Engineering and Technology Journal

Thermal Performance Investigation of a Double Pipe Heat Exchanger Using Experimental and Simulation Techniques
https://doi.org/10.30684/2412-0758.1012
Abstract
A heat exchanger is a device that transfers heat between two media. It is widely applied in various Industrial processes and power plants. Most previous studies relied either on CFD without experimental validation or on limited diameters, while this work integrates both experiments and CFD and compares three diameters. An experimental study on a counter-flow double-pipe heat exchanger with a 12 mm inner pipe was conducted to validate the CFD model. The validated model was then used to assess the effects of inner pipe diameter (12, 15, and 18 mm), flow rate, and temperature on thermal performance. For validation purposes, the experimental data were compared with simulation results for the overall heat transfer coefficient and effectiveness. The results show that the percentage error ranges between (0–12.95) % and (0–11.63) % for both the overall heat transfer coefficient and effectiveness, respectively. This, in turn, indicated an acceptable and accurate simulation model that can be reliably used for further numerical studies. In general, the findings show that the coefficients of overall heat transfer (Ui) and effectiveness (ϵ) can be controlled by selecting an appropriate inner pipe diameter and carefully managing the flow rate and temperatures. The results indicated that a 188% increase in the overall heat transfer coefficient and a 177% increase in the effectiveness can be achieved at the same flow rate and temperatures by reducing the inner pipe diameter from 18 mm to 12 mm. Finally, the study underscores the critical roles of the inner pipe dimensions as a passive technique in optimizing heat exchanger efficiency.
Highlights
1. The CFD simulation of a double-pipe heat exchanger was validated experimentally with high
accuracy.
2. Deviation between experimental and simulation results ranged were 0–12.95% for the OHTC and
0–11.63% for effectiveness.
3. Pipe inner diameter, flowrate and fluid temperatures were identified as key parameters influenc
ing thermal performance.
4. Reducing the ID pipe to 12 mm enhanced the overall heat transfer coefficient and effectiveness
by 188% and 177%
Keywords: Double pipe heat exchanger, Counter flow, CFD analysis, Heat transfer enhancement,
Difference diameters, Effectiveness, Overall heat transfer coefficient
Journal: https://lnkd.in/dgnvtdte
Issue: https://etj.uotechnology.edu.iq/journal/vol44/iss1/13/
Article: https://etj.uotechnology.edu.iq/cgi/viewcontent.cgi?article=1012&context=journal
ETJ LinkedIn: https://lnkd.in/d_8SPqAt

Metaheuristic Evaluation of Paraffin Wax-Related Flow Assurance Challenges for Optimal Productivity in Onshore Facilities
https://doi.org/10.30684/2412-0758.1011
Abstract
In this research, paraffin wax deposition models were evaluated using a multi-objective genetic algorithm (MOGA). This is a metaheuristic approach to multi-parametric solution of complex mathematical problems. The study aims to apply a suitable metaheuristic technique to analyse the parameters of paraffin wax-related flow assurance issues in onshore oil and gas facilities in Nigeria, thereby ensuring optimal productivity and operational efficiency. Thus, a paraffin wax sample collected from a typical onshore production facility was analysed in a laboratory to determine its thermophysical and transport properties and composition. These properties are the WAT, melting point, flash point, liquid density, and dynamic viscosities, respectively, given as 32 °C, 52 °C, 191 °C, 906 kg/m3 and 6.812 × 10-5kg/ms. This showed the range of safe thermal exposure for optimal flow assurance. Also, the compositional analysis revealed the molecular mass, molecular formula, structural formula, and spectral orientations of the different components of the sample. The molar volume of the heaviest component was estimated to evaluate the time required for a wax particle to diffuse a length equal to its diameter under different deposition mechanisms. The average minimum times taken by a wax particle to diffuse a length equal to its diameter by molecular diffusion, Brownian diffusion, shear dispersion, gravity settling, and thermal diffusion are respectively 1.0265 × 1016 seconds, 4.6650 × 1026 seconds, 2.0004 × 103 seconds, 9.9010 × 103 seconds and 4.7453 × 109 seconds. Therefore, maintaining the safe thermal exposure of the waxy fluid in the piping system and ensuring the residency time does not exceed the minimum of these values guarantees optimal flow assurance and operational efficiency.
Highlights
1. Laboratoryanalyses were conductedonparaffinwaxcollectedfromanonshorefacilityinNigeria.
2. Thermophysical and transport properties of paraffin wax were determined through laboratory
analysis.
3. Thesafetemperature range for the paraffin wax sample was found to be between52°Cand191°C.
4. Minimum diffusion times for paraffin wax particles were evaluated using MOGA with different
methods.
Keywords: Piping systems, Flow assurance, Paraffin wax deposition, Multi-objective, Genetic algo
rithms
Journal: https://lnkd.in/dgnvtdte
Issue: https://etj.uotechnology.edu.iq/journal/vol44/iss1/12/
Article: https://etj.uotechnology.edu.iq/cgi/viewcontent.cgi?article=1011&context=journal
ETJ LinkedIn: https://lnkd.in/d_8SPqAt

