Refrigeration in CorrelationThere is an indisputable relationship between the growing advantages provided by the HVAC&R industry and the technology developed for the creation of innovative solutions that respond to the needs of the market.
We have already provided the HVAC&R community with invaluable information about the operation and fault detection of the current air conditioner. These concepts often go unnoticed by the technical community, however gradually we realize that the area of HVAC & R has become a multidisciplinary activity, therefore, the reader is recommended to be aware of these changes, which will undoubtedly be an important tool to know the trends of the market.
We cannot close our eyes to the constant evolution of technology. Thermodynamics and Electronics, increasingly have stronger links focusing their efforts to achieve efficient, functional and robust products. Electronics is a discipline that is often neglected during the training of technical personnel.
Earlier this year, a call will be launched for all those who want to participate in free training programs.
Trends in new systems
Every development of a new technology is based on a need. In our case, the most pressing and one that has taken on greater importance is that related to energy saving.
Thanks to this need, the continuous evolution of the components of our systems has become evident and increasingly notorious. To cite an example, in past decades, the electric motors of most air conditioners were not only noisy, but also large and heavy, situations that resulted in large electrical consumption, since they had to move blades or very heavy metal turbines that required capacitors of the order of 5 to 10 uF as the case may be.
Currently, the entire ventilation system was redesigned and there are fractional amperage motors, capable of displacing a large volume of air.
The control systems of our air conditioning equipment carry a close interaction with the user. Proof of this is the performance monitoring system. At the moment of a failure, the equipment automatically issues an alert and gives notice to the user of a malfunction, in addition, the SLIT FIN fin engraving technology and the ribbed copper pipe used in the design of coils allow a temperature exchange that takes place almost instantaneously. This also makes us participate in how the limit of high efficiency has gone from 13 or 14 SEER, to 21 SEER being this, cataloged as "ultra high efficiency", something that years ago we could not conceive and today we are experiencing.
To achieve this breakthrough, it was necessary to redesign the operation of the compressor, which for these purposes turns out to be the element of greatest consumption in our system. The most popular technologies are known as Digital Scroll and DC Inverter, however although they are still very little known, we should learn because of the potential they possess. The principle of operation will be explained below.
Digital Scroll Technology
They are two intertwined spirals with very small separations that never touch each other. While the bottom spiral is fixed to the compressor chassis, the spiral placed at the top is connected to the engine arrow via an eccentric cam.
This technology has a very special variant in its constitution. The most prominent difference compared to a normal Scroll compressor is that the upper spiral has the ability to separate vertically from the fixed spiral. This movement is carried out by mechanical means thanks to a solenoid valve with feedback to the suction port.
When the valve opens, the high pressure exerted on the upper spiral is directed towards the suction port releasing the upper spiral (Figure 1). It is at that very moment that the refrigerant pressure tends to level out because the compression chamber is partially open. When the valve is closed again, the high pressure exerts force on the upper spiral closing it between the spirals and consequently, the difference in pressures between the suction and discharge increases again.
Figure 1. A solenoid valve acts to regulate the performance of the system.
Indirectly, the displacement capacity of the compressor and therefore the cooling capacity of the equipment is being modified. The solenoid valve needs to be energized to control the flow of coolant from the system. To perform this action, a PAM (Pulse Width Modulation) signal will determine the operating time of the solenoid valve.
One of the most outstanding advantages of using this technology is the simplicity in the constitution of the control system, where all the weight of the operation is in the activation of a coil, which means a single additional line of ON/OFF control.
Figure 2. The activation time of the solenoid will determine the total consumption of the system.
The electrical consumption of this system will be determined directly by the time in which the spirals are closed. This means that when the compression chamber is closed, the engine will experience maximum effort and therefore more consumption power (Figure 2).
On the other hand, since the compression chamber of the engine is open, it will be operating practically without load. This is reflected in 10% of the total consumption of its nominal power.
DC Inverter Technology
It uses in the compressor a direct current motor with high magnetic permeability, which produces a strong magnetic field without the need to apply much energy in its working windings significantly reducing energy consumption.
By having a direct current motor in the compressor, it becomes necessary to convert the voltage of the line 220 VAC to direct current voltage, that is, to use a current inverter.
Figure 3. RPM determines the cooling capacity of the compressor.
The name DC Inverter is due to the use of a voltage inverter in its constitution. This is a very complex electronic control module used to level the voltage and current needed for the operation of such a compressor. By having a direct current motor in the compressor in question, there is the possibility of controlling the rotational speed of the rotor very accurately and consequently changing the cooling capacity of the rotor (Figure 3).
Figure 4. The compressor has minimal energy consumption to maintain the temperature in the room.
This particular characteristic causes that as the room reaches the desired temperature, the control system determines that the need to use 100% of the performance of the equipment does not decrease and it is at this time that the speed of the compressor decreases providing only the BTU / hr necessary to maintain the temperature in the room and consequently decreases the energy consumption of the system (figure 4).
Digital Scroll and DC Inverter Technologies are two different technologies and therefore maintain many variations between one and the other. However, there is also a wide range of benefits that they have when compared to conventional air conditioning equipment, as well as the type of analysis necessary at the time when it comes to solving a failure that occurred within the system.
The incoming panorama demands a spill of very broad knowledge, so we invite anyone dedicated to this area to worry about obtaining knowledge and try to know current technologies.
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