Browsing by Author "Ezan, Mehmet Akif"

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Citation - Scopus: 15
An integrated transient model in TRNSYS for thermal management of the tomato growth process in a greenhouse with a PV-aided heat pump-assisted HVAC system
(Elsevier B.V., 2024) Nezir Yağız Çam; Mehmet Akif Ezan; Yusuf Bicer; Ezan, Mehmet Akif; Çam, Nezir Yağız; Biçer, Yusuf
Greenhouses are the most common agricultural structures for controlled environment agriculture and it is not easy to control the indoor climate due to the complexity of the heat and mass transfer mechanisms. Therefore numerical models help to simulate the greenhouse indoor environment under various design alternatives obtain the heating and cooling rates and determine the appropriate control strategy. In this study a novel transient thermal model of a greenhouse is developed in MATLAB and implemented in TRNSYS software to simulate the thermal management procedure for the tomato growth process. A PV-aided HVAC system with a heat pump is integrated into the greenhouse to meet the heating/cooling load and maintain the temperature and relative humidity of the indoor ambient within the desired ranges. It is assumed that the greenhouse has three tomato growth seasons annually. The temperature and relative humidity of the indoor air and the heating and cooling rates of the HVAC system are determined and the temperature and relative humidity variations are compared against a greenhouse without an HVAC unit. The simulations are conducted with TRNSYS for four climatically different cities: Izmir Valencia Casablanca and Tunis. The results reveal that the electricity consumption of the heat pump-assisted HVAC system is highest in Izmir with 742230 kWh/year. Besides the highest photovoltaic electricity production is determined in Tunis with 417960 kWh/year. The highest reduction in carbon emissions is determined in Casablanca with 112541.4 kg CO2 eq./year. © 2024 Elsevier B.V. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 4
Development of an integrated underfloor heating system model in TRNSYS and performance assessments
(Elsevier Ltd, 2024) Okan Gök; Nezir Yağız Çam; Ersin Alptekin; Mehmet Akif Ezan; Aytunç Erek; Gok, Okan; Alptekin, Ersin; Ezan, Mehmet Akif; Erek, Aytunc; Cam, Nezir Yagiz
In this study a transient model for a solar underfloor heating system with a sensible heat thermal energy storage (SHTES) system to meet the heating demand of a residential building is developed in TRNSYS software. As a novelty in the current model rather than using the built-in modules in the software an in-house MATLAB routine is implemented in TRNSYS to simulate the spatial and temporal variations inside a 2D slab-type SHTES tank. Long-term dynamic simulations are conducted to discuss the influences of the design and working parameters on the (i) energetic and exergetic performances (ii) solar fraction and (iii) CO2 emissions associated with the alternative underfloor heating systems. Parametric analyses are performed for climatically different locations such as Izmir (Csa: Hot-summer Mediterranean climate) and Erzurum (Dfb: Warm-summer humid continental climate). Variations in charging loop mass flow rates have minimal impact on the overall system performance in Izmir and Erzurum compared to other design and working parameters. The highest energy efficiencies of the solar-aided underfloor heating system for Izmir and Erzurum are achieved for a comfort temperature of 20 °C with 32.9 % and 24.6 % respectively. Regarding exergy efficiency the highest was determined as 4.04 % with a 23.5 °C comfort temperature in Izmir and 3.89 % with a comfort temperature of 20 °C in Erzurum. As a final result of the environmental assessments integrating solar SHTES especially with a natural gas-based auxiliary heater significantly reduces CO2 emissions by 99.6 % and 50.0 % in Izmir and Erzurum respectively. © 2024 Elsevier B.V. All rights reserved.
Doğrusal Tip Manyetik Soğutma Sistemi Tasarımı ve Performansının Deneysel Olarak İncelenmesi
(2018) Mehmet Akif Ezan; Ahmet YILANCI; Emrah BIYIK; Orhan EKREN; Ekren, Orhan; Yılancı, Ahmet; Ezan, Mehmet Akif; Bıyık, Emrah
Bu çalışmada manyetokalorik etkinin ısıtma-soğutma amacıyla kullanımına yönelik deneysel bir çalışma sunulmuştur. Çalışma kapsamında tasarlanan ve oda sıcaklığı civarında çalışan manyetik soğutma sistemi performansı incelenmiş ve deneysel çalışma sonuçları verilmiştir. Deneysel manyetik soğutma sisteminde manyetokalorik malzeme olarak gadolinyum kullanılmıştır. Manyetokalorik malzemenin plaka ve toz şeklinde kullanıldığı yeni bir rejeneratör tasarlanarak doğrusal hareketli manyetik soğutma sisteminde çalıştırılmıştır. Sistemde ısı transfer akışkanı olarak %10 etanol-su karışımı kullanılmıştır. Tasarlanan sistem ile 0 76 Tesla manyetik alan altında teorik çalışmalarda5 °C deneysel çalışmalarda yaklaşık 2 °C sıcaklık düşüşü elde edilmiştir.
