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Vaporization and condensation
From;    Author:Stand originally
One, vaporization
Heat to the liquid, make its call vaporization procedure for gaseous process from liquid change. Vaporization has two kinds of kind: Evaporate with boiling.
1) evaporate. The vaporization phenomenon that produces on fluid face is called evaporate. The process of dress air is a model evaporate process. Evaporate the speed of the process and evaporating condition have very big concern. Liquid temperature heals tall, evaporate more fast; Liquid evaporate leaven dough is accumulated more big, or speed of liquid surface gas heals big, evaporate more fast; The aeriform cent pressure of liquid surface and the difference of aeriform cent pressure all round are bigger, evaporate to also heal fast.
Evaporate the process is process of refrigeration of a kind of absorption of heat.
2) boiling. Heat the liquid when some temperature, be in water for example often press next heating to 100 ℃ , its interior can generate a lot of bubble, these bleb arrive at liquid surface burst freely ceaselessly, and emit vapour, this kind of vaporization phenomenon that appears with bleb form in liquid interior is called boiling.
Evaporate to although be the same as,attribute vaporization phenomenon with boiling, but fall in constant pressure, evaporate can undertake below any temperature, and boiling can be in only the constant temperature that reachs to answer relatively with liquid surface pressure (boiling point) when ability undertakes. The temperature when the liquid is boiling calls boiling point, call this pressure the saturated temperature below again, this pressure calls saturated pressure. Actually, boiling point is saturated temperature. The condensing temperature that refrigeration project middling weighs is the saturated temperature below condensing pressure, and evaporate temperature evaporates namely the saturated temperature below pressure.
When the pressure that gets when liquid place, its saturation temperature also is met corresponding change, so saturated pressure and saturated temperature have one to one correspondence relation. Say commonly, pressure increases, saturated temperature is elevatory also.
Below same pressure condition, different material has different boiling point, below atmosphere of a standard, the boiling point of a few kinds of material is as follows:
R134a (C2H2F4) - 26.5 ℃
R290 (C3H8) - 42.1 ℃
Water (R718) (H2O) 100 ℃
R12 (CF2CL2) - 29.8 ℃
R22 (CHF2CL) - 40.8 ℃
R717 (NH3) - 33.4 ℃
Heat to the liquid, can make a liquid boiling. However, to liquid step-down, also can make a liquid boiling. Should fall only when liquid pressure reduces the saturated pressure that falls at this liquid temperature accordingly, the liquid also can undertake boiling likewise. Refrigeration agent uses this principle to work namely when shedding classics throttle and evaporator.
Corporeal vaporization needs to absorb quantity of heat. Unit quality liquid turns the gaseous material place that is the same as temperature into completely the quantity of heat of need, call vaporization heat. Same kind of liquid, when different and saturated temperature, its vaporization heat is different also. Say commonly, temperature heals tall vaporization heat heals small.
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