Heat is a form of thermal energy that can move or transfer within an object, from one or more objects, or from an object to its surroundings, we can reduce the heat transfer or restrict the heat movement by the use of thermal insulation.
In this article, you will learn how heat transfer takes place in a refinery or industrial process plant, by what means heat can transfer, and what is required for the heat to transfer?
Mediums of Heat Transfer
Heat can travel from one place to another in three ways:
Convection
Conduction
Radiation
Convection occurs in liquids or gasses, whereas conduction occurs in solids, and radiation occurs through electromagnetic waves.
Understanding the Heat
To better understand heat as a concept, it is crucial to understand what heat is in its essential form. Heat is a form of thermal energy, and the temperature is the medium to measure the hotness or coldness of a surface or body.
You can measure heat in degrees Celsius (˚C), degrees Fahrenheit (˚F), or Kelvin (K). There are devices available to measure the temperature of a surface, some of the frequently used devices are as follows:
Whirling hygrometer
Contact thermometer
Dew point meter
Any surface with a temperature higher than its surrounding environment is hot, whereas any surface with a temperature lower than its surrounding environment is cold.
How heat travel
Since heat is a form of thermal energy, it can travel within an object, between one or more objects, or from an object to its surroundings. But heat can only begin to travel when temperature differences between the surfaces or its surrounding exist. In fact, when temperature differences are greater, the rate of heat transfer is faster.
Heat always transfers from the part that is hot to the part that is cold. Whenever two different temperatures exist, the heat transfers until it reaches thermal equilibrium.
Heat transfer example 1
An example of heat transfer can better illustrate the concepts discussed above. First, consider a cup of hot coffee is kept on a table in a room. The temperature of the hot coffee is 100˚C, and the normal room temperature is 21˚C. We can assume that it would only take a few seconds or minutes for the coffee’s temperature to turn colder.
This is a result of the temperature differences that exist between the coffee and the room, as the heat from the coffee in the cup transfers to the temperature of the surrounding room.
The heat transfer from the cup will only stop when the coffee’s temperature matches the room temperature, which is known as thermal equilibrium.
How heat transfer from piping and equipment in the refinery or process plant
Next, let's illustrate an example of how heat transfer takes place from piping or from the equipment of a refinery or industrial process plant.
It is customary to install a pipe or equipment in an oil refinery or industrial process plant outdoor. Let’s assume that the normal outdoor temperature ranges from 30˚C and 40˚C, and during the plant operation, the operating temperature of the piping or equipment will be approximately 570˚C.
What will happen without the use of Insulation
Thus, when the plant is in operation, the surface temperature of the pipe or equipment will be hotter than its surrounding temperature, and as previously mentioned, heat requires two different temperatures to move. Thus, the heat of the hot surface—in this case, the piping or equipment—will transfer to its surrounding environment as soon as the plant starts its operation.
A similar situation will occur when the piping or equipment has a lower surface temperature than the surrounding environment (ex. -10˚C). In this situation, the cold surface of the pipe or equipment will gain heat from the surrounding environment.
What is required to control the movement of heat
Moreover, when it is necessary to maintain or control the temperatures within a mechanical component, piping and equipment that carry fluid with temperatures that differ from their surrounding environment are insulated. All such surfaces are insulated using appropriate material and thickness to reduce the heat movement to a minimum.
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