A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor promoting corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator.

While the term coolant is commonly used in automotive, residential and commercial temperature-control applications, in industrial processing, heat transfer fluid is one technical term more often used, in high temperature as well as low temperature manufacturing applications.^[1]

The coolant can either keep its phase and stay liquid or gaseous, or can undergo a phase change, with the latent heat adding to the cooling efficiency. The latter, when used to achieve low temperatures, is more commonly known as refrigerant.

Gases[link]

Air is a common form of a coolant. Air cooling uses either convective airflow (passive cooling), or a forced circulation using fans.

Hydrogen is used as a high-performance gaseous coolant. Its thermal conductivity is higher than all other gases, it has high specific heat capacity, low density and therefore low viscosity, which is an advantage for rotary machines susceptible to windage losses. Hydrogen-cooled turbogenerators are currently the most common electrical generators in large power plants.

Inert gases are used as coolants in gas-cooled nuclear reactors. Helium has a low tendency to absorb neutrons and become radioactive. Carbon dioxide is used in Magnox and AGR reactors.

Sulfur hexafluoride is used for cooling and insulating of some high-voltage power systems (circuit breakers, switches, some transformers, etc.).

Steam can be used where high specific heat capacity is required in gaseous form and the corrosive properties of hot water are accounted for.

Liquids[link]

The most common coolant is water. Its high heat capacity and low cost makes it a suitable heat-transfer medium. It is usually used with additives, like corrosion inhibitors and antifreeze. Antifreeze, a solution of a suitable organic chemical (most often ethylene glycol, diethylene glycol, or propylene glycol) in water, is used when the water-based coolant has to withstand temperatures below 0 °C, or when its boiling point has to be raised. Betaine is a similar coolant, with the exception that it is made from pure plant juice, and is therefore not toxic or difficult to dispose of ecologically.^[2]

Very pure deionized water, due to its relatively low electrical conductivity, is used to cool some electrical equipment, often high-power transmitters and high-power vacuum tubes.

Heavy water is a neutron moderator used in some nuclear reactors; it also has a secondary function as their coolant. Light water reactors, both boiling water and pressurised water reactors the most common type, use light water.

Polyalkylene Glycol or PAG's are used as high temperature, thermally stable heat transfer fluids exhibiting strong resistance to oxidation. Modern PAG's can also be non-toxic and non-hazardous.^[3]

Cutting fluid is a coolant that also serves as a lubricant for metal-shaping machine tools.

Oils are used for applications where water is unsuitable. With higher boiling points than water, oils can be raised to considerably higher temperatures (above 100 degrees Celsius) without introducing high pressures within the container or loop system in question.^[4]

• Mineral oils serve as both coolants and lubricants in many mechanical gears. Castor oil is also used. Due to their high boiling points, mineral oils are used in portable electric radiator-style space heaters in residential applications, and in closed-loop systems for industrial process heating and cooling.
• Silicone oils and fluorocarbon oils (like fluorinert) are favored for their wide range of operating temperatures. However their high cost limits their applications.
• Transformer oil is used for cooling and additional electric insulation of high-power electric transformers.

Fuels are frequently used as coolants for engines. A cold fuel flows over some parts of the engine, absorbing its waste heat and being preheated before combustion. Kerosene and other jet fuels frequently serve in this role in aviation engines.

Freons were frequently used for immersive cooling of e.g. electronics.

Refrigerants are coolants used for reaching low temperatures by undergoing phase change between liquid and gas. Halomethanes were frequently used, most often R-12 and R-22, but due to environmental concerns are being phased out, often with liquified propane or other haloalkanes like R-134a. Anhydrous ammonia is frequently used in large commercial systems, and sulfur dioxide was used in early mechanical refrigerators. Carbon dioxide (R-744) is used as a working fluid in climate control systems for cars, residential air conditioning, commercial refrigeration, and vending machines.

Heat pipes are a special application of refrigerants.

