EXERGETIC ANALYSIS OF AIR CONDITIONING AT DIFFERENT OUTDOOR TEMPERATURES

ABSTRACT

The article examines the cooling agents that cause the depletion of the ozone layer and the alternatives to these cooling agents. Exergetic analysis was also performed. The study compared the refrigerants R22, R410A, 290 and R32 used in a split air conditioner with a capacity of 12000 Btu / s.

АННОТАЦИЯ

В статье рассматриваются хладагенты, вызывающие разрушение озонового слоя, и альтернативы этим хладагентам. Также был проведен эксергетический анализ. В исследовании сравнивались хладагенты R22, R410A, 290 и R32, используемые в сплит-кондиционере мощностью 12000 БТЕ/с.

Keywords: R22, R410A, 290, R32, exergetic analysis, refrigerant, alternative, Ozone, cooling efficiency, cooling coefficient.

Ключевые слова: R22, R410A, 290, R32, эксергетический анализ, хладагент, альтернатива, озон, эффективность охлаждения, коэффициент охлаждения.

Introduction

The production of artificial cooling, obtaining temperatures below ambient temperatures, is widely used in many areas of the economy in the implementation of various technological processes. Refrigeration technology is needed in many areas of human activity.

Life on Earth has been preserved for thousands of years because of its protective atmosphere. This layer is called ozone and protects the Earth from the sun’s harmful ultraviolet rays. If the protective layer is broken, the harmful part of the sun's ultraviolet rays will affect the Earth's surface, killing most living organisms possible. One of the industries that has a negative impact on ozone is artificial cooling. It is impossible to imagine our lives and activities today without artificial cold [1, p. 76].

Research methodology and results

R32 refrigerant is an alternative to R410A, which is currently used instead of R22 refrigerant. The reason can be seen in Table 3.1. The global heating potential (GWP) of R32 is much lower than that of R410A. So R32 is environmentally friendly.

Table 1 shows the characteristics of R32, R410A, R22 and R290. The physical properties of R410A and R32 are very close, so copper pipes of the same diameter are used in the operating mode of the split system. It should be noted that the same oil is used.

Table 1.

Comparison of some properties of refrigerants under study

The following is a study of a ozone-safe refrigerant R410A, R290 and R32 for a split air conditioner with a cooling capacity of 12000 Btu / s.

Today’s world is living and adapting to global warming. The fact that the average temperature of our winters increases every year, and the extreme heat of our summers requires additional experiments. Therefore, we graphically present the results of the study obtained when the ambient temperature is 30, 40, 50. In cooling mode, the air conditioning temperature is always higher than the outside temperature. That is, if the outside temperature is 30, the condensing temperature will be around 10 [2, p. 286].

Figure 1. Graph of correlation of cooling capacity of cooling agents R22, R410A, R290  and R32 to outdoor temperature

R290 is 1.27 times lower than R22. As can be seen, as the outside temperature increased, that is, in summer conditions, the results of all four cooling agents decreased. This is because as the outside temperature increases, the specific mass cooling efficiency (q₀) of the refrigerant decreases, which in turn affects the self-cooling efficiency (Q₀). Under these conditions, the R32 refrigerant performed better than other refrigerants, but it dropped by 38% compared to the initial result. This figure was 38% in R410A and showed the same negative result as R32.  However, these figures were 16% in R22 and 21% in R290, a positive result for them. [3, p. 23]

Figure 2. Relativity of outdoor temperature to exergy efficiency η_ex(%)

Figure 2 shows a graph of the change in the exergy efficiency of the refrigerant under study with a change in ambient temperature. In this graph, we can see that the exergy efficiencies of refrigerants decrease with a change (increase) in the ambient temperature. Refrigerants R290 and R22 have an exergy efficiency of 1.18 times at an outdoor temperature of 30°C. The refrigerants R410 and R32 do not differ significantly at an outdoor temperature of 30°C. The exergy efficiency reaches a high result at an ambient temperature of 50°C and all refrigerants differ slightly [4, p. 176].

Figure 3. Relativity of outdoor temperature to exergy loss

As the ambient temperature rises, the amount of exergy loss increases, and such losses give different results in the cold agents we study (Figure 3). For R410 and R410 refrigerants, the exergy loss is much less than for R32 refrigerant. the same temperature at an ambient temperature of 30 ° C. However, with an increase in the outdoor temperature by 44 ° C, the exergy loss of R410 refrigerant increases more than that of R32 refrigerant [5, p. 179].

Conclusion.

The results of the study of refrigerants R22, R410A, R290 and R32 at different outdoor  temperatures are as follows:

• The refrigerant R32 is 1.2 times higher than R410A, 1.5 times higher than R22, and 1.98 times higher than R290;
• The exergy efficiency of R410 and R32 is almost indistinguishable at an ambient temperature of 32-35℃, but when the ambient temperature exceeds 37℃ to 49℃, the exergy efficiency of R22 refrigerant is the highest.

Reference:

1. Azizov D.H., Norkhujaev A.S., Research of split air conditioner in environmentally friendly cooling agent // Scientific and technical journal of Chemistry and Chemical Technology. №2, 2017 - pages 75-78
2. Azizov D.H., Norkhojayev A.S., Research of a split air conditioner on environmentally friendly refrigerants // Collection of scientific papers international scientific and technical on-line conference. - Tashkent. TashSTU, 2020. pp. 285-288
3. Azizov D.H., Norkhujaev A.S., Perspektivy perevoda split-konditsionerov na GFU ‑ 410A // Molodoy uchonyy. International scientific journal. № 1 (135), January 2017. C. 20-24
4. Koraboev A.S., Norkhujaev A.S., Maxmudov O.O., Study of compressors with split conditioners with low pressure // Texnika i teknologii mashinostroeniya. Materials of the VII  International scientific-technical conference. Omsk, May 21-23, 2018 S. 174-177
5. Nurmatov T.B., Norkhujaev A.S., Khasanov B.B., Testing of split-conditioners with low pressure with the use of refrigerants R22 and R410A // Texnika i teknologii mashinostroeniya. Materials of the VII International scientific-technical conference. Omsk, May 21-23, 2018 C. 178-180