Proceedings of COBEM 2009 |20 th International Congress of Mechanical Engineering Copyright © 2009 by ABCM November, 15 - 20, 2009, Gramado, RS, Brazil DIMENSIONING PROCEDURE OF COOLANT RADIATORS FOR TRUCKS AND BUSES Guilherme da Silva Rosa Agrale S/A – Department of Engineering BR116, Km145, nº 15104 – 95059.520 – Caxias do Sul – RS – Brazil E-mail: grosa@agrale.com.br Diogo Lusa Agrale S/A – Department of Engineering BR116, Km145, nº 15104 – 95059.520 – Caxias do Sul – RS – Brazil E-mail: dlusa@agrale.com.br Carlos Roberto Altafini University of Caxias do Sul – Department of Mechanical Engineering Rua Francisco Getulio Vargas, 1130 – 95001.970 – Caxias do Sul - RS – Brazil E-mail: craltafi@ucs.br Paulo Roberto Wander University of Caxias do Sul – Department of Mechanical Engineering Rua Francisco Getulio Vargas, 1130 – 95001.970 – Caxias do Sul - RS – Brazil E-mail:prwander@ucs.br Abstract. The coolant radiators are fundamental components to the operation of internal combustion engines, and its sizing, particularly, frontal area, should be sufficient to allow the appropriate heat transfer from the engine. This work describes a procedure for calculating the frontal area of radiators to the liquid coolant, especially applicable to trucks and buses. The procedure consists on the determination of the heat rejected by the liquid coolant (water), which is based on the energy associated to the fuel burnt on combustion chambers, or technical information by radiator suppliers, and or from the power developed by the engines. A description of the cooling test for vehicle approval is contained in this work, as well as an equation of the air to boil (ATB) is used for the test validation. A flowchart to calculate the radiator frontal area is proposed. The calculation procedure developed proved to be very accurate when compared with the results of cooling tests (three tests were performed). In general, the temperature results of the air and water (in several points of the system) obtained on calculations, agreed with the values measured in the cooling tests. The worksheet allows evaluate the behavior of the coolant system studied, being very useful in the estimation of frontal area of the radiator's vehicle. Keywords: liquid coolant system, cooling tests, air to boil (ATB), radiator, energetic balance. 1. INTRODUCTION Water radiators on vehicular applications are responsible by heat dissipation in mainly of internal combustion engines and also by other sources of heat, like water/oil heat exchanger of automatic transmissions. The radiator must ensure the heat transfer, dissipating heat through the circulating air (Bosch, 2005). When engines need a higher performance or when there is a small space for installation, the better layout indicated is the radiator with thin tube and corrugated fins (SAE J631, 1988), and this type is the most currently used by vehicular assemblers. The cooling system should be compact, low weight and its installation should occupy the smallest space as possible (Basshuysen e Schafer, 2004). In vehicle design like trucks and buses is important to meet all versions and variations that each vehicle may have, this is necessary for customizing a cooling package for all needs and avoid different developments for each application. Cooling system design need a long time for 3D components modeling for further evaluation in CFD software (Computational Fluid Dynamics). For this reason in some situations the design is based on previous application, and validation is done with a test in track run called cooling test, where is determined the ATB (air to boil) temperature, being this the main methodology used by engine manufactures with application in vehicles. To minimize costs in development and ensure that the selected cooling package meets the system thermal rejection, this work shows a calculation methodology that helps engineers and designers in determining the frontal area of the water radiators. The calculation methodology is based on cooling air conditions, responsible by heat rejection in radiator. To help the calculations an electronic worksheet with the EXCEL® application (by MICROSOFT) was developed. This worksheet has the intention to simulate different conditions and enable value iterations when necessary in some calculations.