Question

levels of activity cui 22.9 An endurance athletic event is conducted when the conditions are extremely stressful, the dry-bulb temperature being 45 °C. One of the participants in the event, a male, is able to absorb 1.1 litre of water per hour through the gut, although he can lose water through perspiration faster than this if necessary. The latent heat of vaporisation of water at the participant's skin temperature is 2440 kJ kg$^{-1}$. (a) Determine the maximum rate at which he can reject heat by perspiration without becoming dehydrated. (b) The athlete has a surface area of 1.8 m$^2$ and his surface heat transfer coefficient, including convection and radiation, is 22 W m$^{-2}$ K$^{-1}$. During the endurance event his skin temperature is 37°C. Determine the rate of heat gain (or loss) due to convection and radiation alone, not including the effect of perspiration. (c) The table above shows the metabolic rate of the athlete doing different activities. Assume this is the same as the rate of production of thermal energy in his body. Determine the maximum sustainable metabolic rate for the athlete during the endurance event without any temperature rise. What is the most vigorous activity that could be sustained under these conditions? (d) Suppose the event is rescheduled for a cooler day. Again the athlete has sufficient water to perspire and evaporate 1.1 kg per hour and on this occasion he intends to run with a metabolic rate of 800 W. What is the maximum dry-bulb temperature at which he could do this sustainably, assuming his skin temperature is 37 °C?

levels of activity
cui
22.9 An endurance athletic event is conducted when the conditions are extremely stressful, the dry-bulb temperature being 45 °C. One of the participants in the event, a male, is able to absorb 1.1 litre of water per hour through the gut, although he can lose water through perspiration faster than this if necessary. The latent heat of vaporisation of water at the participant's skin temperature is 2440 kJ kg$^{-1}$.
(a) Determine the maximum rate at which he can reject heat by perspiration without becoming dehydrated.
(b) The athlete has a surface area of 1.8 m$^2$ and his surface heat transfer coefficient, including convection and radiation, is 22 W m$^{-2}$ K$^{-1}$. During the endurance event his skin temperature is 37°C. Determine the rate of heat gain (or loss) due to convection and radiation alone, not including the effect of perspiration.
(c) The table above shows the metabolic rate of the athlete doing different activities. Assume this is the same as the rate of production of thermal energy in his body. Determine the maximum sustainable metabolic rate for the athlete during the endurance event without any temperature rise. What is the most vigorous activity that could be sustained under these conditions?
(d) Suppose the event is rescheduled for a cooler day. Again the athlete has sufficient water to perspire and evaporate 1.1 kg per hour and on this occasion he intends to run with a metabolic rate of 800 W. What is the maximum dry-bulb temperature at which he could do this sustainably, assuming his skin temperature is 37 °C?

Added by Brent J.

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