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Power Train Applications 107 7.15 engIne coolant Engine coolants used in internal combustion engines can be considered to be cryoprotectant or colligative agents. Cryoprotectants are basically agents added to water to reduce the freeze point of a mixture. Colligative agents describe the behavior of coolant in warmer environments because they have beneficial behavior on both the freezing and boiling ends of the spectrum. It is these antiboil and antifreeze elements that the chemist seeks when he or she attempts to design an engine coolant. Water, of course, was the first material used as an engine coolant. However, alcohols such as methanol and glycols were soon utilized as a standard for engine coolant. In 1926, ethylene glycol became available as “permanent antifreeze.” Ethylene glycol’s higher boiling points increase the operational range of the coolant. 7.16 metHanol Methanol has the structure shown in Table 7.6. It has been used as an antifreeze in the past, but is currently used in windshield wiper fluid as an additive. It is a light, volatile, flammable liquid at room temperature with a distinctive odor mildly different from that of ethanol. 7.17 etHylene glycol Ethylene glycol is the major component used today as an antifreeze. It has a boiling point of 197.3°C. This higher boiling point is an advantage over compounds such as table 7.6 various coolant Properties compound boiling point (°c) mass (g/ mol) Methanol 64.7 32.04 0.79 Ethylene glycol Propylene glycol Diethylene glycol 197.3 62.07 1.11 188.2 79.06 1.04 244 106.12 1.12 density (g/cc) structure H H H HO HO HO O H OH OH O CH 3 OH
108 The Role of the Chemist in Automotive Design methanol and provides advantages for higher as well as lower ambient temperatures. Ethylene glycol is poisonous and must be disposed of through proper means. This compound forms calcium oxalate crystals in the kidneys and can cause acute renal failure. A bittering agent (denatonium benzoate) is added to coolant to discourage oral ingestion. 7.18 ProPylene glycol Propylene glycol is less toxic than ethylene glycol and is often labeled as a nontoxic antifreeze. This material is used in arenas other than the auto industry, such as water pipes and food processing. Propylene glycol will break down more readily and yield organic acids (formic, carbonic, and oxalic) upon exposure to excessive heat and air. The material will turn reddish in color upon breakdown. 7.19 new develoPments Antifreeze contains corrosion-inhibiting compounds and dye for identification purposes. Dilution is 1:1 glycol to water mixture, which gives protection down to –40°C. Newer developments have seen the advent of organic acid technology (OAT) antifreezes such as Dex-cool. OAT antifreezes have extended service lives of up to 150,000 miles. The properties of OAT coolant are shown in Table 7.7. OATs can mix with non-OATs; however, the change interval will decrease to 2 years or 30,000 miles. OATs work by a mechanism different from that of traditional antifreeze mechanisms. As can be seen from Table 7.7, the additive package of the OAT contains table 7.7 oat coolant Properties Physical Color Orange Odor Sweet to faint pH 8.0–8.6 Vapor pressure
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THE ROLE OF THE CHEMIST IN AUTOMOTI
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CRC Press Taylor & Francis Group 60
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Contents Preface...................
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Contents ix 6.6 Thermal Properties
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Contents xi 11.4 Glass Microspheres
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The Author Herman Phlegm was born i
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2 The Role of the Chemist in Automo
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10 The Role of the Chemist in Autom
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3 3.1 IntroductIon Component Materi
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Component Materials in Automobiles
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Page 128 and 129: 8 8.1 IntroductIon Seal and Gasket
Page 130 and 131: Seal and Gasket Design 113 table 8.
Page 132 and 133: Seal and Gasket Design 115 The main
Page 134 and 135: Seal and Gasket Design 117 Properti
Page 136 and 137: Seal and Gasket Design 119 table 8.
Page 138 and 139: Seal and Gasket Design 121 within t
Page 140 and 141: Seal and Gasket Design 123 F F F F
Page 142 and 143: Seal and Gasket Design 125 R R O ma
Page 144 and 145: Seal and Gasket Design 127 stabiliz
Page 146 and 147: 9 9.1 IntroductIon HVAC System Over
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158 The Role of the Chemist in Auto
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190 Index Carbon dioxide emissions,
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192 Index heat exchanger designatio
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194 Index Power train, 95 Power tra
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