Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Conference Object Energy Losses From Outdoor Located Air Handling Unit and Connection Duct(Universita degli Studi di Padova, 2007) Erdoğmuş, Abdullah Berkan; Özerdem, Barış; Özerdem, Barış; Mobedi, Moghtada; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn the present study, energy losses due to heat transmission and air leakage from outdoor located air handling unit and connection duct are investigated based on EN 1886 and NEN-EN 1507 standard. The EN 1886 standard classifies air handling unit according to heat transmission and air leakage, while NEN-EN 1507 standard specify air leakages of rectangular ducts. In this study, air leakage and heat transmission fluxes for three cities in different regions of Turkey are determined and the economical value of energy losses for a building located in the city of Izmir and services 24 hours is calculated. The ambient air temperatures are taken from Turkish State Meteorological Service. The daily average values are considered for ambient temperature. The energy losses are determined for the variable and constant supply temperatures. Tables and charts are provided to show the variation of energy losses due to transmission and air leakage for the whole year. The total amounts of heat transmission and air leakage energy losses for different classes of air handling unit and connection duct are compared and discussed.Letter Citation - WoS: 2Citation - Scopus: 3A Comment on Change of Nusselt Number Sign in a Channel Flow Filled by a Fluid-Saturated Porous Medium With Constant Heat Flux Boundary Conditions(Springer Verlag, 2013) Uçar, Eren; Özerdem, Barış; Özerdem, Barış; Pop, Ioan; Mobedi, Moghtada; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aim of this Letter is to show that, the Nusselt number sign might be changed without changing of heat transfer direction at the wall of channels, even for flows without viscous dissipation. The sign of the Nusselt number is important for deciding on heat transfer direction at a solid wall. The change of the Nusselt number signmay be interpreted as the change of the direction of the heat transfer at a wall. There are studies, such as internal heat and fluid flow in a channel with viscous dissipation (Hung and Tso 2008, 2009; Mitrovic and Maletic 2007; Mobedi et al. 2010) or with an asymmetric heat flux boundary conditions (Cekmer et al. 2011) in which the sign of the wall Nusselt number changes. Nield and Kuznetsov (2008) studied in a very interesting paper the counter flow in a channel whose boundaries are asymmetrically heated and is consisted of two porous layers with different permeability values. These authors showed that even the sign of an overall Nusselt number defined based on the average wall temperatures and heat fluxes, and the mean permeability values of the two porous layers can also be changed and it can take negative values when a strong asymmetry heat flux is imposed to the boundaries. The change of Nusselt number sign at the walls are also observed in other studies of Kuznetsov (Kuznetsov and Nield 2010; Xiong and Kuznetsov 2000).Article Citation - WoS: 32Citation - Scopus: 38Fully Developed Forced Convection in a Parallel Plate Channel With a Centered Porous Layer(Springer Verlag, 2012) Çekmer, Özgür; Mobedi, Moghtada; Özerdem, Barış; Özerdem, Barış; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, fully developed heat and fluid flow in a parallel plate channel partially filled with porous layer is analyzed both analytically and numerically. The porous layer is located at the center of the channel and uniform heat flux is applied at the walls. The heat and fluid flow equations for clear fluid and porous regions are separately solved. Continues shear stress and heat flux conditions at the interface are used to determine the interface velocity and temperature. The velocity and temperature profiles in the channel for different values of Darcy number, thermal conductivity ratio, and porous layer thickness are plotted and discussed. The values of Nusselt number and friction factor of a fully clear fluid channel (Nu cl = 4. 12 and fRe cl = 24) are used to define heat transfer increment ratio (ε th = Nu p/Nu cl)and pressure drop increment ratio (ε p = f Re p/f Re cl) and observe the effects of an inserted porous layer on the increase of heat transfer and pressure drop. The heat transfer and pressure drop increment ratios are used to define an overall performance (ε = ε th/ε p) to evaluate overall benefits of an inserted porous layer in a parallel plate channel. The obtained results showed that for a partially porous filled channel, the value of ε is highly influenced from Darcy number, but it is not affected from thermal conductivity ratio (k r) when k r > 2. For a fully porous material filled channel, the value of ε is considerably affected from thermal conductivity ratio as the porous medium is in contact with the channel walls.Article Citation - WoS: 25Citation - Scopus: 25Economical Assessment of Different Hvac Systems for an Operating Room: Case Study for Different Turkish Climate Regions(Elsevier Ltd., 2011) Özyoğurtçu, Gamze; Mobedi, Moghtada; Mobedi, Moghtada; Özerdem, Barış; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, the annual energy consumptions of four different heating, ventilation and air conditioning (HVAC) systems serving to operation rooms (ORs) located at five different cities (Izmir, Antalya, Istanbul, Ankara and, Erzurum) in Turkey are analyzed. The study is performed for four different HVAC systems: (a) 100% fresh air system (System I), (b) 100% fresh air with half air volume rate at night period (System II), (c) 100% fresh air with half air volume rate at night period and heat recovery unit (System III), (d) 50% fresh air with half air volume rate at night period and with heat recovery and mixing units (System IV). Life cycle cost (LCC) for 20 years life span is calculated for the considered systems. It is found that System IV considerably reduces energy consumption and it is economically proper for the considered cities. The rate of energy consumption and LCC reductions are greater for the cities with extreme climate condition having relatively low specific humidity ratio. Using System IV instead of System I reduces OR energy consumption by 74% for the city of Erzurum which has a cold and dry climate.Article Citation - WoS: 19Citation - Scopus: 23Fully Developed Forced Convection Heat Transfer in a Porous Channel With Asymmetric Heat Flux Boundary Conditions(Springer Verlag, 2011) Çekmer, Özgür; Mobedi, Moghtada; Mobedi, Moghtada; Pop, Ioan; Özerdem, Barış; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAn analytical study is performed on steady, laminar, and fully developed forced convection heat transfer in a parallel plate channel with asymmetric uniform heat flux boundary conditions. The channel is filled with a saturated porous medium, and the lower and upper walls are subjected to different uniform heat fluxes. The dimensionless form of the Darcy-Brinkman momentum equation is solved to determine the dimensionless velocity profile, while the dimensionless energy equation is solved to obtain temperature profile for a hydrodynamically and thermally fully developed flow in the channel. Nusselt numbers for the lower and upper walls and an overall Nusselt number are defined. Analytical expressions for determination of the Nusselt numbers and critical heat flux ratio, at which singularities are observed for individual Nusselt numbers, are obtained. Based on the values of critical heat flux ratio and Darcy number, a diagram is provided to determine the direction of heat transfer between the lower or upper walls while the fluid is flowing in the channel.