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Column for Ch & K Magazine: Is a refrigeration compressor like a car engine?

It is often said that a refrigeration compressor works in a similar way to an internal combustion engine … just the opposite. So let’s compare how a refrigeration compressor resembles a typical car engine.

One of the basic parameters of an internal combustion engine is its displacement volume. So what is the volume of the compressors we use? The smallest transcritical Bitzer 2NSL-05K has a volumetric capacity of 1.33 m3 / h, which gives a displacement volume of only 0.02 liters. The largest currently commercially available compressor – the 6-cylinder Dorin has a displacement of 99.6 m3 / h and a displacement of 1.15 liters. So at the level of a small city car. I remember that this manufacturer sometimes referred to automotive inspiration. This compressor has a capacity of 100 hp.

However, we also have sports engines – high-speed and more working, trucks – low-rev. The difference is, among other things, the proportion of the width of the piston to its stroke. The smaller the stroke, the higher the RPM, but the lower the torque. From my observations, most modern transcritical CO2 compressors have a stroke nearly twice as small as the diameter.

Therefore, if you want to treat the compressor and the internal combustion engine analogously, you should say that the compressor is something like an engine in a sports motorcycle: somewhere between a scooter and a sports 600.

I wonder if this is what the producers are inspired by?

This type of comparison could be made further and further, but now I invite the reader to the completely substantive part of our R744 section.

 

Maurycy Szwajkajzer

for the Chłodnictwo i Klimatyzacja magazine

Column for Ch & K magazine: CO2 air conditioning

Refrigeration and air conditioning only for people from outside these industries are the same. In fact, the refrigerant circuit is identical, but the intended use, technical considerations, market size, power levels and business habits are as far apart as welding is from playing the piano.

Refrigeration works all year round. Air conditioning not anymore. This minor fact influences the profitability of energy saving solutions in a fundamental way. This is especially important for R744 systems, which operate in a subcritical – very, very economical and supercritical – moderately economical, above this value below an outside temperature of about 25 ° C. For obvious reasons, air conditioning requires coolness at high outdoor temperatures – those that require or are close to supercritical work. So what technically has to happen for CO2 chillers to be more widely used in air conditioning?

I present my opinion:

  1. Air conditioning in facilities such as shopping malls, office buildings, serving services, etc. must work all or a significant part of the year. Therefore, for the calculation of profitability, it is not allowed to take only time, with an external temperature above 20 ° C. A lot of computational programs still make this mistake.
  2. The use of hybrid adiabatic towers as gascoolers should be seriously considered. This ensures that the reference for the condensation temperature will be a wet thermometer, not a dry one.
  3. Ejectors that recover expansion energy and flooded systems not requiring superheat in the evaporators should be used.

This, of course, is only part of the puzzle required to popularize the R744 in air conditioning. Meanwhile, after such a short introduction, I invite you to read the notes in our section as well as the information and articles contained in this issue. It is worth knowing more.

 

Maurycy Szwajkajzer

for the Chłodnictwo & Klimatyzacja magazine