(a) The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram ale there in a 5.00-g peanut if the energy from burning it is transferred to 0. 500 kg of water held in a 0.100-kg aluminum cup, causing a 54.9-℃ temperature increase? Assume the process takes place in an ideal calorimeter, in other words a perfectly insulated container. (b) Compare your answer to the following labeling information found on a package of dry roasted peanuts: a sewing of 33 g contains 200 calories. Comment on whether the values are consistent.
(a) The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram ale there in a 5.00-g peanut if the energy from burning it is transferred to 0. 500 kg of water held in a 0.100-kg aluminum cup, causing a 54.9-℃ temperature increase? Assume the process takes place in an ideal calorimeter, in other words a perfectly insulated container. (b) Compare your answer to the following labeling information found on a package of dry roasted peanuts: a sewing of 33 g contains 200 calories. Comment on whether the values are consistent.
(a) The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram ale there in a 5.00-g peanut if the energy from burning it is transferred to 0. 500 kg of water held in a 0.100-kg aluminum cup, causing a 54.9-℃ temperature increase? Assume the process takes place in an ideal calorimeter, in other words a perfectly insulated container. (b) Compare your answer to the following labeling information found on a package of dry roasted peanuts: a sewing of 33 g contains 200 calories. Comment on whether the values are consistent.
During the winter, the inside of an average house is maintained at 20 °C, while the outside temperature is 0 °C. Assuming that the only mechanism of heat transfer is conduction, the walls are 10 cm thick and the heatconductivity of the walls is 0.5 W/(Km). a) Calculate the heat flux from the room to the surroundings in W/m2. b) To reduce the heat loss through the walls, the material should be changed to an insulator material. Thenew overall conductivity will be 0.1 W/(Km); the thickness of the walls is maintained. Calculate the reductionof the heat flux through the walls compared to the initial case.
It is important for the body to be able to cool itself even during moderate exercise. Suppose a 70kg man runs on a treadmill for 30min and at a (total) metabolic energy expenditure rate of 1000W.
Suppose the man is allowed to run without clothing, and in a room inwhich the temperature of the air, walls, floor, and ceiling are all equal to that of his skin temperature.
What is the net heat energy dissipated through radiative, conductive and convective heat transfer combined?
A)1800kJB)450kJC)1350kJD)0kJ
Solar radiation is incident on a 5 m2 solar absorberplate surface at a rate of 800 W/m2. Ninety-three percent ofthe solar radiation is absorbed by the absorber plate, whilethe remaining 7 percent is reflected away. The solar absorberplate has a surface temperature of 40°C with an emissivityof 0.9 that experiences radiation exchange with the surroundingtemperature of -5°C. In addition, convective heat transferoccurs between the absorber plate surface and the ambientair of 20°C with a convection heat transfer coefficient of7 W/m2∙K. Determine the efficiency of the solar absorber,which is defined as the ratio of the usable heat collected bythe absorber to the incident solar radiation on the absorber.
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