Selection issue of key parameters for air coolers (air design temperature)
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Recently, a project required an air cooler to cool the process medium. Since the project is located in a remote area in the northeast of the country where there is no water supply, an air cooler was installed. There has been considerable confusion regarding the design temperature of air, as choosing a higher or lower value for this parameter has a significant impact on the heat exchange area ； In previous projects, the extremely high local temperatures were used as the design temperature for the air in the air coolers; as a result, due to the large heat exchange area, various freezing and blockages occurred during winter on site ； Later, the average temperature of the hottest months was chosen; however, in some periods of summer the cooling effect of the medium is poor and the heat exchange area is small... The literature recommends using the monthly average of the highest daily temperatures during the hottest month plus 3–4°C, while others suggest determining it based on the average daily temperature over a period of no more than five days per year in summer. But the data available is limited – has anyone among you encountered such information? ? How should this key parameter be chosen?
We generally use the monthly average of the highest temperatures on the hottest days of the month plus 3~4℃
Could you please provide the name of the design specification for the air cooler, sir? I took a brief look at ISO13706-2011, NBT 47007, API661, and SHELL DEP.31.21.70.31, and found no provisions regarding the selection of the air design temperature
The values shall be taken in accordance with the provisions in Appendix D of NB/T 47007 \"Air-Cooled Heat Exchangers\". For non-critical operating conditions, the concept of the \"highest air temperature for more than 400 hours per year\" corresponds to meteorological data for which the frequency, calculated using the method based on the frequency of dry-bulb air temperatures, is 5% (= 400/8000); in other words, it refers to the \"dry-bulb temperature\" as recorded in standard meteorological data. For critical operating conditions, use air dry-bulb temperature data with a frequency of 0.5% (= 40/8000); actually, using data with a frequency of 1% and rounding it up slightly will also work just as well. Taking the extreme highest temperature would be too wasteful and unscientific.