NASHIR, Mukhamad and Djaeni, Moh. and Muchammad, Muchammad (2026) INVESTIGASI EVAPORATION LOSS PADA GEOTHERMAL WET COOLING TOWER TIPE COUNTER FLOW-INDUCED DRAFT MELALUI SIMULASI COMPUTATIONAL FLUID DYNAMICS (CFD). Masters thesis, UNIVERSITAS DIPONEGORO.

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Abstract

Cooling tower merupakan komponen krusial dalam sistem pembangkitan listrik panas bumi, berperan menjaga efisiensi termal yang mendukung efisiensi sistem PLTP secara keseluruhan. Penelitian ini mengkaji kinerja termal dan evaporation loss pada cooling tower tipe induced draft–counter flow melalui pemodelan Computational Fluid Dynamics (CFD), yang divalidasi terhadap data performance test dan dibandingkan dengan metode empiris ASHRAE. Validasi menunjukkan kesalahan perhitungan rata-rata sebesar 1,8%, menegaskan bahwa CFD dapat diandalkan untuk analisis dan optimasi desain.
Hasil analisis menunjukkan bahwa variasi hot water inlet temperature (38–46 °C) meningkatkan evaporation loss (≈9–15 kg/s), menaikkan temperatur outlet, dan menurunkan effectiveness sistem. Peningkatan cold air inlet velocity (3,5–6,5 m/s) meningkatkan effectiveness dan menurunkan temperatur outlet, namun respons aktual pada performance test jauh lebih kecil dibanding prediksi CFD (slope efektivitas CFD ≈ +1,7% per 1 m/s vs lapangan ≈ +0,3%). Selain itu, heat load (±50.000–130.000 kJ/s) berkorelasi positif dengan evaporation loss, di mana performance test menunjukkan nilai tertinggi (≈14–16 kg/s), CFD berada di tengah (≈10–13 kg/s), dan ASHRAE paling konservatif. Disparitas ini mengindikasikan bahwa CFD cenderung under-predict laju penguapan akibat asumsi ideal dan pengabaian fenomena non-ideal seperti recirculation, fouling, dan drift loss.
Secara keseluruhan, CFD mampu memberikan estimasi performa yang lebih realistis dibanding metode empiris, dengan deviasi yang dapat dikalibrasi terhadap data lapangan. Oleh karena itu, pendekatan CFD direkomendasikan sebagai alat bantu dalam optimasi desain dan evaluasi performa cooling tower untuk mendukung efisiensi termal dan konservasi air pada pembangkit listrik tenaga panas bumi.
Kata kunci: PLTP, cooling tower, computational fluid dynamics (CFD), kinerja termal, evaporation loss, perpindahan panas dan massa

Cooling towers are critical components in geothermal power generation systems, playing a key role in maintaining thermal efficiency and managing water losses due to evaporation. This study investigates the thermal performance and evaporation loss of an induced draft–counter flow cooling tower using Computational Fluid Dynamics (CFD) modeling, validated against performance test data and compared with the empirical ASHRAE method. Validation results indicate a mean calculation error of 1.8%, confirming that CFD can be relied upon for analysis and design optimization.
The analysis reveals those variations in hot water inlet temperature (38–46 °C) increase evaporation loss (≈9–15 kg/s), raise outlet water temperature, and reduce system effectiveness. Increasing cold air inlet velocity (3.5–6.5 m/s) improves effectiveness and lowers outlet temperature; however, actual performance test responses are significantly smaller than CFD predictions (effectiveness slope ≈ +1.7% per 1 m/s for CFD vs ≈ +0.3% for field data). Furthermore, heat load (approximately 50,000–130,000 kJ/s) shows a positive correlation with evaporation loss, where performance test results exhibit the highest values (≈14–16 kg/s), CFD predictions fall in the mid-range (≈10–13 kg/s), and ASHRAE estimates are the most conservative. This disparity suggests that CFD tends to under-predict evaporation rates due to idealized assumptions and the omission of non-ideal phenomena such as recirculation, fouling, and drift loss.
Overall, CFD provides more realistic performance estimates compared to empirical methods, with deviations that can be calibrated against field data. Therefore, CFD is recommended as a decision-support tool for optimizing cooling tower design and evaluating performance to enhance thermal efficiency and water conservation in geothermal power plants.
Keywords: Geothermal power plant, cooling tower, computational fluid dynamics (CFD), thermal performance, evaporation loss, heat and mass transfer.
Keywords: Geothermal Power Plant (GPP), cooling tower, Computational Fluid Dynamics (CFD), thermal performance, evaporation loss, heat and mass transfer

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