Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Steady-state simulation of the air-conditioning system of a hybrid vehicle
Submission Author:
Leonardo Caron , SC
Co-Authors:
Leonardo Caron, Christian Hermes, Diogo Lôndero Da Silva
Presenter: Leonardo Caron
doi://10.26678/ABCM.ENCIT2022.CIT22-0260
Abstract
The development and commercialization of hybrid and electric vehicles have been drastically increased over the past years. This new concept presents several benefits, such as the reduction of direct emission of polluting gases, but also brings challenges related to the efficient use of energy stored in batteries. Among the different subsystems present in hybrid vehicles, the climate control system has a very significant effect on energy consumption. For this reason, the main purpose of this paper is to develop a steady-state mathematical model for an automotive air conditioning system and use it to identify energy efficiency opportunities. The heat exchangers are modeled based on the effectiveness method, being each tube of the heat exchanger divided into nonoverlapping control volumes. Heat transfer, for each element, is calculated considering average properties among inlet and outlet conditions and the total heat transfer is the sum up of those calculated at each control volume. Compressor model is based on semi-empirical equations, where data from a compressor catalogue was used to determine the fitting coefficients. In order to simulate the AC system cooling mode, both condenser subcooling and evaporator superheating were imposed while an isenthalpic expansion device was considered. Based on geometrical input data to heat exchangers, such as total heat transfer area and refrigerant circuitry, a Newton-like method is used iteratively to obtain the output parameters. Mathematical convergence is obtained when the heat transferred in heat exchangers are equal to the heat calculated on the refrigeration loop with superheating and subcooling imposed. As a result, the model comes out with the heat exchanger temperature profile and heat duty, the working pressures, the compressor power and the coefficient of performance (COP). The simulations show that a decrease in the compressor speed from 6000 rpm to 3000 rpm increases the COP by approximately 50%. In addition, it was observed that the latent thermal load exceeds the sensible one when the air relative humidity is above 55%.
Keywords
Automotive Air Conditioning, energy efficiency, electric vehicle
