Through the burning of food calories your body maintains a c

Through the burning of food calories, your body maintains a constant temperature of around 99 degree F. As this is typically a higher temperature than the environment, you transmit heat to your surroundings, raising the total entropy of you + your environment. On very hot days, when the environment is, say, 100 degree F your default cooling mechanism to maintain your body temperature is sweating. The sweat evaporates into the environment taking with it the latent heat of vaporization and cooling your skin from 100 degree F to a lower temperature than the environment. Explain why this process of heating the environment while cooling you off does not violate the 2^nd law of thermodynamics (or does it)?

Solution

While cooling the body in summer it acts like heat pump.

It takes an amount heat Q1 from a cold body and an amount of work W is done on it by the surroundings and the total energy Q1= Q2 +W is supplid to the hot body in the form of heat.

The general statement of second law is

It is not possible to design a heat engine which works in cyclic process and whose only result is to to take heat from a body at a single temperature and convert it to completely into mechnaical work.

Claussius statement of the second law states

It is not possible to design a refrigerator which works ina cyclic process whose only result is to transfer heat form a clod body to a hot body.

Work is done to evaporate the sweat and soem amount of heat is rejcted to the enviroment increasi9ng the entropy, thus there is no violatio0n the sencod law of themodunamics.