The influence of possible definitions of a reference environment to determine the exergy of air in buildings

Sakulpipatsin, P.; Kooi, Hedzer J. van der; Itard, Laure; Boelman, Elisa C.

doi:10.1504/ijex.2008.018111

Cited by 21 publications

(9 citation statements)

References 10 publications

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“…The results published by 8. Sakulpipatsin [8] may exceed these thermodynamic boundaries. When examined in the operational range, as done by Martinaitis and Streckienė [9], specific intervals highlight that efficiency values going below zero and becoming negative are an incorrect behaviour from the fundamental thermodynamics point of view.…”

Section: Exergy Efficiencymentioning

confidence: 99%

Exergy efficiency of a ventilation heat recovery exchanger at a variable reference temperature

Martinaitis¹,

Bielskus²,

Januševičius³

et al. 2017

mech

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Section: Exergy Efficiencymentioning

confidence: 99%

Exergy efficiency of a ventilation heat recovery exchanger at a variable reference temperature

Martinaitis¹,

Bielskus²,

Januševičius³

et al. 2017

mech

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“…Both combine exergy fluxes, the former in differences, the latter in ratios. As a matter of fact, numerous articles investigate the influence of the dead state temperature on the exergy efficiency of processes [8][9][10][11][12][13][14][15][16][17][18][19]: they study how a given process, often air conditioning, operates in various environmental conditions, especially with various values of the ambient temperature. As a main result, they show how exergy efficiency depends on the ambient temperature, an influence found to be strong especially for building applications [9,20].…”

Section: Introductionmentioning

confidence: 99%

“…The literature is somehow confusing about this point. In most of the articles mentioned above [8][9][10][11][12][13][14][15][16][17][18][19][20], the variable ambient temperature is taken as 'dead state' or 'reference' (a variable 'reference' then), but without any argument for supporting this option. Some authors propose to take an ad-hoc time-averaged ambient temperature as reference, either the hourly average [10,22,23], or the monthly average [10,22], raising then the paradox that 'the dead state varies with operating time' [23] but is in fact kept constant within a given time interval.…”

mentioning

confidence: 99%

Exergy Analysis and Process Optimization with Variable Environment Temperature

Pons

2019

Energies

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In its usual definition, exergy cancels out at the ambient temperature which is thus taken both as a constant and as a reference. When the fluctuations of the ambient temperature, obviously real, are considered, the temperature where exergy cancels out can be equated, either to the current ambient temperature (thus variable), or to a constant reference temperature. Thermodynamic consequences of both approaches are mathematically derived. Only the second approach insures that minimizing the exergy loss maximizes performance in terms of energy. Moreover, it extends the notion of reversibility to the presence of an ideal heat storage. When the heat storage is real (non-ideal), the total exergy loss includes a component specifically related to the heat exchanges with variable ambient air. The design of the heat storage can then be incorporated into an optimization procedure for the whole process. That second approach with a constant reference is exemplified in the case study of heat pumping for heating a building in wintertime. The results show that the so-obtained total exergy loss is the lost mechanical energy, a property that is not verified when exergy analysis is conducted following the first approach.

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“…Exergy analysis is employed to detect and to evaluate quantitatively the causes of the thermodynamic imperfection of the process under consideration. Exergy analysis has been applied to different types of air conditioning systems by various researchers [20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Değişken Soğutucu Akışkan Debili Bir Sistemin Performans ve Ekonomik Analizi

Hürdoğan¹

2017

Çukurova Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi

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This study deals with the exergetic modeling and performance/cost evaluation of a variable refrigerant flow (VRF) air conditioning system. An experimental setup was established to investigate the system performance under cooling conditions. System mainly consists of one outdoor unit and two indoor units. Outdoor unit equipped with two compressors (one variable speed and one constant speed), condenser, and four way valve is connected to two indoor units. Exergy, cost, energy and mass (EXCEM) analysis was applied to this system for the first time to the best of the authors` knowledge. The relations between thermodynamic losses and capital costs were also parametrically investigated. Experimental results show that the greatest irreversibility (exergy destruction) occurs in the condenser, followed by the evaporators. Exergy efficiency of the whole system on the exergetic product/fuel basis was calculated to be 85.84% at a reference state temperature of 25 o C. Exergy efficiency and exergy loss rate were in the range of 85.27-86.55% and 0.919-0.916 MW/USD, respectively, based upon the conditions and parameters considered in the present study. Keywords: Variable refrigerant flow, Energy analysis, Exergy analysis, Exergoeconomic Değişken Soğutucu Akışkan Debili Bir Sistemin Performans ve Ekonomik Analizi ÖzBu çalışma kapsamında, değişken soğutucu akışkan debili (VRF) bir klima sisteminin ekserjetik modellemesi ve performans değerlendirmesi ele alınmıştır. Soğutma koşulları için sistem performansını araştırılabilmek için bir deney düzeneği kurulmuştur. Sistem esas olarak bir dış üniteden ve iki iç üniteden oluşmaktadır. Ġki adet kompresör (bir değişken hız ve bir sabit hız), konderser ve dört yollu valf ile donatılmış dış ünite, iki içi üniteye bağlanmıştır. Bu çalışmada sisteme ekserji, maliyet, enerji ve kütle (EXCEM) analizi uygulanmış ve termodinamik kayıplar ile maliyetler arasındaki ilişkiler parametrik

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The influence of possible definitions of a reference environment to determine the exergy of air in buildings

Cited by 21 publications

References 10 publications

Exergy efficiency of a ventilation heat recovery exchanger at a variable reference temperature

Exergy efficiency of a ventilation heat recovery exchanger at a variable reference temperature

Exergy Analysis and Process Optimization with Variable Environment Temperature

Değişken Soğutucu Akışkan Debili Bir Sistemin Performans ve Ekonomik Analizi

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