TiTich - the surface texture of the Acrylic top has no significant affect, since their is almost no heat flux through the Acrylic (very poor thermal conductivity). It also would have minimal impact on the flow on the bottom of the channel and the lower 2/3rds of the side walls.
That being said - a metal top is better from a thermal standpoint, amount depending on the thickness and height of the channel walls and how good of a thermal interface their is between the channel walls and the top { the top helps to conduct heat across the block and helps to conduct heat to the water }. However, if the walls are too thin or too tall, then you get to the point of diminishing returns since their wouldn't be very much thermal energy conducted to the top of the walls anyway.
|