Weak current College】 【Central air conditioning & refrigeration industry nomenclature resolution (2).

<br> <br> 1.7 evaporation and boiling <br> <br> Evaporation refers to free-surface liquids gasification process. For example, water evaporation. Clothes dry process. Evaporation on the surface of the liquid is due to the high energy of .molecular overcome liquid molecules of gravitation, wear out liquid reaches of space. In the same environment, liquids, the higher the temperature, the faster the evaporation. Refrigeration engineering, many issues are related to the evaporation process, such as cooling and humidification of air .conditioning and drying process. Infrared humidifier humidification is surface evaporation process. <br> <br> Boiling is the liquid inside the bubble forms of violent gasification process. For example, the process water to the boil. At a certain pressure, the liquid is .heated to a certain temperature began to boil. Throughout the boiling process, liquid absorption of heat all for its volumetric expansion and the gas-liquid phase transition temperature remains unchanged. If the electrode humidifiers belongs to the boiling process. <br> <br> .1.8 thermal conductivity (also known as thermal conductivity) <br> <br> Thermal conductivity is a materials transfer heat capacity of a physical quantity. If two equally thick material, one is a copper blocks, one is a cork blocks, put them in .the high temperature than itself, you can feel the copper block temperature, and the Cork block you feel in a short time. This description of two materials on heat conduction of different capacities, the materials on the thermal capacity of different transmission to digital representation is .called thermal conductivity, its value is equal to: when the material layer thickness on both sides for the lm, the temperature difference of 1 ° c, the surface area of over lm2 1h the conduction of heat, the symbol l, units are kcal / .mh ℃, the State's legal units is W / mK or use J / mhK indicated that conversion between them is: 1W/mK = 0.860kcal/mh ℃. <br> <br> Different materials have different thermal conductivity, and material composition, .density, molecular structure, and other factors. <br> <br> The same kind of material, the thermal conductivity of the main factors is the density and moisture. Density, thermal conductivity, thermal conductivity of high humidity is also high. <br .> <br> 1.9 heat transfer coefficient <br> <br> When you freeze a substance, such as in surface blowing it freeze faster than not blowing time fast. Represents the different substances in different States heat capacity of the physical quantity known as the .heat transfer coefficient, its value is equal to the hourly, every square meters area, when fluid and solid wall for temperature-difference between l ° c the transfer of heat. To sign a representation, its units as kcal / (m2h ℃), .the international system of units is W / (m2k) or J / (m2h ℃), the relationship is between the two conversion: 1W / (m2K) = 0.860kcal / (m2h ° c) <br> <br> 1.10 heat transfer .coefficient <br> <br> Heat from the hot side of fluid through the flat wall transfer to low-temperature side fluid. <br> <br> This heat transfer capabilities in addition to temperature, heat transfer on both sides and the size of .the area concerned, and the flat wall heat transmission coefficient, flat wall thickness of the walls on either side of the heat transfer coefficient. <br> <br> All factors column into a single formula, namely: <br> <br> Q .= KFDt (kJ / h) <br> <br> Type: Q: transmission of heat (kJ / h); F: flat wall surface area (m2); the temperature difference Dt: Dt = t1-t2 (° c) .; <br> <br> Heat transfer coefficient K: kJ / (m2h ° c) <br> <br> K is heat transfer coefficient, it numerically equal to the temperature difference when the sides l ° c, heat transfer area by lm2 .lh, thermal fluid from one side to another side of the cooling fluid transfer of heat. Unit is kJ / (m2h ° c) or W / (m2k). <br> <br> 1.11 specific volume and density <br> <br .> Unit volume of moist air has the quality known as density, wet air per unit mass of a volume called the hematocrit. <br> <br> 1.12 humidity <br> <br> Humidity is humid air containing water vapor content in the number .of physical quantities, there are three types of representation. <br> <br> A £ ® absolute humidity <br> <br> Lm3 wet air steam quality. Symbol for Z, unit is kg/m3. <br> <br> .V: steam volume of possession, that is, the wet air volume, expressed in m3. <br> <br> Absolute humidity is not convenient to use. It does not directly reflect the humid air of dry and wet. <br> < .br> B. amount of wet <br> <br> Per kg of dry air containing water vapor amount known as the moisture content, symbols for d, unit is kg / kg (dry). <br> <br> 1.13 dew point .temperature <br> <br> Under certain atmospheric pressure, moisture content does not change the steam condensation in the air to water (DEW) temperature. Unchanged at d, air temperature, from unsaturated State becomes saturated, air relative humidity j = 1O0 per .cent. In the air conditioning technology, the air temperature and dew point temperature, air dehumidification drying. <br> <br> 1.14 enthalpy <br> <br> Enthalpy wet air is an important parameter. Is a bit with the pressure inside the .can of composite state parameters. <br> <br> In the air conditioning process, often moist air state changes, enthalpy can easily determine the status of the change in the amount of heat in the process. Humid air change process is the process of .constant pressure, enthalpy difference equal to the heat capacity, namely: <br> <br> tDh = DQ = cmDt <br> <br> Type: Dh: enthalpy difference kJ / kg (dry) DQ: heat capacity kJ / kgm: .kgc moist air quality: humid air of the constant pressure heat kJ / (kg ¡ã c) 1.15 static, dynamic pressure, pressure <br> <br> In the select air conditioning or fan, you often encounter the static and dynamic pressure, .pressure these three concepts. According to the role of knowledge on fluid mechanics, fluid in the unit area is called a vertical force on pressure. When the air flow along the wind pipe wall, the pressure can be divided into static and dynamic pressure and full .pressure, unit is mmHg or kg/m2 or Pa, China's legal units is Pa. <br> <br> A. static pressure (Pi) <br> <br> Due to the irregular movement of air molecules and impact on the wall .is called a hydrostatic pressure. The calculation to calculate the absolute vacuum is called absolute zero of hydrostatic pressure. To atmospheric pressure to zero pressure is called relative static pressure. Air pressure means relative static pressure. Static pressure above atmospheric pressure, is positive, lower .than the atmospheric pressure is negative. <br> <br> B. dynamic pressure (Pb) <br> <br> Means the air flow pressure, as long as the wind tube air flow has certain dynamic pressure, its value is always positive .. <br> <br> C. full pressure (Pq) full pressure is static and dynamic pressure of algebra and: Pq = Pi x Pb full pressure represents lm3 gas with total energy. If the atmospheric starting point for the calculation, it can .be positive, it can be negative. <br> <br> <br> <br>.