Design Optimization of Cooling System for a Tractor Engine Using Ethylene Glycol-Water Base Fluid

Abstract

An experimental study was conducted to evaluate the thermal performance of a tractor diesel engine cooling system using a 50:50 ethylene glycol (EG)–water coolant. The objective was to characterize how cooling parameters vary with engine operating conditions. A tractor engine was coupled to a dynamometer and cooled by a radiator in a closed loop. Temperatures, flow rate, engine speed, exhaust losses, and brake power were measured. Results show that the coolant temperature drop across the radiator remained nearly constant (~3°C) over 1000–2000 rpm. Exhaust heat loss rose nearly linearly with speed (from ?13 kW at 1000 rpm to ?32 kW at 2000 rpm), indicating more waste heat at higher loads. Brake thermal efficiency peaked at about 37.5% around 1400 rpm, then declined at higher speeds, consistent with increased heat and friction losses. Flywheel power reached ?41 kW at 1800 rpm and plateaued. Increasing coolant flow rate elevated the convective heat-transfer coefficient and heat removal rate. In summary, the cooling system-maintained engine temperature effectively, with best performance in the mid-RPM range. The 50:50 EG–water mixture provided adequate heat rejection, but its ~20% lower heat capacity requires slightly higher flow (?15–20%) than pure water.

Introduction

The study addresses the critical need for effective thermal management in agricultural tractor diesel engines, which operate under challenging conditions such as long hours, high ambient temperatures, and dusty environments. Efficient cooling systems are essential to protect the engine, reduce fuel consumption, and extend operational lifespan.

A common coolant used is a 50:50 mixture of ethylene glycol (EG) and water, which balances thermal performance, freeze protection, and corrosion inhibition better than pure water. However, this mixture affects system parameters like flow rate, heat transfer, and radiator design due to its altered physical properties.

The research experimentally evaluates the thermal behavior of a tractor engine cooled by this EG-water mixture across varying engine speeds (1000–2000 RPM). Key measurements included coolant temperature drop, exhaust heat loss, flywheel power output, convective heat transfer coefficient, and engine brake thermal efficiency.

Findings show:

• Coolant temperature drop across the radiator remains stable (~2.7–3.5°C) over the tested RPM range.

• Thermal power lost through exhaust gases rises steadily with RPM (from ~13 kW to over 32 kW).

• Engine brake thermal efficiency peaks around 1400 RPM (~37.5%) and declines at higher speeds.

• Flywheel power increases with RPM up to 1800 RPM, then plateaus (~41 kW).

• Convective heat transfer coefficient and total heat transfer rate increase linearly with coolant flow rate, improving radiator performance.

• Radiator successfully dissipates increasing thermal power proportional to engine speed.

• Exhaust gas temperature rises from 455°C to nearly 480°C as RPM increases, highlighting heat load growth.

The results underscore the importance of optimizing cooling system components (coolant type, flow rate, radiator size) and operational parameters (engine speed) to enhance engine reliability, efficiency, and thermal management in agricultural tractors.

Conclusion

This experimental analysis on a tractor diesel engine cooling system using a 50:50 ethylene glycol-water mixture demonstrated the system’s efficiency across a wide RPM range. The results showed that while flywheel power and exhaust heat increase with engine speed, the radiator was capable of maintaining effective thermal performance, with only minor changes in coolant temperature drop. 1) The study verified that brake thermal efficiency peaked at around 1400 RPM, indicating this range as optimal for balancing power output and heat rejection. At this point, the engine operated with the highest efficiency and minimal thermal stress. Additionally, the exhaust gas temperatures and power losses tracked engine RPM closely, which validates the cooling system’s ability to scale with thermal demand. 2) The results showed that as coolant flow rate increased, the convective heat transfer coefficient and the heat transfer rate also increased, confirming that forced convection plays a dominant role in thermal management. This implies that by optimizing pump performance and coolant flow paths, one can significantly improve the cooling efficiency of the system. 3) Furthermore, the study reinforces that despite the slightly lower specific heat of ethylene glycol-based coolants, they are highly effective when used in the correct ratio with water. The additional benefits such as freeze protection, anti-corrosion properties, and higher boiling point make them ideal for harsh agricultural conditions. In conclusion, this research highlights the importance of cooling system optimization in improving engine durability and performance in tractors. Future scope includes incorporating nanofluid additives, adaptive flow control systems, and CFD-based design tools to further enhance cooling performance under dynamic operating conditions.

References

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Copyright

Copyright © 2025 Mahendra Singh Parwal, Anand Baghel. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.