Molten metals and salts[link]

Liquid fusible alloys can be used as coolants in applications where high temperature stability is required, e.g. some fast breeder nuclear reactors. Sodium (in sodium cooled fast reactors) or sodium-potassium alloy NaK are frequently used; in special cases lithium can be employed. Another liquid metal used as a coolant is lead, in e.g. lead cooled fast reactors, or a lead-bismuth alloy. Some early fast neutron reactors used mercury.

For certain applications the stems of automotive poppet valves may be hollow and filled with sodium to improve heat transport and transfer.

For very high temperature applications, e.g. molten salt reactors or very high temperature reactors, molten salts can be used as coolants. One of the possible combinations is the mix of sodium fluoride and sodium tetrafluoroborate (NaF-NaBF₄). Other choices are FLiBe and FLiNaK.

Liquid gases[link]

Liquified gases are used as coolants for cryogenic applications, including cryo-electron microscopy, overclocking of computer processors, applications using superconductors, or extremely sensitive sensors and very low-noise amplifiers.

Carbon Dioxide (chemical formula is CO₂) - is used as a coolant replacement^[5] for cutting fluids. CO₂ can provide controlled cooling at the cutting interface such that the cutting tool and the workpiece are held at ambient temperatures. The use of CO₂ greatly extends tool life, and on most materials allows the operation to run faster. This is considered a very environmentally friendly method, especially when compared to the use of petroleum oils as lubricants; parts remain clean and dry which often can eliminate secondary cleaning operations.

Liquid nitrogen, which boils at about -196 °C (77K), is the most common and least expensive coolant in use. Liquid air is used to a lesser extent, due to its liquid oxygen content which makes it prone to cause fire or explosions when in contact with combustible materials (see oxyliquits).

Lower temperatures can be reached using liquified neon which boils at about -246 °C. The lowest temperatures, used for the most powerful superconducting magnets, are reached using liquid helium.

Liquid hydrogen at -250 to -265 °C can also be used as a coolant. Liquid hydrogen is also used both as a fuel and as a coolant to cool nozzles and combustion chambers of rocket engines.

Nanofluids[link]

An emerging and new class of coolants are nanofluids which consist of a carrier liquid, such as water, dispersed with tiny nano-scale particles known as nanoparticles. Purpose-designed nanoparticles of e.g. CuO, alumina, titanium dioxide, carbon nanotubes, silica, or metals (e.g. copper, or silver nanorods) dispersed into the carrier liquid the enhances the heat transfer capabilities of the resulting coolant compared to the carrier liquid alone.^[6] The enhancement can be theoretically as high as 350%. The experiments however did not prove so high thermal conductivity improvements, but found significant increase of the critical heat flux of the coolants.^[7]

Some significant improvements are achievable; e.g. silver nanorods of 55±12 nm diameter and 12.8 µm average length at 0.5 vol.% increased the thermal conductivity of water by 68%, and 0.5 vol.% of silver nanorods increased thermal conductivity of ethylene glycol based coolant by 98%.^[8] Alumina nanoparticles at 0.1% can increase the critical heat flux of water by as much as 70%; the particles form rough porous surface on the cooled object, which encourages formation of new bubbles, and their hydrophilic nature then helps pushing them away, hindering the formation of the steam layer.^[9]

Solids[link]

In some applications, solid materials are used as coolants. The materials require high energy to vaporize; this energy is then carried away by the vaporized gases. This approach is common in spaceflight, for ablative atmospheric reentry shields and for cooling of rocket engine nozzles. The same approach is also used for fire protection of structures, where ablative coating is applied.

Dry ice and water ice can be also used as coolants, when in direct contact with the structure being cooled.

Sublimation of water ice was used for cooling the space suits of astronauts in the Project Apollo.

See also[link]

• Loss of coolant — a type of a nuclear reactor failure
• Pumpable ice technology

References[link]

External links[link]

Look up coolant in Wiktionary, the free dictionary.

