The effects of injection timing on NOx emissions of a low heat rejection indirect diesel injection engine

Higher NO, is one of the major problems to be overcomed in a low heat rejection (LHR) diesel engine as insulation leads to an increase in combustion temperature about 200-250 degrees C compared to an identical standard (STD) diesel engine. High combustion temperatures alter optimum injection timing of a LHR engine. With the proper adjustment of the injection timing, it is possible to partially offset the adverse effect of insulation on heat release rate and hence to obtain improved performance and lower NOx. However, the injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO., emission point of view. In this study, optimum injection timing was found with 4 crank angle (34 degrees CA) retarded before top dead centre (BTDC) in LHR diesel engine in comparison to that of STD diesel engine (380 CA BTDC). When the LHR engine was operated with the injection timing of the 38 crank angle, which is the optimum value of the STD engine, it was shown that NOx emission increased about 15%. However, when the injection timing was retarded to 34 degrees CA in the LHR case, it was observed a decrease on the NOx emissions with about 40% and the brake specific fuel consumption (BSFC) with about 6% compared to that of the STD case. Thus, by retarding the injection timing, an additional 1.5% saving in fuel consumption was obtained. (c) 2005 Elsevier Ltd. All rights reserved

The Thermodynamic Analysis of the Refrigerants Alternative to R22 in the Vapor Compression Refrigeration System

In this study, the performances of the R417A, R438A, R422A and R422D refrigerants which are alternative to the commonly used and ozone layer-friendly R22 refrigerant are examined according to the first and second law of thermodynamics. Chemours Refrigerant Expert 1.0 and Genetron Properties 1.4 were used for the design of the vapor compression cycle. While the condensing temperature was kept constant during the analyses, the evaporation temperatures were determined according to the EUROVENT conditions (0 degrees C, -8 degrees C, -25 degrees C, -31 degrees C). The parameters calculated according to different evaporation temperatures are the required compressor power, performance coefficient (COP), and the required refrigerant mass flow rate. The results showed that the COP values of the R438A and R417A refrigerants were very close to that of R22. The COP values were 5%, 6%, 15% and 10% lower in R438A, in R471A, in R422A, and in R422D, respectively compared to the R22 refrigerant. The COP values were calculated as 13% for R422D and 17% for R422A. The highest exergy efficiency of the analyzed systems was calculated as 31.74% for R438A, 31% for R417A, 27.46% for R422A, and 29.24% for R422D at -25 degrees C evaporation temperature. The results of our study revealed that among the R417A, R438A, R422A and R422D refrigerants developed as an alternative to R22 refrigerant, the R438A refrigerant had comparatively higher COP values. Also, when the condenser and compressor loads were examined, it was found that the R438A, R417A, R422D and R422A refrigerants yielded the best results, respectively. Among the four alternative refrigerants examined, R438A and R417A were found to be better alternatives to R22 in terms of COP values, exergy efficiency, and exergy destruction.WOS:00058190120002

Buhar sıkıştırmalı soğutma sisteminde R22 alternatifi soğutucu akışkanların termodinamik analizi

