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Table Fan
A fan is a powered machine that creates airflow. A fan consists of rotating vanes or blades, generally made of wood, plastic, or metal, which act on the air. The rotating assembly of blades and hub is known as an '' impeller'', ''rotor'', or ''runner''. Usually, it is contained within some form of housing, or case. This may direct the airflow, or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, handcranks, and internal combustion engines. Mechanically, a fan can be any revolving vane, or vanes used for producing currents of air. Fans produce air flows with high volume and low pressure (although higher than ambient pressure), as opposed to compressors which produce high pressures at a comparatively low volume. A fan blade will often rotate when exposed to an air-fluid stream, and devices that take advantage of this, such as anemometers and wind tu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Comfort
Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment.ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC ( heating, ventilation, and air conditioning) design engineers. Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. The main factors that in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ding Huan
Ding Huan () was a Chinese craftsman, mechanical engineer, and inventor who lived in the first century CE during the Han dynasty The Han dynasty was an Dynasties of China, imperial dynasty of China (202 BC9 AD, 25–220 AD) established by Liu Bang and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–206 BC .... Among the inventions attributed to him is an air conditioning system based on evaporative cooling. Purported invention of the zoetrope In his multi-volume '' Science and Civilisation in China'', the British scientist and historian Joseph Needham briefly describes several devices he classes as "... a variety of zoetrope, which may well have originated in China".Needham, Joseph (1962). ''Science and Civilization in China'', vol. IV, part 1: ''Physics and Physical Technology''. Cambridge University Press. p. 123-124. The first example he offers used an umbrella-like canopy hung over an oil lamp and provid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Han Dynasty
The Han dynasty was an Dynasties of China, imperial dynasty of China (202 BC9 AD, 25–220 AD) established by Liu Bang and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–206 BC) and a warring interregnum known as the Chu–Han Contention (206–202 BC), and it was succeeded by the Three Kingdoms period (220–280 AD). The dynasty was briefly interrupted by the Xin dynasty (9–23 AD) established by the usurping regent Wang Mang, and is thus separated into two periods—the #Western Han (202 BC – 9 AD), Western Han (202 BC9 AD) and the #Eastern Han (25–220 AD), Eastern Han (25–220 AD). Spanning over four centuries, the Han dynasty is considered a Golden ages of China, golden age in Chinese history, and had a permanent impact on Chinese identity in later periods. The majority ethnic group of modern China refer to themselves as the "Han people" or "Han Chinese". The spoken Chinese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Conditioning
Air conditioning, often abbreviated as A/C (US) or air con (UK), is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature, and in some cases, also controlling the humidity of internal air. Air conditioning can be achieved using a mechanical 'air conditioner' or through other methods, such as passive cooling and ventilative cooling. Air conditioning is a member of a family of systems and techniques that provide Heating, ventilation, and air conditioning, heating, ventilation, and air conditioning (HVAC). Heat pumps are similar in many ways to air conditioners but use a reversing valve, allowing them to both heat and cool an enclosed space. Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used in vehicles or single rooms to massive units that can cool large buildings. Air source heat pumps, which can be used for heating as well as cooling, are becoming increasingly common in cool ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Punkawallah
A punkah, also pankha (, Hindi language, Hindi: , ), is a type of fan used since the early 6th century BC. The word ''pankha'' originated from ''pankh'', the wings of a bird which produce a current of air when flapped. History In its original sense in the Indian subcontinent, ''pankha'' (a Hindi language, Hindi word) typically describes a handheld fan made from a single frond of palm or a woven square of bamboo strips, rattan or other plant fibre, that can be rotated or fanned. These small handheld devices are still used by millions when ceiling fans stop working during frequent power outages. In the colonial age, the word came to be used in British India and elsewhere in the tropical and subtropical world for a large swinging fan, fixed to the ceiling, pulled by a punkah wallah during hot weather. To cover a larger area, such as the inside of an office or a courthouse, a number of punkahs could be connected together by strings so that they would swing in unison. The material ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British India
The provinces of India, earlier presidencies of British India and still earlier, presidency towns, were the administrative divisions of British governance in South Asia. Collectively, they have been called British India. In one form or another, they existed between 1612 and 1947, conventionally divided into three historical periods: *Between 1612 and 1757, the East India Company set up "factories" (trading posts) in several locations, mostly in coastal India, with the consent of the Mughal emperors, Maratha Empire or local rulers. Its rivals were the merchant trading companies of Portugal, Denmark, the Netherlands, and France. By the mid-18th century three ''Presidency towns'': Madras, Bombay and Calcutta, had grown in size. *During the period of Company rule in India, 1757–1858, the Company gradually acquired sovereignty over large parts of India, now called "Presidencies". However, it also increasingly came under British government oversight, in effect sharing sovereig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convection
Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be Transient state, transient (such as when a Multiphasic liquid, multiphase mixture of oil and water separates) or steady state (see convection cell). The convection may be due to Gravity, gravitational, Electromagnetism, electromagnetic or Fictitious force, fictitious body forces. Convection (heat transfer), Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its Earth's mantle, mantle. Discrete convective cells in the atmosphere can be identified by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sweat
Perspiration, also known as sweat, is the fluid secreted by sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and Apocrine sweat gland, apocrine glands. The eccrine sweat glands are distributed over much of the body and are responsible for secreting the watery, brackish sweat most often triggered by excessive body temperature. Apocrine sweat glands are restricted to the armpits and a few other areas of the body and produce an odorless, oily, opaque secretion which then gains its characteristic odor from bacterial decomposition. In humans, sweating is primarily a means of thermoregulation, which is achieved by the water-rich secretion of the eccrine glands. Maximum sweat rates of an adult can be up to per hour or per day, but is less in children prior to puberty. Evaporation of sweat from the skin surface has a cooling effect due to evaporative cooling. Hence, in Temperature, hot weather, or when the individual's muscles hea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evaporative Cooling
An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate (that is, it has a large enthalpy of vaporization). The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants. The cooling potential for evaporative cooling is dependent on the wet-bulb depression, the difference between dry-bulb temperature and wet-bulb temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cereal
A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, such as amaranth, buckwheat and quinoa, are pseudocereals. Most cereals are annuals, producing one crop from each planting, though rice is sometimes grown as a perennial. Winter varieties are hardy enough to be planted in the autumn, becoming dormant in the winter, and harvested in spring or early summer; spring varieties are planted in spring and harvested in late summer. The term cereal is derived from the name of the Roman goddess of grain crops and fertility, Ceres. Cereals were domesticated in the Neolithic around 8,000 years ago. Wheat and barley were domesticated in the Fertile Crescent; rice and some millets were domesticated in East Asia, while sorghum and other millets were domesticated in West Africa. Maize was domesticat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
