1. Introduction and Background
In water-scarce regions, direct air-cooling (ACC) and indirect air-cooling (ACT) units have been rapidly developed and widely adopted. However, because air-cooled systems exchange heat directly with the ambient atmosphere, their operational performance is significantly affected by environmental weather conditions. In particular, the risk of tube bundle freezing and bursting during cold winter conditions, as well as high backpressure and hot air recirculation (HAR) during hot summer conditions, pose serious threats to the safe and economical operation of power plants.
Traditional temperature measurement methods mostly rely on a limited number of localized wall temperature sensors or manual periodic inspections, making it difficult to achieve real-time, high-resolution temperature field monitoring over large surface areas. In recent years, with advances in IoT sensor technology, infrared thermal imaging, and industrial broadband communication, new temperature measurement technologies-represented by the High-Density Digital Temperature Measurement Cable System and the Rail-Mounted Thermal Imaging Inspection System-have emerged. These technologies provide strong technical support for fine-grained operation, anti-freezing early warnings, and performance optimization of air-cooled systems.
2. Core Operational Pain Points of Air-Cooled Systems
2.1 Winter Freezing Risks and Mechanisms
Air-cooled systems are highly vulnerable to localized subcooling and freezing during winter. Key reasons and susceptible areas include:
Susceptible Freezing Areas
The lower section of parallel-flow (co-current) heat exchanger tubes (where condensate accumulates) and the upper section of counter-flow (counter-current) heat exchanger tubes (where steam volume decreases and non-condensable gases condense/sublimates into ice).
Low Steam Flow and Low Load Conditions
When the steam flow entering the air-cooled system is too small and the heat dissipation load is too low, localized subzero temperatures cannot be avoided even if all fans are stopped and natural ventilation is used.
Uneven Air Distribution in Natural Ventilation
Influenced by ambient winds and structural factors, uneven airflow on the air side easily causes localized overcooling. Generally, counter-flow units freeze more easily than parallel-flow units, and peripheral/edge units freeze more easily than interior units.
2.3 Ash and Dust Fouling on Heat Exchanger Bundles
During long-term operation, dust and debris accumulate on the surface of finned tubes, impairing heat transfer performance. Without accurate temperature distribution data, it is difficult to evaluate localized fouling levels and schedule timely high-pressure cleaning.
2.4 Conflict Between Safe Operation and Economical Backpressure
To prevent freezing during startup, shutdown, or low-load operation, traditional operating strategies typically enforce turbine backpressure to remain above 15 kPa. This conservative strategy sacrifices turbine vacuum and power generation efficiency, preventing the air-cooled system from operating in its most economical backpressure range.
3. Functions and Application Value of New Measurement Technologies
1.Anti-Freezing Early Warning & Protection Linkage: By monitoring the exit air temperature and tube wall temperature of heat dissipation bundles in high density, combined with data on backpressure, condensate temperature, and subcooling degree, lower-limit temperature thresholds for exit hot air are established to implement anti-freezing interventions proactively.
2.HAR Monitoring & Adjustment: Real-time monitoring of inlet air temperature allows calculation of the hot air recirculation rate. Operators can make predictive adjustments before HAR impacts turbine operation, reducing forced shutdowns, boiler trips, or load shedding.
3.Fouling Evaluation & Cleaning Guidance: Temperature field distribution characteristics are used to evaluate local and overall cleanliness of heat exchangers, guiding targeted high-pressure water washing operations.
4.Backpressure Optimization & Energy Saving: Comprehensive temperature field monitoring compensates for the inadequacy of traditional terminal temperature difference and temperature rise metrics. It guides operators to safely lower backpressure and increase vacuum, achieving energy conservation and consumption reduction.
4. High-Density Digital Temperature Measurement Cable Solution
4.1 Spatial Layout and Grid Arrangement
| Application Scenario | Structure Type | Layout Rules for Cable & Measurement Points |
| Direct Air-Cooled Condenser (ACC) | A-Frame Cooling Structure |
Cables arranged vertically every 1 m on both sides; temperature points spaced horizontally at 960 mm intervals; each heat dissipation panel equipped with a dedicated temperature collector. |
| Indirect Air-Cooled Tower (ACT) | Cooling Delta Heat Exchanger |
Cables with integrated digital sensors laid out vertically every 1 m along the cooling delta structure. |
4.2 Technical Characteristics of the Cable
Physical Protection & Armored Design: Built with internal steel wire protective tubing and wrapped in an industrial-grade rubber sheath that is high-voltage resistant, temperature resistant, anti-corrosive, waterproof, and flame-retardant. Highly tensile and wear-resistant for harsh outdoor high-altitude environments.
Sensor Specifications: Integrated high-precision bus-type digital temperature sensors with a measurement range of -55°C to +125.0°C and an accuracy of ±0.5°C.
4.4 Server Software and Data Processing
High-Capacity Processing: A single server supports up to 1,000,000 temperature points and 256 concurrent client connections, retrieving over 20,000 records per second.
Multi-Dimensional Reporting: Quickly aggregates and analyzes temperature data, generating shift, daily, weekly, monthly, quarterly, and annual reports.
Color-Coded Visualization Alert System:
- 30°C to 60°C: Displayed in green (normal values);
- Outside 30°C–60°C Range: Displayed in red (alarm values);
- Above 126°C: Displayed in purple (over-temperature values).