• CO₂ as a natural coolant — FAQs

Edd China (born Edward John China 9 May 1971) is a motor specialist who has been featured in British TV shows including Wheeler Dealers and Auto Trader, both alongside television presenter Mike Brewer. China has also appeared on various radio shows. He was educated at King Edward's School, Witley, and holds a degree in Engineering Product Design from London South Bank University. During one episode of 'Wheeler Dealers' (Season 7, Episode 9: BMW M3 Convertible), Mike Brewer stated that China is 6' 7" tall.

China is managing director of his own company, Cummfy Banana Limited, which was set up in March 1999 to design and manufacture unique vehicles for advertising, corporate promotional work and special occasions such as weddings and proms.

China holds the Guinness World Record for 'fastest furniture', at 92 mph (148 km/h), beating the old record at 82 mph, which he also held.^[1] He has also appeared on Top Gear, where he showcased a Rover 800 (purchased for £200) that had been modified with budget Bond-esque gadgets, such as an ejection seat, for merely £100.^[2] The double-deck cars in Top Gear (series 11 episode 6, British v Germans) were also manufactured by China.^[3]

Records[link]

References[link]

External links[link]

• Cummfy Banana
• http://www.greasejunkie.com/worlds-wackiest-racers.html

Jay Leno
Leno in July 2008
Birth name	James Douglas Muir Leno
Born	(1950-04-28) April 28, 1950 (age 62)[1] New Rochelle, New York, U.S.[1]
Medium	Television, Film, Stand up
Nationality	American
Years active	1973–present
Genres	Observational comedy, Political satire
Subject(s)	American culture, Everyday life
Influences	Johnny Carson, Robert Klein, Alan King, George Carlin,[2] Don Rickles, Bob Newhart, Rodney Dangerfield
Influenced	Dennis Miller[3]
Spouse	Mavis Leno (1980–present)
Notable works and roles	The Tonight Show with Jay Leno (host, 1992–2009, 2010–) The Jay Leno Show (host, 2009–2010)
Signature
Website	The Tonight Show with Jay Leno
Emmy Awards
Outstanding Variety, Music or Comedy Series 1995 The Tonight Show with Jay Leno

James Douglas Muir "Jay" Leno /ˈlɛnoʊ/ (born April 28, 1950)^[1] is an American stand-up comedian and television host.

From 1992 to 2009, Leno was the host of NBC's The Tonight Show with Jay Leno. Beginning in September 2009, Leno started a primetime talk show, titled The Jay Leno Show, which aired weeknights at 10:00 p.m. (Eastern Time, UTC-5), also on NBC. After The Jay Leno Show was canceled in January 2010 amid a host controversy, Leno returned to host The Tonight Show with Jay Leno on March 1, 2010.^[4]

Early life[link]

James "Jay" Leno was born in New Rochelle, New York, in 1950. His mother, Catherine (née Muir; 1911–1993), a homemaker, was born in Greenock, Scotland, and came to the United States at age 11. Leno's father, Angelo (1910–1994), who worked as an insurance salesman, was born in New York to immigrants from Flumeri, Italy.^[5] Leno grew up in Andover, Massachusetts, and although his high school guidance counselor recommended that he drop out of school, he later obtained a Bachelor's degree in speech therapy from Emerson College, where he started a comedy club in 1973.^[6] Leno's siblings include his late older brother, Patrick, who was a Vietnam veteran^[7] and a lawyer.^[6]

Career[link]

During the 1970s, Leno appeared in minor roles in several television series and films, first in the 1976 episode "J.J. in Trouble" of Good Times and the same year in the pilot of Holmes & Yo-Yo. After an uncredited appearance in the 1977 film Fun with Dick and Jane, he played more prominent parts in 1978 in American Hot Wax and Silver Bears. Other films and television series from that period include Almost Heaven (1978), "Going Nowhere" (1979) from One Day at a Time, Americathon (1979), Polyester (1981), "The Wild One" (1981) from Alice, "Feminine Mistake" (1979) and "Do the Carmine" (1983) from Laverne & Shirley.

