The document explains convection and radiation as mechanisms of heat transfer. Convection involves the movement of fluid masses due to temperature differences and density changes, while radiation transfers heat via electromagnetic waves without a medium. Additionally, it discusses specific heat capacities of water, air, and soil, highlighting water's higher capacity for heat absorption.

1. Explain how convection and radiation terms are included in the fundamental equation.
Solution
CONVECTION: Flow of heat through currents within a fluid (liquid or gas). Convection is the
displacement of volumes of a substance in a liquid or gaseous phase. When a mass of a fluid is
heated up, for example when it is in contact with a warmer surface, its molecules are carried
away and scattered causing that the mass of that fluid becomes less dense. For this reason, the
warmed mass will be displaced vertically and/or horizontally, while the colder and denser mass
of fluid goes down (the low-kinetic-energy molecules displace the molecules in high-kinetic-
energy states). Through this process, the molecules of the hot fluid transfer heat continuously
toward the volumes of the colder fluid.
For example, when heating up water on a stove, the volume of water at the bottom of the pot will
be warmed up by conduction from the metallic bottom of the pot and its density decreases. Given
that it gets lesser dense, it shifts upwards up to the surface of the volume of water and displaces
the upper -colder and denser- mass of water downwards, to the bottom of the pot.
Formula of Convection:
q = hA (Ts - T ?)
Where h is for convective heat transfer coefficient, A is the area implied in the heat transfer
process, Ts is for the temperature of the system and T ? is a reference temperature.
RADIATION:
It is heat transfer by electromagnetic waves or photons. It does not need a propagating medium.
The energy transferred by radiation moves at the speed of light. The heat radiated by the Sun can
be exchanged between the solar surface and the Earth's surface without heating the transitional
space.
For example, if I place an object (such as a coin, a car, or myself) under the direct sunbeams, I
will note in a little while that the object will be heated. The exchange of heat between the Sun
and the object occurs by radiation.
The formula to know the amount of heat transferred by radiation is:
q = e ? A [(?T)^4]
Where q is the heat transferred by radiation, E is the emissivity of the system, ? is the constant of
Stephan-Boltzmann (5.6697 x 10^-8 W/m^2.K^4), A is the area involved in the heat transfer by
radiation, and (?T)^4 is the difference of temperature between two systems to the fourth or
higher power.
Water absorbs the incoming solar Infrared Radiation because the frequency of the internal

2. vibration of the water molecules is the same frequency of the waves of the solar Infrared
Radiation. This form of Radiative Heat transfer is known as Resonance Absorption.
We humans feel the heat radiated by the Sun and other systems with a higher temperature
because our bodies contain 55-75% of water. The radiative energy inciding on our skin is
absorbed by the molecules of water in our bodies by Resonance Absorption. Just then, the
Infrared Radiation absorbed by our bodies leads to a more intense internal vibration of the water
molecules in our bodies and our bodies get warmer. However, in general, living beings possess
thermoregulatory systems that permit us to eliminate the excess of heat from our bodies,
maintaining a quasi-stable internal temperature (it is one of the homeostatic processes of
biosystems).
A Heat Sink is a system capable of absorbing heat from an object with which it is in thermal
contact without a phase change or a significant variation in temperature.
At Earth's location, the outer space, the gravity field (Guth. 1999.Pp. 29-31) and the false void
are heat sinks.
Water has a specific Heat of 4.190 kJ/Kg.K, while air has a specific heat of 1.0057 kJ/Kg.K, and
soil have a Specific Heat of 0.725 kJ/Kg.K.
Water has a Specific Heat higher than soil and air; then, the Thermal Capacity of water is higher
than the Thermal Capacity of the air and the soil. To a greater Thermal Capacity, a slower rate of
dissipation of heat.
The atmosphere and the soil don't maintain a load of heat for longer periods than water because
they have a specific heat capacity lower than water, so water absorbs more heat for inreasing its
temperature for a determined interval. For equal volumes (1Kg, for example), water absorbs
more heat than air or soil. The absorbed heat will be transformed into kinetic and potential
energy. A body with a high energy density will lose its inner energy slower than a body with a
lower energy density. For example, if you have ten dollars and your friend has five dollars, and
each one is obliged to spend one dollar per day, you will delay ten days to spend your money,
while your friend will delay only five days to consume his money.
In general, the soil and the air have independently 1/4 of the specific heat of water. For example,
the Specific Heat of Carbon Dioxide is 850 J/Kg