You design a new type of absorber that has a number of slanted plates with falling films on each plate and gas flowing counter to the liquid. In the laboratory, the new system works well. Its high mass transfer coefficients result in excellent separation. When a larger unit is tested in the plant, it does not perform well. You estimate the mass transfer coefficients in the plant and find they are less than half that observed in the lab. The larger unit is brought to the lab, cleaned, set up, and tested. The resulting mass transfer coefficients are about the same as previously observed in the lab. If operating conditions (angle of device, flow rate, feed composition) are the same in the plant and in the lab, what are the most likely reasons for the lower performance in the plant?