Temperature Thermal Environment Research Articles

Experimental Research on Heat Transfer and Strength Analysis of Backfill with Ice Grains in Deep Mines

In deep mines, two urgent problems are a high temperature thermal environment and solid waste. Filling the goaf with slurry mixed with ice grains is an effective way to solve these two problems simultaneously. The thermal property and mechanical property of the ice-added backfill have a great influence on the cooling effect in the deep mine. In this study, an experimental facility for measuring the temperature distribution of ice-added backfill slurry was established, and the temperature of backfill slurry with different proportions was measured. Then, the thermal properties of temperature distribution and cooling capacity and the mechanical property of uniaxial compressive strength of the backfill specimens were analyzed, and the results indicated the following: firstly, the cooling capacity of ice-added backfill specimens is negatively related with the slurry concentration C and is positively related with the ice-water ratio Ω; secondly, the strength of backfill specimens is affected by the slurry concentration C and ice-water ratio Ω by a contrary law compared to the cooling capacity; thirdly, ice-added backfill slurry with an ice-water ratio Ω of 1:1 has the best mechanical property after solidification. The effects of the slurry concentration and ice-water ratio on the thermal and mechanical properties were analyzed, and the results indicated that the optimum proportion of ice-added backfill slurry is a slurry concentration of 74% and an ice-water ratio of 1:1 in the present research range. This study is significant for the deep mine cooling method with ice-added backfill.

Thermal vibration characteristics of fiber-reinforced mullite sandwich structure with ceramic foams core

This paper researched a sandwich structure composed of fiber-reinforced mullite matrix composite face sheets and ceramic foams elastic layer subjected to high temperature and large gradient thermal environment. The vibration characteristics of the hybrid structure with free–free boundary condition were investigated in room and high temperature thermal environment by both experimental means and finite element method (FEM). Finite element models were established to estimate the vibration characteristics of the hybrid sandwich structure. Modal tests by hammer impulse method and exciter were carried out in room temperature environment to get the natural frequencies and corresponding modal shapes and damping loss factors. Then the exciter experiment was performed with the same setups as room temperature test to get the temp-varying vibration characteristics under high temperature thermal loads. The numerical simulation results agree well with the experimental results. The natural frequencies and damping loss factors of the hybrid sandwich structure show steady state with the temperature increased up to 800°C and so large gradient. Correspondently, the structural stiffnesses and damping characteristics of such composite structures keep excellent performance in thermal environment.

On melting of the subducted oceanic crust: Effects of subduction induced mantle flow

Based on petrological and geochemical arguments, it is possible that arc magma is derived from subducted oceanic crust. In this paper, regional thermal models have been constructed to study the feasibility of melting cold subducted oceanic crusts at shallow depth (i.e. at depths of about 100 km) by a dynamic mantle. Calculated results suggest that plate subduction will generate an induced flow in the wedge above the subducting slab. This current continuously feeds hot mantle material into the corner and onto the slab surface. A high temperature thermal environment can be maintained in the vicinity of the wedge corner, immediately beneath the over-riding plate. Our regional models further demonstrate quantitatively that production of local melting is possible just about 30 km down dip from the asthenosphere wedge corner. Additional geological processes such as reasonable amounts of shear heating and minor dehydration (which will lower the local melting temperature) will further increase the probability of melting a cold subducted oceanic crust at shallow depth.