Causes of uneven cooling and heating
The root cause of uneven cooling and heating is hydraulic imbalance. This paper analyzes the causes of uneven cooling and heating of hot users from two aspects: vertical imbalance and horizontal imbalance.
Causes of vertical dislocation
The reasons for vertical misalignment of single pipe system and double pipe system are different. The vertical misalignment of a single tube system is caused by the difference between the heat transfer coefficient k of each layer of radiator and the average calculated temperature difference of each layer. The vertical misalignment of a double tube system is caused by the different circulating pressures passing through each layer of radiator. The consequence of vertical imbalance is the uneven cooling and heating between the upper and lower floors, and the causes of vertical imbalance can be summarized as follows: (1) There is no reasonable vertical zoning in high-rise buildings, resulting in obvious differences in the circulating pressure between the upper and lower radiators. (2) Heat dissipation of main heating pipe and branch pipe is ignored in thermal calculation. (3) Due to the limitation of pipe system specifications, it is impossible to fully realize the hydraulic balance between the riser and the floor of the heating system in the design. (4) When designing and selecting the radiator area, due to the limitation of the radiator specification, the design requirements cannot be fully met. (5) The operating water temperature and flow deviate from the design conditions.
2. Causes of horizontal imbalance
Horizontal imbalance is common in hot water central heating system, which is the main form of hydraulic imbalance. It is mainly caused by the following factors:. (2) The heating area is expanded, and the circulation capacity of some pipe sections of the heating pipe network is insufficient. The pipe network transformation is not carried out in time, resulting in horizontal imbalance. (3) Improper selection of circulating water pump, too large or too small flow and pressure head will make the working point deviate from the design state, resulting in horizontal imbalance. (4) The increase or decrease of users in the system and the change of users' heat consumption require the redistribution of network traffic, which leads to the level imbalance. (5) When the construction conditions are limited, the actual situation of pipeline construction may be very different from the design. In actual operation, it will deviate from the designed balance state, resulting in hydraulic imbalance.
2. Causes of serious water loss of secondary pipe network
There are four main reasons for serious water loss in the secondary pipe network of hot water central heating system. ① Normal leakage of secondary pipe network. In the hot water central heating system, the leakage and blowdown of valves, compensators, vent valves, drain valves and other accessories of the secondary pipe network will cause a small amount of water loss. (2) The secondary pipe network has been used for a long time and has not been effectively maintained, resulting in serious aging of the pipe network, massive scaling and serious internal corrosion, frequent leakage points, and water loss. (3) Sudden accident causes water loss. The pipeline, valve, flexible connection, tee, elbow and other equipment in the secondary pipe network are suddenly damaged by external force or internal stress of the system, resulting in water loss. ④ The user discharges water without permission. Some users who are not hot use drainage to increase flow and indoor temperature, and some users use hot water in the secondary pipe network to wash clothes, which will cause water loss in the secondary pipe network. Among them, the last three reasons will cause abnormal water loss in the secondary pipe network, which is the main reason for serious water loss in the secondary pipe network, and effective measures should be taken to solve it.