Bu çalışmada, soğutma sistemlerinde yaygın olarak kullanılan R22 soğutucu akışkanına alternatif ve ozon tabakasına dost R417A,R438A, R422A ve R422D soğutucu akışkanlarının performansları termodinamiğin birinci ve ikinci yasasına göre incelenmiştir.Buhar sıkıştırmalı çevrimin tasarımı için Chemours Refrigerant Expert 1.0 programı kullanılmıştır. Yapılan analizlerde yoğuşmasıcaklığı sabit (50 ºC) tutulurken, evaporasyon sıcaklıkları EUROVENT şartlarına göre (0 °C, -8 °C, -25 °C, -31 °C) belirlenmiştir.Farklı evaporasyon sıcaklıklarına göre hesaplanan parametreler, gerekli kompresör gücü, performans katsayısı (COP) ve gereklisoğutucu akışkan kütle akış oranıdır. Sonuçlar, R438A ve R417A soğutucu akışkanlarının COP değerlerinin R22’ye çok yakınolduğunu göstermiştir. R22 soğutucu akışkanına göre COP değerleri, R438A’da %5, R471A’da %6, R422A’da %15 ve R422D’de%10 düşük olmuştur. Bu değerler R422D için %13 ve R422A için ise %17 olarak hesaplanmıştır. Analiz edilen sistemlere ait enyüksek ekserji verimi, -25 °C evaporasyon sıcaklığında R438A için %31.74, R417A için %31 ve R422A için %27.46 ve R422Diçin ise %29.24 olarak hesaplanmıştır. Çalışmanın sonunda, R22 soğutucu akışkanına alternatif olarak geliştirilen R417A, R438A,R422A ve R422D akışkanlarından, R438A akışkanının daha yüksek COP değerlerine sahip olduğu belirlenmiştir. Ayrıca kondenserve kompresör yükleri incelendiğinde en iyi sonuçları sırası ile R438A, R417A, R422D ve R422A akışkanlarının verdiğigörülmüştür. Genel olarak incelen 4 alternatif akışkandan R438A ve R417A’nın, COP, ekserji verimliliği, ekserji yıkımlarıaçısından R22 için daha iyi bir alternatif olacağı belirlenmiştir.In this study, the performances of the R417A, R438A, R422A and R422D refrigerants which are alternative to the commonly used and ozone layer-friendly R22 refrigerant are examined according to the first and second law of thermodynamics. Chemours Refrigerant Expert 1.0 and Genetron Properties 1.4 were used for the design of the vapor compression cycle. While the condensing temperature was kept constant during the analyses, the evaporation temperatures were determined according to the EUROVENT conditions (0 °C, -8 °C, -25 °C, -31 °C). The parameters calculated according to different evaporation temperatures are the required compressor power, performance coefficient (COP), and the required refrigerant mass flow rate. The results showed that the COP values of the R438A and R417A refrigerants were very close to that of R22. The COP values were 5%, 6%, 15% and 10% lower in R438A, in R471A, in R422A, and in R422D, respectively compared to the R22 refrigerant. The COP values were calculated as 13% for R422D and 17% for R422A. The highest exergy efficiency of the analyzed systems was calculated as 31.74% for R438A, 31% for R417A, 27.46% for R422A, and 29.24% for R422D at -25°C evaporation temperature. The results of our study revealed that among the R417A, R438A, R422A and R422D refrigerants developed as an alternative to R22 refrigerant, the R438A refrigerant had comparatively higher COP values. Also, when the condenser and compressor loads were examined, it was found that the R438A, R417A, R422D and R422A refrigerants yielded the best results, respectively. Among the four alternative refrigerants examined, R438A and R417A were found to be better alternatives to R22 in terms of COP values, exergy efficiency, and exergy destruction

Performance Assessment of a Refrigeration System Charged with Different Refrigerants Using Infrared Image Processing Techniques

This study aims to investigate the performance of R417A, R422A, R422D and R438A refrigerants as alternatives to R22, in a commercial type refrigeration system operating with R22 refrigerant. To this end, first of all, the cooling capacity and coefficient of performance (COP) values were calculated for all refrigerants used in the experimental setup. Then, two methods were proposed, Pearson's Correlation Similarity Analysis (PCSA) and surface temperature-based COP (COPST), to evaluate the success of each alternative refrigerants, and R22 with infrared image analysis, separately. The COP values obtained for the refrigerants with the mathematical method are R22 4.07, R438A 3.88, R417A 3.63, R422D 3.37, and R422A 3.18, respectively. Both the COP values and the PCSA values (R438A 0.9425, R417A 0.9343, R422D 0.9167 and R422A 0.9080) show the proximity between the R22 refrigerant and other refrigerants. Similarly, the COPST method revealed the values of R22 6.8865, R438A 5.9539, R417A 5.3273, R422D 4.9898 and R422A 4.3057, and the fact that it has the same order with the other two methods demonstrates its operability in the performance test application with the developed infrared image processing. The compatibility of the order in the experimental results obtained from the PCSA and COPST methods and the COP calculation method and has proved that thanks to infrared imaging, the remote performance analysis of the refrigeration system can be successfully performed.Scientific and Technological Research Council of Turkey (TuBTAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [218M936]This study was supported by The Scientific and Technological Research Council of Turkey (TuBTAK) with the project number 218M936.WOS:0006632463000012-s2.0-8510822867