Thermal resistance of the evaporator is calculated by
1 / K = (1/a1) + (δ / a) + Ri + (1/a2)
① tube steam condensation resistance 1/a1 generally small, but it should be noted that the heating chamber and remove non-condensable gas, or non-condensable gases continue to accumulate in the heated indoor, will significantly increase the thermal resistance;
② wall thermal resistance δ / a can generally be ignored;
③ scale the side of the inner wall layer of liquid thermal resistance Ri depends on the nature of the solution, the movement of the liquid tube. Reduce the fouling layer thermal resistance is regular cleaning of heating, speed up the fluid circulation rate, or by adding inhibitors to trace delaying the formation of fouling layer; in dealing with the material can be crystallized by adding a small amount of seed, the crystallization of the main body of the solution as much as possible, rather than precipitation in the heating surface;
④ of boiling to the thermal resistance 1/a2 mainly on the flow of boiling liquid.