Water drainage characteristics are dependent on the design of the evaporator: specifically the design of the fins and plates along with hydrophilic coating. A part of the hydrophilic coating washes off with the moisture that condenses over the evaporator core from the air-stream. Hence, water drainage characteristics of an evaporator changes with the vehicle mileage or the age of the vehicle. Since a part of the hydrophilic coating washes away, more water is retained within the evaporator at this condition. Hence, the effectiveness of the evaporator drainage deteriorates with the age of the vehicles. At this condition, the contact angle measured at the plate increases.
Author has conducted an experimental study to measure the effectiveness of hydrophilic coating from evaporators taken out from arid (9 cores) and humid areas (16 cores) as a function of vehicle mileage or vehicle age. Contact angles and water retention were measured for a number of evaporators from different OEMs. These cores are from different vehicles, with different manufacturers for the evaporators with different fin and plate design; and with different hydrophilic coatings.
Experimentally measured water retention data shows that the water retention increased for the evaporators recovered from arid and humid regions by 85 gms (+27%) for arid areas; and by 110 gms (+37%) for humid area. This data is over the base case over a span of 60,000 miles. This represents a vehicle life of 5 years (Based on average 12,000 miles/year). The measured contact angles ranged from 37 to 78°. Further details are presented in the paper.
This is the first paper in the open literature that deals with the vehicle mileage or vehicle age with the evaporator plate contact angle and surface coating of an evaporator.
