The unit of work is joule, J, which is defined as the amount of work done when a force of 1 newton acts for a distance of 1 m in the direction of the force.ġ J = 1 Nm Example - Work due to Gravitational Force The work done by a force 100 N moving a body 50 m can be calculated as L = length or distance the pressurized area is moved by the applied force (m) Example - Work done by a Force Work = Applied pressure x Displaced volume Work can also be described as the product of the applied pressure and the displaced volume: Work = Applied force x Distance moved in the direction of the force The amount of mechanical work done can be determined by an equation derived from Newtonian mechanics Work and energy are from a technical viewpoint the same entity - but work is the result when a directional force (vector) moves an object in the same direction.
The amount of heat needed to heat a subject from one temperature level to an other can be expressed as:ĭT = temperature difference between hot and cold side (K)Ĭonsider the energy required to heat 1.0 kg of water from 0 oC to 100 oC when the specific heat of water is 4.19 kJ/kg oC: Water has a large specific heat of 4.19 kJ/kg oC compared to many other fluids and materials.Īmount of Heat Required to Rise Temperature The SI units of specific heats are J/kgK (kJ/kg oC).
The specific heat represents the amount of energy required to raise 1 kg of substance by 1 oC (or 1 K), and can be thought of as the ability to absorb heat. Constant-volume and constant-pressure heats can be said to be equal. Unless the pressure is extremely high the work done by applied pressure on solids and liquids can be neglected, and enthalpy can be represented by the internal energy component alone. The change in internal energy with respect to change in temperature at fixed volume is the Specific Heat at constant volume - c v. The change in internal energy with respect to change in temperature at fixed pressure is the Specific Heat at constant pressure - c p. The enthalpy - or internal energy - of a substance is a function of its temperature and pressure. Specific heat for common products and materials can be found in the Material Properties section. Never use tabulated values of heat capacity without checking the unites of the actual values! Specific heat may be measured in J/g K, J/kg K, kJ/kg K, cal/gK or Btu/lb oF and more. Specific heat (= specific heat capacity) is the amount of heat required to change temperature of one mass unit of a substance by one degree. the amount of heat required to change the temperature of the whole system by one degree.More specifically enthalpy is the sum of internal energy and work done by applied pressure.
The term relates to the total energy due to both pressure and temperature of a fluid (such as water or steam) at any given time and condition. The SI-unit commonly used is J/kg or kJ/kg. Specific Enthalpy is a measure of the total energy in a unit mass.
The SI units for heat flow is J/s or watt (W) - the same as power. Heat-transfer as result of temperature difference alone is referred to as heat flow. more about degrees Celsius and degrees KelvinĪ calorie is defined as the amount of heat required to change the temperature of one gram of liquid water by one degree Celsius (or one degree Kelvin).Other units used to quantify heat are the British Thermal Unit - Btu (the amount of heat to raise 1 lb of water by 1 oF) and the Calorie (the amount of heat to raise 1 gram of water by 1 oC ( or 1 K)). heat will transfer from a warm body with higher temperature to a colder body with lower temperature.The SI-unit of heat - or energy - is joule (J).
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