Numerical Study of Thermal Stress and Deformation in Piston and Cylinder Head Assemblies
https://doi.org/10.30684/2412-0758.1010
Abstract
This study examines the behavior of thermal stress and deformation in piston and cylinder head assemblies of internal combustion engines using numerical simulation techniques. Computational Fluid Dynamics (CFD) is employed to investigate the influence of varying thermal loads on the structural response and durability of these critical engine components. In our numerical investigation, we aimed to understand the role of temperature differences in thermal stresses and deformations within piston-cylinder head setups. These rates are indicative of the severe thermal stresses experienced by the material, which are significantly higher than typical rates observed in standard operating conditions. Results show that peak crown temperatures reach 320–400 °C, producing von Mises stresses of 150–220 MPa, which are concentrated at the ring-land region, leading to localized plastic strains of 0.1–0.3%. Radial skirt expansion of 50–150 μm and a 10–30 % reduction in contact pressure at the liner were also predicted. Parametric studies demonstrated that increasing crown thickness and enhancing cooling can lower peak stresses by 10–20%, while stronger alloys increase the allowable stress margin by 30%. A combination of these temperature variations, the materials’ characteristics, and the gaps in assembly all contribute to hotspots of stress and bending, especially in zones subjected to sharp thermal shifts, such as the top of the piston and the walls surrounding the combustion area. Beyond that, this work lays a solid groundwork for refining future engine layouts and offers practical guidance for extending the lifespan and improving the efficiency of internal combustion engines.
Highlights
1. FEA and CFD were used to study temperature distribution and thermal stresses in pistons and
cylinder heads.
2. Materials including ceramic coatings, were investigated to reduce thermal stresses and enhance
engine performance.
3. Evaluating the integrity of pistons and cylinder heads under combined thermal and mechanical
loads.
4. Design optimization studies showed that modifying piston rib structures can effectively reduce
thermal stresses and improve performance.
Keywords: Thermal, Deformation, Piston, Cylinder head, Computational fluid dynamics, Internal
combustion engine
Journal: https://lnkd.in/dgnvtdte
Issue: https://etj.uotechnology.edu.iq/journal/vol44/iss1/11/
Article: https://etj.uotechnology.edu.iq/cgi/viewcontent.cgi?article=1010&context=journal
ETJ LinkedIn: https://lnkd.in/d_8SPqAt

Enhancing R-410A Cooling Efficiency Through Strategic Utilization of Groundwater in HVAC System
https://doi.org/10.30684/2412-0758.1005
Abstract
Utilizing geothermal cooling for refrigerants is considered cost-effective, innovative, and environmentally sustainable. This method leverages the Earth’s stable subsurface temperature to enhance cooling efficiency. In this study, the system was developed by modifying the condenser from an air-cooled configuration to a water-cooled configuration, ensuring enhanced operational clarity through the implementation of water-based cooling. This study introduces a novel integration of a groundwater-based indirect cooling loop with a conventional R-410A split-type system, tailored for hot-arid climates such as Karbala, Iraq. Unlike previous studies focusing on direct ground coupling or alternative refrigerants, this approach emphasizes a real-environment experimental setup combining existing air-conditioning technologies with subsurface cooling. Using a U-shaped heat exchanger, an advanced system was experimentally employed to harness the geothermal cooling effect at a depth of 24 meters. This heat exchanger, extending to the same depth, was utilized to cool water supplied from a primary reservoir. The cooled water was subsequently used to chill the refrigerant R-410A through another heat exchanger. The inlet water to the heat exchanger responsible for cooling R-410A was tested at three different temperature levels: low, medium, and high. Additionally, the impact of the inlet water flow rate on the refrigerant cooling performance was investigated. Various flow rates were tested. It was concluded from this experimental study that increasing the water flow rate into the water-refrigerant heat exchanger resulted in a decrease in refrigerant temperature. Also, the high-level water flow rate (0.3 Kg/s) yielded the highest reduction in refrigerant temperature, reaching below 10°C. Additionally, this flow rate provided the highest coefficient of performance for the cooling system, 5.49, and the lowest energy consumption.
Keywords: Groundwater, Water-water heat exchanger, The borehole, R-410A, HVAC
Highlights
1. Ageothermal-based refrigerant cooling system was designed and successfully operated.
2. Borehole water temperatures varied due to tank heat, flow rate, and groundwater changes.
3. Higher water flow rates significantly improved the cooling of R-410A refrigerant.
4. The system reached a COP of 5.49, exceeding typical split unit and test scenario values.
5. The system met Montreal Protocol standards with an EER of 18.72.
Journal: https://lnkd.in/dgnvtdte
Issue: https://etj.uotechnology.edu.iq/journal/vol44/iss1/6/
Article: https://etj.uotechnology.edu.iq/cgi/viewcontent.cgi?article=1005&context=journal
ETJ LinkedIn: https://lnkd.in/d_8SPqAt