How to determine the decrease in heat transfer efficiency of low-temperature evaporation equipment

Combining operating parameters, production capacity, appearance phenomena, and data comparison, it can be divided into three categories: intuitive judgment, data monitoring, and segmented verification. It can be quickly self checked and sorted from easy to difficult:

1、 Visual phenomenon judgment (on-site visual/physical perception, fastest recognition)

The evaporation rate significantly slows down

Under the same feed rate and original parameters, the rate of liquid level decrease significantly slows down, and the time required to concentrate the same volume of waste liquid significantly increases.

Abnormal overflow and boiling of equipment

Insufficient heat exchange leads to uneven heat distribution, partial overheating of the feed liquid, frequent tumbling, foam overflow, and severe boiling.

Abnormal surface temperature of cavity/pipeline

The shell of the heat exchanger and the steam pipeline are too cold, and the distinction between hot and cold is not clear; Or uneven temperature difference or abnormal condensation may occur locally.

Reduced output of distillate

The continuous decrease in the flow rate of condensate water directly reflects insufficient steam production under the premise of normal cooling system.

2、 Comparison and judgment of operating parameters (core basis, accurate judgment)

Based on the rated operating conditions and historical normal operation data of the equipment, compare the following indicators:

Temperature index

Under the same vacuum degree, the actual temperature of the material liquid is higher than the normal range; Or the output temperature of the heating source is very high, but the temperature of the material liquid rises slowly.

The temperature difference between the inlet and outlet of the cooling water decreases: under normal operating conditions, there is a significant temperature drop, and after the heat exchange deteriorates, the temperature difference between the inlet and outlet water continues to decrease.

Vacuum and pressure

The difficulty of maintaining the set vacuum level has increased, and the vacuum pump frequently operates at high loads; The negative pressure of the system fluctuates frequently and is difficult to stabilize.

Energy consumption changes

Heating power, steam consumption, and electricity consumption have significantly increased year-on-year, but evaporation capacity has not increased, which is a typical characteristic of heat transfer attenuation.

Loop state

The operation noise and vibration of the material liquid circulation pump increase, and the pressure difference in the pipeline rises, indicating that the heat exchange surface is scaled and the flow is blocked.

3、 Auxiliary judgment of water quality and material status

Deterioration of distillate water quality

The conductivity, TDS, and COD of the condensate water have increased inexplicably, and after excluding the problem of feed water quality, it is mostly due to poor heat transfer that mist entrainment occurs.

Abnormal concentrated solution

The viscosity and crystallization amount of the concentrated solution suddenly increase, and under the same concentration ratio, the boiling point continues to rise.

4、 Standardized verification methods (regular testing, quantitative judgment)

Historical data benchmarking

Establish an equipment operation ledger to record under normal operating conditions: evaporation rate, temperature and pressure of cold and hot media, energy consumption, and vacuum degree.

When multiple indicators deviate from normal values for 2-3 consecutive shifts, it can be determined that the heat exchange efficiency has decreased.

Shutdown and disassembly inspection

Open the end caps of the heat exchanger, plates, and tube bundles, and observe the inner walls: if scale, mud, salt crystals, and oil stains adhere, it directly proves that the heat exchange surface is contaminated and the efficiency is damaged.

Segmented isolation test

Independently verify the heating section and condensing section: After excluding faults in the cooling water pump, cooling tower, and vacuum pump, the problem still exists and is locked as an issue with the heat exchange efficiency of the main body.

5、 Summary of Simple Judgment

If any two conditions are met, it can be determined that the heat transfer efficiency has decreased:

Decreased production capacity and reduced water output;

Energy consumption increases under the same parameters;

The temperature difference between cold and hot flows has significantly decreased;

Frequent boiling, overflow, and unstable vacuum;

Visible scaling and fouling on the inner wall of the heat exchanger.