Users' questions

What is meant by heat transfer coefficient?

What is meant by heat transfer coefficient?

Heat transfer coefficient is a quantitative characteristic of convective heat transfer between a fluid medium (a fluid) and the surface (wall) flowed over by the fluid. This characteristic appears as a proportionality factor a in the Newton-Richmann relation.

How do you calculate radiative heat transfer?

The rate of heat transfer by emitted radiation is determined by the Stefan-Boltzmann law of radiation: Qt=σeAT4 Q t = σ e A T 4 , where σ = 5.67 × 10−8 J/s · m2 · K4 is the Stefan-Boltzmann constant, A is the surface area of the object, and T is its absolute temperature in kelvin.

Do you want a higher or lower heat transfer coefficient?

Assuming the heat transfer surface and temperature difference remain unchanged, the greater the U value, the greater the heat transfer rate. In other words, this means that for a certain heat exchanger and product, a higher U value could lead to shorter batch times and increased production/revenue.

What is the definition of radiation as a heat transfer?

Radiation heat transfer is the energy that is emitted by matter in the form of photons or electromagnetic waves. The electromagnetic waves appear in nature for wavelength over an unlimited range. Radiation with wavelength between 0.1 and 100 μm is in form of thermal radiation and is called radiation heat transfer.

What is the best example of heat transfer by radiation?

The heating of the Earth by the Sun is an example of transfer of energy by radiation. The heating of a room by an open-hearth fireplace is another example. The flames, coals, and hot bricks radiate heat directly to the objects in the room with little of this heat being absorbed by the intervening air.

How does heat from a radiator transfer?

A radiator uses radiant energy to transfer heat to the air through electromagnetic waves, similar to the heat from a stove or an open fire. But the bigger heat contribution of a radiator is through convection.

How does a fire transfer heat by radiation?

In a fire, the heated air rises and transfers heat to other areas as it spreads out. Radiation involves the transfer of heat by rays or waves in all directions from the source of the burning. In a fire, heat will radiate in all directions until it strikes an object. The radiant heat will then be passed to the object by conduction.

What is the formula for heat transfer rate?

Heat transfer rate by conduction is given by Fourier law of heat conduction. The formula is. dQ = k*A*dT/dx. Where, k- thermal conductivity of the material.