Below we present the operation of an air conditioning system with three pipes to achieve flexibility in heating and cooling.
by Chigo HVAC
Over the years of presence in the air conditioning market, we have witnessed the rapid increase in special requirements. An in-depth analysis of this phenomenon suggests that it occurred hand in hand with economic growth. Some large, modern buildings may need cooling in winter due to good sealing capacity and powerful heat dissipation. Similarly, during periods of changing seasons, the elderly or hospital patients need heating while healthy people need air conditioning.
The three-pipe air conditioning system, created to cool and heat at the same time, makes it possible to make the most of energy. It can absorb heat from spaces that require cooling, rather than from the environment, to heat other spaces, saving 50% of energy. Currently, many European countries have accepted this system and even governments are trying to promote its use among people.
Next, we will analyze, through a series of very illustrative graphs, the principle of air conditioning investigated by Chigo. As with the conventional system, the three-pipe system is also mounted with an indoor unit and an outdoor unit, but there are some changes to the pipes.
1. Flow circuit in an indoor unit.
This is the cooling circuit of the indoor unit. On the left side of the image you can see the conventional circuit of two pipes and on the right, the circuit of three pipes. As noted, on the right side there is a high-pressure pipe attached, compared to the left side. Thus, cooling arises when the pipe is filled with low-pressure gas and heating when the pipe is filled with high-pressure gas.
In this image you can see four indoor units of this type of system, two of them operating in cooling mode and the other two in heating mode. Heating occurs when high-pressure gas pipes open, and cooling when low-pressure gas pipes are opened. Additionally, solenoid valves are installed on each branch of the high-pressure and low-pressure gas pipes. Therefore, it is only possible to design the system for simultaneous heating and cooling when low-pressure gas, high-pressure gas and coolant are available.
2. Special design for outdoor unit
In any three-pipe air conditioning system, the indoor unit and flow circuit is the same. Therefore, the fundamental aspect, which must be carefully designed, verified and improved, is the way to obtain the three states of the refrigerant. Next, I will share with readers two design principles of this special outdoor unit.
General design: "General" involves making any improvements on the basis of two-pipe air conditioning to get new functions.
The principle of this method is the addition of a new pipe that can connect the compressor outlet or inlet using a reversing valve. In this principle, it is convenient and economical to use a traditional outdoor unit with which you will achieve a better quality quickly. We find that the two gas pipes are exchanged with each other when mode changes work. In fact, when the liquid stabilizes, the system can function normally no matter what gas pipe it is, it is enough to change the control system to adjust the solenoid valves.
Design principle of the VRF (variable refrigerant volume) system of chigo's three pipes:
This system is simple, but more efficient, if we analyze it carefully. With the stabilization of gas pipes, changing the entry point of the condenser between the inlet and outlet of the compressor, the mode of operation can be changed flexibly.
Due to its novelty, and not having the support of traditional devices, it is necessary to develop a large number of auxiliary devices. For example, the solenoid valve, which is observed in the high-pressure gas pipe, is used to get rid of the influence caused by the extensive pipe filled with high-pressure air.
Conclusion
The three-pipe air conditioning system features conventional heating and cooling modes. It also has simultaneous cooling and heating functions. In mixed operating mode, heat recovery can save energy and solve the heat island effect, an advantage that more and more people recognize.
