Papers by Keyword: Heating Rate

Abstract: The entransy efficiency expression of the absorption heat pump systems was defined in this paper, combined with the concept of the entransy and based on the model of a four temperature level absorption heat pump cycle. The relationship between the heating coefficient of the absorption heat pump and heating rate with the changes of the entransy efficiency was deduced. Numerical example was introduced to analysis the impactions of the entransy efficiency on the absorption heat pump systems. The results show that the heating coefficient increases with the growth of entransy efficiency, the entransy efficiency and the heating rate becomes larger when the value u gets larger, but the heating coefficient gets smaller. The heating rate decreases with the growth of the heating coefficient, the value u has more impaction on the heating rate when the heating coefficient remains constant.

Abstract: The effect of heating rates on the premelting of grain boundary (GB) is investigated by the phase field crystal method. The microstructure evolution of premelting under different heating rates are discussed, and the film width of GB is quantitatively calculated in terms of the excess mass method. Results show that the liquid film appears as the melting point () is approached from below and that the film thickness is affected by heating rate. In heating process, at the same temperature (close to), the liquid film width is larger when the temperature increases with lower rate. In insulation process, the liquid film thickness increase until to its equilibrium value with holding time prolonging. For low-angle GBs, the higher heating rate the system has during heating stage, the lager equilibrium value of liquid film will be reached during insulation stage. For high-angle GBs, the liquid film thickness has the same equilibrium value during the insulation process although the heating rate is different during heating process.

Abstract: In the process of pressurized coal gasification, coal particles experience rapid devolatilization to become chars, which react with H₂O and CO₂. The characteristics of the char play an important role in the gasification research. Hence acquisition of coal char fitting real situation is demanded. The article uses PDTF system to produce coal char at high heating rate under pressurized conditions, and char morphology and pore structure are analyzed.

Abstract: The technique of combustion reaction and quick pressing was adopted to prepare dense nanocrystalline ceramics. The densification process of magnesia compact with a particle size of 100 nm was investigated, under the applied pressure of up to 170 MPa, and the temperature of 1740–2080 K with ultra-high heating rate of above 1700 K/min. As a result, pure magnesia ceramics with a relative density of 98.8% and an average grain size of 120 nm was obtained at 1740 K and 170 MPa, while the ones with decreased relative density and increased grain size were produced under the increasing temperature and the identical pressure conditions. The results indicated that grain growth of the nanocrystalline magnesia was effectively restrained by the combined effect of the ultra-high heating rate and the high pressure. Moreover, under the particular sintering conditions, there existed an appropriate temperature range for the preparation of dense nanocrystalline magnesia, and the excessive temperature would not only exaggerate grain growth but also impede densification.

Abstract: The effects of heating rate and prior cold work on the development of dual-phase steel microstructures in three low carbon steels were evaluated with samples processed on a Gleeble 3500 thermomechanical processing simulator. The nominally 0.2 wt pct carbon steels included a plain carbon steel and modified alloys incorporating higher manganese contents, boron additions, and microalloy additions. Each alloy was prepared with two different cold rolled reductions. Heating rates from 1 to 1000 ^oC/s were selected to span the rates typically experienced in conventional furnace heat treating up to rates for induction heating. Critical transformation temperatures were obtained from dilatometric curves. Dual-Phase microstructures after heat treatment with different heating rates were compared. Transformation temperatures decreased with an increase in cold work and increased with an increase in heating rate. The steels with higher manganese and carbon additions exhibited lower Ac₃ values across all heating rates and the steels with higher silicon higher Ac₁ temperatures across all heating rates. Ac₁ increased less than Ac₃ with increasing heating rate. The increase in transformation temperatures between 100 and 1000 °C/s was smaller than values exhibited over other increments in heating rate, and decreased in one steel; contributing factors were identified for this behavior.

