Units of Heat.
The unit of heat commonly used in the English system is the British thermal unit, or Btu, and is approximately equal to the quantity of heat that must be transferred to one pound of water in order that its temperature be raised one degree Fahrenheit. In laboratory work and throughout much of the world, the calorie is the common unit of heat. A gram calorie is the approximate quantity of heat that must be transferred to 1 gram (g) of water in order to raise its temperature by 1*C. The kilocalorie, sometimes called the kilogram calorie, is equal to 1000 gram calories.
The unit of heat commonly used in the English system is the British thermal unit, or Btu, and is approximately equal to the quantity of heat that must be transferred to one pound of water in order that its temperature be raised one degree Fahrenheit. In laboratory work and throughout much of the world, the calorie is the common unit of heat. A gram calorie is the approximate quantity of heat that must be transferred to 1 gram (g) of water in order to raise its temperature by 1*C. The kilocalorie, sometimes called the kilogram calorie, is equal to 1000 gram calories.
Now with Piping and Fabrication, we will go deeper and deeper! and with Heat and Temperature of Pipe continue.
The definitions above are indicated as being approximate because, over the temperature range from freezing to boiling points of water, different quantities of heat are required to produce a unit temperature change. For this reason, the calorie and the Btu have been defined in international units as
In most engineering work, it is sufficiently accurate to use 1 kg . cal = 3.968 Btu and 1 Btu = 0.252 kg . cal.
Units of Temperature.
The relative ‘‘hotness’’ or ‘‘coldness’’ of a body is denoted by the term temperature. The temperature of a substance is measured by noting its effect upon a thermometer or pyrometer whose thermal properties are known. The mercury thermometer is suitable for measuring temperatures from _39 to about 600_F. This limit may be extended to 1000_F if the capillary tube above the mercury is filled with nitrogen or carbon dioxide under pressure. High temperatures must be measured with thermocouples or optical pyrometers. The most commonly used thermometer scales are the Fahrenheit and the Celsius. Thermometer scales have as their bases the melting and boiling points of water, both measured at atmospheric pressure. The relation of the Fahrenheit and Celsius scales is as follows:
The relation between the two scales is
in which C is the reading on the Celsius scale and F is the reading on the Fahrenheit scale.
In certain calculations,