[edit] The Tonight Show

Leno in 1993, shortly after becoming host of The Tonight Show

Starting in 1987, Leno was a regular substitute host for Johnny Carson on The Tonight Show. In 1992, he replaced Carson as host^[8] amid controversy with David Letterman, who had been hosting Late Night with David Letterman since 1982 (aired after The Tonight Show), who many had expected to be Carson's successor. The story of this turbulent transition was later turned into a book and a movie. Leno continued to perform as a stand-up comedian throughout his tenure on The Tonight Show.

In 2004, Leno signed a contract extension with NBC which would keep him as host of The Tonight Show until 2009.^[9] Later in 2004, Conan O'Brien signed a contract with NBC under which O'Brien would become the host of The Tonight Show in 2009, replacing Leno at that time.^[10]

During the 2007–08 Writers Guild of America strike, Leno was accused of violating WGA guidelines by writing his own monologue for The Tonight Show. While NBC and Leno claim there were private meetings with the WGA where there was a secret agreement allowing this, the WGA denied such a meeting.^[11] Leno answered questions in front of the Writers Guild of America, West trial committee in February 2009 and June 2009, and when the WGAW published its list of strike-breakers on 11 August 2009, Leno was not on the list.^[12][13]

In 1998, Leno competed in a tag-team match at the WCW's "Road Wild" pay-per-view . In 2001, he voiced The Crimson Chin, a superhero in the Nickelodeon animated series The Fairly OddParents and continues to do so today.

Leno said in 2008 that he was saving all of his income from The Tonight Show and living solely off his income from stand-up comedy.^[14]

On April 23, 2009, Leno checked himself into a hospital with an undisclosed illness.^[15] He was released the following day and returned to work on Monday, April 27. The two subsequently cancelled Tonight Show episodes for April 23 and April 24 were Leno's first in 17 years as host.^[16][17] Initially, the illness that caused the absence was not disclosed, but later Leno told People magazine that the ailment was exhaustion.^[17][18]

Michael Jackson trial[link]

In the 2005 trial of Michael Jackson over allegations of child molestation, Leno appeared as a defense witness (many celebrity defense witnesses had been expected, but Leno was one of the few whose testimony was actually needed). In his testimony regarding a call by the accuser, Leno testified that he never called the police, that no money was asked for, and there was no coaching — but that the calls seemed unusual and scripted.^[19]

Leno in 2006.

As a result, Leno was initially not allowed to continue telling jokes about Jackson or the case, which had been a fixture of The Tonight Show's opening monologue in particular. But he and his show's writers used a legal loophole by having Leno briefly step aside while stand-in comedians took the stage and told jokes about the trial. Stand-ins included Roseanne Barr, Drew Carey, Brad Garrett, and Dennis Miller among others.^[20]

[edit] Succession by Conan O'Brien and The Jay Leno Show

Because Leno's show continued to lead all late-night programming in the Nielsen ratings, the pending expiration of Leno's contract led to speculation about whether he would become a late-night host for another network after his commitment to NBC expired.^[21] Leno left The Tonight Show on Friday May 29, 2009,^[22][23] and Conan O'Brien took over on June 1, 2009.

On December 8, 2008, it was reported that Leno would remain on NBC and move to a new hour-long show at 10 p.m. Eastern Time (9 p.m. Central Time) five nights a week.^[24] This show follows a similar format to The Tonight Show, tapes at the same lot, and retains many of Leno's most popular segments. Late Night host Conan O'Brien was his successor on The Tonight Show.^[25]

Jay Leno's new show, titled The Jay Leno Show, debuted on September 14, 2009. It was announced at the Television Critics Association summer press tour that it would feature one or two celebrities, the occasional musical guest, and keep the popular "Headlines" segments, which would air near the end of the show. First guests included Jerry Seinfeld, Oprah Winfrey (via satellite), and a short sit-down with Kanye West discussing his controversy at the 2009 MTV Video Music Awards.^[26]