Abstract: Pyrolysis characteristics of edible mushroom bran with different heating rates were investigated applying a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared (FTIR) spectrometer. The pyrolysis experiments were performed up to 1073 K at heating rates of 10, 20, 30 K/min in a dynamic nitrogen flow of 20 ml/min. The results show that important differences on the pyrolytic behavior and product distributions are observed when heating rate is changed. At the lower heating rates, the starting temperature, final temperature of pyrolysis and the maximum rates of mass losses were relatively low. When the heating rate was increased, the starting temperature, final temperature of pyrolysis and the maximum rates of mass losses also increased. There have three stages: the first-stage was from the temperature of 20 to110°C with a weight loss of 12.33~14.36%; the second-stage was from 220°C to 400°C with a weight loss of 45.09~49.59%; the third stage was from 400 to 800°Cwith a weight loss of 15.11%~ 15.34%. The main pyrolysis vapour was CO₂, phenol , and significant amounts of H₂O, hydrocarbon, carbonyl compounds and acids.

Abstract: The paraffin, pre-treated paraffin and hydroxyl-terminated polybutadiene (HTPB) were measured by Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG) in different conditions. Thermal degradation characteristics of the paraffin, pre-treated paraffin and HTPB were studied; Influences of different pressure and different temperatures on thermal degradation characteristics of pre-treated paraffin were analyzed. Experiments show that the decomposition temperature of pre-treated paraffin is higher than that of the untreated paraffin, but lower than that of HTPB; the initial reaction temperature, the reaction exothermic peak temperature and the reaction heat release of pre-treated paraffin were all affected by pressure and heating rate; Kinetic parameters of pre-treated paraffin in oxygen atmosphere were calculated.

Abstract: Lots of basic analyses carried on YJOS (Yaojie oil shale) and LKOS (Longkou oil shale) consist of proximate analysis, ultimate analysis, XRF analysis and shale oil yield in aluminum retort. Besides, TGA are used on YJOS, LKOS and shale oil, gas chromatographic analysis is used on retorting gas. The results show that LKOS and YJOS have the same hydrogen-to-carbon ratio, but LKOS has higher volatile component and its oil yield in aluminum retort is much higher than YJOS. Ca content in LKOS is much higher than YJOS, however, Al and Fe content in LKOS are lower than YJOS. Two kinds of shale oil after destructive distillation have similar composition and relative content, in addition, they all produce more low boiling point distillates, combustible component of their destructive distillation gas are H₂ and CH₄, the second are CO and C₂H₆. Aluminium retort experimental findings, The carbonization temperature is the main influence factor on oil shale destructive distillation process in aluminum retort. Residence time has small influence on shale oil yield but need to choose appropriate heating rate and particle size. Best carbonization parameters of LKOS in aluminum retort: Temperature 500~550°C, heating rate 5°C/min, particle size 2~4mm, Residence time 10~20min;the best parameters of YJOS: Temperature 500~550°C, heating rate 5°C/min, particle size0.2~0.9mm, residence time 10~20min.

Abstract: The effects of heating rate, heating temperature and cooling rate on the microstructures and mechanical properties of four pipeline steels for high frequency electric resistance welded pipe have been studied by using a Gleeble-3500 thermo-mechanical simulator. The results show that the heating rates have an effect on austenizing phase transformation temperature (A_c1 and A_c3). It shows that there is a linear relationship between heating rate and austennizing temperature (A_c1 and A_c3) in the range of tested heating rate. With the heating temperature increasing, the strength property goes up, on the contrary, the strength begins to go down when the heating temperature exceeds 900 °C, then a lowest strength point appears on 925 °C in the testing scope. As the further increase of the heating temperature, the strength goes up again. Moreover, the cooling rate has a great effect on the microstructure and the mechanical properties. With the decrease of cooling rate, the strength decrease significantly, meanwhile, the microstructure becomes coarse, even the banded structure can be found. As the conclusion, the optimum heating temperature is 950 °C, and cooling rate is from 8.5 to 13 °C/s.

Abstract: The effects of heating rate on the preparation, characterization, pore-forming mechanism and bloating mechanism of sludge ceramics were investigated. The experimental results indicated that physical properties of SSC were highly dependent on heating rate. SSC with higher expansion rate and lower water absorption could be obtained as the heating rate was between 4 °C/min and 5 °C/min. Porosity and expansibility of SSC were closely related to the heating rate. The heating rate could affect the relationship between the forming rate of gas and the forming rate of glass phase, and further influenced the bloating phenomenon of SSC.