STUDI KOMPARASI TERMODINAMIKA DAN PEMILIHAN FLUIDA KERJA OPTIMAL PADA ORGANIC RANKINE CYCLE (ORC) BERBASIS KOMPUTASI HELMHOLTZ EQUATION OF STATE MENGGUNAKAN PUSTAKA COOLPROP

Abstract

ABSTRACT

The utilization of low- to medium-temperature heat sources remains constrained by the relatively low efficiency of conventional water-based Rankine cycles. Although the Organic Rankine Cycle (ORC) has been widely developed as an effective technology for converting low-grade heat into electricity, comparative studies on working fluid selection using a computational approach based on the Helmholtz Equation of State (EOS) through the CoolProp library remain limited. This study is important because it provides a scientific basis for identifying working fluids capable of delivering optimal thermodynamic performance while satisfying operational requirements. The objective of this study is to compare the thermodynamic performance of five working fluids R245fa, R1233zd(E), Isobutane, R134a, and n-Pentane in a subcritical Organic Rankine Cycle operating with a heat source temperature of 120°C. The study employed computational simulations using Python integrated with the CoolProp library based on the Helmholtz Equation of State to evaluate the thermodynamic properties of each working fluid. The results demonstrate that working fluid selection significantly affects thermal efficiency, net power output, and system feasibility. n-Pentane exhibits the best overall performance, whereas R1233zd(E) represents a competitive alternative for applications requiring higher safety standards. In contrast, R134a is unsuitable under the investigated operating conditions because its operating temperature exceeds the critical limit. These findings confirm that the thermophysical characteristics of the working fluid are the primary determinant in optimizing Organic Rankine Cycle performance for low-temperature heat source applications.

ABSTRAK

Pemanfaatan sumber panas bersuhu rendah hingga menengah masih menghadapi kendala karena efisiensi siklus Rankine konvensional berbasis air relatif rendah. Meskipun Organic Rankine Cycle (ORC) telah banyak dikembangkan sebagai solusi konversi energi panas suhu rendah, kajian komparatif mengenai pemilihan fluida kerja menggunakan pendekatan komputasi berbasis Helmholtz Equation of State (EOS) melalui pustaka CoolProp masih terbatas. Penelitian ini penting untuk memberikan dasar ilmiah dalam menentukan fluida kerja yang mampu menghasilkan kinerja termodinamika optimal sekaligus memenuhi aspek operasional. Penelitian bertujuan membandingkan performa termodinamika lima fluida kerja, yaitu R245fa, R1233zd(E), Isobutane, R134a, dan n-Pentane, pada sistem Organic Rankine Cycle subkritis dengan temperatur sumber panas 120°C. Metode yang digunakan berupa simulasi komputasi menggunakan Python dan pustaka CoolProp berbasis Helmholtz Equation of State untuk menghitung parameter termodinamika setiap fluida kerja. Hasil penelitian menunjukkan bahwa pemilihan fluida kerja berpengaruh signifikan terhadap efisiensi termal, kerja bersih, dan kelayakan operasi sistem. n-Pentane memberikan performa keseluruhan terbaik, sedangkan R1233zd(E) menjadi alternatif yang kompetitif untuk aplikasi dengan persyaratan keselamatan tinggi. Sebaliknya, R134a tidak layak digunakan pada kondisi operasi yang dikaji karena melampaui batas kritisnya. Temuan ini menegaskan bahwa karakteristik termofisika fluida kerja merupakan faktor utama dalam optimasi kinerja Organic Rankine Cycle berbasis sumber panas bersuhu rendah.