Citation - WoS: 1
Citation - Scopus: 2
Modeling of a Solar-Aided Heating and Cooling System with Thermal Energy Storage for a Sustainable Agricultural Greenhouse
(Pergamon-Elsevier Science Ltd, 2025) Ghiat, Ikhlas; Ezan, Mehmet Akif; Cam, Nezir Yagiz; Bicer, Yusuf
Greenhouses, a primary feature of sustainable agriculture, necessitate sophisticated climate management due to the intricacies of heat and mass transfer processes. Computational modeling tools are utilized to simulate the microclimate within greenhouses under different design scenarios, determine heating and cooling loads, and ascertain optimal control strategies. The current study develops a novel simulation model of a solar-assisted chiller and heat pump system with a thermal energy storage unit for heating, cooling, and ventilation of a climate-controlled agricultural greenhouse. A comprehensive study of the thermal impact of ventilation control and shade cloth, which are passive air conditioning methods used in greenhouses, is conducted using the inhouse code developed in MATLAB. The greenhouse air conditioning system's energy consumption is reduced from 160,447.9 to 80,540.3 kWh by implementing ventilation control and shade cloth. This also leads to a reduction in carbon emissions from 86,882.5 to 43,612.6 kg-CO2 by 49.8 %.
Citation - WoS: 19
Citation - Scopus: 20
Numerical analysis of a near-room-temperature magnetic cooling system, Analyse numérique d'un système de froid magnétique proche de la température ambiante
(Elsevier Ltd, 2017) Mehmet Akif Ezan; Orhan Ekren; Cagri A.S. Metin; Ahmet Yilanci; Emrah Biyik; Salih Murat Kara; Ekren, Orhan; Yilanci, Ahmet; Kara, Salih Murat; Ezan, Mehmet Akif; Biyik, Emrah; Metin, Cagri
In this study for a near-room-temperature magnetic cooling system a decoupled multi-physics numerical approach (Magnetism Fluid Flow and Heat Transfer) is developed using a commercial CFD solver ANSYS-FLUENT as a design tool. User defined functions are incorporated into the software in order to take into account the magnetocaloric effect. Magnetic flux density is assumed to be linear during the magnetization and demagnetization processes. Furthermore the minimum and maximum magnetic flux densities (Bmin and Bmax) are defined as 0.27 and 0.98 respectively. Two different sets of analyses are conducted by assuming an insulated cold heat exchanger (CHEX) and by defining an artificial cooling load in the CHEX. As a validation case experimental work from the literature is reproduced numerically and the results show that the current methodology is fairly accurate. Moreover parametric analyses are conducted to investigate the effect of the velocity of heat transfer fluid (HTF) and types of HTF on the performance of the magnetic cooling system. Also the performance metrics of the magnetic cooling system are investigated with regards to the temperature span of the magnetic cooling unit and the cooling load. It is concluded that reducing the cycle duration ensures reaching lower temperature values. Similarly reducing the velocity of the HTF allows reducing the outlet temperature of the HTF. In the current system the highest temperature spans are obtained numerically as around 6 K 5.2 K and 4.1 K for the cycle durations of 4.2 s 6.2 s and 8.2 s respectively. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 14
Citation - Scopus: 15
Thermal behavior of a solar-assisted latent heat thermal energy storage unit on the heating season under variable weather conditions
(ELSEVIER, 2022) Nezir Yagiz Cam; Ersin Alptekin; Levent Bilir; Mehmet Akif Ezan; Alptekin, Ersin; Bilir, Levent; Ezan, Mehmet Akif; Cam, Nezir Yagiz
Due to the fossil-fuel-related climatic problems which got worse in recent decades the worldwide share of renewable energy has significantly increased. Even though solar energy is one of the most accessible renewables it has an intermittent nature throughout the day. Different energy storage techniques are implemented to resolve the intermittency problem and make solar-aided energy accessible when it is needed. Energy use in buildings has a huge share of total energy demand and heating/cooling demands are responsible for most energy consumption in buildings. In this study the performance of a solar-assisted latent heat thermal energy storage (LHTES) unit integrated with a heat pump is investigated during the heating season under variable weather conditions. Phase change materials (PCMs) with different melting temperatures (T-m) and latent heat of fusions (h(sf)) are studied and parametric simulations are conducted to examine the proposed systems' economic advantage and payback duration. Variable weather conditions are defined in simulations and seven consecutive day analyses are conducted to ensure that results are not dependent on the initial conditions. Results revealed that the PCM with T-m= 35 degrees C and h(sf) = 240 kJ/kg has a better thermal performance than the other alternatives i.e. T-m = 31 degrees C and 40 degrees C. The integration of the solar-aided LHTES unit with the heat pump increases the COP of the heat pump and the increment varies from 35% to 80% for heating months in Izmir. Such an improvement in COP reduces the operating costs related to the electricity consumption of the heating device significantly and the simple payback period of the combined system is determined to be approximately 13 years in Izmir.