![]() Almost all gas energy is measured in Therms or Million BTU's (MBTU).Īs these are all units of energy they can be converted from one unit to another. Almost all electric is measured in units of kWhr of energy. Yet another unit is KWhr (Kilo-Watt-Hour). The JOULE (J) is the most commonly used unit of energy but is so small that KiloJoules (kJ) is the more commonly used engineering-unit for energy. Electric cars and Hybrids often have a dash-display for kW. Brake horsepower ( bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox and drive train. Because the Watt is a small unit power of a device is rated in kW or BTU/hr. higher power can make an automobile accelerate faster, make a reaction go faster, and so on. Generally speaking, power is the rate at which you can do something, e.g. Power is oomph! A more powerful device will be able to convert the same amount of energy faster ( speedier) than a less powerful device. ![]() in a second). Devices are rated by their power. What is Power: Power is the amount of energy that is converted Regardless of the base-state, the change-amount will be the same for the energy exchanged because energy is conserved. the base-state could be the room-temperature and/or room-pressure such as 0K, 25°K, 72☏or 278K or the melting point of a known pure substance. This is because an energy exchange is referenced always to an arbitrary base-state of your choice. The amount of Energy (used/exchanged) is a relative quantity. The main reason for energy conservation stems from the desire to conserve the quality of energy (not the quantity). Objects can be of a phase called solid, liquid gas, plasma or in a supercritical condition or a two or more phase mixture.Įnergy is conserved - Ywa this is the First-law of Thermodynamics (theconservation of energy is a consequence of Emmy Noether's theorem on symmetry). But what does it mean when we want to consever energy? When used the energy is conseved but the quality degrades. *We use objects and cotrol volumes as terms that are interchangeble in this tutorial. The total energy (internal plus mechanical) is given the symbol E. The internal energy is given the symbol U. Often the external energy is called mechanical energy and sometimes also PV energy. The energy of an object is both internal (microscopic), like the vibrational energy of molecules or external (macroscopic) energy like kinetic or potential energy. There are many measurable properties such as like P (Pressure), V (volume) and T (temperature) which also are used for defining energy. Most objects* have a mass and energy associated with them. Energy exchanges for carrying out an objective for a process can occur by the transfer of Work, Heat or Mass, between a system and its surroundings or vice-versa. In other units we can say that on a gloabal scale, humans use about more than 500EJ's per year (1EJ = ~0.947 Quad). The estimate is that we use more than a hundred-billion Planck units of energy every year. In the Physics literature, natural units are used for energy, namely the Planck energy unit (E p) which is equal to 1.956 x 10^9 J (about 2 Billion Joules). Units: Energy is commonly measured in Joules (J). ![]() What happens to energy when it is employed for an objective? Energy degrades when energy is used for an objective. However the amount of energy is unchanges. Objective: A change in the volume (or shape), chemistry, temperature or density of an object of interest is a possible objective. The task is always to cause a change i.e. The concept of Energy (or more appropriately the concept of the exchange of Energy) is related to the latent ability to perform a task called work, transfer mass or transfer heat. Often encounter power and energy in our daily lives. (The Boiler-BHP power unit is a bit confusing becasue BHP could be confused with brake-horsepower (b hp) which is an auto-industry terminology) One BHP (Boiler Power)= 33,500 BTU/hr = 9.803 kilowatts Power rating of steam-boliers is in units of BHP (boiler -horsepower) ![]() Power-Units Conversion 1kW (KiloWatt) = 3414 BTU/hr Power is sometimes expressed in alternate units like BTU/hr or Horsepower (hp) the energy used (or supplied) per unit time. Energy units employed by electric companies are the kWhr (Kilo-Watt-Hour for electric) or Therm (for gas).ġ000J = 1kJ (KiloJoule) = 0.9485 BTU=0.0002778 kWhrġPJ (PetaJoule)= 1,000,000,000,000,000 i.e. The JOULE (J) is a commonly used unit of energy. MHI 101: Energy, Power and Thermodynamics Tutorial
0 Comments
Leave a Reply. |