Newton’s Law of Cooling

Newton’s Law of Cooling is a useful and necessary law in the engineering world. It helps to answer questions such as how much time will it take before an object’s temperature reaches equilibrium with its environment? The law is mathematically expressed as: 

Q= h . A . (T(t) -Tenv)

Where Q is the heat lost from the body, A is the surface area of the body, T is the temperature of the object and t is time. Newton’s law of cooling can be applied to a variety of situations, mostly in engineering. It helps us to find out how much time it would take for an object with a known temperature to reach equilibrium with its environment. It involves basic concepts such as heat transfer (conduction/convection/radiation) resisting materials, thermal conductivity and mass diffusion. By applying this concept, we can determine what material or what thickness of a material must be placed between two objects so that they do not exchange thermal energy during contact.

What is Newton’s Law of Cooling?

Newton’s Law of Cooling is a law of nature which determines how fast or slow an object cools down. It states that the rate of heat transfer from a body to its surroundings is proportional to the difference between their temperatures and inversely proportional to their masses and the area over which they are in contact.

Process of Newton’s Law of Cooling:

Process of Heat is a form of energy that can be transferred from hot bodies to cold bodies. Heat transfer can either be conducted (via contact with solids, liquids, gases and plasmas), convective (in fluids) or radiative (visible light, infrared radiation etc.) based on the properties of the medium. Conduction occurs between solid objects in direct physical contact with each other while convection occurs when they are in liquids or gases. Radiation is more efficient at large distances where objects are not in direct contact with each other, and it can occur through a vacuum.

During conduction and convection heat transfer is proportional to both temperature differences between the surfaces and their surface areas. Heat transfer rates are greater in materials that have a high thermal conductivity (the ease at which they transmit heat), good thermal contact between surfaces and low thermal resistivity (the ability of a material to obstruct heat flow).

Heat can be transferred between objects by radiation, conduction and convection only when they are in contact. The rate of heat transfer depends on the temperature difference, area over which the two objects are in contact, their masses and their thermal conductivity. Heat transfer also depends on the mass of the object in contact with the other object and its thermal conductivity.

Heat is always transferred from a warmer body to a cooler one. When an object’s temperature is lower than the surrounding temperature, heat becomes trapped inside it and seeks the surface. The rate of heat flow will be proportional to:

Q = Heat Content / (T – Tenv)

Where T is the temperature difference, T env is the ambient (environmental) temperature and Q is heat lost from the body.

This law states that the rate of heat transfer from a body to its surroundings is proportional to the difference between their temperatures and inversely proportional to their masses and the area over which they are in contact.

Heat transfer is conducted by conduction, convection and radiation. Convective heat transfer occurs in fluids (water, air, and liquids that flow like a gas) while radiative heat transfer occurs in solids, liquids and gases. Conduction is more efficient when the mass of the object in contact with another object is low. Thermal conductivity of the objects can also alter their rates of heat transfer:

Q = Tc / (T – Tc) where Tc is the temperature difference then transferred between objects and Q is heat lost from the body.

Conclusion:

The article discusses how Newton’s Law of Cooling can be used to calculate the amount of time it takes for an object’s temperature to reach equilibrium with their surroundings. It also explains the concept of how heat flow can be altered and influenced by mass, temperature difference, thermal conductivity, thermal resistivity and area.