Your clients are paying your company a premium to install their HVAC equipment correctly, and they have an expectation of performance. For example,įurthermore, installers, start-up technicians, and field technicians must ensure the system has proper airflow, based on the OEM’s tables, or performance could drop and delivered capacity could be reduced. ![]() Many factors can change the typical 400 CFM per ton to a different CFM value. N = number of moles of gas present Air Volume Conversion FactorsĪir volume conversion factors related to air with temperature 70☏ (21.“ That system needs 400 CFM per ton! “ Does this rule of thumb sound familiar? Although many contractors may have known about this ‘ rule-of-thumb ‘ for a long time, how many contractors know that 400 CFM per ton is not always the case? The True Gas Law, or the Non-Ideal Gas Law, becomes: This correction factor depends on the pressure and temperature for each gas considered. It is called the Gas Compressibility Factor, or Z-factor. To account for the deviation from the ideal situation, another factor is included. The Ideal Gas Law is accurate only at relatively low pressures and high temperatures. T f = Temperature after filter or inlet equipment ( oR) Note! P f = Pressure after filter or inlet equipment (psia) ICFM = ACFM (P act / P f) (T f / T act) (2) The conversion from ACFM to ICFM can be expressed as When air passes through the filter there will be a pressure drop. Inlet Cubic Feet per Minute - ICFM - is used by compressor vendors to establish conditions in front of additional equipment like inlet filter, blower or booster. = 129.1 ICFM - Inlet Cubic Feet per Minute temperature 80 oF - absolute temperature T act = 540 oR.elevation 5000 feet (1500 m) - atmospheric pressure P act = 12.23 psia.The actual CFM of a compressor operating at "non-standard" conditions like Make a Shortcut to this Calculator on Your Home Screen?.Saturation pressure at the actual temperature - P sat - (psia)Īctual ambient air temperature - T act - ( oR) Standard absolute air pressure - P std - (psia)Īctual absolute air pressure - P act - (psia) The calculator below can used to calculate ACFM: free apps for offline use on mobile devices. P sat Φ < P act Related Mobile Apps from The Engineering ToolBox T act = Actual ambient air temperature ( oR) P sat = saturation pressure at the actual temperature (psi) P act = absolute pressure at the actual level (psia) P std = standard absolute air pressure (psia) The conversion from SCFM to ACFM can be expressedĪCFM = SCFM (T act / T std) (1) The Actual Cubic Feet per Minute - ACFM - depends on the The actual air volume flow is often termed ACFM - Actual Cubic Feet per Minute. vacuum is applied to a volume of air - it expands.pressure is applied a volume of air - it gets smaller.Real life "actual conditions" are seldom "standard conditions". Note that the The Compressed Air & Gas Institute and PNEUROP have adopted the definition used in ISO standards with dry (0% relative humidity) air at 14.5 psia (1 bar) and 68 oF (20 oC). The most common used in the United States is with the "sea-level" properties:Įuropeans normally use one ata and 0 oC as SCFM. The SCFM - Standard Cubic Feet per Minute - determines the weight of air to fixed or "Standard" conditions. It is common to rate compressed air consumption in Standard Cubic Feet per Minute - SCFM.
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