Generally speaking, the heat dissipation of the radiator mainly depends on the average surface temperature of the radiator. In the design state, the selection of the heat transfer area of the radiator is calculated based on the average temperature of the design surface of each layer of the radiator under the design conditions. However, in actual operation, due to uneven flow distribution, the change ratio of the average surface temperature of each layer of radiator will be different from the design conditions. When the actual flow of the riser is less than the design flow (ie, the relative flow is less than 1.0), the temperature difference between the supply and return water of the riser is greater than the design temperature difference. At this time, the average surface temperature of the upper radiator is higher than the average surface temperature of the lower radiator. It is more conducive to heat dissipation, so the phenomenon of upper heating and lower cooling occurs; when the relative flow is greater than 1.0, the situation is the opposite.
The point of vertical imbalance in a single-pipe system is that the larger the flow, the higher the room temperature at the end; the smaller the flow, the lower the room temperature at the end. According to this heat, for a single-pipe system, each temperature control valve should follow the following principles installation:
(1) For a single-pipe downstream indoor system, a temperature control valve should be installed on the radiator in the last room of the indoor system;
(2) For single-pipe indoor systems with spanning pipes, a temperature control valve should be installed on the inlet water supply pipe or return pipe of the indoor system, and the remote temperature sensor of the temperature control valve should be placed in the end room of the indoor system ；
(3) For the upper split single pipe downstream system of the old building, the temperature control valve of each riser should be installed on the radiator of the bottom room. At this time, the heat supply should be measured by a heat distributor. It should be pointed out that the advantage of using this temperature control valve is that it not only improves the regulation performance of the heating system, but also reduces the initial investment of the project; its disadvantage is that the room temperature of each room is the same standard and cannot be adjusted as desired. .
Dual-pipe indoor system with a temperature control valve installed at the indoor entrance. The vertical imbalance of the double pipe system is caused by the change of the system flow caused by the change of the pressure head of the natural circulation. In this system, the ideal solution is to install a temperature control valve on each radiator. Some real estate developers are unwilling to increase investment and cancel all temperature control valves. Although there will be no serious imbalance in the indoor system, it will inevitably lead to vertical imbalance between the various floors in the building. In engineering practice, this has also been proved. In order to reduce the cost without affecting the adjustment function of the heating system, in the double-pipe indoor system, a temperature control valve is installed at the indoor entrance, and the remote temperature sensor can be placed in any room. This scheme, although the room temperature adjustment in each room lacks flexibility, but it improves the uneven heating and cooling between the floors in the building, which is more in line with the current economic situation.
