Backwater Temperature Regulation Method for Hot Water Heating System

As one of the primary regulation methods of hot water heating system, the return water temperature regulation method of hot water heating system is suitable for the pipeline network without regulating valves. When the balance valve is not installed at the user's entrance of the pipe network, or when the pressure gauges at both ends of the ordinary control valve are not complete at the entrance, or even when the pipe network entrance only has the ordinary valve, the return water temperature regulation method can be used to adjust.
Chinese Name: Backwater Temperature Regulation Method for Hot Water Heating System
Foreign Name: the return water temperature regulation of hot water heating system
Purpose: To adjust the operating flow of thermal users to the ideal flow rate.
Field: Heating Regulation
Characteristic: Suitable for pipeline network without regulating valve
Regulation theory
When the heating system runs in a stable state, if the loss along the pipeline network is not considered, the heat supplied by the heat medium to the indoor heat dissipation equipment should be equal to the heat dissipation of the heat dissipation equipment and the heat load of the heating user. The heat supplied by the pipe network to the indoor heat dissipation equipment is equal to the product of its flow rate, the temperature difference between supply and return water and the specific heat of hot water. When the actual flow rate is larger than the design flow rate, the temperature difference between supply and return water decreases and the return water temperature is higher than the specified value. When the actual flow rate is less than the design flow rate, the temperature difference between supply and return water increases, and the temperature of return water is lower than the stable value.
Therefore, as long as the return water temperature of each user is equal (when the water supply temperature is equal) or the temperature difference between the supply and return water is equal (the insulation effect of the pipeline is poor, the water supply temperature is slightly different), the heat users can get the heat corresponding to the heat load and achieve the goal of uniform regulation.
This method is the simplest, primitive and time-consuming one. It can be used in any heating system. It does not require the type of valves, pressure gauges and thermometers. It only needs an infrared thermometer or a digital surface thermometer.
(1) Determination of regulating temperature
When the heat supply of the heat source is greater than or equal to the user's heat load and the flow rate of the circulating pump is greater than the design flow rate, considering the energy-saving operation of the circulating pump, the user's return water temperature should be adjusted to the return water temperature corresponding to the temperature regulation curve. When the heat supply of heat source is greater than or equal to the user's heat load and the flow of circulating pump is less than the designed flow rate, the average temperature of supply and return water should be adjusted to the average temperature of supply and return water corresponding to the temperature regulation curve. When the heat supply of heat source is less than the user's heat load, the user's return water temperature should be adjusted to a little lower than the total return water temperature.
(2) Regulation process
Because of the large thermal inertia of the heating system, the temperature changes obviously after the belt. After adjusting the flow rate of the system, the temperature of the system can not reflect the change of the flow rate in time, so the adjustment of the valve opening has a certain degree of experience. The measurement temperature should be adjusted by all users after a period of time. The interval time is related to the size of the system. When the total backwater temperature is stable at a certain value, the next round of adjustment can be made.
Firstly, the backwater temperature of each user is recorded and compared with the total backwater temperature. The higher the temperature, the smaller the valve closes. Under the same backwater temperature difference between users, the bigger the pipe diameter, the more closed it is. In the first round of adjustment, the proximal end user valve should close excessively. Record the number of valve closing cycles for each user.
After the first round of adjustment is completed, the user's return water temperature is recorded after the total return water temperature is stable and unchanged, and compared with that before adjustment, and then compared with the total return water temperature for the second round of adjustment. The interval between the first and second rounds should be more than twice the time required for the furthest user to return water to the heat source after the first adjustment. Estimates are made according to the flow rate of the network and the longest user pipe length, and so on.


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