Fuel efficiency and performance of traditional and innovative cookstoves

Fuel efficiency and other cookstove performance parameters have been evaluated in an attempt to progress toward more efficient stoves for a particular locale, to develop and test methodologies for analysing cookstove fuel economy, and to gain insights into the performance of woodburning cookstoves in general. In the first part of this study, fuel consumption and efficiency were measured during the preparation of meals in 13 households. It was found that fuel consumption averages 3·6 kg/meal (s=2·1 kg/meal) and that efficiency averages 5·9% (s=2·2%). The use of aluminium rather than clay pots correlates with higher than average efficiencies. The magnitude of the various cooking energy losses was estimted to point out the opportunities for increasing fuel efficiency. While no particular energy loss mechanism dominates, the more significant energy losses are (i) heating of excess air, (ii) heat carried away by the combustion products, (iii) heating of the stove body and floor, (iv) energy contained in the charcoal residue, and (v) cooking water evaporation. Techniques for reducing these energy losses are suggested. Tests comparing the efficiency of traditional cookstoves and cookstoves containing a flue, chimney, and tightly fitting pots (the Hyderabad stove design) were then carried out. The Hyderabad cookstoves did not prove to be more fuel-efficient than the traditional stove when a means for controlling the draft or regulating the heat input rate to the pots is not provided. When the Hyderabad stove is equipped with a damper and recessed pots, a fuel savings of the order of 30% is realized in the laboratory. The innovative Hyderabad stove still requires field testing and user evaluation. This limited series of experiments suggests that new woodburning cookstoves should be carefully designed, constructed and operated.     

Thermal conductivity of Freon-218

The thermal conductivity of Freon-218 is investigated experimentally in a wide region of the parameters. Reference tables of thermal conductivity are compiled.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 2, pp. 244–248, February, 1980.     

A delayed reward strategy for large-scale motivation of safety belt use: A test of long-term impact

An incentive program applicable for communitywide motivation of safety belt use was implemented at a large industrial complex. After four weeks of daily baseline observation of drivers' shoulder belt usage at two entrance/exit gates during employees' afternoon departure, an incentive intervention was implemented at only Gate 1, where it was impossible to stop vehicles and immediately reward safety belt wearing. Instead, the employees were informed via signs, posters, and newspaper articles that a winning license plate number would be randomly selected each day from among those vehicles exiting Gate 1 whose drivers were wearing shoulder belts. Winners were offered the choice of two university basketball tickets or meals for two at a local restaurant. Shoulder belt observations continued daily at both gates throughout the three-week incentive intervention, and for three long-term follow-up phases over the subsequent eleven months. The incentive intervention influenced substantial increases in shoulder belt use (from a mean percentage of 6.3% belt usage during baseline to 23.1% during the incentive period); and affected some long-term impact (i.e. mean USE = 16.3% after one month, 15.8% after three months, and 11.0% after ten months).