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D240-19 – Standard Test Method Technical Guide
🧪 Scope and Applicability
ASTM D240-19, “Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter,” specifies a procedure for determining the gross heat of combustion of a wide range of liquid hydrocarbons. Under the jurisdiction of ASTM Committee D02, this method covers fuels with volatilities extending from light distillates to residual fuels.
Directly applicable fuel types include gasolines, kerosines, Nos. 1 and 2 fuel oil, Nos. 1-D and 2-D diesel fuel, and Nos. 0-GT, 1-GT, and 2-GT gas turbine fuels. All values are reported in SI units (MJ/kg).
| 🔍 Fuel Category | 📐 Examples from D240-19 |
|---|---|
| Spark-Ignition | Gasolines |
| Kerosene / Heating | Kerosines, No. 1 & 2 Fuel Oil |
| Diesel | No. 1-D & 2-D Diesel Fuel |
| Gas Turbine | No. 0-GT, 1-GT, & 2-GT |
⚠️ Precision Limitation: D240-19 explicitly states it is “not as repeatable and not as reproducible as Test Method D4809.” Standard D4809 is the preferred method when maximum precision is required.
⚙️ Test Procedure and Key Principles
The test involves combusting a weighed fuel sample in a constant-volume bomb calorimeter pressurized with oxygen. The resulting temperature rise of the calorimeter assembly is measured to calculate the total energy released. The fuel must contain only carbon, hydrogen, nitrogen, oxygen, and sulfur.
The critical term Gross Heat of Combustion (Qg) is defined as the energy released when a unit mass of fuel is burned, with the products being gaseous carbon dioxide (CO2), nitrogen oxides (NOx), and sulfur dioxide (SO2), while the produced water is condensed to the liquid state. The initial standard temperature for these calculations is 25 °C.
💡 Standard State Note: The gross heat of combustion (upper heating value) includes the latent heat of vaporization of water. This test method is used to determine the total energy content of a fuel, which is essential for calculating thermal efficiency and compliance with fuel specifications.
📊 Key Measured Properties and Results
The primary result reported from D240-19 is the Gross Heat of Combustion. The standard provides a detailed procedure and references numerous supporting ASTM methods for determining sulfur and hydrogen content necessary for the calculation (such as D129, D2622, D4294, D3701, and D7171).
| 📏 Parameter | ⚡ Specification in D240-19 |
|---|---|
| Result Name | Gross Heat of Combustion (Qg) |
| Standard Unit | Megajoules per kilogram (MJ/kg) |
| Initial Temperature | 25 °C (Standard State) |
| Water Phase in Products | Liquid (Condensed) |
| Primary Combustion Products | CO2, NOx, SO2, H2O (l) |
Users must follow specific safety precautions outlined in Sections 7, 9, and Annex A3 of the standard.