Heat transfer analysis of a domestic,wood-burning, “heat-circulating” fireplace

Seeking to learn ways of efficiently employing wood-burning fireplaces to heat homes, we analyze in this paper the flow and heat transfer characteristics of a fireplace chimney which is provided with air flow in an annular jacket. Both parallel and counterflow cases of heat exchange between the flue gases and air are studied for two chimney heights. It is found that the heat-extraction rate is governed by the height of the chimney, the heat transfer conductance of the flue wall and the ratio of the heat capacities of flue gas and air. Some important quantitative observations of relevance in design are made from the predicted temperature and velocity profiles and total heat-extraction rate under different circumstances.     

Vitamin E as a universal antioxidant and stabilizer of biological membranes

The known literature data concerning the mechanisms of molecular action of vitamin E in biological membrane systems are reviewed. The role of vitamin E, possessing a broad range of biological activities, as a universal stabilizer of biological membranes in normal oxygen metabolism and peroxidation, and also in disorders of normal metabolism resulting in pathological alterations, has been discussed. The participation of vitamin E in redox reactions taking place in lipid media, its interaction with singlet oxygen, free fatty acids and enzyme systems are considered. Physiological effects of vitamin E and its ability to prevent numerous pathologies are also considered. Vitamin E was concluded to be a universal participant of antioxidant defence reactions in biological membranes, since it acts at all stages of membrane oxidative damage.