British thermal unit defined

Heat is measured in term.s of the calorie, defined as the amount of heat necessary to raise the temperature of 1 gram of water at a pressure of 1 atmosphere firom 15 to 16 °C. This unit is sometimes called the small calorie, or gram calorie, to distinguish it from the large calorie, or kilocalorie, equal to 1000 small calories, which is used in nutritional studies. In mechanical engineering practice in the United States and the United Kingdom, heat is measured in British thermal units (Btu). One Btu is the quantity of heat required to raise the temperature of 1 pound of water 1 ° F and is equal to 252 calories. 

Saturated and Dry Btu Saturated British thermal unit (Btu) is the heating value that is detected when gas is saturated with water vapor. This state is defined as the condition when the gas contains the maximum amount of water vapor at base ambient conditions. Dry Btu is the heating value when the gas is dry. 

A coal is classified as high-sulfur by the United 8tates Department of Energy if it contains more than 763 g of snlfnr per nnit. A unit is defined as the amonnt of coal needed to produce 1.0 X 10 British thermal units (BTUs) of heat. If a unit of coal containing 768 g of snlfnr is bnmed, how much sulfuric acid (H28O4) will be produced ... 

Energy is measured in terms of its ability to perform work or to transfer heat. Mechanical work is done when a force / displaces an object by a distance d w =/ x d. The basic unit of energy is the joule. One joule is the amount of work done when a force of 1 newton acts over a distance of 1 m thus 1 J = 1 N-m. The newton is the amount of force required to accelerate a 1-kg mass by 1 m/sec2, so the basic dimensions of the joule are kg m2 s 2,Thc other two units in wide use, the calorie and the BTU (British thermal unit), are defined in terms of the heating effect on water. Because of the many forms that energy can take, there are a correspondingly large number of units in which it can be expressed. A few of these are summarized in Table 1. 

British thermal unit (Btu) - A non-SI unit of energy, equal to approximately 1055 J. Several values of the Btu, defined in slightly different ways, have been used. 

BRITISH THERMAL UNIT, (BTU) - The Btu is defined as the heat required to raise the temperature of a pound of water from 59° to 60°F. 

As we explained the Btu (British thermal unit) in Chapter 11, one Btu is formally defined as the amount of thermal energy needed to raise the temperature of 1 lb of water by 1°R The calorie is defined as the amount of heat required to raise the temperature of 1 g of water by 1°C. And as you may also recall from our discussion in Chapter 11, in SI units no distinction is made between the units of thermal energy and mechanical eneigy, and therefore the units of thermal energy are defined in terms of fundamental dimensions of mass, length, and time. In the SI system of units, the joule is the unit of energy and is defined as... 

British thermal unit (Btu) The Imperial unit of heat, being originally the heat required to raise the temperature of lib of water by 1°F. 1 Btu is now defined as 1055.06 joules. 

The unit of energy called the joule is equal to 1 watt-second, or 10 million ergs, or about 0.000948 British thermal unit. The British Thermal Unit, in science and engineering, is a unit measurement of heat or energy, usually abbreviated as Btu or BTU. One Btu was originally defined as the quantity of heat required to raise the temperature of 1 lb (0.45 kg) of water from 59.5 F (15.3 C) to 60.5 F (15.8 C) at constant pressure of 1 atmosphere for very accurate scientific or engineering measurements, however, this value was not precise enough. The Btu has now been... 

British thermal unit (Btu) (9.1) A unit of energy defined as the amount of energy needed to raise the temperature of 1 lb of water by 1°E... 

Specific heat (1832) n. Strictly, specific heat is the ratio of the heat capacity of a substance to that of water at 15°C. In traditional cgs and English units, the heat units (calorie and British thermal unit) were defined by the heat capacity of water, making that of water at room temperature closely equal to 1.00 in either system. Thus, for other materials, specific heat and heat capacity were numerically equal. This fact led to the use, still ongoing, of specific heat when the property meant was heat... 

In the SI system energy is given in joules (J) or kilojoules (kJ). Energy is also expressed in btu (British thermal unit) or cal (calorie). The g calorie (abbreviated, cal) is defined as the amount of heat needed to heat 1.0 g water 1.0°C (from 14.5°C to 15.5°C). Also, 1 kcal (kilocalorie) = 1000 cal. The btu is defined as the amount of heat needed to raise 1.0 lb water 1°F. Hence, from Appendix A. 1,... 

Calorie is defined as the quantity of heat when 1 g of water is heated or cooled by one unit of temperature. BTU, British thermal unit, is the quantity of heat that when transferred can effect a one degree Fahrenheit, F, change in one pound of water. The SI unit of energy is the joule. One joule equals 1 newton-meter, N.M. 

British thermal unit (Btu) A unit of measure used to define energy. 

Table of Conversion Factors Following the notation in Landolt-Bornstein [7], values which have been fixed by convention are indicated by a bold-face last digit. The conversion factor between calorie and Joule that is given here is based on the thermochemical calorie, calthch. and is defined as 4.1840 J/cal. However, for the conversion of the Internationale Tafelkalorie , caliT, into Joule, the factor 4.1868 J/cal is to be used [1, p. 147]. For the conversion factor for the British thermal unit, the Steam Table Btu, BTUst. is used [1, p. 95]. ... 

Thermal Conductivity. The quantity of heat a material is capable of passing per second through a specimen of unit cross-sectional area and unit length for a temperature difference of one degree is defined as the thermal conductivity. In the SI system heat is in joules, cross-sectional area is one square meter, length is one meter, and the temperature difference is one kelvin. In the English system the dimensions are in feet, the temperature difference is in Fahrenheit degrees, and the heat quantity is in British thermal units (Btu). 

If the metal specimen does not break after impact, then it absorbed the energy of impact, which defines its toughness. We wiU discnss tonghness later. The comparable impact energy nsed in the U.S. Customary system is the ft-lbf. The unit ft-lbf can be nsed as an energy unit or as a bending moment of torque. The thermal unit in the U.S. Customary system is the British Thermal Unit, or BTU. For reference, 1 BTU approximately equals 1055 Joules, or 1.055kJ (kilojoules). 

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