Difference between one-way and different-way systems in fan coil installation

The same-pass system and different-pass system mentioned in the field of HVAC mainly refer to the water flow direction of the water supply and return mains in the water system pipeline. The direction of water supply and return is the same, which is called the same-pass system; If the direction of water supply and return is different, it is called a different distance system.

In practice, different distance systems are common.

However, the hydraulic transportation itself is inert, and likes the near and hates the far, which is similar to the way people like to take the path when walking. As a result, some problems have arisen: in large-scale projects, there are many branches in the water system, which will hinder the hydraulic transmission due to local head loss of equipment valves and pipe fittings, friction along the pipeline and other factors. The water pressure drop of terminal equipment is uneven, the hydraulic power is out of balance, and the water yield varies from drought to flood. The same-journey system can better solve these problems.

I. Same journey system

With the same program system, the water supply is supplied from near to far, and the backwater follows the water supply in one direction, and then converges from near to far and then returns centrally. Regardless of the distance, the length of the circulating pipeline of each terminal equipment is basically equal.

Classification:

In practical application, Tongcheng system has different manifestations according to different installation and use scenarios:

According to the position and direction of the pipeline, the same process system can be divided into horizontal pipe system and vertical pipe system.

According to the same route, the same route system can be divided into return pipe, water supply and supply, and return pipe.

No matter which form, the same process system follows a simple rule: first in, then out, and last in, first out. Generally, return pipe Tongcheng is often used in projects.

Advantages:

When the lengths of pipelines are basically equal and the resistance per unit length is almost the same, the resistance at each end is congenitally balanced, the water distribution is balanced, the hydraulic stability is good, and the adjustment is more convenient.

Disadvantages:

Due to the same installation, the pipeline length increases and the water resistance increases, thus the energy consumption of the pump increases; Compared with the simple and rough system, the initial investment is increased.

II. Different-range system

Different system, the water supply is supplied from near to far, and the backwater is returned from near to far. The near-end circulating pipeline is short, and the far-end circulating pipeline is long.

advantage

The length of pipelines passing through each parallel loop is not equal, the system is simple, the pipe consumption is small, and the construction difficulty is small.

Although in theory, different distance is not as reasonable as the same distance, the initial investment can be saved because of the short return main pipe of different distance system. Moreover, common frame laying can be adopted during construction (the slope direction of the main water supply and return pipes is consistent), which is easy to construct, so different paths are commonly used in general projects.

disadvantaged

The total length of the pipeline is unequal, the pipeline resistance is unbalanced, the hydraulic stability is poor, and the debugging is inconvenient.