Experimental investigation of a cross-flow heat recovery unit in an air handling unit: energy performance, life cycle assessment, and carbon footprint analysis

Abstract

 Heat recovery units (HRUs) embedded in air handling units (AHUs) represent one of the most straightforward yet effective strategies for curtailing building energy consumption, which accounts for roughly 30-40% of global final energy use. Despite a well-established theoretical foundation, experimental studies spanning multiple operating modes-particularly when combined with life cycle and carbon footprint assessments-remain relatively scarce for cross-flow plate configurations. This paper reports laboratory experiments conducted on the educational Air Handling Unit (AHU) test cycle, which features a cross-flow plate HRU, under four distinct conditioning modes: (1) heating only, (2) humidification combined with heating, (3) cooling with dehumidification, and (4) cooling with dehumidification followed by reheating. Dry-bulb temperature and relative humidity were measured at seven stations along the air path, enabling full psychrometric energy balances following. Air velocity was varied over 1.1-3.6 m/s to assess its influence on HRU temperature effectiveness ( ), thermal output, and Coefficient of Performance (COP). Results show that  decreases from 0.792 to 0.671 as velocity increases in heating mode, while the fraction of total heating demand covered by heat recovery reaches 129% at the highest velocity tested. COP of cooling ranges from 2.52 to 3.37 in Mode 3 and rises to 3.21-5.04 in Mode 4. A simplified operational life cycle assessment (ISO 14040:2006; ISO 14044:2006) using Turkey’s national grid emission factor (0.452 kgCO₂eq/kWh) yields annual CO₂ savings of approximately 6,136 kgCO₂eq.

Keywords

• Cross-flow heat exchanger
• Air handling unit
• HRU effectiveness
• Psychrometric analysis
• COP
• LCA
• Carbon footprint

Bir Klima santralindeki çapraz akışlı ısı geri kazanım ünitesinin deneysel incelenmesi: enerji performansı, yaşam döngüsü değerlendirmesi ve karbon ayak izi analizi

Abstract

Hava işleme ünitelerine entegre Isı Geri Kazanım Üniteleri (IGKÜ), küresel nihai enerji tüketiminin %30-40'ını oluşturan bina enerji tüketimini düşürmenin en doğrudan ve etkin yöntemlerinden birini temsil etmektedir (IEA, 2024; Pérez-Lombard ve ark., 2008). Çapraz akışlı plakalı konfigürasyonlara yönelik, yaşam döngüsü değerlendirmesiyle bütünleşik çok modlu deneysel çalışmalar görece sınırlı kalmaktadır. Bu çalışmada, klima santrali deney düzeneğinde dört farklı koşullandırma modunda deneyler gerçekleştirilmiştir. ASHRAE (2017) ve EN 308:1997 standartları çerçevesinde gerçekleştirilen psikrometrik enerji dengelerinden elde edilen sonuçlar; εT değerinin hız artışıyla 0,792'den 0,671'e gerilediğini, en yüksek hızda toplam ısıtma yükünün %129'unun IGKÜ tarafından karşılandığını ortaya koymaktadır. Soğutma COP değerleri Mod 3'te 2,52-3,37, Mod 4'te 3,21-5,04 aralığında seyretmektedir. ISO 14040:2006 ve ISO 14044:2006 kapsamında yürütülen basitleştirilmiş yaşam döngüsü değerlendirmesi, yıllık yaklaşık 6.136 kgCO₂eş tasarruf sağlamaktadır.

Keywords

• Çapraz akışlı ısı değiştirici
• Klima Santrali
• IGKÜ etkinliği
• Psikrometrik analiz
• COP
• Yaşam döngüsü değerlendirmesi
• Karbon ayak izi

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