Abstract:Highlights• 1/2" smooth tube and 3/8" grooved tube types evaporators are designed for industrial refrigerators.• Theoretical and experimental analysis and comparison of smooth and grooved tube evaporators.• The system COP value is 2.807, while it is calculated as 3.013 for the second system.• The grooved tube evaporator has better cooling performance compared to the smooth tube evaporator.
“…The energy equations condenser capacity (𝑄 ̇ , kW), evaporator capacity (𝑄 ̇ , kW), and the power of compressor (𝑊 ̇ , kW) of the vapor compression refrigeration cycle are given below, respectively [13]:…”
In recent years, the use of refrigerants, which increase the global warming potential by creating a greenhouse effect, has begun to be restricted in refrigeration systems. More environmentally friendly and more efficient synthetic mixtures and natural refrigerants are replacing refrigerants with high global warming potential. In this study, R404A refrigerant, which is frequently preferred in refrigeration systems, especially in residential split air conditioner applications, and has a high global warming potential, was discussed. Eight different refrigerants (R407H, R448A, R454A, R454C, R457A, R468A, R290, R1270) that could be alternatives to R404A refrigerant were examined and compared with R404A. Energy, exergy, and environmental analyzes were performed under the same conditions according to -10 ℃, -5 ℃, and 0 ℃ evaporating temperatures. Among the refrigerants, R290 had the best value with a coefficient of performance of 4.11 and an exergy efficiency of 40.04%. The values of R1270 refrigerant were also almost the same as R290. Even if R468A shows the lowest performance, it can be preferred over R404A because its global warming potential is lower than R404A.
“…The energy equations condenser capacity (𝑄 ̇ , kW), evaporator capacity (𝑄 ̇ , kW), and the power of compressor (𝑊 ̇ , kW) of the vapor compression refrigeration cycle are given below, respectively [13]:…”
In recent years, the use of refrigerants, which increase the global warming potential by creating a greenhouse effect, has begun to be restricted in refrigeration systems. More environmentally friendly and more efficient synthetic mixtures and natural refrigerants are replacing refrigerants with high global warming potential. In this study, R404A refrigerant, which is frequently preferred in refrigeration systems, especially in residential split air conditioner applications, and has a high global warming potential, was discussed. Eight different refrigerants (R407H, R448A, R454A, R454C, R457A, R468A, R290, R1270) that could be alternatives to R404A refrigerant were examined and compared with R404A. Energy, exergy, and environmental analyzes were performed under the same conditions according to -10 ℃, -5 ℃, and 0 ℃ evaporating temperatures. Among the refrigerants, R290 had the best value with a coefficient of performance of 4.11 and an exergy efficiency of 40.04%. The values of R1270 refrigerant were also almost the same as R290. Even if R468A shows the lowest performance, it can be preferred over R404A because its global warming potential is lower than R404A.
“…𝑊 ̇𝑐 𝜂 𝑖𝑠,𝑐 + 𝑚̇4 ℎ 4 = 𝑚̇5 ℎ 5 (11) Buradan, 𝑊 ̇𝑐 kompresör kapasitesi aşağıdaki gibi elde edilmiştir;…”
Section: Isı Pompası Sisteminin Termodinamik Analiziunclassified
“…Hesaplamalar, ısıtma ihtiyacının olduğu kasım, aralık, ocak, şubat ve mart ayları için yapılmıştır. Sistem tasarlanırken evaporatör dış ortam sıcaklık farkı ∆T = 7 °C olarak alınmıştır [11]. Pompa izentropik verimi (ηis,p) %87.5…”
Dünyada ve ülkemizde insan nüfusu sürekli olarak artış eğilimi göstermektedir. Bu artışın doğal bir sonucu olarak tüketim artmaktadır. Artan tüketimlerin başında ise enerji ihtiyacı gelmektedir. Yeryüzünde sınırlı ve her geçen gün azalmakta olan enerji kaynaklarının birçoğu ise gezegene kullanımlarıyla beraber zararlar vermektedirler. Tercih edilen bu çevreci ve sürdürülebilir enerji kaynakları sayesinde ise çevre kirliliğinde azalma ve küresel ısınmada yavaşlama sağlanmaktadır. Bu çevreci kaynakların başında ise güneş enerjisi gelmektedir. Bu çalışmada PVT’li ve çevreci CO2 akışkanlı hibrit bir ısı pompası ile tasarlanan bir evin ısınma ve elektrik enerjisi ihtiyacının karşılanması için bir sistem tasarımı ile teorik incelemesi yapılmıştır. İlk aşamada, çalışmada tasarlanan evin ısınma enerjisi ihtiyacı belirlenmiştir. Daha sonrasında ise PVT’nin modellenmesi ile termal ve elektriksel analizleri yapılmıştır. Son olarak da ısı pompasının termodinamik analizi gerçekleştirilmiştir. Dizayn edilen sistem özelinde yapılan bu analiz ve belirlemeler sonucunda ise gerek CO2 akışkanı gerekse farklı akışkanlar ile sistem karşılaştırmak suretiyle birçok parametrede bulgular elde edilmiştir. Elde edilen bulgular grafik ve çizelge formatında karşılaştırmalı şekilde makalede verilmiştir.
Cascade refrigeration systems are preferred in applications where low temperature cooling is required, such as in some special industrial and laboratory applications. Since, in these systems, the energy consumed by the compressors is less and the compressor outlet temperature is lower. Due to environmental problems, the use of natural refrigerants in cascade refrigeration systems has become to be of great importance. In this study, two cascade systems consisting of R744/R290 (System 1) and R1270/R290 (System 2) natural refrigerant pairs were designed and thermodynamically examined. In the analyzes performed according to different evaporator temperatures, the highest COP value was 3.66 at -20℃ evaporating temperature was obtained in the cascade system consisting of the R1270/R290 refrigerant pair. Moreover, it was considered that there was a 17.95% enhancement in exergy efficiency with the use of R1270 refrigerant in the low temperature cycle. By the rise in the evaporator temperature, energy consumption decreases and as a result, the amount of carbon dioxide emissions reduced was attained.
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