This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Study of Motor Oil Cooling at Low Reynolds Number in Multi-Port Narrow Channels
Abstract:
Mini and micro-scale channels have drawn researchers'
attention in the past three decades. The use of these tiny channels
in a heat exchanger is considered as one of the pioneered works on
the narrow channels as minichannels provide high heat transfer
rates per unit volume. Motor oil, known as engine oil, is one of
the vital fluids in automotive applications. Its cooling process is
confronted by its thermo-physical properties, especially viscosity,
which makes this process difficult.
In current investigations, experimental endeavors have been
performed using a closed loop thermal wind tunnel to verify the
aptness of cooling the motor oil through a cross-flow minichannel
heat exchanger. The prototype heat exchanger consists of 3
circuits; each circuit has five slabs which are connected to each
other by four serpentines. There are 68 channels of 1 mm circular
diameter drilled through each slab. The minichannel heat exchanger
comprises of wavy fins arranged parallel to the flow of air. The
inlet temperature of the motor oil was kept constant at 75°C while
the air inlet temperatures were varied within the range of 20°C and
40°C.
The flow of the oil fell in the laminar regime due to its high
viscosity, which consequently resulted in low Reynolds numbers
(Re). The range of was found to be from 0.85 to 3.5 whereas the air
flow rates were between 6 m/s and 18 m/s. Correlations were
developed between the oil Nusselt number and oil Re and Prandtl
numbers. The effect of Re on the heat transfer coefficient, NTU,
and effectiveness were investigated. The results were compared with
the findings of another highly viscous fluid where a similar test
specimen was used and same trends were observed.