Gas Turbine Inlet Air Cooling: Case Study from a Middle East Power Plant
The boundary conditions
The site is a Saudi Arabian power plant running frame-type gas turbines, with summer ambient air temperatures regularly exceeding 45°C — well above the ISO reference condition of 15°C. Gas turbines are volumetric machines: as inlet air temperature rises, air density falls, mass flow into the compressor drops, and output falls with it. At 45°C ambient, a turbine rated at ISO conditions can lose 5–10% of nameplate capacity simply because the air feeding the compressor is too thin and hot. During peak summer demand — exactly when the grid needs maximum output — the turbine delivers the least.
The plant operator had frame-type gas turbines with conventional dry-filter inlet systems and no thermal conditioning of the incoming air. The project objective was to recover that lost capacity through inlet air cooling, without modifying the turbines themselves or exceeding the pressure drop budget at the compressor inlet.
Sizing the inlet cooler
Intake cooling works by lowering the temperature of ambient air before it enters the compressor, increasing air density and mass flow. For every degree Celsius the inlet temperature drops below the ambient, the turbine recovers a fraction of its derated output. At this site, the target was to cool incoming air from summer peak conditions down toward 15°C — a temperature differential that, at typical summer conditions, delivers a power recovery exceeding 20% of the derated output.
Dongrun performed thermal performance calculations accounting for the complex condensation conditions that arise when humid desert air is cooled below its dew point. This is a critical design constraint: condensate entrained in high-velocity airflow can cause compressor blade erosion. The inlet cooler design incorporated front-end filtration, rear-end condensate blocking, and an automatic defogging and cleaning system to prevent droplet carry-over into the turbine inlet duct.
The heat exchanger bundle uses copper and stainless steel tubes with hydrophilic aluminum foil fins — the hydrophilic coating promotes condensate sheeting rather than droplet formation, reducing entrainment risk. The frame is painted carbon steel sized to fit the existing inlet plenum structure. Air-side pressure drop through the bundle was held to as low as 70 Pa, preserving the compressor inlet pressure budget that the OEM’s performance guarantee requires.
The engineering chain
Thermal sizing started with Dongrun’s in-house calculation software, which incorporates condensation heat transfer models calibrated against the company’s own test platform data — standard Nusselt-Re-Pr correlations are unreliable when a phase change is occurring simultaneously with sensible cooling. The design was then cross-checked against HTRI to confirm the heat transfer and pressure-drop predictions. The fin geometry and tube layout selected for this project were drawn from geometries that had previously been tested on Dongrun’s physical test platform, so performance confidence was backed by measured data, not extrapolation.
Manufacturing, shipping, and on-site commissioning were handled by Dongrun under a turnkey contract — the plant operator received a working system rather than a collection of components to integrate.
Result: Significant summer power recovery
The Saudi Arabia deployment, completed in 2007, was Dongrun’s first overseas turnkey project and established the company’s capability in gas turbine inlet air systems for international clients. Summer peak-period measurements confirmed substantial power recovery consistent with the thermal design predictions, with the inlet air conditioning system operating reliably through sustained high-ambient-temperature conditions.
The project also validated Dongrun’s condensate management approach: no compressor damage or blade erosion incidents were reported attributable to the inlet cooling system during the service period.
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