# Impact of Heat Exchanger Effectiveness and EGR on Energy and Emission Performance of a CI Engine
## 2 Materials and Methods
### Methodology of Experimental Research
Type-K thermocouples were used to measure the coolant temperature before the heat exchanger (T\({}_{1}\), \({}^{\circ}\)C) and after the heat exchanger (T\({}_{2}\), \({}^{\circ}\)C), as well as the air temperature entering the heat exchanger from the turbocharger (T\({}_{3}\), \({}^{\circ}\)C) and the air temperature exiting the heat exchanger toward the engine (T\({}_{4}\), \({}^{\circ}\)C) (see Figure 1). The temperature measurement accuracy was \(\pm\)1.5 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Value** & **Units** \\ \hline Number of cylinders & 4 & - \\ Bore & 79.5 & mm \\ Stroke & 95.5 & mm \\ Displacement & 1896 & cm\({}^{3}\) \\ Compression ratio & 19.5 & - \\ Rated power & 66 & kW \\ Rated speed & 4000 & rpm \\ Peak torque & 180 & Nm \\ Peak torque speed & 2000–2500 & rpm \\ \hline \end{tabular}
\end{table} 
Table 1: Engine technical specifications. \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Measurement** & **Resolution** & **Units** \\  & **Limits** & **Resolution** & **Units** \\ \hline CO & 0–10 & 0.01 & \% Vol. \\ CO\({}_{2}\) & 0–20 & 0.1 & \% Vol. \\ O\({}_{2}\) & 0–25 & 0.01 & \% Vol. \\ HC & 0–20,000 & 1 & ppm Vol. \\ NO\({}_{\rm x}\) & 0–5000 & 1 & ppm Vol. \\ Lambda, \(\lambda\) & 0–9.999 & 0.001 & - \\ Absorption & 0–99.99 & 0.01 & m\({}^{-1}\) \\ (K-Value) & & & \\ Opacity & 0–100 & 0.1 & \% \\ \hline \end{tabular} \({}^{1}\) The device complies with the following standards and approvals: OIML R99 Class I, ISO 3930 [41], ECE R24 [42], and IEC 801-1/2/3/4.  
\end{table} 
Table 2: Technical specifications of the AVL DiCom 4000 \({}^{1}\) exhaust gas analyzer. The experiments were carried out at an engine speed of 2000 rpm, which allows the broadest usable torque range to be achieved. The engine was subjected to loads of 30 Nm, 60 Nm, and 90 Nm, corresponding to BMEP of 0.2 MPa, 0.4 MPa, and 0.6 MPa, respectively. These values represent low to medium engine load conditions (6.3 kW, 12.6 kW, and 18.9 kW), which are characteristic of typical urban transient driving conditions. Test No. 1--HEE 0%. Prior to the test, the coolant flow through the heat exchanger was completely shut off by closing the fluid valves in order to prevent the cooling of the compressed and heated air flowing from the turbocharger into the engine. Type-K thermocouples, installed before and after the heat exchanger, recorded the temperature of the incoming and outgoing compressed air. Data were collected with the exhaust gas recirculation system both activated and deactivated. The EGR ratio was approximately estimated based on the observed reduction in intake air mass. It was determined that during EGR operation, the recirculated exhaust gas fraction decreased with increasing engine load, reaching approximate values of 0.28, 0.22, and 0.19, respectively. The EGR system was deactivated by disconnecting the electronic control connector from the vacuum solenoid controlling the EGR valve. Under these conditions, the ECU did not register any diagnostic fault codes (DTCs) related to the engine control system. During the experimental investigation, the ROSS-TECH VCDS diagnostic tool (RossTech, LLC, Montgomery County, PA, USA) was used to retrieve real-time operational data from the engine's ECU via the OBDII interface, including the start of injection (SOI) timing. Deactivation of the EGR system resulted in a minor shift in SOI timing (up to 0.5\({}^{\circ}\) crank angle), which had no significant impact on the engine's energy efficiency or exhaust emission parameters. Test No. 2--HEE 50%. Before the test, the coolant valves were opened to 50%, allowing partial cooling of the airflow through the heat exchanger. Type-K thermocouples measured the temperature of the coolant entering and exiting the heat exchanger, as well as the air temperature before and after the heat exchanger. Measurements were conducted under the same engine operating conditions as in Test No. 1. Test No. 3--HEE 100%.