[edit] Timeslot conflict and return to The Tonight Show

Wikinews has related news: US TV host Conan O'Brien rejects NBC's offer to switch his show's time slot

In their new roles, neither O'Brien nor Leno succeeded in delivering the viewing audiences the network anticipated. On January 7, 2010, multiple media outlets reported that beginning March 1, 2010, Jay Leno would move from his 10pm weeknight time slot to 11:35pm, due to a combination of pressure from local affiliates whose newscasts were suffering, and both Leno's and O'Brien's poor ratings.^[27][28] Leno's show would be shortened from an hour to 30 minutes. All NBC late night programming would be preempted by the 2010 Winter Olympics between February 15 and February 26. This would move The Tonight Show to 12:05am, a post-midnight timeslot for the first time in its history. O'Brien's contract stipulated that NBC could move the show back to 12:05 a.m. without penalty (a clause put in primarily to accommodate sports preemptions).^[29]

On January 10, NBC confirmed that they would move Jay Leno out of primetime as of February 12 and intended to move him to late night as soon as possible.^[30][31] TMZ reported that O'Brien was given no advance notice of this change, and that NBC offered him two choices: an hour-long 12:05am time slot, or the option to leave the network.^[32] On January 12, O'Brien issued a press release that stated he would not continue with Tonight if it moved to a 12:05am time slot,^[33] saying, "I believe that delaying The Tonight Show into the next day to accommodate another comedy program will seriously damage what I consider to be the greatest franchise in the history of broadcasting. The Tonight Show at 12:05 simply isn’t The Tonight Show."

On January 21, it was announced that NBC had struck a deal with O'Brien. It was decided that O'Brien would leave The Tonight Show. The deal was made that O'Brien would receive a $33 million payout and that his staff of almost 200 would receive $12 million in the departure. O'Brien's final episode aired on Friday, January 22.^[34][35][36] Leno returned as host of The Tonight Show following the 2010 Winter Olympics on March 1, 2010.

On July 1, 2010, Variety reported that total viewership for Jay Leno's Tonight Show had dropped from 5 million to 4 million for the second quarter of 2010, compared to the same period in 2009. Although this represented the lowest second-quarter ratings for the show since 1992, Tonight was still the most-watched late night program, ahead of ABC's Nightline (3.7 million) and David Letterman's Late Show (3.3 million).^[37] Ratings over the following summer, when compared to the same period in 2009 with O'Brien hosting The Tonight Show (including O'Brien's highly rated debut), showed that while total viewership was 12% higher for Leno, viewership in the important "adults aged 18–49" demographic was 23% lower.^[38] NBC ratings specialist Tom Bierbaum commented that due to the host being out of late night television for a period of time and the subsequent 2010 Tonight Show conflict, Leno's ratings fall was "not a surprise at all".^[39]

Public image[link]

Criticism of Leno[link]

Leno on The Tonight Show in 2005

Leno has faced heated criticism and some negative publicity for his perceived role in the 2010 Tonight Show timeslot conflict.^[40][41] Critics have pointed to a 2004 Tonight Show clip, wherein Leno claimed he would allow O'Brien to take over without incident.^[41][42] At the time, Leno stated he didn't want O'Brien to leave for a competing network, adding, "I'll be 59 when [the switch occurs], that's five years from now. There's really only one person who could have done this into his 60s, and that was Johnny Carson; I think it's fair to say I'm no Johnny Carson."^[42] Leno also described The Tonight Show as a dynasty, saying "you hold it and hand it off to the next person. And I don't want to see all the fighting..." At the end of the segment, he said, "Conan, it's yours! See you in five years, buddy!"^[43]

