A hydraulic fan driven heat exchanger for automotive cooling systems
Abstract
Hydraulics are widely applied in transportation and manufacturing systems due to their high power density, design flexibility for power transmission, and ease of computer control. One fluid system application that merits investigation is the internal combustion engine advanced thermal management system which replaces the traditional mechanical coolant pump and radiator fan with computer controlled components. Although electric servo-motors may be integrated to drive these mechanical loads, the power demands often require large actuator sizes and electrical currents. An alternative to dc motors are hydraulic driven motors which offer higher torques in a smaller package space. In the paper, an automotive heat exchanger will be investigated that features a computer controlled hydraulic actuated fan. A series of dynamic models will be presented for the radiator, fan assembly, and hydraulic circuit. For comparison purposes, two radiator models are developed using heat transfer concepts for a cross flow heat exchanger. The e-NTU method is a standard methodology for heat exchanger analysis involving a logarithmic mean temperature difference of the fluids. In contrast, the Nusselt method uses temperature differential equations for fluids in cross flow to calculate an average temperature difference. Representative numerical results will be presented to demonstrate transient responses of the hydraulic components as well as the radiator temperature. Copyright © 2006 by ASME.
