EFFECT OF POT THERMAL MASS ON THE COOKING TEMPERATURE AND TIME OF COOKSTOVE

Abstract

One of the major losses of heat from cooking stoves is through the gap between the inner edge of stove top and outer bottom of the pot, which is exposed to the surrounding air. In this study, design and construction of insulated stoves and pot rings were done in order to accommodate various sizes of pots and minimize the heat losses through the gap. The design improvement of the stove focused on the provision of insulation with 4 cm thickness and from mixture of 25% gypsum and 75% wood Ash. In the study, five pot of different mass of 522.5,560,664,828 and 894 gm with outer diameters of 18, 20, 22, 24 and 26 cm were used, respectively. Four of them had insulated pot-rings of 2cm thicknesses. For comparison, a control stove (CS) without pot ring was also used. Three parameters (time of onset of cooking or time to initially reach 75oC (ti)), maximum temperature (Tmax) and effective cooking time (T ≥ 75oC) (Δt)) were used for comparison. The comparisons were made graphically (using MATLAB software and Microsoft excel) and using one-way ANOVA. Stove body, Smoke outlet and ring body temperatures were also additionally tested. ANOVA tests showed significant differences (at p = 0.05 level) between controlled and the four stoves in terms of early initiation of cooking time and length of effective cooking time. The controlled stove (CS stove with 18 cm pot without ring), reached onset of effective cooking temperature in 12.4 minutes, The stoves with 20 cm pot, 22 cm pot and 24 cm pot with rings showed poor performance in terms of onset of cooking temperature which was 25.6, 23.2 and 20 minutes, but length of effective cooking time of 103.2, 113.2 and 112.4 minutes were observed, respectively. All of the stoves reached maximum temperatures regardless of their pot thermal mass and cooking time. The stove of 26 cm pot with ring exhibited the earliest initiation of cooking of 17.4 and the length of effective cooking of 97.2 minutes and maximum cooking temperature of 94.2 0C, hence it was better in terms of combined performance ti ,Δt and Tmax than the rest. The results obtained from this study shows that pot thermal mass have little influence on the onset of cooking and effective cooking time. However, the use of pot rings is not recommended for fast cooking since they delayed onset of cooking