Views: 0 Author: Site Editor Publish Time: 2025-07-03 Origin: Site
There are significant differences in heat transfer performance, application scenarios, and maintenance requirements between light tube bundles and finned tube bundles for low-pressure economizers, with the core difference stemming from whether or not the heat transfer surface area is extended by fins.
Performance Indicators | Bare Tube Bundle | Finned Tube Bundle |
| Heat Transfer Efficiency | Lower. Relying only on the smooth surface of the tube itself, the heat transfer area per unit volume is small (usually 10-30 m²/m³) and the heat transfer coefficient is low (about 30-60 W/(m²・K) on the flue gas side). | Higher. Expanding the heat transfer surface area through fins (e.g. spiral fins, flat fins), the heat transfer area per unit volume is 3-10 times higher than that of a light tube (up to 50-200 m²/m³), and the heat transfer coefficient is even higher (about 80-150 W/(m²・K) on the flue gas side). |
| Flue Gas Side Pressure Loss | Smaller. Smooth surfaces have a low resistance to flue gas flow and pressure losses of typically 200-500 Pa, making them suitable for scenarios where fan energy consumption needs to be controlled. | Larger. The fins disturb the flue gas flow, increasing turbulence and resistance. Pressure losses are typically 500-1500 Pa, and higher-powered induced draft fans may be required. |
| Fouling Resistance | Stronger. Smooth surface is not easy to accumulate ash or trap particles (such as fly ash, tar), especially suitable for high ash or flue gas containing viscous impurities (such as coal-fired, biomass boilers). | Weaker. The gap between the fins is easy to jam ash particles, sticky substances (such as oil and gas, biomass tar), long-term operation is easy to form a blockage, resulting in a sudden drop in heat transfer efficiency. |
| Wear Resistance / Corrosion | Stronger. No fin structure, smooth surface, abrasive particles in the flue gas (e.g., fly ash) on the tube wall of the scouring abrasion is lighter; and is not easy to form localized corrosion due to the accumulation of ash (e.g., “under the ash corrosion”). | Weaker. Thin fin edges and low strength make them susceptible to abrasion by particles in high-velocity flue gases; accumulation of dust between fins leads to localized humidity increases and accelerated corrosion (especially in environments below the acid dew point). |
| Maintenance Difficulty | Lower. It can be cleaned directly by high-pressure water washing, mechanical ash removal or steam soot blower without worrying about fin damage and low maintenance cost. | Higher. It is necessary to avoid damaging the fins during the cleaning process (e.g., high-pressure water washing may bend the fins), and it is necessary to disassemble and clean the fins in case of serious accumulation of ash, which makes the maintenance cycle short and the cost high. |
| Cost and Volume | Low material cost (no finning), but requires more volume to ensure sufficient heat transfer area (2-5 times the volume of finned tubes for the same amount of heat transfer). | Higher material and processing costs (complex fin welding/rolling process), but more compact (1/3-1/5 the size of a light tube for the same amount of heat exchange). |
Typical applications for bare tube bundles
are high ash / abrasive flue gas environments: e.g. coal-fired boilers (high fly ash content), biomass boilers (with straw / wood pellets), waste incinerators (with hard impurities). The smooth surface of the light pipe reduces ash deposition and is highly resistant to abrasion, extending service life.
Flue gases containing sticky impurities: e.g. biomass gas boilers (containing tar), heavy oil boilers (containing unburned carbon particles) to avoid clogging of fin gaps with sticky substances.
Low heat transfer requirements or large space scenarios: when the boiler tail space is sufficient, and the heat transfer efficiency requirements are not high (such as only a small amount of waste heat recovery), the low-cost advantage of light tube is more obvious.
Frequent Soot Removal: For systems that require periodic soot removal by high pressure water or mechanical means, light tubes are easier to maintain without worrying about fin damage.
Typical Applications of Finned Tube Bundles
Low Ash / Clean Flue Gas Environment: For example, gas-fired boilers (virtually ashless flue gas), oil-fired boilers (low-sulfur, low-ash fuels), which can give full play to the high efficiency of fins for heat transfer and are less likely to be clogged with ash.
Scenarios with high heat transfer demand or space constraints: When space is tight at the end of the boiler (e.g., small industrial boilers), and a large amount of waste heat needs to be recovered in a limited volume (e.g., lowering the flue gas temperature from 300°C to 150°C), the compactness of finned tubes is more advantageous.
Low to medium temperature, low corrosion risk environment: Flue gas temperature is higher than the acid dew point (e.g., gas boiler flue gas dew point is about 50-70℃, much lower than the operating temperature), which avoids corrosion of the fins due to condensed acid. If the flue gas has a high sulfur content (e.g., high sulfur coal), corrosion-resistant materials (e.g., 316L stainless steel fins) are required, but at a significantly higher cost.
How to choose?
If the flue gas has high ash content, sticky impurities, severe wear and tear, or if you need to simplify maintenance and control fan energy consumption, give preference to bare tube bundles;
if the flue gas is clean (low ash, low corrosion) and you need to have high efficiency of heat transfer and space saving, give preference to finned tube bundles.
