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1. Radiation makes it impossible to stand close to a hot lava flow. Calculate the rate of heat transfer by radiation from 2 m² of 1197 deg C fresh lava into 30 deg C surroundings, assuming lava's emissivity is 0.8. o=5.67X10-8 J/(s m2 °C) Use the sign convention for heat leaving or entering the system. = = 423022.8 kW

1. How much heat transfer (in kilocalories) is required to thaw a 0.3-kg package of frozen vegetables originally at 0°C if their heat of fusion is the same as that of water? Heat of fusion for water is 79.8 kcal/kg. Q= V kcal

1. Thermography is a technique for measuring radiant heat and detecting variations in surface temperatures that may be medically, environmentally, or militarily meaningful. (a) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.2 deg C compared with that at 32.5 deg C, such as on a person's skin? % Increase = % (b) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 33.7 deg C compared with that at 20 deg C, such as for warm and cool automobile hoods? % Increase = %