On design and analysis of a concentric tube micro fin heat exchanger for applications of tire pyrolysis lube oil cooling

Abstract

Concentric tube heat exchangers are widely used as lube oil coolers in large internal combustion engines. They are particularly preferred because of simple manufacturing, lower area, and better heat transfer characteristics. With the growing use of unconventional fuel-based lubricants, their design is continuously improved to achieve the required heat transfer characteristics. One of the emerging alternative oil is Tire Pyrolysis Oil (TPO) to minimize tire waste and achieve the waste-to-energy objective. The TPO is employed not only as diesel blended fuel but also as a lube oil because of its satisfactory tribological properties. The present work provides a detailed design and analysis of a concentric-tube micro-fin-based lube oil cooler for TPO applications. The design encompasses the thermal, hydraulic, and economic characteristics of the heat exchanger subjected to TPO, Ethylene Glycol (EG), and Crude Oil (CO). To achieve this a robust numerical model is developed and implemented using engineering equation solver software. The model is validated with experimental data first. Then a detailed parametric analysis is done to investigate the heat exchanger performance. It was observed that TPO offered a better heat transfer coefficient along with lesser power input and cost compared to EG and CO. For instance, in the case of a mass flow rate 0.1 kg/s, the heat transfer per unit pressure drop is highest for TPO with 5.86 m/sK followed by CO with 5.12 m/sK and EG with 0.3876 m/sK. Similarly, the annual operational cost is calculated as 27.7 k$, 31.4 k$, and ∼ 80.8 k$ for the TPO, CO, EG which shows the superiority of TPO as lube oil for engine applications. Based on thermal, hydraulic design and economic analysis, it is concluded that tire pyrolysis oil (TPO) is used in the concentric tube micro fin heat exchanger for applications of oil cooling.