ACR Journal

October | November 2020 REFRIGERATION 28 Volume 6 No.5 An electronic expansion valve is best defined as a valve that combines the strength of mechanics with the intelligence of electronics. I was recently embarrassed to find myself having to discuss this subject with a major international player, convinced that the transition from mechanical to electronic thermostatic valves was by now an obsolete topic. I therefore had to search around for some documents that we had published about 10 years ago. The role of the expansion valve - the antagonist of the compressor in traditional systems - is to guarantee the correct flow of refrigerant to the evaporator, so as to obtain the best heat exchange performance with the highest possible eciency. Among other things, the valve also has the function of protecting the system against the return of liquid. Using an electronic valve instead of a mechanical valve brings numerous advantages: 1. Much more stable and precise superheat control (i.e. measurement of the complete vaporisation of the liquid in the evaporator) as a result of the intelligent The electronic expansion Andrea Dalan, CAREL Valves Drivers & Flow Control Platform Manager, explains the advantages of electronic valves. control system comprising probes, the controller and its algorithms. 2. Wide range of control, from 0 to 100% of flow-rate 3. Compatibility with a wide range of refrigerants without the need to select a specific electronic valve based on the refrigerant used. The type of refrigerant is selected by setting a parameter on the controller. 4. Unlike thermostatic valves, electronic valves do not require periodic calibration. 5. Fast response to changes in the surrounding conditions (on, oŒ, ...). 6. Hermetic seal ensured by the use of high-performance gaskets and motors. Thermostatic valves, on the other hand, need to be used in combination with a solenoid valve in order to prevent refrigerant from migrating to the compressor. The result is: 1. Energy savings for the end user. The lower condensing pressure means less work for the compressor. Comparative studies between electronic and thermostatic valves carried out together with customers and universities have shown savings in annual energy consumption of 15 to 35% when using electronic valves. 2. Lower maintenance costs. Better compressor operating conditions (lower pressures, lower discharge temperatures), no liquid return and therefore less deterioration of the mechanical parts. No maintenance needed for valve calibration. 3. Less components for manufacturers to handle as the same solution covers a wide range of refrigerants. All with a view to safeguarding our planet, ensuring the most ecient solutions to achieve what we need (heating or cooling). The advent of variable-speed compressors has made the use of electronic valves even more essential, by virtue of their ability to respond quickly to changes in operating conditions and the wide control range they allow. One interesting example that helps understand the direction we need to take comes from the automotive sector. The development of electric cars has led to the need to maximise the performance of all auxiliary vehicle systems. As the energy stored in the batteries is precious and needs to be used primarily to move the car, high eciency of the passenger compartment air conditioning and battery cooling systems make electronic expansion valves a must.

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