Numerical simulation of heat transfer properties of large-sized biomass particles during pyrolysis process.

During the pyrolysis process of large particles, the conduction between particles cannot be ignored. In the present work, a numerical simulation model for the pyrolysis of biomass particles was established, which takes into account the conduction within the particles. Based on this model, the temperature distribution inside the particle during the pyrolysis process was determined and the effects of particle size, moisture content, and gas velocity on heat transfer characteristics were analyzed. The results showed that the temperatures at different positions of the particles along the inflow direction were quite different, and the maximum temperature difference inside the particles was about 146.7 K for a particle diameter of 10 mm and a velocity of 0.2 m/s. During the pyrolysis process of biomass particles, there were two peaks of Nusselt number. The increase of moisture content prolonged the pyrolysis time. The pyrolysis. time of particles with moisture content of 15 % was about 1.5 times longer than that of dry particles when the particle diameter was 10 mm. Increasing the particle size decreased the difference between the two peaks and increased the time interval between the two peaks. Increasing the gas velocity can improve the heat transfer, but the effect of too high gas velocity on improving the heat transfer is limited. The present study is of great importance for a detailed understanding of the pyrolysis process of biomass particles.

[Preventive effect of trans-resveratrol on hypertension-induced cardiac hypertrophy in partially nephrectomized rats].

OBJECTIVE: To investigate the effect of trans-resveratrol on hypertension-induced cardiac hypertrophy and its potential mechanisms involving endothelin (ET), angiotensin II (AngII) and nitric oxide (NO). METHODS: Animal models bearing cardiac hypertrophy were replicated in male SD rats following partially nephrectomy (PNX). 10 mg/kg bw or 50 mg/kg bw of resveratrol was administered to rats by gavage, respectively, for 4 weeks. PNX control and sham-operation control (SHAM) were simultaneously established. Systolic pressure of rats was measured through tail at baseline and it, as well as heart weight, was measured after 4-week treatment. Serum ET-1 and AngII concentrations were determined using radioimmunological assay and NO using nitric acid reductase method. RESULTS: After 4-week treatment, animals in PNX control group had significantly higher systolic pressure and heart weight, higher ET-1 and AngII concentrations while lower NO concentrations, compared with those in SHAM group (P < 0.05). Rats treated with 50 mg/kg bw of resveratrol had significantly lower systolic pressure and heart weight, lower ET-1 concentrations while higher NO concentrations, compared with animals in PNX group (P < 0.05). CONCLUSION: Trans-resveratrol could protect against the increase of systonic pressure and subsequent cardiac hypertrophy in vivo, which mechanisms might, at least partly, involve with its modulation on NO, AngII and ET.