Automotive Science and Engineering

---

This thesis looked at the effect of clay and silt soil blocking the heat transfer area of the radiator and its effect on the engine coolant through the conduct of experiments and a mathematical model developed. The results indicated that the percentage area covered resulted in a proportional increase of the inlet and outlet temperatures of the coolant in the radiator. The mathematically model developed also predicted the experimental data very well. Regression analysis pointed out that every 10% increase area of the radiator covered with silt soil resulted in an increase of about 17 oC of the outlet temperature of the radiator coolant. Similarly, using clay as a cover material, 10% of the area covered of the radiator resulted in an increase of about 20 oC of the outlet temperature of the radiator coolant. Statistical analysis pointed to the fact that the result obtained for clay, silt and the mathematical model were not significantly different. Thus, irrespective of the type of material that blocks the radiator surface area, the coolant rises with proportion of the radiator covered.

---

In this experimental study, heat transfer and pressure drop, ΔP, of a coolant nanofluid, obtained by adding alumina nanoparticles to Ethylene Glycol-water mixture (60:40 by mass), in a automotive radiator have been investigated. For this purpose, an experimental setup has been designed and constructed. The experiments have been performed for base fluid and nanofluid with different volume fractions of 0.003, 0.006, 0.009 and 0.012 and under laminar regime with various coolant flow rates of 9, 11 and 13 lit/min and two air velocities of 3.75 and 2.85 m/s. The thermophysical properties have been calculated using the recently presented temperature dependent models. According to the results, the heat transfer and ΔP increase with increasing the coolant flow and nanoparticles volume fraction. Increasing the air velocity causes enhancement of heat transfer. Although Nusselt number decreases when nanofluid is utilized, it enhances as the nanoparticles volume fraction increases. The performance evaluation using nanofluid in the car radiator shows remarkable enhancement in radiator thermal efficiency. However, the ratio of heat transfer rate to the needed pumping power (Merit parameter) decreases.

---

In this research, the effect of using three Nano fluids contains graphene oxide (GO), titanium oxide (TiO2) and aluminum oxide (Al2 O3) was analyzed on the heat transfer of the car radiator by experiment in physical conditions on the car engine. Distilled water and ethylene glycol (60:40) as the base fluid was companied with three nanoparticles contain graphene oxide, titanium oxide and aluminum oxide that each one separately with 0.1, 0.2 and 0.3 weight percent and flow rates of 10, 20, 32 and 40 liters per minute were used at normal engine temperature. After the temperature of the radiator cooling fluid reached 90 degrees Celsius and the fan was turned on for one minute, the results showed that increasing the weight percentage of nanoparticles to the base fluid increases the displacement heat transfer coefficient and most increase in the coefficient of heat transfer at 0.3 weight percent to an approximate value of 5.2% in aluminum oxide, 11.9% for titanium oxide and 28.7% for graphene oxide compared to the base fluid was received. With the increase in weight percentage, the pressure drop and Nusselt number increased.  The highest percentage increase in the radiator pressure drop for all three Nano fluids with 0.3 weight percentage and 2.2% for   aluminum oxide, 3.5% for Titanium oxide and 5.24% for graphene oxide were received.

---

One of the most important aspects of designing passenger cars is the engine cooling. This process would significantly affect the vehicle performance. This study has been conducted both theoretically and experimentally to reveal the influences of different involved parameters of cooling. The current research is implemented in order to examine the effects of 2-speed radiator fan utilization rather than the 1-speed type. For this aim, the new modified fan is considered and the experimental data are obtained to compare the results with those of the old one. Additionally, the effects of parameters such as ECU strategy, radiator fin density as well as the radiator plate geometrical properties are considered in the analysis. As a prominent result, the experimental results show a substantial effect of considering 2-speed radiator fan and choosing a better strategy for ECU on the cooling performance in the vehicle. The experimental results show that employing 2-speed fan instead of single-speed and 900 fin/m fin density instead of 780 fin/m decreases coolant outlet temperature of radiator by 6.1% and 7.1% in the same condition, respectively.
 

---

One of the main challenges in designing a vehicle's cooling system, particularly the radiator, is not considering the non-uniform airflow distribution in the radiator's characteristic performance graphs. In this study, a three-dimensional numerical analysis of the airflow passing through a QUIK vehicle and the effect of the cooling system's placement relative to the vehicle's grille in five different cases was conducted. The effect of non-uniform airflow distribution on related radiator parameters such as the Darcy number, particle diameter, and inertial term was examined. The results indicate that the optimal placement range of the vehicle's cooling system for appropriate cooling performance is very limited. Additionally, non-uniform air velocity distribution plays a significant role in the radiator pressure drop. The inertial term is more significant in non-uniform flow conditions. For larger Forchheimer numbers, the change in radiator pressure drop for uniform compared to non-uniform flow distributions is about 22%.