Cenk Onan

CFD and Experimental Analysis of a Falling Film outside Smooth and Helically Grooved Tubes

Simultaneous heat and mass transfer are investigated in a falling film outside grooved and smooth tubes. A numerical analysis of the helically trapezoidal-grooved and reference smooth tube was performed in the computational fluid dynamics program “Ansys Fluent 14.” The three-dimensional model drawings in the x, y, and z coordinates are used, and the effects of the falling film outside the helically grooved tube on the surface temperature and surface heat transfer coefficient are determined. The average surface temperature, heat transfer coefficient, and Nu values are determined experimentally for a constant heat flux. An uncertainty analysis and Nu correlation for the grooved tube are also provided in this study. The Reynolds number varied between 50 and 350 for the falling film and between 1500 and 3500 for air. Using a computational fluid dynamics (CFD) analysis for the reference smooth tube, the experimental results are validated within 2–12% difference. The experimental results are also within 6–13% of the grooved tubes.

Determination of the Thermal Insulation for the Model Building Approach and the Global Effects in Turkey

One of the most important considerations to be considered in the design of energy efficient buildings is the thickness of the insulation to be applied to the building. In this study the existing building stock in Turkey has been investigated depending on parameters such as the height and the area. A model building has been created covering all of these buildings. Fuel emission reduction of combustion system was calculated in the case of insulation applied to this model building. Heat loss of the existing building stock and exhaust emissions and the contribution to the countrys economy with the model building methodology are also determined. The results show that the optimum insulation thicknesses vary between 3.21 and 7.12 cm, the energy savings vary between 9.23 US

Theoretical study of R32 to replace R410A in variable refrigerant flow systems

/m2 and43.95 US

The Effect of Insulation on Energy Savings and Costs for the Current Building Inventory in Turkey

/m2, and the payback periods vary between 1 and 8.8 years depending on the regions. As a result of the study when the optimum insulation thickness is applied in the model building, the total energy savings for the country are calculated to be 41.7 billion US

Heat Transfer Analysis of Internally Grooved Copper Tube R404-A Evaporators

. And also total CO2 emissions for the country are calculated to be 57.2 billion kg CO2 per year after insulation.

Daily Exergy Assessment of LiBr-Water Absorption Chiller Used for Solar Cooling

ABSTRACT In recent years, global warming has reached critical levels and this has caused a gradual decrease in the use of refrigerants. In the 1997 Kyoto Conference, it was announced that after 2011, use of refrigerants which have higher global warming potential (GWP) of 150 will be restricted. Hence, it was foreseen that R410A, with a GWP of 2088, which has been used in residential heating, ventilating and air conditioning systems, will be prohibited in the near future. This study investigates the thermodynamic performance using R32, which is a potential alternative because of its low GWP, and R410A in variable refrigerant flow (VRF) systems. As a result of theoretical analysis, it was observed that the coefficient of performance of R32 is 5% higher in heating mode and 6% higher in cooling mode than that of R410A. Considering all of this, it was confirmed that R32 can be used in VRF systems as a replacement for R410A in terms of performance.

A New Approach to Determine Optimum Insulation Thickness for All Buildings in Turkey Based on Heating Loads and Heat Gains

The current building inventory in Turkey includes a large number of uninsulated buildings. By insulating these buildings, the required heating energy is decreased, and significant energy savings are achieved. Within the country, the standard “Thermal Insulation Requirements for Buildings” was placed into effect in buildings in the year 2000 and divided the country into four climatic regions. The optimum insulation thickness in buildings changes as a function of the region, type of insulation material and fuel. In this study, the implemented insulation thickness according to the “Thermal Insulation Requirements for Buildings” standard is calculated for the four different regions of Turkey for expanded polystyrene insulation material. The current building inventory in Turkey was taken from the State Institute of Statistics (Prime Ministry, Republic of Turkey). Energy savings, costs and payback period are calculated by the P1-P2 method for the current building inventory, using XPS insulation in all buildings and natural gas as the fuel for the heating energy requirements. The results are shown in the figures for the four different climatic regions, and the effect of the current building inventory distribution around the country is determined.© 2012 ASME

Optimization of insulation thickness for different glazing areas in buildings for various climatic regions in Turkey

Internally grooved copper tubes are used extensively in HVAC applications, direct expansion batteries and air or water cooled heat exchangers. The advantage of internally grooved copper tubes in evaporator and condenser units is an increase in the refrigerant-side heat transfer coefficient. When an internally grooved tube heat exchanger and a smooth-tube heat exchanger with the same dimensions are compared, the overall heat transfer coefficient and convective heat transfer coefficient are found to increase in different ratios. In addition to this difference, the refrigerant side pressure is found to be a function of the groove geometry, pitch space and choice of refrigerant. In this study, which is different from previous studies in the literature performed using single internally grooved tube condensers and evaporators, refrigerant R404-A is studied in the internally grooved tube evaporator. The heat transfer in the evaporator described here is 30% better than that observed in a conventional smooth-copper-tube evaporator. In the internally grooved tube, the internal surface area is 68% larger than that inside the smooth reference tube. As a result, the convective heat transfer coefficient inside the internally grooved tube is found to be lower than that in the smooth tube.Copyright

Exergy analysis of a solar assisted absorption cooling system on an hourly basis in villa applications

In today’s society in which energy costs are high, the use of renewable energy sources has gained importance in cooling and heating systems. In recent years, solar cooling, which is a type of renewable energy source, is increasing rapidly in use in Europe. A solar assisted absorption cooling system was designed for acclimatizing villas in Mardin, Turkey, and the performance of the system under different temperatures was analyzed using Matlab. The cooling load of the villas was calculated assuming a cooling season of May 15 to September 15. The cooling capacity was calculated to be 106 kW. Changes in the coefficient of performance, the capacity of the hot water driven absorption cooling system and the exergy destruction values of the system according to our country’s meteorological data were calculated using Matlab. The amounts of inlet and outlet exergy were calculated separately for each component. Calculations were performed for two dead state temperatures: 25 °C and the environmental temperature, which is a more realistic approach. Therefore, the effect of varying the dead state temperature on the results was determined. It is observed that the greatest source of exergy destruction in the system was the solar collectors and the second greatest source of exergy destruction was the generator. The hourly distributions of exergy destruction values are given in a table. The effects of environmental temperature and solar insulation were stated for the optimization of energy and exergy in the combined system, which are planned to be established.Copyright

Exergy Assessments by Using Real-Time Measurements in a Factory

In Turkey, “Thermal Insulation Requirements for Buildings” was implemented to provide energy saving in buildings in 2000. After this, more then seven hundred thousand new buildings are constructed. Determining the correct material and optimum insulation thickness are very important issues in these buildings for thermal insulation. Calculations using monthly outdoor temperatures and solar radiation are done for XPS insulation material and 4 different climatic regions in Turkey. Natural gas, the most preferred in our country is selected as fuel. P1 -P2 method is used to obtain energy saving and payback period. New correlations are specified to determine optimum insulation thickness depending on building heat gains and areas. Furthermore, buildings are categorized into three building class according to external wall area and floor/roof area. Effect of change in building external wall area, floor or roof area, window area to payback period, energy saving and optimum thickness are investigated. As a result, effect of architectural design is determined on thermal insulation. All calculation results are shown in a table for four different climatic regions and three different types of buildings which have the same gross volume.Copyright