增长率小于从76 mm增至102 mm对应的解堵时间增长率;④热量扩散模拟计算结果与现场实际用量的吻合率超过85%,证明所建立的化学自生热解堵剂热量扩散模型可靠,可以用于现场解堵剂加量的计算;⑤使用抗硫耐压140 MPa的固体药剂投加装置投加固体自生热解堵剂,在四川盆地超高压含硫气井已应用3井次,成功解除了水合物堵塞,使气井顺利恢复生产。结论认为,所形成的解堵技术针对超高压含硫气井井筒中形成的水合物堵塞的解除效果好、现场操作安全简单、费用低,具有较好的应用前景。

Morphological evolution ofγ'phase in K465 superalloy during thermal fatigue

The alternative heating/cooling cycles (thermal fatigue) of K465 superalloy were carried out. The specimens were held at 1 050℃for 300 s, then quenched into 20℃recycling water for 10 s as a cycle. During thermal fatigue,γ' precipitates changed typically from cubical to irregular shape after 10 cycles, to complex configuration after 20 cycles and raft-like shape after 30 cycles. The very fineγ' particles precipitated inter the originalγ' particles. The elastic energy dominated morphological evolution of largeγ' precipitates, and the thermal stress induced the directional growth of precipitates that minimized the total energy of the system, and the nucleation theory controlled the formation of fineγ' precipitate. The results show that the volume fraction ofγ' precipitates is increased with the increase of heating/cooling cycles, which improves the mechanical property of this alloy.

Influence of phosphorus on oxidation behavior of low thermal expansion superalloy IN909 at 650℃

The effect of phosphorus on the oxidation resistance of low thermal expansion alloy IN909 was studied. The composition and structure of the oxidation layer were analyzed. It is found that the oxidation initiates at the grain boundaries. During the oxidation, Fe atoms diffuse toward the surface and form the outside oxidation layer as the oxide of iron. The transition oxidation layer lies between the oxidation layer and the matrix which is enriched with Nb, Ti and Si, forming FeTiO5, Nb2O5,Fe2SiO4 and TiO2. Phosphorus hardly influences the thermal expansion coefficient of IN909 alloy. However, it increases the formation ofεphase at the boundary of the transition oxidation layer and matrix. As a result, the oxidation rate is decreased efficiently because theεphase inhibits the diffusion of the element such as iron from the matrix to the oxidation layer.

蒸发冷却制冷水设备的改进设计

分析现有间接蒸发冷却制冷水设备的不足并设计两个改进装置,理论显示加了逆流汽水表面式冷却换热器的设备制冷水效果更好。对三种蒸发冷却制冷水设备进行分析计算,结果显示三种装置的损失依次减少。从角度分析湿空气参数对蒸发冷却过程的影响,显示提高蒸发冷却效率的关键在于提高化学的利用率,使其更多地转化为热量,进而降低湿空气的损失。湿空气变化的温度差仅影响热量增加量,但湿空气变化的湿度差不仅影响热量增加量更影响化学的减少量。

环境因素对煤自热的影响

环境因素对煤自热的影响为：可使煤的水分含量发生变化；改变煤氧接触条件：使生产成的热量扩散。可分为：

Double-diffusive Fluxes of Salt and Heat in the Upper Layer of North Pacific Intermediate Water

Almost half of the oceanic water columns exhibit double-diffusion. The importance of double-diffusion in global oceans’ salt and heat fluxes, water-mass formation and mixing, and circulation is increasingly recognized. However, such an important physical process in the ocean has not been well studied. One of the reasons is the difficulty of parameterizing and quantifying the processes. The paper presented here attempts to quantify the double-diffusive fluxes of salt and heat in the ocean. Previous qualitative analysis by applying the water-mass Turner angle, mTu, to the North Pacific Intermediate Water (NPIW) layer showed a favorable condition for salt-fingering in the upper NPIW due to the overlying warm/salty water above the cold/fresh NPIW core, and a doubly-stable condition in the lower NPIW where potential temperature decreases with depth while salinity increases, inducing double stratification with respect to both potential temperature and salinity. The present study gives a quantitative estimate of double-diffusive fluxes of salt and heat contributed by salt-fingering in the upper NPIW layer.

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.

Connection between heat diffusion and heat conduction in one-dimensional systems

Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method, we demonstrate that for one-dimensional systems, using the indices of particles as the space variable, which has been accepted as a convention, may lead to misleading conclusions. We then show that though in one-dimensional systems there is no general connection between energy diffusion and heat conduction, however, a general connection between heat diffusion and heat conduction may exist. Relaxation behavior of local energy current fluctuations and that of local heat current fluctuations are also studied. We find that they are significantly different,though the global energy current equals the globe heat current.

An improved algorithm to estimate the surface soil heat flux over a heterogeneous surface: A case study in the Heihe River Basin

Surface soil heat flux(G0) is an indispensable component of the surface energy balance and plays an important role in the estimation of surface evapotranspiration(ET). This study calculated G0 in the Heihe River Basin based on the thermal diffusion equation, using the observed soil temperature and moisture profiles, with the aim to analyze the spatial-temporal variations of G0 over the heterogeneous area(with alpine grassland, farmland, and forest). The soil ice content was estimated by the difference in liquid soil water content before and after the melting of the frozen soil and its impact on the calculation of G0 was further analyzed. The results show that:(1) the diurnal variation of G0 is obvious under different underlying surfaces in the Heihe River Basin, and the time when the daily maximum value of G0 occurs is a few minutes to several hours earlier than that of the net radiation flux, which is related to the soil texture, soil moisture, soil thermal properties, and the vegetation coverage;(2) the net radiation flux varies with season and reaches the maximum in summer and the minimum in winter, whereas G0 reaches the maximum in spring rather than in summer, because more vegetation in summer hinders energy transfer into the soil;(3) the proportions of G0 to the net radiation flux are different with seasons and surface types, and the mean values in January are 25.6% at the Arou site, 22.9% at the Yingke site and 4.3% at the Guantan site, whereas the values in July are 2.3%, 1.6% and 0.3%, respectively; and(4) G0 increases when the soil ice content is included in thermal diffusion equation, which improves the surface energy balance closure by 4.3%.

Conductivity properties of β-SiAlON ceramics

The thermal diffusivity and heat capacity of β-SiAION ceramics with different Z values （0.6, 1.5, 3.0） were measured by laser flash technique and differential scanning calorimetry （DSC）, respectively. The thermal conductivity of β-SiAION was calculated from thermal diffusivity, heat capacity and density and it decreased and then kept almost constant with increasing of temperature. Two different models representing effective thermal conductivity were established and the various parameters of these models were simulated based on the results from the present work. The fitted regression lines were in good agreement with the experimental values.

Size Dependent Heat Conduction in One-Dimensional Diatomic Lattices

We study the size dependency of heat conduction in one-dimensional diatomic FPU-β lattices and establish that for low dimensional material,contribution from optical phonons is found more effective to the thermal conductivity and enhance heat transport in the thermodynamic limit N →∞.For the finite size,thermal conductivity of 1D diatomic lattice is found to be lower than 1D monoatomic chain of the same size made up of the constituent particle of the diatomic chain.For the present 1D diatomic chain,obtained value of power divergent exponent of thermal conductivity0.428±0.001 and diffusion exponent 1.2723 lead to the conclusions that increase in the system size,increases the thermal conductivity and existence of anomalous energy diffusion.Existing numerical data supports our findings.