【正文】 ues are sometimes given in other units，but consistent units must be used in Equation 1 . Equation 1 states that the heat flow rate q in the x direction is directly proportional to the temperature gradient dt/dx and the crosssectional area A normal to the heat flow. The proportionality factor is the thermal conductivity k. The minus sign indicates that heat flow is positive the direction of decreasing temperature. Conductivity values are sometimes given in other units，but consistent units must be used in Equation 1 . 公式（1）在x方向的熱流率q是成正比的溫度梯度DT/ DX和橫截面積一個(gè)正常的熱流。當(dāng)流體的電流是由外部來源（例如，一個(gè)鼓風(fēng)機(jī)或泵），固 液傳熱被稱為強(qiáng)迫對(duì)流。When fluid currents are produced by external sources (for example, a blower or pump), the solidtofluid heat transfer is termed forced convection. If the fluid flow is generated internally by nonhomogeneous densities caused by temperature variation, the heat transfer is termed natural convection or free convection.When fluid currents are produced by external sources (for example, a blower or pump), the solidtofluid heat transfer is termed forced convection. If the fluid flow is generated internally by nonhomogeneous densities caused by temperature variation, the heat transfer is termed natural convection or free convection.當(dāng)流體的電流是由外部來源（例如，一個(gè)鼓風(fēng)機(jī)或泵），固 液傳熱被稱為強(qiáng)迫對(duì)流。熱能量轉(zhuǎn)移發(fā)生在溫度降低的方向。電導(dǎo)電液體和固體，它被認(rèn)為是造成晶格結(jié)構(gòu)的縱向振蕩。 in liquids and electrically nonconducting solids, it is believed to be caused by longitudinal oscillations of the lattice structure. Thermal conduction in metals occurs, like electrical conduction, through the motion of free electrons. Thermal energy transfer occurs in the direction of decreasing temperature. In solid opaque bodies, thermal conduction is the significant heat transfer mechanism because no net material flows in the process and radiation is not a factor. 熱傳導(dǎo)傳熱，使能量是連續(xù)部分之間的運(yùn)輸粒子在原子水平上的顆?；驁F(tuán)體之間的動(dòng)能轉(zhuǎn)移的機(jī)制。傳熱之間的能源運(yùn)輸?shù)默F(xiàn)象，其中包括傳質(zhì)，動(dòng)量傳遞或流體摩擦和導(dǎo)電。Heat is energy in transit due to a temperature difference. The thermal energy is transferred from one region to another by three modes of heat transfer: conduction, convection, and radiation. Heat transfer is among a group of energy transport phenomena that includes mass transfer, momentum transfer or fluid friction and electrical conduction. 熱是由于溫差在傳輸過程中的能量。在暖通空調(diào)行業(yè)（如，水，空氣，大部分制冷劑）牛頓流體可以作為治療?？紤]采取分類流體為牛頓或非牛頓粘性的影響。Viscosity is a measure of a fluid’s resistance to shear. Viscous effects are taken into account by categorizing a fluid as either Newtonian or nonNewtonian. In Newtonian fluids, the rate of deformation is directly proportional to the shearing stress。雖然液體和氣體的分子運(yùn)動(dòng)特性有著很大的區(qū)別，但是他們的主要的力學(xué)區(qū)別在于可壓縮性的程度和液體自由表面（界面）的形成。當(dāng)剪切應(yīng)力下了堅(jiān)實(shí)的變形量只有有限的，而流體的剪切變形。在施加剪切力時(shí)，固體只發(fā)生有限的變形，而只要有剪切力的作用流體就會(huì)連續(xù)變形。Fluids differ from solids in their reaction to shearing. When placed under shear stress, a solid deforms only a finite amount, whereas a fluid deforms continuously for as long as the shear is applied. Both liquids and gases are fluids. Although liquids and gases differ strongly in the nature of molecular actions, their primary mechanical differences are in the degree of pressibility and liquid formation of a free surface. In general, liquids are considered inpressible fluids。可逆循環(huán)有兩個(gè)重要的屬性：（1）無制冷循環(huán)的性能系數(shù)之間相同的溫度限制經(jīng)營(yíng)的可逆循環(huán)高于，（2）之間相同的溫度極限運(yùn)行時(shí)，所有可逆循環(huán)，同樣的性能系數(shù)Flowing fluids in heating, ventilating, airconditioning, and refrigeration systems can transfer heat, mass, and momentum. This chapter introduces the basics of fluid mechanics related to HVAC processes, reviews pertinent flow processes, and presents a general discussion of singlephase fluid flow analysis.流動(dòng)的液體在加熱，通風(fēng)，空調(diào)和制冷系統(tǒng)，可以傳遞熱量，質(zhì)量和動(dòng)量。不可逆轉(zhuǎn)的概念到周期的運(yùn)作提供額外的洞察力。第二定律可能在幾個(gè)方面。如在常溫常壓下空氣的氣體是高度過熱蒸汽。當(dāng)蒸汽溫度大于飽和溫度，它是一個(gè)熱蒸氣。如果液體的溫度低于現(xiàn)有的壓力的飽和溫度，它被稱為是過冷液體（溫度低于給定壓力的飽和溫度）或壓縮液體（壓力大于飽和為給定的溫度壓力）。純物質(zhì)均勻的和不變的化學(xué)成分。因此，在一個(gè)周期結(jié)束時(shí)，所有屬性具有相同的價(jià)值，他們開始。一個(gè)過程是指定的初始和最終的平衡狀態(tài)，路徑（如果識(shí)別），并采取跨系統(tǒng)的邊界，在這個(gè)過程中發(fā)生的相互作用。通常情況下，熱力學(xué)性質(zhì)相結(jié)合，形成