Heat Transfer Analysis of Helical Coil Condenser for Bioethanol Purification

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FORMOSA NEWS - Helical Coil Condenser Enhances Bioethanol Purification Efficiency By 32 Percent. Researchers from three Indonesian universities have successfully validated the use of a helical coil condenser to accelerate and optimize the purification of bioethanol, a critical renewable energy alternative. The experimental thermal study, published in 2026, was conducted by Djoko Wahyudi from Universitas Panca Marga, Yusuf Hendrawan and Nurkholis Hamidi from Universitas Brawijaya, and Dwi Irawan from Universitas Muhammadiyah Metro. Their findings demonstrate that adjusting reactor temperatures within a curved pipe condensing system significantly improves steam condensation efficiency, marking a vital step forward for the scalable production of clean biofuels.

Thermal Engineering to Meet Growing Clean Energy Demands
The global demand for sustainable energy alternatives continues to rise, driven by rapid population growth, industrial expansion, and the inevitable depletion of fossil fuel reserves. Bioethanol has emerged as a highly promising renewable fuel due to its biodegradability and its potential to achieve carbon neutrality. However, a major bottleneck in bioethanol production lies in the purification stage. Traditional vacuum distillation requires substantial energy to vaporize and subsequently condense the liquid mixture back into high-purity ethanol. To address this challenge, the research team focused on optimizing the condenser, which is the core component responsible for changing vapor back into liquid. Unlike conventional straight-tube configurations, Djoko Wahyudi and his co-authors utilized a helical coil geometry. The curved architecture of a helical coil induces a unique physical phenomenon known as secondary flow, or Dean vortices. This swirling flow creates turbulence, improves fluid mixing, and reduces thermal resistance near the pipe walls. Ultimately, this structural innovation accelerates convective heat transfer, making the entire phase-change process far more energy-efficient.

A Practical Experimental Approach Using Temperature Variations
The quantitative experimental research design utilized a laboratory-scale, 20-liter bioethanol purification unit integrated with a custom-engineered helical coil condenser. To maintain continuous heat removal from the system, a high-capacity external cooling water pump circulated water through the shell side at a steady flow rate of 417 liters per minute. The researchers evaluated the thermal performance of the system under two distinct operational conditions: a lower reactor heating temperature of 58°C and a higher heating temperature of 71°C. The testing durations spanned across precise intervals from 1,800 seconds (30 minutes) to 7,200 seconds (120 minutes). To ensure absolute data reliability, an automated digital data logger recorded critical thermodynamic parameters including inlet steam temperature, steam mass flow rate, and condensate film mass every 100 seconds under steady-state conditions.

Key Findings: Higher Operational Temperatures Unlock Greater Efficiency
The experimental data compiled by the team revealed that reactor temperature variations profoundly alter uap dynamics and condenser performance. The primary findings from the comparative thermal analysis include:

• Operational Reactor Temperature at 58°C: This setting generated an average inlet steam temperature of 46.25°C entering the condenser. The steam mass flow rate reached $1.5 \times 10^{-4}$ kg/s, while the condensate film mass rate was limited to $30 \times 10^{-4}$ kg/s. This resulted in a final condensation efficiency of 20.26%.
  
• Operational Reactor Temperature at 71°C: This elevated setting produced a significantly higher inlet steam temperature of 59.00°C. The steam mass flow rate increased to $1.9 \times 10^{-4}$ kg/s, and the condensate film mass rate more than doubled to $62 \times 10^{-4}$ kg/s. Consequently, the system achieved a superior condensation efficiency of 32.66%.
  

A notable anomaly observed in the study was that while the lower temperature condition (58°C) yielded a higher total accumulated heat energy, it resulted in poorer condensation efficiency. This phenomenon confirms that distillation performance is not dictated by raw energy accumulation alone. Instead, the higher thermal input at 71°C strengthens the phase-change intensity and accelerates vapor transport toward the cooling surfaces, optimizing how effectively the energy is utilized.

Real-World Impact and Industrial Implications
The collaborative insights generated by the researchers from Universitas Panca Marga, Universitas Brawijaya, and Universitas Muhammadiyah Metro offer immediate practical benefits for green energy industries. By replacing conventional straight-tube heat exchangers with optimized helical coil configurations and maintaining higher operational reactor temperatures, bioethanol manufacturing plants can substantially decrease their total processing time and energy expenditures. These engineering refinements provide policymakers and businesses with a viable blueprint to lower the production costs of domestic biofuels, making renewable alternatives economically competitive with fossil fuels.

Author Profiles
Djoko Wahyudi, S.T., M.T. is a faculty member and researcher at Universitas Panca Marga, Probolinggo, Indonesia. He specializes in thermal engineering, phase-change heat transfer, and renewable energy conversion systems.
Prof. Dr. Ir. Yusuf Hendrawan, S.TP., M.App.LifeSc. is a Professor at the Faculty of Agricultural Technology, Universitas Brawijaya, Malang, Indonesia. His field of expertise encompasses bioprocess engineering, agricultural automation, and bioenergy optimization.
Dr. Eng. Nurkholis Hamidi, S.T., M.Eng. is a senior lecturer in the Department of Mechanical Engineering at Universitas Brawijaya, Malang, Indonesia. He focuses on advanced thermodynamics, combustion technology, and alternative fuel systems.
Dwi Irawan, S.T., M.T. is an academic and researcher in the Mechanical Engineering Study Program at Universitas Muhammadiyah Metro, Lampung, Indonesia. His research focus includes thermal system design and industrial energy efficiency.

Sources

Djoko Wahyudi, Yusuf Hendrawan, Nurkholis Hamidi, Dwi Irawan. Heat Transfer Analysis of Helical Coil Condenser for Bioethanol Purification. Formosa Journal of Applied Sciences (FJAS), Volume 5, Nomor 6, Tahun 2026. Halaman 1421-1436.
DOI: https://doi.org/10.55927/fjas.v4i11.72
URL: https://journalfjas.my.id/index.php/fjas