Adverse effects of hydraulic imbalance in air conditioning

1. Concepts of hydraulic imbalance and hydraulic balance

1. 1 water imbalance: the heating pipe network of HVAC system is a complex interconnected pipe system composed of many series-parallel pipes and various heat users. In the course of operation, due to various reasons, the network traffic distribution often does not meet the user's design requirements, and the traffic between users needs to be redistributed. In the hot water heating system, the inconsistency between the actual flow rate of each heat user and the required flow rate is called the hydraulic imbalance of heat users. The degree of hydraulic imbalance can be measured by the ratio of actual flow to designed flow, which is hydraulic imbalance. X = QS/QJ(QS: actual traffic of users, QJ: traffic required by users' design)

1.2 hydraulic balance: hydraulic balance is an adjustment method aiming at the problem of hydraulic imbalance, aiming at eliminating hydraulic imbalance and realizing energy saving and consumption reduction. Because hydraulic imbalance can be divided into static imbalance and dynamic imbalance. Static imbalance is due to the small resistance of some loops, and the actual flow of the loop will exceed the design flow, but because the total flow is certain, other parts will not reach the set flow, and there will be uneven cold and heat; In the dynamic system, when the water quantity of some loops changes, the pressure distribution of the system will be uneven, which will interfere with other loops and cause undue changes in other loops. Hydraulic balance refers to the ability of each heat user in the pipe network to keep their own flow unchanged when the flow of other heat users changes, which is usually expressed by the hydraulic stability coefficient r of heat users. R = 1/XMAX = QJ/QMAX(QJ: user design demand flow, QMAX: maximum flow of users).

2. Classification of hydraulic imbalance and hydraulic balance

As far as the current specific classification is concerned, the hydraulic imbalance and hydraulic balance of HVAC heating systems can be divided into the following categories:

2. 1 static hydraulic imbalance and static hydraulic balance

There are problems in the design, construction, material and equipment selection of heating system, which leads to the inconsistency between the actual pipeline characteristic resistance ratio and the designed pipeline characteristic resistance ratio, and then leads to the inconsistency between the actual flow and the designed flow, which is called static hydraulic imbalance. However, if the static hydraulic balance equipment is designed in the heating pipeline, and the characteristic resistance ratio of the whole heating system is adjusted to keep it consistent with the design value, and the design requirements can be met in each terminal equipment, and the flow rate can also meet the design requirements, this is static hydraulic balance.

2.2 Dynamic hydraulic imbalance and dynamic hydraulic balance

When the water flow changes due to the change of valve opening of users, the flow of other users also changes, deviating from the design requirements, resulting in hydraulic imbalance, which is called dynamic hydraulic imbalance. Dynamic hydraulic imbalance is a dynamic change, not inherent in the system itself, but produced in the process of system operation. If dynamic hydraulic imbalance occurs, dynamic hydraulic balance equipment (flow regulator or differential pressure regulator) can be installed in the pipeline system. When the valve opening of other users changes, their own flow will not change with the shielding effect of dynamic hydraulic balance equipment, and the flow of terminal equipment will not interfere with each other, so the actual flow of each user tends to be consistent with the design flow. At this time, the system realizes dynamic hydraulic balance.

3. Hydraulic balance analysis of constant flow water system

Constant flow hydraulic balance system is a common hydraulic system in HVAC design, and the flow of each part of the system remains basically unchanged during operation. Commonly used mainly in the following three forms.