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Research Papers: Internal Combustion Engines

# A Convective Mass Transfer Model for Predicting Vapor Formation Within the Cooling System of an Internal Combustion Engine After Shutdown

[+] Author and Article Information
Rocco Piccione

Department of Mechanics, University of Calabria, 87030 Arcavacata di Rende, Cosenza, Italyr.piccione@unical.it

Antonio Vulcano

Department of Mechanics, University of Calabria, 87030 Arcavacata di Rende, Cosenza, Italyalvulcano@unical.it

Sergio Bova

Department of Mechanics, University of Calabria, 87030 Arcavacata di Rende, Cosenza, Italys.bova@unical.it

J. Eng. Gas Turbines Power 132(2), 022804 (Nov 02, 2009) (10 pages) doi:10.1115/1.3126262 History: Received October 02, 2008; Revised March 25, 2009; Published November 02, 2009; Online November 02, 2009

## Abstract

In the usual liquid cooling system of an internal combustion engine a centrifugal pump is driven by the crankshaft and imposes a coolant flow, which transfers heat from the engine walls to the radiator. Therefore, as the engine is switched-off, the coolant flow also stops, while metal temperature may be particularly high after a period of high load operation; coolant vaporization in the cylinder head passages may occur in these conditions, with a pressure increase inside the cooling circuit. A numerical dynamic model was developed to predict this phenomenon, often called after-boiling among engine manufacturers. The model structure includes thermodynamic equations to compute heat transfer as well as mass transfer equations to determine the vaporized mass of the coolant, which occurs in cylinder head passages and the vapor condensation within the radiator. The developed mathematical model was validated against test data carried out on a production four-stroke spark-ignition engine, and simulation results show good agreement with experimental data.

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## Figures

Figure 10

(a) Behavior of coolant pressure, (b) vaporized mass in the cooling system, and (c) leaked coolant for different levels of coolant fluid in the radiator expansion tank

Figure 9

(a) Effect of psat parameter on coolant pressure, (b) vaporized mass in the cooling system, and(c) leaked coolant

Figure 8

(a) Changes in coolant pressure, (b) vaporized mass in the cooling system, and (c) leaked coolant with a 10% variation of hmA parameter

Figure 7

Comparison of measured (solid lines) and predicted (dash lines) values: (a) vaporized mass in the cooling circuit and (b) leaked coolant

Figure 5

Ad hoc test for determination of the averaged value for Tf: pressure evolution in the “sealed” cooling circuit (relief valve blocked)

Figure 4

Schematic representation of a radiator-cap pressure valve

Figure 3

Schematic representation of mass transfer process in the coolant contained in cylinder head passages of an internal combustion engine

Figure 2

Flow chart of the zero-dimensional two-phase model

Figure 1

(a) Time history of coolant pressure and temperature at engine outlet. (b) Temperature evolution in the cylinder block and in the engine head. Baseline case: time of idle operation 5 s; initial condition at WOT; standard length of cooling circuit.

Figure 6

Comparison of measured (solid lines) and predicted (dash lines) values: (a) coolant pressure and (b) head and cylinder block temperature

## Errata

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