Convective coolant heat transfer in internal combustion engines

Broatch

Int.J Automot. Technol.

et al. 2008

One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80ºC and 90ºC), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.

Section: Engine Internal Cooling Circuitmentioning

confidence: 99%

Assessment of the influence of different cooling system configurations on engine warm-up, emissions and fuel consumption

Broatch

Int.J Automot. Technol.

et al. 2008

“…The heat transfer coefficient h f c was computed using a Dittus-Boelter equation modified along some of the lines indicated by Robinson et al [22] as…”

Section: Experimental Set-upmentioning

confidence: 99%

“…They stressed the importance of an accurate representation of the purely convective heat transfer accounting for the complex issues associated with the fact that the flow is undeveloped both hydrodynamically and thermally, for the sensitivity to temperature of the fluid viscosity and for surface roughness [22]. In connection with this last factor, Ramstorfer et al [23] pointed out the importance of the surface porosity in the nucleate boiling regime, showing the potential of several surface coatings for heat flux enhancement.…”

Section: Introductionmentioning

confidence: 99%

Experiments on subcooled flow boiling in I.C. engine-like conditions at low flow velocities

Broatch

Experimental Thermal and Fluid Science

et al. 2014

Subcooled boiling flow is specially attractive for engine cooling system design, as no essential changes in its architecture are required while it is still possible to take advantage of the highest rates of heat transfer associated with nucleate boiling, mostly at high engine loads. In this paper, experiments on subcooled boiling flow in representative temperature conditions were conducted with a usual engine coolant in the low velocity range, for which little information is available, even if it may be relevant when advanced thermal management strategies are used. The results were analyzed by comparison with a reference Chen-type model which provided reasonable results for relatively low wall temperatures, but with noticeable discrepancies at higher wall temperatures. Analysis of the deviations observed indicated a significant influence of the Prandtl number on the suppression factor, and the inclusion into the model of a first estimate of this effect produced a noticeable improvement in its results, thus suggesting that one such modified additive model may be useful for practical engine cooling applications.

“…Although the previous correlation was developed for straight pipes, it has been demonstrated to be useful for this application [23].…”

Section: Coolant -Wall Heat Transfermentioning

confidence: 99%

A Tool for Predicting the Thermal Performance of a Diesel Engine

Heat Transfer Engineering

Martín

et al. 2011

Abstract.This paper presents a thermal network model for the simulation of the transient response of diesel engines. The model was adjusted by using experimental data from a completely instrumented engine run under steady-state and transient conditions. Comparisons between measured and predicted material temperatures over a wide range of engine running conditions show a mean error of 7ºC. The model was then used to predict the thermal behavior of a different engine. Model results were checked against oil and coolant temperatures measured during engine warm-up at constant speed and load, and on a New European Driving Cycle. Results show that the model predicts these temperatures with a maximum error of 3ºC.3