[工學(xué)]建筑環(huán)境學(xué)chapter41-2thermalcomfortable(1)-wenkub
2023-04-06 02:33:11 本頁(yè)面
【正文】 fferent modes of heat transfer. 1 Conduction 導(dǎo)熱 2 Convection 對(duì)流 3 Radiation 輻射 Conduction 導(dǎo)熱 is the transfer of heat energy through a material without the molecules of the material changing their basic positions. 物體各部分無(wú)相對(duì)位移或不同物體直接接觸時(shí)依靠分子、原子及自由電子等微觀粒子熱運(yùn)動(dòng)而進(jìn)行的熱量傳遞現(xiàn)象 in theory , can occur in solids, liquids and gases in fact， dense solids. Different materials conduct heat at different rates thermal conductivity導(dǎo)熱率 best conductors are Metals Poor conductors are called insulators 隔熱體 A very famous Law?? Fourier’s Law 各向同性材料的導(dǎo)熱問(wèn)題 注冊(cè)設(shè)備師考題 ? 單純的導(dǎo)熱發(fā)生在（ ） A 氣體中 B 液體 C固體 D以上三種物體 ? 穩(wěn)態(tài)導(dǎo)熱是指（ ） A溫度不隨時(shí)間變化 B溫度不隨空間位置變化 C溫度在各點(diǎn)的值相等 D溫度不隨時(shí)間和空間位置變化 ? two types: (a) Natural / Free Convection (b) Forced Convection uses a mechanical pump to achieve a faster flow of fluid. Convection 對(duì)流 is the transfer of heat energy through a material by the bodily movement of particles can occur in fluids ( liquids and gases) ,but never in solids. 注冊(cè)設(shè)備師考題： ?對(duì)流換熱以（ ）作為基本計(jì)算式 A 傅里葉定律 B 牛頓冷卻定律 C 普朗克定律 D 熱力學(xué)第一定律 Stack effect 煙囪效應(yīng) 主要作用是拔火拔煙，排走煙氣，改善燃燒條件。 解：設(shè)熱泵按逆卡諾循環(huán)運(yùn)行，根據(jù)題意， t1= 95 ℃ ， t2= 13℃ n pu te n e r g y P u m p ou t pu t e n e r g y H ea t C O P211H ???? TTT pump energy input :10kW heat energy output: 熱泵從環(huán)境中取得的熱量 供熱量中 注冊(cè)設(shè)備師考試題 ? 冬季 利用熱泵為房屋供暖，使室內(nèi)溫度保持在 20℃ ，需要向室內(nèi)供熱 3000W，室外環(huán)境溫度為 5℃ ，試求該熱泵的熱泵性能系數(shù)（供熱系數(shù)）？ ? 帶動(dòng)該熱泵工作所需要的最小功耗是多少？ ? ? Heat sources for heat pumps ? Air ? Earth ? Water ? Exhaust heat A geothermal heat pump system. Summary of chapter 2 Nature of heat, its measurement and its effect 熱的性質(zhì)、量度和作用 Heat transfer 熱傳遞 Gases and vapours, and their effects 氣體和蒸氣，及其作用 Refrigerators and heat pumps 制冷機(jī)及熱泵 useful sentence patterns： XX is the standard SI unit of YY ?焦耳是國(guó)際單位制中能量的單位 ?開爾文是國(guó)際單位制中溫度的單位 Table XX gives YY values for a variety of materials ?表（ ）給出了不同材料的（ 比容 ） 值 xx will be discussed in later chapter. ? 這些問(wèn)題在以后的章節(jié)中會(huì)講到。 Heat Pump 制冷機(jī)和熱泵 ? Refrigeration: 制冷 The transfer of heat from lower temperature regions to higher temperature is called refrigeration. ? Refrigerator: 制冷機(jī) Devices that produces refrigeration are called refrigerators. ? Refrigerant:制冷劑 The working fluid used in refrigerators are called refrigerant. ? Heat Pump:熱泵 Refrigerator used for the purpose of heating a space by transferring heat from a cooler medium are called heat pump. Can be divided into: 1） pression refrigerator and heat pump cycle 壓縮式制冷機(jī)和熱泵循環(huán) 2） absorption refrigeration cycle 吸收式制冷循環(huán) The refrigeration cycle 制冷循環(huán) 1） pression refrigerator and heat pump cycle 壓縮式制冷機(jī)和熱泵循環(huán) Four main ponents： Compressor 壓縮機(jī) Condenser 冷凝器 Expansion valve 膨脹閥 Evaporator 蒸發(fā)器 Four main ponents of a kitchen refrigerator. 2） absorption refrigeration cycle 吸收式制冷循環(huán) Not every gas behaves in a way that is suitable for the cycle of vapourliquidvapour changes used in refrigeration. A refrigerant must be below its critical temperature, or it will not liquefy, and it must be above its melting point, or else it will solidify. in general a useful refrigerant should possess the following properties: ? Low boiling point 低沸點(diǎn) ? High latent heat of vaporisation 高的氣化潛熱 ? Easy liquefaction by pression 壓縮后容易液化 ? Stable, nontoxic and noncorrosive 穩(wěn)定、無(wú)毒無(wú)腐蝕 ? Environmental safety 對(duì)環(huán)境無(wú)害 Refrigerants :制冷劑 ? Chlorofluorocarbon (CFC) is a mixture of anic pounds contain carbon碳 , chlorine氯 , and fluorine 氟 ? freon 氟利昂 . ? It is now accepted that CFCs help cause a reduction of the ozone layer臭氧層 in the upper atmosphere of the earth and contribute to global warming of the World’s weather systems. CFCs ) 氟氯碳化物類 CFC replacements 氟利昂替代物 ? Ammonia 氨 is an efficient refrigerant but its toxicity and flammability requires special safety measures. ? Carbon dioxide 二氧化碳 is used in some large refrigeration plants and requires high operating pressures. ? Compression refrigeration cycle 壓縮式制冷循環(huán) ? Absorption refrigeration cycle 吸收式制冷循環(huán) refrigerators 制冷機(jī) A heat pump is a device which extracts hea
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