Optimization of CO2 booster refrigeration cycle with flooded evaporators and parallel compressor by using the bees algorithm

Abstract

Energy supply is one of the most significant issues in modern society. So, energy saving becomes important in systems used frequently in daily life. Due to these energy saving concerns, there are numerous studies in literature to make supermarket refrigeration systems consume less energy. Among these studies, CO2 booster refrigeration system with flooded evaporators and parallel compressor (BFP) seems as an energysaving and nature-friendly choice. In this study, BFP was selected as the system of concern and the Bees Algorithm optimization was applied to get minimum power consumption (maximum COP). Gas cooler pressure (𝑃𝑔𝑐), intermediate pressure (𝑃𝑖𝑛𝑡), and medium temperature (MT) level evaporator outlet quality(𝑥14) were chosen as optimization parameters. According to the optimization results, the Bees Algorithm converged well, and these three parameters were found worthy to optimize as they brought significant energy saving in total (up to 8.7% in comparison with constant intermediate pressure and MT evaporator outlet quality). As a result of this analysis, the optimal 𝑃𝑔𝑐 values were found to be between 7600 kPa and 12000 kPa at ambient temperatures ranging from 28 to 46°C. The optimal 𝑃𝑖𝑛𝑡 values were found to be around 3500 kPa below ambient temperature of 14 °C and around 4500 kPa above this temperature. The optimal values for x14 ranged between 0.62 and 0.69. Additionally, annual energy consumption (AEC) and total equivalent emission (TEE) for 15 years were calculated for four different climate types. The highest AEC and TEE were obtained at tropical climate with 728.56 MWh and over 10000 tons, respectively. The lowest AEC and TEE were found at continental conditions as 380.01 MWh and almost 6000 tons of emission.

Keywords

• The bees algorithm
• Optimization
• Refrigeration
• Carbondioxide
• Booster
• Supermarket

CO2 akışkanlı yaş evaporatörlü paralel kompresörlü booster soğutma çevriminin güç tüketiminin arı algoritması ile optimizasyonu

Öz

Modern toplumdaki en önemli konulardan biri enerji tedariğidir. Bu nedenle günlük hayatta sıklıkla kullanılan sistemlerde enerji tasarrufu önem kazanmaktadır. Bu enerji tasarrufu hedeflerine yönelik süpermarket soğutma sistemlerinin daha az enerji tüketmesini amaçlayan çok sayıda çalışma literatürde bulunmaktadır. Bu çalışmalar arasında yaş evaporatörlü ve paralel kompresörlü CO2 booster soğutma çevrimi (BFP) enerji tasarruflu ve doğa dostu bir seçim olarak ön plana çıkmaktadır. Bu çalışmada, BFP çevriminde minimum güç tüketimini (maksimum COP) elde etmek için Arı Algoritması optimizasyonu uygulanmıştır. Optimizasyon parametreleri olarak gaz soğutucu basıncı (𝑃𝑔𝑐), ara basınç (𝑃𝑖𝑛𝑡) ve orta sıcaklık (MT) seviyesi evaporatörü çıkış kuruluk derecesi (𝑥14) seçilmiştir. Arı Algoritması optimizasyon sonuçlarına göre bu üç parametre, toplamda önemli ölçüde enerji tasarrufu sağlamaları sebebiyle (sabit ara basınç ve sabit MT evaporatör çıkış kuruluk derecesine kıyasla %8.7'ye kadar) optimize edilmeye değer bulunmuştur. Analiz sonucunda, optimum 𝑃𝑔𝑐 değerlerinin 28 °C ila 46 °C arasındaki çevre sıcaklıklarında 7600 kPa ile 12000 kPa arasında olduğu tespit edilmiştir. Optimum 𝑃𝑖𝑛𝑡 değerlerinin 14 °C çevre sıcaklığının altında yaklaşık 3500 kPa ve bu sıcaklığın üstünde yaklaşık 4500 kPa olduğu bulunmuştur. x14 için optimum değerler 0.62 ile 0.69 arasında elde edilmiştir. Ayrıca dört farklı iklim tipi için yıllık enerji tüketimi (AEC) ve 15 yıllık toplam eşdeğer emisyon (TEE) hesaplanmıştır. En yüksek AEC ve TEE sırasıyla 728.56 MWh ve 10000 tonun üzerinde değerlerle tropikal iklimde elde edilmiştir. En düşük ise 380.01 MWh AEC ve yaklaşık 6000 ton TEE ile karasal iklimde bulunmuştur.

Anahtar Kelimeler

• Arı algoritması
• Optimizasyon
• Soğutma
• Karbondioksit
• Booster
• Süpermarket

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