人的体温是由“下丘脑”中特殊神经细胞组织控制的,它对人体体温的变化很敏感,当下丘脑温度低于
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3Cmo%3E%C2%B0%3C%2Fmo%3E%3Cmtext%3EC%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
时,人体发热机制(如血管收缩、燃烧脂肪等)就会活跃起来.此时实现的能量转化是
.当下丘脑温度高于
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3Cmo%3E%C2%B0%3C%2Fmo%3E%3Cmtext%3EC%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
时,人体散热机制(如出汗等)就会活跃起来,已知
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3Cmo%3E%C2%B0%3C%2Fmo%3E%3Cmtext%3EC%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
时蒸发
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E20%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
克汗水所需要的能量为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E4800%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
焦.这时体表的汗水发生了汽化(即蒸发),这属于通过
(选填“做功”或“热传递”)的方式减少身体的内能.现有一中年人漫步行走时,每秒钟体内产生的热量为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E35%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
焦,而此时人体通过传导、辐射等方式(不包括出汗)产生的散热功率只有
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E33%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
瓦,他的体表温度会
.因此还要通过出汗的方式才能保持
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3Cmo%3E%C2%B0%3C%2Fmo%3E%3Cmtext%3EC%3C%2Fmtext%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
的体温不变.那么此人漫步行走
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmath%3E)
小时出汗约
克.