Actor and comedian Patton Oswalt was among the first celebrities to openly voice disappointment with Leno, saying, "Comedians who don't like Jay Leno now, and I'm one of them, we're not like, 'Jay Leno sucks;' it's that we're so hurt and disappointed that one of the best comedians of our generation... willfully has shut the switch off."^[44] Rosie O'Donnell has been among O'Brien's most vocal and vehement supporters,^[45][46] calling Leno a "bully" and his recent actions "classless and kind of career-defining."^[47]

Bill Zehme, the co-author of Leno's autobiography Leading with My Chin, told the Los Angeles Times: "The thing Leno should do is walk, period. He's got everything to lose in terms of public popularity by going back. People will look at him differently. He'll be viewed as the bad guy."^[48]

Support for Leno[link]

NBC Sports head executive and former Saturday Night Live producer Dick Ebersol spoke out against all who had recently mocked Leno, calling them "chicken-hearted and gutless."^[49]

Jeff Gaspin also defended Leno: "This has definitely crossed the line. Jay Leno is the consummate professional and one of the hardest-working people in television. It's a shame that he's being pulled into this."^[48]

Paul Reiser and Jerry Seinfeld are two of the number of celebrities to have voiced support for Leno.^[50][51]

Responding to the mounting criticism, Leno claimed that NBC had assured him that O'Brien was willing to accept the proposed arrangement and then would not let either host out of his contract.^[52] Leno also said that the situation was "all business."^[52] He appeared on the January 28 episode of The Oprah Winfrey Show in an attempt to repair some of the damage done to his public image.^[53][54]

Personal life[link]

Leno with President Barack Obama in March 2009

Leno has been married since 1980 to Mavis Leno; they have no children.^[55]

He is known for his prominent jaw, which has been described as mandibular prognathism.^[56] In the book Leading with My Chin he stated that he is aware of surgery that could reset his mandible, but does not wish to endure a prolonged healing period with his jaws wired shut.

Leno is dyslexic.^[6] He claims to sleep only four to five hours each night.^[57] Leno does not drink or smoke, nor does he gamble.^[58] He spends most of his free time visiting car collections or working in his private garage.^[58]

Leno reportedly earns $32 million each year;^[59] his total net worth is unknown, but has been estimated to be at least $150 million.^[60]

Charity[link]

In 2001, along with his wife, he donated $100,000 to the Feminist Majority's campaign to stop gender apartheid in Afghanistan, to educate the public regarding the plight of women in Afghanistan under Taliban rule. Mavis Leno is on the board of the Feminist Majority.^[61][62]

In 2009, he donated $100,000 to a scholarship fund at Salem State College in honor of Lennie Sogoloff. Mr. Sogoloff gave Leno his start at his jazz club, Lennie's-on-the-Turnpike.^[63]

Love Ride[link]

Since 1985 Jay Leno has been the grand marshal for the Love Ride, a motorcycle charity event which since its founding in 1984 has raised nearly $14 million dollars for charities benefiting muscular dystrophy research and, in 2011, Autism Speaks.^{[citation needed]}

Leno arriving at the 45th Primetime Emmy Awards in his Hispano-Suiza Aero^[64]

Vehicle collection[link]

Leno owns approximately 100 vehicles, not including about 90 motorcycles.^[65] He also has a website called "Jay Leno's Garage," which contains video clips and photos of his automobiles in detail.^[66]

He has a regular column in Popular Mechanics which showcases his car collection and gives advice about various automotive topics, including restoration and unique models, such as his jet-powered motorcycle and solar-powered hybrid. Leno also writes occasional "Motormouth" articles for The Sunday Times,^[67] reviewing high-end sports cars and giving his humorous take on automotive matters.

References[link]

External links[link]

Wikiquote has a collection of quotations related to: Jay Leno

Wikimedia Commons has media related to: Jay Leno

• Official Tonight Show with Jay Leno web site
• Jay Leno's Car Collection
• Jay Leno's Columns at Octane magazine
• The New York Times on Leno's affiliation with McPherson College
• Live performance videos from the Tonight Show
• Jay Leno at the Internet Movie Database